Mike, I'm glad you have a supplier willing to do selective electroplate for
anything other than gold edge contacts, and I'm happy that you have
customers who are willing to pay the extra for your equipment because of
more expensively processed bare boards. Yes, it is possible to do selective
electroplate of features, but it adds to the processing (more lamination and
print steps), increases the risk of failure (etching problems due to
different metal electron levels), and is NOT designed for manufacture. I
used to make a very large complex 26 layer board with 3 mil buried cores, 4
mil line and space everywhere, 6 mil holes, laser vias 1 - 3, ZBC layers,
and multiple impedances on  many layers, yet the thing that blew our yields
was the selective electroplated nickel gold areas for LGA components.

Dougal Stewart

email:  [log in to unmask]
phone: +44 1896 822204
mob:    +44 7984 629667
www.pwbsolutions.co.uk
----- Original Message -----
From: "Barmuta, Mike" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, June 24, 2003 9:23 PM
Subject: Re: [TN] (2) [TN] Electro-Plated Ni/Pd/Au vs [ENIG]


> Hi Chris: Sorry but I have to disagree with you regarding hard gold "
> requiring the ENTIRE board be plated with gold". It does not require the
> complete outerlayer circuitry to be plated with gold.
> Selective electroplated hard gold is fairly common. It can be done either
> before or after copper pattern plate. The rest of the  exposed copper
> pattern plate circuitry use whatever the normal etch resist plating is,
> typically tin. The key is in how you design the plating resist layers and
> the interface between then gold and copper features.
>
> Then of course there is bussed gold plate usually done with gold
> tips/fingers.
>
> We build several thousand boards a week thru our PCA processes using
> selective hard gold.
>
>
> Just out of curiosity why are you removing the gold from your surface
mount
> pads? Is it too thick for reliable solder joints due to a thickness
> requirement you have? If so you can actually do a double gold where SM
pads
> get one thickness and other features have a heavier deposit for things
like
> rotary switches.
>
>
> Regards
>
> Michael Barmuta
>
> Staff Engineer
>
> Fluke Corp.
>
> Everett WA
>
> 425-446-6076
>
>
>
> -----Original Message-----
> From: Chris Robertson [mailto:[log in to unmask]]
> Sent: Tuesday, June 24, 2003 12:36 PM
> To: [log in to unmask]
> Subject: Re: [TN] Electro-Plated Ni/Pd/Au vs [ENIG]
>
>
> Scott,
> There a few versions of the gold plating. Hard gold requires the ENTIRE
> board be plated with gold. Some are reportedly capable of doing this
> selectively, but since the gold is used as an etch resist, it really is
> difficult.
>
> The problem we encounter is we must remove the gold from all surface mount
> pads (not through hole) before soldering. A very time consuming process.
I'm
> not familiar with the ENIG (or I just don't recognize it)
> I'm not sure what palladium get you in the mix.
> Gold is a great antioxidizing metal (what it is used for in this case) and
> has a long shelf life unlike entek and some other coatings. The nickel is
> for hardness. If you do use/change to this, ask the forum about the mix.
> There are some common ratios for nickel/gold. I personally don't have one
> that includes Pd.
>
> Chris Robertson
> Design Engineer
> Lockheed-Martin Technology Services
> 4912 Research Dr.
> Huntsville, AL 35805
> (256) 722-2626
> [log in to unmask] <mailto:[log in to unmask]>
>
>
> I have a new board shop promoting their Electro-Plated Ni/Pd/Au (hard or
> soft gold) surface finish over our existing [ENIG] boards.  We have not
had
> any issues with our current assemblies using [ENIG].  I am requesting any
> advice or information on Electro-Plated Ni/Pd/Au and if it would be worth
> switching to it.  Any advice would be greatly appreciated, thank you in
> advance.
>
>
>
> SCOTT
>
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