Sensor Recess Design for Thermal Expansion Mitigation
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Solution Overview
Problem
Semiconductor packages face reliability issues due to thermal expansion caused by differing coefficients of thermal expansion (CTE) among materials, leading to distortions and measurement errors in sensors.
Innovation Solution
A recess is created on the back surface of the electric device within the package, which is filled with adhesive material to improve adhesion and reduce signal drift by allowing for lower adhesive fillets, thereby mitigating the effects of thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive material is used to bond the electric device to the substrate, then adhesion is improved, but thermal expansion distortions are exacerbated due to adhesive fillets
Solution Approach 1:
The back surface of the electric device is segmented into an active area and a peripheral area. The recess is formed specifically in the peripheral area, separating the bonding function (adhesive fillet) from the active sensing area, allowing the adhesive to be confined to non-critical regions while preserving sensor performance
Solution Approach 2:
The recess creates a localized structural modification in the peripheral area of the electric device. This local change allows the adhesive material to be positioned precisely where it provides bonding strength without interfering with the active sensing elements, achieving different quality requirements in different zones
2Strength
If adhesive fillets are increased to improve adhesion, then bonding strength is improved, but signal drift caused by thermal expansion increases
Solution Approach 1:
The recess confines the adhesive fillet to the peripheral region, segmenting it away from the active sensing area. This allows adequate adhesive volume for bonding strength while preventing the adhesive from causing thermal expansion-induced signal drift in the sensor elements
Solution Approach 2:
The recess acts as an intermediary structure that mediates between the adhesive material and the active sensing area. It provides a dedicated space for the adhesive while creating a physical and functional barrier that prevents the adhesive from directly affecting the sensor measurements
3Ease of manufacture
If the electric device is bonded directly to the substrate, then manufacturing is simplified, but thermal expansion mismatches cause delamination
Solution Approach 1:
The recess is pre-formed on the back surface of the electric device before bonding to the substrate. This preliminary structural preparation ensures that when adhesive is applied, it automatically fills the recess and creates optimal bonding geometry, improving both reliability and manufacturing consistency
Solution Approach 2:
The recess structure enables the adhesive material to self-align and self-constrain within the peripheral region during bonding. The geometry of the recess automatically guides the adhesive placement and prevents excessive adhesive from reaching the active area, reducing the need for complex adhesive application controls
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 recessed design enhances adhesion between the electric device and the substrate, reduces measurement errors, and minimizes distortions caused by thermal expansion, improving the overall reliability of semiconductor packages.
Implementation Method 1
the recess is substantially filled with adhesive material improving adhesion between the electric device and a substrate of the package
Implementation Method 2
heat that remains in the package can result in varying thermal expansion rates thereby causing distortions or delamination within the package
Data Source
AI summary
Embodiments are directed to a package that includes an electric device having a recess. In one embodiment, the electric device is a sensor and the recess reduces signal drift of the sensor caused by thermal expansion of the package. In another embodiment, the recess is substantially filled with adhesive material, thus increasing adhesion between the electric device and a substrate of the package while at the same time allowing for lower adhesive fillets.