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Researchers Submit Patent Application, "Production Method for Electronic Component and Pressure-Sensitive Adhesive Sheet to Be Used in the Production...

March 5, 2014



Researchers Submit Patent Application, "Production Method for Electronic Component and Pressure-Sensitive Adhesive Sheet to Be Used in the Production Method", for Approval

By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Hirayama, Takamasa (Ibaraki-shi, JP); Shimokawa, Daisuke (Ibaraki-shi, JP), filed on July 6, 2012, was made available online on February 20, 2014.

The patent's assignee is Nitto Denko Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "In production of a semiconductor chip, a package system called a wafer level chip size package (WL-CSP) in which packaging is performed in a wafer state for the purpose of high-density packaging is drawing attention. According to the WL-CSP, a wafer is subjected to dicing after redistribution, formation of terminals, and the like are performed on the wafer, and hence a semiconductor package reduced in size almost to a chip size can be obtained.

"In this connection, a plurality of circuit patterns formed on one wafer may include defective products. In this case, when processes such as redistribution are performed on the wafer in a collective manner without discriminating defective products from non-defective products, a process performed with respect to the defective products becomes waste, resulting in an increase in production cost of the non-defective products which can be shipped. In order to solve the problem, there has been proposed a production method involving performing formation of terminals and the like after only non-defective products are selected (Patent Literature 1).

"Further, the WL-CSP requires many complicated processing steps. For example, the step of forming a redistribution layer generally includes some steps such as first interlayer insulating layer formation, seed metal deposition, photoresist pattern formation, plating, photoresist removal, and seed metal etching, and second interlayer insulating layer formation. Therefore, in the WL-CSP, there is a strong demand for simplification of the steps as well as a reduction in production cost. More specifically, according to a production method for a CSP, a dielectric protective layer is provided on a pattern surface and bumps are formed thereon. However, a thickness of a semiconductor chip is becoming small, and hence with only a thickness of such dielectric protective layer, it is highly probable that the semiconductor chip may be broken. Further, the semiconductor chip is often used in a severe environment, which makes it difficult to ensure reliability. Thus, there is a demand for increasing the thickness of the dielectric protective layer. However, in a conventional production method, which involves applying a liquid resin as a dielectric protective layer onto a pattern surface of a semiconductor chip through use of spin coating, there are problems in that it is difficult to increase a thickness of the dielectric protective layer, and that the use of the spin coating results in a reduction in coating yield of the dielectric protective layer and an increase in use amount of the resin."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Technical Problem

"The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to reduce a production cost of a chip-shaped electronic component such as a semiconductor chip and simplify a production method therefor.

"Means for Solving the Problem

"The present invention provides a production method for an electronic component. The production method includes:

"attaching a pressure-sensitive adhesive sheet to a substrate, the pressure-sensitive adhesive sheet including a base, a thermally expandable pressure-sensitive adhesive layer containing thermally expandable microspheres provided on one surface of the base, and a dielectric layer including a weak pressure-sensitive adhesive layer and an adhesive layer provided on another surface of the base in this order from a side of the base, so that the thermally expandable pressure-sensitive adhesive layer is placed on a side of the substrate;

"attaching and fixing a plurality of chip-shaped electronic components to a surface of the pressure-sensitive adhesive sheet on a side of the adhesive layer so that electrode surfaces of the plurality of chip-shaped electronic components are placed on the side of the adhesive layer;

"covering an entire surface of the plurality of chip-shaped electronic components excluding fixed surfaces with a protective substance to obtain an encapsulated body including the plurality of chip-shaped electronic components;

"subjecting the pressure-sensitive adhesive sheet to heating treatment to cause the thermally expandable microspheres in the thermally expandable pressure-sensitive adhesive layer to expand to decrease an adhesion of the thermally expandable pressure-sensitive adhesive layer and peeling the thermally expandable pressure-sensitive adhesive layer from the substrate;

"peeling the weak pressure-sensitive adhesive layer from the adhesive layer to obtain a laminate of the adhesive layer and the encapsulated body; and

"cutting the laminate between the plurality of chip-shaped electronic components to separate individual chip-shaped electronic components.

"In a preferred embodiment, the protective substance contains a thermosetting resin or a thermoplastic resin, and a heating temperature in the heating treatment is equal to or higher than a curing temperature of the thermosetting resin or is equal to or lower than a softening temperature of the thermoplastic resin.

"According to another aspect of the present invention, a pressure-sensitive adhesive sheet to be used in the production method for an electronic component is provided. The pressure-sensitive adhesive sheet includes:

"a base;

"a thermally expandable pressure-sensitive adhesive layer containing thermally expandable microspheres provided on one surface of the base; and

"a dielectric layer including a weak pressure-sensitive adhesive layer and an adhesive layer provided on another surface of the base in this order from a side of the base.

"In a preferred embodiment, a dielectric constant of the adhesive layer is 5 or less.

"In a preferred embodiment, a water absorption rate of the adhesive layer is 2% or less.

"In a preferred embodiment, an adhesion of the weak pressure-sensitive adhesive layer with respect to the adhesive layer in an atmosphere of 23.degree. C. is 3 N/20 mm or less.

"In a preferred embodiment, the adhesion of the weak pressure-sensitive adhesive layer with respect to the adhesive layer in an atmosphere of 100.degree. C. is 2 N/20 mm or less.

"In a preferred embodiment, the protective substance contains a thermosetting resin, and an expansion starting temperature of the thermally expandable microspheres is equal to or higher than a curing temperature of the thermosetting resin.

"Advantageous Effects of Invention

"According to the present invention, through use of a pressure-sensitive adhesive sheet having a predetermined configuration, a dielectric protective layer can be formed easily on an electrode surface of a chip-shaped electronic component. The dielectric protective layer can serve as an insulating layer in formation of the above-mentioned redistribution layer, which leads to simplification of the step of forming a redistribution layer in a production method for a chip-shaped electronic component. Further, in the present invention, a further process with respect to a defective product can be avoided by selecting only a non-defective product as a chip-shaped electronic component and covering the non-defective product with a protective substance to obtain an encapsulated body. Further, the encapsulated body can be peeled from a substrate without being damaged by decreasing the adhesion of a thermally expandable pressure-sensitive adhesive layer sufficiently by heating treatment. Consequently, a yield is enhanced, and hence a production cost can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

"FIG. 1 A schematic cross-sectional view of a pressure-sensitive adhesive sheet of the present invention.

"FIG. 2 A schematic view illustrating a production method of the present invention."

For additional information on this patent application, see: Hirayama, Takamasa; Shimokawa, Daisuke. Production Method for Electronic Component and Pressure-Sensitive Adhesive Sheet to Be Used in the Production Method. Filed July 6, 2012 and posted February 20, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2655&p=54&f=G&l=50&d=PG01&S1=20140213.PD.&OS=PD/20140213&RS=PD/20140213

Keywords for this news article include: Treatment, Semiconductor, Electronic Components, Nitto Denko Corporation.

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Source: Electronics Newsweekly


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