Al Connection Material Composition for Crack-Free Thermal Cycling
Solution Overview
Problem
Next-generation power semiconductor devices require Al connection materials that can withstand repeated thermal stress without developing cracks, as existing Al alloys with added elements like Si suffer from internal cracks and poor temperature cycle reliability.
Innovation Solution
An Al connection material containing 3.0% to 12.0% Si, 5 to 800 ppm of Sr, Na, and Eu or Ca, with controlled Si phase orientations and diameters, and optionally Ti, B, Zr, Ni, Y, Yb, and Sc, to enhance adhesion and reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al connection material is made of high-purity Al to maintain good electrical conductivity and bonding properties, then bonding strength is maintained, but the material breaks due to thermal stress after repeated temperature cycling
Solution Approach 1:
The invention changes the compositional parameters of Al connection material by adding specific alloying elements (Ti: 0.01-0.1 mass%, B: 0.01-0.1 mass%, Zr: 0.01-0.1 mass%) to high-purity Al (99.99% or more). These parameter changes enable the material to withstand thermal stress while maintaining good bonding properties, resolving the contradiction between reliability under thermal cycling and resistance to thermal stress.
Solution Approach 2:
The invention creates a composite Al alloy material combining high-purity Al base metal with trace amounts of strengthening elements (Ti, B, Zr). This composite structure provides both the electrical conductivity and bonding characteristics of pure Al and the thermal stress resistance of alloyed material, achieving temperature cycle reliability without sacrificing strength.
2Strength
If alloying elements are added to Al to improve mechanical strength and thermal stress resistance, then temperature cycle reliability improves, but internal cracks develop during manufacturing
Solution Approach 1:
The invention precisely controls the concentration parameters of alloying elements to very low levels (0.01-0.1 mass% each for Ti, B, Zr). This precise parameter control provides sufficient thermal stress resistance while avoiding excessive alloying that would cause internal cracks during wire drawing and manufacturing processes.
Solution Approach 2:
The invention introduces trace amounts of specific elements (Ti, B, Zr) that locally strengthen the Al matrix without creating widespread structural defects. These localized strengthening elements improve thermal stress resistance while maintaining manufacturing quality and preventing internal crack formation.
3Strength
If Si is added to Al to improve mechanical strength through solid-solution strengthening, then bonding strength is improved, but crack development is suppressed only in limited temperature ranges
Solution Approach 1:
The invention uses a composite approach combining high-purity Al with multiple trace alloying elements (Ti, B, Zr) instead of relying on Si alone. This multi-element composite provides broader temperature range applicability and more consistent performance across different operating conditions compared to Si-based solutions.
Solution Approach 2:
The invention changes from Si-based strengthening (with limited temperature range effectiveness) to a new parameter regime using Ti, B, and Zr alloying at 0.01-0.1 mass% levels. This parameter change extends the effective temperature range for crack suppression while maintaining bonding strength.
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 effectively suppresses internal cracks during manufacturing and improves temperature cycle reliability, ensuring stable operation of next-generation power semiconductor devices.
Implementation Method 1
the Al connection material contains 0.01% by mass or more and 0.1% by mass or less of Ti, B, and Zr in total, thereby making it possible to suppress generation of an internal crack at the time of manufacture and to exhibit excellent temperature cycle reliability
Implementation Method 2
wedge bonding is a method for applying ultrasonic vibrations and loads to the Al connection material via a jig (tool) made of metal, breaking surface oxide films of the Al connection material and an electrode material to expose new surfaces
Implementation Method 3
thermal stress, which is caused by a thermal expansion difference between the Al connection material and the semiconductor chip, is repeatedly applied to the 1st bonding part
Data Source
Figure 1~2
Figure 3
AI summary
To provide an Al connection material that may suppress generation of internal cracks at the time of manufacture and exhibits excellent temperature cycle reliability. The Al connection material containing 3.0% by mass or more and 12.0% by mass or less of Si, and containing 5 mass ppm or more and 800 mass ppm or less of one or more of Sr, Na, Eu, and Ca in total.