JP2001251161A - Surface acoustic wave device and method for manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive surface acoustic wave device in which flip chip bonding can easily be performed even in a surface acoustic wave element provided with sound absorbing material and which does not have such problems as cracking and chipping, and to provide its manufacturing method. SOLUTION: In a surface acoustic wave element 1, a surface on the side of a transducer 2 is arranged so as to face the surface of a base substrate 6 where a wiring pattern is formed, and the element 1 is covered with a cap member 9 and the base substrate 6 and sealed. The sound absorbing material 11 of the element 1 covers the entire rear surface of the element 1, the edge parts of the material 11 extend around the side faces of the element 1 and also function as cushioning material. The sound absorbing material 11 is formed on the rear surface of the element 1 after the element 1 is subjected to flip chip bonding to the substrate 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used for, for example, a television, and more particularly to a surface acoustic wave device having a sound absorbing material for absorbing surface acoustic waves and an internal connection structure thereof.

[0002]

2. Description of the Related Art A method of connecting a transducer surface of a surface acoustic wave element to a circuit board having a wiring pattern opposed thereto by flip-chip bonding has been known in order to reduce the size and surface mounting of a surface acoustic wave device. I have. The flip chip connection method is a method in which terminals provided on the element surface and terminals provided on the substrate are directly joined to each other without using wires.
In general, ceramic is used as a substrate material connected to the surface acoustic wave element, and a metal pattern such as tungsten is formed on the surface of the substrate.

For example, in a surface acoustic wave device used for a specific application such as a television, a sound absorbing material is formed on a transducer surface of a surface acoustic wave element and / or a back surface of the element in order to absorb unnecessary surface acoustic waves. . However, when a sound absorbing material is provided on the surface of the surface acoustic wave element on the side facing the substrate, when flip-chip connection is performed, the thickness of the sound absorbing material fluctuates and it is difficult to connect both terminals. Alternatively, a sufficient connection weight may not be applied. For this reason, a part of the substrate surface facing the sound absorbing material must be cut off or a concave portion must be provided. As described above, a hard material such as a ceramic is used as a material of the substrate, so that processing is troublesome.

[0004] By performing these processes,
There is a disadvantage that the manufacturing cost of the surface acoustic wave device increases. Furthermore, when a sound absorbing material is formed on the back surface opposite to the transducer surface, the transducer surface is opposed to the base substrate, and the surface acoustic wave element is pressed against the base substrate for flip-chip connection, the surface acoustic wave is applied to the base substrate. It was difficult to connect the elements in parallel.

In order to avoid these problems, if the application area of the sound absorbing material is reduced, the effect of the sound absorbing material is weakened, or the end of the surface acoustic wave element hits the inside of the cap member, causing chipping or cracking. In some cases, there is a problem with the yield.

[0006]

As described above, the sound absorbing material is formed on the back surface of the surface acoustic wave element, the surface acoustic wave element is connected in parallel to the base substrate, and the surface acoustic wave element is not damaged. Is difficult to seal with a base substrate and a cap member.

The present invention solves the above-mentioned problems, and even if the surface acoustic wave element is provided with a sound absorbing material, it can be easily flip-chip connected and has a low cost with few problems such as cracks and chips. An object of the present invention is to provide a surface acoustic wave device and a method of manufacturing the same.

[0008]

A surface acoustic wave device according to the present invention comprises a transducer, a wiring pattern connected to the transducer, a pad portion provided on a part of the wiring pattern, and a bump formed on the pad portion. A surface acoustic wave element in which a first sound absorbing material for absorbing surface acoustic waves is formed on one surface, and a second sound absorbing material for absorbing surface acoustic waves is formed on the other surface on the opposite side; A base substrate provided with a terminal for connection to the outside on one surface, and a wiring pattern connected to the terminal on the other surface, provided on the base substrate;
A cap member having a concave portion larger than the thickness of the surface acoustic wave element, a connection member for electrically and mechanically connecting the surface acoustic wave element and the base substrate, and mechanically connecting the cap member and the base substrate. A sealing member for sealing the surface acoustic wave element, wherein a surface of the surface acoustic wave element on the transducer side is arranged to face the other surface of the base substrate on which the wiring pattern is formed. The second sound absorbing material is provided so as to extend to the one surface and the side surface of the surface acoustic wave element.

