Wafer Protection Adhesive Sheet Resolving Stability
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Solution Overview
Problem
The existing pressure sensitive adhesive sheets for wafer protection suffer from instability over time, leading to insufficient interfacial adhesion between the intermediate and adhesive layers after radiation irradiation, resulting in poor followability to uneven wafer surfaces and potential residue deposition during peeling.
Innovation Solution
A pressure sensitive adhesive sheet comprising a base material, an intermediate layer formed from a composition of non-energy ray-curable and energy ray-curable acrylic polymers in specific proportions, and a pressure sensitive adhesive layer, ensuring improved interfacial adhesion and stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a radiation curable oligomer as a low-molecular component is contained in the intermediate layer to improve the modulus of elasticity after radiation irradiation, then the followability to unevenness is improved, but the adhesive strength becomes unstable after long-term storage and the pressure sensitive adhesive layer is excessively cured
Solution Approach 1:
The patent changes the molecular weight parameter of the radiation curable component from low-molecular (oligomer) to high-molecular (polymer with mass average molecular weight of 100,000 to 1,000,000). This parameter change maintains the ability to improve modulus of elasticity and followability while preventing excessive curing and adhesive strength instability during long-term storage.
Solution Approach 2:
The patent creates a composite intermediate layer containing both a non-radiation curable polymer (mass average molecular weight: 1,000,000 to 5,000,000) and a radiation curable polymer (mass average molecular weight: 100,000 to 1,000,000). This composite structure combines the stability of the non-curable polymer with the curability and modulus improvement of the radiation curable polymer, achieving both followability and long-term stability.
2Duration of action of stationary object
If the pressure sensitive adhesive sheet is stored for a long period of time, then the radiation curable oligomer transfers to the pressure sensitive adhesive layer, but this causes excessive curing and insufficient interfacial adhesion
Solution Approach 1:
The patent changes the molecular weight parameter of the radiation curable component from low-molecular (oligomer) to high-molecular (polymer with mass average molecular weight of 100,000 to 1,000,000). High-molecular-weight polymers have lower mobility and reduced tendency to migrate or transfer between layers during storage, thereby preventing excessive curing and maintaining stable interfacial adhesion even after long-term storage.
Solution Approach 2:
The patent creates a composite intermediate layer containing both a non-radiation curable polymer (mass average molecular weight: 1,000,000 to 5,000,000) and a radiation curable polymer (mass average molecular weight: 100,000 to 1,000,000). This composite structure provides long-term stability by combining the migration resistance of high-molecular-weight polymers with controlled radiation curability, preventing transfer to the adhesive layer during storage.
3Reliability
If a pressure sensitive adhesive sheet with insufficient followability to unevenness is used, then the adhesion between the pressure sensitive adhesive layer and the wafer surface is insufficient, but this leads to peeling, infiltration of polishing waste, and damage
Solution Approach 1:
The patent changes the molecular weight and curability parameters of the intermediate layer material to achieve optimal balance between followability and adhesion. The radiation curable polymer with mass average molecular weight of 100,000 to 1,000,000 provides sufficient flexibility for followability while maintaining adequate adhesion strength, preventing peeling and infiltration during polishing processes.
Solution Approach 2:
The patent creates a composite intermediate layer containing both a non-radiation curable polymer (mass average molecular weight: 1,000,000 to 5,000,000) and a radiation curable polymer (mass average molecular weight: 100,000 to 1,000,000). This composite structure provides excellent followability to uneven wafer surfaces while maintaining strong adhesion, preventing peeling, infiltration of polishing waste, and wafer damage during processing.
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 solution provides excellent interfacial adhesion, prevents residue deposition, and maintains adhesive strength stability even after long-term storage, ensuring effective wafer protection during polishing and grinding processes.
Implementation Method 1
an intermediate layer, and a pressure sensitive adhesive layer in this order, wherein the intermediate layer is a layer formed from an intermediate layer-forming composition containing 100 parts by mass of a non-energy ray-curable acrylic polymer (A) and 25 parts by mass or more of an energy ray-curable acrylic polymer (B) having a mass average molecular weight of 50,000 to 250,000
Data Source
AI summary
There is provided a pressure sensitive adhesive sheet for wafer protection (1a) comprising a base material (11), an intermediate layer (12), and a pressure sensitive adhesive layer (13) in this order, wherein the intermediate layer is a layer formed from an intermediate layer-forming composition containing 100 parts by mass of a non-energy ray-curable acrylic polymer (A) and 25 parts by mass or more of an energy ray-curable acrylic polymer (B) having a mass average molecular weight of 50,000 to 250,000; and the pressure sensitive adhesive layer is a layer formed from a pressure sensitive adhesive composition containing an energy ray-curable acrylic polymer (C). The inventive pressure sensitive adhesive sheet for wafer protection is excellent in interfacial adhesion between an intermediate layer and a pressure sensitive adhesive layer after energy ray irradiation. Therefore, the pressure sensitive adhesive sheet for wafer protection can suppress the deposition of a residue of the pressure sensitive adhesive layer to an adherend when it is removed after laminated to the adherend, has excellent followability even to an adherend having a large unevenness difference on a wafer surface, and has a small rate of change of adhesive strength even after being stored for a long period of time and has excellent stability with time.