Ken,
In addition, local fiducials are looked at prior to
placing each component. This would definitely slow down your placement
rate....
Mike McMonagle
Senior SMT Engineer
Telxon Corporation
www.telxon.com <http://www.telxon.com>
-----Original Message-----
From: Lam, Patrick
[mailto:[log in to unmask]]
Sent: Tuesday, October 10, 2000 3:43 PM
To: [log in to unmask]
Subject: Re: [TN] Fiducials and HDI
Hi Ken,
Tomb-stoning is related to the land pattern
used for the component, not to
the local fiducial which is for component
placement.
Patrick Lam
-----Original Message-----
From: Ken Patel [mailto:[log in to unmask]]
Sent: Monday, October 09, 2000 9:28 AM
To: [log in to unmask]
Subject: Re: [TN] Fiducials and HDI
Do you think it will help in reducing
tomb-stoning for many 0402 size
components by having few scattered local
fiducials in the middle of large
board, say 11x17?
re,
ken patel
-----Original Message-----
From: Jim Kittel
[mailto:[log in to unmask]]
Sent: Monday, October 09, 2000 5:08 AM
To: [log in to unmask]
Subject: Re: [TN] Fiducials and HDI
Thanks Poh,
Sounds like good data.
Jim Kittel
-----Original Message-----
From: Poh Kong Hui
[mailto:[log in to unmask]]
Sent: Friday, October 06, 2000 5:33 PM
To: [log in to unmask]
Subject: Re: [TN] Fiducials and HDI
Hi All,
I would like to make some comments. I ever
had cases that some
assembly guys wanted the designer to put
local fiducial when using
50 mil pitch BGA.
We evaluated using the placement machine to
check the balls of the
BGA to perform centering vs using the
component's outline of the
BGA to perform centering, it did not showed
any difference.
However, I would like to say that local
fiducial is rather critical
for the large board size if there is fine
pitch component of 20 mil
pitch or less.
I encountered case that misalignment on 20
mil fine-pitch on the
board size of about 14 X 16 inches. It was
alright once I used
local fiducial.
I would think it depends on situation of
when we need to have local
fiducial or not.
Regards,
Poh
---------------------------------------------------------------------
At 01:05 PM 10/5/00 -0400, Paul Fly wrote:
>From: Paul M Fly
>
>Hi gang,
>
> I have to make a few comments here. The
company I work for is now working
>with a contract
>manufacturer for our PCB assembly needs. We
used to have an in-house
>assembly operation,
>but they went out of business a year or two
ago.
>
> When we had the in-house assembly going
we were required to put local
>fiducials on fine pitch
>SMT parts. Our definition of fine pitch
being less than 25 mils. On a tight
>board getting those local
>fiducials in place could be a real problem,
but we could generally find a
>way to make it work.
>
> Then our in-house group goes out of
business and we are told to use the
>contract manufacturer.
>They want us to put local fiducials on
regular 50 mil pitch BGAs! Steve I
>gotta tell you Jim is 150%
>right, we are being pushed to make boards
smaller but at the same time we
>are getting pressure
>for local fiducials in addition to global
fiducials and thats on parts that
>our own assembly group could
>place two years ago using just the global
fiducials! Sorry to sound like
>I'm venting (well maybe I am a little),
>but this trend I've been seeing is moving
in the wrong direction.
>
> Jim, to answer your question, yes we have
been able to group parts into
>clusters and share fiducials.
>We have been given a dimension, (which I
imagine varys from vendor to
>vendor) that we are told as
>long as the parts all fall within this
distance from the fiducial it is ok
>to share a fiducial with several parts.
>
>Thanks for listening,
>Paul Fly
>
>
>
>
>
>"Stephen R. Gregory" <[log in to unmask]> on
10/05/2000 12:04:35 PM
>
>Please respond to "TechNet E-Mail Forum."
<[log in to unmask]>; Please respond
> to [log in to unmask]
>
>To: [log in to unmask]
>cc: (bcc: Paul M Fly/243609/EKC)
>Subject: Re: [TN] Fiducials and HDI
>
>
>
>
>In a message dated 10/05/2000 9:55:18 AM
Central Daylight Time,
>[log in to unmask] writes:
>
>Hi Jim!
>
>I'd have to agree with Daan. Very rarely,
if ever, have I used local
>fiducials.
>
>As long as there is some good global
fiducials, I've never found the need
>to
>use Locals...this includes placing 15.7-mil
pitch parts and MicroBGA's...
>
>-Steve Gregory-
>
>> Hi Jim,
>>
>> One solution could be to place the local
fiducials underneath the
>components.
>> Another solution: don't use them.
>> And do you really need a 0.150 (inch ?)
keep out area ?
>>
>> Kind regards,
>>
>> Daan Terstegge
>> SMT Centre
>> Signaal Communications
>> Unclassified mail
>> Personal Website: http://www.smtinfo.net
>>
>> >>> Jim Kittel <[log in to unmask]>
10/05 3:25 pm >>>
>> TechNetters,
>>
>> With so much emphasis on reducing
circuit board feature sizes by use of
>> micro BGA's, micro lead frames, micro
vias, etc. the use of local
>fiducials
>> becomes a real burden. For example, our
typical fiducial is a 0.048
>circle
>> with a 0.150 keep out area. This keep
out area is approaching the size
>of
>> flash memories, micro BGA's, 0402 chips,
etc.
>>
>> Has anyone figured out a way to work
around this local fiducial problem?
>Is
>> anyone grouping these parts into some
kind of symmetric clusters? Any
>> ideas?
>>
>> Jim Kittel
>
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