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October 2004

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Subject:
From:
Jeffrey Bush <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jeffrey Bush <[log in to unmask]>
Date:
Tue, 12 Oct 2004 08:34:26 -0400
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Planarity within a component with HASL S/B .001" maximum - target
condition is around .4 mils (speaking horizontal HASL).  Immersion
silver or tin will provide planarity less than .1 mils.



Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com	



-----Original Message-----
From: Dacia Super [mailto:[log in to unmask]] 
Sent: Friday, October 08, 2004 7:12 PM
To: [log in to unmask]
Subject: [TN] Coplanarity


All -


I have a question related to surface mount component coplanarity.

Is there a set +/- "window of opportunity" that surface mount gull-wing
leads are allowed to fall within?  Is this covered in a standard
anywhere?

I looked into IPC-A-610 and J-Std - and I found information related to
"toe down" configuration but I did not see any information related to
"toe up" configuration.

I also referenced JESD22 Method B 108.  Interesting guideline - using
the seating place method as a measure of determining coplanarity
deviation.  So, if I am understanding this test method properly, the
user (meaning the manufacturer trying to build with the darn thing)
defines the +/- window?

Background info:
Qualifying new board.  One part on the board is a large transformer with
gull wing leads - 24 leads on either side of the component.  We are
frequently seeing leads bent upwards (towards the heavens) and this is
obviously creating manufacturing frustrations.  However, vendor is
indicating a +/- window of 4 mils - either side.  Doesn't that seem
large? That would be a total of 8 mils of variation.....

So, I was just wondering if there was a criteria out there that we could
reference, to determine whether or not these parts are really
acceptable.


Appreciate the help.

- D

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