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40 SMT007 MAGAZINE I DECEMBER 2022 rework. A slower ramp rate ensures that the flux is fully activated, thus preventing solder balls from forming. Soldering techs need to be adequately trained in hand soldering and the variables affecting outcomes to reduce the chances of solder ball formation. Training should include adequately reinforcing the correct materi- als, choosing the correct tip as a heat bridge between the lead and the land, maintaining the correct tip temperature, and keeping the soldering tips clean. Inexperienced soldering technicians may feed in too much solder too quickly (See Figure 1). Another area to consider when assessing the likelihood of solder contamination is compo- nent lead contamination. Potential sources of contamination include improper storage of the components, improper MSD controls of the component, and the cleanliness of the tape, tray, or stick the components are stored in. With the proper solder training, or in some cases retraining, soldering technicians can pick up better habits and help diagnose problems as they happen. Reminder of the IPC-A-610 Spec on Solder Balls A refresher is in order on what the inspection standard says about solder balls. Solder balls (IPC-A-610H 5.2.7.1) become a defect when: 1. e presence of a solder ball reduces the distance between the solder ball and another conductive surface to below the minimum electric clearance. 2. e solder ball is not entrapped, encap- sulated, or attached, or can become dis- lodged in the service environment. A sol- der ball rolling around in an electronics enclosure is not acceptable. 3. e solder ball is entrapped in coating or flux residue such that other form, fit, or functions of the electronics assembly can- not be maintained. Removing Solder Balls Solder balls can be removed by several means. For solder balls entrapped in flux res- idue, an orangewood or plastic stick can dis- lodge the solder balls. e challenge is mak- ing sure that solder balls dislodged in this man- ner do not get "lost" in the assembly and cre- ate a future reliability issue. Large solder balls can be removed with a soldering iron, flux, and soldering braid. If entrapped by a conformal coating or other material layer, the coating will need to be removed prior to eliminating the solder balls. While solder balls typically appear in other PCB assembly processes, those formed in hand soldering can be mitigated through a variety of methods including proper flux usage; proper soldering tip and temperature selection; and by keeping the materials in the soldering process free from moisture and contaminants. SMT007 Bob Wettermann is the principal of BEST Inc., a contract rework and repair facility in Chicago. For more information, contact info@solder.net. To read past columns, click here. Figure 3: Too much or "heavy" solder can lead to solder ball formation.