Soldering Station Accuracy out of specification


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Here is an interesting situation:
One of our hand soldering station came back from yearly calibration test and a significant degradation in accuracy.
We are using it in 300 and 350 Celsius. The calibration test results indicate the the nominal value is approximately 50 Celsius less than anticipated; declared accuracy should be about 10 Celsius.

Obviously, the tool will be put out of service, but we need to make an assessment of impact on products that were released to the field.
Obviously, we don't have tractability at that level.

And so my question: how do I justify that the soldered quality is acceptable?
I am thinking to write that the soldering temperature is higher than the melting point of the solder. Is there something better to write? I believe I'm on a grey area... I guess the good news is that the soldering station did not produce 50 Celsius more than anticipated.

Thanks in advance.


Re: soldering station out of spec..

Hi Shimon,

What post-soldering inspection / test would you have in place?
Could you say that the joints produced would have passed inspection?

An iron that is too cold tends to do the job - just that bit slower than optimum, especially if it is a large joint or involves heating a large area/mass.

Could you use the defective iron to produce some samples - perhaps 'worst case' samples (biggest, most difficult etc) then carefully inspect / photograph the joints showing that, even when done with the defective tool they are acceptable?

You could use the standard 'IPC A-610F Acceptability of electronic assemblies' for examples of what is acceptable - it has lots of illustrations of good versus bad joints, and how much below optimum is allowed for different categories of end product (life critical [aerospace etc], important [medical?], non-critical [general products]).

Sidney Vianna

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Re: soldering station out of spec..

And so my question: how do I justify that the soldered quality is acceptable?
in your production line, do the products have monitoring activities, downstream of the hand soldering process? Visual inspection? burn-in? board testing? etc.

If there were monitoring activities done to the product and they passed, this should be reasonable justification for deeming the products acceptable? from a risk based perspective, I would institute a rapid response, in case you see a sudden higher rate of returned defective products.
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Re: soldering station out of spec..

Thanks Pads38 and Sidney,
I'll have to check what we have in terms of process control, but I suspect it's not robust enough to compensate / justify.
Doing a comparative test of 'worst case' is not a bad idea in a perfect world.:)

I'll check what 'IPC A-610F Acceptability of electronic assemblies' has to say.

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