Key points of automobile PCBA production: the whole process specification from material control to reliability guarantee

As the core carrier of automotive electronics, PCBA (printed circuit board assembly) directly affects the safety, reliability and durability of automobiles in its production process, which needs to meet the stringent requirements far higher than those of consumer electronics or industrial products. The following key points should be focused on in production: Ⅰ.  Strict control of materials and components 

The "reliability" of automotive PCBA starts at the source, and the quality of materials and components is the foundation:

1. Admission threshold and traceability of automotive-grade components. All components must meet automotive certification: chips must pass AEC-Q100, passive components (resistors, capacitors, inductors) must pass AEC-Q200, connectors, relays and other standards such as ISO 16750 to ensure stability in extreme environments such as-40℃~125℃ (or even higher) temperature, vibration, humidity, etc.

Strictly review supplier qualification: give priority to suppliers with IATF 16949 certification, and avoid using "industrial grade" or "commercial grade" replacement parts (even if the parameters are close, long-term reliability differences are significant).

Full link traceability: Record the batch number, production date and supplier information of components, and bind them with PCBA production batch to ensure that the problem can be quickly located and traced. 2.PCB substrate and auxiliary material compatibility

PCB substrate should be selected with high Tg (glass transition temperature) material (Tg≥170℃), such as FR-4 high Tg sheet or polyimide material, which can withstand the high temperature of welding and long-term working temperature rise, and avoid deformation or delamination of the plate.

Soldering materials (weld paste, flux, solder mask ink) must meet automotive-grade environmental and reliability standards: The solder paste should adapt to wide temperature ranges (e.g., lead-free solderwith Sn-Ag-Cu composition, melting point 217℃); flux must be low-corrosion to prevent long-term use from corroding solder joints; and solder mask requires chemical corrosion resistance for environments like engine compartments with oily contaminants.

Ⅱ.  Fine control of production process 

The production process of automotive PCBA needs to take into account "consistency" and "ability to resist harsh environment", the core links include: 

 1. SMT (surface mount technology) process control 

Welding paste printing:

The thickness of the steel mesh and the opening size should match the vehicle-standard components (such as 0201,01005 and other small size components, or BGA, QFP and other tight foot components), to ensurethe accurate amount of solder paste (too much is easy to bridge, too little is easy to false solder).

Printing parameters (squeegee pressure, speed and demolding distance) should be verified by DOE (experimental design), and the steel grid should be calibrated every 2 hours to avoid batch defects caused by printing deviation.

Component mounting:

For large components of automotive grade (such as power modules and connectors), the pressure and precision of the suction nozzle of the mounting equipment should be calibrated (the positioning error is less than ±0.05mm) to prevent the offset of the mounting from causing stress concentration of the solder joint (easily broken under long-term vibration).

For sensitive components (such as MEMS sensors and RF chips), anti-static measures should be taken (workbench grounding and operators wearing anti-static wristbands) to avoid electrostatic breakdown.

Reflow soldering process:

The temperature curve should strictly match the specifications of components: preheating section (to avoid sudden heating of components), constant temperature section (volatilization flux), reflux section (the peak temperature should be higher than the melting point of solder 20~30℃, but not more than the upper limit of temperature tolerance of components), and cooling section (rapid solidification to ensure the strength of solder joints).

Nitrogen protection in furnace: For BGA, CSP and other tight foot components, it is recommended to use nitrogen atmosphere (oxygen content ≤500ppm) to reduce solder oxidation and reduce the risk of false soldering. 

2. DIP (plug-in) and post-weld process control 

The soldering of plug components (such as electrolytic capacitors, relays and terminals) should ensure that the solder joints are full and no false solder/cold solder: the temperature of wave soldering should be controlled at 250±5℃, and the transmission speed should match the soldering time (usually 3-5 seconds), so as to avoid the welding failure caused by lead oxidation. 

Handmade post-welding (such as high current terminal, irregular components) should use a constant temperature soldering iron (temperature 320±20℃), control the welding time (no more than 3 seconds for a single solder point), and prevent high temperature damage to components (such as electrolytic capacitors due to overheating failure). 

Ⅲ.  Full-process quality inspection and reliability verification 

The detection of automotive PCBA should run through the whole production process, and the standard is much higher than that of ordinary products:In-line detection (ICT/AOI/AXI)

AOI (Automatic Optical Inspection): Check the appearance of solder joints (bridging, false soldering, less tin), component misplacement/defect/offset after SMT. The resolution should be less than 25μm to ensure that defects of small size components are not missed. AXI (Automatic X-ray inspection): For "invisible solder joints" such as BGA and CSP, the internal cavities of solder joints are detected by X-ray (the cavity rate should be less than or equal to 5%, otherwise it will affect heat dissipation and conductivity).

ICT (online circuit test): detect circuit connectivity, resistance/capacitance/inductance values, diode/triple pole polarity, and eliminate basic faults such as short circuit and open circuit

Function and environmental reliability testing

FCT (functional test): simulate the actual working conditions of the car (such as voltage 12V/24V, load change), test the core functions of PCBA (such as battery balance of BMS, light control of BCM), and ensure that the parameter error is within the design range (such as signal acquisition accuracy ≤1%).

Environmental stress test:High and low temperature cycle: -40℃~125℃ cycle 1000 times, test the temperature fatigue of solder joints and components;

Vibration test: according to ISO 16750-3 standard, the vibration is 100 hours at 10~2000Hz frequency and 20g acceleration, to detect whether the solder joints fall off and the connector is loose;Humid heat test: 1000 hours in 40℃/95% RH environment to verify the protective effect of conformal coating and corrosion resistance of PCB.

Sampling and full inspection combined The core principle of automotive PCBA production is "reliability-first," requiring rigorous material screening, meticulous process control, comprehensive testing protocols, and compliant management systems to ensure stable operation throughout the vehicle's entire lifecycle (15 years/200,000 km), ultimately meeting safety and functional requirements. Any oversight in these processes could lead to vehicle malfunctions or even safety incidents, making "zero defects" the ultimate goal of automotive PCBA manufacturing.