Semiconductor Chip Rounded Corners Mitigate Thermal Stress
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Solution Overview
Problem
Solder joint fatigue and delamination issues in flip-chip assemblies due to thermal expansion mismatch between semiconductor chips and substrates, particularly at the orthogonal corners, lead to mechanical defects like chip cracking and solder joint failure.
Innovation Solution
Forming semiconductor chips with rounded corners instead of orthogonal ones to reduce stress concentration and prevent underfill delamination, using techniques like laser cutting to create rounded corner geometries that blend into the edges, thereby minimizing the ledge and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal corners are used in semiconductor chips, then manufacturing is simpler, but stress concentration occurs at corners leading to delamination and solder joint failure
Solution Approach 1:
The patent applies curvature by rounding the corners of the semiconductor chip instead of using sharp orthogonal corners. This curvature eliminates stress concentration points at the corners, preventing delamination and solder joint failure while maintaining manufacturing feasibility through standard rounding processes.
2Reliability
If dummy bumps are added to reinforce edge areas, then solder joint reliability improves, but die size increases and routing is constrained
Solution Approach 1:
The patent uses corner rounding to eliminate stress concentration without adding any physical structures. This approach improves reliability by preventing delamination while maintaining the original die area and routing flexibility, unlike dummy bumps which occupy valuable space and constrain routing.
3Reliability
If underfill chemical compositions are modified to prevent delamination, then reliability may improve, but chemical solutions are not readily available and add complexity
Solution Approach 1:
The patent addresses delamination by modifying the physical geometry of the chip corners rather than changing material chemistry. This geometric solution is readily implementable and avoids the complexity of developing and characterizing new underfill chemical compositions.
4Adaptability or versatility
If chip size is increased to accommodate routing around edge effects, then routing flexibility improves, but material cost and processing cost increase
Solution Approach 1:
The patent eliminates the need for increased die size by removing the root cause of edge effects through corner rounding. This maintains full routing flexibility within the original die area, avoiding additional material costs and processing expenses associated with larger chips.
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 rounded corners effectively mitigate stress concentrations, reducing the likelihood of underfill delamination and associated mechanical defects, thereby enhancing the reliability and durability of solder joints.
Implementation Method 1
The rounded corners effectively mitigate stress concentrations, reducing the likelihood of underfill delamination and associated mechanical defects
Implementation Method 2
using techniques like laser cutting to create rounded corner geometries
Data Source
AI summary
Various semiconductor chips and methods of making the same are disclosed. In one aspect, a method of manufacturing is provided that includes providing a semiconductor wafer that has plural semiconductor chips. Each of the plural semiconductor chips includes a first principal side and a second and opposite principal side. Material is removed from the semiconductor wafer to define at least one rounded corner of the first principal side of at least one of the plural semiconductor chips.