JPH10135772A - Surface acoustic wave device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small sized and inexpensive surface acoustic wave device. SOLUTION: After forming a surface acoustic wave devide pattern 2 consisting of IDT electrodes and bonding pads or the like is formed on a piezoelectric substrate 1, and an enclosing wail 3 is formed around a part where a surface acoustic wave is propagated except the bonding pads. After a cover 4 to cover an upper end of the enclosing wall 3 and an upper space of the part where the surface acoustic wave is propagated, a bump 5 is formed on the bonding pads to obtain the surface acoustic wave element. The bump 5 is pressed into contact with a conductive adhesives 6 on a chip carrier 7 so that the conductive adhesives 6 reaches the bonding pads and the surface acoustic wave element is connected electrically and fixed to the chip carrier 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface acoustic wave device used for communication equipment and the like and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a surface acoustic wave device has been housed in an expensive multilayer ceramic package and then mounted on a substrate.

In the field of semiconductors, as a method of mounting a chip such as an IC, as shown in FIG. 2, a plurality of bumps 12 are formed on a chip 11 and these bumps 12 are formed in order to make many dense connections simultaneously. The height is made uniform, and then the conductive adhesive 13 is applied to only the tips of the bumps 12 accurately so that they do not short-circuit each other, and mounted on the substrate 15, and the chip is fixed to the substrate 15 with the insulating adhesive 14. A so-called stud bump bond method is used.

Although this method is suitable for miniaturization, it has been necessary to control the accuracy in many steps, and this has caused a cost increase.

[0005]

In recent years, there has been an increasing demand for surface mounting of surface acoustic wave devices along with miniaturization of equipment. According to the conventional configuration, the surface acoustic wave device must be mounted using an expensive laminated ceramic package, and furthermore, there is a problem that it is difficult to reduce the size because a bonding area is required.

Accordingly, an object of the present invention is to provide an inexpensive and small surface acoustic wave device.

[0007]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the feature of a surface acoustic wave device that the number of connections is not as large as that of an IC and the connections are not dense.

In order to achieve the above object, a surface acoustic wave device according to the present invention comprises a chip carrier, and a surface acoustic wave element connected and fixed on the chip carrier via a conductive adhesive. The element includes a piezoelectric substrate, an IDT electrode provided on one surface of the piezoelectric substrate, and an IDT.
At least two bonding pads electrically connected to the T electrode, and metal bumps respectively provided on the two bonding pads, and the conductive adhesive is provided between the bonding pads and the chip carrier. Since the bonding pad and the chip carrier can be electrically connected with a conductive adhesive and the surface acoustic wave element can be fixed to the chip carrier, there is no need to use a ceramic package as in the conventional case, and it is not necessary to use an IC. In addition, since there is no need to fix with another insulating adhesive and the application amount of the conductive adhesive is not required to be as precise as that of an IC, the equipment cost and the number of steps are small, so that the apparatus is small and inexpensive.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a chip carrier, and a surface acoustic wave device fixedly connected to the chip carrier via a conductive adhesive.
The surface acoustic wave element includes a piezoelectric substrate, an IDT electrode provided on one surface of the piezoelectric substrate, and at least two bonding pads electrically connected to the IDT electrode.
It has a metal bump provided on each of these two bonding pads, and the conductive adhesive is a surface acoustic wave device provided between the bonding pad and the chip carrier. It is small and inexpensive without any.

According to a second aspect of the present invention, there is provided the surface acoustic wave device according to the first aspect, wherein the metal bump is formed of gold, and a stable electrical connection can be easily obtained.

According to a third aspect of the present invention, there is provided a surface acoustic wave device according to the first aspect, wherein an epoxy-based conductive adhesive is used as the conductive adhesive. There is no need to reinforce with an insulating adhesive.

According to a fourth aspect of the present invention, in the surface acoustic wave element, an enclosing wall is provided on the piezoelectric substrate so as to surround an IDT electrode and a portion where the surface acoustic wave propagates and to exclude a bonding pad portion. 2. The surface acoustic wave device according to claim 1, further comprising a cover provided to cover a space above the surrounding wall and a portion where the surface acoustic wave propagates, wherein the conductive adhesive reaches the IDT electrode. 3. And the occurrence of short-circuiting can be prevented.

According to a fifth aspect of the present invention, there is provided the surface acoustic wave device according to the first aspect of the present invention, wherein the height of the metal bump is substantially equal to the height of the lid. Can be sufficiently secured.

According to a sixth aspect of the present invention, an IDT electrode, at least two bonding pads electrically connected to the IDT electrode, and a metal on each of the two bonding pads are provided on one surface of the piezoelectric substrate. A step of forming a bump to obtain a surface acoustic wave element; a step of applying a conductive adhesive to a predetermined location of the chip carrier; and then applying the conductive bump of the chip carrier to the metal bump of the surface acoustic wave element. A step of bringing the conductive adhesive into direct contact with the bonding pad by contacting with the bonding pad, and then a step of curing the conductive adhesive. A small and inexpensive surface acoustic wave device that does not require the use of a ceramic package can be obtained.

