PCB footprint insertion origin

Are you referring to how the tool will generate a pick and place file? It doesn't matter, eventually your assembler will translate to whatever he wants for his particular tool. Anyways, most PCB tools let you choose to what point the cursor sticks to when placing on-screen, you can usually choose from centroid, 0,0, pin 1 or user select (which can be any pin# or a x,y).

Probably depends on the component. I might want to place the center of a coaxial jack on a precise center line, but not care much where (and whether they were off-grid) the hard metric pin locations turn up on my inch standard board. OTOH, for a part that does not have some mechanical relationship with the outside world other than through the padstacks, probably you'd rather use pin 1 or something like that. Best regards, Spehro Pefhany

You don't solder a part down from the center of the silkscreen.

All parts should reference a real copper "foot print", not painted art work.

My .02

donald

Th reason I posted this question: some time ago we were asked by assembly house to place origin and insertion origin in the middle (if my memory serves me right). Now we are trying to clean up the libraries and I started having doubts.....

Look at the IPC requirements. Most assembly shops use this standard. Cheers

I have goggled for "IPC requirements", but I still do not understand what IPC means.

Please elaborate a little more about IPC requirements.

Thank you

donald

Found it:

Institute of Interconnecting and Packaging Electronic Circuitry

I'll have to check this out.

thanks

donald

means.

Have a look here...

They have a std IPC-7531 land pattern calculator, SMT only but it should give you an idea....

Cheers

In Layout, you want to place the datum at the center of the part. This is contrary to what Orcad wants you to do with the datum. Layout was developed in the days of parts on 50 mil pitches. This will prevent the component from being placed on a weird grid after you rotate it and/or place it on the opposite side if the pads aren't on a multiple of your placement grid. When the part gets placed on a weird grid, you need to pick up the part and place it down again to get the part to snap to the proper grid (you'll see the part jump to the new location). This is a very annoying bug in Layout. Placing the datum on the center of the part solves this issue. Layout, which was the Massteck(sp??) router of yore, had a lot of issues with coordinate translation and rotation. Back in the mid 90s, I got sick of moving Layout projects back to PCAD to give proper pick & place coordinates for bottom mounted parts. I figured out the translation/rotation math and gave it to the Layout manager so they could post a work around using Excel. They actually fixed the next release of the program. Boy, folks think Layout is a bear to use these days, you should have seen how horrible it was back then!

Always put the pick & place point at the center of the part for a symmetrical part (like smt resistors). For odd parts where the body isn't centered on the pads, I'll put the pick & place point on the center of the body.

But you're still the dummy one.

...Jim Thompson

Maybe that's why everyone was using Autotrax back then :-)