Semiconductor Laser Bonding Film Composition for Low-Temperature Reliability
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Solution Overview
Problem
Existing thin solder films for semiconductor laser bonding do not achieve high performance and low melting points, leading to issues such as poor wetting, void formation, and thermal stress that degrade the performance of light-emitting elements.
Innovation Solution
A thin film composition comprising 7.2-14.0 wt% Au, 0.1-4.4 wt% Ag, 0.1-10.1 wt% Cu, with a Cu layer covering one surface and a diffusion prevention layer containing Pt and Cr, which includes a Cr layer and a Pt layer, to prevent diffusion and enhance adhesion, is used for semiconductor laser bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ag layer is disposed between Sn layer and Au layer to inhibit Au diffusion, then poor wetting and Kirkendall voids are reduced, but the melting point cannot be sufficiently lowered
Solution Approach 1:
The patent uses a composite thin film structure with multiple layers (Sn, Ag, Cu, Au) where each layer contributes specific properties. The Sn-Ag-Cu-Au composite composition achieves both low melting point (through eutectic formation) and high reliability (through diffusion barrier and wetting enhancement), resolving the contradiction between melting point reduction and reliability maintenance.
Solution Approach 2:
The patent optimizes the compositional parameters of the thin film, specifically controlling Ag content (5.5 wt% or less) and Cu content (1.5 wt% or less) to achieve the desired melting point while maintaining reliability. By adjusting these compositional parameters, the eutectic temperature is lowered without compromising the protective functions of the Ag layer.
2Reliability
If Ag content is increased to improve wetting, then surface oxidation is reduced, but melting point reduction becomes insufficient
Solution Approach 1:
The patent changes the compositional parameters by introducing Cu and Au elements alongside controlled Ag content. This multi-element compositional adjustment creates a eutectic system with lower melting point while the Ag layer maintains its wetting enhancement function, resolving the contradiction between wetting quality and melting point.
3Temperature
If Cu content is increased to lower melting point, then eutectic temperature is reduced, but diffusion control becomes challenging
Solution Approach 1:
The patent creates a composite structure where Cu layer is disposed on Sn layer, and Ag layer is disposed between Cu layer and Au layer. This composite arrangement allows Cu to lower the melting point through eutectic formation while the Ag layer acts as a diffusion barrier to control element mixing, simultaneously achieving both objectives.
Solution Approach 2:
The Ag layer serves as an intermediary between Cu and Au layers, mediating the interaction between these elements. It allows Cu to contribute to melting point reduction while preventing excessive diffusion of Au into Sn and Cu, thus maintaining diffusion control despite higher Cu content.
4Reliability
If multiple layers are added to improve performance, then wetting and diffusion control are enhanced, but film complexity increases
Solution Approach 1:
The patent segments the thin film into distinct functional layers (Sn layer, Cu layer, Ag layer, Au layer) where each layer performs a specific function. This segmentation allows optimization of each layer's thickness and composition independently, achieving high performance while maintaining a manageable layered structure.
Solution Approach 2:
The patent designs the thin film structure where layers serve multiple functions: Sn provides base adhesion and low melting point, Cu enhances melting point reduction and electrical conductivity, Ag provides diffusion barrier and wetting enhancement, and Au offers surface stability. This multi-functionality reduces the need for additional specialized layers, controlling overall complexity.
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
The solution provides a thin film with a melting point of 210°C or less, reduced void formation, and improved reliability, enabling efficient and durable semiconductor laser bonding.
Implementation Method 1
a Cu layer made of Cu is disposed all over one surface of the solder layer
Implementation Method 2
a Ag layer is disposed between a Sn layer and a Au layer, inhibiting the diffusion of Au contained in the Au layer into the Sn layer
Implementation Method 3
The thin film for semiconductor laser bonding has high performance and a low melting point
Data Source
AI summary
A thin film for semiconductor laser bonding includes a solder layer that contains 7.2-14.0 wt % Au, 0.1-4.4 wt % Ag, and 0.1-10.1 wt % Cu with the remainder except unavoidable impurities being Sn.