Foaming Adhesive Sheet for Backgrinding Hard Brittle Substrates
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Solution Overview
Problem
The existing methods for grinding hard and brittle substrates, such as sapphire or silicon carbide, face challenges with high frictional resistance, reduced pressure-sensitive adhesive strength due to frictional heat, and contamination issues from adhesive residues.
Innovation Solution
A pressure-sensitive adhesive sheet with a pressure-sensitive adhesive layer containing a base polymer, such as a thermoplastic elastomer, and a foaming agent with a foaming temperature of 90° C. or more, ensuring a shear adhesive strength of 1.0 MPa or more at 25° C. and 0.2 MPa or more at 80° C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pressure-sensitive adhesive sheet is used to fix the hard and brittle substrate during high-load grinding, then productivity and contamination property are improved, but the pressure-sensitive adhesive strength is reduced due to frictional heat, resulting in insufficient fixing
Solution Approach 1:
The patent changes the physical and chemical parameters of the pressure-sensitive adhesive by incorporating a foaming agent that activates at high temperature. The adhesive transitions from a dense state at room temperature to a foamed state during heating, altering its mechanical properties to maintain adhesive strength under frictional heat conditions while preserving fixing capability during grinding.
Solution Approach 2:
The foaming agent undergoes a phase transition from solid to gas when heated during the grinding process. This phase transition creates foam within the adhesive layer, which helps dissipate frictional heat and maintains the adhesive's fixing property despite the high-temperature conditions generated during high-load grinding of hard and brittle substrates.
2Reliability
If a pressure-sensitive adhesive sheet with strong adhesive property under high temperature is used, then fixing property is improved, but peel strength increases and adhesive residue occurs, requiring cleaning of the substrate
Solution Approach 1:
The patent utilizes parameter changes by selecting a foaming agent with a specific activation temperature range. During grinding, the adhesive remains in a non-foamed state with strong adhesive properties. After grinding, when heated to the foaming temperature, the adhesive foams and its properties change, enabling easy peeling without residue. This parameter change resolves the contradiction between strong fixing during grinding and easy removal afterward.
3Reliability
If wax is used as a fixing material for grinding hard and brittle substrate, then fixing property is improved, but cleaning step with large amount of solvent is required, worsening contamination property and productivity
Solution Approach 1:
The patent employs a disposable pressure-sensitive adhesive sheet that performs the fixing function during grinding and then is easily removed without requiring solvent cleaning. The adhesive sheet is designed to be used once and discarded, eliminating the need for time-consuming cleaning steps with solvents, thereby improving productivity while maintaining effective fixing during the grinding process.
Solution Approach 2:
The patent replaces the traditional wax-based mechanical fixing system with a pressure-sensitive adhesive system. This substitution eliminates the need for solvent-based cleaning processes, as the adhesive sheet can be easily peeled off without residue, thereby improving both contamination property and productivity while maintaining fixing effectiveness.
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 pressure-sensitive adhesive sheet provides excellent grinding accuracy, low contamination, high productivity, and effective fixing properties for hard and brittle substrates during the backgrinding process, while allowing easy peeling after grinding without the need for solvent cleaning.
Implementation Method 1
a foaming agent having a foaming temperature of 90° C. or more
Implementation Method 2
extremely large frictional resistance occurs between the body to be ground (hard and brittle substrate) and the grinder, resulting in a reduction in pressure-sensitive adhesive strength of the pressure-sensitive adhesive sheet due to frictional heat
Data Source
AI summary
Provided is a pressure-sensitive adhesive sheet that may be used for the grinding of a hard and brittle substrate in a backgrinding step for the hard and brittle substrate, the pressure-sensitive adhesive sheet being excellent in all of grinding accuracy, low contamination property, productivity, and fixing property. The pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains: a pressure-sensitive adhesive containing a base polymer; and a foaming agent having a foaming temperature of 90° C. or more, and wherein the pressure-sensitive adhesive sheet has, when a pressure-sensitive adhesive surface thereof is bonded to a silicon chip, a shear adhesive strength of 1.0 MPa or more under an ambient temperature of 25° C., and a shear adhesive strength of 0.2 MPa or more under an ambient temperature of 80° C.