IPC-7351 component rotation confusion

[frank26080115]

I need to generate a table of component placements so an assembly company can assembly my boards.

The problem is knowing what exactly is "zero degrees" for each component. I found some documents and webpages (mainly this page and there's a link to another PDF on the bottom of that page) http://blogs.mentor.com/tom-hausherr/blog/tag/ipc-standards/

Now here's the confusion, I take out a piece of cut tape with diodes, holding it with cathode on the left and anode on the right (as dictated by IPC-7351 document), the tape will have holes on the left side. I take out another piece of cut tape with some SOT-23-5 chips, hold it so that the side with 2 pins is on the right (as dictated by IPC-7351 document again), the tape will have holes on the right side.

What the hell? Why is it different?

The real problem is I don't know how to orient a lot of custom components in my CAD library, and I am trying to depend on the tape to tell me what the zero-degree orientation should be. If there is a discrepency between a diode and SOT-23-X, then I don't know which convention to follow.

[free_electron]

this is irellevant. don;t worry about it.
the assembly people will verify the rotational offset.

[frank26080115]

the assembly people will verify the rotational offset.

I don't know... They seem pretty busy, most responses were canned or even automated, and they've already missed some details during quotation.

Should I take a survey of my own inventory and see which convention is followed the most, and then follow that, and then give the assembler a note saying so? This sounds like a good thing to do regardless, makes both of our lives a bit easier, in a way.

[free_electron]

again , it doesn't matter.

they pre-run polarized parts and verify the correct orientation for 2 pin polarized parts.
for multipin parts sot23 etc it don't matter as the machines camera will detect it. they have pattern recognition. during teach-in the machine detets it and correct automatically.
i had an old Zevatech z750 that already could do that fully automatic and this was a 20 year old machine.

[frank26080115]

for multipin parts sot23 etc it don't matter as the machines camera will detect it. they have pattern recognition. during teach-in the machine detets it and correct automatically.
i had an old Zevatech z750 that already could do that fully automatic and this was a 20 year old machine.

Ah, cameras, that's smart

This company does sound like they have some high speed high tech stuff... I hope you are right.

Thanks