Semiconductor Strain Sensor with Variable Thickness Plate
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Solution Overview
Problem
Semiconductor strain sensors face limitations in measurable strain range due to chip breakage, and increasing base rigidity leads to bonding layer stress and reliability issues.
Innovation Solution
A mechanical quantity measuring device with a semiconductor chip and a plate member where the plate member has varying thickness regions to reduce strain transmission and prevent bonding layer separation, featuring a metal film on the semiconductor chip for improved bonding and a flexible wiring unit for efficient signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the semiconductor strain sensor is used to measure large strain quantities, then the measurement range is expanded, but the semiconductor chip breaks due to exceeding its breaking strength
Solution Approach 1:
A base structure is introduced as an intermediary between the semiconductor strain sensor and the object being measured. This base absorbs and distributes the mechanical stress, preventing direct transmission of large strains to the fragile semiconductor chip while still allowing accurate strain measurement through the sensor.
Solution Approach 2:
The measurement system combines the semiconductor strain sensor with a base structure made of different material properties. The composite structure leverages the high sensitivity of the semiconductor sensor and the mechanical strength of the base material to achieve both extended measurement range and chip protection.
2Reliability
If the rigidity of the base is increased to reduce strain transmission to the semiconductor chip, then chip protection is improved, but stress concentrates in the bonding layer causing separation
Solution Approach 1:
The base structure incorporates localized rigid portions positioned directly beneath the semiconductor strain sensor to provide targeted support and strain distribution. These local rigid regions protect the chip without creating excessive overall rigidity that would cause bonding layer stress concentration.
Solution Approach 2:
The base is divided into multiple regions with different rigidity characteristics. Rigid portions are segmented and positioned strategically under the sensor, while other areas of the base have lower rigidity to allow stress distribution and prevent bonding layer separation.
3Ease of manufacture
If a uniform thickness plate member is used, then manufacturing is simplified, but strain distribution is uneven causing both chip breakage and bonding layer separation
Solution Approach 1:
The plate member features varying thickness with locally optimized regions. Thicker regions are positioned under the semiconductor sensor to provide enhanced support and strain distribution, while thinner regions reduce overall mass and stress. This non-uniform structure is designed to create optimal strain distribution patterns.
Solution Approach 2:
The thickness parameter of the plate member is varied spatially to optimize performance. By changing the thickness parameter across different regions of the plate, the invention achieves improved strain distribution and chip protection while maintaining manufacturing feasibility through standardized fabrication processes.
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 enhances connection reliability and expands the measurable strain range while preventing chip breakage and bonding layer separation, allowing for stable strain measurement beyond previous limits.
Implementation Method 1
a semiconductor chip including a plurality of piezoresistive elements formed on a front surface of a semiconductor substrate
Data Source
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AI summary
A mechanical quantity measuring device (semiconductor strain sensor) has a semiconductor chip including a plurality of piezoresistive elements formed on a front surface of a semiconductor substrate, a lead wire unit electrically connected to a plurality of electrodes of the semiconductor chip, and a plate member joined to a rear surface of the semiconductor chip. Further, the plate member includes a first region facing the rear surface of the semiconductor chip and a second region provided adjacent to the first region, and a thickness of the plate member in the first region is made larger than a thickness in the second region.