To technetters: Several interesting questions and answers about immersion gold on electroless nickel. 1.Solderability: About phosphorus content and solderability----- It has been written many times that the higher the phos the poorer the solderability. However, we did not mention that many electroless nickel bath for electronic use are a nickel-boron type and do not use any phosphorus in make up or as a reduciing agent. The boron electroless nickels are reasonably solderable even with out the immersion gold overplate, but the gold does aid solderability. The palladium overplate also works well with the boron electroless nickels and is perhaps will retain solderability better. 2.Storage life: The question continues to come up as to storage life of immersion gold over nickel. In my experience, I tried to determine if one was better than another, and therefore, used steam aging on the M-coupon as a test vehicle. The result was that the immersion gold is a poor barrier to retain soldrability of the underling nickel in histile environments and that some product even exuded nickel salts after the test. Some product was better than other, but it was not related to thickness. In general the test indicated that the gold is porous and with the most probable presence of residual ionic salts will cause the nickel to react and become very-very-poorly solderable. For best storage results, it is best to bake-dry the boards after processing and keep them dry up until soldering time. Note: a true non-porus immersion gold would only have to be about 4 angstroms thick or about a 1000 time thinner than the 3-8 millionths that we apply Phil Hinton [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************