Contract PCB Assembly for Multilayer PCB
SMT common defects
1. Empty soldering-- there is no joint between the part foot or lead foot and the tin pad due to no tin or other factors.
2. False welding-- false welding is similar to that of empty welding, but the amount of tin pad is too little, which is lower than the joint surface standard.
3. Cold welding-- there are still fuzzy granular attachments on the tin gaskets after the tin or tin paste is gasified in the return air stove.
4. Bridge -- there is a short circuit between the feet where the foot parts are connected by excess solder, and another phenomenon is caused by the use of tweezers and bamboo sticks by inspectors.Improper operation of chips may lead to short circuit for foot to foot contact, or shave chip foot may cause residual tin residue leading to short circuit for foot to foot.
5. Wrong parts-- if parts specifications or types are placed inconsistent with the operation regulations or BOM and ECN.
6. Missing parts-- the address where the parts should be placed, which is caused by abnormal conditions.
7. Polarity reversa-- polarity azimuth accuracy is not the same as the assembly of engineering samples, that is, polarity error.
8. Parts upside down-- SMT parts shall not be upside down. In addition, CR shall not be dumped without polarity because the bottom part is completely white and there is no specification mark.
9. Part offset-- the welding point of SMT all parts' surfaces shall not be deviated from pad position by more than 1/2 area.
10. Tin PAD damage-- in the normal process, after the return air furnace gasification welding, can not damage tin PAD, the cause of general tin PAD damage is improper use of soldering iron to repair, for lightly can be shipped normally after repaired, seriously is included in the secondary judgment, or transplant scrap.
11. Dirty contamination-- SMT processing operations are not good, resulting in unclean board surface or foreign bodies attached between the feet of chips, or chips repair is not good, a little glue, anti-solder spot paint are considered as unqualified products. However, the repair supplement may be included in the secondary judgment as the case may be.
12 SMT blast board-- PC board after the blast furnace in high temperature, due to the board itself poor material quality or blast furnace temperature anomalies, resulting in the board layer blister or white spot phenomenon is a defective product.
13. Package welding-- solder joints with too much solder to see parts feet or their outline.
14. Tin ball, tin slag-- PCB board surface attached to excess solder ball, tin slag, are rejected.
15. Foreign bodie-- residues, iron scraps, staples and other adhesive board surface or stuck in the parts between the feet, shall be rejected.
16. Pollution-- serious impurity, such as solder pollution oxidation of parts, residual rosin on the board surface is not cleared, cleaning does not pay attention to the chips pollution oxidation and cleaning impurity (such as SLOT SLOT impurity,SIMM impurity, board CHIP or SLOT side impurity,SLOT inside with many small tin particles,PC board surface water grain...) is not acceptable.
17. Stilt skin-- no more than 10% cracked of the joints related to the parts' feet, and no more than 25% cracked of the joints unrelated to the copper foil line.
18. PCB bending deformation-- if the pcb bending deformation exceeds 0.5% or more of the diagonal length of the pcb, it shall be judged as rejected.
19. Collision Angle, board damage-- board damage caused by abnormal reasons can be accepted by qualified products if it is well repaired, otherwise it will be included in the sub-product judgment.
20.DIP explosion-- after DIP high temperature for pcb assembly, due to the PC board itself poor material or tin furnace solder joint temperature is too high, resulting in PC board layer blister or white spot phenomenon is a bad product.
21. Kneel-- CACHE RAM, K/B B10S...PIN and other parts are discounted to form kneeling feet.
22. Floating parts-- according to regulations, the parts must be inserted to the bottom (flat paste) or positioning holes. The standard for floating parts is slot, and the floating height of SIMM cannot exceed 0.5mm, while the traditional parts are recommended to be no more than 1.59mm.
23. Scratch-- pay attention to the PCB board accumulation improper protection or improper protection of heavy industry scratches.
24.PCB board different colors-- due to reflow welding caused by the board color darkening or improper baking lead to be yellow or black, which is not acceptable.However, as the case may be included in the sub-standard judgment acceptable.
25. Poor repair-- the repair line is not glued to the substrate flat or the repair line is not solderproof.