Further, in the method of manufacturing a surface acoustic wave device according to the present invention, in order to form a plurality of surface acoustic wave elements on one surface of a wafer serving as a surface acoustic wave element, a plurality of transducers and a wiring pattern connected thereto are formed. Forming a pad portion on a part of the wiring pattern; forming a first sound absorbing material for absorbing surface acoustic waves on one surface of the wafer; and forming a pad portion on one surface of the wafer. Forming a connection bump on the pad portion provided;
Dividing a wafer on which a plurality of surface acoustic wave elements are formed into individual surface acoustic wave elements; and providing a terminal for connecting to the outside on one surface of the base substrate and a wiring pattern for connecting to these terminals on the other surface. Providing a conductive adhesive on a part of a wiring pattern provided on the other surface of the base substrate; and providing wiring between the surface of the surface acoustic wave element on which the transducer is formed and the base substrate. The surfaces on which the patterns are formed face each other, the conductive adhesive area of the base substrate is connected to the bumps of the surface acoustic wave element, and a gap is formed between the base substrate and the transducer of the surface acoustic wave element. A step of flip-chip connecting the surface acoustic wave element to the base substrate while producing the surface acoustic wave element; a surface of the surface acoustic wave element opposite to a transducer forming surface; Forming a second sound absorbing material for absorbing surface acoustic waves over a side surface of the element, and mechanically connecting the cap member to the base substrate with a sealing member; Is hermetically sealed.

The sound absorbing material on the back surface of the surface acoustic wave element covers the entire back surface of the element, and the end of the sound absorbing material has a shape larger than the area of the element and goes around the end of the element. The cap member does not directly contact the portion. For this reason, cracks, chips,
Cracks can be prevented.

In this case, the back sound absorbing material has a role of a cushioning material. Such a shape of the back surface sound absorbing material can be realized by flip-chip connecting the surface acoustic wave element to the base substrate and then applying or potting the back surface sound absorbing material.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a surface acoustic wave device according to an embodiment of the present invention. A transducer 2 is formed on the chip surface of the surface acoustic wave element 1, and a wiring pattern 3 and a sound absorbing material 4 are formed on this surface. The thickness of the sound absorbing material 4 is smaller than the distance between the surface acoustic wave element 1 and the base substrate 6.

The wiring pattern 3 is connected to a base substrate 6 via a connection portion 5. A plurality of terminals 7 are arranged at an end of the base substrate 6. The surface acoustic wave element 1 is flip-chip connected to the base substrate 6 so that the transducer section 2 faces the wiring pattern on the substrate surface of the base substrate 6. This surface acoustic wave device 1
Is enclosed and sealed with the substrate 6 by the cap material 9 and the sealing material 8.

A sound absorbing material 11 is formed on a surface of the surface acoustic wave element 1 different from the surface on which the transducer section is provided. The material of the sound absorbing material 11 may be the same as the sound absorbing material 4 or may be different as required. The sound absorbing material 11 prevents the surface acoustic wave generated by the transducer 2 from being reflected on the back surface (the top surface in FIG. 1) of the surface acoustic wave element 1.

FIG. 2A is a plan view of the base substrate 6 and FIG.
(B) is a bottom view and a side view. As shown in FIG. 2A, a wiring pattern including the connection portion 5 is formed on the front surface of the base substrate 6, and terminals 7a are formed on the back surface as shown in FIG. 2B. The terminal 7a and the wiring pattern are connected by a through-hole plating 7b. The terminal 7a is connected to a pad on a circuit board (not shown) to which the surface acoustic wave device is applied. In FIG. 1, for convenience of explanation, the two terminals 7 face each other in the same direction as the left and right sound absorbing members 3, but actually, the positions 4 as indicated by the dotted lines in FIG.
a.

The thickness of the sound absorbing material 4 formed on the surface of the surface acoustic wave element 1 on which the transducer 2 is provided is about 40 μm when formed by a normal screen printing method. By making the sound absorbing material portion of the surface acoustic wave element face the other, both the sound absorbing material and the substrate are maintained without contact.

Next, the manufacturing method and structure of the surface acoustic wave device according to the present invention will be described in detail with reference to FIGS. FIG.
FIG. 4 is a flowchart showing a method of manufacturing the surface acoustic wave device according to the present invention, and FIG. 4 is an enlarged sectional view showing the structure of an end portion of the surface acoustic wave device 1 of FIG.

First, in order to form a plurality of surface acoustic wave elements on one surface of a wafer (not shown) serving as a surface acoustic wave element, one of a plurality of transducers 2 and a wiring pattern connected thereto and a wiring pattern are formed. Pad part 5a
Is formed (step S1).

