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January 2003

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 6 Jan 2003 17:19:01 -0500
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text/plain (82 lines)
Good reply but I think he means space not place.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Matthias Mansfeld
> Sent: Monday, January 06, 2003 3:34 PM
> To: [log in to unmask]
> Subject: Re: [TN] SM-782A
>
>
> On 6 Jan 2003 at 12:25, Black, Paul wrote:
>
> > My company is in the process of relayout of a board, and we
> are trying
> > to use SM-782A for component layout. However, we are seeing
> a number
> > of discrepancies between the recommended layout from the component
> > manufacturer and the SM-782A standard. The differences include pad
> > length and width, and distances between pads and pad rows.
> Does anyone
> > have experience with this problem, and what is your recommendation?
> >
> > Thanks in advance,
> > Paul Black
> > Manufacturing Engineer
> > Kronos Incorporated
>
> The IPC standard tries to define optimum footprints for best
> process safety for the worst case sum of tolerances (means it
> should fit with nearly every board shop and every assembly house).
>
> Footprint recommendations from component manufacturers may
> base on own tests under standard or specific conditions and
> can save place and trouble (good example are the great
> Philips footprint guidelines which need often much less place
> than IPC but need a bit more precise placement equipment and
> sometimes a few prototype runs to optimize the soldering process)
>
> Or they result on nothing more than untested own thumb rules
> with no scientific or experience-based justification. That's
> worst case.
>
> The best idea is to check critical dimensions against IPC,
> against good-known other recommendations (like Philips) and,
> most important against the experiences of your favourite
> assembly house.
>
> HTH, Regards
> --
> Matthias Mansfeld Elektronik
> * Printed Circuit Board Design and Assembly
> Am Langhoelzl 11, D-85540 Haar, GERMANY
> Phone: +49-89-4620 0937, Fax: +49-89-4620 0938
> E-Mail: [log in to unmask]
> Internet: http://www.mansfeld-elektronik.de
>
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