Friction Stir Welding Sputtering Target Bonding
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Solution Overview
Problem
Existing sputter target and backing plate assemblies face challenges with material stress and hermetic seal issues due to high yield strength coefficients and poor weldability of certain alloys, leading to deflection, particle generation, and decreased uniformity during sputtering.
Innovation Solution
Friction stir welding is used to bond sputter targets to backing plates with high yield strength alloys, such as Al 7000 series and Cu alloys, creating a strong and durable joint along the circumferential interface or major plate interfacial surface, avoiding high-temperature processes that can cause recrystallization or weak bond formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength backing plate materials such as Al-SiC composite or Al alloy 7075 are used, then the assembly exhibits significant strength and yield strength, but the materials are impossible to weld at circumferential surfaces due to chemical composition and poor weldability
Solution Approach 1:
The patent replaces traditional thermal welding processes with friction stir welding, which uses mechanical friction and stirring action to create metallurgical bonds. This mechanical approach allows welding of high-strength alloys like Al 7075 and Al-SiC composites that are otherwise unweldable due to their chemical composition and tendency to crack during thermal cycling.
Solution Approach 2:
The invention changes the welding process parameters by using controlled friction heat generation and stirring speed to create bonds without melting the base materials. This parameter change enables welding of materials with poor weldability by avoiding the thermal cycles that cause cracking in high-strength alloys.
2Strength
If high temperature bonding processes such as diffusion bonding are used to join Al alloy target to Cu alloy backing plate, then bonding is achieved, but Al alloy target recrystallization or weak bond strength occurs due to formation of brittle intermetallic compounds
Solution Approach 1:
The patent replaces high-temperature diffusion bonding with friction stir welding, which uses mechanical friction and stirring to create bonds at lower temperatures. This avoids the formation of brittle intermetallic compounds between Al and Cu alloys while preventing target material recrystallization.
Solution Approach 2:
The invention changes the bonding temperature parameter by using friction stir welding operating at significantly lower temperatures than diffusion bonding. This parameter change prevents unwanted metallurgical reactions while still achieving strong bonds through mechanical interlocking and localized plastic deformation.
3Reliability
If soft solders are used to join sputter target to backing plate, then stresses during heating and cooling are accommodated, but the bonds have insufficient strength and yield strength to withstand sputtering stresses
Solution Approach 1:
The patent creates a composite bond structure through friction stir welding that combines the benefits of mechanical interlocking and metallurgical bonding. The stirred zone creates a fine-grained composite structure with enhanced strength while maintaining stress accommodation capabilities through the plasticized material in the weld zone.
Solution Approach 2:
The invention changes the bond material properties by creating a friction stir welded joint with controlled microstructure. The stirred zone produces a fine-grained, plasticized material that has both high strength and ductility, allowing it to accommodate thermal stresses while withstanding sputtering loads.
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 friction stir welding method provides a high-strength bond that withstands sputtering stresses and maintains assembly integrity, ensuring a hermetic seal without damaging the target material microstructure, thus improving sputtering performance and uniformity.
Implementation Method 1
Friction stir welding is used to bond sputter targets to backing plates
Implementation Method 2
The joint existing around the circumferentially extending target/backing plate interface may then be bonded via friction stir welding
Data Source
AI summary
A method for producing a sputtering target assembly bonded to a backing plate. The method includes bonding a target to a high strength backing plate and further creating a vacuum seal between the target and the backing plate using friction stir welding processes.