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December 2004

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Subject:
From:
Leo Higgins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Leo Higgins <[log in to unmask]>
Date:
Thu, 16 Dec 2004 10:52:58 -0800
Content-Type:
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text/plain (156 lines)
Moisture Stress Level.  Detailed in JEDEC spec J-STD-020C.


Best regards,
Leo

Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704

ph     512-383-4593
fx      512-383-1590
[log in to unmask]
www.asat.com


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-----Original Message-----
From: Judy Rae Brown [mailto:[log in to unmask]]
Sent: Thursday, December 16, 2004 12:59 PM
To: [log in to unmask]
Subject: Re: [TN] Thermal Stress on Components


What is MSL?

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Leo Higgins
Sent: Thursday, December 16, 2004 10:38 AM
To: [log in to unmask]
Subject: Re: [TN] Thermal Stress on Components


I have had experiences where rework caused failure of a functioning
component that was intended to be re-surface mounted.  The cause was failure
to bake the board to meet the MSL level of the device to be removed and
remounted.  Also it is still very common for rework thermal profiles to much
more severe than a typical SMT reflow profile, so even if the board is baked
out to meet the MSL requirements of the package, rework can destroy a good
device.


Best regards,
Leo

Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704

ph     512-383-4593
fx      512-383-1590
[log in to unmask]
www.asat.com


The information contained in this electronic message is CUSTOMER/SUPPLIER
PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the
individual or entity named above. If the reader of this message is not the
intended recipient, you are hereby notified that any dissemination,
distribution and copying of this communication is strictly prohibited. If
you have received this communication in error, please immediately notify the
sender by electronic mail. Thank you.



-----Original Message-----
From: Kasprzak, Bill (sys) USX [mailto:[log in to unmask]]
Sent: Thursday, December 16, 2004 10:23 AM
To: [log in to unmask]
Subject: [TN] Thermal Stress on Components


I was just wondering if any studies have ever been made that analyzed
whether normal rework of a component on a PC board could thermally damage a
component.

A hypothetical case, let's say during the process of wavesoldering, a part,
whether it be a resistor, cap or DIP was lifted to the extent that a rework
was necessary to seat part against the board. The normal course of rework
would be to remove solder from the holes, allow the part to be removed, then
resolder the part.

I'm thinking that most of the responses will have concerns about the board
de to rework more than concern for the part itself.

My concern is thermal damage to the part. Assume that the part has been
pre-tinned at a solder pot followed by installation and wavesoldering.

Anyone have a take on this? Thanks.

Bill Kasprzak
Moog Inc., Systems Group, Process Engineer

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