Slotted Laminated Suspension Flexure for Hard Disk Drive Bonding
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Solution Overview
Problem
Conventional solder jet bonding in hard disk drive head stack assemblies often results in solder bridging and polyimide burning, leading to high defect rates due to the continuous polyimide layer between traces, which introduces contaminants and reduces yield.
Innovation Solution
A laminated structure with a metallic layer, a dielectric layer, and slots formed in both, where conductive traces terminate as bonding pads extending into the slots, reducing the likelihood of solder bridging and polyimide burning by creating gaps between adjacent pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a continuous layer of polyimide is used between traces for bonding pads, then the bonding pad structure is simple and continuous, but solder bridging occurs between adjacent traces and polyimide burning introduces contaminants
Solution Approach 1:
The continuous polyimide layer is segmented by creating slots that extend from the edge of the suspension flexure toward the bonding pad region. These slots divide the polyimide base into separate regions, physically isolating adjacent bonding pads and preventing solder bridging between them while maintaining structural integrity.
Solution Approach 2:
Polyimide material is selectively removed in the form of slots from the bonding pad region. By extracting the polyimide base material in controlled areas, the invention eliminates the source of solder bridging and burning contaminants while preserving the polyimide's insulating function in regions where it is still needed.
2Productivity
If solder jet bonding is performed on continuous polyimide base, then the process is straightforward, but polyimide burning occurs and introduces contaminants in the bonding region
Solution Approach 1:
The polyimide material is extracted in the form of slots from the bonding pad region, removing the combustible material that causes burning during solder jet bonding. This eliminates the source of contaminants while allowing the bonding process to proceed efficiently on the exposed metallic layers.
Solution Approach 2:
The slots, which remove polyimide material, convert the harmful effect of polyimide burning into a beneficial outcome by eliminating the contaminant source. The same material removal that prevents burning also improves solder wetting and bonding quality by exposing clean metallic surfaces.
3Reliability
If slots are formed in polyimide base to prevent solder bridging, then solder jet bonding yield improves, but the structure becomes more complex
Solution Approach 1:
The suspension flexure structure is segmented by adding slots, but these slots follow simple geometric patterns that extend from the edge toward the bonding region. This segmentation provides functional separation without creating complex three-dimensional structures, maintaining manufacturing simplicity.
Solution Approach 2:
The slot dimensions and positions are optimized to provide sufficient separation for preventing solder bridging while minimizing the overall structural impact. By carefully controlling slot width, length, and spacing, the design achieves high bonding yield without excessive complexity.
Data Source
AI summary
A laminated structure includes a metallic layer, a dielectric layer on the metallic layer, wherein the dielectric layer and metallic layer have a slot formed therein, and one or more conductive traces on the dielectric layer opposite the metallic layer, wherein the ends of the one or more traces terminate to form bonding pads extending into the slot. A method of forming a slotted laminated structure includes forming a metallic layer, forming a dielectric layer on the metallic layer, forming a slot in the dielectric layer and metallic layer, and forming one or more electrically conductive traces on the dielectric layer opposite the metallic layer, wherein ends of the one or more traces are formed to terminate with bonding pads extending into the slot.