1. Short circuit
Refers to thephenomenon of joining between two independent adjacent solder joints aftersoldering. The cause is that the solder joints are too close, the parts arearranged improperly, the soldering direction is incorrect, the soldering speedis 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 onthe tin trench, and the parts and the substrate are not welded together. Thereasons for this situation are unclean welding trenches, high feet, poorsolderability of parts, extravagant parts, improper dispensing operations, andoverflow of glue in the welding trenches. The first class will cause emptywelding. The PAD parts of the empty welding are mostly bright and smooth.
3. False welding
There is tin betweenthe foot of the part and the welding trench, but it is actually not completelycaught by the tin. Most of the reason is that rosin is contained in the solderjoints or caused by it.
4. Cold welding
Also calledundissolved tin, it is caused by insufficient flow soldering temperature or tooshort flow soldering time. Such a shortcoming can be improved by secondary flowsoldering. The surface of the solder paste at cold solder joints is dark andmostly powdery.
5. Parts fall off
After the solderingoperation, the parts are not in the proper position. The reasons for this areimproper selection of glue material or improper glue dispensing operation,incomplete maturation of the glue material, excessive tin wave and too slowsoldering speed, etc.
6. Missing parts
Parts that should beinstalled but not installed.
7. Damaged
The appearance ofthe parts is obviously broken, material defects, or process bumps are caused,or the parts are cracked during the soldering process. Insufficient preheatingof parts and substrates, too fast cooling rate after soldering, etc., allcontribute to the tendency of parts to crack.
8. Denudation
This phenomenonmostly occurs on passive parts. It is caused by poor plating treatment on theterminal part of the part. Therefore, when passing through the tin wave, theplating layer melts into the tin bath, causing the structure of the terminal tobe damaged, and the solder does not adhere. Good, and higher temperature andlonger soldering time will make the bad parts more serious. In addition, thegeneral flow welding temperature is lower than wave welding, but the time islonger. Therefore, if the parts are not good, it will often cause erosion. Thesolution is to change the parts and control the flow welding temperature andtime appropriately. The solder paste with silver content can inhibit thedissolution of the end of the part, and the operation is much more convenientthan the change of the solder composition of wave soldering.
9. Tin Tip
The surface of thesolder joints is not a smooth continuous surface, but has sharp protrusions.The possible causes of this are excessive soldering speed and insufficient fluxcoating.
10. Shaoxi
The amount of tin inthe welded parts or parts feet is too small.
11. Tin ball (bead)
The amount of tin isspherical, on the PCB, part, or part foot. Poor quality of solder paste orstorage for too long, unclean PCB, improper solder paste coating operation, andtoo long operation time of solder paste coating, preheating, and flow solderingare all likely to cause solder balls (beads).
12. Open circuit
The line should beturned on but not turned on.
13. Tombstone effect
This phenomenon isalso a kind of open circuit, which is easy to occur on CHIP parts. The cause ofthis phenomenon is that during the soldering process, due to the differenttensile forces between the different solder joints of the parts, one end of thepart is tilted, and the tensile force at both ends is different. So thedifference is related to the difference in the amount of solder paste,solderability and tin melting time.
14. Wick effect
This mostly occurson PLCC parts. The reason for this is that the temperature of the part feetrises higher and faster during flow soldering, or the solder cut has poorsolderability, which causes the solder paste to rise along the part feet afterthe solder paste melts. , Resulting in insufficient solder joints. In addition,insufficient preheating or no preheating, and easier flow of solder paste,etc., will promote this phenomenon.
15. CHIP parts turnwhite
In the SMT process,the marked surface of the part value is soldered on the PCB upside down, andthe part value cannot be seen but the part value is correct, which will notaffect the function.
16. Reversepolarity/direction
The component is notplaced in the specified orientation.
17. Shift
18. Too much or notenough glue:
19. Side Standing