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2oz copper PCB introduction and application guide

05/08/2025 in /by

Printed circuit boards (PCBs) are a key component of electronic devices, both providing physical support for electronic components and enabling electrical connections. Among the many technical parameters of a PCB, the thickness or weight of the copper foil is particularly critical and is often expressed in ounces per square foot (oz/ft²). While 1oz copper foil is a common standard in traditional applications, 2oz copper PCBs are becoming increasingly popular as the performance needs of electronic devices increase.

In this article, we’ll take an in-depth look at what the actual thickness of 2oz copper foil means in a PCB, explain why it’s growing in popularity in today’s electronic designs, plus we’ll sort through the key benefits that 2oz copper brings to the table, the applications for 2oz copper pcb’s, and introduce some design guidelines to help maximize its performance.

What is 2oz copper thick pcb

A 2oz copper thick PCB is a printed circuit board (PCB) with a copper foil thickness of 2 ounces (OZ). Below is a detailed description of 2 ounce copper thick PCBs:
In the PCB industry, copper foil thickness is measured using ounces (OZ) as a unit, with 1 oz copper thickness indicating the thickness achieved by evenly distributing 1 oz (approximately 28.35 grams) weight of copper foil over a 1 square foot area.
A 1oz copper thickness equals approximately 35 microns (1.4 mils), so a 2oz copper thickness is approximately 70 microns (2.8 mils).

Basic Properties of 2oz Copper PCBs

High Conductivity: The increased thickness of the copper foil increases the ability of the line to carry a significant amount of current (formula: I ∝ h, h is the copper thickness) and reduces resistance losses.
Excellent heat dissipation: thick copper layer can quickly export heat, preventing components from overheating, extending the life of the equipment.
High mechanical strength: strong resistance to bending, pulling and impact, adapting to complex industrial environments.
Classification difference: the production process is different between regular thick copper boards (≤3OZ) and ultra-thick copper boards (3-12OZ), with the latter requiring high-precision copper foil selection, special press-fit technology and enhanced etching process.

Why choose 2oz copper PCB?

High Current Carrying Capacity
Equation derivation: Line loadable current I is directly proportional to copper thickness h (I ∝ h), and heat generation Q is inversely proportional to copper thickness h (Q ∝ 1/h).
Practical application: In high power scenarios such as power modules and motor drives, 2oz copper PCBs can reduce resistance loss and improve system efficiency.

Thermal Management Optimization
The thick copper layer acts as a “cooling channel” to quickly transfer heat to the heat sink or enclosure to avoid localized overheating.
Case in point: automotive engine control systems are exposed to high temperatures for long periods of time, and 2oz copper PCBs ensure circuit stability.

Mechanical Reliability
Shock resistance is improved by more than 30%, suitable for industrial equipment or automotive electronics with frequent vibration.

2oz copper PCB

2oz copper PCB

Core Application Areas

Automotive Electronics
Control modules, engine control systems, airbags and other critical components need to withstand high temperatures, corrosion and mechanical stress.

Power & Energy
Power modules, DC-DC converters, solar inverters, etc., need to handle high power conversion and distribution.

Industrial Automation
High-power motor drives and automation equipment control require circuit boards with high conductivity and durability.

Emerging Fields
High-end products such as 5G base stations, AI servers, etc., have stringent requirements for PCB layers, precision and heat dissipation performance.

Design Recommendations for 2oz Copper PCBs

In order to fully utilize the advantages of 2oz copper foil thickness in circuit board design, design engineers should consider the following layout and wiring guidelines:

Reasonable use of space: 2oz copper supports finer line widths and spacing, allowing for a more compact device layout. Components can be appropriately dispersed during design to fully utilize the extra space.

Shorten wiring paths: Because 2oz copper has lower resistivity, there is less reliance on wider alignments, and shorter, more direct connections can be prioritized.

Optimize layer structure: Lower current densities allow for fewer board layers when the layout permits. However, sufficient power and ground layers need to be maintained to ensure stability.

Reduced via size: Thanks to the high resolution capability of 2oz copper, smaller via designs can be used while maintaining good wiring density.

Increased component integration: Thinner copper wires make it easier to connect small package components, thereby increasing overall component density.

Controlling High Frequency Impedance: For high frequency applications, ensure that thin copper traces are routed as short as possible to avoid signal integrity issues caused by long or narrow traces.

Reduce thermal structure: If conditions permit, remove some heat sinks to reduce overall thermal resistance.

Increase copper-filled areas: Enhance heat dissipation efficiency and electromagnetic interference (EMI) shielding effect through reasonable copper surfacing, while maintaining a safe distance from signal lines.

Avoid excessive fragmentation of planar layers: Minimize fragmentation of the power and ground layers and improve continuity through multi-point over-hole connections.

Focus on edge spacing: Under high-precision etching processes, special attention needs to be paid to the alignment gap at the edge of the board to avoid processing defects.

Optimize design rules: Tighten the design grid and DRC (Design Rule Check) parameters to accommodate the manufacturing capacity of 2oz copper boards.

Pay attention to pad-via-hole matching: In high-density wiring, ensure that the design of pads and vias meets reliability requirements to avoid soldering problems.

Through rational layout and standardized wiring strategies, 2oz copper PCBs can not only effectively reduce board size, but also significantly improve electrical performance and help control manufacturing and assembly costs!

Summary

With its high conductivity, thermal performance and mechanical strength, 2oz copper PCBs have become the first choice for high-power, high-reliability electronic devices. With the rapid development of automotive electronics, new energy and AI fields, its market demand will continue to grow. The design and manufacturing process needs to focus on line compensation, process optimization and thermal design to ensure product performance and yield. In the future, intelligent production and the application of environmentally friendly materials will further promote the technological innovation and industrial upgrading of thick copper PCB.

What is the PCB assembly process?

05/05/2025 in /by

As we all know, printed circuit board (PCB) is an indispensable core component in modern electronic devices, while printed circuit board assembly (PCBA) is the process of mounting electronic components onto PCBs and making them circuit-connected through soldering and other processes. In this article, we will introduce the concepts related to PCBA and the processing flow of PCBA.

What is PCB assembly?

PCBA, or printed circuit board assembly, is an important part of electronic circuit design.
It is not just a simple printed circuit board (PCB), but electronic components (such as SMD components SMT and plug-in components DIP) are mounted on the PCB board and formed into a complete circuit system through welding and other processes.
PCBA is widely used in all kinds of electronic products, such as TVs, computers, cell phones, automotive electronics and medical equipment, etc. It is an indispensable core component for electrical connection and signal transmission in these devices.

Basic Components of Printed Circuit Board Assemblies

1. Base structure components

Substrate: Made of insulating material (e.g. FR-4 epoxy resin) that provides mechanical support and electrical isolation.
Lead layer and copper foil: copper foil etched to form a network of leads for the transmission of current and signals.
Solder pads and vias: Solder pads are used to solder component pins and vias connect different layers of the circuit.
Soldermask and silkscreen: The soldermask (green coating) protects the outer layer of the circuitry, and the silkscreen labels the component locations and identifies them.
Mounting holes and connectors: to fix the board or connect other devices.

