How to determine footprint size from old datasheets?

[MarkS]

I'm trying to create a library for the QFP variant of the MC68030. This was a time when dimensional drawings were found in datasheets, but a recommended PCB layout wasn't. The link to the datasheet is here (PDF) and the package diagram is on page 578. It tells me clearly how wide and long the pins are where they contact the board, but from what I've seen pads are typically slightly longer and wider than the pins. Since the datasheet doesn't specify, how should I proceed? Should the pads be set to the maximum dimensions of the pins(D and K in the diagram), somewhere between the minimum and maximum, or is there a general guideline to follow?

[ElektroQuark]

Try the test version of Library Expert software. It will do all calculations based on IC dimensions.

[MarkS]

Thank you. I'll check that out, but it really doesn't directly answer my question. I'm not looking for a simple solution, but rather the knowledge to figure it out on my own. This was an extremely popular chip in its day and those who used it knew how to do this.

[ElektroQuark]

Maybe this can help: CLICK!

[MarkS]

NICE! Yes, that is VERY useful! I did download the free version of Library Expert and created the part in that. I was surprised that it outputted a footprint very similar to my guess, although my footprint was a lot rougher.