Electroless Ni/Pd/Au Plating for Wire Bonding Workability
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Solution Overview
Problem
The existing electroless Ni/Au and Ni/Pd/Au surface treatment technologies on printed circuit boards result in high hardness of the Ni layer, which reduces wire bonding workability due to increased deformation depth and hardness, making it difficult to achieve reliable connections with miniaturized Au wires.
Innovation Solution
The electroless surface treatment plating layers of nickel, palladium, and gold are optimized to have thicknesses of 0.02 to 1 μm, 0.01 to 0.3 μm, and 0.01 to 0.5 μm respectively, with the nickel layer thickness minimized to less than 1 μm to reduce hardness and increase the depth of wedge deformation, allowing for improved joinability and workability during wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Ni layer thickness is increased to 3 μm or more for electroless surface treatment, then the structural hardness is improved, but the wire bonding workability deteriorates due to increased hardness and reduced deformation depth
Solution Approach 1:
The patent applies parameter changes by reducing the Ni layer thickness from the conventional 3 μm or more to 1 μm or less. This parameter modification directly addresses the technical contradiction by lowering the hardness of the Ni layer, thereby enabling sufficient deformation depth (1.0 μm or more) during wire bonding while maintaining the protective function of the plating layers.
2Quantity of substance
If the Au wire diameter is reduced and Au thickness is minimized due to increased Au value, then the cost is reduced, but the wire bonding workability deteriorates
Solution Approach 1:
The patent addresses this contradiction by changing the parameter of Ni layer thickness to 1 μm or less, which compensates for the reduced Au wire diameter and thickness. The softer Ni layer enables adequate deformation depth even with thinner Au wires, thereby maintaining wire bonding workability while allowing cost reduction through minimized Au usage.
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 approach maximizes the joint area and improves wire bonding workability by reducing the hardness of the Ni layer, enabling effective bonding with Au wires and enhancing the bonding process's efficiency by increasing the depth of wedge deformation to 1.0 μm or more.
Implementation Method 1
electroless surface treatment plating layers of nickel, palladium, and gold are optimized to have thicknesses of 0.02 to 1 μm, 0.01 to 0.3 μm, and 0.01 to 0.5 μm respectively
Data Source
AI summary
A wire bonding joint structure of a joint pad in which electroless surface treatment plating layers of joint pads configured by a nickel layer/a palladium layer/a gold layer are connected to each other by a metal wire and when the metal wire is joined to the electroless surface treatment plating layer, a depth of the wire bonding pad formed by wedge deformation is 1.0 m or more.The electroless surface treatment layer of the joint pad can lower strength and hardness of the wire bonding pad of which the surface is treated to improve follow-up capability between a gold wire and the bonding pad, such that a joint area between the gold and the bonding pad is maximized, thereby increasing joinability at the wire bonding finish process by wedge pressure and greatly improving wire bonding workability.