Selection of High Strength Encapsulant for MEMS Devices Undergoing High Pressure Packaging

TL;DR

This study evaluates various encapsulant materials for MEMS devices under high pressure, identifying carbon-based epoxy resin as the optimal choice due to its minimal deflection under 100 atm.

Contribution

It introduces a systematic screening method for selecting high-strength encapsulants for MEMS devices in high-pressure packaging.

Findings

Carbon epoxy resin shows deflection <5 μm at 100 atm

Parylene C is acceptable but less optimal

Polyimide is unsuitable for high-pressure encapsulation

Abstract

Deflection behavior of several encapsulant materials under uniform pressure was studied to determine the best encapsulant for MEMS device. Encapsulation is needed to protect movable parts of MEMS devices during high pressure transfer molded packaging process. The selected encapsulant material has to have surface deflection of less than 5 ?m under 100 atm vertical loading. Deflection was simulated using CoventorWare ver.2005 software and verified with calculation results obtained using shell bending theory. Screening design was used to construct a systematic approach for selecting the best encapsulant material and thickness under uniform pressure up to 100 atm. Materials considered for this study were polyimide, parylene C and carbon based epoxy resin. It was observed that carbon based epoxy resin has deflection of less than 5 ?m for all thickness and pressure variations. Parylene C is acceptable and polyimide is unsuitable as high strength encapsulant. Carbon based epoxy resin is considered the best encapsulation material for MEMS under high pressure packaging process due to its high strength.