Phil
If most of your product is through hole, you may want to consider an OSP. This will reduce the price of the board in most cases and provide a satisfactory solderability coating. The risk are soldermask on the land and tin oxide. Most high quality board houses have resolved these issue for through hole boards.
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: Phil Nutting<mailto:[log in to unmask]>
To: TechNet E-Mail Forum<mailto:[log in to unmask]> ; Lee parker<mailto:[log in to unmask]>
Sent: Thursday, April 14, 2005 4:02 PM
Subject: RE: [TN] ENIG - no more problems?
Ok, I've been following this whole thread. What I haven't seen is
anybody touting the use of Immersion Tin. We do about 98% of our boards
as through hole. As we transition to RoHS compliant products we will
need to change our board plating. I had thought that Immersion Tin was
the best route. Now I'm confused. I need some fog cutters.
Baffled in Beverly.
Phil Nutting
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
Sent: Thursday, April 14, 2005 3:36 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] ENIG - no more problems?
Frank
I have been involved in the black pad issue since the middle '90s.
I agree with you the occurrence is now much less than eight or nine
years ago; however, other than reducing the gold thickness, I have not
seen any convincing data of the mechanism or the remedy. Most of what I
have experienced are hand waving augments that are void of supporting
data and in most cases conflicting.
You mentioned "we now have a better understanding of the likely causes".
Could you go into some detail both on the likely causes and the
supporting data; other than of course reducing the thickness of the
gold.
Best regards
Lee
J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
----- Original Message -----
From: Frank Kimmey<mailto:[log in to unmask]<mailto:[log in to unmask]>>
To: [log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]>>
Sent: Thursday, April 14, 2005 1:47 PM
Subject: Re: [TN] ENIG - no more problems?
Genny,
I hate to argue with folks like Vladimir, Ed and George
because I truly respect their opinions and knowledge (they are on my
list of who to go to for help).
That said, I also need to tell you about the success of ENIG and IAg
for replacing Pb.
As far as ENIG and Black Pad all the statements of recreating
Black Pad are true (I also have never heard of anyone successfully
causing it on demand). Also true though is the fact that we (the
industry) now has a better understanding of the likely causes and by
following corrected processes have seen a large reduction (to the point
of elimination in some facilities) of the occurrence of Black Pad. I
personally have not had a Black Pad incident in more than 3 years (close
to half of our designs are ENIG).
We spent 2 years trying to qual IAg and found some finishes
better than others (due to thickness of deposit).
The result was only one finish (of the 3 available at the time) was
qualified for use on our product. Unfortunately some of the finishes
resulted in the formation of Cuprous Oxide on the outer surfaces rending
the pads unsolderable. From our approved supplier we have seen NO
solderability issues in the more than a year we have been using IAG.
All rambling aside, we expect to replace Pb HASL with ENIG as
drop in for legacy and use ENIG and IAg for designs going forward.
Bottom line should be if you have good suppliers then you should be able
to confidently make the change from HASL to Pb free finishes.
Hope its helped,
FNK
Frank N Kimmey CID+
Principal PCB Designer
Powerwave Technologies Inc
Office 916-941-3159
Fax 916-941-3195
Cellular 916-804-2491
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Lee parker
Sent: Thursday, April 14, 2005 9:40 AM
To: [log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]>>
Subject: Re: [TN] ENIG - no more problems?
Genny
If the problem with black pad is resolved, then the suppliers should
be able to produce the problem at will and then demonstrate a corrective
action that prevents the issue form occurring without any side effects.
To the best of my knowledge this is not the case.
What has taken place is that most suppliers are now recommending a
gold thickness of two micro inches or less based on imperial data; there
have been few reported cases of black pad when the gold is restricted to
two micro inches or less. Unfortunately, no one has given me a
convincing mechanism to explain the phenomena. Also as the gold
thickness is reduced the probability of soldering issues is increased.
Best regards
Lee
----- Original Message -----
From: Genny
Gibbard<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]>>>
To:
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:Tec<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:Tec>
[log in to unmask]<mailto:[log in to unmask]>>>
Sent: Thursday, April 14, 2005 11:54 AM
Subject: [TN] ENIG - no more problems?
Just listened to a Lead Free presentation by one of our assembly
materials
suppliers. They tested different pastes on different board finishes
using a
variety of different patterns, spacings, aperture sizes, etc,...
By far and away, ENIG was the best finish for performance, for
wetting,
defects, voiding, ...
The guy making the presentation said that he felt a lot of the
initial
concerns re ENIG - black pad being the biggest - have been resolved,
and
that they are no longer a concern, that they have determined what
the cause
of it is and eliminated it. Anyone want to comment on that? I'm
not sure
if he is correct, or just out of the loop.
It was interesting as well: ImmAg got a very bad rating from them
in
performance, even though many on this forum really praise that
finish. It
exhibited dewetting (they printed solderpaste pads on an area with
no
soldermask, and the solder did not stay and spread where it was
printed, it
crept together with other pads into a big blob, like you might see a
water
drop do) and the amount of voiding was impressive!!
About 4 years ago I joined this forum, and one of the reasons was
because I
was looking for info on ENIG. We had done a prototype run of a
couple of
boards and they failed miserably. They were never analyzed in
depth, so it
wasn't figured out what exactly caused the failure. It was the
excuse we
needed to not choose this finish and some of the extra costs
associated with
it.
However, with the Pbfree push now, I don't know if we should
re-examine
whether to use the finish. For products where we needed a flat
finish, we
have gone to ImmSn, but we still use HASL wherever possible.
Genny
"Genius may have its limitations, but stupidity is not thus
handicapped"
Elbert Hubbard
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