Is anyone aware of benchmarking data to suggest what is best-in-class (and average) performance for manual visual inspection?
We would like to better understand what percentage of defects going into the process will be screened out. This provides us something to use in comparison and justification of alternate methods (i.e. AOI, AXI, test).
Great if we could also understand "best practices" for this process as well. Has anyone put effort towards the study and improvement of this process? Is inspection only used to provide insight into the performance of other processes and never formally optimized?
We use a great concensus document for inspection. It is: IPC-A-610C, Acceptability Of Electronic Assemblies as the basis for accepting assemblies. You can find it at IPC [http://www.ipc.org]. [Help!!!! I�m turning into an IPC Cal.]
We find that many different things cause inspection rejections vary. AOI seems to be a great leveler. The question becomes: How many of these machines can you justify?
No problem with the workmanship standard. Our staff are all trained in the C rev and we use it as our standard. Most of our clients are referring to it as well.
The main problem is with untested product. We currently rely on manual visual inspection as the only means to verify compliance with the relevant workmanship spec for these products.
How can I predict what the DPMO will be coming out of inspection? I'm sure I could plan some data gathering to determine this but this doesn't tell me where I should be (average) or could be (best-in-class). I need this info to help in justifying test (or other solutions) to our clients and ourselves. Want to put an end to the "shouldn't have inspection caught that" syndrome.
We rate each board for producibility. [Our rating chart may be based on some things that Bob Willis did. Check his site [http://www.bobwillis.co.uk/ ] for all kinds of neat stuff. Maybe even bring him in to help you sort through things.]
There is a fair amount of correlation between our rating and build-to-cost. We have never drilled into the type detail you seek. But then again if your building to cost, who cares about the rest of the stuff, eh?
Can anyone add any new info to this old thread? We be great if a study was available detailing expected performance and factors that can have an impact like complexity, fatigue, etc. Lots of AOI mfrs claiming that there are studies on this but noone identifies them.