Semiconductor Die Attachment Using Indium Braze for Vacuum Tubes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vacuum device technologies face challenges in achieving precise alignment and minimizing strain in ultra-high vacuum (UHV) environments due to thermal coefficient of expansion mismatches and the use of high-temperature braze materials, which lead to degraded sensor performance and increased package volume.
Innovation Solution
The use of low melting point, ductile metals like indium or indium alloys for die bonding, along with a pattern of small braze pads on both the semiconductor device and the substrate, allows for alignment through surface tension forces during vacuum processing, reducing strain and enabling efficient heat transfer while eliminating the need for intermediate pedestals and wire bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature braze materials are used to secure the semiconductor device during vacuum sealing, then the semiconductor device remains stable and does not move, but the thermal mismatch-induced strain increases significantly when cooled to room temperature
Solution Approach 1:
The patent changes the temperature parameter by using low melting point braze materials (melting below 200°C) instead of high-temperature braze materials. This allows the bonding process to occur at lower temperatures, reducing the thermal mismatch strain while still providing sufficient stability during vacuum sealing. The low melting point braze material melts during the sealing process to allow movement compensation, then solidifies to secure the device.
Solution Approach 2:
The patent introduces dynamic behavior by using braze material that changes state from solid to liquid and back during the vacuum sealing process. The braze material is designed to be solid at room temperature for stable bonding, melt during the sealing process to accommodate movement, and re-solidify to secure the final position. This dynamic phase change resolves the contradiction between stability during sealing and strain reduction.
2Stress or pressure
If the linear dimension of the braze pad is reduced to minimize strain, then the thermal mismatch strain decreases, but the heat transfer area between the semiconductor device and substrate is limited
Solution Approach 1:
The patent changes the material parameter by using low melting point braze material with high thermal conductivity. This allows the braze pad to remain small for strain reduction while the material itself provides efficient heat transfer. The low melting point characteristic enables the small pad to still provide adequate thermal coupling during the vacuum sealing process.
3Reliability
If wire-bonds are used to make electrical connections, then reliable electrical connection is achieved, but the package volume increases due to the annular ring of pads outside the semiconductor die
Solution Approach 1:
The patent merges the electrical connection function with the mechanical bonding function by using the same low melting point braze material for both purposes. The braze pads serve dual functions: providing mechanical support and thermal coupling, and establishing electrical connections. This eliminates the need for separate wire-bonds and reduces the package volume by removing the annular ring of external pads.
Solution Approach 2:
The braze material and braze pads are designed to perform multiple functions simultaneously: mechanical bonding, thermal coupling, and electrical conduction. This multi-functionality reduces the overall package complexity and volume by eliminating the need for separate wire-bonding infrastructure and external pad structures.
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 approach results in improved reproducibility, flatness, and reduced thermal mismatch-induced strain, leading to higher performance image sensors with enhanced resolution and reduced package volume, as well as the ability to maintain parallelism between critical components, thus improving the overall quality of vacuum devices.
Implementation Method 1
alignment through surface tension forces during vacuum processing
Implementation Method 2
enabling efficient heat transfer
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
There is described novel bonding and interconnect techniques including a spacer for use with semiconductor die for the creation of thermally efficient, physically compliant Ultra High Vacuum Tubes and the novel tube resulting therefrom.