Answering the question really requires reading between the lines.
IPC-610 doesn't allow for "excessive rework". For us, that number is
"something" less than 25% of the components. An exact number depends on
spacing, ease of rework, cost of the unit, even number of
units affected.
IPC-TM-650 2.3.28 sets out guidelines for ionic surface
contamination. Heating the board draws out bromides from FR4, and rework
usually means additional flux, either from cored solder or added straight.
For high mass components with close spacing, I could see allowing only minimal
rework. Then there's the risk of burning a board, lifting pads, etc.
The decision is more a question of economics.
Neil Flatter
TRW Automotive
Process Quality
>>>
[log in to unmask] 10/02/03 12:00AM
>>>
------------------------------
Date: Wed, 1
Oct 2003 08:23:13 -0500
From: Charles Caswell <
[log in to unmask]>
Subject: Re:
How many SMT capacitors / Resistors IPC Spec's allows to
be replaced?
All of the bad
ones.