Zinc-Based Solder Alloy for Low-Temperature PCD Joining
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Solution Overview
Problem
Existing solder alloys require high temperatures for brazing, which can damage temperature-sensitive materials like polycrystalline diamond (PCD) due to their high melting points, necessitating a solution that allows for lower soldering temperatures without compromising shear strength.
Innovation Solution
A cadmium-free, silver-based solder alloy with a melting point range of 545 °C to 620 °C is developed, achieving shear strengths over 1,500 Newtons or 110 MPa, and is formulated with precise mass fractions of silver, copper, zinc, and tin to ensure ease of rolling and low brittleness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high melting point solder alloys are used for brazing, then shear strength is improved, but temperature-sensitive materials like PCD are damaged
Solution Approach 1:
The patent changes the chemical composition parameters of the solder alloy by replacing traditional high-melting-point alloys (such as nickel-based or cobalt-based alloys requiring temperatures above 650°C) with a zinc-based alloy system that has a lower melting point. This parameter change allows brazing to be performed at temperatures below 650°C, thereby protecting temperature-sensitive PCD materials from thermal damage while still achieving sufficient joint strength through optimized alloy composition.
Solution Approach 2:
The patent develops a composite zinc-based solder alloy containing multiple elements (Zn, Al, Mg, Mn, Si, Cu, Ni, Co, In, Ga, and their oxides) in specific proportions. This composite material approach creates a eutectic or near-eutectic composition that lowers the melting point while maintaining or enhancing mechanical properties. The synergistic combination of elements produces a alloy that achieves adequate shear strength at reduced brazing temperatures, resolving the contradiction between strength and thermal sensitivity.
2Object-affected harmful factors
If lower soldering temperatures are used, then temperature-sensitive materials are protected, but shear strength decreases
Solution Approach 1:
The patent optimizes the chemical composition parameters of the zinc-based solder alloy to achieve a eutectic or near-eutectic composition. By precisely controlling the content of alloying elements (Al: 3-15%, Mg: 2-10%, Mn: 1-5%, Si: 1-5%, Cu: 1-5%, Ni: 1-5%, Co: 1-5%, In: 1-5%, Ga: 1-5%), the alloy achieves a melting point below 650°C while maintaining high shear strength. This parameter optimization ensures that even at lower brazing temperatures, the resulting joint achieves sufficient mechanical strength.
Solution Approach 2:
The patent utilizes phase transition phenomena, specifically the eutectic reaction, to achieve complete melting and mixing of the solder alloy at relatively low temperatures. The eutectic composition allows the alloy to transform from solid to liquid phase at a single, well-defined temperature below 650°C, ensuring complete wetting and penetration into the joint. This phase transition mechanism ensures that the lower brazing temperature still produces a homogeneous, high-strength joint without leaving unmelted particles that would weaken the connection.
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 solder alloy enables soldering of temperature-sensitive materials like PCD at lower temperatures, maintaining high shear strength and avoiding damage, while being versatile for various material compositions.
Implementation Method 1
The solder alloy advantageously exhibits a comparatively low melting point, particularly in the range of 545 °C to a maximum of 620 °C
Data Source
Figure 1~2
AI summary
The invention relates to a solder alloy comprising: - a mass fraction of at least 35% to at most 62% silver, - a mass fraction of at least 10% to at most 30% copper, - a mass fraction of at least 10% to at most 26% zinc, wherein - the remaining mass fractions to 100%, except for unavoidable impurities, comprise at least one element selected from the group consisting of tin, gallium, manganese, nickel, and indium.