PCB Assembly quality control methods as following
1. Make production documents and check it strict
Perform DFM manufacturability analysis on customer PCB, BOM, schematic, 3D drawings, assembly manuals, and so on, follow check one by one:
a) Check the document version and final repair time
b) Process: environmental protection
C) If marking of the directional components on the PCB silkscreen, and the patch coordinate file are complete and clear
d) Whether the model, brand, and silkscreen mark of electronic components in the BOM are complete and clear
e) Prototype PCB board manufacturing process requirements. (Base material, number of layers, copper thickness, board thickness, surface treatment, impedance, special through-hole methods, etc.)
f) Whether PCB routing, windowing, boarding, solder mask, aperture and device layout are reasonable
g) Whether the patch coordinate file is complete and clear
h) IC programming process (before production or after mounting)
i) Whether the material, size, and special process are clearly marked in 3D drawings such as the shell
j) Whether the requirements, standards, and operating instructions of the assembly manual are clear and accurate
k) Whether the test plan is complete and clearly
l) Customer’s special requirement
2. The meeting before production
The marketing, project manager, purchasing, engineering, production, PMC, quality to attend the meeting. Will clarify the customer’s background and requirements, to marking if something special attention during the order production. That to facilitate the actual Better collaboration in production.
3. Choose a reliable PCB manufacturer
Choose high-end PCB production plants with abundant production capacity, punctual delivery, and stable quality. They support special process requirements such as multilayer boards, HDI, FPC, impedance, and blind buried vias. They use Rogers A+ grade substrates and are equipped with high-end fully automatic copper sinking. Drilling production line, 100% factory inspection of all products, to ensure the quality of prototype PCB board.
4. First choose a High-level component agent or trader
Cooperation with top-level components agents and establish long-term and stable cooperation ship to ensure 100% original purchases from the supplier.
5. IQC incoming inspection
Check the incoming materials of prototype PCB board, components, stencil, and fixtures to ensure compliance. With circuit electrical design and production requirements at the source. Which greatly improves production quality.
6. Storage of sensitive components
Special constant temperature and humidity storage for sensitive components. Such as IC and BGA to ensure. That they remain in a stable state will help improve the reliability of later welding.
7. Solder paste printing
Solder paste printing is very important to the entire soldering process, it will control as follow for reference:
a) Choose well-known brand of solder paste
b) Stirring of solder paste: Stir clockwise for 2-5 minutes with an automatic solder paste mixer. Until the solder paste reaches a silky viscous state;
c) Laser stencil: fine-tuning the opening according to the engineering process to ensure the control of solder paste printing
d) Fully automatic solder paste printing machine: Automatically scan Mark points. Adjust printing coordinates and detect the thickness of solder paste printing.
8. PCB, IC, BGA baking
A professional oven is used to bake PCB, important IC, and BGA for 2-12 hours. Which is convenient to remove the moisture on the pads and pins. And can ensure reliability in the chip soldering process to the greatest extent.
9. SMT patch
Automatic high-end SMT placement machine, electric feeder feeding, perfect realization of 01005 placement accuracy. Support precision placement of mainstream IC, BGA, QFN, PLCC, and other components.
Based on the BOM list and production documents, the quality department inspects the first product . After the SMT placement is completed item by item to avoid major errors such as wrong materials. Wrong directions and positions, and line inspections to control quality during mass production.
11. Reflow soldering
10 temperature zone reflow soldering. Precise furnace temperature control, smooth furnace temperature curve, and effective control of the soldering process.
12. AOI inspection
It will be passed inspect by AOI 100% when finish reflowed, scanned and photographed, compared with the preset PCB images. Effectively preventing defects such as solder connection, false soldering, false soldering, component shedding, and component reverse.
13. X-Ray detection
Equipped with X-Ray equipment to perform X-scanning of PCB circuit boards containing BGA. And detect whether there are defects such as BGA solder balls connecting tin, false soldering, solder balls falling off. And air bubbles through equipment imaging, and 100% guarantee the BGA soldering effect.
14. DIP plugin
We own 4 DIP plug-in production lines. Equipped with auxiliary tools such as automatic track cable, trimming machine, shaping machine, etc. Normalized worker training. And dedicated personnel to ensure the efficiency and quality of the plug-in.
15. Wave soldering
Precise furnace temperature control (±3°C). Adjust the furnace speed and slope according to the requirements of prototype PCB board and components, select the corresponding flux. And use customized carriers for mass production to ensure the consistency and yield of welding.
16. ICT test
PCB designers are required to reserve test points on the board surface. To make professional test fixtures, perform ICT test on the soldered prototype PCB board, external power supply and load. And test the voltage and current values. Between test points to ensure input and output and design test plan is the same to test the electrical PCB.
17. Program burning
According to customer requirements, the PCB is programmed to burn, support J-Link, ST-Link and other mainstream programmers. The production line is equipped with a computer and assembly line operation.
18. Functional test
After burning, connect the prototype PCB board to the load, simulate user input and output. Perform function testing on the PCB board, realize the joint debugging of software and hardware. And ensure the normal front-end manufacturing and welding.
Custom PCB Assembly test can be divided into ICT test, FCT test, aging test, vibration test, etc.
The custom PCB Assembly board test is a big test. According to different products and different customer requirements, the test methods used are different. The ICT test is to detect the welding condition of the components and the on-off condition of the circuit. The FCT test is input and output parameters of the custom PCB Assembly board, the check if it meets for the condition.
19. Product assembly
Equipped with 4 professional automatic finished product assembly production lines. Equipped with professional tools and auxiliary materials, and assembled in strict accordance with the customer’s assembly manual. Reasonable division of production area, setting standard line-side material in and out and recording, effectively prevent wrong material.
Set up OQA positions, and conduct AQL project inspections on the final products before they leave the factory
a) Appearance: check the appearance items such as scratches, signs, etc.
b) Whether the inner packaging accessories are complete
c) Whether the product function meets the design requirements
Ensure that 100% of the test passes. If one piece is found to be defective, the entire batch will be returned. For a full inspection until the problem is found and effectively improved. Under normal circumstances, customers will also cooperate in this link to conduct QC random inspections until they reach the standard.
21. Aging test
Equipped with professional aging test frame, 100% product aging. (Aging method, time and environment, base on client’s requirement), independent aging area.
22. Vibration test
A professional vibration tester used for long-period testing to ensure it’s no falling off of the welding components. The sampling test ratio is determined according to customer requirements.
23. High and low-temperature test
Equipped with a professional test room, and targeted testing services in common temperature zones such as -40℃ to 100℃. fully simulate the ambient temperature of the product, and maximize the reliability of the product.
24. Packaging logistics
a) Ordinary carton packaging
b) EPE protection (ten-level anti-static)
c) Independent packaging of products
The above is the quality control method of the custom PCB Assembly production process. Only by strictly checking every link and process can a perfect production be created.