JinSee Goh:
- In response to your question about how many lifted pads and open traces are
allowed for repair within a printed circuit board.  The answer to the
question is "who cares" and obviously the answer to that question is that
your customer cares.  So, as Jeff Ferry noted, have a conversation with the
customer and find out what he will accept.  As far as I know there are NO
standards or specifications that place limits on how many times a circuit
board can be repaired.  
- Your question raises some additional questions that may shed some light on
how to arrive at an answer.  Q1 Is the circuit board being "repaired" after
field failure or is it a newly manufactured product with defects that need to
be "repaired"?  Q2 Is  this a multilayer board or a double sided board. Q3
You asked "within a printed circuit board".  Does that mean that the defects
are on internal layers of the circuit board, or are the defects on the
surface (top or bottom).  Q4 Are your people trained and/or certified to do
repairs of that nature and are the repairs performed in accordance with a
documented procedure or process?  Q5 Does your customer have the right to
review/approve your repair procedure/process, and if-so, has he done so.
- If the answer to Q1 is that it is a newly manufactured assembly, then you
need to both look at the assembly processes/procedures to assure that damage
is not being inflicted during assembly and also look upstream to the pwb
supplier.  If is a newly manufactured assembly then negotiate with the
customer about how many "repairs" (if any) he is willing to accept.  If the
assembly is being returned for repair after failure in field service, then
your organization needs to closely review the repair techniques used and
define the maximum number of repairs that you feel can be performed before
the reliability of the assembly is reduced to an unacceptable level.   
- Note that in the distant past (when the electronics assembly world was
influenced by Mil-Stds.) there was a generally accepted limit of five (5) as
the number of times that any individual connection could be reworked or
repaired.  The limit of five times was (and is) based on a gross
misunderstanding and misapplication (that I won't go into here) of the
Mil-Std. that controlled pwb assembly (Mil-P-55110).  Note also that the
military organizations spent a lot of time and money training and certifying
their people to perform those repairs with documented procedures under
closely controlled conditions.
- Hope that the above helps.  If additional questions come up please contact
me off line.  Regards, Jim Moffitt, Moffitt Consulting Service, 317/773-5570