Semiconductor Load Sensor Packaging for Uniform Force Transfer
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Solution Overview
Problem
High-range semiconductor load sensor devices face challenges in applying uniform loads to micromechanical sensing structures within packages, leading to reduced measurement accuracy and maximum load capacity due to local force concentrations and stress-related issues caused by packaging materials with different thermal expansion coefficients.
Innovation Solution
A high-range semiconductor load sensor device design featuring a micromechanical sensing structure with a deformable covering layer and a lateral spacer element, both made of materials with compatible Young's moduli, to distribute loads uniformly and decouple stresses, preventing local force concentrations and ensuring homogeneous contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a package is used to protect the micromechanical sensing structure, then protection from environmental disturbances and mechanical strength are improved, but uniform load application is worsened due to local force concentrations
Solution Approach 1:
A deformable layer is introduced as an intermediary element between the package and the micromechanical sensing structure. This layer serves as a mediator that transforms the non-uniform load from the package into a uniform distributed load on the sensing structure, thereby resolving the contradiction between package protection and measurement precision
Solution Approach 2:
The deformable layer changes its mechanical parameters (shape, thickness) in response to applied load, allowing it to adapt and distribute forces uniformly across the sensing structure surface, thus maintaining measurement precision while preserving package protection
2Strength
If packaging materials with different thermal expansion coefficients are used, then package protection and structural integrity are improved, but stress-induced deformations are worsened
Solution Approach 1:
The patent explicitly addresses thermal expansion by selecting materials with compatible thermal expansion coefficients for the deformable layer and the sensing structure. This prevents differential thermal expansion from inducing harmful stresses and deformations, thereby maintaining structural integrity while ensuring stability
Solution Approach 2:
The patent employs homogeneous material properties (matching thermal expansion coefficients and compatible Young's moduli) across the package-sensing structure interface. This material homogeneity eliminates thermal mismatch stresses and ensures stable, stress-free operation across temperature ranges
3Measurement precision
If the deformable layer has low Young's modulus for compliance, then uniform load distribution is improved, but load transfer efficiency is worsened
Solution Approach 1:
The patent optimizes the Young's modulus parameter of the deformable layer to achieve a balance: low enough to enable uniform load distribution through deformation, but not so low that it prevents adequate load transfer to the sensing structure. The specific modulus value is selected based on the sensing structure's mechanical properties
4Reliability
If the covering layer is made of material with Young's modulus similar to silicon, then stress decoupling is improved, but material selection flexibility is worsened
Solution Approach 1:
The patent specifies that the covering layer should have a Young's modulus similar to silicon (the sensing structure material). This material homogeneity ensures stress decoupling by preventing stress concentration at interfaces, thereby improving reliability while constraining material selection to silicon-compatible materials
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 enables accurate and reliable high-range load measurements by ensuring uniform force distribution and stress decoupling, enhancing the stability and reliability of the sensor device while preventing damage from excessive loads.
Implementation Method 1
a deformable covering layer... to distribute loads uniformly and decouple stresses
Implementation Method 2
sensing elements are formed, for example piezoresistors, adapted to deform upon application of the load thus generating a variation of electrical signal
Implementation Method 3
load measurement may be implemented by the capacitive technique... form a capacitor element with a capacitance that is variable according to the applied load
Data Source
AI summary
A device includes: a micromechanical sensing structure configured to provide an electrical detection quantity as a function of a load; and a package enclosing the micromechanical sensing structure and providing a mechanical and electrical interface with respect to an external environment. The package includes a housing structure defining a cavity housing the micromechanical sensing structure; and a package coating that coats, at least in part, the housing structure, the package coating including a mechanical interface configured to transfer, in a uniform manner, the load on the housing structure and on the micromechanical sensing structure, wherein the housing structure includes a deformable layer interposed and in contact between the micromechanical sensing structure and the package coating, and wherein the deformable layer defines a mechanical-coupling interface.