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What are the common defects in PCBA processing
1. Short circuit
Refers to the phenomenon of joining between two independent adjacent solder joints after soldering. The cause is that the solder joints are too close, the parts are arranged improperly, the soldering direction is incorrect, the soldering speed is too fast, the flux coating is insufficient, and Poor solderability of parts, poor solder paste coating, excessive solder paste, etc.
2. Empty welding
There is no tin on the tin trench, and the parts and the substrate are not welded together. The reasons for this situation are unclean welding trenches, high feet, poor solderability of parts, extravagant parts, improper dispensing operations, and overflow of glue in the welding trenches. The first class will cause empty welding. The PAD parts of the empty welding are mostly bright and smooth.
3. False welding
There is tin between the foot of the part and the welding trench, but it is actually not completely caught by the tin. Most of the reason is that rosin is contained in the solder joints or caused by it.
4. Cold welding
Also called undissolved tin, it is caused by insufficient flow soldering temperature or too short flow soldering time. Such a shortcoming can be improved by secondary flow soldering. The surface of the solder paste at cold solder joints is dark and mostly powdery.
5. Parts fall off
After the soldering operation, the parts are not in the proper position. The reasons for this are improper selection of glue material or improper glue dispensing operation, incomplete maturation of the glue material, excessive tin wave and too slow soldering speed, etc.
6. Missing parts
Parts that should be installed but not installed.
7. Damaged
The appearance of the parts is obviously broken, material defects, or process bumps are caused, or the parts are cracked during the soldering process. Insufficient preheating of parts and substrates, too fast cooling rate after soldering, etc., all contribute to the tendency of parts to crack.
8. Denudation
This phenomenon mostly occurs on passive parts. It is caused by poor plating treatment on the terminal part of the part. Therefore, when passing through the tin wave, the plating layer melts into the tin bath, causing the structure of the terminal to be damaged, and the solder does not adhere. Good, and higher temperature and longer soldering time will make the bad parts more serious. In addition, the general flow welding temperature is lower than wave welding, but the time is longer. Therefore, if the parts are not good, it will often cause erosion.
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