There is no "standard" JEDEC marking for where the pin 1 is oriented.
The prime reason for this really goes back to a "war" that was waged
between TI and National Semi some 30 years ago. TI originally wanted a
small indentation; however, because of a mold mark left behind, National
had patented this (under the guise of "If you can't fix it, feature
it."). TI then was left with the chamfer; as new players came online,
everyone took out one or the other's license., depending on their
particular alignments. Then in the late 1960's, Fairchild Camera &
Instrument (later to becaome Fairchild Semicondutors) did the industry
one better- it needed a commercial package reverse bent for a special
application-this became the "die down" package- but the markings were
all on the side of the board.
Anyway, with JEDEC struggling with the breadth of package issues on its
plate, the least of its worries is where pine 1 is on any given package.
In all fairness to JEDEC, however, in JES95 it does indicate a "index
corner", though this may not be where pin 1 is...
Within a given package type and pin count, however (TSOP, PDIP, etc)
there is an accepted practice within the industry as to where pin 1 is-
this isn't because of any altruism on the industry's part- it's because
the tool makers got sick and tired of customizing toolsets for everyone-
they are the folks that actually enforce the industry.
Anyway, there's my 2 cents worth adjested for inflation out here on the
left coast...
> Bill Davis, Ph.D.
> Diamond Multimedia Systems
> Senior Scientist
> Tel. 408.325.7868
> Cell. 408.888.5650
> e-mail: [log in to unmask]
>
>
-----Original Message-----
From: Lustig, Steven K.. [mailto:[log in to unmask]]
Sent: Friday, May 21, 1999 8:39 AM
To: [log in to unmask]
Subject: Re: [TN] TopMark Orientation on ICs
All I know is that we use an Analog Devices IC with no obvious top mark
orientation (supposedly there is a very subtle chamfer along one side -
try
inspecting lots of those!). In fact, they have a box with a triangle in
it
that looks deceptively like an arrow (as if it could be pointing at pin
1)
which is just part of their text and is not pointing to the pin 1 side.
Yes, we put them down in the wrong orientation on the prototype boards.
I've had to add a view to my assembly drawing indicating the proper
orientation of that part relative to the text to make sure we put it
down
right.
A nice white dot or indentation sure would be nice!
-Steve
Steven K. Lustig
Process Engineer
EMS Technologies, Inc.
Norcross, GA
(770) 263-9200 x4714
[log in to unmask]
> ----------
> From: Tomaso Mordha[SMTP:[log in to unmask]]
> Sent: Friday, May 21, 1999 11:01 AM
> To: [log in to unmask]
> Subject: [TN] TopMark Orientation on ICs
>
> Hello Technetters,
>
> Many thanks for the help with AutoCAD to dot.PDF conversion.
>
> Here is another item which puzzles me ....
>
> Is there a recognized standard for orientation of top-mark with
respect to
> the
> pin-1 corner of the package (or ball A1 in the case of BGAs)?
>
> What is the spec?
>
> If it exists why do some vendors not comply with it?
>
> Again thank you for your past help,
>
> Tom
>
> ____________________________________________________________________
> Get free e-mail and a permanent address at
http://www.netaddress.com/?N=1
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV
1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in the body:
> To subscribe: SUBSCRIBE TechNet <your full name>
> To unsubscribe: SIGNOFF TechNet
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
> section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################
>
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV
1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
################################################################
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################
################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe: SUBSCRIBE TechNet <your full name>
To unsubscribe: SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################
|
