Neil - I have spent a number of years implementing SPC into PCB
manufacturing. I have also applied it to cable making where we had little
but attribute data. To hedge my answer slightly, I am not sure what you
are really seeking to define, what your objective is.
In PCB manufacturing, each key process can be controlled by SPC either by
looking at the output or by identifying the most important variable in the
process. There isn't a quick and easy answer, however, if you really want
the data you gather to have meaning.
For example, on a Hot Air Solder Level process, you might look first at
measuring the output, i.e. solder thickness. On an etch line, the output
easiest to measure may be the etch rate. On an electroless line, it might
be the thickness of the deposition.
Each of these outputs, however, just reflect the control of the key
variable that drives the process. In electroless, the deposition might be
most influenced by say temperature. To assure that the deposition rate
remains as consistent as possible, charting and control the temperature may
be key.
Anyway, back to your question. To determine the capability of any of the
processes above, you can use the measurement data you gather from the
output. If, however, you are looking at capability in terms of yeilds,
then count may be your only alternative.
Marti Tully
Stickley-Vejar PWB Technical Services
Phone 602 995-0227 or 877 792-8324 (toll free)
[log in to unmask]
_____________________
Neil Atkinson wrote:
> Does anyone out there have any experiences of implementing SPC into PCB
> Manufacture, surface mount placement or wave soldering?
>
> And if so, what do you measure / count, have you been able to use many
> measures which allow you to calculate capability indices etc. At the
> moment I am getting bogged down in counting faults and using attribute
> charts as opposed to variables.
>
> Help!!!
>
> Neil Atkinson
>
> -------------------------------------------------------
>
> Part 1.2 Type: application/ms-tnef
> Encoding: base64
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