An embodiment of the present invention will be described below with reference to FIG. (Embodiment 1) FIG. 1 is a sectional view of a surface acoustic wave device according to an embodiment of the present invention.

First, on a piezoelectric substrate 1 made of lithium niobate, lithium tantalate, quartz or the like, an elastic surface made of aluminum or an aluminum alloy, comprising an IDT electrode and at least two bonding pads electrically connected to the IDT electrode. A plurality of wave device patterns 2 are formed. Next, the surrounding wall 3 is formed of a film-shaped resist for each predetermined surface acoustic wave device pattern 2 except for a portion where the surface acoustic wave propagates on the piezoelectric substrate 1 and a portion of a bonding pad for extracting an electric signal is excluded. Formed. Next, a lid 4 that covers the upper end of the surrounding wall 3 and the space above the portion where the surface acoustic wave propagates is formed with a film-like resist.
The combined height of the surrounding wall 3 and the lid 4 is set to be substantially equal to the height of the bump. Then, usually 25 ~ 3 diameter
The bumps 5 are formed on the bonding pads by using a gold wire of 0 μm, and the piezoelectric substrate 1 is cut into chips of a desired size to obtain a surface acoustic wave device. In the present embodiment, the combined height of the surrounding wall 3 and the lid 4 is approximately 50 to
70 μm, and the height of the bump 5 is about 50 μm. The bumps 5 may be formed after the piezoelectric substrate 1 is divided into chips of a desired size. However, it is better to cut the bumps 5 after forming them in a wafer state, and to cut the conventional cut surface acoustic wave element using a ceramic. It is possible to reduce the number of processes compared to a process of wire bonding after die bonding to a package and curing.

Next, the bumps 5 of the surface acoustic wave element are applied to the conductive adhesive 6 provided on the chip carrier 7.
Are brought into contact with the bonding pads to electrically connect and fix the surface acoustic wave element to the chip carrier 7.

At this time, a method of applying an epoxy-based conductive adhesive 6 to a predetermined position of the chip carrier 7 with a dispenser or the like and pressing the bumps 5 of the surface acoustic wave element against the conductive adhesive 6 to heat and cure the same. The simplest is to electrically connect and fix the surface acoustic wave element and the chip carrier 7.

By doing so, the conventional wire bonding apparatus can be used for forming the bumps 5 and the conventional die bonder can be used for mounting the surface acoustic wave element on the chip carrier 7, so that new investment is minimized. In addition, a small surface acoustic wave device can be obtained at a much lower cost than the conventional stud bump bond method.

The chip carrier 7 is formed of alumina, glass epoxy resin or the like, and is usually rectangular in consideration of productivity.

In this embodiment, only the surface acoustic wave element is mounted on the chip carrier 7, but it is also possible to change the size of the chip carrier 7 and mount other components together.

[0022]

As described above, according to the present invention, since a ceramic package is not used, a surface acoustic wave device that is small and inexpensive as compared with the prior art can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a surface acoustic wave device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a general chip such as an IC using a stud bump bond method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Surface acoustic wave device pattern 3 Surrounding wall 4 Lid 5 Bump 6 Conductive adhesive 7 Chip carrier

Claims (6)

[Claims] 1. A chip carrier, comprising: a chip carrier; and a surface acoustic wave element connected and fixed to the chip carrier via a conductive adhesive. The surface acoustic wave element includes a piezoelectric substrate and one surface of the piezoelectric substrate. The IDT electrode provided above and the IDT
At least two bonding pads electrically connected to the electrodes and metal bumps respectively provided on the two bonding pads, and the conductive adhesive is provided between the bonding pads and the chip carrier. Surface acoustic wave device. 2. The surface acoustic wave device according to claim 1, wherein the metal bump is formed of gold. 3. The surface acoustic wave device according to claim 1, wherein the conductive adhesive is an epoxy-based conductive adhesive. 4. In a surface acoustic wave element, an enclosing wall provided on a piezoelectric substrate so as to surround an IDT electrode and a surface acoustic wave propagating portion and excluding a bonding pad portion, and the enclosing wall and the elastic surface A cover provided so as to cover a space above a portion where the wave propagates.
A surface acoustic wave device according to claim 1. 5. The surface acoustic wave device according to claim 1, wherein the height of the metal bump is substantially equal to the height of the lid. 6. An IDT electrode, at least two bonding pads electrically connected to the IDT electrode on one surface of the piezoelectric substrate, and a metal bump formed on each of the two bonding pads to form a surface acoustic wave. Obtaining a device, and then applying a conductive adhesive to a predetermined location of the chip carrier, and then contacting the metal bump of the surface acoustic wave device with the conductive adhesive of the chip carrier to form the conductive adhesive. A method for manufacturing a surface acoustic wave device, comprising: a step of bringing a conductive adhesive into direct contact with the bonding pad; and a step of curing the conductive adhesive.