Magnetic Head Bonding Pad Bridging Prevention
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Solution Overview
Problem
The existing magnetic heads in hard disk drives face issues with bonding pads shorting-circuit due to their small size and close proximity, limiting the number of functional pads and affecting the reliability and performance of the disk drive unit.
Innovation Solution
A magnetic head design featuring a slider substrate with multiple bonding pads arranged in a row, each with a seed layer and a solder nonwettable layer to prevent bridging and shorting-circuit, allowing for additional pads to be added and enhancing the read and write performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of bonding pads is increased to enhance functionality, then the magnetic head can connect to more elements for improved read and write performance, but the risk of bridging and shorting-circuit between adjacent pads increases due to limited space on the trailing edge
Solution Approach 1:
A solder nonwettable layer is introduced as an intermediary between adjacent bonding pads. This layer acts as a physical barrier that prevents solder from bridging between pads during the soldering process, thereby eliminating the shorting-circuit risk while allowing pads to be placed closer together for enhanced functionality
Solution Approach 2:
The invention changes the surface properties of the bonding pad structure by adding a solder nonwettable layer with specific material composition (such as nickel, titanium, or their alloys). This parameter change in surface wettability prevents solder adhesion on the nonwettable regions, enabling higher pad density without compromising reliability
2Adaptability or versatility
If the spacing between bonding pads is reduced to fit more pads on the trailing edge, then additional functional pads can be accommodated, but the manufacturing precision required to prevent shorting-circuit becomes more difficult to achieve
Solution Approach 1:
The solder nonwettable layer serves as a mediator that decouples the spacing requirement from the shorting prevention requirement. By placing this intermediate layer between pads, the design allows reduced pad spacing without increasing manufacturing difficulty, as the nonwettable layer provides inherent protection against solder bridging
Solution Approach 2:
The solder nonwettable layer is formed on the bonding pad structure before the soldering process. This preliminary action of creating a nonwettable surface ensures that even if manufacturing tolerances cause slight variations in pad spacing, the solder will not bridge between pads, thereby reducing the stringency of manufacturing precision requirements
Data Source
AI summary
A magnetic head includes a slider substrate having a trailing edge and multiple bonding pads arranged on the trailing edge in a row. Each of the bonding pads includes a seed layer adhered to the trailing edge and electrically connected with the slider substrate, a soldering layer formed on the seed layer and adapted for connecting with a suspension, and at least one solder nonwettable layer adhered to the trailing edge and connected with at least one side of the seed layer. The structure of the magnetic head is simple and stable, which can prevent the bonding pads bridging and shorting-circuit. An HGA and a disk drive unit with the same, a manufacturing method for the magnetic head are also disclosed.