Ed Knowles posted an inquiry on verifying the temperature of soldering
irons periodically, saying that he was dealing with an auditor who
"feels it is absolutely necessary for process control." He states
that he hasn't had a problem with bad soldering irons, that previous
attempts to do what the auditor is asking for had been unsuccessful,
and that trained operators should be able to determine whether the
iron was too hot or too cold. This is my response.
1. The function of an auditor is to determine whether what you do
matches what you say you do. If the auditor has strong "feelings"
they are just that: feelings. The issue here is a technical one that
should be capable of being resolved without resort to feelings (except
as a guide, perhaps, to what needs to be investigated). If the audi-
tor has actual data, he should present them. Otherwise, at most, he
can hope that you and he will be able to agree on an experiment that
would resolve the issue.
2. How big a problem are you having with your "uncontrolled" irons?
How much is it costing you? Auditors are rarely responsible for
costs. How much does the auditor think that it would cost to
implement his ideas, and how much money does he think it would save?
Surely he doesn't believe in process control for its own sake?
3. Process control is certainly a laudable goal, but why stop with tip
temperature? Why not also insist on monitoring the time and pressure
being used by the operator? What about tip size and shape? How about
monitoring the time since the tip was used to make a connection, to
make sure it is properly tinned? What about the amount of solder
being added by the operator? And while we're considering the
operator, why not investigate the operator's aptitude, attitude,
degree of concentration on the task at hand, and quality of training?
I suppose this sounds sarcastic, but what I'm leading up to is the
idea that process control can be judged in a different way - namely,
the results of the process. In any process that involves human
beings, it is much better to infer control by examining the product
than by attempting to control all the factors that affect the outcome
(which is impossible, anyway). Each person's soldering is a separate
process. If you don't like what you get from the process used by a
particular human being for whatever reason, then you can deal with
that particular person, including watching to see what he is doing
wrong. Some people shouldn't be allowed to solder product that is
going to be sold to someone else.
Surely you can point to a very large number of connections being made
properly by many people using many soldering irons. As a way to
resolve the issue between you and the auditor, perhaps you could agree
on an experiment to determine the consequences of giving operators
irons that are out of control. If an operator responds properly,
either by using the iron to make acceptable connections or by reject-
ing the iron, then you ought to be able to agreee that that operator's
process is in control, even if the iron isn't, since the operator is
able to respond adequately to the situation. This experiment would be
much simpler and cheaper than trying to show a reduction in solder
defects as a result of using only irons that are temperature-verified.
Gordon Davy
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