Military PCB design and manufacturing

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Military PCB is a printed circuit board for military products. Because of its high requirements in terms of environment, stability and reliability, its design is relatively complicated and the design requirements are more stricter. How to ensure the quality of military PCB is a very critical issue. In this article, we will introduce the processes and requirements of military PCB manufacturing in detail.

The importance of military circuit board

Military circuit board is part of the core component of military electronic equipment. It is responsible for connecting and supporting various electronic components to realize the function of the circuit. In many military applications, such as communication, navigation, control, detection, etc., they need to rely on military circuit boards to ensure the stability of the equipment’s normal operation and signal transmission. Without a stable and reliable circuit board, these equipment will not be able to work effectively, which will affect the performance and security of the entire military system.

Military circuit boards have high reliability and durability. In military applications, equipment often needs to face harsh working environment, such as high temperature, low temperature, high humidity, strong vibration, etc. Military circuit boards are specially designed and manufactured, and can operate stably under these extreme conditions to ensure that the equipment can work for a long time and fail to fail. This is essential for ensuring the smooth completion of military tasks.

Military PCB design requirements

Components Selection:

Select high-quality printed circuit board materials that are best suited for military and defense applications. Use materials that meet the required standards for thermal management, chemical resistance, and PCB mechanical strength.

Abiding by Standards:

Military, aerospace, and law enforcement systems often hold specific standards and certifications that must be adhered to. For example, mention the standards and certifications of MIL-PFR-31032 (PCB HDI) and IPC-A-610 (acceptability of electronics assembled). Check and make sure that the PCB manufacturing process is according to these standards.

Durability and Functionality:

Military systems and their environment can be rigorous, facing extreme temperatures, increased humidity, and vibration. PCB must be designed very efficiently to adhere the required condition to ensure better functionality.

Confidentiality and Security Factor:

Military and security defense applications usually hold sensitive and confidential information. So, the security and keeping secret the design and manufacturing process of military PCB is very crucial to preventing unauthorized and unknown individuals from obtaining it.

PCB Traceability, Testing and Evaluation:

Design a strong traceability system for all materials to be used in military PCB manufacturing and assembly. It is essential to identify any malfunctions, errors, or defects throughout the military application lifecycle.

Apply a thorough testing and evaluation process to in the design and manufacturing of all components from beginning to the final military application.

Testing methods include visual testing, X-ray inspections, automated optical inspections (AOI), etc. which can help identify any malfunctions and defects produced in the early military PCB manufacturing process. Regarding the microscope magnification requirements for military PCB board inspection, it is generally required to use a microscope of more than 40 times for inspection.

The implementation of all these design and manufacturing considerations for military PCB is very important, as the military and law enforcement sectors need strict obedience to standards and regulations. Which enhances the required specifications for PCB manufacturing, such as working precision, functionality, and security throughout the PCB assembly and manufacturing process. Extreme

Thermal Management:

Military PCBs are subjected to extreme temperature conditions, so this factor should be critically considered in designing military systems and applications.

Electromagnetic Interference(EMI):

Military and defense sector environments often consist of electrical noise, which can interrupt sensitive electronics applications. Military PCBs should be properly shielded and designed to avoid any EMI issues.

PCB Corrosion:

Moisture exposure of PCB and severe chemicals can affect a printed circuit board with corrosion. Hence, military printed circuit boards must be covered with specialized components to resist and avoid corrosion.

Military PCB material

For military PCB, the reliability and stability of the material are very important. In extreme environments, under bad conditions such as high temperature, low temperature, and humidity, PCB needs to maintain good performance and working status. The commonly used materials are as follows:

1.FR-4

FR-4 is a glass fiber widely used in PCB to enhance epoxy resin materials, which has high mechanical strength and excellent insulation performance. It is widely used in the field of military industry, mainly because of its high stability and relatively low price, and is suitable for most military equipment.

2.PTFE

PTFE has excellent high temperature resistance and chemical stability. PTFE’s applications in military PCB are widely used, especially in some areas that have strict requirements on high -frequency performance, such as radar, communication and other systems, PTFE’s PCB can provide better signal transmission performance.