Next, a sound absorbing material 4 for absorbing surface acoustic waves is formed on one surface of the wafer on which the transducer 2 of the surface acoustic wave element is formed (step S2), and a connection member is formed on the pad portion 5a. Is formed (step S3). In step S4, the wafer on which the plurality of surface acoustic wave devices are formed is divided into individual surface acoustic wave devices 1.

As for the base substrate, first, as shown in step S5, a terminal 7 connected to the outside is connected to one surface of the base substrate.
And a wiring pattern for connecting to these terminals is provided on the other surface.

The base substrate used in the present invention is, for example, a substrate having a thickness of 0.4 mm and copper foil having a thickness of 18 μm on each side. As the material of the substrate, for example, a glass epoxy substrate FR-4 or FR-5, BT resin (bismaleimide triazine resin), or the like is preferable. Although the thickness of the copper foil was 18 μm here, it was 9 to 100 μm.
It may be arbitrarily adjusted in the range of μm. However, when a fine wiring pattern is to be formed on the base substrate, it is preferable that the thickness is thinner in terms of accuracy. When used with a surface acoustic wave element having a sound absorbing material formed thereon, a thickness of about 18 μm is appropriate.

A resist is applied to both surfaces of the substrate, and only necessary portions are exposed to pattern the resist. Thereafter, the resist is dipped in an etching solution of Cu (copper) to partially remove the resist. A pattern can be formed on a circuit board. Usually, the width of the pattern is at least about 100 μm.

Subsequently, Cu plating is performed on the formed Cu wiring pattern by about 15 to 35 μm. Further, Ni (nickel) plating is performed thereon for 5 to 10 μm,
Further, Au (gold) plating is performed thereon for about 0.03 to 2 μm. These may be electrolytic plating or electroless plating.

By doing so, the step between the surface of the base substrate and the surface of the patterned metal is about 40 to 80 μm in total. At this time, it is necessary that there is no coating such as a solder resist on the wiring pattern of the base substrate in order to obtain good electrical connection.

In step S6, a conductive adhesive 5c is applied on the Au plating 5d on the base substrate side.
At 7, the surface of the surface acoustic wave element 1 on which the transducer is formed and the surface of the base substrate 6 on which the wiring pattern is formed face each other, and the conductive adhesive region of the base substrate is connected to the bumps of the surface acoustic wave element. The surface acoustic wave device 1 is flip-chip connected to the base substrate 6 while creating a gap between the base substrate 6 and the transducer 2 of the surface acoustic wave device 1.

In step S8, the sound absorbing material 11 is provided on the surface of the surface acoustic wave element 1 opposite to the surface on which the transducer 2 is located.
Is formed. The end of the sound absorbing material 11 spreads so as to cover the corner 12 of the surface acoustic wave device 1 and extends around the side surface of the surface acoustic wave device 1. That is, the sound absorbing material 11 extends to the side surface of the surface acoustic wave element 1. It is sufficient that this degree does not cover the transducer forming surface of the surface acoustic wave element 1, and it is preferable that the degree of wrap around the surface acoustic wave element is within 1/2 of the thickness of the surface acoustic wave element. Finally, as in step S9, the cap member 9 is mechanically connected to the base substrate 6 by the sealing member 8, and the surface acoustic wave element is hermetically sealed.

The formation of the sound absorbing material 11 in the step S8 can be easily performed by screen printing as in the case of the sound absorbing material 4. Alternatively, the slurry of the sound absorbing material can be provided on the back surface of the surface acoustic wave element 1 by potting, that is, hanging down.

The step of forming the sound absorbing material 11 needs to be performed after the step of connecting the surface acoustic wave element to the flip chip. This is because the sound absorbing material 11 needs to be provided so as to cover the corners 12 of the elastic surface cushioning element 1. Generally, the inner corner 13 of the cap member 9 is formed in an arc as shown in FIG.
2 and this corner 13 are likely to collide. However, by manufacturing as described above, the angle 1 of the surface acoustic wave element 1 can be reduced.
2, when the cap member 9 is connected to the base substrate,
There is no direct contact with the cap member. When the corner 12 of the surface acoustic wave element 1 directly contacts the cap member 9, not only the performance of the surface acoustic wave element 1 is reduced, but also the surface acoustic wave element 1 may be damaged. In the present invention, a sound absorbing material is provided between the surface acoustic wave element 1 and the camping member 9, and the sound absorbing material 11 also functions as a cushioning material.

