Nature's first green is gold,
Her hardest hue to hold.
Her early leaf's a flower;
But only so an hour.
Then leaf subsides to leaf.
So Eden sank to grief,
So dawn goes down to day.
Nothing gold can stay.

Inge



----- Original Message -----
From: "John Burke" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, October 16, 2006 7:07 PM
Subject: Re: [TN] Suspect PCBs


> Looks like gold, feels like gold, sounds like gold when running the
> fingers
> through large heaps of coin........Ahhhhhhhhhhhhhhh
>
> Oooops sorry,
>
> Got carried away there............8-)
>
> Late Friday moment,
>
> John
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
> Sent: Monday, October 16, 2006 10:01 AM
> To: [log in to unmask]
> Subject: Re: [TN] Suspect PCBs
>
> reminds of a problem we had once: there was no nickel at all under the
> gold,
> XRF or EDAX will tell you. Also, we have seen 'dull gold' from a chinese
> supplier. In that case there was nearly no gold present, so what we saw
> was
> nickel. Again, agree with the others, don't wait, make a XRF or EDAX.
> Wouldn't listen to the explanations given, gold is gold, and should look
> like gold. Amen.
> Inge
>
>
>
> ----- Original Message -----
> From: "Tom Parkinson" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Monday, October 16, 2006 3:47 PM
> Subject: [TN] Suspect PCBs
>
>
> Hello All (DN & TN),
>
> I'm having a disagreement with one of my board vendors.  We have rejected
> some of the boards for "suspect bad pads" (ENIG).  During visual
> inspection,
> the suspect pads 'jump out' at you by looking dark in color.  At the very
> least, they sure refract the light the wrong way making them look dark in
> color. Rotating the board does not make them look better.
>
> In the past we have tried soldering to these pads and have run into
> problems
> with wetting.  In my letter to the vendor, I mentioned the ENIG was either
> too thick, or too thin, both which will cause problems.
>
> I'm especially worried about these when they are under BGAs.
>
> The vendor says there is nothing wrong with the pads as-is.  In fact he
> said
> the following:
>
> =========================
> "Boards are good.  There is no black Pad - only dull gold.  Xxxxxx (board
> vendor) is "Cleaning" the gold to make it look "Pretty".  We will be
> returning the boards on Monday to you.
>
> There is always a variation in surface color with any immersion gold
> process. It may be minimal in some cases or more obvious as in the boards
> in
> question. But problem is not the correct description, variation is the
> correct term. It will not effect form fit or function.
>
> The color variation you refer to is not because of the variation in
> thickness. Three to seven micro-inches of gold is deposited over 100 to
> 150
> micro-inches of nickel. The gold vaporizes during your reflow process and
> the adhesion is solder to nickel. There will be no adherence problem. By
> the
> same token, there is no embrittlement problem with immersion gold as there
> would be with electro-plated gold. For one thing electro-plated gold is 10
> times thicker than immersion gold. Secondly the grain structure of
> immersion
> gold and electro-plated gold is very different. Electro-plated gold having
> a
> long grain structure in comparison to immersion gold.
>
> Using a pencil eraser as you suggest only proves my point. The surface
> color
> variation is caused by an alkaline deposit on the surface of the gold
> which
> vaporizes on contact with molten solder. We propose to clean the boards
> using a mild baking soda solution."
> ==========================
>
> Looking forward to your inputs.
>
> Thanks,
>
> Tom
>
>
>
> Tom Parkinson
> Quality System Manager - CIT
> WinTronics, Inc.
> Phone: 724-981-5770 - extension 235
>
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