Why it is sometimes necessary to re-seat a board or chip

[Chuck Guzis]

On 30 Dec 2008 at 22:41, dwight elvey wrote:

>  To my knowledge, it is pure gold. It is difficult to plate
> alloys.

Not really that hard, depending on the alloy.  For instance, I can 
plate brass in my own shop--it's not difficult; just an acid bath 
process. (Tin-lead) Solder has been electroplated onto PCBs for 
decades.

Some people have pointed to their college chemistry texts and told me 
definitively that it was impossible to electrodeposit an alloy.  I 
don't know where that one got started.   

I'll agree that cooking up a plating bath can be a black art.  Stuff 
you'd never think would affect the outcome such as sugar sometimes 
winds up in them and I know a retired fellow who ran a plating shop 
who swore that he got better results than anyone else because he 
urinated in his tanks.

From: http://www.pfonline.com/articles/pfd0022.html

Hard, Bright Gold

Platers who gold plate contacts and connectors generally use bright 
acid gold formulations. These baths contain complexed cobalt or 
nickel in small quantities, to improve hardness and brightness of the 
deposit. Such gold electroplates will be 99.7 to 99.9 pct pure, and 
hardness can be 120 to 300 Knoop. The small amount of nickel or 
cobalt will interfere with die bonding, so these baths cannot be used 
for semiconductor plating. Hard, bright gold baths, if operated with 
good housekeeping and chemical control, have very long life-often 
three years and more. 

Cheers,
Chuck