1. Discussion on PCBA technology
The PCBA manufacturing process is a very complicated process. The entire PCBA process seems to be only one word different from the PCB. In fact, it varies greatly. PCBA has a series of back-end processes based on the PCB, such as solder paste printing, SPI inspection, SMT processing, reflow soldering, DIP post-soldering, wave soldering / selective wave soldering, PCBA first-piece inspection, etc. These processes are PCB does not come with.
However, because all the following processes are based on the PCB board, the quality of the PCB determines the quality of the entire PCBA. So what aspects of the PCB have an impact on the PCBA? Today, the FASTPCBA technician will share with you.
First, the board is dirty
Dirty board surface is mainly caused by high flux solid content, excessive coating amount, preheating temperature is too high or too low, or because conveyor belt PCB clamping claws are too dirty, too much oxide and tin slag in the solder bath, etc. .
The main solution is to choose the appropriate flux; control the flux coating amount; control the preheat temperature; check the cleaning effect of the automatic cleaning PCB clamping claws and take measures; timely clean up the oxide and tin slag on the surface of the solder bath.
Second, white residue
The white residue is commonly known as hoarfrost. Although it does not affect the surface insulation resistance, but the customer does not accept it.
Solution: first use the flux and then the solvent to clean it; if it cannot be cleaned, it may be due to the aging of the flux, or it may be exposed to the air to absorb water vapor, or it may be due to the high moisture content in the cleaning agent (solvent), or the flux does not match the cleaning agent, the supplier should be asked to help resolve or replace the flux, cleaning agent.
Third, PCB deformation
PCB deformation is mainly caused by large PCB quality or uneven component layout
When designing the PCB, try to make the components evenly distributed. Design a support belt in the middle of the large-sized PCB (design the non-layout component area with a width of 2 ~ 3mm); or use a mass-balanced tool to press the sparse components on the PCB to realized quality balance during welding.