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What are the solder problems of printed circuit boards

Printed circuit board solder work always has the problem of poor solder spots, and this problem has been a lot of problems, it seems that there will always be new problems, so we sort out some rules, as a basis for finding out the problem. The problem on the circuit board is often caused by the solder operation, but before determining that is caused by the solder operation, should first consider all kinds of other reasons, and then consider the solder operation, most of the problems between the solder operation in the material changes and operating conditions change.

1, circuit board short circuit
When the circuit board after welding over the aging process will find some circuit board short circuit, discharge circuit board design and electronic components of the problem, can be found from the following aspects to find the circuit board solder tin eating time is too short, resulting in poor welding. Flux itself activity is not strong, weakened solder wettability and its expansion. Circuit board into the direction of tin and tin wave direction, solder level oxide too much to affect the welding.
2, after soldering tin point dull and dull
Solder found that the tin point is dark without lustre, from two aspects one is the degree of solder is too low. Solder joints with more than 50% tin content will be shiny. On the other hand, the residue of flux remains on the surface of the solder spot without cleaning and the acid corrodes the solder spot and causes the solder spot to be dull and dull.
3. The surface of tin spot is rough after soldering
The roughness of the surface of the tin spot first depends on the quality of the solder. The solder itself contains a variety of small amounts of metal elements. When the content of these metal elements exceeds its limit, it will affect the surface of the tin spot. Solder requires that the surface of the liquid tin impurities, when the surface of the liquid tin oxidation too much time to clean up otherwise it will affect the surface of the tin point.
4. The solder joint is yellow in color
Yellow solder joint color is a common problem, many people do not know why. The color of the solder usually has a considerable relationship with the temperature. When the solder temperature is too high the surface of the liquid tin yellowing. It is necessary to adjust the appropriate operating temperature of the tin furnace.

Poor local tin adhesion
This kind of phenomenon and stick tin bad similar, different is the local stick tin bad situation, will not expose the copper surface, only thin for a while solder can not form full solder spot, its formation reason in stick tin bad similar. Two solder discharges may not improve the situation, you must remove the solder with a solder stripping agent, clean the surface again and do the solder again. Electroplating pollution did not clean up, will produce local tin bad, this kind of problem, should be sent back to the circuit board manufacturers to deal with again.

White residue
1. After welding or cleaning, white residue is found on the circuit board, which is usually the residue of rosin. Such material will not affect the surface resistance value, so it is usually not acceptable for customers.
2 flux is usually the main role of this problem, sometimes switch to another that will not have a problem, rosin type flux often produce white spot phenomenon when cleaning.
3. When making circuit boards, residual substances, in the storage of a long time, will produce a day shift, but this problem can be cleaned with a strong solvent.
4. Improper treatment of the circuit board will cause white spots, often a batch of circuit boards will produce problems, but other will not, this problem can be cleaned with a strong solvent.
5. Flux and oxidation protection have not been compatible, just change to another flux can improve the problem. This problem is also caused by solvent degradation of PCB board during the production process. Therefore, it is recommended that the storage time should be as short as possible. Solutions in the process of nickel plating often cause this problem, which should be paid special attention to.
6 flux used for a long time aging, exposed to air moisture absorption caused by white spots, when using fresh flux, solder after too long time before cleaning, so that it is not easy to clean. Minimizing the delay time between soldering and cleaning will improve the situation.
7. Excessive water content in the solvent to clean circuit boards, reducing the cleaning ability. The solution is to remove water from the solvent properly, such as using a water separator or placing a water-absorbing material in the separator.

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