Back Grinding Adhesive Sheet for Protecting Wafer Protrusions
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Solution Overview
Problem
Existing adhesive sheets for back grinding of semiconductor wafers fail to properly protect convex portions during the process, leading to potential damage due to excessive load applied during back grinding.
Innovation Solution
An adhesive sheet with a non-adhesive cushion layer and an adhesive layer having an opening, where the convex portions of the semiconductor wafer are placed in the opening, ensuring protection by the cushion layer. The cushion layer is designed to have specific tensile stress and is composed of a thermoplastic resin with controlled melt flow rate and melting point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive sheets with thicker adhesive or flexible resin layer are used to achieve followability, then adhesion to uneven surfaces is improved, but risk of adhesive residue and insufficient followability on rough surfaces increases
Solution Approach 1:
The adhesive sheet is divided into a base film and a separate cushion layer with specific elastic modulus, creating distinct functional zones that address both adhesion and followability requirements without causing adhesive residue
Solution Approach 2:
The cushion layer's elastic modulus is specifically controlled (0.01 to 0.1 MPa) to optimize the balance between followability for bump protection and prevention of adhesive residue, representing a precise parameter adjustment to resolve the contradiction
2Device complexity
If only tips of protruding electrodes are in contact with the base sheet during back grinding, then the adhesive sheet structure is simplified, but damage to protruding electrodes due to excessive load increases
Solution Approach 1:
The cushion layer is positioned beforehand to contact and protect the protruding electrodes (bumps) before the back grinding process begins, distributing the load during grinding to prevent electrode damage while maintaining a relatively simple adhesive sheet structure
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 effectively protects the convex portions of the semiconductor wafer during back grinding, preventing damage by distributing the load and ensuring proper followability and adhesion properties.
Implementation Method 1
tensile stress of the cushion layer punched out by using a dumbbell according to JIS Z 1702 is 2 to 30 N/10 mm when the punched-out cushion layer is stretched by 25%
Implementation Method 2
the cushion layer is composed of a thermoplastic resin with a melt flow rate (JIS K 7210, 125° C./10.0 kg load) of 0.2 to 30 g/10 min and a melting point of 60 to 110° C.
Data Source
AI summary
Provided is a back grinding adhesive sheet which can adequately protect protrusions provided to a semiconductor wafer, and with which back grinding can be adequately performed. The present invention provides a back grinding adhesive sheet for a semiconductor wafer having protrusions, the back grinding adhesive sheet comprising a non-adhesive cushion layer, and an adhesive layer provided on the cushion layer. The adhesive layer has an opening with a smaller diameter than the diameter of the semiconductor wafer, and the outer edge of the semiconductor wafer is adhered to the adhesive layer such that the protrusions on the semiconductor wafer are positioned inside the opening. The protrusions are protected by the cushion layer when the semiconductor wafer is in the state of being adhered to the adhesive layer. The adhesive sheet satisfies at least one of the following conditions (1)-(2). (1) When the cushion layer is cut out using the dumbbell from JISZ1702 and is stretched 25% at a gauge length of 40 mm and a tensile speed of 300 mm/min, the tensile stress is 2-30N/10 mm. (2) The cushion layer is formed from a thermoplastic resin that has a melt flow rate (JISK7210, 125° C./10.0 kg load) of 0.2-30 g/10 min, and a melting point of 60-110° C.