Electronic Component Zero Orientation and Rotation in Tape

[ma...@makr.zone]

Hi everybody

I'm in the course of documenting the ReferencePushPullFeeder in the Wiki.

https://github.com/openpnp/openpnp/wiki/ReferencePushPullFeeder (work in progress).

One point is the "Rotation in Tape" setting. I've looked at the Documentation here

https://github.com/openpnp/openpnp/wiki/ReferenceStripFeeder#rotation-in-tape

as a guide.

Example:

However, this is not how I understand the industry standard, as documented in these documents:

• Electronic Component Zero Orientation For CAD Library Construction
  http://ohm.bu.edu/~pbohn/__Engineering_Reference/pcb_layout/pcbmatrix/Component%20Zero%20Orientations%20for%20CAD%20Libraries.pdf
• EIA-481-C (Revision of EIA-481-B) OCTOBER 2003
  (no online source found anymore, but see image at end)
  

Reasoning:

1. A component at 0° (zero) as drawn in the E-CAD has its pin 1 in the upper left corner.
2. EIA-481-C Figure 1 "Component orientation and quadrant designations" has the tape with its principal sprocket holes at the top, unreeling to the right. It calls the quadrants "upper left" etc. as seen in this orientation. I.e. this is the 0° (zero) tape orientation. So far so good.
   
3. But why is the first example given in the OpenPnP Wiki then called  +90° ??? This should be 0° IMHO.
   

What am I missing here?

_Mark

[Ian Arkver]

Hi Mark,

I found a presentation by Tom Hausherr whose blog article was linked on the original Wiki (but is sadly no longer available).

https://www.mikrocontroller.net/attachment/364589/PCB_Design_Optimization_Starts_in_the_CAD_Library.pdf

This is a good presentation generally, but the zero-orientation bits start around page 78.

I think the choice of zero quadrant is different for IPC-7351 vs. IEC which might account for the 90degree offset.

All the best,
IanJ

[ma...@makr.zone]

Hi Ian

Thanks for the link, that seems to explain it, especially page 77. I don't claim to really understand what this means in terms of "standardization power" one vs. the other and I still don't understand why the first example (in the image from my initial post) should be +90° and not -90° if interpreted as IEC 61188-7.

But I'll settle for a pragmatic approach for OpenPnP. See here:

https://github.com/openpnp/openpnp/wiki/ReferencePushPullFeeder#tape-settings

It is almost unbelievable the industry hasn't agreed on this a very long time ago. It seems that manufacturing volumes are so high, they can afford to spend a lot of time setting up machines, again, and again, and again. And to afford to throw away 10k boards if they got it wrong...

_Mark

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