I remember having a boss who had on his a desk this quote:
"It is not enough to write so we can be understood. We must write so
that we cannot possibly be misunderstood."
I was never able to write one sentence in my audit reports without him
bleeding all over it. This was back before we used computers to write
reports. They were all done a typewriter.
I found this searching for that quote:
SHOES ARE REQUIRED TO EAT IN THIS CAFETERIA.
Below it, someone had written:
Socks can eat wherever they want to.
I rest my case.
Jon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Thursday, July 08, 2010 7:51 AM
To: [log in to unmask]
Subject: Re: [TN] Underfill as a Remedy for Electro Migration?
Your writing skills are not much better than your reading skills (no
reflow?) - Go get a Diet Mt. Dew asap!
To clarify, we applied the conformal coating materials to the test
vehicles after reflow processing and injected the material under the
BGAs
creating a worst case situation.
Dave Hillman
Rockwell Collins
[log in to unmask]
Douglas Pauls <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
07/08/2010 07:45 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
[log in to unmask]
To
[log in to unmask]
cc
Subject
Re: [TN] Underfill as a Remedy for Electro Migration?
I gotta learn to start reading closer. I read it as conformal coating
as
an underfill. My mistake.
The study that we did was on fully assembled test boards, no reflow.
The
thermal cycling we used was 2000 cycles between -55C and +125C, 15
minutes
at each extreme, 8-10C/min ramp rates. A fairly common profile for
aerospace.
Doug Pauls
Leif Erik Laerum <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
07/08/2010 07:38 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Leif Erik Laerum <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] Underfill as a Remedy for Electro Migration?
Doug,
Thank you for your input and the pictures. Just to clarify, conformal
coating was never intended to be applied AS underfill. The NASA paper
suggested EITHER underfill or conformal coating.
In your experiment did you apply conformal coating before reflow? Or was
the coating applied after reflow and injected under BGAs. Are you
saying if you need to conformal coat a board, you first need underfill
material to prevent the conformal coating to damage the BGA?
Leif Erik Laerum
Quality Assurance Manager
Texas Memory Systems
[log in to unmask]
Tel: (713) 266-3200 x468
www.texmemsys.com
On 7/8/2010 7:01 AM, [log in to unmask] wrote:
> Good morning Leif,
>
> Conformal coating as an underfill material is a really, Really, REALLY
bad
> idea. The primary problem is the coefficient of thermal expansion.
In
> thermal cycling, there is enough strength to pop BGAs right off a
board.
> Dave Hillman and I did a study a few years ago where we intentionally
did
> what you suggest. I will post some pictures on the newfangled Technet
> picture site of what happens. The one part solvent based acrylic we
used
> on one set had a 73% failure rate. The water-based acrylic we used
did
> fine, but it had a lower CTE value. I would expect silicones to be
much
> worse, due to their CTE.
>
> Second, you have the problem of solvent entrapment under parts. That
> solvent has to get out somehow. If you wait to let it diffuse out
slowly,
> you have horrendously long process times. If you try to force it out,
you
> get bubbles and voids. May be a little different if you are using a
> 2-part coating or a 100% solids coating for this second aspect.
>
> Loctite has a pretty good line of underfill material and we use and
have
> evaluated several. Which one you pick depends on whether you need
your
> assemblies reworkable or not.
>
> Doug Pauls
>
>
>
> Leif Laerum<[log in to unmask]>
> Sent by: TechNet<[log in to unmask]>
> 07/07/2010 05:11 PM
> Please respond to
> TechNet E-Mail Forum<[log in to unmask]>; Please respond to
> Leif Laerum<[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> [TN] Underfill as a Remedy for Electro Migration?
>
>
>
>
>
>
> Technetters,
>
> We have identified electromigration as the root cause of some field
> failures we have been seeing. During the troubleshooting we came
across
> the following NASA paper. All of the details of this paper fits our
> situation perfectly. We use the same package as described.
>
> http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40854/1/08-23.pdf
>
> The executive summary is that the silver in the epoxy used to attach
as
> die attach migrated to create a short. The migration was triggered by
> humidity.
>
> The paper suggests using underfill or conformal coating to remedy the
> problem. Currently we do not use either in our process. I have some
> questions regarding these:
>
> - What are the pros and cons using either of these for this particular
> purpose? IMO underfill seems the best solution for us.
> - Does anyone have any experience as to whether this is a good
solution?
I
> am not quite understanding the "chemistry" here.
> - Does anyone have a recommendation as to what type of underfill would
> work well for this application?
>
> Thank you for your input.
>
>
>
> --
> Leif Erik Laerum
>
>
>
> CONFIDENTIALITY NOTICE: This email and any attachments are Texas
Memory
> Systems' proprietary material for the exclusive and confidential use
of
> the intended recipient. If you are not the intended recipient, please
do
> not read, distribute or take action in reliance upon this message. Any
> unauthorized disclosure is prohibited. If you have received this in
> error, please notify us immediately by return email and promptly
delete
> all copies of this message and its attachments from your computer
system.
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or
[log in to unmask]
> ______________________________________________________________________
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> 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
> -----------------------------------------------------
>
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or
[log in to unmask]
> ______________________________________________________________________
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> 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
> -----------------------------------------------------
>
CONFIDENTIALITY NOTICE: This email and any attachments are Texas Memory
Systems' proprietary material for the exclusive and confidential use of
the intended recipient. If you are not the intended recipient, please
do
not read, distribute or take action in reliance upon this message. Any
unauthorized disclosure is prohibited. If you have received this in
error, please notify us immediately by return email and promptly delete
all copies of this message and its attachments from your computer
system.
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or
[log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or
[log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or
[log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
This communication is intended only for use by the addressee(s) named herein and may contain business confidential and/or legally privileged information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution, disclosure or copying of this e-mail and its contents is strictly prohibited. If you have received this e-mail in error, kindly notify the sender by replying to this message. In addition, please permanently delete the message and any attachments without copying or disclosing the contents. Thank you for your cooperation.
THIS DOCUMENT AND/OR SHIPMENT MAY CONTAIN COMMODITY ITEMS, SOFTWARE OR TECHNICAL DATA THAT IS CONTROLLED BY U.S. EXPORT LAW, AND MAY NOT BE EXPORTED OUTSIDE THE UNITED STATES OR TO NON U.S. PERSONS WITHOUT THE APPROPRIATE EXPORT LICENSE FROM EITHER THE U.S. DEPARTMENT OF STATE OR DEPARTMENT OF COMMERCE.
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
-----------------------------------------------------
|
