Semiconductor Solder Joint with Barrier Layer for Crack Prevention
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Solution Overview
Problem
Existing semiconductor devices face reliability issues due to defects such as cracks in solder joints, leading to characteristic degradation and reduced lifetime of electronic systems.
Innovation Solution
A semiconductor device design featuring a high-temperature solder with a higher tin content, a barrier layer, and a low-temperature solder with a lower melting point, where the high-temperature solder is formed on a conductive pad, and the low-temperature solder is formed on the high-temperature solder with a barrier layer in between, preventing mixing and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer solder joint is used, then the manufacturing process is simple, but the reliability is low due to cracks and defects
Solution Approach 1:
The solder joint is divided into multiple layers with different functions: a first solder layer (high melting point, high Sn content) provides mechanical strength and stress relief, while a second solder layer (low melting point, lower Sn content) ensures good electrical connection and wettability. This segmentation allows each layer to optimize for its specific function, improving overall reliability without excessive complexity.
Solution Approach 2:
The invention uses composite solder structure combining different solder materials with distinct properties. The first solder layer uses high-Sn alloy for strength, while the second solder layer uses low-melting-point alloy for connection quality. This composite approach leverages the advantages of each material to achieve both mechanical integrity and electrical performance.
2Strength
If high-tin content solder is used, then the strength is improved, but the melting point increases making assembly difficult
Solution Approach 1:
The solder system is segmented into two layers with different compositions. The first layer contains high Sn content (≥90 wt%) for strength, while the second layer has lower Sn content and lower melting point for easy assembly. This segmentation allows the high-strength material to be used only where mechanical support is needed, while the lower-melting-point material handles the bonding process.
Solution Approach 2:
Different regions of the solder joint have different material compositions tailored to local requirements. The bottom layer (first solder layer) has high Sn content for strength where mechanical load is highest, while the top layer (second solder layer) has lower melting point for better wettability and easier assembly operations.
3Reliability
If multiple solder layers with different temperatures are used, then the reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The first solder layer is formed and partially reflowed before the second solder layer is applied. This preliminary action creates a stable base with good mechanical properties, allowing the second layer to be added subsequently for final connection. This sequential approach simplifies manufacturing compared to attempting to apply both layers simultaneously.
Solution Approach 2:
The manufacturing process utilizes parameter changes in temperature to control the state of each solder layer. The first solder layer is reflowed at a higher temperature to ensure strength, then the second solder layer is applied and reflowed at a lower temperature. This parameter control enables multi-layer construction without requiring completely separate manufacturing processes.
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 provides a high-reliability solder joint by relieving stress and preventing mixing between the high-temperature and low-temperature solders, thereby improving the durability and performance of semiconductor devices.
Implementation Method 1
A barrier layer is formed between the high-temperature solder and the low-temperature solder
Implementation Method 2
A first inter-metallic compound (IMC) may be formed between the barrier layer and the high-temperature solder. A second IMC may be formed between the barrier layer and the low-temperature solder
Implementation Method 3
A first diffusion region may be formed between the second IMC and the low-temperature solder. The first diffusion region may include materials of the second barrier layer and the low-temperature solder
Data Source
AI summary
Provided is a semiconductor device having a high-reliability solder joint. The semiconductor device includes a high-temperature solder formed on a conductive pad. A low-temperature solder having a lower melting point than the high-temperature solder is formed on the high-temperature solder. A barrier layer is formed between the high-temperature solder and the low-temperature solder. An Sn content of the high-temperature solder is higher than that of the low-temperature solder.