Wave soldering

Wave soldering operation guide for pcb assembly

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What is wave soldering?

Wave soldering refers to the process of forming a solder wave of melted solder alloy, typically using an electric pump or an electromagnetic pump, to achieve the desired solder wave height. Alternatively, nitrogen gas can be injected into the solder pot to create the wave. During wave soldering, a printed circuit board (PCB) with pre-mounted components passes through the solder wave, forming a specific shape of solder fillet on the liquid solder surface. This process, in which the PCB with components is passed through the solder wave at a specific angle and with a certain immersion depth to achieve solder joint connections, is called wave soldering.

Historical Development of Wave Soldering

  1. Origin of Manual Wave Soldering Wave soldering, as an electronic soldering technology, originated in the early 1960s. At that time, manually operated wave soldering equipment was widely used. Due to its simple structure, complex operation, and low efficiency, the application of manual wave soldering equipment was somewhat limited.

  2. Automation Control of Wave Soldering Equipment In the early 1970s, wave soldering equipment began to transition towards automation control. With the continuous development of electronic technology, the equipment gradually achieved automation control, greatly improving production efficiency. During this period, various automatic control systems for wave soldering equipment, including PLCs and microcontrollers, began to appear.

  3. Digitization of Wave Soldering Equipment Since the 21st century, wave soldering equipment has been advancing towards digitization. The application of digital technology has enabled wave soldering equipment to achieve higher precision, more stable quality, increased production efficiency, and reduced production costs. In particular, the application of CAD technology in wave soldering equipment has resulted in more stable and consistent soldering effects.

The working principle of wave soldering

The fundamental principle of wave soldering is to utilize molten solder to form a wave on the soldering surface. The soldering material is heated and melted as it passes through the wave, then contacts the soldering surface to create a solder joint. The key to wave soldering lies in controlling the temperature and flowability of the solder to ensure joint quality.

  1. Formation of molten solder: Initially, molten solder is formed in the solder pot through pump pressure, creating a specific shape of solder wave on its surface.

  2. Transport of circuit board: The circuit board is conveyed through the wave soldering machine on a chain conveyor, passing through the preheating zone to ensure temperature control during soldering.

  3. Soldering process: As the circuit board passes through the solder wave at a certain angle, its pins pick up solder from the liquid solder, which solidifies during cooling to form solder joints. The solder wave wets the soldering area and extends to fill, facilitating the soldering process.

  4. Soldering quality: Wave soldering technology is suitable for soldering a variety of metals and non-metals, including aluminum, copper, steel, as well as plastics, ceramics, and other non-metallic materials. It is widely used in electronics, machinery, automotive manufacturing, and other fields, providing efficient, fast, and precise soldering to meet high-precision, high-reliability, and high-quality soldering requirements.

The Process of Wave Soldering

The wave soldering process involves the following steps:

  1. Preparation: Ensure the quality of the PCB and electronic components to be soldered, and perform necessary surface treatments such as cleaning and oxide removal.

  2. Application of solder paste: Apply solder paste to the appropriate soldering areas on the PCB, typically covering the contact surfaces of component pins and PCB pads.

  3. Component placement: Precisely mount electronic components onto the PCB at predetermined locations. This can be done using automated pick-and-place machines or manual methods.

  4. Wave soldering machine setup: Configure the wave soldering machine according to the soldering requirements and specifications, including soldering temperature, wave height, preheating zone, and soldering speed.

  5. Soldering process: Move the assembled PCB through the conveyor system to the solder wave area. The molten solder in the wave area makes contact with the PCB pads and component pins, forming solder joints.

  6. Cooling and solidification: Once the PCB exits the solder wave area, the solder joints are rapidly cooled and solidified through a cooling process, establishing stable solder connections.

  7. Inspection and quality control: Inspect and perform quality control checks on the soldered PCB, including visual inspection, X-ray testing, and solder joint reliability testing, to ensure that the soldering quality meets the requirements.

Operation Guide for Wave Soldering Equipment

  1. Preparing for Wave Soldering

(1) Turn on the main power switch according to the equipment’s operating schedule and control the solder pot switch time via the time electromagnetic valve.

