Repairing IC pins

Dwight> ... I have a number of RAM IC that are Dwight> gradually failing because they have the iron cored pins. I Dwight> guess these were cheaper ... Probably not. Chances are the pin is actually made of Kovar or some other oddball alloy like that. Those aren't cheap at all. Their purpose in life is to match the thermal coefficient of expansion of the ceramic, so fast temperature cycles don't break the hermetic seal. This came out of vacuum tube technology, but it applies to hermetic semiconductors, too. I don't believe that Kovar can be soldered, but it probably can be brazed (with nickel?). Copper would work quite poorly in that application, because the t.c.e. of copper is far higher than that of any glass or ceramic. There are ways around that (see John Strong, "Procedures in Experimental Physics", a brilliant book) but they aren't all that appropriate for IC packaging. paul