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

---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------