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76 PCB007 MAGAZINE I MARCH 2019 Engineers must understand the limitations of organic solderability preservatives (OSPs) and how best to optimize the performance of the finish. Paying close attention to equip - ment systems, pH control, and pre-OSP pro- cess steps will help to ensure optimum OSP performance. Introduction Never underestimate the importance of the equipment set-up and the operating parameters for any chemical process, and OSPs are no ex- ception. Complex PCB assembly presents sig- nificant challenges concerning the solderable finish selected. While there are many choices available to assembly engineers and OEMs, some finishes—such as OSPs and ENIG—oc- cupy a significant market share. Even with the significant market acceptance of OSPs, there are many questions related to the finish. These include the performance of the coating under multiple lead-free reflows, solder flow-up, and creep corrosion, among others. In addition, as with all finishes, there are limitations. In this month's column, those limitations will be presented along with a thorough discussion of key equipment and chemical process parameters that influence the performance of the OSP. No one finish will meet all criteria that an end user and assembly company may desire. However, it is critical that the final finish selected meet sev - eral criteria depending on the environment and functionality of the final assembled product. Since electronic products are often grouped according to the end-use environment or ap- plication, it makes sense to gain a thorough understanding of the key attributes that will determine how well that particular finish func- tions. The engineer must consider a number of attributes that will determine which finish is the best fit within the following well-known market segments: • Medical • Aerospace/defense • Computer/office • Consumer/handheld • Telecommunications Optimizing the OSP Process for High Performance, Part 1 Trouble in Your Tank by Michael Carano, RBP CHEMICAL TECHNOLOGY

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