Re: gEDA-user: Footprint TQFP100_14 pitch ?

[Rick Collins <gnuarm.2007@xxxxxxxxx>]

At 03:37 PM 4/24/2008, DJ Delorie wrote:

> > How can I know the pitch and area of the TQFP100_14 footprint
> > available in the pcblib ?
>
>When in doubt, add one to a blank board and measure it.
>
>FYI the "14" is a 14 mm body size.
>
>The TQFP100_14 is an 0.5mm pitch part.
>
>Math: 14mm / 24 spacings = 0.58mm maximum pitch (i.e. can't be 0.65mm)

The TQFP 100 pin package has a 0.5 mm pitch.  There are about 10 or a 
dozen important parameters that you need in order to design or verify 
a footprint.  In the past I have found pre-designed libraries to be 
unreliable.  So I create my own footprints from scratch... well not 
quite from scratch.

I use the manufacturer's data sheet to verify the dimensions of the 
part and I use the PCB Library LP Viewer (IPC-7351) tool to obtain 
workable footprint dimensions.  The only difficulty in using this 
tool is that the naming they use is mostly the formal names which are 
not commonly used by manufacturers.  So you have to hunt around a bit 
to find the footprint you need.  But it is worth it in the end 
because you have a footprint that you can trust in my opinion.

For example, I quickly found two versions of the 100 pin QFP with 0.5 
mm pitch.  One is 1 mm tall and the other is 1.2 mm tall.  The only 
difference I see quickly is the length of the foot which results in 
slightly different length pads.

http://www.pcblibraries.com/

Their LP Viewer library tool is free for general use.  They sell a 
version that allows you to skip the hand copying of the data.




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