Microwave Tech - Precautions for PCB assembly solder joint quality

Nowadays, with the development of science and technology, smart phones, tablet computers and other electronic devices tend to be light, small and portable. The electronic components selected in PCB assembly are also shrinking. In the past, 0402 resistance capacitors were also replaced by 0201 size. How to ensure the quality of solder joints has become a key issue of high-precision patches, As a bridge of welding, the quality and stability of solder joints on PCB circuit board determine the quality of electronic components and equipment. In other words, in the process of PCB board processing, the quality of PCBA processing is finally expressed as the quality of solder joints.

1. Select on-line tester and professional equipment for testing.

2. During visual inspection or AOI inspection, SMT technical quality inspectors need to pay attention when they find that there are too few welding materials, poor solder penetration, broken joints in the middle of the solder joint, convex spherical solder surface, or incompatibility between solder and SMD. Even minor conditions will lead to hidden dangers, and they should immediately judge whether there is a batch of false welding problem, The judgment method is: check whether there are many solder joints at the same position on PCB circuit boards. For example, the problems on some PCB circuit boards may be caused by solder paste scraping and pin deformation. For example, there are problems at the same position on many PCB circuit boards. At this time, it is likely to be caused by poor components or pad problems.

Causes and solutions of faulty welding.

1. The pad design is defective. The through hole in the pad is a major disadvantage of PCB design. It is not necessary to use it. The through hole will cause solder loss, resulting in insufficient welding materials. The pad spacing and area also need to be standardized for SMT patch matching, otherwise the design should be corrected as soon as possible.

2. The PCB board is in oxidation condition, that is, the welding pad is dark. If there is oxidation condition, the oxidation layer can be removed with an eraser to make it bright again. The PCB circuit board is damp. If you suspect, you can put it into the drying oven for drying. If the PCB board is polluted by oil, sweat and so on, you should clean it with absolute ethanol.

SMT chip processing is a key stage in one-stop PCBA chip processing. Such a stage will seriously affect a PCBA product processing plant or even the product quality of this batch of products. In SMT OEM, electronic PCB assembly plants generally have strict chip processing regulations, which stipulate that chip processing personnel carry out chip processing according to such a process, These articles of association are analyzed from the precautions in every detail.

1. The PCB circuit board must be prepared before welding, so that the bonding pads of components and PCB circuit board can be solderable.

2. During SMT patch processing and welding, PCBA processing SMT technical operators must wear anti-static caps and pull up all their long hair, which is tightly covered by the static caps.

3. During SMT patch processing and welding, the soldering iron head shall not be immersed in the flux for a long time, and other highly corrosive chemical industrial products shall not be used as flux.

4. Electric soldering iron shall be selected according to the heat required for actual welding.

5. Choosing rosin solder paste as flux can improve the wetting effect of components and increase the weldability of components during welding. The flux can be directly used as rosin block or configured as rosin alcohol solution.