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From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Wed, 5 Aug 2015 15:06:46 +0000
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It is implied all dimensions are with reference to 0,0 datum registration unless otherwise indicated.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chuck Brummer
Sent: Wednesday, August 05, 2015 10:02 AM
To: [log in to unmask]
Subject: Re: [TN] PCB length/width tolerance

Guys, 

I didn't weigh in before but +/- .016" from what?  I tooling hole to the edge? 

If I'm building you a board 18: x 24" and you want that tolerance for the routing of the outside edges I'm not bidding.

my thoughts,

Chuck


Charles W. Brummer | 3M Manufacturing Engineer 3M Electronic Solutions Division 3M Canoga Park, 8357 Canoga Ave. | Canoga Park, CA 91304
Office: 818 734 4930
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From:   "Scott A. Bowles" <[log in to unmask]>
To:     <[log in to unmask]>
Date:   08/05/2015 07:08 AM
Subject:        [EXTERNAL] Re: [TN] PCB length/width tolerance
Sent by:        TechNet <[log in to unmask]>



Bob,

Maybe you can clarify what is driving your question.  You state that the ±.016" seems liberal (and I agree) but this is our subjective opinion. Are you asking from a design/OEM perspective or manufacturing/supplier perspective? Section 3.4 of IPC-6012 states the printed board shall meet the dimensional requirements specified in the procurement documentation. 
However, if there truly isn't any requirement specified then you default to the applicable design series specifications. I would think it is very rare for a drawing to have no requirements, to not even have the "Unless Otherwise Specified" title block tolerances on sheet 1, which typically default to something along the values of three place decimals ±.005", two-place decimals ±.010".

From a design perspective, IPC-2222A, paragraph 5.4.1 states the tolerances specified on the drawing shall accommodate the dimensions and tolerances of the mating part.

I suggest clarifying the requirement before manufacturing product.

Regards,
Scott
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