Gel Encapsulation Baffle for Semiconductor Sensor Stability
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Solution Overview
Problem
Semiconductor devices face a challenge in packaging, where low modulus gels used for encapsulation are prone to movement under mechanical stress, leading to reliability issues and potential wire breaks, while higher modulus gels required for stability can induce stress on wire bonds and impact device performance.
Innovation Solution
Incorporating a structural feature such as a fine mesh fabric, random matrix fibrous mat, pre-formed film, posts, or baffles within the gel cavity to reduce gel movement and minimize stress on wire bonds, allowing the gel to cut through with little resistance during stress testing or in the operating environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a low modulus gel is used for encapsulation, then thermomechanical stress on the sensor is minimized, but the gel moves or flows under centrifugal stress reducing reliability
Solution Approach 1:
A fabric layer is introduced as an intermediary between the low modulus gel and the sensor components. The fabric has higher mechanical strength and lower gel movement characteristics, acting as a mediator that prevents gel flow under centrifugal stress while allowing the gel to maintain its low modulus properties for minimizing thermomechanical stress on the sensor.
Solution Approach 2:
The encapsulation system becomes a composite structure combining the low modulus gel with a fabric layer. The gel provides stress minimization properties while the fabric provides structural stability and prevents gel movement. This composite approach allows both materials to contribute their advantageous properties without compromising the other.
2Stability of the object's composition
If a higher modulus gel is used to resist movement, then gel stability is improved, but wire bond stress increases causing wire breaks
Solution Approach 1:
The fabric layer serves as a mediator that bears the mechanical load and prevents gel movement, thereby protecting the wire bonds from stress. The wire bonds no longer need to support the gel's structural requirements, as the fabric assumes this role, allowing the gel to focus on its primary function of stress minimization.
Solution Approach 2:
The encapsulation system is segmented into distinct functional layers: the gel layer for stress minimization and the fabric layer for structural support. This segmentation allows each layer to be optimized for its specific function without compromising the other, with the fabric handling mechanical stability requirements.
3Force
If a higher modulus gel is used to prevent movement, then gel flow resistance is improved, but sensor performance is impacted
Solution Approach 1:
The fabric layer acts as an intermediary that provides the necessary mechanical resistance to gel flow and centrifugal forces. This allows the gel to maintain its low modulus properties for optimal sensor performance while the fabric provides the structural rigidity needed to prevent gel movement and maintain system stability.
Data Source
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AI summary
A pressure sensor (100) includes a first housing (102) having a cavity (200). The pressure sensor further includes a pressure sensing device (106) attached to a bottom of the cavity. The pressure sensor further includes a layer of gel (208) over the pressure sensing device. The pressure sensor further includes a baffle (110, 302, 502, 702, 1002) in contact with the gel to reduce movement of the gel.