Au-Pd Skin Layered Cu Bonding Wire for Humidity-Stable 2nd Bonds
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cu bonding wires with Pd coating face issues with 2nd bondability to Pd-plated lead frames and Au-plated lead frames, and high failure rates in high-humidity heating evaluations due to oxidation and corrosion reactions, especially during HAST tests.
Innovation Solution
A Cu alloy core material with a Pd coating layer and a skin alloy layer containing Au and Pd, where Ni, Pd, and Pt are added to the core material, and the concentration of Cu is adjusted at the outermost surface to 1-10 at%, enhancing 2nd bondability and reducing corrosion by controlling mutual diffusion at the bonding interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Cu bonding wire with Pd coating is used, then oxidation resistance and long-term storage characteristics are improved, but 2nd bondability to Pd-plated lead frames deteriorates
Solution Approach 1:
The patent applies local quality by creating a multi-layer coating structure where each layer serves a specific function: the Pd layer provides oxidation resistance, while the Au layer (5-20 nm thick) on top of the Pd layer provides excellent 2nd bondability to Pd-plated lead frames. This localized functional differentiation resolves the contradiction between oxidation resistance and bondability.
Solution Approach 2:
The patent uses composite materials by combining Pd and Au in a multi-layer coating structure on the Cu core. The composite structure leverages the oxidation resistance of Pd and the superior bondability of Au, achieving both properties simultaneously and resolving the technical contradiction.
2Duration of action of stationary object
If a Cu bonding wire with Pd coating is used, then long-term storage characteristics are improved, but failure rate in high-humidity heating evaluation increases
Solution Approach 1:
The patent applies local quality by creating a multi-layer coating structure where each layer serves a specific function: the Pd layer provides oxidation resistance and long-term storage characteristics, while the Au layer on top (5-20 nm thick) provides excellent resistance to corrosion in high-humidity environments, thereby reducing failure rates in HAST tests.
Solution Approach 2:
The patent uses composite materials by combining Pd and Au in a multi-layer coating structure on the Cu core. The composite structure leverages the oxidation resistance of Pd and the superior corrosion resistance of Au in high-humidity environments, achieving both long-term storage characteristics and reliability in harsh conditions.
3Adaptability or versatility
If the bonding wire is thinned for fine pitch application, then adaptability to fine pitch is improved, but symmetry of the fishtail-shaped crimped part deteriorates
Solution Approach 1:
The patent applies local quality by optimizing the coating thickness distribution: the Au layer (5-20 nm) on top of the Pd layer provides excellent ductility and formability even at thin wire diameters (15-50 μm), ensuring symmetric fishtail formation during crimping while maintaining fine pitch adaptability.
Solution Approach 2:
The patent uses parameter changes by precisely controlling the Au layer thickness (5-20 nm) on the Pd coating. This parameter optimization ensures that even when the wire is thinned for fine pitch applications, the coating provides sufficient ductility and formability for symmetric fishtail crimping, resolving the contradiction between fine pitch adaptability and crimped part symmetry.
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 significantly improves 2nd bondability and symmetry of the fishtail-shaped crimped part, while reducing failure rates in high-humidity tests, extending the lifetime of bonded parts by 1.5 times compared to conventional Cu bonding wires, and enabling reliable performance in harsh environments.
Implementation Method 1
Cu is more susceptible to oxidation than Au, and a simple copper bonding wire is difficult to be stored for a long period of time... In order to solve the problem of oxidation of Cu bonding wire, there has been proposed a Cu bonding wire in which a surface of Cu wire is coated with a noble metal
Implementation Method 2
a skin alloy layer containing Au and Pd provided on a surface of the coating layer... adjusting a concentration of Cu at an outermost surface of the wire to 1 to 10 at%... controlling mutual diffusion at the bonding interface
Implementation Method 3
ball bonding featuring a thermal compressive bonding technique with the aid of ultrasound
Data Source
AI summary
There is provided a bonding wire for a semiconductor device including a coating layer having Pd as a main component on a surface of a Cu alloy core material and a skin alloy layer containing Au and Pd on a surface of the coating layer, the bonding wire further improving 2nd bondability on a Pd-plated lead frame and achieving excellent ball bondability even in a high-humidity heating condition. The bonding wire for a semiconductor device including the coating layer having Pd as a main component on the surface of the Cu alloy core material and the skin alloy layer containing Au and Pd on the surface of the coating layer has a Cu concentration of 1 to 10 at% at an outermost surface thereof and has the core material containing a metallic element of Group 10 of the Periodic Table of Elements in a total amount of 0.1 to 3.0% by mass, thereby achieving improvement in the 2nd bondability and excellent ball bondability in the high-humidity heating condition. Furthermore, a maximum concentration of Au in the skin alloy layer is preferably 15 at% to 75 at%.