I do a little repair work for my friends on the side and I was recently working on a 148 Mhz transceiver.
The final power module is bad so, I successfully removed the lid to this power module and found the 2 RF transistors in side how ever, these units do not have any encapsulated case but are exposing the silicone wafer and electrical connecting wires. I noticed the use of a compound injected into the body of these units which had debris in it, most likely from when I was removing the lid. Under the microscope with my precision tweezers I removed the debris and noticed the compound is still solidified.
My question I guess is, what is this compound and how does it stay in place ? I can visualize the unit being stored up side down and having this compound oz out how ever, this apparently isn't the case and I know this unit has had some abuse being placed in lots of different angles for long periods of time.