PCBA processing process involves many links, so we must control the quality of each link to produce good products. The general PCBA is a series of processes, such as PCB board manufacturing, component procurement and inspection, SMT SMT chip processing, plug-in processing, program firing, testing, aging and so on. Next, we will elaborate on the points needing attention in each link.
1. PCB manufacturing
After receiving the PCBA order, analyze Gerber file, pay attention to the relationship between PCB hole spacing and board bearing capacity, do not cause bending or fracture, and whether high frequency signal interference, impedance and other key factors are considered in wiring.
2. Purchase and inspection of components
We need to strictly control the channels of purchasing components. We must take delivery from large traders and original factories, and avoid second-hand materials and fake materials 100%. In addition, a special incoming inspection post is set up to strictly check the following items to ensure that there is no fault in the components.
PCB: reflow oven temperature test, no flying wire, via hole blocking or ink leakage, board surface bending, etc;
IC: check whether silk screen printing and BOM are completely consistent, and do constant temperature and humidity preservation;
Other common materials: screen printing, appearance, power on test value, etc. the inspection items are carried out according to the sampling method, and the proportion is generally 1-3%.
3. SMT assembly processing
Solder paste printing and reflow furnace temperature control are the key points. It is very important to use laser steel mesh with good quality and meet the process requirements. According to the requirements of PCB, some of them need to increase or reduce the steel mesh hole, or use U-shaped hole to make steel mesh according to the process requirements. The furnace temperature and speed control of reflow soldering is very important for solder paste infiltration and welding reliability. It can be controlled according to normal SOP operation guidelines. In addition, AOI detection should be strictly carried out to minimize the adverse effects caused by human factors.
4. Dip plug in processing
In the process of plug-in, the mold design of over wave soldering is the key point. How to use the mold to maximize the probability of good products after the furnace is a process that PE engineers must constantly practice and summarize experience.
5. Programmed firing
In the previous DFM report, it is suggested to set some test points on PCB to test the continuity of PCB and PCBA circuit after soldering all components. If possible, customers can be required to provide programs to burn programs into the main control IC through burners (such as st-link, j-link, etc.), so that the functional changes caused by various touch actions can be more intuitively tested, so as to test the functional integrity of the whole PCBA.
6. PCBA board test
For the order 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, etc., which can be operated according to the customer's test scheme and the report data can be summarized.
