Composite Adhesion via Thermal Expansion Inversion
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Solution Overview
Problem
Current composites in the electronics industry face issues such as residual stresses, micro-cracks, and stress crack corrosion due to mismatched coefficients of expansion and surface unevenness between glass or glass ceramic materials and components, leading to instability and failure during the dicing process.
Innovation Solution
A composite is developed with a specific geometric and material-physical compatibility index (KG) that balances the coefficients of expansion, thickness variations, and residual stresses, ensuring a uniform adhesive layer and optimized adhesion, where the coefficient of expansion of the component is greater than the glass or glass ceramic material to reduce tensile stresses and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the coefficient of expansion of the component is made lower than the coefficient of expansion of the glass material, then the adhesion between component and glass is improved, but tensile stress occurs on the underside of the glass leading to composite failure
Solution Approach 1:
The invention changes the parameter relationship by making the component's coefficient of expansion greater than the glass material's coefficient of expansion, reversing the conventional approach. This parameter inversion transforms the stress distribution, converting tensile stress on the glass underside into compressive stress, thereby preventing glass failure while maintaining adhesion strength
Solution Approach 2:
The invention utilizes thermal expansion differences between materials but inverts the conventional parameter selection. By selecting a component material with higher thermal expansion coefficient than the glass, the system exploits thermal expansion to generate beneficial compressive stresses in the glass during temperature variations, preventing tensile stress-induced failures
2Reliability
If a relatively thin adhesive layer is applied to cover surface unevenness on the glass surface, then the adhesion coverage is improved, but the adhesive layer becomes too thick leading to stress concentration and failure
Solution Approach 1:
The invention performs preliminary action by pre-smoothing the glass surface through mechanical polishing or chemical etching before adhesive application. This preliminary surface preparation creates a sufficiently flat substrate that allows thin adhesive layers to achieve complete surface coverage without requiring excessive thickness, thereby avoiding stress concentration
3Manufacturing precision
If the glass material is stretched to smooth the surface, then the surface evenness is improved, but residual stresses remain in the glass leading to potential failure
Solution Approach 1:
The invention applies preliminary anti-action by implementing a controlled thermal annealing process after mechanical stretching. This annealing treatment counteracts the residual stresses introduced during stretching by allowing stress relaxation through controlled heating and cooling, thereby eliminating the harmful effects of residual stress while preserving the surface evenness achieved through stretching
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 composite achieves a higher degree of compatibility, resulting in longer lifespan, low residual stresses, and high surface quality, with reliable adhesion and reduced risk of stress crack corrosion, enabling stable bonding and separation into individual components.
Implementation Method 1
The glass or respectively the glass ceramic material is stretched smooth
Implementation Method 2
The composite consisting of the wafer material and a glass or glass ceramic material which can also be used as a capping wafer, is produced by means of an adhesive
Implementation Method 3
the coefficient of expansion α1 of the material for the component is selected to be lower than the coefficient of expansion α2 for the glass or respectively the glass ceramic material
Data Source
AI summary
A composite includes a component and a glass or glass ceramic material. The component has a first coefficient of expansion α1 and the glass or the glass ceramic material has a second coefficient of expansion α2. The glass or the glass ceramic material has a surface with a thickness and thickness differences (TTV) within the surface, and thickness fluctuations (LTV). The composite has a residual stress in the glass or the glass ceramic material (WARP), and a geometric and material-physical degree of compatibility KG≥4.