Semiconductor Device Bonding Wire Material Distribution
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Solution Overview
Problem
Semiconductor devices using copper bonding wires face reduced temperature cycle resistance due to increased stress on electrode pads and thinner intermetallic compound layers, leading to cracking and increased material costs when all wires are made of the same expensive metal like gold.
Innovation Solution
Employing bonding wires of different metals with varying Young's moduli for electrode pads located near and away from corners, with a thicker intermetallic compound layer for pads near corners to enhance mechanical strength and using a softer metal bump for stress relief, allowing for reduced material costs by eliminating the need for expensive gold wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If bonding wires made of Cu are used instead of Au, then material cost is reduced, but temperature cycle resistance deteriorates due to increased stress and thinner intermetallic compound layers
Solution Approach 1:
The patent applies different wire materials to different regions: Cu wires for corner pads (high stress areas) and Au wires for non-corner pads. This local differentiation allows cost reduction in critical areas while maintaining reliability in less critical areas, resolving the contradiction between material cost and temperature cycle resistance.
Solution Approach 2:
The patent changes the material parameter (Young's modulus) of bonding wires based on location. Cu has higher Young's modulus than Au, making it stiffer and more cost-effective for corner pads where stress management is critical, while Au provides better flexibility for other positions, optimizing both cost and reliability.
2Reliability
If all bonding wires are made of expensive Au, then temperature cycle resistance is improved, but material cost increases
Solution Approach 1:
The patent differentiates wire material selection by pad location: corner pads receive Cu wires optimized for stress management, while non-corner pads receive Au wires. This selective approach maintains overall reliability while significantly reducing material cost compared to using Au for all wires.
Solution Approach 2:
The patent uses cheaper Cu wires for corner pads where the intermetallic compound layer provides sufficient mechanical strength, accepting that these wires may have different durability characteristics than Au wires, thereby reducing overall material cost while maintaining acceptable reliability.
3Quantity of substance
If Cu bonding wires are used, then material cost is reduced, but intermetallic compound layer becomes thinner leading to reduced mechanical strength
Solution Approach 1:
The patent places Cu wires specifically at corner pads where structural design and thicker intermetallic compound layers compensate for the thinner IMC formed by Cu bonding. Non-corner pads use Au wires that form thicker IMC layers, maintaining mechanical strength where needed while reducing cost at critical positions.
Solution Approach 2:
The patent creates a composite bonding wire system using both Cu and Au materials with different properties. Cu provides cost effectiveness and adequate performance at corner positions, while Au provides superior mechanical strength at other positions, creating an optimized hybrid system.
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 configuration improves temperature cycle resistance of electrode pads while reducing material costs by distributing stress effectively and increasing mechanical strength at critical corner areas, preventing cracking and optimizing wire bonding materials.
Implementation Method 1
an intermetallic compound layer is disposed between each of the plurality of electrode pads and the corresponding bonding wire, and the intermetallic compound layer is made of an intermetallic compound including both of the metal configuring the plurality of electrode pads and the metal configuring the bonding wires
Data Source
AI summary
Electrode pads disposed on a first surface of a semiconductor element include a first pad located close to a corner and a second pad located apart from the corner compared with the first pad. A first wire connected to the first pad has a smaller Young's modulus than a second wire connected to the second pad. A thickness of an intermetallic compound layer formed by the first wire and the first pad is larger than a thickness of an intermetallic compound layer formed by the second wire and the second pad.