Polyurethane Microsphere Adhesives for Clean Wafer De-Bonding
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Solution Overview
Problem
Current adhesives for wafer cutting and de-bonding processes face challenges in efficiently releasing from surfaces in hot water without leaving residue, with existing solutions either having high wafer damage rates or odor concerns, and lacking the use of thermally expandable microspheres which can control de-bonding temperature and time effectively.
Innovation Solution
Development of de-bondable polyurethane adhesives based on thermally expandable microspheres, formed by reacting di- or polyisocyanates, polyols, catalysts, and thermally expandable microspheres, with an isocyanate index between 28 to 65, allowing for efficient and clean de-bonding in hot water by expanding the microspheres upon heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy adhesive is used to provide strong bonding to Si ingot, then bonding strength is improved, but wafer damage rate increases due to high product hardness and brittleness
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive system by using polyurethane instead of epoxy, and controls the isocyanate index within 28-65 to achieve optimal balance between bonding strength and flexibility. This parameter optimization reduces brittleness while maintaining adhesion strength, thereby lowering wafer damage rates during cutting operations.
Solution Approach 2:
The invention creates a composite adhesive system by incorporating thermally expandable microspheres (5-50 wt%) into the polyurethane adhesive matrix. This composite structure combines the strong bonding capability of polyurethane with the thermal expansion properties of microspheres, providing both mechanical strength and controlled de-bonding behavior to prevent wafer damage.
2Productivity
If adhesive is designed to release in hot water, then de-bonding efficiency is improved, but adhesion stability at operating temperature deteriorates
Solution Approach 1:
The patent utilizes the phase transition of thermally expandable microspheres at specific temperatures. These microspheres remain stable and provide strong adhesion at operating temperatures (up to 80°C), then undergo rapid expansion when exposed to hot water (90-100°C), causing controlled adhesive failure and enabling efficient de-bonding. The phase transition temperature of the microspheres is carefully selected to distinguish between operating and de-bonding conditions.
Solution Approach 2:
The invention exploits thermal expansion of the microspheres embedded in the adhesive. At normal operating temperatures, the microspheres maintain adhesive integrity. When exposed to hot water, the microspheres expand rapidly, generating internal stress that causes the adhesive to fail and release from the bonded surfaces, achieving efficient de-bonding while maintaining stability during operation.
3Speed
If expandable microspheres are added to adhesive, then de-bonding speed is improved, but adhesive formulation complexity increases
Solution Approach 1:
The patent uses thermally expandable microspheres as a disposable functional component within the adhesive. These microspheres are inexpensive, commercially available materials that perform their expansion function once during de-bonding. Their simple addition to the adhesive formulation provides rapid de-bonding capability without requiring complex processing or additional equipment, making the complexity increase acceptable given the significant productivity improvement.
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 adhesives achieve efficient and clean de-bonding in hot water with minimal residue and controlled de-bonding time, improving wafer cutting processes and mechanical property testing by ensuring strong adhesion and rapid release without wafer damage or odor issues.
Implementation Method 1
Such an adhesive can have significant thermal expansion when the materials are heated above the 'starting temperature' of the microspheres, thus leading to a fast and clean de-bonding from bonded surfaces.
Implementation Method 2
de-bondable polyurethane adhesives based on thermally expandable microspheres, obtainable or obtained by the reaction of the components of (A) at least one di- or polyisocyanate, (B) at least one polyol
Data Source
AI summary
Disclosed herein are de-bondable polyurethane adhesives based on thermally expandable microspheres, obtainable or obtained by the reaction of the components of (A) at least one di- or polyisocyanate, (B) at least one polyol, (C) catalyst, (D) thermally expandable microspheres, and (E) other additives, wherein the isocyanate index of the reaction is set in the range of from 28 to 65. Additionally disclosed herein is a method of using the de-bondable polyurethane adhesives for de-bonding metal and cutting pad during wafer cutting. Further disclosed herein is a method of using the de-bondable polyurethane adhesives in mechanical property testing sample preparation.