Patterned Adhesive Stress Decoupling for MEMS Pressure Sensors
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Solution Overview
Problem
MEMS pressure sensors face challenges due to non-linearity induced by large deflections and temperature differences, leading to undesirable sensor output drift, particularly in ultra-sensitive applications where stress changes from carrier bending and moisture uptake are significant.
Innovation Solution
A semiconductor package design featuring a stress-sensitive die attached to a support using a patterned adhesive on the backside, with non-contiguous regions such as stripe-shaped adhesive areas, which acts as a stress decoupling mechanism to prevent bending moments from being transferred to the pressure sensor, maintaining a low profile without increasing the package height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solid layer of adhesive is used to attach the die to the support, then the die is securely attached, but bending moments are transferred to the pressure sensor causing stress-induced errors
Solution Approach 1:
The adhesive layer is segmented into multiple non-contiguous regions rather than forming a continuous solid layer. This segmentation allows the die to be securely attached while creating compliance zones that prevent bending moments from being transferred to the pressure sensor, thus resolving the contradiction between attachment strength and sensor accuracy.
Solution Approach 2:
Different regions of the die backside have different adhesive coverage - some areas are fully covered while others are intentionally left uncovered. This local quality variation provides both secure attachment in covered regions and stress relief in uncovered regions, simultaneously achieving strong attachment and maintaining sensor accuracy.
2Strength
If the adhesive covers the entire backside of the die, then the die is firmly attached to the support, but the package height increases
Solution Approach 1:
The adhesive is applied in segmented non-contiguous regions rather than as a complete continuous layer. This segmentation reduces the overall adhesive volume and die attachment height while maintaining sufficient attachment strength, thereby reducing the total package height without sacrificing attachment quality.
3Reliability
If the adhesive is applied in non-contiguous regions, then stress is decoupled from the pressure sensor, but the attachment area is reduced
Solution Approach 1:
The die backside is treated with local quality variation where specific regions receive adhesive coverage while others remain uncovered. The covered regions provide secure attachment, while the uncovered regions provide stress decoupling. This local differentiation allows the system to simultaneously achieve both strong attachment and effective stress decoupling.
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 approach effectively reduces stress-induced errors, maintaining accurate and stable pressure readings across varying temperatures and pressures, enhancing the reliability of MEMS sensors in applications like wearable and consumer devices.
Implementation Method 1
adhesive can act as a roller bearing, preventing bending moments from being transferred to the pressure sensor
Data Source
AI summary
A die attachment to a support is disclosed. In an embodiment, a semiconductor package includes a support and a die attached to the support by an adhesive on a backside of the die, wherein the die includes a capacitive pressure sensor integrated on a CMOS read-out circuit, and wherein the adhesive covers only a part of the backside of the die.