Hello Mrs Perez, and thank you for your fast reply!
I am glad to hear you have a 100% test and I looked through the AN9311. The note deals with the Unibody Package class of the MPX series. My company uses thousands of these circular shaped sensors per year (MPX2100AP and the MPX5xxxDP in different pressure ranges). From the (very small) number of warranty issues on the regarding subassemblies including these sensors, I can confirm the very high quality of the Unibody Packaged MPX Sensors. I hope you are glad to hear.
In my application I want to extend the use of your sensors to a number that manually attached tubing (with or without hose clamp) is no more reasonable. Therefor I dont use the Unibody Package but rather the MPAK. I think the MPXMxxxxGS-Body is designed for o-ring sealing, and that is what I did in my tests. Technical details of the mechanical load are: a shore 70 o-ring, cord thickness 1.5mm, ID 1.5mm, pretension is 0.2mm axially. (For the fast reader: these numbers say, that the mechanical load is low).
Beside that I stressed a few (non leaky) MPXM2010GS sensors (with pretty massive pliers) to an extend that the sensors, including its soldering pads, were pulled off the boards – they stayed absolutely tight.
My last board order included mainly sensors of batches KBF601C and KJN835D, and all 14 leaky sensors are of batch KJN835D - although all sensors experienced the identical assembly process and thermal load of soldering (reflow soldered).
I conclude that you are potentially able to produce almost indestructible sensors and would be very glad to find the reason why I have got one batch with about 20% leaky sensors and 10 batches without a single issue.
The open points are:
1) Is my demand of tightness (<5mm³/min @1kPa) higher than your production test can assure?
2) Even though your test might not be able to identify the issued sensors (with leak rates ~ 10mm³@1kPa), it may be, that your production test is still able to identify delicate batches with finding a surprisingly high share of gross leaky sensors.
3) It might be that the sensors leave your factory in perfect condition, but some batches are very sensitive to e.g. thermal load.
4) I did something wrong.
For 1) – can you give me some details of the production test?
For 2) – does your available data allows you an assertion of typical failure rate (or at least failure rate of batch KBF601C) and failure rate of batch KJN835D?
Might there be a possibility to get sensors from certain batches?
For 3) – It might be possible that the used glue seals in the area between metal plate and cap, but the glue does not reach the edges of the metal plate to seal plastic body to plastic cap. Then while soldering, the difference of thermal expansion coefficients of metal and plastic leads to a detachment of the glue layer and, as a consequence, small leaks will appear. Is there an obligatory processing temperature?
For 4) – Its easy to say but hard to prove that I did everything right. But we are a team of engineers and the recent problems – and its technical details – had been seen by quite a few people so far…
Thanks again in advance!
The picture shows a tightness test of a desoldered pressure sensor, possibily close to your production test. The sensor is submerged in water and pressured with 4kPa. It took a few minutes for the formation of the large bubble. The two small bubbles on the left are remnants from the submersion and did now grow over time.
