Non-metallic Conductive Posts in MEMS Package Structures
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Solution Overview
Problem
The existing package structures for MEMS chips, particularly those using glass or silicon substrates with copper posts, face challenges in manufacturing complexity, high cost, and internal stress due to significant thermal expansion coefficient differences, leading to poor consistency and stability.
Innovation Solution
A package structure utilizing a non-metallic conductive material with a thermal expansion coefficient similar to the insulating dielectric layer, such as silicon, and a reflow process to form conductive posts within the package cover, along with a filling post and seal rings, to reduce internal stress and simplify the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper posts are used in glass or silicon substrate package structures, then electrical conductivity is achieved, but thermal expansion coefficient differences cause internal stress and poor consistency
Solution Approach 1:
The patent changes the material parameter of the conductive post from traditional metal (copper) to non-metallic conductive material, specifically selecting materials with thermal expansion coefficients matching the substrate (glass: 7-9×10^-6/°C, silicon: 2.5-3.5×10^-6/°C). This parameter change eliminates thermal expansion mismatch and internal stress while maintaining electrical conductivity for I/O connections.
Solution Approach 2:
The patent employs composite material structure where non-metallic conductive material is integrated into the package cover alongside insulating dielectric layers. This composite approach combines materials with complementary properties - conductivity where needed and thermal expansion matching where required - to achieve both electrical function and mechanical stability.
2Ease of manufacture
If traditional metal conductive posts are used, then electrical connection is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces expensive metal conductive posts with cost-effective non-metallic conductive materials that can be formed directly in the package cover during standard manufacturing processes. This substitution reduces material cost and eliminates complex metal deposition, plating, or alloying steps while achieving the required electrical connection function.
Solution Approach 2:
The patent merges the formation of conductive posts with the standard package cover manufacturing process. Instead of adding conductive posts as a separate complex step, the non-metallic conductive material is integrated into the package cover structure itself, combining multiple functions (structural support, electrical connection, thermal matching) into a single manufacturing flow.
3Reliability
If materials with different thermal expansion coefficients are used, then functional requirements are met, but thermal stress causes instability
Solution Approach 1:
The patent systematically changes the thermal expansion parameter of the conductive post material to match the substrate material. By selecting non-metallic conductive materials with specific thermal expansion coefficients (glass-matched: 7-9×10^-6/°C, silicon-matched: 2.5-3.5×10^-6/°C), the patent eliminates thermal stress generation during temperature cycling while maintaining all required electrical and mechanical functions.
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 solution reduces manufacturing complexity and cost while improving the consistency and stability of the package structure by minimizing thermal stress and allowing for a simpler, more efficient production process.
Implementation Method 1
an absolute value of a difference between a thermal expansion coefficient of the conductive post and a thermal expansion coefficient of the insulating dielectric layer is less than or equal to 8×10−6/° C.
Data Source
AI summary
Provided is a package structure, including: an insulating dielectric layer having a first surface and a second surface opposite to each other, wherein at least one first accommodation space running from the first surface to the second surface is formed in the insulating dielectric layer; and at least one conductive post in one-to-one correspondence with the at least one first accommodation space, wherein the conductive post is within the corresponding first accommodation space, a material of the conductive post comprises a non-metallic conductive material, and an absolute value of a difference between a thermal expansion coefficient of the conductive post and a thermal expansion coefficient of the insulating dielectric layer is less than or equal to 8×10−6/° C.; wherein the at least one conductive post comprises at least one first conductive post, two end faces of the first conductive post are flush with the first surface and the second surface, respectively.