Solder Joint Crack Arrestor for Thermal Stress
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Solution Overview
Problem
The mismatch in thermal expansion coefficients between semiconductor dies and substrates leads to stress-induced cracks in solder joints, which can propagate and degrade or destroy the electrical and physical connections, rendering the components useless and requiring complete refabrication.
Innovation Solution
A crack stopper structure, such as a hollow cylinder or ring-shaped feature, is integrated into the solder joints to intercept and prevent the propagation of cracks, using conductive materials like copper or nickel, and optionally backed up by additional cylindrical structures for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder joints are used to connect semiconductor die to substrate, then electrical and physical connections are established, but thermal expansion mismatch causes stress-induced cracks that propagate and destroy the connections
Solution Approach 1:
The patent divides the solder joint into multiple segments by introducing a crack stopper structure that creates discrete zones. The crack stopper is formed with multiple openings that segment the continuous solder material, creating isolated regions that prevent crack propagation across the entire joint while maintaining electrical connectivity through the remaining conductive paths.
Solution Approach 2:
The patent applies local quality by creating a crack stopper structure with specific geometric features (openings or cavities) at strategic locations within the solder joint. This localized structural modification changes the mechanical properties only where needed to arrest cracks, while the rest of the solder joint maintains its original connectivity and electrical properties.
2Reliability
If crack stopper structure is added to prevent crack propagation, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges the crack stopper structure with the existing solder joint formation process. The crack stopper is created as an integral part of the solder joint during the same manufacturing steps (e.g., using the same plating, paste screening, or ball mount processes), combining two functions (connection and crack protection) into a single integrated structure rather than adding separate components.
Solution Approach 2:
The crack stopper structure serves multiple functions simultaneously: it acts as both a mechanical barrier to crack propagation and maintains electrical conductivity through its conductive material composition. The same structural feature provides both protective and functional roles, reducing the need for additional separate components.
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 crack stopper effectively prevents crack propagation, reducing defects and maintaining electrical continuity, even if the conductive material cracks, thereby enhancing the reliability and resilience of the interconnects.
Implementation Method 1
the semiconductor die and the substrate will expand during heating up cycles and contract during cooling down cycles to different lengths
Data Source
AI summary
A system and method for preventing cracks is provided. An embodiment comprises placing crack stoppers into a connection between a semiconductor die and a substrate. The crack stoppers may be in the shape of hollow or solid cylinders and may be placed so as to prevent any cracks from propagating through the crack stoppers.