Hard Disk Drive Flexure Sidewalls Prevent Solder Bridging
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Solution Overview
Problem
The increasing number of connection pads in hard disk drives due to new technologies such as dual thermal flying height control and two-dimensional magnetic recording makes it challenging to connect slider pads to flexure pads using traditional solder ball jet (SBJ) methods, leading to issues with solder bridges and deformation during pre-solder processes like solder paste printing and reflow.
Innovation Solution
The implementation of a multi-stage pre-solder solder plating process with sidewalls around flexure electrical pads to form pre-solder bumps, which are then reflowed to create solder fillets, preventing short circuits and allowing for reliable electrical connections in high-density, small-pitch configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional solder ball jet (SBJ) methods are used to connect slider pads to flexure pads, then the connection process is simple, but solder bridges and deformation occur during pre-solder processes like solder paste printing and reflow
Solution Approach 1:
The patent applies preliminary action by forming sidewalls around the flexure electrical pads before applying the solder paste. This pre-structural preparation creates physical barriers that prevent solder from bridging between adjacent pads during the subsequent reflow process, thereby eliminating solder bridges while maintaining reliable electrical connections.
Solution Approach 2:
The sidewalls act as an intermediary structure between the electrical pads and the solder paste. These sidewalls are formed by depositing material (such as polyimide or other insulating materials) around the pads, creating a physical barrier that mediates the interaction between the solder paste and adjacent pads, preventing unwanted solder bridging while allowing proper solder joints to form.
2Adaptability or versatility
If the number of connection pads is increased to support new technologies like dual thermal flying height control and two-dimensional magnetic recording, then functionality is improved, but the complexity of connecting pads using traditional methods increases
Solution Approach 1:
By pre-forming sidewalls around each electrical pad before applying solder paste, the patent creates a systematic approach that scales well with increased pad density. This preliminary structural preparation ensures that even with many closely spaced pads, the sidewalls provide consistent barriers that prevent solder bridges, making the connection process manageable and reliable for high-density configurations.
3Reliability
If sidewalls are formed around flexure electrical pads before solder paste printing, then short circuits are prevented, but an additional manufacturing step is required
Solution Approach 1:
The sidewalls serve as an intermediary barrier structure that is formed by depositing insulating material around the electrical pads. This intermediate layer prevents direct contact between solder paste and adjacent pads, eliminating short circuits. The sidewalls are formed using standard deposition processes that can be integrated into existing manufacturing lines, balancing reliability improvement with manufacturing feasibility.
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 approach effectively prevents short circuits and ensures reliable electrical connections between slider and flexure pads, even in high-density configurations, by controlling the formation and reflow of pre-solder bumps, thus enhancing manufacturing efficiency and reducing costs associated with head-gimbal assembly failures.
Implementation Method 1
form sidewalls around the flexure electrical pads
Implementation Method 2
heated, such as by using a laser in a solder bond jet (SBJ) procedure
Implementation Method 3
the pre-solder bumps are then reflowed to create solder fillets
Implementation Method 4
solder balls between the suspension electrical pads and the slider electrical pads are heated
Data Source
AI summary
A hard disk drive flexure assembly includes a base layer, a conductive layer, a plurality of electrical pads over the conductive layer, and a sidewall layer including sidewalls on each side of and extending higher than a corresponding electrical pad. Pre-solder bumps are formed between the sidewalls and over each pad. Use of sidewalls prevents the pre-solder bumps from undesirably bridging to an adjacent electrical pad and forming a short circuit, which might otherwise cause head-gimbal assembly (HGA) manufacturing failures and consequent increased cost. These techniques are especially relevant with narrow, high-density, small pitch electrical pads.