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> Why? Making schematic symbols and PCB footprints is not time consuming Whaaaaaat? o_O

by wott 10y ago

Animats 10y ago
I was just making some yesterday. It's time consuming if you use KiCad, which has a draw program with a UI from the 1990s. I could have drawn a footprint in Autodesk Inventor's sketch mode in a tenth of the time, and without having to use a calculator to compute distances from the data sheet drawing. (CAD program UIs are really hard to do well. The big companies have it figured out at last, but the technology hasn't filtered down to open source yet.)
madengr 10y ago
The pre-canned libraries will never have the typical customization needed for PCB. The paste mask aperatures need sizing depending on what stencil thickness you use. Need vias under the QFN belly pad for RF or heat sinking purposes. Do those need tenting on the back side? They also may need to avoid the paste aperatures? How about solder mask relief? Copper defined pads or mask defined pads? Are the part centroids on the correct layer? Also the keep out regions, and 3D model? What I'm getting at is the footprints are more than just copper pads; that's the easy part. They will still require lots of customization, so you are better of just doing them yourself and building up your own library. Now having correct schematic symbol pinouts for that 1024 ball BGA. That is useful. PCB library vendors have come and gone over the 20+ years I have been an EE. Also, as someone else mentioned, the schematic symbols are defined by if you have a logical (digital) or physical (RF) schematic. For example, pin spacing should be such that bypass caps can be squeezed between. Even data sheets have multiple symbols for the same part in the same data sheet; Linear Technology is a good example of this. Anyone doing PCB professionally will make their own symbols and footprints. A hobbyist using free layout software won't pay $29 for a footprint.
- CamperBob2 10y ago
  So, first you say this stuff isn't time-consuming, then you post a list of very well-thought-out reasons why it is. Which is it? Anyone doing PCB professionally will make their own symbols and footprints. Used anything from Analog Devices lately? They provide symbols and footprints via Ultra Librarian ( http://www.analog.com/en/design-center/packaging-quality-symbols-footprints/symbols-and-footprints.html http://www.analog.com/en/design-center/packaging-quality-sym... ). It works fine. This is just a vendor-independent alternative, and a welcome one. That being said: yes, "Trust but verify" are words to live by in this business.

> Why? Making schematic symbols and PCB footprints is not time consuming Whaaaaaat? o_O

by wott 10y ago

> Why? Making schematic symbols and PCB footprints is not time consuming Whaaaaaat? o_O

I was just making some yesterday. It's time consuming if you use KiCad, which has a draw program with a UI from the 1990s. I could have drawn a footprint in Autodesk Inventor's sketch mode in a tenth of the time, and without having to use a calculator to compute distances from the data sheet drawing. (CAD program UIs are really hard to do well. The big companies have it figured out at last, but the technology hasn't filtered down to open source yet.)

madengr 10y ago

The pre-canned libraries will never have the typical customization needed for PCB. The paste mask aperatures need sizing depending on what stencil thickness you use. Need vias under the QFN belly pad for RF or heat sinking purposes. Do those need tenting on the back side? They also may need to avoid the paste aperatures? How about solder mask relief? Copper defined pads or mask defined pads? Are the part centroids on the correct layer? Also the keep out regions, and 3D model? What I'm getting at is the footprints are more than just copper pads; that's the easy part. They will still require lots of customization, so you are better of just doing them yourself and building up your own library. Now having correct schematic symbol pinouts for that 1024 ball BGA. That is useful. PCB library vendors have come and gone over the 20+ years I have been an EE. Also, as someone else mentioned, the schematic symbols are defined by if you have a logical (digital) or physical (RF) schematic. For example, pin spacing should be such that bypass caps can be squeezed between. Even data sheets have multiple symbols for the same part in the same data sheet; Linear Technology is a good example of this. Anyone doing PCB professionally will make their own symbols and footprints. A hobbyist using free layout software won't pay $29 for a footprint.

CamperBob2 10y ago
So, first you say this stuff isn't time-consuming, then you post a list of very well-thought-out reasons why it is. Which is it? Anyone doing PCB professionally will make their own symbols and footprints. Used anything from Analog Devices lately? They provide symbols and footprints via Ultra Librarian ( http://www.analog.com/en/design-center/packaging-quality-symbols-footprints/symbols-and-footprints.html http://www.analog.com/en/design-center/packaging-quality-sym... ). It works fine. This is just a vendor-independent alternative, and a welcome one. That being said: yes, "Trust but verify" are words to live by in this business.