Shawn, that's a great question. Let me contribute to TechNet with something other than a question, if only an odd story. Maybe IPCers can add more.

645 came out spring of 1993-19944. I learned about it by attending the developing committee's wrap up meeting at a the IPC conference in Boston in April of 94. The committee was reorganizing, as its original work was completed, and I volunteered, although a newcomer to the industry, to fill the seat as chair. To me, the work and document seemed important.

In subsequent months, I studied the document, found lots of typographical errors and maybe some chances for editorial improvement. The other committee members at the time provided no encouragement or discouragement. In time, I went to work at a razor factory and dropped the matter. Then a few years later, I started working in assembly again, got back in the 645 chair when solicited by IPC. Still was not able to get the updates made before I went off to work at a college.

So 645 is still at the original version. To my knowledge, it remains a valuable, maybe unique, source of guidance on how to use human eyes in inspection.

Various acceptability standards, including those of IPC, are of limited value in defining instruments for use for visual inspection by humans. To be less vague, magnification is commonly specified when resolution is the critical parameter. As I've put it, quoting some long forgotten source, the purpose of a microscope is not to magnify but to resolve detail. Numerical aperture is the critical parameter, not magnification or focal length. The distance at which the inspector focuses ips eyes contributes to the conduct of inspection, and that is not something a standard can control. (I use 'ips' as a generic personal analogue to the neuter singular possessive 'its', and I don't take credit for inventing the word.)

TechNetter Chris Mahanna and I, along with some others, discussed the matter of optical aids during the 6012 committee meeting at EXPO 2011. (I was not able to attend 2012.) We outlined a structure for improving the visual inspection aids criterion, but I, for one, have not done anything more than talk about it since 2011.

Any other TechNetters who have something to say about 645, I am interested in hearing. It would not be a bad idea for more people to have a look at it.

Louis Hart

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Upton, Shawn
Sent: Thursday, June 07, 2012 8:58 AM
To: [log in to unmask]
Subject: Re: [TN] Looking for a specification

What is IPC-OI-645 "Standard for Visual Optical Inspection Aids"?

Looks like I will want to get copies of 600, 6011 and 6012; not sure if 960 is necessary or not (not doing mass produced boards).

Thanks.

Shawn Upton, KB1CKT
Test Engineer
Allegro MicroSystems, Inc
[log in to unmask]
603.626.2429/fax: 603.641.5336



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