Steve:
You may want to ask him to perform the inspection for you so that you can
watch his technique. I had one customer who was using a pick with a tip
that was probably 25 mills in diameter at the tip. He was using it and was
using way to much force. I gave him a much smaller pick - appropriate for
25-20 mill parts. He was under the impression that if he could break the
joint with the pick, the joint was no good. I explained to him that any
fine pitch solder joint can easilly be broken by hand using a pick as a
lever. In the end, he was basically embarassed that he had been destroying
perfectly good solder joints.
It may just be that your customer has a mistaken impression of the force
required to break a solder joint.
At 18:51 1/13/97, [log in to unmask] wrote:
>
>Hello all,
>
> I've got a question, how many of you out there check whether or not a
fine
>pitch solder joint is good by dragging the tip of an exacto-knife blade or a
>steel pick across the foot of the leads?
>
> I have seen it done back in the past by a few inspectors maybe 4 or 5
years
>ago, but not anytime recently...until I heard about it today. Is this still a
>common practice?
>
> I'm pretty sure it's not the smart thing to do, but when you have someone
>call and tell you that the fine pitch solder joints on the board you built for
>them are insufficient because the leads come loose when they check them
with an
>exacto-knife...they sure don't want to hear you tell them that they
shouldn't be
>dragging anything across the leads.
>
> I'm almost sure it's not one of the cases where sometimes a solder joint
>will become plastic during wave soldering and separate from the pad, some
of you
>may have seen that before. You know, where the fillet stays attached to the
foot
>of the lead with a nice wetting angle and all that stuff, but it's not
attached
>to the pad...but I haven't actually seen the actual boards that supposedly has
>the insufficient solder yet, the customer has to bring them to me...
>
> Oh, another thing, these boards have all been through and passed ICT, a
>24-hour burn-in, and a functional test after burn-in. So it would seem to me
>that if I have a problem with my solder joints, it would have showed itself
for
>sure in burn-in...
>
> But before they get here, I'd thought I'd ask and see if it's a common
>practice to rake fine pitch leads with a steel object...by the way, we're
>talking about .020" pitch QFP devices here...
>
>
>(gimme' some ammo guys!) Thanks in advance!
>
>
>
> __\/__
> . / ^ _ \ .
> |\| (o)(o) |/|
> #------.OOOo----oo----oOOO.-----#
> # Steve Gregory #
> # SMT Process Engineer #
> # The SMT Centre Incorporated #
> # [log in to unmask] #
> #________________Oooo.__________#
> .oooO ( )
> ( ) ) /
> \ ( (_/
> \_)
>
>
>
>
>
>
>
>
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-Pat-
-------------
Patrick McGuine
Nicolet Instrument
[log in to unmask]
(608) 276-6334
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