SnBiAg Solder Connection for Radiation Detector Thermo-Mechanical Stability
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Solution Overview
Problem
Current radiation detector devices for medical imaging, particularly in CT scanners, face mechanical and thermo-mechanical stress due to rotational g-forces and thermal cycling, which degrade the performance of Cadmium-based semiconductor materials, and existing lead-free solders lack the necessary mechanical and thermal stability.
Innovation Solution
A radiation detector device using a solder alloy of Bismuth, Tin, and Silver (SnBiAg) for connecting the detector and readout substrates, which provides improved mechanical and thermal stability, thermal conductivity, and reliability, suitable for high-stress medical imaging applications like CT scanners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free solder materials are used for environmental reasons, then environmental compliance is improved, but mechanical and thermo-mechanical performance deteriorates under strong mechanical requirements
Solution Approach 1:
The patent employs a ternary solder alloy composite consisting of Bismuth (54-60 wt%), Tin (35-43 wt%), and Silver (0.01-2 wt%). This composite material combines the low melting point advantage of SnBi alloy with the mechanical strength and thermal conductivity enhancement provided by Silver particles, achieving both environmental compliance and improved reliability under mechanical stress and thermal cycling conditions.
Solution Approach 2:
The patent optimizes the compositional parameters of the solder alloy by precisely controlling the weight percentages of Bismuth, Tin, and Silver within specific ranges. Additionally, the melting temperature is controlled within 130-150°C and Silver particle size within 1-10 μm, thereby achieving optimal balance between low-temperature processing compatibility and mechanical/thermo-mechanical performance.
2Temperature
If low melting temperature solder is used for temperature sensitive Cadmium-based detector substrates, then thermal damage to detector substrate is prevented, but mechanical strength and reliability under elevated g-forces deteriorates
Solution Approach 1:
The ternary SnBiAg solder alloy creates a composite structure where Silver particles are distributed within the SnBi matrix. This composite provides both low melting temperature (130-150°C) for thermal sensitivity compatibility and enhanced mechanical strength to withstand elevated g-forces during CT scanner operation.
Solution Approach 2:
The patent introduces Silver particles with specific size range (1-10 μm) locally distributed within the solder matrix to enhance mechanical properties at critical stress points while maintaining the overall low melting point characteristic of the SnBi base alloy, thereby achieving localized reinforcement without sacrificing thermal compatibility.
3Use of energy by stationary object
If binary SnBi solder alloy is used for low temperature bonding, then processing temperature is reduced, but mechanical and thermo-mechanical performance under thermal cycling deteriorates
Solution Approach 1:
The patent transforms the binary SnBi solder into a ternary SnBiAg composite material. The Silver component forms a reinforcing phase within the solder matrix that significantly improves resistance to thermal cycling and mechanical stress while maintaining the low bonding temperature advantage, thereby resolving the performance limitation of binary SnBi alloy.
Solution Approach 2:
By adding Silver to the SnBi alloy and controlling its concentration (0.01-2 wt%), the patent modifies the physical and mechanical parameters of the solder. This compositional change enhances creep resistance and fatigue strength under thermal cycling conditions while preserving the low melting point characteristic essential for temperature-sensitive detector substrates.
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 SnBiAg solder connection enhances the thermo-mechanical stability and extends the lifetime of the radiation detector device by maintaining performance under elevated mechanical and thermal conditions, outperforming binary SnBi alloys in terms of reliability and thermal cycling resistance.
Implementation Method 1
The solder comprises Bismuth, Tin and Silver... provides improved mechanical and thermal stability, thermal conductivity
Implementation Method 2
For the connection of the detector substrate and the readout substrate, a solder alloy comprising Bismuth, Tin and Silver is used
Data Source
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AI summary
The invention relates to a radiation detector device comprising a detector substrate for direct conversion of X-ray and/or gamma quanta to electrical charge, wherein the detector substrate comprises a semiconductor material comprising Cadmium, a readout substrate having a readout contact, a charge collector contact for collecting an electrical charge from said detector substrate, and a connection wherein the connection electrically interconnects the charge collector contact and the readout contact, wherein the connection comprises a solder connection wherein the solder comprises Bismuth, Tin and Silver.