Sputtering Target Backing Plate Brazing Layer
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Solution Overview
Problem
The existing brazing methods for sputtering targets with low thermal expansion coefficients, such as silicon, face issues with warping and brazing material seepage due to heat accumulation, which compromises bonding strength and product quality.
Innovation Solution
Incorporating a material with high thermal conductivity, such as copper or silver, into the brazing material or using a metal foil with specific thickness and area ratios to enhance the thermal conductivity of the braze bonding layer, thereby preventing brazing material seepage and maintaining the buffer effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the brazing material is thickened to prevent warping of the sputtering target, then the buffer effect against thermal expansion difference is improved, but heat accumulates and causes brazing material to melt and seep out from the bonded interface
Solution Approach 1:
The patent creates a composite brazing material by dispersing high thermal conductivity particles (silver, copper, or aluminum with 1-100 μm diameter) within the low-melting-point brazing material matrix (In, Sn, or their alloys). This composite structure combines the warping-prevention buffer effect of thick brazing material with the heat-dissipation capability of high-conductivity particles, preventing heat accumulation and brazing material seepage while maintaining thickness of 100-700 μm
Solution Approach 2:
The patent modifies the thermal conductivity parameter of the brazing material by adding high thermal conductivity particles (silver: 429 W/m·K, copper: 401 W/m·K, aluminum: 237 W/m·K) to the low-melting-point matrix. This parameter change enables the thick brazing layer to dissipate heat effectively during sputtering, preventing the heat accumulation that would otherwise cause brazing material melting and seepage
2Object-generated harmful factors
If the brazing material is thinned to prevent seepage, then brazing material seepage is reduced, but the buffer effect against warping is insufficient
Solution Approach 1:
The composite brazing material structure allows the use of thicker brazing layers (100-700 μm) without the risk of seepage, because the dispersed high thermal conductivity particles enable effective heat dissipation. This resolves the need to thin the brazing material, allowing the full buffer effect against thermal expansion differences to be utilized for warping prevention
3Reliability
If diffusion bonding method is used for high power sputtering, then heatproof temperature and cleanliness are improved, but it cannot be applied to brittle semiconductor materials and oxide materials
Solution Approach 1:
The patent changes the bonding temperature parameter by using low-melting-point brazing materials (In: 232°C, Sn: 232°C, or their alloys) instead of the high temperatures required for diffusion bonding. This temperature reduction makes the bonding process compatible with brittle semiconductor materials (Si, Ge) and oxide materials (PZT, HfO2, La2O3, MgO) that would be damaged by diffusion bonding temperatures, while the added high thermal conductivity particles ensure adequate heat dissipation
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 increased thermal conductivity of the braze bonding layer reduces brazing material melting and seepage, maintaining bonding strength and preventing warping, even with thicker braze bonding layers.
Implementation Method 1
a braze bonding layer which bonds the sputtering target and the backing plate contains a material having thermal conductivity that is higher than that of the brazing material
Data Source
AI summary
A sputtering target-backing plate assembly obtained by bonding a sputtering target and a backing plate using a brazing material, wherein a braze bonding layer which bonds the sputtering target and the backing plate contains a material having thermal conductivity that is higher than that of the brazing material in an amount of 5 vol % or more and 50 vol % or less, and a thickness of the braze bonding layer is 100 μm or more and 700 μm or less. An object is to prevent the seepage of the brazing material while maintaining the thickness of the braze bonding layer.