Near Hermetic MEMS Packaging via Segmented LCP Seals
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Solution Overview
Problem
Conventional Micro Electro-Mechanical System (MEMS) chip carrier packages using thermotropic liquid crystal polymers (LCP) are only semi-hermetic, which is inadequate for certain applications requiring fully hermetic sealing, as LCP materials are semi-permeable despite being sealed with glass, ceramic, or metal lids.
Innovation Solution
A near hermetic chip carrier package design utilizing two dies formed of substantially impermeable materials like glass, ceramic, or silicon, with a thin thermoplastic substrate of LCP that forms a sealed cavity around the MEMS device mechanism, minimizing exposure and permeability, and incorporating flip chip connections for electrical communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LCP material is used for TE packaging, then ease of manufacture and flexibility are improved, but hermetic sealing capability deteriorates due to semi-permeability
Solution Approach 1:
The package is divided into two distinct sealing interfaces: a first hermetic seal between the LCP substrate and the metal lid, and a second hermetic seal between the LCP substrate and the glass or ceramic body. This segmentation allows each seal to be optimized independently, with the LCP providing ease of manufacture for the lid seal while the glass/ceramic provides superior hermetic sealing where needed.
Solution Approach 2:
The package combines multiple materials with complementary properties: LCP substrate for ease of manufacture and flexibility, metal lid for structural integrity and first hermetic seal, and glass or ceramic body for second hermetic seal. This composite structure resolves the contradiction by allowing each material to contribute its strengths.
2Reliability
If glass, ceramic or metal lid is sealed with LCP, then hermetic sealing is improved, but the package size and complexity increase due to total encasement structure
Solution Approach 1:
The hermetic sealing function is segmented into two distinct interfaces rather than requiring a complete total encasement structure. The first hermetic seal between LCP and metal lid, and the second hermetic seal between LCP and glass/ceramic body, allow hermetic sealing to be achieved through localized seals rather than comprehensive encasement, reducing structural complexity.
3Ease of operation
If LCP substrate is used with window configuration, then electrical conductor accessibility is improved, but sealing surface area is reduced
Solution Approach 1:
The package structure is segmented into sealed interior regions and accessible exterior regions. The window configuration creates designated openings in the LCP substrate that provide electrical conductor accessibility while the remaining portions of the LCP substrate maintain hermetic sealing. This segmentation allows both functions to coexist without compromising either.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves a nearly hermetic seal with significantly reduced permeability, allowing for the use of MEMS devices in applications previously limited by semi-hermetic packaging, while maintaining a compact and efficient package size.
Implementation Method 1
LCP is usually used as the body of the package, the 'bathtub,' to which a glass, ceramic or metal lid is sealed by heating the LCP until it melts and flows to produce a bond between the LCP and the lid
Implementation Method 2
heating the LCP until it melts and flows to produce a bond
Data Source
AI summary
An apparatus and method for a near hermetic chip carrier package having a base die and a lid die each formed of a substantially impermeable material and conjoined by a semi-permeable sheet or tape substrate of only a few thousands of an inch thickness that is formed of two or more thermotropic liquid crystal polymer (LCP) films laminated over a selected number of metal electrical conductors carrying signals into and out of package.