Wiring Board Multi-Layer Electrode Crack Prevention
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Solution Overview
Problem
As electrodes on wiring boards are downsized due to increasing functionality of electronic components, the connection area between electrodes and the insulating layer becomes smaller, leading to potential cracks and incomplete connections, which can cause operational issues with electronic components.
Innovation Solution
A wiring board design featuring a specific layered structure including a first conductor layer with nickel or chromium, a second conductor layer with copper, a third conductor layer with nickel and an overhanging part, and a fourth conductor layer with gold, which enhances connection strength and stress distribution, preventing cracks and ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the size of electrodes is decreased to accommodate higher functionality electronic components, then the number of electrodes and functionality increase, but the connection area between electrodes and insulating layer becomes smaller leading to reduced connection strength
Solution Approach 1:
The electrode structure is divided into multiple conductor layers (first conductor layer with nickel/chromium, second conductor layer with copper, third conductor layer with nickel, and fourth conductor layer with gold), where each layer serves specific functions. This segmentation allows the electrode to maintain small footprint while achieving sufficient connection strength through the combined effect of multiple layers with different properties.
Solution Approach 2:
The electrode employs a composite multi-layer structure combining different metals (nickel, chromium, copper, gold) with distinct properties. The first conductor layer uses nickel or chromium for adhesion to insulating layer, the second layer uses copper for electrical conductivity, the third layer provides corrosion resistance, and the fourth layer offers oxidation resistance. This composite structure achieves both small size and strong connection simultaneously.
2Adaptability or versatility
If the connection area is reduced due to downsized electrodes, then the electrode size decreases for higher functionality, but cracks may occur between electrodes and insulating layer due to stress
Solution Approach 1:
The multi-layer conductor structure acts as a stress buffer before cracks can propagate. The different metal layers have different mechanical properties and thermal expansion coefficients, creating a gradient that absorbs and distributes stress. This beforehand cushioning prevents stress concentration at the electrode-insulating layer interface, eliminating the root cause of crack formation even with reduced connection area.
3Strength
If a multi-layer conductor structure is implemented to improve connection strength, then connection reliability improves, but the device complexity increases
Solution Approach 1:
Each conductor layer performs multiple functions simultaneously. For example, the first conductor layer provides both adhesion to the insulating layer and structural support, while the copper layer provides both electrical conductivity and stress distribution. This multi-functionality reduces the need for additional specialized layers, thereby limiting the increase in device complexity while achieving improved connection strength.
Data Source
AI summary
A wiring board of the present disclosure comprises an insulating layer, a first conductor layer located on the surface of the insulating layer and containing any one of nickel and chromium, a metal belonging to group of the periodic table; or a metal belonging to group of the periodic table, a second conductor layer located inside the outer circumferential edge on the first conductor layer and containing copper, a third conductor layer located on the surface of the insulating layer in a state of covering the first conductor layer and the second conductor layer and containing nickel, and a fourth conductor layer located in a state of covering the third conductor layer and containing gold. The third conductor layer has an overhanging part extending outward from the outer circumferential edge of the first conductor layer, and the fourth conductor layer is located between the overhanging part and the insulating layer.