Key points of PCBA process control and quality control
PCBA manufacturing process involves a lot of links, we must control the quality of each link to produce good products. The general PCBA is a series of processes such as PCB manufacturing, component procurement and inspection, SMT patch processing, plug-in processing, program burning, testing, aging and so on. Every link needs to be paid attention to.
1, PCB manufacturing
After receiving the order of PCBA, we analyze the Gerber file, pay attention to the relationship between the spacing of the PCB and the bearing capacity of the plate, do not cause the bending or break, whether the wiring takes into account the key factors such as the high frequency signal interference, impedance and so on.
2. Procurement and inspection of components
The procurement of components requires strict control of the channel. It is necessary to pick up goods from large traders and original factories. 100% avoid second-hand materials and fake materials. In addition, set up special inspection posts, strictly check the following items to ensure that the components are free of malfunction.
PCB: reflow oven temperature test, no fly line, through hole plugging or leakage, ink, plate bending, etc.
IC: check whether silk screen is identical with BOM and keep constant temperature and humidity.
Other common materials: screen printing, appearance, electrified measurement, etc.
The inspection items shall be conducted according to the sampling inspection method, with a ratio of 1-3%.
3, SMT Assembly processing
The temperature control of solder paste printing and reflow soldering is the key point. It is very important to use laser steel net with better quality and process requirements. According to the requirements of PCB, part of the steel mesh needs to be enlarged or reduced, or U hole shall be used to make steel mesh according to the technological requirements. The furnace temperature control of reflow soldering is very important for solder paste infiltration and welding reliability. It can be controlled according to the normal SOP operation guidelines. In addition, AOI testing is necessary to minimize the adverse effects caused by human factors.
4, plug-in processing
In the plug-in process, the design of the mould for over wave soldering is the key point. How to use mold to maximize the probability of good products after furnace is a process for PE engineers to constantly practice and experience.
5. Program burning
In the previous DFM report, customers could be advised to set up some test points on PCB (Test Points) to test the PCBA circuit conductivity of all PCB and all components. If there is a condition, you can ask the client to provide the program and burn the program into the main control IC by burning the machine (such as ST-LINK, J-LINK, etc.), so it can be more intuitively tested for the functional changes brought by the various touch actions to verify the functional integrity of the block PCBA.
6, PCBA board test
For orders with PCBA test requirements, the main test contents include ICT (In Circuit Test), FCT (Function Test), Burn In Test (aging test), temperature and humidity test, drop test and so on, which can be operated and summarized according to the customer's test scheme.