Steve - If you have some specific quality issues that you would like to
solve, direct your SPC efforts in that direction. Look at all the variables
in the process and choose variable attributes that are easy and inexpensive
to determine. For example, if solder paste registration is a problem for
you, take some dimensional measurements on the stencils and on the pad
locations on the PCB. Chart these attributes and see what you get. For
Small Lot quick turn business, try to use short run charting techniques.
Keep Smiling
Dick Desrosiers
Director of Manufacturing
Harbor Electronics
3021 Kenneth St
Santa Clara, CA 95054
408-988-6544
408-406-3729 (cell)
[log in to unmask]
-----Original Message-----
From: Stephen R. Gregory [SMTP:[log in to unmask]]
Sent: Monday, October 25, 1999 1:55 PM
To: [log in to unmask]
Subject: [TN] SPC programs, how make the best use of the
efforts..
Hi All,
I'd like to ask any input or opinions on how to implement a SPC
program that
will really be meaningful. I don't want to waste time and effort on
something
if all it's going to produce is "window dressing"...
Our business is very high-mix/low volume stuff. From boards that are
very
straight forward, standard 50-mil pitch stuff, to those that have
every part
on the board (SOIC's, CQFP's) cut and formed, pre-tinned, and then
placed and
reflowed. A big run for us is 100-boards, most of the time it's 50
and under.
I guess what I'm saying is that there are TONS of variables with a
lot of the
products we build here.
We do a lot of hi-rel stuff here, very custom, almost hand built
boards. We
also hand place a lot of components here...for example the resistors
on a lot
of the boards come to us in little 2" X 2" matrix trays that can't
be machine
placed. Any design problems that cause defects on the boards most of
the time
won't be corrected because the document trail that has be completed
is so
daunting that our customers tell us to not ask for changes because
it won't
happen, and our time is best spent figuring out a way how to deal
with it.
So what I'm wondering in a situation like this, what good is SPC
going to do?
I think the time spent trying to correctly identify all the
variables and
gather meaningful data would be better spent in training and working
with our
operators to learn all the little nuances with the product we build
so we can
deal with them. What was proposed to me for example in screen
printing, was
to create a simple attribute chart for example;
1. Is the paste coverage complete? Yes/No
2. Is it registered on the pads? Yes/No
3. Is the paste smeared? Yes/No
or such simple attributes such as that, and then plot them on a
chart. To me
it'll be a waste of time. We don't have anything to quantify any
measurements...no paste height measuring equipment, or X/Y measuring
equipment, everything will be done by the ol' Mark-I / MOD-I eyeball
with all
it's subjectivity...but I am still being asked
to establish an SPC program in SMT.
Am I fighting this too much? Or is there some means that will be
worthwhile
to make this happen? Oh yeah, it's gotta be cheap (next to nothing)
too...
Thanks in advance!
-Steve Gregory-
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