From bitter experience I can say that there definitely are handling and
storage issues with ENIG -and although we have never seen the notorious
"black pad", we have had multiple instances of batches with different
solderability issues due to poor rinsing, poor drying, underdeveloped
resist, and copper contamination of the ENIG bath.
Also I'm told that ENIG plating chemistries sometimes use Cd as a
stabiliser in a proportion which may make the ENIG deposit non-compliant
with RoHS - check carefully with your PCB supplier that they can
guarantee the ENIG they offer really is RoHS compliant.
Imm Sn seems to be OK, but when we tried it a few years ago as an
alternate to get around problems with ENIG we found it does not hold up
under multiple rework cycles.
Imm Ag is something we are trialling now and seems to be working out
nicely so far.
I understand OSP works very well with Pb-free providing shelf-life is
not an issue for you, ie you use lots of PCBs and use them quickly.
I'm no metallurgist but if we are joining PCB copper traces with SAC
solder to (most-commonly) Sn-based component lead finishes, then having
a PCB finish using Sn, Ag or Cu seems to make more sense than adding in
"foreigners" like Au and Ni
-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]]
Sent: 28 July 2005 14:04
Subject: Re: RoHs board surface recommendations.
And ENIG has no handling and storage issues like Immersion Silver and
Immersion Tin.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Edwin Louis
Sent: Thursday, July 28, 2005 8:49 AM
To: [log in to unmask]
Subject: Re: [TN] RoHs board surface recommendations.
If you are talking about PWB metallization, I would recommend ENIG. It
is compatible with both Tin/Lead and Lead-free.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barry Gallegos
Sent: Thursday, July 28, 2005 8:27 AM
To: [log in to unmask]
Subject: [TN] RoHs board surface recommendations.
Good Day TecNetters.
Does anybody out there have Board surface recommendations for a RoHs
process ?
A matrix would be preferred. I don't seem to recall seeing any such type
of document or discussions on TechNet so any help would be greatly
appreciated.
Barry
Western Electronics.
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