Well, SOMEONE is missing the point.... <grin>
Yes, you can create stuff any way you like, but since he has a CHOICE what
orientation to build them, and since it doesn't matter to the CAD operator
what orientation they are, it seems logical and intelligent to wonder if the
ASSEMBLER might have a preference, eh?
If you build a library component and plop it into your design, and don't
rotate it, at the end of the design cycle when you create your pick and
place files for the assembler, that component will be listed as zero degrees
rotation, right? If you build a SMT resistor vertically, no matter how you
rotate it in the database, the rotation in the data file will be useless
because SMT resistors are packaged horizontally on a reel. The operators
know this, so they check rotations before they start, but wouldn't it be
nice if we could get MOST OF THEM right in the library? Sometimes you can't
because some ICs come on reels horizontally, and some come packaged in
sticks and come out vertically, so you have to modify some rotations no
matter what. But all I am saying is that if you know what your vendor is
using, why not make it easy for him and TRY to supply good data?
Still, you can never win... here at Intel we are asked NOT to place
components in the same orientation as they come on the reel, because the
type of pick-and-place machine we use rotates the head 180 degrees as it is
moving from the reel to the board, and then will have to rotate another 180
to get back to the same orientation, which wastes a whole tenth of a second
(perish the thought!). So, you can never learn enough in this business,
right?
Onward thru the fog, Jack
-----Original Message-----
From: Uptain, George [SMTP:[log in to unmask]]
Sent: Tuesday, September 22, 1998 12:29 PM
To: [log in to unmask]
Subject: Re: [DC] PCB Footprint standard for smt polarised
components?
I think you are is missing the point (although
[log in to unmask] is the only one that can say) To me he seems to be
asking how he should create the library part. The answer to that is, IT
DON'T MATTER. It can be rotated any which way in most every CAD system I
know of when it's placed on the board. THEN assembly and fabrication rules
apply. But not in library part creation.
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