Image Sensor Cap with Air Vent for CTE Mismatch Stress Relief
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Solution Overview
Problem
Prior art image sensing devices face reliability issues due to warping caused by coefficient of thermal expansion (CTE) mismatch in high-stress applications like automobiles, leading to potential failures from temperature and humidity variations.
Innovation Solution
The image sensing device incorporates an open cavity design with an air vent coupled to an internal cavity, reducing stress factors by allowing CTE mismatch reduction and using a cap with a multi-step shoulder to prevent flexing, along with adhesive layers and encapsulation material to secure components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the image sensing device uses a fully enclosed encapsulation structure, then protection against environmental factors is improved, but thermal expansion stress accumulates causing warping
Solution Approach 1:
The encapsulation structure incorporates a porous cap with controlled porosity (e.g., 10-50% void volume) that allows thermal expansion accommodation while maintaining environmental protection. The porous structure acts as a stress-absorbing medium that expands and contracts with temperature changes, preventing warping of the underlying image sensor components.
Solution Approach 2:
The cap structure transitions from a fully solid design to a locally modified porous design, where specific regions contain voids or pores while other regions maintain solid structural integrity. This localized quality change allows differential expansion in different areas, accommodating CTE mismatch between components while preserving overall structural strength and environmental sealing.
2Strength
If the cap structure is made rigid to prevent flexing, then structural stability is improved, but stress from thermal expansion cannot be relieved
Solution Approach 1:
The cap is constructed as a composite structure combining rigid material phases with void or porous phases. The rigid portions provide structural stability and strength, while the void/porous portions serve as stress-relief zones that expand and contract with thermal cycles. This composite architecture simultaneously achieves both structural integrity and stress accommodation.
Solution Approach 2:
The porous or void-containing cap structure预先 (in advance) provides cushioning space for thermal expansion before stress can build up to damaging levels. The voids act as pre-configured stress-absorbing zones that accommodate expansion movements, preventing stress transmission to the image sensor and interconnect layers.
3Stability of the object's composition
If adhesive layers are used to secure components, then assembly stability is improved, but thermal stress concentrates at adhesive interfaces
Solution Approach 1:
The porous cap acts as an intermediary element between the rigid封装 structure and the image sensor components. It mediates thermal expansion forces, distributing stresses uniformly across its structure rather than concentrating them at adhesive interfaces. This intermediary function protects the adhesive bonds from thermal cycling damage.
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 open cavity design enhances reliability by mitigating CTE mismatch stress, effectively addressing warping and failure issues in high-stress environments, particularly in automotive applications.
Implementation Method 1
reliability issues due to warping caused by coefficient of thermal expansion (CTE) mismatch
Data Source
AI summary
An image sensing device includes an interconnect layer and a number of grid array contacts arranged on a bottom side of the interconnect layer. An image sensor integrated circuit (IC) is carried by the interconnect layer and has an image sensing surface. A number of electrical connections are coupled between the image sensor IC and an upper side of the interconnect layer. A transparent plate overlies the image sensing surface of the image sensor IC. A cap is carried by the interconnect layer and has an opening overlying transparent plate and the image sensing surface. The cap has an upper wall spaced above the interconnect layer and the image sensor IC to define an internal cavity and the cap defines an air vent coupled to the internal cavity.