2. Active Components

Integrated circuits (IC): core components, integrated complex logic functions, such as microprocessors, memory.
Transistor (Triode/Field Effect Tube): used for signal amplification, switching control.
Diode: unidirectional conductivity, used for rectification, voltage stabilization.
Sensors: detect environmental parameters (e.g. temperature, light) and convert them into electrical signals.
Actuator (relay, motor): according to the control signal to perform the action.

3. Passive components

Resistor: limit current, voltage and current divider.
Capacitor: store electrical energy, filtering, coupling.
Inductor: storage of magnetic energy, filtering, oscillation.
Transformer: voltage conversion, impedance matching.
Crystal oscillator: provide clock signals to ensure stable operation of the equipment.

4. Connection and protection components

Connector: connection between boards or equipment (such as rows of pins, sockets).
Fuses: overcurrent protection.
Varistor / transient suppression diode: anti-surge voltage.
Filter: Suppresses noise and improves signal quality.

The basic process of PCB assembly

PCBA production, i.e., PCB bare board through the component placement, plug-in, and complete the welding process. This process covers a number of procedures, including SMT placement processing, DIP insertion processing, PCBA testing, three-proof coating, and the final visual inspection and packaging shipment. Each step is critical and works together to ensure the quality and performance of the PCBA.

SMT SMD Processing

1. Board Drop
This link in the beginning of the SMT production line plays a crucial role, it ensures that the PCB boards can be transferred to the production line in an orderly and efficient manner, thus guaranteeing the continuity and efficiency of production.

2. Solder Paste Printing
Solder paste printing is a key part of SMT placement processing, which involves the precise printing of solder paste onto the circuit board by manual means through the stencil of the printing machine. This step not only requires professional printing machine (such as hand printing table) and squeegee, but also requires strict control of the composition of the solder paste, printing resolution, accuracy, and thickness and uniformity of the solder paste.

3. On-machine placement
On-machine placement is the SMD components in accordance with the process diagram or BOM requirements, through the SMD machine programming or manual alignment, accurate mounting to the circuit board has been printed with good solder paste.

4.Reflow soldering
In the solder paste printing and on the machine after the patch, in order to ensure that the components can be firmly soldered on the PCB board, reflow soldering must be carried out. This link through the high-temperature heating to melt the solder paste, so that the components and PCB pads closely together, so as to complete the welding.

5.AOI Inspection
Post-oven AOI is a key link in the production line. It is through the graphic recognition method will be stored in the AOI system standard digitized image and the actual detection of the image for comparison, so as to obtain the test results. The technical points of this link include inspection standard, detection force, false detection rate, sampling position, coverage rate and blind spot. Its inspection items cover a wide range of possible problems such as missing parts, reverse, upright, broken solder, wrong parts, less tin, warped legs, continuous tin and more tin.

DIP Insert Processing

DIP insertion, also known as DIP packaging or dual-row in-line packaging technology, is a process that packages integrated circuit chips in the form of dual-row in-line insertion.

1.Manual insertion
In this link, the PCB is passed through the rotation of the chain, and the workers need to insert the molded parts and components accurately and correctly to the corresponding position of the PCB according to the work instruction (applicable to through-hole components).

2. Wave soldering
Wave soldering is a kind of molten solder with the help of the pump, in the solder tank to form a specific shape of the solder wave process. During the soldering process, the PCB with components inserted passes through the conveyor chain and passes through the solder wave at a specific angle and immersion depth, thus realizing a solid connection of the solder joints.

3. Manual foot trimming
After the wave soldering is completed, the PCB board needs to be manually clipped. This step involves manual PCB board plug-in components on the surface of the pad exposed pins, in accordance with the provisions of the operating instructions for cutting. The purpose of cutting the foot operation is to ensure that the height of the component pins in the right place, while avoiding damage to the component body and its pad.

4. Manual soldering
In the manual welding process, the need for the PCB board soldering abnormalities, such as false soldering, leakage of solder, less tin, tin, etc., to repair in a timely manner. At the same time, for the components of the insertion of abnormalities, such as skewed, floating high, fewer pieces, wrong insertion, etc., also need to be dealt with accordingly to ensure the quality of welding.

DIP Insert Processing

DIP Insert Processing

Test link

1.ICT test

ICT test is designed to examine the basic characteristics of components to ensure good performance. During the testing process, NG (non-conforming) and OK (qualified) products are placed separately to facilitate subsequent processing. For the test results for the OK circuit board, the corresponding ICT test labels need to be affixed, and separated from the foam, in order to facilitate the subsequent tube.

2.FCT Test

FCT test is designed to comprehensively check the functional integrity of the circuit board. In the testing process, NG (defective) and OK (qualified) strictly differentiated, and are properly placed. For circuit boards with OK test results, they need to be labeled with the appropriate FCT test labels and isolated from the foam to facilitate subsequent tracking and management. At the same time, if you need to generate a test report, you should ensure that the serial number on the report corresponds to the serial number on the PCB board. For NG products, they need to be sent to the maintenance department for repair, and do a good job of recording the defective product maintenance report.

Coating of three-proof paint

Three-proof paint, as a kind of coating with special functions, is widely used in PCBA protection. Its role is to provide comprehensive protection for electronic components, effectively resist the erosion of moisture, salt spray and corrosive substances. By spraying three-proof paint, it not only ensures that the products work stably under the harsh environment of high humidity and high salt spray, but also significantly extends their service life.

Visual inspection for packing and shipping

Before packing and shipping, manual inspection must be carried out to ensure product quality, IPC610 standard is an important basis for inspection, focusing on checking whether the direction of the components on the PCBA is correct, such as IC, diodes, transistors, tantalum capacitors, aluminum capacitors and switches and so on. At the same time, it is also necessary to carefully check the defects after welding, such as short circuit, open circuit, fake parts, false welding, etc., to ensure that the products can work stably and meet customer requirements.

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What are the advantages of using flexible PCB?

04/28/2025 in /by

In the realm of printed circuit boards (PCBs), flexible PCBs stand out as a unique category, complementing their traditional rigid counterparts. In a wide range of applications, flexible PCBs demonstrate capabilities that rival — and sometimes surpass — those of rigid PCBs. To explore the charm and versatility of flexible PCBs, this article offers an in-depth analysis of their various types and real-world applications.

What Is a Flexible Circuit Board?

An FPC (Flexible Printed Circuit), often referred to as a “soft board,” is a member of the PCB family. Made with flexible substrates such as polyimide or polyester films, FPCs boast high wiring density, lightweight construction, thin profiles, and exceptional bendability and flexibility. These boards can endure millions of dynamic flexing cycles without damaging the circuitry, making them ideal for complex spatial layouts and three-dimensional assembly. By integrating component mounting and wiring into a single structure, FPCs achieve a level of performance that rigid PCBs often cannot match.

Basic Structure of an FPC

Copper Film (Copper Foil Substrate)

  • Copper Foil: A crucial material in FPCs, copper foil is available in two types — electrolytic copper and rolled annealed (RA) copper — with common thicknesses of 1oz, 1/2oz, and 1/3oz.

  • Substrate Film: Supports the copper foil and typically comes in thicknesses of 1 mil or 1/2 mil.

  • Adhesive: Used during manufacturing to bond layers, its thickness varies depending on customer requirements.

Coverlay (Protective Cover Film)

  • Cover Film: Primarily used for surface insulation, usually with thicknesses of 1 mil or 1/2 mil, applied together with adhesive layers.

