Silicon Wafer Sensor Constraint With Through-Holes
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Solution Overview
Problem
Existing sensor assemblies face accuracy impairments due to thermal and mechanical stresses transferred from the package and die attach to the sensor die, with conventional constraints being either ineffective, expensive, or prone to early failure.
Innovation Solution
A sensor assembly constraint comprising a silicon wafer with a passageway and a flexible structure extending from it, which is monolithically formed with beams and trenches, providing flexibility to isolate the sensor die from stresses by being attached to the substrate via a die attach material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a glass constraint is used to limit stress transfer, then the sensor die accuracy is improved, but the manufacturing cost increases and production difficulty increases
Solution Approach 1:
The patent changes the material parameter from glass to silicon, and structurally from a solid constraint to a constraint with through-holes. This parameter change maintains the stress isolation function while enabling compatibility with standard silicon wafer fabrication processes, thereby reducing manufacturing difficulty and cost.
Solution Approach 2:
The constraint structure incorporates through-holes penetrating the silicon wafer, creating a porous configuration. This porous design reduces the constraint's stiffness, allowing it to flex and absorb thermal and mechanical stresses effectively, while maintaining ease of manufacture using standard semiconductor fabrication techniques.
2Measurement precision
If a glass constraint is used to limit stress transfer, then the sensor die accuracy is improved, but the manufacturing cost increases
Solution Approach 1:
The patent changes the material parameter from glass to silicon, and structurally from a solid constraint to a constraint with through-holes. This parameter change maintains the stress isolation function while enabling compatibility with standard silicon wafer fabrication processes, thereby reducing manufacturing cost.
Solution Approach 2:
The silicon wafer constraint can be manufactured using standard, cost-effective silicon fabrication processes that are already widely available in the semiconductor industry, replacing expensive glass constraints with a more economical silicon-based solution.
3Ease of manufacture
If other suggested constraints are used, then the manufacturing cost is reduced, but the bonding strength decreases leading to early failure
Solution Approach 1:
The patent changes the material parameter to silicon, which has superior mechanical properties and bonding characteristics compared to alternative materials. This enables strong, reliable bonding to both the sensor die and substrate while maintaining cost-effectiveness through standard fabrication processes.
Solution Approach 2:
The constraint structure combines silicon material with a specific geometric configuration (through-holes), creating a composite structure that achieves both strong bonding capability and stress isolation function, resolving the contradiction between bonding strength and cost.
4Measurement precision
If a rigid constraint is used to limit stress transfer, then the sensor die accuracy is improved, but the constraint cannot accommodate thermal expansion differences
Solution Approach 1:
The through-holes create a porous constraint structure that reduces overall stiffness, allowing the constraint to flex and accommodate differential thermal expansion between the sensor die, constraint, and substrate while maintaining stress isolation benefits.
Solution Approach 2:
The constraint transitions from a rigid, static structure to a dynamic, flexible structure with through-holes that can deform elastically. This dynamic capability allows the constraint to adapt to thermal and mechanical stress variations while continuing to protect the sensor die.
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 flexible constraint effectively limits stress transfer, enhancing the accuracy and consistency of the sensor die across a range of temperatures and applications, while maintaining strength and compatibility with various die attach materials.
Implementation Method 1
The flexible structure extends from the second side... providing flexibility to isolate the sensor die from stresses
Data Source
AI summary
A constraint for a sensor assembly includes a silicon wafer and a flexible structure. The silicon wafer has a first side, a second side opposite to the first side, and a passageway extending through the silicon wafer from the first side to the second side. The first side is a continuous planar surface except for the passageway. The flexible structure extends from the second side.