(2) Check if the solder pot temperature indicator is functioning properly: Measure the temperature around 15mm below and above the solder pot’s liquid level with a thermometer, and ensure that the actual set temperature remains within a range of ±5°C.

(3) Check the operation of the lead cutter: Adjust the height of the cutter head based on the thickness of the PCBA, aiming for component pin lengths between 1.4 to 2.0mm.

(4) Verify the normal supply of flux: Pour flux into the fluxer, adjust the air inlet valve, and activate the fluxer to check for foaming or spraying of flux. Adjust the flux ratio to meet the requirements.

(5) Check the solder level height; if it is below 12-15mm from the solder pot, add solder promptly. Add solder in batches, not exceeding 10 kilograms each time.

(6) Clean the solder dross from the solder surface, and add anti-oxidant after cleaning.

(7) Adjust the angle of the transport rail: Adjust the total width of the rail according to the total width of the PCBAs to be soldered, ensuring moderate clamping force. Adjust the rail slope based on the pin density of the soldered components.

 

  1. Startup Process for Wave Soldering

(1) Turn on the flux switch, adjusting the foam adjusting plate thickness to half of “l” during foaming. For spraying, ensure the board is symmetrical, with moderate spray volume, preferably avoiding spraying on component surfaces.

(2) Adjust the air knife airflow to allow excess flux on the board to drip back into the foam groove, preventing drips on the preheater that could cause a fire.

(3) Turn on the transport switch and adjust the transport speed to the desired value.

(4) Turn on the cooling fans.

 

  1. Post-Wave Soldering Procedure

(1) Turn off the switches for the preheater, solder pot wave, fluxer, transport, cooling fans, and lead cutter.

(2) During operation, replace the flux in the foam groove every two weeks and measure it regularly.

(3) After shutdown, clean the wave soldering machine and claws thoroughly, soaking the nozzles in a cleaning solvent.

Wave soldering

Advantages and Disadvantages of Wave Soldering

Advantages:

High Efficiency: Wave soldering can simultaneously solder a large number of through-hole components, increasing production efficiency and output.

Welding Quality: Through strict control of welding parameters such as temperature, soldering time, and solder flux flow, wave soldering ensures stable welding quality.

Low Cost: Wave soldering can use standardized components and equipment, reducing production costs.

Disadvantages:

Component Limitations: Wave soldering can only solder through-hole components and cannot solder surface mount components.

Large Size Limitations: Wave soldering requires the PCB to be tilted on the soldering pallet, so there are certain limitations on the size and shape of the PCB.

Maintenance Difficulty: Wave soldering machines require regular maintenance and cleaning, which can be challenging.

Applications of Wave Soldering

Wave soldering technology has been widely applied in various electronic products, including consumer electronics, communication equipment, computers, and more. Here are the main application areas of wave soldering:

● Household Appliances: Wave soldering has become the primary welding technology in the manufacturing of household appliances, including TVs, DVDs, stereos, and more.

● Automotive Electronics: Wave soldering technology has been applied in automotive electronic products, including in-vehicle entertainment systems, safety control systems, etc., enhancing the reliability and safety of automotive electronic products.

● Communication Equipment: Wave soldering technology has been widely used in communication equipment such as base stations, routers, etc., enabling high-density and high-speed circuit designs.

● Industrial Control: Wave soldering technology has been applied in the field of industrial control, including PLCs, industrial computers, etc., improving the reliability and stability of equipment.

Future Development of Wave Soldering

With the trend of miniaturization and high-density electronic products, wave soldering technology is continuously innovating and developing. Here are the future development directions of wave soldering:

● Increased Automation: The automation level of wave soldering machines will continue to increase, including automation of component feeding and solder liquid supply.

● Improved Welding Quality: The welding quality of wave soldering machines will continue to improve, including more precise control of welding parameters such as temperature, welding time, solder flux flow, etc.

● Innovation in Welding Materials: With the growing environmental awareness, the welding materials used in wave soldering machines will continue to innovate and improve, including the adoption of lead-free solder and other environmentally friendly materials.

● Expansion of Application Areas: Wave soldering technology will be applied in more electronic products, including smart homes, the Internet of Things (IoT), etc.

In summary, as an important electronic component welding technology, wave soldering has been widely applied in various electronic products. With continuous technological innovation and development, it will play an increasingly important role in the future.