Hi all, need some professional backup regarding MIL quality boards.

Objects: FR-4 Class III double-sided multi-layer boards, populated with SOICS, BGAs,and a lot of passive components.

Observation 1 : the non soldered board have lots of Tin whiskers on inside of the PTH barrel. My thought is this: if whiskers can grow long before the board is assembled, then ain't it likely that even CAF can be generated?  See photo 1.

Observation 2:  Copper has somehow penetrated the solder mask. This can be found everywhere along the conductor traces. You need a very good light microscope and a SEM to see it. See photo 2.

Board data: Copper with 0.8 micrometer Immersion Tin. No nickel barrier. Solder mask thickness not specified.

Application: Typical MIL-883 environment

Q1: What is your opinion about that thin Tin directly on copper? I dislike the concept. Copper is very mobile at high temperatures, and combined with humidity, there can be leakage currents and corrosion issues. Even if the boards are CCd, there is a risk with copper .

Q2: I gave  the advice to introduce a nickel barrier, but our customer claimed, that they can't because of pressfit connectors and pressfit test pins on the board. Furthermore, they had heard that one cannot have nickel platings when pressfitting, because the nickel will crack and oxidize and cause electrical disfunction. Is this your opinion too? Are there any relevant testing behind such statements?

Thanks in advance

Inge

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