Author Topic: How to determine footprint size from old datasheets?  (Read 1899 times)

0 Members and 1 Guest are viewing this topic.

Offline MarkS

  • Frequent Contributor
  • **
  • Posts: 530
  • Country: us
How to determine footprint size from old datasheets?
« on: June 21, 2017, 08:43:19 pm »
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?
« Last Edit: June 21, 2017, 08:45:09 pm by MarkS »
 

Offline ElektroQuark

  • Supporter
  • ****
  • Posts: 1209
  • Country: es
    • ElektroQuark
Re: How to determine footprint size from old datasheets?
« Reply #1 on: June 21, 2017, 08:48:13 pm »
Try the test version of Library Expert software. It will do all calculations based on IC dimensions.

Offline MarkS

  • Frequent Contributor
  • **
  • Posts: 530
  • Country: us
Re: How to determine footprint size from old datasheets?
« Reply #2 on: June 21, 2017, 08:53:14 pm »
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.
 

Offline ElektroQuark

  • Supporter
  • ****
  • Posts: 1209
  • Country: es
    • ElektroQuark
Re: How to determine footprint size from old datasheets?
« Reply #3 on: June 21, 2017, 09:28:31 pm »
Maybe this can help: CLICK!
 
The following users thanked this post: MarkS

Offline MarkS

  • Frequent Contributor
  • **
  • Posts: 530
  • Country: us
Re: How to determine footprint size from old datasheets?
« Reply #4 on: June 21, 2017, 10:38:45 pm »
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.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf