![]() ![]() In most cases the solder paste determines the reflow profile used. Fritz has published over a dozen papers at various industry conferences. Design of Experiments (DoE) techniques have been an area of independent study. Fritz's educational background is in mechanical engineering with an emphasis on materials science. If the process is currently well-optimized for the paste and the assemblies being processed, it is quite possible that no changes will be required.įritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Those are the main impacts that switching surface finish can have on the reflow process. You may find that minimizing peak temperatures and liquidus times helps to preserve solderability through multiple soldering processes. You potentially could need to introduce nitrogen to the reflow process to enhance wetting (though this is uncommon most modern paste flux formulations provide good wetting in air). You may find that you need to tweak the profile to re-optimize the transition from soak to spike in order to manage thermal gradients more effectively, to minimize shifting/skewing of discretes. All that said, back to your original question does any of this impact the reflow profile? The answer is, very possibly yes. ![]() double reflow and subsequent TH soldering, then you should carefully consider what non-fusible finish will provide the best solderability retention through the entire process.įinally, when choosing a non-fusible finish, be sure to consider packaging and storage requirements to ensure solderability on the line. If your assemblies require multiple soldering processes, e.g. On the positive side, non-fusible (flat) finishes will typically enable more robust printing processes. You are also changing the total solder volume by eliminating the SnPb HASL finish, which can have a visible impact for some joints, particularly those on fine-pitch leaded components. You may see more skewing or movement of small discrete components due to differences in the timing of wetting, which can be greater on the non-fusible finishes. ![]() Most likely, you will see slightly higher wetting angles and less spread, which may cause questions from inspectors who are not used to these finishes. The wetting behavior of the new finish will be different. The big change is the move from the fusible SnPb HASL finish to a non-fusible surface finish since you cannot use SnPb solder with a Pb-Free HASL finish, the move to a non-fusible finish is a requirement. Kaminsky has 30+ years of circuit board soldering assembly experience along with a patent for wave solder VOC flux process. ![]()
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