Unattached MEMS Pressure Sensor Package Design
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Solution Overview
Problem
Existing MEMS pressure sensor packages face accuracy issues due to packaging stress caused by thermal expansion and mechanical mounting, which traditional stress mitigation methods either increase cost and size or have limitations in consistency and media compatibility.
Innovation Solution
A semiconductor device package design where the semiconductor die is detached from the containment body and connected via flexible wire bonds, allowing for movement within a clearance space filled with a lubricious fluid to mitigate packaging stress, with the wire bonds being the only fixed mechanical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the semiconductor die is directly mounted to the package, then manufacturing cost is reduced and assembly is simplified, but packaging stress significantly impairs measurement accuracy
Solution Approach 1:
The patent introduces an intermediary fluid medium (vacuum, gas, or liquid) between the semiconductor die and package cavity walls. This fluid acts as a stress-decoupling medium that transmits pressure to the diaphragm while isolating it from packaging stress, thereby improving measurement accuracy without requiring complex mechanical stress mitigation structures
Solution Approach 2:
The patent employs a thin diaphragm membrane as the pressure-sensing element that is flexible enough to respond to pressure changes while being isolated from stress by the fluid medium. The diaphragm's flexibility allows it to deform under pressure for accurate measurement while the fluid cushion prevents stress transmission from the package structure
2Measurement precision
If stress mitigation features are added to the package, then pressure measurement accuracy improves ten times, but cost and size of the sensor package increase
Solution Approach 1:
The fluid intermediary provides stress isolation with minimal space requirements compared to traditional mechanical stress mitigation features like thick topping/backing wafers or low-aspect ratio pedestals. This achieves accurate pressure measurement without increasing package size or weight
Solution Approach 2:
The patent extracts the stress mitigation function from mechanical structures and transfers it to the fluid medium. By removing the need for complex mechanical stress relief structures, the package size and weight are reduced while maintaining high measurement accuracy
3Ease of manufacture
If adhesive mounting is used to attach the die to the package, then manufacturing is simplified and cost is reduced, but thermal expansion stress and mechanical mounting stress are imparted on the die
Solution Approach 1:
The fluid medium serves as a stress-decoupling intermediary that allows the die to be mounted with simple adhesives while preventing stress transmission. The fluid cushion absorbs thermal expansion and mechanical mounting stresses, protecting the die from stress while maintaining manufacturing simplicity
Solution Approach 2:
The patent applies preliminary anti-action by using the fluid medium to pre-compensate and counteract thermal expansion and mechanical mounting stresses before they can be transmitted to the die. This protective action occurs continuously, maintaining die reliability while allowing simple adhesive mounting
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 design enhances accuracy and reliability by reducing packaging stress and strain, improving long-term stability and ease of manufacturing, while maintaining mechanical integrity and reducing resonance issues.
Implementation Method 1
A clearance space is defined between the semiconductor die and the interior surfaces. The respective interior surfaces of the interior cavity and the die surfaces are configured and adapted to move relative to one another even when in contact with one another
Data Source
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AI summary
An unattached, contained semiconductor device includes a semiconductor die, for example a MEMS pressure sensor die. The semiconductor die is unattached from the interior cavity of a surrounding containment body in that the semiconductor die is free of adherence to the containment body to mitigate packaging stress and strain between the containment body and the semiconductor die.