  • Release Paper: Employed during manufacturing to prevent foreign matter from adhering to the adhesive before lamination, simplifying the production process.

Stiffener (PI Stiffener Film)

  • Stiffener: Enhances the mechanical strength of the FPC, facilitating surface-mount assembly. Typically, stiffeners range from 3 mil to 9 mil in thickness and are bonded with adhesives.

  • EMI Shielding Film: Protects the internal circuits from external electromagnetic interference, ensuring the stability and reliability of electronic devices.

Types of Flexible PCBs

Types of Flexible PCBs

Types of Flexible PCBs

As a major innovation within the PCB industry, flexible PCBs not only offer exceptional performance but also come in a wide variety of types. Their versatility greatly enriches the design possibilities for electronic products and meets the demands of increasingly complex applications. Below is an overview of the most common types of flexible PCBs and their typical uses:

  1. Single-Sided Flexible PCB
    Featuring a simple structure with a single conductive layer, these PCBs are cost-effective and ideal for basic applications.

  2. Double-Sided Flexible PCB
    With copper layers on both sides connected through metallized vias, double-sided flexible PCBs offer greater functionality for more complex scenarios.

  3. Multilayer Flexible PCB
    Built with multiple layers of copper and dielectric material stacked alternately, these PCBs achieve high elasticity while delivering superior performance.

  4. Rigid-Flex PCB
    Combining both rigid and flexible circuits into a single board, rigid-flex PCBs support high-density wiring and sophisticated layout designs.

  5. HDI Flexible PCB
    Featuring high-density interconnect (HDI) designs, these boards are lightweight, compact, highly integrated, and offer excellent electrical performance.

  6. Sculptured Flexible Circuit
    Designed with variable trace thicknesses to meet specific localized requirements, these circuits are ideal for intricate electronic applications.

  7. Polymer Thick Film Flexible PCB
    Manufactured using screen-printing techniques, these low-cost flexible circuits are best suited for low-voltage applications.

  8. Dual Access/Backside Flexible PCB
    A single-sided design that allows circuit access from both sides, simplifying the layout of complex circuitry.

  9. Single-Layer Flexible FPCB
    Comprising a base layer, adhesive, and a copper layer, this straightforward structure emphasizes protection of the conductive areas.

  10. Dual Access/Backside FPCB
    Similar in structure to a single-layer FPCB but with laser-drilled openings to access the copper layer, significantly enhancing design flexibility.

Features of Flexible PCBs

  1. Flexibility:
    Flexible PCBs can bend and fold without compromising circuit functionality, allowing for freedom of movement in three-dimensional spaces.

  2. Lightweight and Thin:
    Compared to rigid PCBs, flexible PCBs are significantly thinner and lighter.

  3. Miniaturized Design:
    Thanks to their ability to bend in 3D space, flexible PCBs enable the creation of more compact electronic products.

  4. High Reliability:
    Flexible PCBs offer greater resistance to vibration and shock compared to rigid boards, enhancing overall reliability.

  5. High-Temperature Resistance:
    These PCBs can operate reliably in high-temperature environments, demonstrating outstanding thermal stability.

In-Depth Analysis of Core Advantages of Flexible PCBs

In-Depth Analysis of Core Advantages of Flexible PCBs

In-Depth Analysis of Core Advantages of Flexible PCBs

Flexible PCBs (FPCs) have become increasingly indispensable in modern electronics due to their unique physical properties and design advantages. Below is a detailed exploration of their core strengths:

1. Exceptional Flexibility and Spatial Adaptability

  • Bendable and Foldable Design:
    Utilizing flexible substrates such as polyimide (PI) or polyester (PET), FPCs can bend, fold, or even roll within three-dimensional space, breaking the two-dimensional limitations of traditional rigid PCBs. For example, in foldable smartphones, FPCs are used in hinge areas, enduring hundreds of thousands of folds without failure.

  • Space Optimization:
    With thicknesses as low as 0.1 mm and weighing only 50%-70% of a rigid PCB, FPCs significantly enhance space utilization inside devices. In smartphones, FPCs seamlessly connect the mainboard to the display and camera modules, enabling “zero-gap” designs.

2. Lightweight Design and High Reliability

  • Weight Reduction and Cost Savings:
    The lightweight nature of FPCs makes them ideal for aerospace and wearable devices. For instance, satellite electronics systems utilizing FPCs see weight reductions of over 30%, while also minimizing the need for bulky connectors and reducing overall assembly costs.

  • Environmental Resistance:
    PI substrates withstand temperatures up to 250°C and exhibit excellent chemical and vibration resistance, making them suitable for harsh environments such as automotive engine compartments and industrial control systems.

3. Design Freedom and Integration Capabilities

  • 3D Routing:
    FPCs can route along curved surfaces, supporting innovative structural designs. In smartwatches, FPCs are integrated into the straps to flexibly connect sensors to the mainboard.

  • High-Density Integration:
    With technologies like laser drilling and fine-line patterning, FPCs can achieve line widths and spacings as small as 20μm/20μm, meeting the miniaturization demands of devices such as implantable medical equipment (e.g., neural stimulators) for multi-channel signal transmission.

4. Dynamic Adaptability and Durability

  • Extended Flexing Lifespan:
    Designs using serpentine routing patterns and rolled annealed (RA) copper allow FPCs to endure over 100,000 bending cycles, ideal for dynamic applications like flip phones.

  • Shock Absorption:
    Flexible substrates absorb mechanical stresses, reducing the risk of solder joint failures caused by vibrations. In automotive electronics, FPCs are used in airbag control modules to ensure signal stability even under extreme collision conditions.

5. Cost Efficiency and Manufacturing Productivity

  • Long-Term Cost Benefits:
    Although the unit cost of FPCs may be higher, their ability to reduce the need for connectors and simplify assembly processes lowers overall system costs in mass production. For example, integrated FPC modules in smartphones are 15%-20% more cost-effective than traditional cable harness solutions.

  • Rapid Production Support:
    FPCs can be produced with robotic automation, supporting small-batch, multi-variety manufacturing, ideal for the fast-paced iteration cycles of consumer electronics.

Typical Application Scenarios

  • Consumer Electronics:
    Display connections and camera modules in smartphones and tablets.

  • Medical Devices:
    Implantable pacemakers and miniature diagnostic device sensor circuits.

  • Automotive Electronics:
    Lightweight wiring for engine management systems and advanced driver-assistance systems (ADAS).

  • Aerospace:
    Radiation-resistant flexible circuits for satellite antennas and UAV control systems.

Conclusion

With the rapid rise of wearable devices, flexible displays, and smart technologies, the demand for flexible PCBs is experiencing explosive growth. In an era where electronic products increasingly prioritize lightweight, thin, compact, and highly efficient designs, ultra-thin and stretchable flexible circuits are poised to unlock immense market potential and drive the next wave of advancements in electronic devices and related technologies.

How to Remove Protective Coatings from PCBs

04/24/2025 in /by

Before production and processing, a protective conformal coating is typically applied to the surface of a PCB to safeguard it from environmental damage. This coating helps prevent water, dust, salt, and dirt from coming into contact with sensitive components, thus preserving the performance of the mainboard.

