>Date: Fri, 12 Jul 1996 10:10:04
>To: [log in to unmask] (APeder01)
>From: David Arivett <[log in to unmask]>
>Subject: Re: FAB: Electroless Nickel - Immersion Gold
>
>We have been producing bare boards with electroless nickel immersion gold
for about 2 years now and most customers are pleased with the solderability
results. To answer some of your direct questions, no, electroless gold is
not the same as immersion gold. Electroless gold requires a catalyst. The
gold plates on the catalyst layer and continues to plate until you reach
your desired thickness (this is a good process for gold wire bond).
Immersion gold is a "replacement" process where nickel is being removed and
is relaced by gold. This self-limits at about 8 microinches when the gold
layer effectivly becomes a barrier preventing additional contact with the
nickel layer.
>Again speaking from reports from our customers, solderability has been good
at five to eight microinches. One word of caution though. I have heard
reports where there have been some problems with solder coming over the knee
of the hole for your mixed-technology product. Maybe someone else out there
has had this problem. (It might be a myth, I heard it from people selling
other surface finishes). If you want to discuss this further feel free to
call me.
>
>David Arivett
>Cuplex Inc.
>214 487-2609
>
> At 09:55 AM 7/12/96 -0400, you wrote:
>>     My company is in the process of evaluating the use of Electroless 
>>     Nickel - Immersion Gold as a finish, for both SMT and mixed technology 
>>     PWBs.  Is this a good plating system to evaluate??  Is there any 
>>     "conventional wisdom" that we're missing?
>>     
>>     Secondly, some questions about the gold deposition.
>>     1. Is "electroless gold" the same as "immersion gold?"
>>     2. How thick can we expect the gold to deposit?
>>     3. Is the gold deposition process a self limiting one?
>>     4. How much gold is required to adequately keep the nickel solderable?
>>     
>>     Any other comments regarding this topic is appreciated.
>>
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>

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