Interposer Depression for Thermal Stress Relief in Semiconductor Packages
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Solution Overview
Problem
Temperature cycling causes different materials in a package with varying coefficients of thermal expansion to experience static force stress, leading to delamination and potential damage such as broken wire bonds due to thermal-induced stress.
Innovation Solution
Incorporating at least one depression in the surface of the interposer, which allows the encapsulant material to adhere mechanically in addition to a chemical bond, thereby resisting movement and minimizing thermal-induced stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different materials with varying coefficients of thermal expansion are used in the package, then functional requirements are met, but thermal-induced stress increases during temperature cycling
Solution Approach 1:
The patent introduces a depression with specific geometric characteristics (depth, diameter, location) in the interposer substrate at specific locations where thermal stress concentrates. This local structural modification creates a stress-relief zone that absorbs thermal expansion differences between materials, allowing the package to accommodate multiple materials with varying coefficients of thermal expansion without excessive stress.
2Reliability
If the encapsulant material is applied over the interposer surface, then protection and encapsulation are achieved, but delamination occurs under thermal stress
Solution Approach 1:
The depression is formed in the interposer substrate before the encapsulant material is applied. This pre-formed structural feature acts as a cushioning element that absorbs and distributes thermal stress before it can propagate to the encapsulant interface, preventing delamination by reducing the stress concentration at the bonding interface.
3Ease of manufacture
If the interposer surface is flat, then manufacturing is simplified, but stress concentration occurs during thermal cycling
Solution Approach 1:
Rather than making the entire interposer surface complex, the patent applies a local modification approach by forming a depression with specific geometric parameters (depth, diameter, location) only at the stress concentration zone. This maintains the simplicity of flat surface manufacturing while introducing localized stress-relief geometry where needed.
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 solution effectively reduces static mechanical stress and minimizes the impact of thermal stresses on the package, preventing delamination and potential damage like broken wire bonds.
Implementation Method 1
allows the encapsulant material to adhere mechanically in addition to a chemical bond
Implementation Method 2
disposed in the at least one depression to resist movement of the encapsulant material relative to the interposer
Implementation Method 3
different coefficients of thermal expansion, which may result in static force stress during temperature cycling
Implementation Method 4
resist movement of the encapsulant material relative to the interposer, minimizing thermal-induced stress
Data Source
AI summary
Embodiments include but are not limited to apparatuses and systems including semiconductor packages, e.g. memory packages, having an interposer including at least one topological feature, such as a depression in a surface of the interposer, a die coupled to the surface of the interposer, and an encapsulant material formed over the die and the interposer, and disposed in the at least one depression to resist movement of the encapsulant material relative to the interposer. Other embodiments may be described and claimed.