Removing conformal coatings can be challenging due to their durability and resistance to wear. If rework is needed, alcohol is not the ideal choice for removing these coatings. While alcohol is inexpensive and readily available, it lacks the solvent strength to effectively dissolve the coating and often requires extended soaking to have any effect. In this article, we will explore effective methods for removing protective coatings from PCBs.

Types of Conformal Coatings

There are five common types of conformal coatings available on the market:

  1. Acrylic Resin
    Acrylic resins dissolve easily in many organic solvents, making them convenient for board rework. They offer selective chemical resistance, dry quickly, resist mold, do not shrink during curing, and provide good moisture resistance. However, they have low abrasion resistance and are prone to scratching, cracking, and peeling.

  2. Epoxy Resin
    Typically composed of two parts that begin to cure upon mixing, epoxy resins offer excellent abrasion resistance, chemical resistance, and decent moisture protection. However, they are difficult to remove and rework. Because film shrinkage occurs during polymerization, a buffer solution is recommended around precision components. Curing at lower temperatures can help minimize shrinkage.

  3. Polyurethane
    Polyurethane coatings provide strong moisture and chemical resistance. Due to their robust chemical properties, removing them usually requires strippers, which may leave ionic residues behind. These residues must be thoroughly cleaned to avoid baseboard corrosion. Although rework through soldering is possible, it often results in brown discoloration that can affect the product’s appearance.

  4. Silicone
    Silicone is typically a single-component compound that begins to cure when exposed to moisture in the air and a certain temperature. Once cured, it forms a uniform, well-adhering layer across all surfaces of electronic components or modules. It is suitable for high-temperature environments (>120°C), as well as settings that require moisture sensitivity, chemical resistance, corrosion protection, and antifungal properties.

  5. Urethane (Polyurethane Carbamate)
    Urethane offers strong protection, hardness, and high solvent resistance. It provides excellent abrasion resistance and low moisture permeability. While it performs well in cold environments, it is not suitable for high-temperature applications. Most urethane coatings are difficult or impossible to rework or repair.

pcba

Common Types of Protective Coatings and Removal Methods

  1. Chemical Solvent Method

Applicable Types:

  • Polyurethane: Methanol/ethylene glycol ether with an alkaline activator, or toluene/xylene.

  • Acrylic: Methylene chloride, chloroform, ketones (e.g., acetone), γ-butyrolactone, or butyl acetate.

  • Silicone: Methylene chloride or specific hydrocarbon solvents.

  • Epoxy: Difficult to remove once cured; for small areas, methylene chloride with an acidic activator and a cotton swab may be used.

Procedure:
Apply the solvent to the coating surface. Once the coating swells, gently wipe with a cotton swab or soft cloth. Avoid letting the solvent spread to unintended areas.

  1. Physical Removal Methods

Heat Method:

  • Tools: Soldering iron or hot air gun.

  • Note: Carefully control the temperature (do not exceed component tolerance). Suitable for high-temperature resistant components. Work quickly to avoid damaging the laminate.

Micro-abrasion Method:

  • Tools: Specialized abrasive equipment (e.g., walnut shell or glass bead media).

  • Note: Mask surrounding areas to prevent electrostatic buildup. Should be performed by trained personnel.

Mechanical Scraping:

  • Tools: Razor blade or small knife.

  • Steps: Cut a V-groove at the solder point, apply solvent, then lift the coating. Best for localized rework.

  1. Specialized Cleaning Agents

Recommendation: Use eco-friendly cleaning agents (e.g., Kyzen ES125A).
Method: Ultrasonic cleaning or soaking. Suitable for large areas or complex PCBs.

  1. Localized Replacement Method

Use Case: When only specific components need replacement.
Steps: Use a soldering iron to heat and remove the coating on the component, replace the part, clean the area, and reapply conformal coating.

Summary

PCB protective coatings are surface-applied materials designed to protect circuit boards from moisture, dust, chemicals, and high temperatures, thus improving product reliability. Common types include:

  • Acrylic (easy to apply, requires specific solvents for removal),

  • Polyurethane (strong protection, difficult to remove, may emit toxic fumes when heated),

  • Silicone (heat-resistant and reworkable), and

  • Epoxy (very tough once cured, hard to remove).

Removal methods should be selected based on coating type and may include chemical solvents (e.g., methylene chloride, methanol), physical methods (heat, abrasion), special cleaning agents, or localized replacement. Always prioritize safety and environmental responsibility, and take care to avoid damaging the PCB or its components.

Comprehensive Guide to 8-Layer PCB Design and Prototyping

04/21/2025 in /by

In the field of electronics manufacturing, printed circuit boards (PCBs) play a critical role. With rapid advancements in technology, multilayer PCBs have become widely used across various electronic devices due to their superior electrical performance and optimized space utilization. This article provides a brief overview and explanation centered on the prototyping of 8-layer PCBs.

Basic Structure of an 8-Layer PCB

8-Layer PCBs

An 8-layer PCB consists of eight conductive layers (typically copper) interleaved with seven insulating layers (usually dielectric materials). This structure enables more complex circuit routing, enhances circuit integration, and improves overall performance. Each conductive layer can be routed as needed according to the design, while the insulating layers ensure electrical isolation between the layers.

8-Layer PCB Stack-Up

1. Signal Layer (TOP)

Signal Layer

Signal Layer

The first signal layer, also known as the top layer, is the visible surface of the physical PCB and is used for mounting electronic components. As shown in the diagram, this layer has a high density of traces. One reason is that components are placed on this same layer, allowing direct routing without the need for vias to switch layers. This avoids vias interfering with routing on other layers. In multilayer board design, via placement requires careful consideration.

2. Power Plane (VCC)

Power Plane
This layer shows no routing because it is dedicated to the power network. During design, specific traces are used to split different power domains. It is essential to place components with the same voltage requirement in the same region so they can be connected to the corresponding power zone through vias—eliminating the need for additional routing.

3. Signal Layer (Inner Layer 3)

Inner Layer 3

Inner Layer 3


This layer is primarily used for signal routing, though some power lines are also present. In the diagram, the thicker traces represent power lines, while the thinner ones are signal traces.

4. Signal Layer (Inner Layer 4)

Inner Layer 4
This layer is similar in function to the previous one, used for both signal and power routing.

5. Ground Plane (GND)

Ground Plane
This layer serves as the ground network, interconnected through vias.

6. Signal Layer (Inner Layer 5)

Inner Layer 5
Used for signal routing.

7. Ground Plane (GND)
This layer mirrors Layer 5 and also functions as part of the ground network.

8. Bottom Layer

Bottom Layer
The bottom layer, like the top layer, is commonly used for routing small components. Traces for many of the smaller chips are typically found on either the top or bottom layer.

Standard Thickness of 8-Layer PCBs

The standard thickness for 8-layer PCBs typically ranges from 1.6 mm (63 mils) to 2.4 mm (94 mils), depending on the copper foil thickness and the choice of prepreg/core materials. However, the final thickness may also be influenced by several key factors:

  • Copper thickness (e.g., 1 oz, 2 oz)

  • Dielectric spacing between layers

  • Type of materials used in the PCB stack-up

Standard Thickness of 8-Layer PCBs

Standard Thickness of 8-Layer PCBs

Thicker PCBs offer greater mechanical strength and are less prone to warping, making them ideal for industrial applications. Thinner PCBs, on the other hand, are more suitable for compact devices such as smartphones and portable electronics.

