From: "Leo Potjewijd" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Saturday, February 07, 2004 4:47 AM
Subject: Re: [PEDA] Semiconducto rmfg Footprint creation


> Calculating SMT footprints can be quite laborious as the
datasheet-supplied
> measurements often need serious work: calculating that
> needed-but-not-supplied dimension, (re-)calculating tolerances and offsets
etc.
> The online SMT footprint calculator from IPC asks for numbers that are
> often not in the datasheets but are required to complete the calculation
of
> the footprint....
> Calculating the footprint yourself also requires knowledge of the PCB
> stuffing and soldering techniques that will be used later on.... And even
> then, some footprints cannot be calculated (but that might be my
> misunderstanding of the mathematics involved ;).


This is why I created my QFP & TSOP footprint generator, It does all that
math for you automatically.
get it here:
http://www.proteluser.com/download/Pcb_99SE_add-on/BriansStuff/

The "brians_public.txt" describes the contents of the "brians_public.zip"
file.  Take a look at the library footprint generator & it's documentation.
No more mathematics to understand or do, all you need are the footprint's
general drawing dimensions.

_____________
Brian Guralnick


----- Original Message ----- 
From: "Leo Potjewijd" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Saturday, February 07, 2004 4:47 AM
Subject: Re: [PEDA] Semiconducto rmfg Footprint creation


> Well, I've got 2 (euro)cents to spare:
>
> I'd settle for footprint definitions in DXF, preferably also showing the
> paste mask  and component outline.
>
> That would already make a huge difference in work when defining a library
> component, with virtually no extra effort on the manufacturer side. I
mean,
> they probably designed the mechanics of the component too, so they must
> have that information in some sort of CAD system (and what CAD system
> doesn't export DXF? virtually none..)
>
> After spending considerable time de- and refining a DIN41612C96 footprint
> by manually entering the data from the manufacturers' datasheet (and
ending
> up with a less-than-perfect footprint) I stumbled upon their DXF drawings.
> I imported them in a scratch PCB file, stripped all unnecessary
> information, added the pads on the positions indicated and then
copy-pasted
> the whole thing to the PCB library (P99SE you know). The whole process
took
> no longer than the manual definition even though it was the first time I
> tried this procedure; the result not only looks great  but is stunningly
> accurate...
>
> Calculating SMT footprints can be quite laborious as the
datasheet-supplied
> measurements often need serious work: calculating that
> needed-but-not-supplied dimension, (re-)calculating tolerances and offsets
etc.
> The online SMT footprint calculator from IPC asks for numbers that are
> often not in the datasheets but are required to complete the calculation
of
> the footprint....
> Calculating the footprint yourself also requires knowledge of the PCB
> stuffing and soldering techniques that will be used later on.... And even
> then, some footprints cannot be calculated (but that might be my
> misunderstanding of the mathematics involved ;).
>
>



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