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time guarding against changes that could have
detrimental effect on the process. Redundant
TPCs must also be avoided as there is no need
to expend resources on a method that has been
proven unsuccessful in the past. Obviously, pro-
cess engineering, engineering or whatever func-
tion owns the shop’s processes, should manage
this. Each shop is different; however, my only
caveat would be to have a single entity oversee-
ing the process. I would also highly recommend
making this a stand-alone procedure/work in-
There are three main components
of a solid system, the temporary pro-
cess change form, the temporary pro-
cess change log, and the quality assess-
ment phase. My position affords me the
unique opportunity to evaluate the best
and brightest in the PCB world, but on
the other hand I also get to observe the
opposite end of the evolutionary scale.
It continues to amaze me, ISO notwith-
standing, how many times I run across
controlled procedures that have things
crossed off and/or changed, or process-
es that only the operator knows has been
“unofficially” changed. A few companies
have even accounted for this by includ-
ing in their document control procedure
that handwritten changes are allowed!
Although this loophole may satisfy a Bar-
ney Fife ISO auditor, that would require
banishment to the “not ready for prime
time” file in my book. Figure 1 details the
process flow for a TPC program.
TPC Form
A simple form should be devel-
oped—either electronic or paper will
work fine—that provides the basic infor-
mation needed to implement and track
the change. It should include sections
that describe the change, any chemical
changes, the reason for the change, and
the results (implemented or denied).
A TPC can be defined as “Any process
change that deviates from a standard op-
erating procedure (SOP) for a short peri-
od of time.” The change could be pro-
cedural, raw material, or supplier/brand-
related, and the “short period of time” must be
defined. Anyone should be allowed to submit a
TPC for review and approval, however utilizing
the organization’s various Improvement Teams
for this activity increases buy-in and can be an
effective filter for unworthy ideas. If the change
is global for the process, it should be attached
to the appropriate procedure (either paper or
electronic). If the change is limited to a specific
lot(s), it should be attached to the appropriate
process travelers. In either case, all appropri-
ate operators should be notified of the change,
again improvement teams are a perfect media
for this communication.
A method for managing TPCs needs to be
developed, and a simple spreadsheet log is the
most effective. Building a level of intelligence
into the TPC numbering system (such as em-
bedding the procedure or department number)
will allow historical analysis of successful and
unsuccessful TPCs for any process. Regular re-
view of open TPCs and status is critical to a suc-
cessful program.
Quality Assessment Phase
The second mission-critical aspect of a TPC
program is the quality assessment phase, where
a decision will be made to either permanently
incorporate the change into the process or deny
it. This decision needs to have the cross-func-
tional approval from the department/improve-
ment team, engineering, operations and quality
at a minimum. This decision needs to be docu-
mented (TPC form) and as data driven as possi-
ble, i.e., yield & rework, material/labor cost re-
ductions, etc., over the TPC period. If a discrete
lot(s) is being evaluated, the quality assessment
form can be attached to the process traveler(s)
to gather the appropriate data as mentioned
above. Global TPC’s affecting continuous pro-
duction will require a systemic tracking method
over the course of the time period.
This should be easily accomplished, but get-
ting to the decision point is where many often
stumble. As mentioned earlier, setting a defined
time frame for the TPC evaluation is critical. In
most cases, 30, 60, or 90 days are sufficient to
execute a meaningful evaluation of a process
change. It is a strongly recommended best prac-
tice to close out as many of the open TPCs as
possible prior to a major customer or registrar
audit. Closure also means revising the appropri-
ate SOP to include any successful TPCs, and re-
training operators when required. Don’t be con-
cerned with having a history of frequent TPCs;
if the quality system is operating correctly this
activity should be encouraged. In the quest for
continuous improvement, change is good.
I’ll end this column with a quote about
change that seems appropriate in the volatile
world of printed circuit board manufacturing. It
is from my good friend and quality guru W. Ed-
wards Deming, who said, “If you can’t describe
what you are doing as a process, you don’t know
what you’re doing.” PCB
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