Chip Scale Package Multi-Composite Cavity Wall Design
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Solution Overview
Problem
Chip scale packages with high modulus materials for cavity walls face delamination issues during reflow due to popcorn cracking, and low modulus materials struggle to maintain bond integrity during singulation, leading to stress-induced breakdown and moisture contamination risks.
Innovation Solution
Implementing a multi-composite wall design with a low modulus material for the inner cavity wall and a high modulus material for the outer cavity wall, where the inner wall is made of a dry film and the outer wall is made of a solder mask, reducing stress and enhancing bonding integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high modulus material is used for cavity wall, then bond integrity is improved, but stress-induced delamination occurs during reflow
Solution Approach 1:
The cavity wall is segmented into inner and outer walls with different material properties. The inner wall uses low modulus material to reduce stress during reflow, while the outer wall uses high modulus material to maintain bond integrity, thus resolving the contradiction between bond strength and delamination resistance.
Solution Approach 2:
Different regions of the cavity wall are assigned different material qualities. The inner wall region near the die uses low modulus material for stress reduction, while the outer wall region uses high modulus material for structural strength, allowing each region to optimize its local function.
2Reliability
If low modulus material is used for cavity wall, then stress during reflow is reduced, but bond integrity deteriorates during singulation
Solution Approach 1:
The cavity wall is divided into functional segments: inner wall with low modulus material for stress reduction during reflow, and outer wall with high modulus material for maintaining bond integrity during singulation and handling.
Solution Approach 2:
The cavity wall structure uses composite material configuration with two distinct materials: low modulus material for the inner wall and high modulus material for the outer wall, combining the advantages of both material types to resolve the contradiction.
3Ease of manufacture
If single material is used for cavity wall, then manufacturing is simplified, but cannot simultaneously satisfy reflow stress reduction and bond integrity requirements
Solution Approach 1:
The cavity wall employs a composite structure with inner and outer walls made of different materials optimized for their specific functions. This composite approach maintains manufacturing feasibility while achieving superior performance in both stress reduction and bond integrity.
Solution Approach 2:
Different material qualities are applied to different parts of the cavity wall structure. The inner wall uses low modulus material for thermal stress management, while the outer wall uses high modulus material for mechanical strength, allowing each region to be optimized for its specific operational requirements.
Data Source
AI summary
Implementations of semiconductor packages may include: a die coupled to a glass lid; one or more inner walls having a first material coupled to the die; an outer wall having a second material coupled to the die; and a glass lid coupled to the die at the one or more inner walls and at the outer wall; wherein the outer wall may be located at the edge of the die and the glass lid and the one or more inner walls may be located within the perimeter of the outer wall at a predetermined distance from the perimeter of the outer wall; and wherein a modulus of the first material may be lower than a modulus of the second material.