Encapsulation of downhole microelectronics and method the same

A method of forming the encapsulated electronic assembly, the method comprising:

• disposing a plurality of electrically non-conductive particles on a substrate which carries one or more components of the electronic assembly;
• introducing a reactive parylene monomer in a vapor form into interstitial spaces among the plurality of the electrically non-conductive particles;
• forming a sealing structure comprising the plurality of electrically non-conductive particles and the parylene binder in the interstitial spaces of the electrically non-conductive particles derived from the reactive parylene monomer, the electrically non-conductive particles comprising hexagonal boron nitride, silicon nitride, or a combination comprising at least one of the foregoing, and the parylene binder locking the plurality of electrically non-conductive particles to each other, to the substrate, and to the one or more components disposed on the substrate;
• disposing a heat sink on the sealing structure opposing the substrate;
• disposing the substrate on a package base;
• and
• coupling the heat sink to the package base.