MEMS Sensor Lid Electrode Taper for Stable IC Bonding
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Solution Overview
Problem
The existing Si-MEMS acceleration sensors face instability in adhesion between the lid and the IC due to level differences caused by electrode thickness variations, leading to stress and bias output fluctuations.
Innovation Solution
The physical quantity sensor design features a lid with an electrode that tapers in thickness from the through-hole opening, reducing level differences and improving bonding stability by using a mask to form a gradually decreasing metal layer, which is sealed and bonded with a circuit element using an adhesive material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrode is provided at the peripheral edge of the through-hole at the surface of the lid with uniform thickness, then the electrode provides sufficient mechanical strength and electrical conductivity, but a level difference occurs due to the thickness of the electrode, causing partial unstable adhesion and stress in the bonded part
Solution Approach 1:
The electrode thickness is made non-uniform, with a gradually decreasing thickness from the through-hole opening toward the peripheral edge. This local variation in thickness eliminates the level difference that caused unstable adhesion, while maintaining sufficient mechanical strength and electrical conductivity in the bonded region.
2Reliability
If the electrode thickness is reduced at the peripheral edge to eliminate level difference, then adhesion stability improves, but the mechanical strength of the electrode may be compromised
Solution Approach 1:
The electrode thickness parameter is gradually changed from the through-hole opening toward the peripheral edge, creating a tapered profile. This gradual parameter change ensures that the electrode maintains sufficient strength while eliminating the level difference that caused bonding instability.
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
This configuration enhances the stability of the bonding between the lid and the circuit element, reducing stress and fluctuations in the bias output signal, thereby improving the sensor's performance and reliability.
Implementation Method 1
a circuit element bonded to a surface of the lid via an adhesive material
Implementation Method 2
a through-hole, which pierces through the lid from the housing space to the surface on the opposite side and is sealed by a sealing member
Data Source
AI summary
A physical quantity sensor includes a physical quantity sensor element including a lid joined to a substrate to define a housing space in the inside and a physical quantity sensor element piece housed in the housing space and a circuit element bonded to the outer surface of the lid via an adhesive material. In the lid, an electrode is provided to extend from an inner wall of a through-hole, which pierces through the lid from the housing space to a surface on the opposite side of the side of the physical quantity sensor element piece and is sealed by a sealing member, to a peripheral edge of the through-hole at the surface on the opposite side. In a sectional view, thickness of a region at the peripheral edge of the electrode is smaller at the opposite side of the side of an opening of the through-hole than the opening side.