Re: gEDA-user: Specification of Rotations for Auto Assembly

[John Griessen <john@xxxxxxxxxxxxxx>]

Rick Collins wrote:
you still have to decide if the bottom side is
> viewed from the top or the bottom.

Always take the viewpoint of looking down at the board
as it physically would be, never as a see through image
is what they want.

> When I have asked assembly houses about what they assume as convention, 
> I never get an answer.  They just tell me that they need the X and Y 
> data along with the side.  They basically figure out or at least verify 
> the rotation data for themselves.
>
> Is that what you find?  

Yes, they don't get all the info from the design drawings.
They're used to having to figure out some of it from a single hand
assembled prototype, or notes, or photos of a prototype.


It just seems very odd that there is no accepted
> and widely used convention for rotations.  I found info from IPC that 
> says pin 1 in upper left corner is 0 degrees for ICs.  But I've seen 
> nothing that addresses how to spec the bottom side components.

They are assuming you  mean "look at the bottom side of the board
and pin 1 in upper left corner is unrotated."

They do NOT want directions explained as if you
"See through board with X-ray vision".

Besides IPC there's EIA and they're different on package origin points.
Fabs verify these things by looking at them.

John
--
Ecosensory   Austin TX


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