I am presently reviewing an IPC Video script titled "Through-Hole Rework". 
 In it they state that rework should be done only if and when absolutely 
necessary, that is when the joint is unacceptable.  If it is acceptable, 
even minimally acceptable, leave it alone.  The reasoning is that reworking 
can do more harm than good.

This video is scheduled to begin production in late October, so should be 
available by the end of the year (I would guess).  The technical advisor is 
from PACE and a large number of people contributed input, so I am inclined 
to think it is worth paying attention to.

If you haven't seen any of the IPC training videos, especially the newer 
ones, you will be impressed with the graphics and clarity of explanations. 
 I am and I have seen a LOT of them!  As you can guess, they are available 
through IPC.

Patty
 ----------
From: TechNet-request
To: TechNet
Subject: Re: Through Hole wave Vs. rework
Date: Tuesday, October 15, 1996 8:36AM


Several years ago there was an article that said anytime you "solder sculpt"
a
connection, you degrade the integrity of the pwb by 80%. I believe it had
something to do with trapped moisture and the cosmetics of the joint without 

preheating could cause outgassing. Going back farther than IPC-A-610, Mil 
Std
454 Req 5 also dealt with the acceptability of a partially filled 
connection.

______________________________ Reply Separator
_________________________________
Subject: Through Hole wave Vs. rework
Author:  [log in to unmask] at SMTPpost1
Date:    10/10/96 4:46 PM



     We are building a board that has 8 layers with multiple ground planes,
this

     combined with Entek plus coating and a no clean process is making it
     difficult to optimize the wave solder profile to get 100% fill with a
     fillet on all pins on the top side of the board.

     The IPC A-610 rev B specification calls out 75% fill as being 
acceptable
     (table 4-1, pg. 52) on through hole solder joints. We are pushing our
     subcontractors to get 100% fill with a fillet on each pin.

     Since we are setting our expectations to 100% fill on these solder
joints
     the subcontractor is having to touch up some of the solder joints to
meet
     this requirement (they are touching up the pin from the solder side
letting

     the solder flow through the board to the top)    Thus my question...

     Is a solder joint that is 75% filled over the wave stronger (more
reliable)

     than a solder joint that has been touched up to get to 100% with a
fillet?

     What is the effect to long term reliability of touching up a through
hole
     solder joint?

     I would really like some reference material on this subject if anyone
has a

     source.

     Thanks,

     Mark Weiler
     [log in to unmask]
     512-728-8323

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