After SMT reflow soldering we will encounter some defective phenomena, these SMT processing soldering defects will directly or indirectly affect the quality of the product. These defective phenomena are clear SMT operators on the patch processing defects judgement, so as to provide the industry benchmark for production improvement and operation of the bad name. In the actual patch processing for these defective phenomena detected, are to be strictly rework or remedial treatment. So how should we understand to determine the bad phenomenon?
Below for you to sort out the following:
1. (even tin) SMT processing welding even tin is also known as tin bridge, between component ends, between adjacent solder joints of components, as well as solder joints and adjacent wires, perforations, etc. should not be connected by the part of the solder connected together, SMT processing industry called even tin.
2. (monument) tombstone, also known as the Manhattan phenomenon, refers to the two soldering end of the chip components, after reflow soldering, one of the soldering end away from the pad surface of the entire component was oblique and upright. SMT industry called the monument.
3. (side stand) chip component side and PCB pad contact phenomenon. the SMT industry called side stand.
4. (offset) components in the horizontal position to move, resulting in the solder end or pin is not attached to the PCB pad.
5. (anti-white) piece of component front to the PCB, the bottom side up phenomenon.
6. (tin beads) in the reflow soldering, attached to the piece of component side or scattered in the solder joints annex tiny beads of solder.
7. (cold soldering) reflow incomplete phenomenon, the solder does not reach its melting point temperature or welding heat is not sufficient, so that it is solidified before the wetting and flow, there is no formation of any metal alloy layer, so that all or part of the solder in a non-crystalline state and simply build up on the surface of the metal being soldered.
8. (core suction) solder from the pad along the pin to climb up to the pin and the chip body, resulting in insufficient solder or empty solder at the solder joints.
9. (reverse) refers to the polarity of components after welding, the polarity of the direction of the actual requirements of the direction is not consistent.
10. (bubble) solder in the solidification of gas before the failure to escape in time, the formation of hollow phenomenon inside the solder joint.
11. (pinhole) in the solder joint surface to form needle-like holes.
12. (fissure) solder joints due to mechanical stress or internal stress caused by the phenomenon of cracked solder joints.
13. (tin tip) welding at the outward protruding needle-like or spiky tin.
14. (more tin) soldering at the solder is much more than the normal amount of demand, so that it is difficult to see the outline of the soldered parts or solder to form a pile of spherical.
15. (open solder) component pins / solder end of all out of or away from their corresponding pads, and not due to soldering.
16. (white spots) appeared in the laminated substrate inside a phenomenon, in which the glass fibres in the longitudinal and transverse crossings and resin separation. This phenomenon is manifested as discrete white spots or the substrate surface under the “cross-shaped”, usually associated with the formation of stress due to heat.
17. (grey welding) due to high welding temperature, excessive flux evaporation and repeated welding, etc., the surface of the weld is grey, the solder crystal loose, porous and slag-like.
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Post time: Aug-04-2023