ZnAl Solder Phase Transition for Semiconductor Bonding
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Solution Overview
Problem
The bonding strength between semiconductor elements and substrates using zinc-aluminum based eutectic solder varies significantly, affecting the yield of semiconductor devices.
Innovation Solution
Increasing the temperature of ZnAl eutectic solder sandwiched between a semiconductor element and a substrate under load, causing it to melt and then reducing the temperature while applying a static load, which converts ZnAl eutectic phase structures to ZnAl eutectoid phase structures, minimizing stress differences and bonding strength variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ZnAl eutectic solder is used for bonding semiconductor elements and substrates, then bonding is achieved at relatively low temperature, but bonding strength varies significantly
Solution Approach 1:
The patent applies parameter changes by controlling the cooling rate after melting the ZnAl eutectic solder. By reducing the temperature at a controlled rate (0.1-10°C/min) while maintaining a load, the phase structure transforms from eutectic to eutectoid, which minimizes stress differences and reduces bonding strength variation while maintaining low bonding temperature
Solution Approach 2:
The patent utilizes phase transitions by transforming the ZnAl solder from eutectic phase structure to eutectoid phase structure through controlled cooling. This phase transition occurs during the cooling process after melting, where the specific cooling rate controls the transformation to minimize stress differences at phase interfaces, thereby improving bonding strength consistency
2Productivity
If ZnAl eutectic solder is heated and cooled rapidly, then bonding process is fast, but stress differences at phase interfaces increase causing bonding strength variation
Solution Approach 1:
The patent optimizes the cooling rate parameter to a specific range (0.1-10°C/min) that balances bonding speed and bonding strength consistency. This controlled cooling rate allows sufficient time for uniform phase transformation to eutectoid structure, minimizing stress differences while maintaining reasonable productivity
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 method results in a semiconductor device with consistent bonding strength, improved yield, and reduced thermal resistance, meeting international standards and maintaining strength up to high temperatures.
Implementation Method 1
ZnAl eutectic phase structures change to ZnAl eutectoid phase structures
Implementation Method 2
ZnAl eutectic solder sandwiched between a semiconductor element and a substrate having Cu as a principal element on the surface is increased in temperature while being subjected to a load, caused to melt
Data Source
AI summary
A method for manufacturing a semiconductor device is carried out by readying each of a semiconductor element, a substrate having Cu as a principal element at least on a surface, and a ZnAl solder chip having a smaller shape than that of the semiconductor element; disposing the semiconductor element and the substrate so that respective bonding surfaces face each other, and sandwiching the ZnAl eutectic solder chip between the substrate and the semiconductor element; increasing the temperature of the ZnAl solder chip sandwiched between the substrate and the semiconductor element while applying a load to the ZnAl solder chip such that the ZnAl solder chip melts to form a ZnAl solder layer; and reducing the temperature of the ZnAl solder layer while applying a load to the ZnAl solder layer.