Encapsulated MEMS Structures with Epoxy Corrosion Protection
Solution Overview
Problem
MEMS devices are vulnerable to damage from environmental factors such as moisture and debris, which can compromise their longevity and functionality.
Innovation Solution
A MEMS device design that includes a substrate with a semiconductor die and a four-sided structure sealed by epoxy, forming a sealed cavity with a glass member to protect vulnerable components, using a composition of at least 80% silica and a coefficient of thermal expansion below 25 to prevent mechanical and thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MEMS device uses a corrodible material structure to form a sealed cavity, then the sealing capability is improved, but the device becomes vulnerable to corrosion from environmental factors
Solution Approach 1:
The patent uses a composite material system consisting of a corrodible metal stack (providing sealing capability) combined with an epoxy encapsulant containing at least 80% silica (providing corrosion resistance). This composite structure allows the metal stack to form effective seals while the epoxy protects it from environmental corrosion, resolving the contradiction between sealing performance and corrosion vulnerability
Solution Approach 2:
The epoxy encapsulant acts as an intermediary protective layer between the corrodible metal stack and the harsh external environment. This intermediary substance provides the necessary protection against corrosion while allowing the metal stack to maintain its sealing function, effectively mediating between the conflicting requirements of seal integrity and corrosion resistance
2Stability of the object's composition
If the epoxy contains at least 80% silica with a coefficient of thermal expansion below 25, then thermal stress is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise compositional parameters for the epoxy (at least 80% silica content) and thermal properties (coefficient of thermal expansion below 25) to optimize thermal stress resistance. By carefully controlling these material parameters, the invention achieves reduced thermal stress while the resulting performance benefits outweigh the increased manufacturing precision requirements
Data Source
AI summary
In examples, a micro-electromechanical (MEMS) device comprises a substrate and a semiconductor die coupled to the substrate and including circuitry formed therein. The semiconductor die also includes a bond pad coupled to the circuitry. The MEMS device includes a structure extending away from the semiconductor die and having four sides, with the structure comprising a corrodible material. The MEMS device includes an epoxy contacting outer surfaces of the four sides of the structure and over the corrodible material.