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August 2007

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Subject:
From:
"Whittaker, Dewey (EHCOE)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Whittaker, Dewey (EHCOE)
Date:
Mon, 6 Aug 2007 13:28:03 -0700
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Victor,

Nothing, but the hole truth.

 A plated -through hole (PTH) dimension in relationship to aspect ratio
and needed clearance to the inserted lead is a multi-faceted dynamic. Is
your concern the ability to form an acceptable solder joint or merely to
be able to insert the lead in the PTH. The true position relationship of
the PTHs on the printed board(PB) to the part geometry tolerances
(single pin, multiple rows, round vs. rectangular, etc. ) and the
placement accuracy of the equipment, as well as whether the part is
clinched or preformed for retention, will have an impact on insertion
capability. This is minimally impacted by thickness. 

PB thickness and/or aspect ratio and the clearance between the lead and
barrel of the PTH will have an impact on the solder to sufficiently wet
and fill the PTH through capillary action. This can be offset by
equipment selection (dual wave, jet wave) and processing parameters.

This is really simplifying it, but given all things being relevant; the
finished PTH size should be 0.014 of an inch over the nominal lead
dimension. If this creates a non-standard drill size, err on the
conservative side by basing it more towards the max lead dimension

Dewey

________________________________

From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Monday, August 06, 2007 11:48 AM
To: [log in to unmask]
Cc: [log in to unmask]; [log in to unmask]; [log in to unmask];
Whittaker, Dewey (EHCOE); [log in to unmask];
[log in to unmask]; [log in to unmask]; [log in to unmask];
[log in to unmask]
Subject: Hole drill-Finish size versus min-max lead diameter,

 

Fellow TechNetters:

   Please bear with me as I have followed this string of e-mail for some
time and am not sure if a straight forward response was provided.  II
have reviewed IPC-2222 sec 9.2.2 and IPC-2221 sec 9.0.   I still have no
clue

Is there a quick reference calculator that permits an individual to
select and enter component lead dimensions, board thickness and receive
a recommended plated/finish hole size and vice-a versa.   As a lab
analyst I can only provide destructive analysis measured dimensions and
not nominal.

Victor,


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