Gary-
The bottom line is that electrical solder is not a reasonable load
bearing material. You can relieve the stress in the joints by reflowing
the connections after attaching the heatsink. IF the pins aren't long
enough to make that work, then re-think your mounting, because there is
no way that it will be reliable with the joints under stress, even if
there is no additional environmental stress placed on the system.
Wayne Thayer
>>> [log in to unmask] 2/1/2007 3:51:03 pm >>>
Steve,
This is side view of the module with the broken pin. There is a
heatsink
above approximately 0.100 thick with 4 screws pulling the DC/DC
converter upward away from the circuit board. I do not want to place
any
solder joints under load wither it be clamping or pulling forces.
Thanks,
Gary Bremer
Senior Manufacturing Engineer, CIT
Phone: 257-4430 extension 2170
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, February 01, 2007 9:35 AM
To: [log in to unmask]
Subject: Re: [TN] Mechanical Stress on solder joints
Hi Gary!
I have your picture posted. It's at:
http://stevezeva.homestead.com/files/Broken_Pin.jpg
It sure looks like something has pulled or stressed that pin. I'm
trying
to visualize the heatsink, but I can't form a mental picture of it, so
I
can't say for sure if it was the heatsink or not. But from your
description, it seems pretty probable that the stress that you
describe
damaged that pin.
-Steve Gregory-
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bremer, Gary
Sent: Thursday, February 01, 2007 10:02 AM
To: [log in to unmask]
Subject: [TN] Mechanical Stress on solder joints
Gentlemen,
I have a device that failed in the field, the part is a DC/DC
converter
that is first soldered to the circuit board then a massive heatsink is
screwed to the converter pulling the device upward because of an air
gap
not covered by a thermal conductive pad. Could this be the cause of
damage to the component pins as shown in the attached photo? The
solder
used is Sn63 on the circuit board side and the mass of the board
solder
joint appears to be twice that of the component.
Gary Bremer
Senior Manufacturing Engineer, CIT
Curtiss-Wright Controls Inc.
Embedded Computing -Subsystem
28965 Avenue Penn
Santa Clarita, CA 91355-4185
Main: 661.257.4430 extension 2170
Fax: 661.257.4782
e-mail: [log in to unmask]
Web: www.cwcembedded.com
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______________________________________________________________________
<<Failed Module.bmp>> <<heatsink.jpg>>
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