Disk Drive Suspension Interconnect Using Chromium Tie Layer
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Solution Overview
Problem
Existing disk drive suspension interconnects face challenges in achieving reliable electrical grounding between copper circuit layers and stainless steel components due to limited space and metal compatibility issues, leading to high interconnect resistance and manufacturing inefficiencies.
Innovation Solution
The use of metallized vias with a chromium tie layer and copper conductor to establish a direct, low-resistance electrical connection between copper circuitry and stainless steel layers, eliminating the need for conductive adhesives and enhancing bonding through an additive manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive adhesive is used to connect copper traces to stainless steel foil, then electrical connection is achieved, but interconnect resistance is very high
Solution Approach 1:
A chromium tie layer is deposited onto the stainless steel foil to serve as an intermediary between the stainless steel and copper conductor. This chromium layer forms a metallurgical bond with both metals, replacing the non-conductive adhesive and significantly reducing interconnect resistance while maintaining reliable electrical connection.
Solution Approach 2:
The suspension interconnect structure uses a composite metallization approach with multiple layers (stainless steel foil, chromium tie layer, copper conductor) bonded together. This composite structure combines the advantages of each material: mechanical strength from stainless steel, bonding compatibility from chromium, and electrical conductivity from copper.
2Reliability
If spanning lead with conductive polymer is used for grounding, then grounding connection is achieved, but manufacturing complexity and labor intensity increase
Solution Approach 1:
The invention extracts and eliminates the complex spanning lead assembly process entirely. Instead of adding a separate lead that must be manually bent and adhered, the grounding connection is integrated directly into the suspension interconnect structure through the metallized via approach, simplifying both device structure and manufacturing process.
Solution Approach 2:
The grounding function is merged with the existing suspension interconnect structure. The chromium tie layer and copper conductor are deposited as part of the standard interconnect fabrication process, combining the grounding function with the electrical connection structure rather than treating it as a separate assembly step.
3Ease of manufacture
If conductive adhesive is used for bonding, then connection is achieved, but drive contamination increases
Solution Approach 1:
The chemical bonding mechanism of conductive adhesive is replaced with a metallurgical bonding system using chromium tie layer and copper conductor. This substitution eliminates organic adhesive materials that can outgas and contaminate the drive, while providing equivalent or superior bonding performance through vacuum-compatible deposition processes.
4Area of stationary object
If limited space is used for grounding connection, then compact design is achieved, but reliable grounding becomes difficult
Solution Approach 1:
The chromium tie layer is applied locally at the via location where grounding connection is needed, concentrating the bonding function in a small area. This localized approach allows reliable grounding to be achieved within the limited space constraints by focusing the metallurgical bonding precisely where required, rather than requiring large connection areas.
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 solution provides a highly conductive, adhesive-free connection with improved signal fidelity and manufacturing efficiency, enabling better grounding of disk drive sliders and facilitating the addition of multiple circuit layers while reducing contamination and labor costs.
Implementation Method 1
depositing a tie layer through the insulative layer onto the grounding layer in bonding relation with the ground layer
Implementation Method 2
depositing a conductor onto both the conductive metal layer and the tie layer in conductive metal layer and tie layer bonding relation
Data Source
AI summary
An additive process disk drive suspension interconnect, and method therefor is provided. The interconnect has a metal grounding layer of typically stainless steel or copper metallized stainless steel, a metal conductive layer and an insulative layer between the metal grounding layer and the conductive metal layer. A circuit component such as a slider is electrically connected to the conductive layer along a grounding path from the circuit component and the conductive layer to the metal grounding layer through an aperture in the insulative layer. For improved electrical connection a tie layer is provided through the insulative layer onto the grounding layer in bonding relation with the ground layer. A conductor is deposited onto both the conductive metal layer and the tie layer in conductive metal layer and tie layer bonding relation, and the circuit component is thus bonded to the grounding layer by the conductor.