In practical design, the standard PCB thickness should be determined based on the circuit’s characteristics—such as whether impedance control is needed, if there are thermal management requirements, and the manufacturing capabilities of the PCB fabricator. An appropriate thickness ensures the PCB can be properly mounted inside the enclosure, aligned with connectors, and integrated smoothly into the final product assembly.

Key Design Considerations for 8-Layer PCBs

1. Impedance Control
High-speed signal traces (e.g., DDR4, HDMI) require differential impedance matching (typically 100Ω). This is achieved by fine-tuning trace width, spacing, and the distance to reference planes.
Use SI/PI simulation tools (Signal/Power Integrity) to optimize trace layout.

2. Power Distribution Network (PDN)
Dedicated power and ground planes reduce noise and ensure power integrity.
Decoupling capacitors (e.g., 0.1μF) are placed near power pins to suppress high-frequency interference.

3. Differential Pair Routing
Differential signal lines (e.g., USB 3.0) should be routed with equal length and closely spaced in parallel.
Avoid 90° angles—use 45° bends to reduce signal reflection and maintain integrity.

4. Interface Design

  • Ethernet: Magnetic transformers should be placed close to the PHY chip; differential pairs should have copper pour cleared underneath to minimize crosstalk.

  • HDMI: Common-mode chokes and ESD protection components should be placed near the connector; keep intra-pair skew ≤ 5 mils.

5. Thermal Management
For high-power components (e.g., CPUs), add thermal vias or conductive materials beneath the component to dissipate heat and prevent thermal-induced signal instability.

8-Layer PCB Prototyping Process

The prototyping process for an 8-layer PCB typically involves the following key steps:

  1. Design
    Use professional electronic design software to create the schematic diagram, and convert it into a PCB layout file.

  2. Review
    Conduct a thorough review of the design files to ensure the circuit layout is accurate and meets manufacturing requirements.

  3. Photoplotting
    Convert the verified PCB layout files into photoplot files, which are used in the exposure process.

  4. Inner Layer Circuit Fabrication
    Import the photoplot files into an exposure machine. Using exposure and development processes, create the inner layer circuitry.

  5. Lamination
    Alternate the inner layers with insulating layers, and bond them together under high temperature and pressure to form a multilayer structure.

  6. Drilling
    Drill holes in the laminated stack based on design specifications to allow for component mounting and inter-layer connections.

  7. Outer Layer Circuit Fabrication
    Create circuit patterns on the outer copper layers and perform necessary surface finishes (e.g., gold plating, HASL).

  8. Inspection
    Perform rigorous quality checks on the finished 8-layer PCB, including visual inspection and electrical testing, to ensure performance and reliability.

  9. Shipping
    Once the PCBs pass inspection, they are packaged and shipped to the customer.

8-Layer PCB Prototyping Process

8-Layer PCB Prototyping Process

Applications of 8-Layer PCBs

8-layer PCBs are widely adopted in various industries due to their excellent electrical performance and superior signal integrity. Common application areas include:

  1. Telecommunication Equipment
    In the communications sector—particularly in high-frequency, high-speed systems such as 5G base stations and optical communication devices—8-layer PCBs effectively reduce signal crosstalk and improve transmission quality and stability.

  2. Computers and Servers
    Modern computing environments, especially high-performance servers and data centers, require intricate circuit design and precise power management. The multilayer architecture of 8-layer PCBs meets diverse circuit demands and enhances data processing efficiency.

  3. Consumer Electronics
    Devices such as smartphones, tablets, and high-end home audio systems increasingly rely on 8-layer PCBs. As device functionality expands, so does component density. These boards allow for greater integration and stability within compact form factors.

  4. Medical Devices
    Complex equipment like ultrasound machines and CT scanners benefit from the optimized layout and signal accuracy provided by 8-layer PCBs. This ensures precise signal processing, which is critical for diagnostic reliability.

  5. Industrial Control Systems
    Automation systems and industrial robots demand high reliability and functional complexity. The robust power distribution and noise immunity of 8-layer PCBs make them suitable for harsh and demanding industrial environments.

8-layer PCBs, with their multilayer collaborative design, address key challenges such as high-speed signal integrity, power noise suppression, and thermal management. They are becoming core components in emerging fields like 5G communication and AI hardware. As material technologies evolve—such as ultra-thin dielectrics and laser drilling—the performance boundaries of 8-layer PCBs will continue to expand.

Introduction to automotive audio pcba modules

04/17/2025 in /by

Automotive Audio Control Module (ACM) is one of the core components of in-vehicle infotainment system (Infotainment System), which is responsible for the management, processing, and regulation of audio signal input, output, and function control in the vehicle. With the development of automotive electronics technology, the audio PCB module is constantly upgraded in terms of integration, performance and functionality, and has become a key indicator of the strengths and weaknesses of the car audio system.

Automotive audio pcba module functions

1. Audio signal processing

Input source management: integrates multiple audio inputs (e.g. AM/FM radio, Bluetooth, USB/AUX interface, in-car navigation voice, cell phone casting audio, etc.), supports signal switching and priority control.

Digital Signal Processing (DSP): including equalizer (EQ) adjustment, frequency crossover, noise reduction, surround sound (such as Dolby Atmos) effect enhancement.

Volume Dynamic Compensation: Automatically adjusts the volume according to the speed of the vehicle (e.g. Speed-Volume Compensation) to offset the interference of environmental noise.

2. User Interactive Controls

Functions are operated via physical buttons, touch screen or voice commands (e.g. “Turn up the volume”).

Linkage with the instrument panel or HUD (Heads Up Display) to display information on the current audio source, volume, etc.

3. Network communication

interacts with other vehicle modules (e.g. BCM body control module) via CAN/LIN bus, realizing functions such as mute door opening and closing, reverse radar tone mixing and so on.

Support OTA (over-the-air upgrade) to update the audio algorithm or function expansion.

Automotive audio control modules

Composition of Automotive Audio PCB Module

1. Signal Input and Processing Unit
Receives audio signals from radio, Bluetooth, USB, AUX and other input sources.
Includes ADC (analog-to-digital converter) and DAC (digital-to-analog converter) to convert analog signals to digital signals.
Integrated DSP (Digital Signal Processor) for sound effects adjustment (such as equalizer, reverb, sound field positioning) and noise suppression.

2. Power amplifier unit

amplifies the processed audio signal to a power level sufficient to drive the speakers.
Classification:
Class AB amplifier: balancing efficiency and sound quality, suitable for mid-range models.
Class D amplifier: high efficiency, low power consumption, widely used in modern car audio.
Class G/Class H amplifier: Dynamically adjusts the power supply voltage to improve the energy efficiency ratio.

3.Audio Output Unit

Connects speakers (tweeter, midrange, bass, subwoofer) and subwoofer.
Supports multi-channel output (e.g. 5.1-channel, 7.1-channel) to realize immersive sound.

4. Control and interface unit
provides user interaction interface (e.g. knob, touch screen, voice control).
Integrate CAN bus, LIN bus and other communication protocols to link with in-vehicle infotainment system (IVI).

Software Architecture

Bottom driver: control hardware resources (e.g. I2S audio bus, GPIO key detection).

