Rework or scrap? the risk is usually assessed by weighing in the laminate
type (PI, FR-4, flex etc), design, board stack-up, components in vicinity
of rework site and time/temperature required for each rework (including
preheat).


Any guidelines regarding the number of allowable reworks are going to be
specific to a design/material combination, tricky to extrapolate that
guidance into a standard…rework risk assessment needs to analyze all
factors and be better understood with solid research.  Most companies say a
site can be reworked 2 or 3 times (assuming high Td/Tg PI...$$$).



On Wed, Mar 28, 2018 at 1:40 PM, Nutting, Phil <[log in to unmask]>
wrote:

> Respected colleagues,
>
> I was just asked a question to which I could not put a number.
>
> In the case of needing to fix a circuit board "right now" to fill the
> income stream there should be a logical point at which the reworks have
> become too extensive for production boards beyond the "right now" need and
> the board should be revised to eliminate the reworks.
>
> Is there an IPC or MIL standard that suggests a limit on the number of or
> amount of rework allowed on a circuit board before it should be revised?
>
>
> Phil Nutting  |  HVP Senior Development Engineer   |  Excelitas
> Technologies Corp
>
> Lab: +1 978.224.4332   |  Office: +1 978.224.4152
> 35 Congress St, Salem, MA  01970 USA
> [log in to unmask]<mailto:[log in to unmask]>
> www.excelitas.com<http://www.excelitas.com/>
>
>
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-- 
Bhanu Sood
Tel: (202) 468-8449