> having been in such a situation before i would suggest just making your
> own based on the mech dwg with pad dimensions adjusted according to your
> experience.
> there are not a lot of pins on those uMax

True, but part of effective time management is "managed laziness" ;-)

That is, spend your time where you must, and try to reuse someone else's
work where feasible.  This SHOULD be the cornerstone of modern engineering
practice.  But too often, some stupid thing prevents reuse of work (see next
paragraph).

> I understand why the chip vendors don't show actual footprints on the
> finer pitch stuff
> they don't want the grief/lawyer if there are problems, give the
> customer the pkg dims and then it is their problem according to their
> process window

Ah yes, another instance of lobotomization by lawyer.  What's the matter, is
the phrase "no warranty of suitability for a particular purpose" not a
sufficient disclaimer anymore?

The tech industry has focused their "reuse" goal too high.  They contrive
all kinds of convoluted software languages and schemes to reuse code, and
overlook a million smaller, more attainable items that are practical
candidates for reuse.  PCB footprints, for example.  Take the time that all
electronic CAD users have spent creating the same SCH and PCB symbols, and
multiply that by the average time it takes to create a symbol.  How many
thousands of man-years have been wasted on that?  If I had a choice between
two chip vendors with more-or-less equivalent function parts, and one vendor
had predesigned PCB and SCH symbols that I could plunk right down in Protel,
I'd pick them.

> I would take my best shot, make a small number and inspect and review
> closely with your assembler
> odds are that even if you had the IPC footprint you would not be home
> free

I've got to get it right the first time.

> as to the '$ free' I wouldn't presume to know the answer
> this is like the populist issue: 'a chicken in every pot'
> free airfare would be nice, but would it enhance safety?
> it actually might, or maybe it might not, but someone or some entity has
> to pay

It costs money to produce chickens and air travel.  But Internet hosting of
data for download is *almost* free these days.  Our website is hosted by a
local ISP for about $40 per month.

Best regards,
Ivan Baggett
Bagotronix Inc.
website:  www.bagotronix.com


----- Original Message -----
From: "Dennis Saputelli" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Friday, July 13, 2001 1:21 AM
Subject: Re: [PEDA] need uMAX10 footprint


> having been in such a situation before i would suggest just making your
> own based on the mech dwg with pad dimensions adjusted according to your
> experience.
> there are not a lot of pins on those uMax
>
> the slight (but important) differences in footprints are as much a
> matter of the particular assy process as anything else
>
> there are various rules of thumb as to the heel and toe extensions
> pad width is yet another matter
> the rules of thumb tend to break down as the dimensions get smaller
>
> I understand why the chip vendors don't show actual footprints on the
> finer pitch stuff
> they don't want the grief/lawyer if there are problems, give the
> customer the pkg dims and then it is their problem according to their
> process window
> there really isn't any one entirely perfect footprint for these things
>
> at the finer pitches the type of paste and the quality of the stencil
> wall hole and other specs of the stencil all interact with the design of
> the footprint
>
> I would take my best shot, make a small number and inspect and review
> closely with your assembler
> odds are that even if you had the IPC footprint you would not be home
> free
>
> I have seen people make WORKING boards with the pad width so great as to
> disallow solder mask between, I also have seen and read testimonials
> from people who insist that the pad should actually be narrower than the
> device lead to avoid bridging
>
> then there is the 'pad defined' (I think it is called) where the solder
> mask expansion is actually negative and by design is on the pad so as to
> create a dam for the paste which would seem to fly in the face of past
> experience where any SM impinging on the pad inhibited solderablity
>
> what if you had the 'standard' and it didn't work for you?
> adjust your process to fit the standard?
> or adjust the footprint to fit your process?
> these issues get down to fundamental issues of freedom and choice
> (including of course the freedom to hang yourself)
>
> as to the '$ free' I wouldn't presume to know the answer
> this is like the populist issue: 'a chicken in every pot'
> free airfare would be nice, but would it enhance safety?
> it actually might, or maybe it might not, but someone or some entity has
> to pay
>
> as somebody once quipped "the best number of standards is either one or
> infinity"
>
> sorry to have rambled and good luck with your footprint
>
> Dennis Saputelli
>
> Bagotronix Tech Support wrote:
> >
> > Hello, all:
> >
> > Does anyone have a land pattern (footprint) for the uMAX10 package?  If
so,
> > I would appreciate a copy of it.  Please send it to my e-mail address,
not
> > the Protel group.
> >
> > This is used by a Maxim part, and I called Maxim for the recommended
land
> > pattern.  They didn't have one, and told me to look on my "program disk"
for
> > the JEDEC type M0187.  I finally figured out that what they meant was
"call
> > IPC and get the land pattern".
> >
> > Well, I went to IPC's website, and didn't find anything useful.  It
looks
> > like you have to pay for anything useful.  I guess it's one of those
"open"
> > standards that is really only open if you pay the standards body $$$ to
get
> > a copy of it.  Phooey on that!  I just want a downloadable electronic
> > version, I don't need another piece of paper.
> >
> > I am tired of standards bodies locking up all the vital information with
> > copyrights and big fees.  IEEE is probably the worst in this regard.  In
the
> > Internet age, open standards should be distributed electronically for
free.
> > They can charge for paper copies and physical media.
> >
> > Thank you in advance for your help.
> >
> > Best regards,
> > Ivan Baggett
> > Bagotronix Inc.
> > website:  www.bagotronix.com
>
> --
>
___________________________________________________________________________
> www.integratedcontrolsinc.com            Integrated Controls, Inc.
>    tel: 415-647-0480                        2851 21st Street
>       fax: 415-647-3003                        San Francisco, CA 94110
>

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