So, soldering: In any case I can think of, it creates a continuous metal connection. In our corner of the industry (PCBA), that connection is between the metal pad of a circuit board board and a component. The connection can carry electrical signals or heat, and is also a physical attachment keeping all the pieces held together. However, as with many things, the devil is in the details (or rather, how MANY details there are to consider), and the surface finish is definitely one of those details.
Solder alloys need to work well on all sorts of surfaces - so our tech team has a lot of knowledge in this area. Some types are immersion silver, organic or OSP covered copper, immersion tin (ImSn), and electroplated nickel/gold (ENIG).
This showed up in a big way when we had to plan out testing on our new alloy for thermal cycling reliability - Indalloy®292. Indalloy®292 is a high-reliability alloy for tough thermal cycling conditions, and one of the huge places where that is becoming necessary is the automotive industry. However, since the automotive industry requires such good reliability, making sure the details of the testing match up - like thermal cycling temperature, component types, and surface finish - is important!
We definitely need (and have!) data proving Indalloy®292 reliability on ImSn boards (probably the biggest "player" so to speak, at least in automotive PCBs), but if we want Indalloy®292 to be a representative of high-reliability for decades to come - testing needed to happen on other surfaces. OSP in particular came up in quite a few customer road maps - and that's what I want to touch on. Interest in the wide use of OSP elsewhere and the low cost are still being balanced by other concerns, but from a solder developer and manufacturer, we needed confidence in our material's ability to meet the future of high-reliability needs. And let me just say... our R&D team knocked it out of the park.
We are proud of the data, of Indalloy®292, of our R&D team's work designing and testing the alloy, and of how it stacks up to competitive alloys. However, there is definitely something important to be said for paying attention to and addressing not only the current needs, but those that will be relevant in the future.
Every new variable, whether it is a material or a process, brings new interactions. New interactions bring consequences and impressive possibilities; that's probably why any test DOE inevitably seems to balloon like crazy! But hey, in exchange for that occasional "crazy," what we get is a lot of new great information - like rock solid reliability on OSP.