Joe Ahearn asked:


>Hi Joe. We are trying to standardize the rotation information for
>components on our PCB designs and wondered if you have this type of
>information.
>
>Our question is: Is there a standard covering component rotation data for
>
>use by pick/place machines when the boards are being stuffed? We are in
>the
>process of updating our component symbol library and one of the things we
>
>need to add to the symbol data is rotation data. We need to know where
>pin
>1 is located to consider the part at 0 degrees. For example, a QFP may
>have
>pin 1 in the top left corner -- would this be considered 0 degrees?

Yes, but 0 with reference to what?

>Any help would be greatly appreciated!

Speaking from an assembler's point of view, the "standard" for rotation
would be affected by several non-design issues.

For instance, when the pick/place machines are programmed, we enter a
rotation from the device pickup point (0,+/-90,180). So, we need to know
what orientation the part will be in when it is loaded on the feeder (which
feeder bank, tape or matrix tray orientation). The orientation on the board
must be known, but there is no "standard" or optimum orientation without
knowing things the designer can't predict that manufacturing sometimes
can't even say which orientation we prefer.

For our pick/place machines, the axis of conveyor movement is "X" and the
positive X direction "up" is 0 rotation. Other machines may differ, and of
course you need to know which orientation the assemblers plan to use in
their conveyor loading.

As regards the "standardization" of orientation reference, My own
preference is to see all the legend markings in the same orientaion, with
12 o'clock (reference to the legend) being 0 rotation at the layout step.
But we often change the orientation of the board in making arrays (2 up or
4 up) for assembly, and this "0" may become -90 on our machines more or
less randomly...

confused? don't worry, so am I...


regards,

Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com