Thin Film Capacitor Lower Electrode Adhesion via Nickel Roughness
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Solution Overview
Problem
Thin film capacitors embedded in circuit boards experience interfacial peeling due to low adhesion between the nickel (Ni) lower electrode layer and the insulating resin layer, and existing solutions that enhance adhesion, such as roughening the copper (Cu) layer, increase the number of processes and the capacitor's thickness.
Innovation Solution
A thin film capacitor design featuring a lower electrode layer with a first Ni metal layer and a second Cu metal layer, where the first surface is roughened and covered by a thin second Cu layer that reflects its surface properties, enhancing adhesion to the insulating resin layer without increasing the overall thickness or number of processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Cu layer with thickness of about 5 μm is provided on the surface of the lower electrode layer of Ni and the surface of the Cu layer is roughened, then adhesion between the lower electrode layer and the insulating resin layer is enhanced, but the number of processes increases and the thickness of the entire capacitor increases
Solution Approach 1:
The patent combines the roughening function and adhesion enhancement function into a single integrated lower electrode layer structure. The first metal layer (Ni) provides both the roughened surface for adhesion and serves as the base electrode, eliminating the need for a separate Cu layer and roughening process. This merging of functions reduces the number of manufacturing processes while maintaining high adhesion to the insulating resin layer.
Solution Approach 2:
The patent changes the surface roughness parameter of the first metal layer to enhance adhesion. By controlling the surface roughness of the Ni layer (first metal layer) to be within a specific range (Rz: 0.5 μm to 5 μm), the patent achieves high adhesion to the insulating resin layer without requiring additional thick Cu layers or separate roughening processes.
2Reliability
If a Cu layer with thickness of about 5 μm is provided on the surface of the lower electrode layer of Ni and the surface of the Cu layer is roughened, then adhesion between the lower electrode layer and the insulating resin layer is enhanced, but the thickness of the entire capacitor increases
Solution Approach 1:
The patent merges the functions of the Ni layer and Cu layer into a single integrated lower electrode layer. The first metal layer (Ni) with controlled surface roughness performs both the electrical function and the adhesion function, eliminating the need for an additional 5 μm Cu layer. This integration maintains capacitor thickness while achieving high adhesion to the insulating resin layer.
Solution Approach 2:
The patent optimizes the surface roughness parameter of the first metal layer to enhance adhesion without increasing thickness. By controlling the surface roughness (Rz: 0.5 μm to 5 μm) of the Ni layer, the patent achieves high adhesion to the insulating resin layer while maintaining a thin overall structure, avoiding the need for thick Cu layers.
3Temperature
If Ni is used as the lower electrode layer material, then heat resistance is achieved, but adhesion to the insulating resin layer is low causing interfacial peeling
Solution Approach 1:
The patent changes the surface parameter of the Ni layer by controlling its surface roughness (Rz: 0.5 μm to 5 μm). This surface modification enhances the adhesion between the Ni layer and the insulating resin layer while preserving the heat resistance properties of Ni. The roughened surface provides mechanical interlocking with the resin layer, preventing interfacial peeling.
Solution Approach 2:
The patent applies different properties to different parts of the Ni layer. The bulk Ni layer maintains its heat resistance properties, while the surface of the Ni layer is modified to have high surface roughness for enhanced adhesion. This local differentiation allows the single Ni layer to simultaneously provide both heat resistance and high adhesion to the insulating resin layer.
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 achieves high adhesion between the lower electrode layer and the insulating resin layer, preventing interfacial peeling and minimizing structural thickness and process complexity, while also providing heat resistance and stress relief due to the thermal expansion coefficient matching of the second metal layer.
Implementation Method 1
The first surface has a surface roughness higher than that of the second surface
Implementation Method 2
The second metal layer reflects the surface property of the first surface
Implementation Method 3
the thickness of the second metal layer may be 0.1 times or more and 2.5 times or less a surface roughness Rz of the first surface
Implementation Method 4
the thermal expansion coefficient of the second metal layer may lie between those of the first metal layer and the insulating resin layer contacting the second metal layer. This can relieve a stress caused due to a difference in thermal expansion coefficient
Data Source
AI summary
Disclosed herein a thin film capacitor that includes a lower electrode layer, an upper electrode layer, and a dielectric layer disposed between the lower electrode layer and the upper electrode layer. The lower electrode layer includes a first metal layer positioned on a side facing the dielectric layer and a second metal layer positioned on a side facing away from the dielectric layer. The first metal layer has a first surface positioned on a side facing the second metal layer and a second surface positioned on a side facing the dielectric layer. The first surface has a surface roughness higher than that of the second surface. The second metal layer reflects a surface property of the first surface.