Middleware: audio framework (e.g. AAOS Audio HAL for Android Automotive), Bluetooth protocol stack (A2DP/HFP).

Application layer:

sound algorithms (e.g. Bose’s Centerpoint virtual surround technology).

Voice recognition integration (e.g. Amazon Alexa, Baidu DuerOS).

Troubleshooting (supports UDS protocol, can read DTC fault codes).

Key Technologies for Automotive Audio PCB Modules

1. Highly integrated design
Adopting SoC (System-on-Chip) or SiP (System-in-Package), the processor, amplifier, DAC and other functions are integrated into a single chip, reducing PCB area and wiring complexity.

2. Low noise and anti-interference technology
Power supply decoupling design: use multi-layer PCB and low ESR capacitors to suppress power supply noise.
Shielding technology: metal casing, ground isolation, differential signal transmission, reduce electromagnetic interference (EMI).
Grounding optimization: star grounding or single-point grounding to avoid ground loop interference.

3. High-efficiency heat dissipation design
High-power amplifier generates a lot of heat, which needs to be dissipated by heat sink, heat pipe or liquid cooling system.
PCB layout optimization: dispersed arrangement of heat generating components to avoid local overheating.

4. High Reliability Design
meets AEC-Q100/Q200 and other automotive grade component standards.
High temperature, vibration and humidity resistant design to adapt to the harsh automotive environment.

Automotive audio pcba module application cases

High-end models: such as BMW 7 Series, Mercedes-Benz S-Class, with multi-channel DSP amplifier, supporting active noise reduction and personalized sound customization.
New energy vehicles: Tesla Model 3/Y and other models, integrated 14-speaker + subwoofer system, sound effect optimization through the central processor.
Aftermarket: Third-party manufacturers (e.g., JBL, Harman Kardon) provide modular audio solutions, adapting to different models.

Summary

Automotive audio control modules are evolving from single-function to highly integrated and intelligent, becoming the key to enhancing the driving experience. With the popularization of electric vehicles and the advancement of autonomous driving technology, the requirements for real-time, sound quality and multi-modal interaction will further increase. If you need automotive audio modules, please contact LSTpcb, we have PCBA modules designed specifically for automotive audio, with powerful functions to meet all automotive audio applications.

FPC circuit board: a complete analysis from materials to processes

04/03/2025 in /by

In the electronics manufacturing industry, flexible printed circuit boards (FPCs) play a vital role. With the rapid development of science and technology, higher requirements are placed on the processing technology of FPCs. In order to meet market demand and improve production efficiency, we need to continuously innovate and optimize FPC processing technology. In this article, we will make a comprehensive analysis of FPC from materials to processing technology to help everyone better understand flexible circuit boards.

FPC concept

FPC, the full name of Flexible Printed Circuit, is a flexible printed circuit board, or soft board for short. It uses photo-imaging pattern transfer and etching technology on a flexible substrate to construct a conductor circuit, realize the electrical interconnection of the inner and outer layers of double-sided and multi-layer circuit boards, and protect and insulate through PI and glue layers. FPC is known for its high wiring density, light weight and thin design, and is widely used in many electronic products such as mobile phones, laptops, PDAs, digital cameras and LCMs.

Main raw materials of FPC

The main raw materials of FPC include: substrate, cover film, reinforcement material and other auxiliary materials. These materials play a vital role in the manufacturing process of FPC and together constitute the basis of flexible printed circuit boards.

1. Substrate:

As the supporting core of FPC, it determines the basic performance of the product. There are many types of substrates, and the selection should be based on the specific application scenarios and needs.

1.1 Glue substrate

Glue substrate, mainly composed of copper foil, glue and PI materials, is divided into single-sided substrate and double-sided substrate. Single-sided substrate is covered with copper foil only on one side, while double-sided substrate is covered with copper foil on both sides.

1.2 Glue-free substrate

Glue-free substrate, that is, substrate without glue layer, has a simpler structure than ordinary glue substrate, and is composed of only two parts: copper foil and PI. The advantages of this substrate are its thinner characteristics, excellent dimensional stability, excellent heat resistance, bending resistance and excellent chemical resistance. For this reason, glue-free substrate has been widely accepted and applied in various fields today.

In terms of copper foil, the common thickness specifications on the market include 1OZ, 1/2OZ and 1/3OZ. Recently, thinner 1/4OZ copper foil has been introduced. Although such materials have been used in China, their advantages are more obvious when making products with ultra-fine lines (line width and line spacing of 0.05MM and below). With the increasing demand of customers, this specification of copper foil is expected to be more widely used in the future.

2. Covering film

The covering film is mainly composed of release paper, glue layer and PI. During the production process, the release paper plays a role in protecting the glue layer to prevent it from being contaminated with foreign matter. But in the end, the release paper will be torn off, and the glue layer and PI together constitute an important part of the product.

3. Reinforcement material

Reinforcement material is specially designed for FPC to enhance the support strength of specific parts of the product, thereby improving the overly “soft” characteristics of FPC. There are many types of common reinforcement materials on the market.
1) FR4 reinforcement: It is mainly made of glass fiber cloth and epoxy resin glue, which is exactly the same as the FR4 material used in PCB.

2) Steel sheet reinforcement: This reinforcement material is mainly composed of steel, which is not only outstanding in hardness, but also has strong supporting strength.

3) PI reinforcement: It is similar to the cover film, consisting of PI and adhesive release paper, but the special thing is that its PI layer thickness can be customized from 2MIL to 9MIL.
Pure glue: This thermosetting acrylic adhesive film consists of protective paper/release film and a layer of glue. It is mainly used to bond layered boards, soft-hard boards, and FR-4 and steel sheet reinforcement boards.
Electromagnetic protective film: It is designed to be attached to the board surface to play a shielding role.
Pure copper foil: This material is composed only of copper foil and is a key material in the production process of hollow boards.

Unique advantages of flexible circuit boards

Flexible printed circuit boards, with their flexible insulating substrate as their feature, create many superior properties that rigid printed circuit boards do not have:

1. Flexibility: Flexible circuit boards can bend, roll and fold freely, fully adapting to the needs of spatial layout, while achieving easy movement and stretching in three-dimensional space, thus efficiently integrating component assembly with wire connection.

2. Size and weight advantages: With the help of flexible circuit boards, the volume and weight of electronic products can be significantly reduced, perfectly matching the trend of electronic products towards high density, miniaturization and high reliability. For this reason, flexible circuit boards have been widely used in aerospace, military, mobile communications, laptops, computer peripherals, PDAs, digital cameras and other fields or products.

3. Excellent characteristics: Flexible circuit boards not only have good heat dissipation and solderability, but also are easy to install and connect, and the overall cost is relatively low. Its soft and hard combination design makes up for the slight lack of flexible substrate in component carrying capacity to a certain extent.

Types of FPC

There are many types of flexible circuit boards, including single-sided flexible, double-sided flexible and multi-layer flexible. Among them, the cover layer of the single-sided flexible PCB is bonded to the single-sided FPC core without adhesive, while the double-sided flexible PCB is a double-sided FPC core without adhesive with cover layers bonded on both sides and plated through holes. Multi-layer flexible PCB contains three or more conductive layers with plated through holes, and its manufacturing capacity can reach more than 12 layers. In addition, there are special types of flexible circuit boards such as hollow boards, layered boards, and soft-rigid boards.

