Hi, we have this subsea project where one of the challenges is to install a circuit board on the outside of a retrievable subsea installation (20" pipe), rated for 350 bar (5000 PSI) environmental pressure, so the pressure load will be somewhat cyclic between 0 and 350 bar.
Some other equipment installed on this pipe is embedded in a hard, polyurethane (PUR) potting. So I am thinking to also embed the circuit board into this PUR potting. Since the surrounding potting material is quite hard, ShA 80, and that it is significant differences in the compressibility or bulk modulus of the PCB laminate (FR4) and the potting material, we are concerned that the compression differences between the PCB and the potting material will lead to high stress levels on the components mounted on the PCB. The components on the PCB is a few D2Packs and some 0603 resistors. The size of the PCB is 50x50 mm.
Two obvious alternatives is to put the PCB inside a 1-atm container. or submerge the PCB in some pressure compensated oil container. The reason not to choose one of these is to keep the size and complexity low.
So I am now thinking that this circuit board should first be potted in a form of softer potting material before it is embedded in the harder PUR potting surrounding the 20" pipe. So now I am wondering where to find, or what kind of soft potting material to chose for this purpose? Anny thoughts / experiences / suggestions, anyone?
Thanks..
Br, Rune