SMT007 Magazine

SMT-July2018

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60 SMT007 MAGAZINE I JULY 2018 There are several instances where the gold contacts on PCBs need to be replated. IPC A-610 discusses several of these cases. One of the more common defects is when solder "splashes" onto the contact during the wave or selective soldering process, thereby contam- inating it. This requires that the operator strip away the solder, first by wicking off excess solder and then to a greater degree via mechan- ical and chemical stripping means. This is then followed by a replating of the contacts. Another defect is when "pitting" occurs in the contact area. This pitting is a result of a defective plat- ing operation. Many times, this defect can be buffed out and then it can be replated. Other times, the contact area is scratched, which similarly requires the buffing out of the scratch followed by replating. Gold replating of these contacts is a process that requires setup, special chemistry that requires advanced PCB repair tech skill, and the correct materials and training. The operator skills required for gold contact replating are similar to those required for micro device rework and PCB repair. Patience, dexterity and the ability to improvise correctly if the standard process followed does not go as planned are all attributes of a PCB rework and repair technician. The most experienced and skilled techs are the right ones for being trained to perform PCB repair techniques such as gold finger replating. Numerous materials are required for the proper repair of gold fingers per the indus- try standard IPC-7721 4.6.3, which in many cases can be had in a complete replating kit. Knocking Down the Bone Pile by Bob Wettermann, BEST INC. Replating of Gold Fingers: Getting the Shine Back

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