The material of the sound absorbing material when performing screen printing,
By adjusting the viscosity and the application area, it is possible to make the sound absorbing material 11 wrap around the side surface of the surface acoustic wave element 1. In the case of potting, the sound absorbing material can be made to go around the side surface of the surface acoustic wave element 1 by adjusting the material, viscosity, dropping speed, and temperature of the sound absorbing material. In any case, the corner 12 of the surface acoustic wave element 1
, It is not preferable to lower the viscosity so much. The viscosity is preferably about 3 to 50 Pa · s.

[0031]

As described above, according to the present invention, the sound absorbing material on the back surface of the surface acoustic wave device covers the entire back surface of the device, and its end is larger than the area of the device and goes around the end of the device. With this configuration, the cap member does not directly come into contact with the corner of the surface acoustic wave element, so that cracks, chips, and cracks starting from the corner can be prevented. That is, a surface acoustic wave device having a structure in which a surface acoustic wave element having a back surface sound absorbing material having a role of a cushioning material formed flip-chip connected to a base substrate can be provided at low cost.

[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.

2A is a plan view of a base substrate 6, and FIG. 2B is a bottom view and a side view.

FIG. 3 is a flowchart illustrating a method for manufacturing a surface acoustic wave device according to the present invention.

FIG. 4 is an enlarged cross-sectional view showing a structure of an end portion of the surface acoustic wave device of FIG. 1 and a connection portion with a base substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave element 2 ... Transducer 3 ... Wiring pattern 4, 11 ... Sound absorbing material 5 ... Connection member 5a ... Pad part 5b ... Au bump 5c ... Conductive adhesive 5d ... Au plating layer 5e ... Ni plating layer 5f ... Cu Plating layer 5 g Cu foil 6 Base substrate 7 Terminal 8 Sealing member 9 Cap member

Claims (5)

[Claims] 1. A transducer, a wiring pattern connected thereto, a pad portion provided on a part of the wiring pattern, a bump formed on the pad portion, and a second electrode for absorbing a surface acoustic wave. A surface acoustic wave element in which one sound absorbing material is formed on one surface and a second sound absorbing material for absorbing surface acoustic waves is formed on the other surface on the opposite side; and one surface is connected to the outside. A base member provided with a terminal, and a wiring pattern connected to the terminal on the other surface; a cap member provided on the base substrate and having a recess larger than the thickness of the surface acoustic wave element; A connection member that electrically and mechanically connects the surface acoustic wave element and the base substrate, and a sealing portion that mechanically connects the cap member and the base substrate and seals the surface acoustic wave element; Surface acoustic wave device The surface on the transducer side has a structure arranged so as to face the other surface of the base substrate on which the wiring pattern is formed, and the second sound absorbing material is provided on the one side of the surface acoustic wave element. A surface acoustic wave device provided so as to extend to a surface and a side surface. 2. A method for forming a plurality of surface acoustic wave devices on one surface of a wafer serving as a surface acoustic wave device,
Forming a plurality of transducers, a wiring pattern connected thereto, and a pad portion on a part of the wiring pattern; forming a first sound absorbing material for absorbing a surface acoustic wave on one surface of the wafer; Forming a connection bump on the pad portion provided on one surface of the wafer; and dividing the wafer on which the plurality of surface acoustic wave elements are formed into individual surface acoustic wave elements. A step of providing a terminal connected to the outside on one surface of the base substrate and providing a wiring pattern connected to these terminals on the other surface; and a part of a wiring pattern provided on the other surface of the base substrate. Disposing a conductive adhesive on the surface of the surface acoustic wave element, and the surface of the surface acoustic wave element on which the transducer is formed and the surface of the base substrate on which the wiring pattern is formed are opposed to each other; The surface of the conductive adhesive is connected to the bump of the surface acoustic wave element, and the surface acoustic wave element is flip-chip bonded to the base substrate while creating a gap between the base substrate and the transducer of the surface acoustic wave element. Connecting; and forming a second sound absorbing material for absorbing surface acoustic waves over a surface of the surface acoustic wave element opposite to a transducer forming surface and a side surface of the surface acoustic wave element. And mechanically connecting the cap member to the base substrate with a sealing member to hermetically seal the surface acoustic wave element;
A method for manufacturing a surface acoustic wave device, comprising: 3. The step of forming the second sound absorbing material,
3. The method for manufacturing a surface acoustic wave device according to claim 2, wherein the method is performed after the flip chip connecting step of the surface acoustic wave element. 4. The method for manufacturing a surface acoustic wave device according to claim 2, wherein the second sound absorbing material is formed by screen printing. 5. The method of manufacturing a surface acoustic wave device according to claim 2, wherein the formation of the second sound absorbing material is performed by potting.