I don't have a copy of the new standard.
Just out of curiousity, do they define the
center of a component as the center of
gravity, or the geometric center?
I still don't understand your prediction
that people will be upset by the move
towards a consistent standard. I applaud
it wholeheartedly. My prediction is that
some companies simply won't change.
(speaking from experience)
The problem in my mind is that a vendor
won't know which customers follow the
IPC and which don't. Should we start
adding a fab dwg note that says
"component rotations conform to IPC-7351"?
HA! (just joking)
Jack
(p.s. you put 112 quotation marks in one post,
that's gotta be a record!)
JaMi Smith
<jamismith@SBCGLO
BAL.NET>
Sent by: To
DesignerCouncil To
<DesignerCouncil@ [log in to unmask]
ipc.org> cc
10/26/2004 03:39
PM
Subject
Please respond to Re: [DC] Pin Numbering Question
"(Designers
Council Forum)"
<DesignerCouncil@
IPC.ORG>; Please
respond to
JaMi Smith
<jamismith@SBCGLO
BAL.NET>
Caterpillar: Confidential Green Retain Until: 11/25/2004
Retention Category: G90 -
General
Matters/Administration
The "orientation" of components when packaged in "Tape and Reel" is defined
by
ANSI/EIA-481-C (specifically see Figure 1), and is fairly well followed by
a
majority of manufacturers when packaging a majority, although not all, of
their
components in "Tape and Reel".
The problem here is that there is no specific "standard" on how to "orient"
or
"mount" a "Reel" into a "Pick and Place" machine, and there are in fact
many
different machines that "orient" or "mount" the "Reels" in many different
ways such
that they may "feed" the components in any of the four basic directions.
The problem of "Tape and Reel" mounting or loading orientation in any given
location
in any given "Pick and Place" machine is a matter which has to be
individually
resolved by each individual Manufacturing Engineer, for his individual
"Pick and
Place" machine, which usually taken care of in the programming of that
machine.
Additionally, components also come in "Tubes", "Coin Stacks", "Magazines",
or
"Trays", (much of which is defined by JEDIC JEP95), which packaging
presents similar
problems to the Manufacturing Engineer, respecting their orientation in his
particular individual "Pick and Place Machine".
IPC-7351 is not intended to specify either how components are mounted in
"Tape and
Reel" or "Trays" or any other type of "packaging", or how such "packaging"
is to be
"mounted" or "loaded" into any given automated assembly equipment. This is,
and
always has been, and always will be, the individual responsibility of the
Manufacturing Engineer and or the operator of such equipment.
IPC-7351 is however specifically intended to be a standard for Library
Components
and the orientation of those Library Components, as used in the "design" of
a
Printed Circuit Board, such that respecting "component orientation", all
components
in any given "design" will have a common standard "zero degrees of
rotation" ("zero
rotation"), with respect to the "zero rotation" of the PCB, which is
defined by the
Gerber File and Fabrication Drawing (which should correspond to each other
unless
specifically noted on the Fab Dwg).
IPC-7351 can not dictate how manufacturers package their components, nor
can it
dictate how those packaged components are mounted or loaded into automated
assembly
equipment.
IPC-7351 does dictate that when individual components within "Component
Libraries"
that are defined in accordance with IPC-7351 are utilized, that those
components
will have a "standard orientation", and that any "rotation" of any
individual
component will be based upon a standardized "zero rotation", with respect
to the
"normal" orientation of the PCB itself, such that any Manufacturing
Engineer will
have a "standard component orientation" to rely upon with respect to each
component
on that PCB, such that the Manufacturing Engineer can make such
"compensations" or
"adjustments" as may be necessary with regards to the "mounting" or
"loading" of any
components into any automated manufacturing equipment, and the
"programming" of such
equipment, irrespective of how each component is packaged or oriented
within that
packaging.
The bottom line is this. IPC-7351 defines how components are to be made in
a
"Standard Library", which will among other things insure that all of the
components
within that "Standard Library" follow a standardized orientation based upon
a
standard "zero rotation", which in turn will mean that your data in your
"Pick and
Place File" will be correct and can be relied upon by the Manufacturing
Engineer to
make your PCB quicker and without any errors, and cheaper without any
additional
setup and NRE charges.
IPC-7351 resolves many of the problems that now exist with respect to
component
"land patterns" and "component orientation", such that it will allow the
utilization
of the automation that is already built into most of today's EDA / PCB
Design
Software, as well as most of today's automated manufacturing equipment such
as "Pick
and Place" machines.
While IPC-7351 may not satisfy everyone in every situation, it certainly is
a
monumental step forward in standardizing the "Design" of PCB's such that
the current
avenues of automation can be fully utilized, and new avenues of automation
can be
developed, such as for example, the future standardization of "Pick and
Place" file
"data" and "format".
While on the topic of IPC-7351, I should probably also mention that the
"center" of
a component is chosen as the standard for locating all components, as
opposed to Pin
1 or any other feature, such that the component can be "rotated about its
center".
This will undoubtedly make some people happy, while upsetting others.
JaMi Smith
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