I have setup SPC programs in the past as I am currently doing. Then, I used software as SAS or some
other that didn't provide benefits available in QC-Calc for Windows.
My current major emphasis is on solder past profiling. Also, I am analyzing PCB board "stretch",
"shrinkage", fiducual locations on boards and coresponding openings in stencils, pad and stencil
opening locations, clogged stencil openings, etc.
We have six DEK 265 GSX, Fuji IP & CP + glue, and BTU lines with MYDATA joing the mix within the
next two months. We are doing about 12 million placements per month going to much more. The mix is
as yours - low volume and high mix with 9 different board types or classes. These include double
sided SMT, through hole, and whatever else our customers want - not within reason with DFM being
executed for the most part.
We never expect to do real time X bar R charts but expect very fast corrective action to the design
level. We cannot afford operator interaction using provided information. Instead, we use our DEK
programming capability to down load, in QC-Calc, to the machine's hard drive. Then, we load the raw
data into another computer for ANOVA and brainstorming to correlate cause and effect.
Print profiles are correlated, as 3D information, to viaual inspection, then to solder joint
quality, then to x-ray, then to functional test. Again, all this is done to make very fast
corrective action possible with DFM/CE changes mad to ensure future designs more producible.
The QC-Calc software package may be used in real time via a serial port to a stand alone computer
accompanying your printer. It may be used in a batch mode, or it may be used as I am doing now
which works for our capabilities.
There is much more that can be done. The key to our process control is using the best design rules,
best board fabricators and stencil makers, employing the best test equipment/resources/people, and
ensuring designs and processes are continuously improved. One example of this is using our BTU
ovens with our nine different board classes. We have only one profile to do it all with very few
defects. Another is our wave solder pot temperature set at 470 with corresponding preheat
temperature to ensure no cracked chip devices.
There is so much more, but it all can be summed up by saying KISS and ensure processes and designs
are proven before starting operations. Plus, ensure maintenance and calibration are performed as
required.
It keeps going on - with or without us and our SPC stuff. It's just a matter of how well it gets
done.
Earl Moon
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