Laser Diode Electrode Pad Wettability Control for Solder Overflow
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Solution Overview
Problem
Conventional head gimbal assemblies for thermally assisted magnetic recording face issues with solder bonding, leading to short circuits and reduced performance and reliability due to limited solder connection areas and overflow, which affects the connection between the laser diode and suspension components.
Innovation Solution
The design incorporates an electrode pad layer with a solder-bonding pad and a solder-contact preventing part, where the solder-bonding pad has higher wettability and the preventing part has lower wettability, ensuring the solder connector touches only the bonding pad without the preventing part, thus preventing short circuits and ensuring reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used to connect the laser diode to the suspension, then electrical connection is achieved, but solder overflow occurs causing short circuits and reducing reliability
Solution Approach 1:
The electrode pad layer is designed with spatially varying solder wettability: the solder-bonding pad part has high solder wettability to attract and bond solder, while the solder-contact preventing part has low solder wettability to repel solder. This local quality differentiation ensures solder is confined to the bonding pad area, preventing overflow onto the semiconductor element and improving connection reliability.
2Ease of manufacture
If the laser diode structure is simplified for manufacturing, then production efficiency increases, but the precision of solder placement decreases leading to short circuits
Solution Approach 1:
The electrode pad layer incorporates regions with different solder wettability characteristics. The solder-bonding pad part is designed with high wettability to actively attract solder, while the solder-contact preventing part has low wettability to repel solder. This local quality differentiation provides self-aligning and self-confining properties for solder, ensuring precise solder placement without requiring complex manufacturing processes or additional alignment steps.
3Strength
If the solder connection area is increased to improve bonding strength, then connection strength increases, but the risk of solder short circuiting the semiconductor element increases
Solution Approach 1:
The electrode pad layer is designed with spatially differentiated solder wettability: the solder-bonding pad part has high solder wettability to provide strong solder bonding, while the solder-contact preventing part has low solder wettability to prevent solder from reaching the semiconductor element. This local quality differentiation allows the solder connection area to be sufficiently large for strong bonding while simultaneously confining solder to safe zones, eliminating short circuit risk.
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 configuration ensures that the solder is connected to the predetermined position on the laser diode without touching the solder-contact preventing part, preventing short circuits and enhancing the reliability and performance of the thermally assisted magnetic head and head gimbal assembly.
Implementation Method 1
the solder-bonding pad part has higher wettability
Implementation Method 2
the preventing part has lower wettability
Data Source
AI summary
The laser diode includes an electrode pad layer, being connected to an electrode, and an outer surface in which the electrode pad layer is formed. The electrode pad layer includes a solder-bonding pad part and a solder-contact preventing part. The solder-contact preventing part is formed with small wettability material having solder wettability which is smaller than solder wettability of the solder-bonding pad part. The solder-bonding pad part and the solder-contact preventing part are formed so that a pad height, being a height from the outer surface to a surface of the solder-bonding pad part, is larger than a preventing height, being a height from the outer surface to a surface of the solder-contact preventing part.