GB2297424A

GB2297424A - Surface acoustic wave device

Info

Publication number: GB2297424A
Application number: GB9601285A
Authority: GB
Inventors: Seiichi Arai; Hiroaki Tanaka
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 1995-01-26
Filing date: 1996-01-23
Publication date: 1996-07-31
Anticipated expiration: 2016-01-23
Also published as: GB2297424B; DE19602665C2; DE19602665A1; GB9601285D0; JPH08204497A

Description

2297424 I SURFACE ACOUSTIC WAVE DEVICE

BACKGROUND OF THE INVENTION

The present invention relates to an surface acoustic wave (hereinafter abbreviated as SAW) device with improved packaging, in particular to a SAW device being arranged to facilitate packaging of the SAW device.

SAW devices, such as SAW resonators, SAW delay lines, SAW filters, elastic (SAW) convolvers (convolution devices using piezoelectric materials) and the like have been put to practical use in the prior art. The structures of these types of SAW device products will be explained taking the SAW filter as an example.

FIG. 1 is a partially exploded perspective view of an example of a conventional SAW device. A SAW filter element 2 is attached to the top of a plate-shaped base 1 formed by an insulative ceramic, synthetic resin or the like. The SAW filter element 2 has a structure with a pair of interdigital transducers (hereinafter abbreviated as IDT) 2b and 2c separated by a predetermined distance and f ormed on the upper surf ace of a surf ace wave base 2a. Each IDT 2b and 2c is formed by a pair of electrodes in the shape of the teeth of a comb the fingers of the electrodes mutually interfitting with each other.

In the SAW filter element 2 one IDT 2b is used as an input IDT or an output IDT and the other IDT 2c is used as an output IDT or input IDT, and a surface wave is transmitted between the IDTs 2b and 2c.

2 In the structure shown in FIG. 1, the SAW filter element 2 is fixed to the base I using an insulative adhesive or the like so that the surface wave conveying surface of the SAW filter element 2 is the upper surface. Also, a plurality of lead terminals 3a to 3d are f ixed to the base 1. The upper ends of these lead terminals 3a to 3d protrude in the upward direction of the base 1, and the lower ends of the terminals 3a to 3d extend in the downward direction of the base 1. The IDTs 2b and 2c of the SAW filter element 2 are electrically connected to the lead terminals 3a to 3d by bonding wires 4a to 4d.

Also, a metal cap 5 is fixed to the base 1 from above. In this way, the SAW filter element 2 is enclosed in the package formed by the base 1 and the metal cap 5. In the SAW filter element 2, if contaminants adhere to the surface wave conveying surface, the characteristic of the SAW filter element 2 deteriorates. Also, the IDTs 2b and 2c are normally made of aluminum in order to reduce cost However, the comb-shaped electrodes made from aluminum easily oxidize in a high-humidity atmosphere. If the combshaped electrodes are made from aluminum oxidize, conductivity decreases or weight increases, and the resonance characteristic deteriorates.

Accordingly, in the prior art, by forming an enclosed package by means of the metal cap 5 and the base 1, the SAW f ilter element 2 is enclosed within this package.

FIG. 2 is an exploded perspective view of another example of a package structure of a conventional SAW device. In the structure shown in FIG. 2, a package member 6 made of ceramic is used. The 3 package member 6 has a flat plane shape which is rectangular and has an opening 6a which opens upward. The SAW filter element 2 is fixed within this opening 6a. In other words, the SAW f ilter element 2 is fixed therein by adhering it to the bottom surface of the opening 6a using an insulative adhesive. Also, terminal electrodes 7a to 7d. are formed in an indented portion of the package, these terminal electrodes 7a to 7d being connected to the external surface of the package member 6. The terminal electrodes 7a to 7d are electrically connected to the IDTs 2b and 2c of the SAW f ilter element 2 by bonding wires 8a to ad.

In this structure, a metal plate 9 is fixed to the top surface of the package member 6 so as to seal the opening 6a. In this way, in the same manner as in the example shown in FIG. 1, the SAW filter element 2 is enclosed within the package. Note that, although omitted from FIG. 2, external electrodes are formed on the external surface of the package member 6 and are electrically connected to the terminal electrodes 7a to 7d.

In the conventional SAW devices shown in FIG. 1 and FIG. 2, because the SAW filter element 2 is enclosed within a package, deterioration of the resonance characteristic thereof due to adhesion of contaminants to the surface wave conveying surface and deterioration of the resonance characteristic due to oxidation of the IDTs can be somewhat prevented.

However, bonding wires 4a to 4d and Sa to ad are used in the electrical connections between the SAW filter element 2 and the lead 4 terminals 3a to 3d and terminal electrodes 7a to 7d on the package side. Consequently, not only must a complex connecting function be carried out by means of the bonding wires, but the use of bonding wires 4a to 4d and 8a to 8d makes it extremely difficult to reduce the thickness of the entire structure.

In recent years, in remote control devices which utilize electromagnetic waves, thin and compact products have been in great demand, therefore there has also been a great demand for reduction in the thickness of SAW devices which are used in such applications. However, reduction of thickness has been difficult with the structures shown in FIG. 1 and FIG. 2, and consequently the above demands have not been met.

