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PTH crystal is malfunction when humidity is up to 90%

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PTH crystal is malfunction when humidity is up to 90% | 6 July, 2010

Hi all,

Is anyone used to encounter PTH(plated through hole) crystal component(Not SMT component) become malfunction when the environment humidity is more than 90%? It is happening here...It is very weird that crystal become OK when humidity is back to normal (Around 40%). We simulate the failure in the chamber..

The problem disappear when they clean the PCBA bottom side, especially on the crystal area(Bottom side)....Some people think that this could be flux residue related issue..However, the PCBA look clean..I don't think this is flux residue that lead to this problem..As far as I know if it is related to flux residue, the problem would not go away immediately when the humidity drop to 40% (Temperature is remain the same during the study) unless there is drastic temperature change take place which burn away the flux residue..

However, it is also weird and remain unexplainable as the problem disappear after they clean it as mentioned above..

Note: Our PCBA went through non-clean process..

Anyone has experience the same problem, pls do share with me..I am glad to hear from you..

Thanks, Sean

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PTH crystal is malfunction when humidity is up to 90% | 6 July, 2010


We suggest having the PCB tested for ionic cleanliness. It is conceivable that though the visible flux residue has been cleaned, there is still invisible, yet ionically significant residue in the area of the board/part.

We also suggest ensuring that the issue is not one of trapped flux residues underneath the body of the crystal, which could be shadowed in a cleaning process.

And, yes, we have experienced issues with no-clean flux residues affecting the operation of the circuit.

cheers ..rob

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PTH crystal is malfunction when humidity is up to 90% | 6 July, 2010


I have seen the oscillation frequency change in higher humidity environments. Was doing some data acquisition in a high humitity environment in 1990 using some off the shelf loggers. The data that was collected was incorrect. Found out the crystal was oscillating at the wrong frequency. To fix the problem I cut the can off the leaded crystal. I know sounds like it would get worse but indeed it improved. Moisture was not longer trapped in the crystal can and thus it oscillated at the correct frequency.

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