FEDEVEL
Platform forum

zeino , 02-08-2016, 12:33 PM

When should we use IPC compliant footprint wizard? Shouldn't we always be IPC compliant regardless of soldering it by hand or using picking machines ...? Would it mean for manufacturing we would need to do the layout again if the footprints are changed to be IPC compliant. What are your thoughts about it.

robertferanec , 02-09-2016, 12:44 AM

You can use IPC wizard, no problem. I prefer to use footprints from datasheets, and I found, that the way how standard Componet Wizard works is easy and fast to use with datasheet footprints.

zeino , 02-09-2016, 04:33 AM

Probably it would be good idea to compare the "Walsin pdf+ our courtyards" with the 3 levels of IPC-7351B courtyard values. To me it seems the values in the chart is compliant with the minimum value but not sure. If that is so adding 0.2 to the value would be closer to the Nominal value and 0.7 closer to the largest courtyard without manufacturing zone extra. So 3.08+0.2 gives ~3.3 if nominal, ~3.8 if max courtyard is made and on the side, 1.85+0.2 = 2.05, or 2.55 for max.

At the end the manufacturer defines the manufacturer zone courtyard and it is just to give a realistic view when building compact designs.

Also regarding the land pad on the footprint, I see that the rectangular is chosen. It is better to choose the rounded rectangular as it is better for manufacturing and the corners would not have the paste anyway. It seem that is the trend.

There is a great Mentor Graphics blog on this: https://blogs.mentor.com/tom-hausherr/page/2/ and how to calculate the courtyards and things related to the latest IPC standard.

The history about my obsession with IPC standard is once I gave an upverter layout to a manufacturer/designer explaining how the RF layout would look like when he came back telling me what I have drawn is too optimistic and the real thing is less compact and wouldn't fit complying with the IPC level and manufacturing zones they require. I dropped using Upverter as I didn't know if their standard is correct regarding the footprint

robertferanec , 02-10-2016, 12:00 AM

Maybe very long time ago (like 10 years ago) we had some problems with assembly, but these days I have not heard about many problems. Unless you go into extremes (like VIA in PAD), you should be fine. We mostly use footprints from datasheets, then we always print the footprints and compare with real components. If footprint or pads look bad (e.g. pads are too small or too big), we just adjust them.

Same for PCB manufacturers - unless you do something really bad, I believe, if needed, they adjust the problematic parts of PCB by themselves. From our experience, the biggest problem with PCB manufacturers is to get a good stackup. Sometimes they do comment on "a track too close to a hole or edge" or something similar, we adjust it and it's fine. Very often we send PCB into PCB house before it is finished, so if there are any problems, we can adjust our PCB before the final data are generated.

I hope it helps.

zeino , 02-10-2016, 12:20 AM

Thank you Robert.

EVW13 , 02-17-2016, 10:10 AM

Just to avoid crossposting- some comments on Altium footprint wizard.