Hey Dan,
I have seen this phenomenon more times than I like.
There are a few more questions prior to reaching root cause.
Talk to your supplier and see if:

1. Are nonplated holes done as second operation or are they "poisoned" to stop electroless Cu from adhering.
If "poisoning" is done, then you likely are seeing Immersion gold adhering to contamination and/or fibers within the nonplated hole surface. I do not reject for this, but do notify my suppliers they have issue and in small amounts I consider this a process indicator.

2. What is process flow? How does it differ from your other suppliers.

3. When was ENIG maintenance preformed (before and after) in relationship to date code of build? Possibly a contaminated bath within the process.


The majority of the times I have seen this phenomenon it was caused by weak and/or poorly applied "poison" solution used with drilling all holes in same primary drill process (no secondary drill in process flow). 
Finally, discuss with your supplier and let them know this is one of those things you just don't want to see. They can then make sure this process indicator is watched and maintained in house for a better product to you.
Hope this has helped.
Call me if you want to discuss further.
FNK

Frank N Kimmey CID+
Principle PCB Designer
Powerwave Technologies
EDH 916-941-3159
FAX 916-941-3195
CEL 916-804-2491


-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Thursday, February 05, 2004 7:13 AM
To: [log in to unmask]
Subject: [TN] Goldresidues in non-plated holes


Hi Technet,

I looked at an ENIG board today and noticed it had some gold-residues
in the nonplated holes.
I always thought that a non-plated hole should not have any plating at
all, but seeing this condition for the second time (the first time was
on a board from another manufacturer and another designer) I almost
begin to think this is a normal condition.
What do you think, is this normal, is it acceptable (I don't think so),
any idea what causes it ? For those who like to see a photograph of
this, see: http://www.smtinfo.net/forum/index.php?showtopic=40

Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net

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