Well put Lee. As I said in the previous email I'm certainly not
knowledgeable about the chemical processes. However, as you are aware
form your two year participation in 1996/1997 on the Bell
Laboratories/Lucent Technologies CFT (cross functional team) the quality
and reliability of the commercially available immersion silver processes
were fully evaluated before production implementation in the fall of
1997. In the past 8 years we haven't had any products field returned
for immersion silver problems. We do not have a preferred immersion
silver chemistry supplier and we leave that choice to the board
fabrication. However, we do have end-point surface finish requirements
we expect our fabricators to meet and we do periodically monitor the
quality of boards. Our board fabricators and their chemistry suppliers
can call it anything they want as long as it meets our end-point
requirement.
Regards,
George
George M. Wenger, Andrew Corporation
Reliability / FMA Engineer
Base Station & Subsystems Group
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
Sent: Friday, May 27, 2005 5:10 PM
To: [log in to unmask]
Subject: Re: [TN] Immersion Silver - Fab notes
Dewey
We have all been down the road before. As George correctly points out
the mechanism for an immersion process is an ionic exchange (which is
also the mechanism for corrosion). Once the surface of the host material
is no longer exposed to the plating solution it passivates and the
process reaches completion. It is difficult to conceive of this being
more than a few micro inches thick and certainly not approaching or
suppressing 10 micro inches.
Obviously more is involved than an immersion process. There are
overtones here of an electroless process which is normally caused by a
catalyst being present. My guess is that both of these processes are
occurring simultaneously, however the suppliers are not commenting on
this apparent contradiction. Trying to classify these coatings will be
difficult until the suppliers explain to some extent what is taking
place. What we now have are "immersion and augmented immersion"
processes. We may want to classify both types under a single inclusive
title such as the one above until the industry is provided some
additional information.
Best regards
Lee
J. L. Parker Ph.D.
JLP Consultants LLC
(804) 779 3389
----- Original Message -----
From: Whittaker, Dewey (AZ75)<mailto:[log in to unmask]>
To: [log in to unmask]<mailto:[log in to unmask]>
Sent: Friday, May 27, 2005 1:04 PM
Subject: Re: [TN] Immersion Silver - Fab notes
As the Lead-Free initiatives take place Immersion Silver is one of the
leading candidates. The word Immersion to me means that the final
thickness
is self-limiting by nature. If this is not the case or the term is not
definitive enough, this must be resolved, because we have more at
stake than
just a tarnished image.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Friday, May 27, 2005 9:52 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] Immersion Silver - Fab notes
Rudy,
If you assume that all immersion silver chemistries in use are
replacement
chemistries than you should expect the silver thickness to be
self-limiting.
However, during our implementation of immersion silver we tested
"immersion
silver" palted boards that had 45u" thick silver as measured by XRF
and also
confirmed by Auger depth profiling and cross sectioning. My
background
isn't chemistry but it appears that some of the immersion silver
chemistries
must have an some auto-catalytic action as well as replacement.
Regards,
George
George M. Wenger
Reliability / FMA Engineer
Base Station and Subsystems Group
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908)
546-4531
[log in to unmask]<mailto:[log in to unmask]>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of R Sedlak
Sent: Friday, May 27, 2005 12:37 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [TN] Immersion Silver - Fab notes
Dave: I have never heard of anyone being able to get over about 12
microinches of Silver, I think the 25 microinch number came from
somebody
trying to build a spec they could meet no matter what.
Remember, Silver is an immersion finish, which means it is
self-limiting,
when all the Copper is covered, plating ceases, no matter what you
do..
Rudy Sedlak
RD Chemical Company
Dave Seymour
<[log in to unmask]<mailto:[log in to unmask]>> wrote:
Gerard,
This is a prelimary run of boards for us. I am just trying to get my
ducks
in a run before going and having the same conversation with our board
supplier.
The first set of numbers came out of table 3-1 in the draft.
Based on your comments, I'll start the conversation in the 8-12 micro
inch
range.
Thanks
dave
Gerard O'Brien wrote:
>Dave - there is only one supplier of the thin Silver and they are now
>offering a thicker silver. Given that, the majority is thick silver.
>25 micro inches on what pad size? Did they follow the 30% rule for
>collimator to pad for XRF measurement? Were they using the correct
>energy level to measure I Ag?
>The 4553 group is actively working to determine the upper limit due
to
>the fears of Ag3Sn IMC's that are known bad actors when it comes to
>solder joint embrittlement. I would suggest having an independent
check
>on their thickness.
>
>Regards
>
>Gerard O'Brien
>Co-chairman 4-14 plating
>
>-----Original Message-----
>From: Dave Seymour [mailto:[log in to unmask]]
>Sent: Friday, May 27, 2005 9:03 AM
>To: [log in to unmask]<mailto:[log in to unmask]>
>Subject: Re: [TN] Immersion Silver - Fab notes
>
>All,
>
>The IPC draft IPC-4553 spec listed below mentions two types of valid
>silver plating.
>Thin 3-5 micro inch and Thick as 8-12 micro inch.
>
>What are board fabricators typically using Thin or Thick?
>
>Also, I saw a presentation from a board shop recently with Silver
>thickness up to 25 micro inch.
>
>It that too thick?
>
>What is too Thick?
>
>Thanks in advance,
>Dave Seymour
>
>
>Gerard O'Brien wrote:
>
>
>
>>There is a new spec that has just completed balloting - IPC-4553.
Ken,
>>you can go the committee home page 4-14 at ipc.org and find a copy
of
>>the
>>
>>
>draft
>
>
>>that will soon be released.
>>
>>Regards
>>
>>
>>Gerard O'Brien
>>Co-chairman 4-14
>>
>>-----Original Message-----
>>From: Ken Patel [mailto:[log in to unmask]]
>>Sent: Wednesday, March 09, 2005 1:51 PM
>>To: [log in to unmask]<mailto:[log in to unmask]>
>>Subject: [TN] Immersion Silver - Fab notes
>>
>>All,
>>What kind of note should I put on fab drawing if I want to use
>>Immersion Silver as my surface finish. Is there any IPC- document
that
>>also I can refer to as part of my note.
>>
>>Any help will be appreciated.
>>
>>re,
>>ken patel
>>
>>
>>
>>
>>__________________________________
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>--
>Dave Seymour, CID+
>Catapult Communications Inc.
>800 Perimeter Park Dr, Suite A
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