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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