hybrid solder joints

I am seeing reflow around my signal pins after being subjected to a profile of 204c for 1 minute and 225c for a min of 30 seconds. Signal pins are soldered into a copper plated alum. case with SB5 and then silver plated. The pins have a hot oil tin finish. Can the finish (tin) on the pin migrate into the Sb5 and form a hybrid joint and if it does how will this effect the melting point of the joint? If this does lower the temp of reflow what finish would be recommended for these high temp profiles?

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| I am seeing reflow around my signal pins after being subjected | to a profile of 204c for 1 minute and 225c for a min of 30 seconds. Signal pins are soldered into a copper plated alum. case with SB5 and then silver plated. The pins have a hot oil tin finish. Can the finish (tin) on the pin migrate into the Sb5 and form a hybrid joint and if it does how will this effect the melting point of the joint? If this does lower the temp of reflow what finish would be recommended for these high temp profiles? | I am assuming the Sb is Antimony which alone has a melting temp of 630 degrees C. However, when it is mixed with Tin to make an alloy such as Sn95/Sb05, the melting temperature of the alloy is lowered to a range of 232-240 degrees C. I think, and it is only my 2 cents, that if you used a pin with some lead in it ( such as a 90/10 finish ) the resulting alloy if any migration occurs should get you to at least 260 degrees C. I would call a solder company or metallurgist to confirm. Good Luck.

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