TECHNET Archives

June 2003

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Subject:
From:
Mike Fenner <[log in to unmask]>
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Date:
Fri, 20 Jun 2003 16:51:24 +0100
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If you are describing a simple butt joint [vertical wall to horizontal pad],
this is indeed a low strength configuration and text book no no.

Mechanical Solder joints should have maximum bond area to minimise stress in
a given joint. Whether the joint is strong enough in absolute terms will
depend on its size, rate and type of stress, service environment and so on.

Solders are weakest in peel, then usually sheer with tensile strongest.
Compression might produce creep as this is a low rate of stress, and if so
eventually the solder will yield.

It  is likely that one of the most common solder failures in the world is
shield joints:  as in "whoops I dropped my mobile" . Millions do it every
day. Clearly the failure mode though is a sudden high shear rate. You need
to determine how your configuration will be stressed in use.
Mechanical data for solders should be easily available from your solder
supplier.

Regards

Mike Fenner

Applications Engineer, European Operations
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Pb-free: www.Pb-Free.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Grant
Emandien
Sent: Thursday, June 19, 2003 2:55 PM
To: [log in to unmask]
Subject: [TN] Mechanical Stress of a 'seam' solder joint


'Netters,

How does one go about convincing a customer not to use a seam joint as a
mechanical weld. The problem is that due to an oversight by design to
include tabs on a screen wall, the customer requests that we solder the wall
to the PCB in the area where a tab is needed. The joint appears to be under
permanent compression when the unit is finally assembled. From a liability
perspective, should we even entertain this?

TIA
Grant

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