3. Metal substrate

The metal substrate has good heat dissipation performance and mechanical strength, which can effectively reduce the working temperature of electronic components and improve the reliability and stability of the system. In some military equipment with high heat dissipation, metal substrates are often adopted.

The characteristics of military PCB

Military PCB has the following characteristics:
1. High reliability
In military applications, reliability is crucial. Military PCB must be able to ensure stability in extreme environments to ensure the smooth completion of military tasks. The high reliability of the military PCB is mainly manifested in the control of the thickness of the copper of the hole wall or avoiding welding repairs or cutting circuit supplementation to ensure the performance and safety of the circuit board.

2. High -intensity
The high strength of military PCB refers to its ability to withstand high -intensity use environments, including high temperature, low temperature, high radiation, vibration, etc., while ensuring the stability and reliability of the circuit. This high -intensity is determined by military PCB materials and structural design to ensure that it can work normally in harsh environments and meet the special needs of military applications.

3. high heat dissipation properties
The military PCB’s high heat dissipation properties refer to their good thermal conductivity and heat dissipation capabilities, which can quickly pass and distribute the heat generated during the work of the circuit to ensure the stability and reliability of the circuit. This high heat dissipation is determined by the military PCB materials and structural design to meet the needs of military applications under high load and long -term work.

4.high confidentiality
The high confidentiality of military PCB refers to its good electromagnetic shielding and information security performance, which can prevent electromagnetic leakage and information leakage, to ensure the confidentiality and security of military equipment. This high secret is determined by military PCB materials and structural design to meet the special needs of military applications in information security.

5. high durability
The high durability of military PCB refers to its good mechanical strength and stability, and can work for a long time in harsh environments to ensure the reliability and service life of military equipment. This high durability is determined by military PCB materials and structural design to meet the special needs of military applications in a complex and changeable environment.

The testing standards for military-grade boards

There are different electrical test requirements as per MIL-PRF-55110 and MIL-PRF-31032 standards.

Electrical test requirements as per MIL-PRF-31032 standard
➤Continuity should be less than 10 Ω.
➤Isolation should be more than 2 mΩ and can be managed up to more than 10 mΩ for stringent requirements.
➤Voltage should be at least 40 volts unless otherwise specified.

Subject to all group A testing per C=0 sampling plan:
The following tests should be performed on a monthly basis on thermally stressed cross-section of every panel in X and Y direction.

➤Solderability
➤Ionic contamination
➤Dimensional & hole sizes
➤Plating adhesion test
➤Solder mask adhesion testing
➤Legend adhesion
➤Surface finish thickness – XRF
➤Bow and twist
➤Electrical testing (continuity and isolation)
➤Copper tensile and elongation should be tested monthly

Electrical test requirements as per MIL-PRF-55110 standard

➤Continuity should be less than 10Ω.
➤Isolation should be more than 10mΩ, including metal core jobs.
➤Voltage should be at least 40 volts unless otherwise specified.

Subject to all group A testing per C=0 sampling plan: The following tests should be performed on a monthly basis on thermally stressed cross-section of every panel in X and Y direction.

➤Solderability
➤Ionic contamination
➤Dimensional & hole sizes
➤Plating adhesion test
➤Solder mask adhesion testing
➤Legend adhesion
➤Surface finish thickness – XRF
➤Bow and twist
➤Electrical testing (continuity and isolation)
➤Copper tensile and elongation

Military PCB application

Military PCB (printing circuit board) is widely used in the military field, and its high reliability, stability and excellent performance make it an indispensable core component in military electronic equipment. The following are the main application areas of military PCB:

1. Missile system: Military PCB plays a key role in the guidance, control and communication systems of missiles to ensure that the missile can perform the task accurately and stably.

2. Aircraft and spacecraft: In the aerospace system, communication system, and navigation systems of aircraft and spacecraft, military PCB is responsible for connecting and supporting various electronic components to ensure the safe and stable flight of aircraft and spacecraft.

3. Chariot and ships: Military PCB plays an important role in the control system, communication system and weapon system of chariots and ships to improve combat effectiveness and survivability.

4. Radar and electronic warfare systems: radar and electronic warfare systems are key technologies in the military field. Military PCB undertakes tasks such as signal transmission, data processing and communication connection to ensure the stable operation of the system and efficient operations.