Detailed explanation of FPC production process

Single-sided board process flow:
Cutting: First, cut out the board of suitable size according to the design requirements.
Baking: Preheat the board to increase its machinability.
Dry film: Paste a layer of dry film on the board as a protective layer for subsequent processes.
Exposure: Transfer the circuit pattern to the dry film through the exposure machine.
Development: Wash off the unexposed dry film with chemical solution to expose the circuit pattern.
Etching: Etch off the part not covered by the dry film with etching liquid to form a circuit.
Demolding: Peel off the dry film from the board.
Pretreatment: Clean and activate the board to enhance surface adhesion.
Coating film: Paste a layer of covering film on the board to protect the circuit.
Lamination: Lay the covering film and the board together to form a circuit layer.
Curing: Cure the lamination layer by heating and pressurizing.
Surface treatment: Surface treatment of the circuit to enhance its corrosion resistance and conductivity.
Electrical measurement: Detect the connectivity and performance of the circuit through electrical measurement equipment.
Assembly: Assemble the circuit board with other components.
Pressing: Press the circuit board again to ensure that the connection between the components is firm.
Curing: Heat and pressurize again to cure the assembly layer.
Text: Print logos and instructions on the circuit board.
Shape: Cut the shape of the circuit board according to the design requirements.
Final inspection: Perform a final inspection on the circuit board to ensure that its quality and performance meet the requirements.
Packaging and shipment: Qualified circuit boards are packaged and then shipped.

Summary

Flexible PCB manufacturing requires full-link coordination from material selection, process parameters to testing standards. In the future, as AIoT devices develop towards high frequency and miniaturization, flexible PCBs will evolve towards ultra-thick copper layers (>3oz), embedded components, self-healing materials, etc., becoming the core technology supporting the innovation of smart hardware.

14 Methods of PCBA Testing

03/27/2025 in /by

PCBA (Printed Circuit Board Assembly) testing is a critical step in the electronics manufacturing process. It ensures that circuit boards and their mounted electronic components function correctly according to design specifications, achieving the expected performance and reliability. PCBA testing encompasses various aspects, including functional testing, performance evaluation, reliability assessment, and environmental adaptability testing.

As an indispensable part of PCB manufacturing, PCBA testing helps detect issues in a timely manner, enabling engineers to address problems quickly and ensuring high product quality. In this article, we will explore 14 PCBA testing methods in detail, helping you understand their applications and select the most appropriate approach for your needs.

14 commonly used PCB testing methods.

Functional Testing

1. In-Circuit Testing (ICT)

In-Circuit Testing

In-Circuit Testing

ICT, or Automated In-Circuit Testing, is an essential and powerful tool for modern PCB manufacturers. It uses test probes to contact designated test points on the PCB layout, detecting open circuits, short circuits, and component failures while providing clear diagnostic feedback.
ICT offers broad applicability, high measurement accuracy, and precise fault indication, making it easy for even less-experienced workers to handle defective PCBs. It significantly improves production efficiency and reduces manufacturing costs.

2. Flying Probe Testing

Both Flying Probe Testing and ICT are highly effective in identifying manufacturing defects, but flying probe testing is a particularly cost-effective method for enhancing PCB quality. Unlike traditional ICT, which relies on fixed test probes, flying probe testing uses two or more independently controlled probes that move dynamically based on software instructions.
Since flying probe testing does not require fixed test points, it has a lower initial cost and can be modified via software rather than hardware adjustments. This makes it ideal for small-batch production. However, ICT is faster and less prone to errors, making it more economical for high-volume production.

3. Functional Testing

Functional Testing


Functional System Testing employs specialized test equipment at various stages of production to verify circuit board functionality. It primarily includes Final Product Testing and Hot Mock-Up Testing.
Unlike ICT, functional testing does not provide in-depth data (such as pin positions or component-level diagnostics) for process improvement. Instead, it requires dedicated testing equipment and custom-designed test programs, making it complex and less suited for most production lines.

4. Automated Optical Inspection (AOI)

Automated Optical Inspection

AOI utilizes either a single 2D camera or dual 3D cameras to capture PCB images and compare them to a detailed schematic. If discrepancies are detected, the system flags them for manual inspection.
Since AOI does not power up the PCB, it cannot detect all potential defects, making it most effective when combined with other testing methods, such as:

  • AOI + Flying Probe Testing

  • AOI + ICT

  • AOI + Functional Testing

5. X-Ray Inspection

X-Ray Inspection

X-Ray Testing uses low-energy X-rays to quickly identify open circuits, short circuits, solder voids, and other defects.
It is particularly useful for inspecting ultra-fine-pitch and high-density PCBs, detecting assembly issues like bridging, missing chips, and misalignment. Additionally, X-ray inspection can utilize tomography to identify internal defects within IC chips. It remains the only reliable method for evaluating BGA solder quality and embedded components, offering the advantage of fixture-free testing.

6. Laser Inspection

This is one of the latest advancements in PCB testing technology. It involves scanning the PCB with a laser beam to collect measurement data, which is then compared to preset acceptance thresholds.
Laser inspection has been successfully validated for bare board testing and is being explored for assembled PCB testing. It provides fast output, requires no fixtures, and offers clear visual access. However, its main drawbacks include high initial costs and maintenance challenges.

7. Aging Test

Aging Test

Aging testing simulates real-world conditions to accelerate product wear and evaluate its long-term stability and reliability. The product is exposed to controlled temperature and humidity conditions while operating continuously for 72 hours to 7 days. Performance data is recorded and analyzed to refine the production process, ensuring the product meets market demands. Aging tests primarily focus on electrical performance but can also include drop tests, vibration tests, and salt spray tests.

8. Solderability Testing

Solderability testing ensures robust surface adhesion and enhances the likelihood of forming reliable solder joints. This test, based on the wetting balance method, evaluates the solderability of components, PCB pads, solder materials, and fluxes both qualitatively and quantitatively.

9. PCB Contamination Testing

PCB contamination testing detects ionic residues from flux, cleaning agents, humidity, plating, wave soldering, and reflow soldering. These contaminants can lead to corrosion and other reliability issues. Identifying and eliminating them is crucial for maintaining PCB integrity.

10. Cross-Section Analysis

Cross-Section Analysis

Cross-section analysis examines defects, open circuits, short circuits, and other failures by slicing the PCB for microscopic inspection. It provides insights into structural and material integrity.

11. Time-Domain Reflectometry (TDR) Testing

TDR testing

TDR testing is recommended for diagnosing faults in high-speed or high-frequency PCBs. It quickly identifies open and short circuits while pinpointing the exact failure location, making it a crucial tool for signal integrity analysis.

12. Peel Test

Peel Test

The peel test evaluates the adhesion strength between copper foil and the PCB substrate or brown oxide layer. It assesses bonding integrity under various conditions, including normal states, thermal stress, and high temperatures, ensuring mechanical reliability.

13. Solder Float Test

This test determines a PCB’s resistance to thermal stress, particularly for plated-through holes, surface conductors, and pads. The sample is immersed in molten solder for up to 5 minutes, with a depth not exceeding 50% of its thickness. After removal, it remains level until the solder solidifies, ensuring structural resilience.

