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March 2000

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Subject:
From:
Paul Klasek <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 10 Mar 2000 12:21:16 +1100
Content-Type:
text/plain
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text/plain (121 lines)
I'd say Werner (archives) condemned this "reliability" checks time over and
again,
even lab performed shears .
My condolences Clayton , the only recommendation on this one is CI's woodoo
doll .
Apply connectors of largest pin counts to desired effect .

PK

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Friday, 10 March 2000 12:02
To: [log in to unmask]
Subject: Re: [TN] Mechanical Straining Solder Joints


Hi Clayton!

Hoo-boy! Got one of those inspectors huh? Ask this person when was the last
time that they had their arm in for calibration for an accurate measure of
force? I had the same experience in the a long time ago in the past where a
source inspector would drag a _STAINLESS STEEL DENTAL PICK_ across fine
pitch
leads to verify whether or not they were soldered! YIKES! The person was
destroying perfectly good solder joints in their "inspection" (if you want
to
call it that).

My opinion is that if visually the solder joints meet the criteria (and
there's some conditions that allow for an incomplete toe fillet, e.g:
exposed
copper from the form and trim) take the tweezers away from this individual,
and politely ask that they please not ruin acceptable solder joints.

Geeze, I thought I heard the last of that sort  of inspection "technique"
years ago...

-Steve Gregory-

> Hi TechNet
>
>  Has anyone got any opinions on verifying solder joint quality by applying
> mechanical strain?
>
>  I have had a board rejected recently for "insufficient solder" on a
corner
> pin of a wave soldered SO08 package.
>
>  The joint was inspected by Customer QC, who determined the joint was
suspect
> due to dull colour and potential insufficient toe fillet.  To verify if
the
> joint was good or bad, mechanical strain was applied to the lead using
> tweezers and wiggling it back and forth.  This caused the lead to pull
from
> the solder joint.  Leaving a pocket of solder on the pad from where the
lead
> was pulled (What was left of the pocket exhibited good heel fillet and
> sufficient toe fillet).
>
>  Customer QC opinion is that if a solder joint is good you should not be
able
> to pull the lead from the joint and if too much force is applied the pad
will
> pull from the board not the lead from the joint.
>
>  My understanding is that a solder joint is not meant for mechanical
strain
> only good electrical contact therefore by applying force even a good joint
> will deteriorate.  Therefore, even if the lead doesn't pull from the
joint,
> the quality of the joint has been affected.
>
>  Any comments?  Would anyone classify this as a valid verification
technique?
> How do you verify a suspect joint?
>
>  Thanks
>
>  Clayton Gardner
>  Engineering Manager
>
>  A.E.M.S
>  11-13 Fiveways Boulevard
>  Keysborough VIC 3173
>  AUSTRALIA
>  Ph. 61 +3 9701 5499
>  Fx. 61 +3 9701 5422
>  Mb. 0416044552
>  Email:  [log in to unmask]
>  WEB:  www.aemspl.com.au

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