MEMS Sensor Bonding Elastic Modulus for Warpage Reduction
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Solution Overview
Problem
Physical quantity sensors with silicon micro electro mechanical systems (MEMS) technology face measurement accuracy issues due to warpage caused by stress from mounting, leading to temperature hysteresis and fluctuation in electrostatic capacitance, which existing methods fail to adequately address.
Innovation Solution
Optimizing the elastic modulus of the bonding material between the sensor element and the substrate to 2.0 GPa < e < 7.8 GPa, with a preferred range of 2.0 GPa < e ≤ 7.5 GPa, 2.5 GPa ≤ e ≤ 7.0 GPa, or 3.4 GPa ≤ e ≤ 6.0 GPa, and ensuring the glass transition temperature is outside the operation range, to reduce temperature hysteresis and stabilize the sensor's temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sensor element is mounted on the substrate using a bonding material, then the sensor element is fixed to the substrate, but stress is applied to the sensor element causing warpage in the container and distortion in the electrodes
Solution Approach 1:
The patent optimizes the elastic modulus of the bonding material to a specific range (2.0 GPa < e < 7.8 GPa) to balance bonding strength and stress relaxation. This parameter change allows the bonding material to provide sufficient mechanical support while simultaneously reducing the stress applied to the sensor element, preventing electrode distortion and maintaining measurement precision.
2Reliability
If heating processing is performed to attach the electronic device on the circuit substrate, then the electronic device is securely attached, but temperature hysteresis is generated in the measurement signal
Solution Approach 1:
The patent specifies a glass transition temperature range for the bonding material (−50°C < Tg < 150°C) that ensures the material maintains appropriate mechanical properties during heating processing and normal operation. This parameter optimization reduces temperature-induced stress and minimizes temperature hysteresis in the measurement signal while maintaining secure attachment.
Solution Approach 2:
The bonding material acts as an intermediary layer between the sensor element and the substrate that mediates thermal stress. By selecting materials with specific elastic modulus and glass transition temperature, the bonding material absorbs and distributes thermal stress during heating processing, protecting the sensor element from direct stress that would cause temperature hysteresis.
3Strength
If the adhesive is applied on the entire surface of the semiconductor element, then the element is firmly attached, but excessive stress is generated in the element
Solution Approach 1:
The patent recommends applying the adhesive at specific locations rather than across the entire surface of the sensor element. This local quality approach concentrates the bonding function at critical attachment points while leaving other areas stress-free, thereby maintaining firm attachment without generating excessive stress in the element.
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 optimized elastic modulus and glass transition temperature settings significantly reduce temperature hysteresis and stabilize the sensor's characteristics, improving measurement accuracy and reliability by minimizing the impact of heating processes on the sensor's physical properties.
Implementation Method 1
when an elastic modulus of the bonding material is e, 2.0 GPa < e < 7.8 GPa
Data Source
AI summary
A physical quantity sensor includes a sensor element (acceleration sensor element) and a substrate (package) to which the sensor element is attached using a bonding material (resin adhesive), in which, when an elastic modulus of the bonding material is e, 2.0 GPa<e<7.8 GPa is satisfied.