Multi-layer Stress-isolation Platform for MEMS Die
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Solution Overview
Problem
Existing methods for attaching Micro Electro Mechanical Systems (MEMS) dies to mounting surfaces often result in torque sensitivity and stress transmission, which can adversely affect the performance of MEMS fluid pressure sensors by generating erroneous readings due to mechanical stress.
Innovation Solution
A multi-layer stress-isolation platform is used, comprising a first platform with a first layer of attachment material between the base and the platform, and a second layer between the platform and the MEMS die, with both layers being attached using a re-flow process to minimize stress and torque sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the MEMS die is directly soldered to the mounting surface, then the attachment is simple and strong, but torque sensitivity increases and stress is transmitted to the MEMS die causing measurement errors
Solution Approach 1:
The patent introduces an intermediary platform structure between the MEMS die and the mounting surface. This platform includes a base, an intermediate layer, and a top layer that collectively serve as a mediator to decouple the MEMS die from direct mechanical stress and torque transmitted through the mounting surface, thereby protecting measurement accuracy while maintaining attachment strength.
Solution Approach 2:
The attachment structure is segmented into multiple functional layers: a base layer for mounting, an intermediate layer for stress isolation, and a top layer for die attachment. This segmentation allows each layer to perform its specific function independently, with the intermediate layer specifically designed to block stress transmission while the other layers provide structural support and attachment functionality.
2Strength
If the base is tightly threaded into the housing, then the mechanical connection is strong, but stress is transmitted through the solder to the MEMS fluid pressure sensor causing erroneous readings
Solution Approach 1:
The platform structure acts as an intermediary between the mounted base and the MEMS die. The intermediate layer specifically functions as a stress-isolating mediator that prevents harmful mechanical stress from propagating from the base through the solder joint to the sensitive MEMS sensor, while still allowing strong mechanical connection at the base level.
Solution Approach 2:
Different regions of the attachment structure have different mechanical properties optimized for their specific functions. The base and mounting interface region is designed for strong mechanical connection, while the intermediate layer region is designed with stress-isolating properties, and the top layer region is designed for precise die attachment. This local differentiation of mechanical properties allows simultaneous achievement of strong connection and stress isolation.
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 torque sensitivity and stress transmission, ensuring accurate fluid pressure readings by isolating the MEMS die from mechanical and thermal stresses, thereby enhancing the reliability of MEMS fluid pressure sensors.
Implementation Method 1
heating the first and second solder preform in a re-flow process to attach the MEMS die to the first platform and to attach the first platform to the base
Data Source
AI summary
A multi-layer, stress-isolation platform configured for attaching a MEMS die to a base includes a first platform, a first layer of attachment material between the base and the first platform and attaching the first platform to the base, a MEMS die, and a second layer of attachment material between the first platform and the MEMS die and attaching the MEMS die to the first platform.