Thermosetting encapsulation adhesive sheet

Abstract

A thermosetting encapsulation adhesive sheet which is used for encapsulating a chip type device (1) having connection electrodes (bumps) (3) and mounted on a wiring circuit board (2). The thermosetting encapsulation adhesive sheet is composed of an epoxy resin composition having a viscosity of 5×104 to 5×106 Pa·s as measured at a temperature of 80 to 120° C. before thermosetting thereof. The thermosetting encapsulation adhesive sheet makes it possible to conveniently encapsulate a hollow device with an improved yield.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a thermosetting adhesive sheet to be employed for encapsulating a chip type device and, more specifically, to a thermosetting adhesive sheet to be employed for encapsulating a so-called hollow device, such as a surface acoustic wave device (SAW device), a quartz device, a high frequency device or an acceleration sensor, which is required to have a hollow surface.[0003]2. Description of the Related Art[0004]Conventionally, encapsulation of a chip type device such as a semiconductor element or an electronic component is achieved by a transfer molding method employing a powdery epoxy resin composition, or a potting method, a dispensing method or a printing method employing a liquid epoxy resin composition, a silicone resin or the like. These encapsulation methods require an expensive molding machine, and suffer from a problem such that the encapsulation resin adheres to unwanted portions of...

AI Technical Summary

Benefits of technology

[0009]To achieve the aforementioned object, the inventors of the present invention conducted studies on the physical properties of a thermosetting adhesive sheet to be employed as an encapsulation material. The inventors further conducted intensive studies on the viscosity of the sheet at an encapsulation temperature before the thermosetting. As a result, the inventors found that, if a sheet having a viscosity in the aforementioned specific viscosity range at a temperature of 80° C. to 120° C. before the thermosetting is employed as the thermosetting adhesive sheet, the intrusion of the resin into below the chip type device is suppressed when the chip type device on the substrate is encapsulated with the thermosetting adhesive sheet having such a proper viscosity, and thus the present invention is attained.

[0010]As described above, the inventive thermosetting encapsulation adhesive sheet to be used for encapsulating the chip type device mounted on the substrate comprises the epoxy resin composition having a viscosity of 5×104 to 5×106 Pa·s as measured at a temperature of 80° C. to 120° C. before the thermosetting thereof. Therefore, the intrusion of the resin into below the chip type device is suppressed during the encapsulation of the chip type device mounted on the substrate, so that a hollow space can be kept defined between the substrate and the chip type device. Thus, the resin encapsulation can be conveniently achieved with an improved yield with the use of a thermosetting encapsulation adhesive sheet.

[0011]The epoxy resin composition preferably comprises the following components (A) to (E): (A) an epoxy resin; (B) a phenol resin; (C) an elastomer; (D) an inorganic filler; and (E) a curing accelerating agent. In this case, the thermosetting encapsulation adhesive sheet can be easily provided which has a viscosity controlled at a predetermined level under the aforementioned conditions.

[0012]Where the inorganic filler (D) is present in the epoxy resin composition in a proportion of 60 to 80% by weight based on the weight of the epoxy resin composition, the thermosetting encapsulation adhesive sheet can be more easily provided which has a viscosity controlled at a predetermined level under the aforementioned conditions.

[0013]Where the curing accelerating agent (E) is a quaternary phosphonium salt compound, the thermosetting encapsulation adhesive sheet can be easily provided which has a viscosity controlled at a predetermined level under the aforementioned conditions and is excellent in storage stability at ordinary temperatures.

Problems solved by technology

These encapsulation methods require an expensive molding machine, and suffer from a problem such that the encapsulation resin adheres to unwanted portions of the device.

Therefore, a less expensive and more convenient encapsulation method is demanded.

Particularly, where the conventional dispensing method employing a liquid encapsulation material is employed for the encapsulation of a device required to have a hollow surface, it is difficult to suppress intrusion of the encapsulation material into an active surface below the device.

Even with this method, complete rheological control of the liquid encapsulation material is difficult.

This may reduce the yield, and prevent the size reduction and the cost reduction of the device.

Thus, the conventional control of the resin encapsulation of the hollow device is not satisfactory.

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