Multi-Layer Plating Stack for Corrosion-Free Solder Bonding
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Solution Overview
Problem
Existing methods for forming plating films on conductor circuits face issues such as local corrosion, oxidation layer formation, and void generation during solder bonding, leading to inadequate solder bonding strength and stability, especially with the miniaturization and densification of wiring.
Innovation Solution
A plating stack is formed in layers, with a protective layer A deposited first, followed by a substitution plating layer B and then a reduction plating layer C, preventing local corrosion and ensuring stable film formation, thereby enhancing solder bondability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reduction plating is performed directly on the object to be plated, then plating film formation is achieved, but local corrosion occurs and oxidation layers form on the surface
Solution Approach 1:
A protective plating layer is formed on the object to be plated before performing reduction plating. This preliminary protective layer prevents local corrosion and oxidation layer formation during the subsequent reduction plating process, while still allowing the reduction reaction to proceed effectively.
Solution Approach 2:
The protective plating layer acts as an intermediary between the object to be plated and the reduction plating solution. It mediates the interaction by preventing direct harmful effects (corrosion and oxidation) while enabling the desired plating film formation through controlled reduction reactions.
2Productivity
If catalysts such as palladium are added to enable reduction plating, then plating proceeds, but local corrosion and oxidation layer formation occur
Solution Approach 1:
The protective plating layer is formed in advance before adding catalysts for reduction plating. This preliminary protection ensures that when catalysts are introduced to enable plating progression, the underlying object remains protected from corrosion and oxidation.
Solution Approach 2:
The protective plating layer serves as an intermediary barrier that allows catalysts to function effectively for plating progression while preventing direct contact between the catalysts and the object to be plated, thereby avoiding corrosion and oxidation.
3Loss of substance
If the plating film thickness is thin to avoid excessive material use, then cost is reduced, but voids are likely to generate during solder bonding
Solution Approach 1:
A composite plating structure is created with multiple layers (protective plating layer and reduction plating layer). This composite structure provides sufficient thickness and compositional gradient to prevent void formation during solder bonding, while optimizing material consumption by using different materials for different functional requirements.
4Device complexity
If substitution plating is used instead of reduction plating, then process simplicity is maintained, but film thickness is limited and local corrosion occurs
Solution Approach 1:
The plating process is segmented into two distinct stages: substitution plating to form a protective layer, followed by reduction plating to form the functional plating film. This segmentation allows each process to optimize its strengths while avoiding the weaknesses of using either method alone.
Solution Approach 2:
The final plating structure is a composite of materials formed by substitution plating and reduction plating. This composite approach enables achieving greater film thickness and better corrosion resistance than either method could provide individually, while maintaining reasonable process complexity.
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 method produces a plating stack with high solder bonding strength and stability, reducing the likelihood of void formation and ensuring reliable solder bonding.
Implementation Method 1
a plating layer B mainly composed of a third metal is deposited on the plating layer A... the plating layer B is a substitution plating layer formed by a substitution reaction between an ion of the third metal contained in a substitution plating solution, and the first metal contained in the object to be plated or the second metal contained in the plating layer A
Implementation Method 2
a plating layer C mainly composed of the second metal, the third metal, or a fourth metal is deposited on the plating layer B... the plating layer C is a reduction plating layer not mainly composed of gold and/or nickel, formed by a redox reaction between a reducing agent and a metal ion contained in a reduction plating solution
Data Source
AI summary
In the method for producing a plating stack, a plating layer A mainly composed of a second metal is deposited on an object to be plated S mainly composed of a first metal by a substitution reaction, then a plating layer B mainly composed of a third metal is deposited on the plating layer A, and then a plating layer C mainly composed of the second metal, the third metal, or a fourth metal is deposited on the plating layer B by a redox reaction. A concrete configuration of plating layers includes, for example, the plating layer A is gold, platinum or silver, the plating layer B is palladium, and the plating layer C is palladium.