Core-Shell Composite Solder Paste for Low-Temperature Heat Dissipation
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Solution Overview
Problem
Current solder pastes face challenges in achieving high thermal conductivity while maintaining a low melting point, which is essential for efficient heat dissipation in electronic devices, as they often result in device deformation and poor mechanical properties due to high operating temperatures and thermal expansion.
Innovation Solution
A composite metal material with a Cu@Ag@Sn or Cu@Ni@Sn core-shell structure is developed, where a Cu core is coated with an Ag or Ni intermediate layer and an Sn shell, reducing the formation of high thermal resistance intermetallic compounds and enhancing thermal conductivity to 50.82 W/(m·K) at 85° C. with a melting point of 138.9° C., suitable for low-temperature welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Sn-Bi series alloys with low Bi content are used, then melting point is reduced below 140°C, but thermal conductivity remains low due to segregation of hard and brittle Bi
Solution Approach 1:
The patent applies composite materials by combining Cu particles with Sn-Bi alloy to form a composite solder material. The Cu particles serve as thermal conductivity enhancement agents dispersed within the Sn-Bi matrix, creating a composite structure that leverages the low melting point of Sn-Bi while incorporating the high thermal conductivity of Cu to overcome the thermal conductivity limitations of pure Sn-Bi alloys
Solution Approach 2:
The patent applies local quality by creating regions of different composition and properties within the solder material. The Cu particles are distributed throughout the Sn-Bi matrix, creating local zones of enhanced thermal conductivity without changing the overall low melting point characteristic of the Sn-Bi alloy system
2Reliability
If Bi content is increased to achieve eutectic composition, then thermal conductivity improves, but mechanical strength and drop impact resistance deteriorate
Solution Approach 1:
The patent uses composite materials by integrating Cu particles into the Sn-Bi alloy matrix. The Cu particles provide thermal conductivity enhancement while the Sn-Bi matrix maintains adequate mechanical properties, creating a balanced composite system that achieves both thermal and mechanical performance requirements
Solution Approach 2:
The patent applies local quality by creating heterogeneous structure with Cu particles distributed in the Sn-Bi matrix. This creates local regions of enhanced thermal conductivity while the surrounding Sn-Bi matrix provides the necessary mechanical strength and ductility
3Strength
If traditional SAC alloys are used, then mechanical strength is maintained, but welding temperature exceeds 240°C causing device deformation
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the base alloy composition from SAC (Sn-Ag-Cu) to Sn-Bi system. This compositional parameter change reduces the melting point from above 240°C to below 140°C while incorporating Cu particles to maintain thermal conductivity and mechanical properties through the composite structure
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 effectively combines high thermal conductivity with a low melting point, addressing the limitations of existing solder pastes by improving thermal performance and mechanical stability, enabling efficient heat dissipation and reduced risk of device damage during welding.
Implementation Method 1
the thermal conductivity of Sn—Bi series solders can be increased from 21.4 W/(m·K) to 50.82 W/(m·K) at 85° C.
Implementation Method 2
an eutectic Sn-58Bi alloy has a melting point of 138° C.
Data Source
AI summary
The present invention relates to a composite metal material and a low-temperature solder paste with high thermal conductivity containing the same. The composite metal material is a Cu core/Ag intermediate layer/Sn shell type metal powder (Cu@Ag@Sn) or a Cu core/Ni intermediate layer/Sn shell type metal powder (Cu@Ni@Sn) with a particle size of 20-60μm. The low-temperature solder paste with high thermal conductivity is obtained by mixing the composite metal material with an Sn—Bi series alloy powder and a flux paste, can be used for welding of a variety of substrate, and is suitable for welding at a low temperature of lower than 150° C. The composite metal material of the present invention has a simple process, a low cost and high practicability, and poor heat dissipation and other problems of power devices after die bonding caused by low thermal conductivity of current solder pastes on the market are solved.