The cleaning after PCB manufacturing and soldering refers to the use of physical action and chemical reaction methods to remove the flux residues remaining on the surface layer of the surface layer assembly board after PCB reflow soldering, wave soldering and manual soldering, and the PCB manufacturing assembly assembly process The pollutants and impurities caused by the process are harmful to the surface-layer assembled board.
The activator added in the flux and the welding sound contains a small amount of western compounds, acid or salt, and the residual debris will cover the surface of the solder joint after welding. When the electronic device is powered on, the ions of the remaining impurities will migrate to the electrical conductor with the opposite polarity, which may cause a short circuit in severe cases.
2. At this stage, the halides and chlorides in the more common fluxes have very strong activity and hygroscopicity, which will corrode the substrate and solder joints in the humid environment, which will reduce the insulation resistance of the substrate surface layer and cause electromigration. , When the situation is serious, it will conduct electricity, causing short circuit or open circuit.
3. Products with special requirements for high-standard military products, medical products, instruments, etc. need to be treated with three-proofing. The standard before the three-proofing treatment has a high degree of cleanliness, otherwise it will be exposed to relatively harsh environmental conditions such as hot flashes or high temperatures. Cause serious consequences such as electrical performance degradation or failure.
4. Due to the speed shift of the residual debris after welding, the test probe contact is not good during the online test or the function test, which is prone to false test
5. For high-standard products, some defects such as thermal damage and delamination cannot be exposed due to the occlusion of residual debris after welding, resulting in missed inspection and affecting reliability. At the same time, many impurities also affect the appearance of the substrate and the commercial nature of the board.
6. Residual debris after soldering will affect the connection reliability of high-density, multi-I/O connection point array chips and flip-chip chips.