Sputter Target Bonding Foil for Controlled Solder Thickness

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Solution Overview

Problem

Conventional sputter target assemblies face challenges in achieving good thermal and electrical contact between the target and backing plate, often requiring high temperatures and pressure, which can affect the target microstructure and lead to warpage and differential contraction due to thermal expansion differences.

Innovation Solution

A method involving the use of an ignitable heterogeneous stratified bonding foil between the sputter target and backing plate, which ignites to generate an exothermic reaction, melting the solder layers and bonding them without heating the assembly excessively, thus maintaining the target's microstructure and flatness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If soldering is used to join the sputter target to the backing plate, then good thermal and electrical contact is achieved, but the high temperature heating affects the target microstructure and causes warpage due to thermal expansion differences

Engineering Contradiction:

Improvethermal and electrical contact qualityVSAvoidtarget flatness and microstructure integrity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the temperature parameter by using a low-melting-point solder (melting point 140-220°C) instead of conventional high-temperature soldering materials. This allows the bonding process to occur at temperatures that do not affect the target microstructure or cause warpage, while still achieving good thermal and electrical contact between the target and backing plate.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a solder layer as an intermediary material between the sputter target and the backing plate. This solder mediator enables thermal and electrical contact while its low melting point ensures that the bonding process does not expose the target to damaging high temperatures, thus preserving target flatness and microstructure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If high pressure and temperature are applied during bonding, then strong bonding between target and backing plate is achieved, but the target microstructure is affected and warpage occurs

Engineering Contradiction:

Improvebond strengthVSAvoidtarget flatness

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the temperature parameter by selecting a solder with a low melting point (140-220°C), which allows bonding to occur at temperatures that do not cause target warpage or microstructure changes. The low temperature inherently reduces the pressure needed for bonding, thus achieving strong adhesion without compromising target flatness.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional soldering methods are used, then bonding is achieved, but solder layer thickness cannot be precisely controlled

Engineering Contradiction:

Improvebonding process simplicityVSAvoidsolder layer thickness uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-coating the sputter target and/or backing plate surfaces with a controlled thickness of solder layer before the bonding process. This pre-application of solder at controlled thicknesses (e.g., 0.005-0.010 inches) allows for precise control of the final solder layer thickness while maintaining ease of manufacture through a straightforward coating and bonding sequence.

Inventive Principle:

Principle #10Preliminary action

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 allows for precise control of solder layer thickness and maintains the target's metallurgical integrity, achieving a uniform target material thickness and symmetric magnetic leakage flux, resulting in improved film deposition uniformity on substrates.

Implementation Method 1

introducing a bonding foil, between the backing plate and the sputter target, wherein the bonding foil is an ignitable heterogeneous stratified structure for the propagation of an exothermic reaction; pressing the backing plate and the sputter target together and igniting the bonding foil, therebetween to melt and bond the solder layer

Methodology Applied

Scientific EffectExothermic reaction: Exothermic Reaction

Implementation Method 2

igniting the bonding foil, therebetween to melt and bond the solder layer on the backing plate with the solder layer on the sputter target

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS8993122B2Method for forming sputter target assemblies having a controlled solder thickness

Publication Date: 2015.03.31 PRAXAIR TECH INC

AI summary

The present invention relates to a method and apparatus of forming a sputter target assembly having a controlled solder thickness. In particular, the method includes the introduction of a bonding foil, between the backing plate and the sputter target, wherein the bonding foil is an ignitable heterogeneous stratified structure for the propagation of an exothermic reaction.