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OSP degradation



OSP degradation | 17 July, 2002

Hello all, I have a question about OSP. The solder mask over traces leading to SMT pads, in some instances, does not cover all the way to the pad. Of course the stencil apertures do not include traces. After the SMT and reflow process, there is visible copper between the pad, and the beginning of the trace. After the OSP has degraded, this area will eventually oxidize. Is this a concern? Will this shorten the products life?

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OSP degradation | 17 July, 2002

The thing I hate the most about OSP, the ugly copper shadows, is similar to what you�re talking about. �Copper shadows� are the copper outline around soldered pads on OSP boards that remain after soldering. They are an artifact of pinching aperture sizes from pads sizes. Yano, you do everything correct; good print, placement, and reflow, nice smooth solder connection, bla bla bla, ladeda; and nobody sees nuttin �cept the stupid ring of copper around the pad.

Huh? Where was I?

Oh. The term we�re looking for is �exposed basis metal�. A-610, 6.5.2 - Exposed Basis Metal, basically says that it�s acceptable, if it�s supposed to be that way. [In your case: it�s supposed to be that way, if that�s the way the board was designed.] This begs the question of: Is it REALLY supposed to be that way or did it just end-up being that way? Which leads us to your main question => Is it OK?

�Is it OK?� => We have no earthly idea if this will shorten the life of your product. We don�t know your product from a shoebox. ;-) Seriously, exposed basis metal could have a variety of effects, depending on the product design and end-use.

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