SMT007 Magazine

SMT-July2018

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62 SMT007 MAGAZINE I JULY 2018 Several solutions are required for the replating process, including the gold stripping and the nickel and the gold plating solutions. Applica - tor tips are put onto the end of the electrodes and come in a variety of sizes to accommo- date the different gold finger geometries. A variable power supply will supply the current for the plating process. In addition, there are polishing materials including the polishing compound and water to rinse the remnant compound off the board. Finally, a grounding wire is used to form the bus to all the contacts requiring replat - ing. As a warning the replating area should be properly venti- lated and care must be taken for this process as the solutions are hazardous in nature. There are numerous ways personnel can be trained in this PCB repair procedure. One method is via the IPC-7721 PCB repair program. This industry certification program can accom- modate the training of this repair technique at the CIS level. Other- wise various training companies or gold replating suppliers can provide training in this repair technique. The basic replating process is referenced in IPC-7721 4.6.3 or in the manufacturer's instruc- tions as part of the gold replating kit. If the gold finger is severely damaged, a gold-plated circuit frame and the pad repair process as outlined in IPC-7721 proce- dure 4.6.1 or 4.6.2 can be utilized to replace the finger lieu of the replating process. If you are outsourcing this as a service, inspect the replated area per the most recent IPC-A-610 guidelines (Revision G, Section 10.1.1). The bond strength of the plating material can also be measured using the peel tape test found in IPC TM-650. SMT007 Bob Wettermann is the principal of BEST Inc., a contract rework and repair facility in Chicago. Figure 1: Stripping the remnants as part of preparing the contacts for replating. Figure 2: Replating the contact with gold solution.

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