Find IC footprint

[alamwte]

Hello,

I have a question.
What is the true way of finding a PCB footprint of ICs?
 For example I can not find the IC's footprint by its part number. But I know it is a QFN 56 7x7 .
How can I find the standard dimension of these packages to build its footprint by my own?
I have found many dimension for this package!!
I even found different footprint in Snapeda.com

please guide me,
Thanks ,

[Pseudobyte]

If the manufacturer doesn't include the footprint information in the datasheet, they usually include at least the internal package name/drawing number. When you go to the manufacturer's website or do a careful web search you should be able to find the drawing of the footprint.

As you have discovered there are many QFN56 7x7 packages. If there is a drawing of the geometry of the physical part, QFN's are easy to make footprints for from scratch.

[alamwte]

In its  manufacture's site is just written its package is QFN56 7x7.

Now I want to find out where can I find its dimension ?
Is there any site that I can find the QFN packages standards?

I have found some different dimension of this package in every site. for example in nxp.com and ti.com or FTDI.com it has different dimension.

Thanks,
 

[thm_w]

I have found some different dimension of this package in every site. for example in nxp.com and ti.com or FTDI.com it has different dimension.

Yeah but is it close enough that it would work, thats all that matters.

[alamwte]

OK, thanks