Plating Stack With Protective Layer For Solder Bonding
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Solution Overview
Problem
The challenge is to produce a plating stack with high bond strength for solder bonding on conductor circuits, while avoiding void generation at the interface between the object to be plated and the plating layer, especially with thin nickel film thicknesses.
Innovation Solution
A method involving the deposition of a plating layer A mainly composed of a second metal, followed by a plating layer B of palladium, and then a plating layer C of nickel, where a protective layer is interposed between the object to be plated and the catalytic layer of palladium to prevent local corrosion and oxidative layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If palladium or its alloys are added directly as catalysts on an object to be plated, then catalytic activity is improved, but local corrosion and oxidative layer formation occur on the object surface
Solution Approach 1:
A protective layer is introduced as an intermediary between the object to be plated and the palladium catalyst layer. This protective layer prevents direct contact between the catalyst and the object surface, thereby preventing local corrosion and oxidative layer formation while still allowing the catalyst to function. The protective layer acts as a mediator that separates the conflicting elements (catalyst and object surface).
Solution Approach 2:
The structure is segmented into multiple layers: the object to be plated, a protective layer, and then the palladium catalyst layer. This segmentation separates the catalytic function from the object surface, allowing the catalyst to perform its function without directly causing corrosion or oxidation on the object surface.
2Productivity
If film thickness of nickel plating layer is reduced to about 0.2 μm for miniaturization, then wiring density is improved, but voids generate at the interface and bondability deteriorates
Solution Approach 1:
The protective layer is applied in advance before depositing the nickel plating layer. This preliminary action prevents local corrosion and oxidative layer formation on the object surface, ensuring a clean interface that prevents void generation during subsequent nickel deposition. This allows thin nickel layers (0.2 μm) to be deposited without creating bonding defects.
3Ease of manufacture
If substitution plating is used to add palladium catalysts, then catalytic layer formation is simplified, but local corrosion and oxidative layer formation occur
Solution Approach 1:
The protective layer serves as an intermediary that allows substitution plating to proceed without causing harmful effects. It separates the object surface from the palladium deposition process, enabling the simplified substitution plating method to be used while preventing the local corrosion and oxidation that would otherwise occur during this process.
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 enables the stable production of a nickel layer with minimal voids, ensuring good solder bondability even with thin nickel film thicknesses, and reducing the consumption of expensive nickel.
Implementation Method 1
plating mainly by substitution reactions (hereinafter sometimes referred to as 'substitution plating')
Implementation Method 2
plating mainly by reduction reactions (hereafter, sometimes referred to as 'reduction plating')
Implementation Method 3
arranging a protective layer between a layer of palladium or its alloys (a catalytic layer) and the object to be plated
Data Source
AI summary
The problem of the present invention is to provide a plating stack (a stack of plating films) for applying on surface of conductor circuits or the like, the plating stack can maintain high bond strength when solder is bonded on that and can be produced stably. In the method for producing a plating stack of the present invention, 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 palladium is deposited on the plating layer A, and then a plating layer C mainly composed of nickel is deposited on the plating layer B by a redox reaction. The first metal is, for example, copper. The second metal is, for example, gold, platinum or silver.