Lead-Free Column Interconnect With Short Moment Arm
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Solution Overview
Problem
Semiconductor chip packages face sensitivity to thermal and mechanical stresses, which existing technologies have not adequately addressed in terms of performance improvements.
Innovation Solution
A method involving the use of a lead-free column interconnect, where a high melting temperature, lead-free solder is plated on a copper pillar and contacted with low melting temperature, lead-free solder on a laminate substrate, allowing the copper pillar to penetrate into the solder a predetermined distance, thereby joining the semiconductor device to the substrate while minimizing stress through a short moment arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-free solder columns are used to interconnect semiconductor devices to substrates, then reliability under thermal and mechanical stresses is improved, but stress resistance and joint strength are worsened due to long moment arms
Solution Approach 1:
The interconnect structure is segmented into three distinct components: a copper pillar, a high melting temperature lead-free solder layer, and a low melting temperature lead-free solder layer. This segmentation allows each component to perform its specific function - the copper pillar provides structural support with short moment arm, the high melting solder provides thermal stability, and the low melting solder provides stress-resistant joining
Solution Approach 2:
The invention uses a composite interconnect structure combining copper pillar with two different lead-free solder materials having different melting temperatures. This composite approach leverages the advantages of each material - copper's mechanical strength, high melting solder's thermal stability, and low melting solder's stress resistance - to achieve both reliability and stress resistance simultaneously
2Temperature
If high melting temperature lead-free solder is plated on the entire copper pillar surface, then thermal stability is improved, but manufacturing precision is worsened due to difficulty in controlling solder distribution
Solution Approach 1:
The high melting temperature lead-free solder is applied selectively only to the end surface of the copper pillar rather than the entire surface. This local quality approach ensures proper solder distribution and area control while still providing the necessary thermal stability for the interconnect structure
Solution Approach 2:
The high melting temperature lead-free solder is plated on the copper pillar end surface before the actual interconnection process. This preliminary action prepares the copper pillar with controlled solder distribution, making subsequent assembly easier and more precise
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
This approach enhances the reliability of the interconnect by reducing stress on the lead-free column and achieving strong, stress-resistant joints between semiconductor devices and substrates, improving thermal and mechanical performance.
Implementation Method 1
plating a high melting temperature, lead-free solder on a portion of the end
Implementation Method 2
reflowing the low melting temperature, lead-free solder so that the high melting, lead-free solder and copper pillar penetrate into the reflowed low melting, lead-free solder
Data Source
AI summary
Disclosed are interconnects in which one substrate having a high melting temperature, lead-free solder column is joined to a second substrate having openings filled with a low melting temperature, lead-free solder such that the high melting temperature, lead-free solder column penetrates into the low melting temperature, lead-free solder so as to obtain a short moment arm of solder.