Stephen -
One of the first things you may want to consider is to inform your Quality
personnel the first solder joint is the best solder joint. Reworking or
touching-up the same solder on a solder joint, without removing all the
original solder, decreases the strength of the solder joint due mostly to
the larger metallic crystallization. Rework should only be done when you
truly have a bad solder joint due to factors such as poor wetting,
insufficient solder, insufficient reflow, poor component placement, etc.
The cosmetics of the solder joint (e.g. bright, shiny solder joints) are a
good goal for aesthetic reasons, but are not a good indicator as to the
quality of the solder joint. I am reminded of the days when we soldered
surface mount assemblies with Vapor Phase soldering. Vapor Phase was and is
an excellent soldering process, but the solder joints were typically not
bright and shiny. We ended up convincing our QA Engineers by
cross-sectioning a number of "failed" solder joints and demonstrating to
them the excellent wetting angles. We also did pull tests, which further
convinced them to revise their fail criteria.
Good Luck! Ed/
Ed Valentine
Electronics Manufacturing Solutions
Phone: (919) 270-5145
Fax: (919) 847-9971
www.ems-consulting.com
[log in to unmask]
----- Original Message -----
From: Stephen R. Gregory <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, February 07, 2000 9:04 PM
Subject: [TN] Rework vs. Quality...
> Hi ya'll!
>
> I know this is going to be question with no easy answers. What I want to
ask
> is how do you go about evaluating the real effort that is being expended
on
> rework or touch-up? Then prove what was necessary, and what wasn't?
>
> To set the stage, the process is mainly "gate-inspection" (I know that's
not
> desirable) but that's what it is. Past history has been to meet standards
> that match a picture (Martin Marrietta comes to mind). Not whether or not
> touch-up or rework is adding any reliability or value to the finished
> product, or is just make it look like the pictures. (reading between the
> lines;..that quality mindset is THOROUGHLY ingrained here)
>
> So how do you getting a good un-biased snap-shot of what is actually going
on
> out on the floor, and then go about changing things?
>
> I believe that there is no simple way. It's going to take a lot of time
and
> effort to take assemblies that are in process, identify them by way of a
> serial number or some other means, have a referee (knowledgeable unbiased
> person) inspect them after each major process to determine what (if any)
> defects are on each assembly, then let them continue on through the
process
> with the instructions that any rework or touch-up performed on the
assemblies
> must be documented as accurately and completely as possible as to what
> defects were observed, where, and why they were reworked. Then afterwords,
an
> assessment done on the whole quality process.
>
> As you may guess, there is some thought going around that we rework more
> things than we need to. I'm just trying to find a way that will be the
most
> effective, and that will be as unbiased as possible. Also as you may
guess,
> this subject can get pretty emotional with the QA folks...I butt heads
every
> single day. I want to find a way that nobody can argue with.
>
> Yes, It does still seem a little silly that I need to secretly strategize
a
> plan to bring out the realities of the situation in order to convince
certain
> people to change their philosophies. But I have been asked to do it, and I
> got the the task because they think that I have a magic solution to change
> certain mind-sets, but I don't. I'm asking if any of ya'll have had to go
> through a situation such as this, and what you did to resolve the obvious
> issues...
>
> Thanks everybody!
>
> -Steve Gregory-
>
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