Effect of perfluorocarbon liquids on the silicone gel of the MPXV7205. Why can't I get real tech support like from a real company?
We do not recommend the MPXV7025 to become in direct contact with any kind of liquid substance or corrosive gases which would damage the gel and cause the sensor to become out of specification.
The strain gauge and the electronic circuitry for calibration and compensation are protected by a nitride layer but the aluminum bonding pads which provide electrical connections between the leadframe and the gauge are not protected, in order to make the bonding feasible. The complete die is also protected with a silicone gel. This gel is not fully hermetic, although we use much better gel for our newer types of pressure sensors, water or any other fluid can penetrate the gel and can reach the die. When the sensor die is in contact with water e.g., oxydoreduction reactions between Al/Al3+ and water start as soon as the sensor is biased. After some working hours, or maybe days, the aluminum pad of the supply pin is destroyed, so that an open circuit on the Vcc pin occurs. This is an aluminum corrosion phenomena. But the corrosion phenomena is stopped when the sensor supply voltage is switched off. There are also some other failure causes like galvanic corrosion, but the Mean Time To Failure (MTTF) due to these other causes much longer than the MTTF caused by electrocorrosion of the Vcc pad. Therefore electrocorrosion is the major failure cause, and they are permanent.
I would also recommend taking a closer look at our AN3728 about media compatibility.
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I hope it helps.
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