FR4 in oil

Most HV and lots of high-current equipment runs in an oil bath and common board materials (phenolic, epoxy-fiberglass) are fine with it. The 'Formica' brand name came from the parent company (GE) substituting their mica insulators with the new material (exactly the same as the cheap phenolic of today's consumer goods).

But, that's 'transformer oil', and hydraulic fluids might be different. The fluid in your car's brakes, for instance, isn't a hydrocarbon (alkane) mix, like mineral oil, but is a heavy alcohol (glycerine). So, you want to get a MSDS for the hydraulic fluid, then look at the chemical composition of the substrate (any substrate supplier can get you all the info you want). "FR4" is, I believe, a fire-resistance rating and is NOT enough info to complete this task. Neither is "G10" which just specifies a glass-density.

Phenolic, epoxy, teflon, ceramic, even porcelainized steel are available as substrates, I'm sure one or more will be suitable.

Am 29.10.2010 16:00, schrieb John Devereux:

FR4 will soak hydrocarbons and it will grow. DOn't know if it will harm a single sensor.

We used Kapton for 16-layer boards to be deployed in ultrasonic pipeline pigs. 1024 ultrasonic channels in a thing that looks like a torpedo. Was quite costly and the prepregs have a short shelf life. (danger of delamination)

\Gerhard

There is not much of a typical pressure and temperature... Can you be more precise? Hydraulic pressures 'typically' run from a few hundreds of PSI to many thousands of PSI. Temps can run from just above ambient to 350 degrees (F).

It would vary with the application, but say up to 400 bar, and 85'C.