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solder SnPb wire to gold plated IC

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Sam

#49040

solder SnPb wire to gold plated IC | 13 April, 2007

Anyone experience using SnPb wire to gold plated ICs? I have tried to solder the SnPb wire to the gold plated ICs lead, but the surface finishing is dull. Can anyone explain that to me? Why it is not shinny surface? Any recommendation?

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#49047

solder SnPb wire to gold plated IC | 14 April, 2007

When soldering a component to a board, the solderability protection on the component combines with the solderability protection on the board and the solder to form an alloy. This alloy is unique for that combination of solder and solderability protection of the board and component. It will have a melting point, grain structure, mixture of metals, appearance, and other characteristics unlike other alloys on your board.

In solder, gold: * Gives SnPb solder a more dull and more grainy appearance than some other metals. * Increases the melting point. * Forms a brittle AuSn4 intermetallic phase. If the portion of gold is too high, solder joints can fail along the AuSn4 boundary. So, ANSI/J-STD-001D requires that components with gold plated leads be tinned prior to soldering.

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Sam

#49053

solder SnPb wire to gold plated IC | 15 April, 2007

few more questions: Is there any standard saying that the dull surface is accepted if solder Au plated leads? Understand that more than 3% Au in the solder connection leads to unacceptable embrittlement of the connection. How about any standard related to Au coating on the leads itself? How many micron of coating is acceptable?

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#49057

solder SnPb wire to gold plated IC | 16 April, 2007

Standard for appearance: J-STD-001 and IPC-A-610 committees eliminated the requirement that solder connections be "bright and shiny". Certain solderability protections; such as Au, NiPd, NiPdAu; can affect the surface texture of a solder connection, but have no impact of reliability. Reliance on the appearance of a solder connection as a measure of quality can be a poor assumption.

Standard for plating thickness: No, there is no standard for plating thickness. Again, that's why J-STD-001 requires pretinning of the leads of components with gold leads.

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