TECHNET Archives

April 2005

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 15 Apr 2005 07:26:00 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (320 lines)
Hi Phil! Which immersion finish is the best" I'll steal Sir Doug's line "it
depends"! We have had a number of internal discussions on which of the
immersion finishes should be "preferred". The final conclusion we reached
is that a pwb designer should have all three in his or her tool box.
Immersion tin is low cost, metallurgically matched to tin/lead but quickly
oxidizes, has poor thermal exposure robustness and can have tin whiskers
issues when improperly produced. Immersion silver has great RF signal
characteristics, good thermal exposure characteristics but has corrosion
issues under specific use environments (sulfur loaded) and has specific
storage requirements. Immersion gold/electroless nickel has great shelf
life, handling characteristics, and is widely available but can have "black
pad" issues and soldering to nickel can be problematic. All of the finishes
have some warts and you need to understand that all immersion tin's or all
immersion silver's are not equal -e.g. I have seen some immersion tin that
whiskers and some that doesn't.  All three immersion finishes are being
used in High Performance use environments successfully. The new IPC
immersion finish specifications (IPC-4552,4553,4554)  will be helpful in
getting industry consistency on immersion finishes.

Dave Hillman
Rockwell Collins
[log in to unmask]



             Phil Nutting
             <PNutting@KAISERS
             YSTEMS.COM>                                                To
             Sent by: TechNet          [log in to unmask]
             <[log in to unmask]>                                          cc

                                                                   Subject
             04/14/2005 03:02          Re: [TN] ENIG - no more problems?
             PM


             Please respond to
              TechNet E-Mail
                   Forum
             <[log in to unmask]>
             ; Please respond
                    to
               Phil Nutting
             <PNutting@KAISERS
                YSTEMS.COM>






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]
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]>
  To: [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]>
  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]>>
    To:
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:Tec
[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

    ---------------------------------------------------
    Technet Mail List provided as a service by IPC using LISTSERV 1.8e
    To unsubscribe, send a message to
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:
[log in to unmask]>> with following text in
    the BODY (NOT the subject field): SIGNOFF Technet
    To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:
[log in to unmask]>>: SET Technet NOMAIL or (MAIL)
    To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:
[log in to unmask]>>: SET Technet Digest
    Search the archives of previous posts at:
http://listserv.ipc.org/archives<http://listserv.ipc.org/archives<http:/
/listserv.ipc.org/archives<http://listserv.ipc.org/archives>>
    Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/cont
entpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.
16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16>> for additional
information, or contact Keach Sasamori at
[log in to unmask]<mailto:[log in to unmask]<mailto:[log in to unmask]<mailto:sasako
@ipc.org>> or 847-615-7100 ext.2815
    -----------------------------------------------------

  ---------------------------------------------------
  Technet Mail List provided as a service by IPC using LISTSERV 1.8e
  To unsubscribe, send a message to
[log in to unmask]<mailto:[log in to unmask]> with following text in
  the BODY (NOT the subject field): SIGNOFF Technet
  To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]<mailto:[log in to unmask]>: SET Technet NOMAIL or (MAIL)
  To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]<mailto:[log in to unmask]>: SET Technet Digest
  Search the archives of previous posts at:
http://listserv.ipc.org/archives<http://listserv.ipc.org/archives>
  Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/cont
entpage.asp?Pageid=4.3.16> for additional information, or contact Keach
Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100
ext.2815
  -----------------------------------------------------

  ---------------------------------------------------
  Technet Mail List provided as a service by IPC using LISTSERV 1.8e
  To unsubscribe, send a message to
[log in to unmask]<mailto:[log in to unmask]> with following text in
  the BODY (NOT the subject field): SIGNOFF Technet
  To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]<mailto:[log in to unmask]>: SET Technet NOMAIL or (MAIL)
  To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]<mailto:[log in to unmask]>: SET Technet Digest
  Search the archives of previous posts at:
http://listserv.ipc.org/archives<http://listserv.ipc.org/archives>
  Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/cont
entpage.asp?Pageid=4.3.16> for additional information, or contact Keach
Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100
ext.2815
  -----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text
in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2