Suspension Substrate Insulating Layer Edge Alignment for Crack Resistance
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Solution Overview
Problem
Conventional substrates for suspension experience crack generation in the insulating layer at the boundary region between metal supporting and non-metal supporting areas due to stress concentration, which affects the integrity and functionality of hard disc drives.
Innovation Solution
A substrate design featuring a metal supporting substrate, an insulating layer, a wiring layer, and a cover layer, where the edge of the insulating layer coincides with or is closer to the wiring layer than the cover layer at the boundary region, reducing stress concentration and crack formation. Additionally, features like auxiliary wiring layers and widened edge regions are incorporated to enhance crack resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a part of the metal supporting substrate is removed to achieve lower stiffness, then the substrate flexibility is improved, but cracks are easily generated in the insulating layer at the boundary region
Solution Approach 1:
The patent applies local quality by making the insulating layer thickness non-uniform: it is thicker at the boundary region between metal and non-metal supporting substrate areas, and thinner in other regions. This localized thickness variation strengthens the insulating layer precisely where stress concentration occurs during substrate flexing, preventing cracks while maintaining overall substrate flexibility.
Solution Approach 2:
The patent implements beforehand cushioning by pre-reinforcing the insulating layer at the boundary region before any cracking can occur. The increased thickness at this location acts as a preventive measure, cushioning against the stress concentration that naturally arises when the substrate is flexed during hard disc drive operation.
2Volume of moving object
If the insulating layer is made thinner to reduce substrate thickness, then the substrate for suspension is miniaturized, but stress concentration increases at the boundary region
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatially varying insulating layer thickness. The layer is thin in regions where stress is low to achieve miniaturization, but locally thickened at the boundary region where stress concentration occurs, thus maintaining structural integrity while reducing overall substrate thickness.
Data Source
AI summary
The present invention provides a substrate for suspension that includes a first structural part including a metal supporting substrate, an insulating layer, a wiring layer, and a cover layer, and a second structural part formed so as to extend continuously from the first structural part and has no metal supporting substrate. A position of an edge of an upper surface of the insulating layer coincides with a position of an edge of the lower surface of the cover layer or the position of the edge of the upper surface of the insulating layer is positioned on a side closer to the wiring layer than to the position of the edge of the lower surface of the cover layer at a boundary region between the first structural part and the second structural part.