14. Wave Soldering Test

Wave soldering testing evaluates the PCB’s ability to withstand the soldering process. Parameters such as fixture type, conveyor speed, preheating conditions, oxidation prevention, process control, board inclination, and soldering temperature are carefully recorded and analyzed to ensure optimal soldering quality.

Conclusion

These testing methods provide a comprehensive evaluation of PCBA performance. Manufacturers can select the most suitable tests based on the product’s specific applications and environmental requirements. By implementing rigorous testing, the risk of field failures is significantly reduced, enhancing product reliability and market competitiveness.

PCB coil manufacturing and use guide

03/25/2025 in /by

Coil PCB refers to an inductor-like component created by directly routing traces into a coil shape on a PCB. This technology offers excellent voltage resistance, high Q factor, strong consistency, flexible routing, and high current-carrying capacity, making it widely used in antenna applications. A PCB coil is a coil directly fabricated on a printed circuit board using conductor traces on the circuit board layers.

In this article, we will provide a detailed introduction to PCB coils, covering their concept, advantages, applications, manufacturing processes, and other key characteristics to help users gain a comprehensive understanding of PCB coils.

What is a PCB Coil?

A PCB coil is a device that uses precisely designed metal traces on a printed circuit board to form a coil of a selected shape. Interestingly, this process can be implemented across multiple layers, depending on different shapes and models.
Additionally, PCBs consist of alternating insulating layers and conductors that interweave to form grouped PCB coils.
Moreover, this component includes a conductor layer with tracks, allowing it to fit an appropriate arc shape while being divided into multiple conductive sections.

Basic Structure of PCB Coils

PCB coils mainly consist of the following components:

  • Coil Conductor: Typically made of copper foil, formed into spiral or other special shapes through PCB routing processes.

  • Insulation Layer: Commonly made of FR4, polyimide (PI), or ceramic substrates to ensure proper insulation performance.

  • Vias: Used to connect coil traces in multilayer PCBs, enhancing current-carrying capacity or increasing inductance.

  • Surface Treatment: Includes ENIG (electroless nickel immersion gold), OSP (organic solderability preservative), leaded/unleaded solder plating, etc., to improve soldering reliability and conductivity.

Types of PCB Coils

(1) Classification by Layer Count

  • Single-Layer PCB Coil: The coil structure is laid out only on one side of the PCB, featuring a simple design suitable for low-power applications.

  • Multilayer PCB Coil: Uses multiple PCB layers stacked and connected via vias to enhance inductance and current-carrying capacity.

  • Flexible PCB Coil (FPC Coil): Made from flexible materials like PI, suitable for bendable and ultra-thin applications, such as wireless charging coils.

(2) Classification by Shape

  • Spiral Coil: The most common structure, with the coil spirally distributed along the PCB surface. Widely used in wireless charging and RFID antennas.

  • Serpentine Coil: Designed for sensor and high-frequency applications, reducing parasitic capacitance.

  • Rectangular/Ring Coil: Used in specialized structural designs, such as electromagnetic shielding and transformer applications.

PCB coil

How Does a PCB Coil Work?

The electromagnetic principles of PCB coils are identical to those of wire-wound coils or any other inductors:

  • Conductive Element: Copper traces act as conductive components, replacing the wire windings in discrete inductors.

  • Induced Magnetic Field: When an alternating or pulsed current flows through the traces, it generates an expanding and contracting magnetic field.

  • Energy Storage: Due to the coil’s inductance, the magnetic field temporarily stores energy in each cycle of the AC current.

  • Induced Voltage: Any change in the applied current induces a voltage across the coil proportional to the rate of change, due to inductance.

  • Impedance: The coil presents an impedance that varies with frequency, primarily due to inductive reactance.

Thus, a PCB coil essentially functions as a standard inductor, with its parameters determined by its structure and materials.

Key Design Considerations for PCB Coils

(1) Coil Parameter Calculations

The design of a PCB coil primarily involves the following key parameters:

  • Inductance (L): Depends on the number of turns, trace width, spacing, and substrate material.

  • Resistance (R): Determined by copper foil thickness, trace width, and length, directly affecting energy losses.

  • Q Factor (Quality Factor): A higher Q factor indicates lower losses, making it suitable for high-efficiency applications.

  • Resonant Frequency (f₀): The resonant point must be considered to avoid signal interference or losses.

(2) Coil Layout Considerations

  • Trace Width and Spacing: Should be selected based on current levels and frequency to prevent overheating or electromagnetic interference (EMI).

  • Interlayer Connections (Via Design): Via diameter and copper filling should be optimized to reduce impedance and enhance reliability.

  • Shielding and Ground Planes: For high-frequency applications, ground planes or shielding layers can be used to minimize external interference.

PCB coil-1

PCB Coil Manufacturing Process and Precision Control

The manufacturing of PCB coils involves photolithography, etching, and electroplating processes. The typical workflow is as follows:

Photolithography Process

  • Steps: Photoresist coating → UV exposure (using film or LDI direct imaging) → Development → Etching → Resist stripping.

  • Precision: LDI (Laser Direct Imaging) technology enables line width/spacing ≤ 25μm, meeting the requirements of high-frequency coils.

Copper Layer Thickening Technology

  • Electroplated Copper: Electrolytic deposition increases the copper layer from 1oz to 10oz, significantly reducing resistance. (For example, in a 1mm wide, 10mm long coil, 1oz copper has ~5mΩ resistance, while 10oz copper reduces it to ~0.5mΩ.)

  • Applications: High-power inductors or transformers require a balance between cost and heat dissipation.

Multilayer PCB Process

  • Lamination & Vias: Multilayer copper foils are laminated using prepreg sheets, with vias formed via laser or mechanical drilling to establish electrical connections between layers.

  • Advantages: Planar transformers (e.g., a 4-layer board with primary and secondary coils vertically coupled) enhance magnetic coupling efficiency.

Laser Cutting Technology

  • Suitable for: Flexible PCB coils, high-frequency meander lines, eliminating the need for etching by directly cutting the copper layer.

  • Precision: CO₂ or UV lasers achieve ±10μm cutting accuracy.

Applications of PCB Coils

(1) Wireless Charging

  • Used in Qi wireless charging transmitters (TX) and receivers (RX).

  • Multilayer spiral coil designs improve energy transfer efficiency.

(2) RF and NFC Communication

  • Used in RFID, NFC applications such as smart cards and electronic payment devices.

  • Coil resonance frequency optimization ensures compatibility with target frequency bands (e.g., 13.56MHz).

(3) Sensors and Measurement

  • Applied in magnetic induction sensors and current sensors.

  • Differential PCB coil designs enhance signal sensitivity.

(4) Power and Electromagnetic Shielding

  • Used in PCB transformers and EMI suppression.

  • Coil turns and shape adjustments optimize electromagnetic compatibility (EMC).

Conclusion

As an essential magnetic component in modern electronic systems, PCB coil design requires careful consideration of materials, manufacturing processes, electromagnetic performance, and thermal management. With increasing demands for high-frequency, integrated, and flexible designs, PCB coil technology will continue to evolve for higher performance and broader applications. Through optimized design and process innovation, PCB coils will play a crucial role in emerging fields such as 5G communication, IoT, and electric vehicles.