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May 2010

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Subject:
From:
"Temkin, Gregg" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Temkin, Gregg
Date:
Wed, 19 May 2010 15:48:51 -0700
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On a first shipment from a new PWB supplier, we found all the 0402 component outlines deleted from our legend layers.  The PWB vendor said they automatically deleted the marking during DFM because it exceeded their manufacturing allowances and could have resulted in ink covering a portion of the pad.

Our in house PWB designer uses a program to develop his pad and marking dimensions.  The program would not generate a marking outline for this device, so he designed the outline to be the courtyard plus some manufacturing allowance.

Other vendors have supplied with PWBs with the same outline marking configuration; seemingly without any problem.

I've reviewed IPC-7351A, but couldn't find mention of PWB marking recommendations.  Is there guidance that I missed of is there another document I should be looking at?  Is it generally assumed that outline marking of 0402 and smaller devices is impractical?  Is placing a remotely located legend the best way of showing 0402 placement and orientation?

Thanks for your help.

Gregg




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