Disk Drive Suspension Terminal Design for Short-Circuit Prevention
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Solution Overview
Problem
The increasing density of terminals and wirings in disk-drive suspensions leads to a risk of short-circuiting between adjacent solder bumps, while reducing the amount of solder to prevent this can result in connection defects, and existing methods to reduce bump height compromise alignment tolerance.
Innovation Solution
A disk-drive suspension design featuring terminals with a narrow and wide part configuration, where the bump height is greater than the terminal width, allowing for planarization and alignment to enhance connection accuracy and prevent short-circuits, with a connection method involving planarization and melting of bumps to secure reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the intervals between terminals are made smaller to increase terminal density, then the productivity and functionality of the suspension are improved, but the risk of short-circuiting between adjacent solder bumps increases
Solution Approach 1:
The terminal is designed with non-uniform width, featuring a narrow central portion and wider end portions. This local variation in geometry allows the terminal to maintain high density while controlling bump dimensions to prevent short-circuits. The narrow central portion reduces the bump width at the critical connection point, increasing spacing between adjacent bumps.
2Reliability
If the amount of solder constituting the bump is reduced to prevent short-circuiting, then the short-circuit risk is lowered, but the possibility of connection defects increases
Solution Approach 1:
The invention changes the geometric parameters of both the terminal and bump. The terminal width is varied along its length (narrower at center, wider at ends), and the bump height is specifically controlled to be greater than the terminal width. This parameter optimization ensures adequate connection strength while preventing short-circuits between adjacent bumps.
3Reliability
If the height of the bump is reduced to decrease the width of the central part, then the short-circuit risk is reduced, but the alignment tolerance for terminals is lowered
Solution Approach 1:
Instead of reducing bump height to prevent short-circuits, the invention inverts the approach by maintaining or increasing bump height while controlling bump width through terminal geometry. The bump height is made greater than the terminal width, providing both short-circuit prevention and adequate alignment tolerance through the vertical dimension rather than horizontal reduction.
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 design effectively reduces the risk of short-circuits between adjacent terminals while maintaining alignment accuracy and ensuring robust connections, even at high terminal densities, by maintaining sufficient bump height and width ratios.
Implementation Method 1
a technique described in, for example, JP H07-320434 A and JP H11-110925 A is known. In the method of these literatures, a solder bump is formed on a terminal, the bump is then planarized
Implementation Method 2
the bump is melted and is joined to the terminal of the connection counterpart
Data Source
AI summary
A disk-drive suspension includes a load beam, a flexure laid on top of the load beam, a first terminal provided on the flexure, and a first bump arranged on a top surface of the first terminal. The first terminal includes a narrow part having a first width in a first direction and including a center of the first terminal, and a wide part having a second width in the first direction greater than the first width. The wide part and the narrow part are arranged in a second direction intersecting the first direction. The first bump has, at the center, a first height from a bottom surface of the first terminal. The first height is greater than the first width.