[PROTEL EDA USERS]: SM Device footprints (ex Re: MC13145/6)

["Geoff Harland" <gharland@ingenico.com.au>]

> > Anyone have a footprint for the Motorola MC13145/MC13146.  The package
type
> > is and LQFP-24?
> >
> > Melvin Stevens
>
> Melvin,
>
> Have you found the datasheet for MC13145 at;
> http://ebus.mot-sps.com/ProdCat/psp/0,1250,MC13145~M928145,00.html
>
> and the datasheet for MC13146 at;
> http://ebus.mot-sps.com/ProdCat/psp/0,1250,MC13146~M928145,00.html
>
> You may already have or will notice that not all vendors supply
recommended land patterns.  I could not find any searching Mot's site.  It
is very annoying, to say the least.
> Even IPC-SM-782 has no specs for a QFP 4x4-(for ANY pin count) or a QFP
7x7-48.  Though IPC-SM-782 does provide min solder joints which may or may
not be of help.
> I do not know if wave or re-flow opens another can-o-worms.
>
> Andrew W. Riley III

Based upon advice which I have received about wave soldering, I would
strongly recommend that no attempt be made to wave solder any device having
a footprint like these devices, as, in general, the wave soldering procedure
cannot be reliably applied to SM devices that have pads on all four sides of
a rectangular (or square) outline. (It is possible to wave solder a device
which has pads on two sides of a rectangular outline, but the device still
needs to be oriented in an optimal direction, and in some cases, the
provision of additional "robber" pads is also advisable.)

However, if you have a copy of IPC-SM-782 (which I did in my previous job,
but not in my current one), then this contains details of how you can
calculate the dimensions of each pad in a device's footprint (for reflow
soldering situations). Typically, some calculations are required, because of
the manner in which the dimensions associated with the device itself are
customarily documented, but an example is provided of how to undertake
these.

There is also an "on-line" footprint calculator available on IPC's Website,
which you can access after you have registered some of your contact details
with IPC. I don't know the URL for this off-hand, but I am sure that someone
else on this forum can help you out in this regard in the event that you
can't find this yourself.

In the interests of getting a high assembly yield, I would recommend that
you put in the time to produce, or otherwise acquire, footprints that are
either optimal or otherwise near optimal. It may not be the most fun part of
a job, but it pays off in the long run...

Regards,
Geoff Harland.
-----------------------------
E-Mail Disclaimer
The Information in this e-mail is confidential and may be legally
privileged. It is intended solely for the addressee. Access to this
e-mail by anyone else is unauthorised. If you are not the intended
recipient, any disclosure, copying, distribution or any action taken
or omitted to be taken in reliance on it, is prohibited and may be
unlawful. Any opinions or advice contained in this e-mail are
confidential and not for public display.