Indeed, by mounting a SAW filter element 2 directly on a printed circuit board 10 as shown in FIG. 3, it is possible to achieve a thinner circuit incorporating the SAW filter element 2.

However, in the structure shown in FIG. 3, because the SAW filter element 2 is exposed, adhesion of contaminants on the surface wave conveying surface cannot be avoided. For example, as shown in FIG. 3, where a transistor 11, IC 12, capacitor 13, etc. as well as the SAW filter element 2 are mounted and soldered, contaminants adhere to the surface wave conveying surface of the SAW filter element 2. In addition, because the surface wave conveying surface of the SAW filter element 2 is exposed, deterioration in the resonance characteristic results from the effect of flux and atmospheric gases during soldering.

Further, because the SAW f ilter element 2 is exposed, during actual use deterioration of the resonance characteristic has occurred due to oxidation of the electrodes which form the IDTs 2b and 2c, and deterioration of the resonance characteristic and shorting have occurred due to adhesion of contaminants.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a SAW device which can reliably prevent deterioration of the resonance characteristic and performance of the SAW device during manufacture and practical use, and allow the thickness of the overall structure of the SAW device to be substantially reduced.

According to a first aspect of the present invention there is provided a surface acoustic wave device comprising a plate-shaped base, a plurality of bumps formed on the base for providing electrical connections, a surface wave element mounted on the base with a surface wave conveying surface facing downward, the surface wave element being f ixed to the base by means of the bumps and being electrically connected to the bumps, and a packaging resin layer arranged so as not to protrude into a space exposing the surf ace wave conveying surface of the surface wave element and to cover at least the surface wave element.

In the first aspect of the invention, an indented portion is preferably formed in an area opposite the surface wave conveying surface of the surface wave element of the base.

6 Also, the packaging resin layer preferably comprises a first resin layer which forms an inside portion of the packaging resin layer and is relatively soft, and a second resin layer which is formed on the outside of the first resin layer and is relatively hard.

According to a second aspect of the present invention there is provided a SAW device comprising a plurality of lead terminals, a plurality of bumps formed on upper surfaces of the plurality of lead terminals for providing electrical connections, a surface wave element mounted on the plurality of lead terminals with a surface wave conveying surface facing downward, the surface wave element being fixed to the plurality of lead terminals by means of the bumps and being electrically connected to the bumps, and a packaging resin layer arranged so as not to protrude into a space exposing the surface wave conveying surface of the surface wave element and to cover at least the surface wave element.

Also in the second aspect of the invention, an indented portion is preferably formed in an area opposite to the surface wave conveying surface of the surface wave element of the base.

According to a third aspect of the present invention there is provided an electronic device comprising:

a printed circuit board; a plurality of bumps mounted on the printed circuit board; a surface wave element mounted on the printed circuit board such that a surface wave conveying surface of the surface wave 7 element faces an upper surface of the printed circuit board, the surface wave element being fixed to the printed circuit board by the bumps and being electrically connected to the bumps; and a resin layer located on the surface wave element so as to not protrude into a space between the upper surface of the base and the surface wave conveying surface of the surface wave element and such that the resin layer covers at least the surface wave element.

In the first aspect of the invention of the present application, the surface wave element is mounted on the plate-shaped base by a face-down method, and the surface wave element and the base are connected by bumps. In other words, because the part of the surface wave element electrically connected to the bumps is formed on the surface wave conveying surface, by mounting the surface wave element on the base by the face-down method, as well as, fixing of the surface wave element to the base by means of the bumps, achieving electrical connection is possible. Further, since electrical connection is performed by means of the bumps, reduction of the thickness of the overall structure can be achieved compared to an electrically connected structure using bonding wires.

In addition, because the surface wave element is covered by the packaging resin layer, the thickness of the entire surface wave device is reduced. In particular, when a packaging resin layer is formed so that it covers only the portion of the device where the surface wave element is formed, because it is unnecessary to cover the lower surface of the base with the packaging resin, the overall thickness can be reduced even further.

8 Also, although the surface wave element is fixed onto the base with the surface wave conveying surface defining a lower surface, the surface wave conveying surface and the base are separated by a space corresponding to the thickness of the bumps. Further, because the depth of this space (the distance between the surface wave conveying surface and the base) is determined by the thickness of the bumps, the depth of the space is very small. Thus, when the resin is applied and hardened to form the packaging resin layer, intrusion of the resin into this space can be prevented by the surface tension of the resin in its molten state. Accordingly, a space which does not hinder excitation and conveyance of surface waves can be reliably defined between the surface wave conveying surface and the base.

in a preferred mode of the present invention, an indented portion is formed in an area facing the surface wave conveying surface of the surface wave element of the base and consequently the space between the surface wave conveying surface and the base can be more reliably formed.

Further, where the packaging resin layer having first and second resin layers is formed, the compression stress on the surface wave element from the packaging resin can be alleviated by the first resin layer and the strength of the packaging resin can be maintained by the second resin layer.

In the second aspect of the invention, the surface wave element is preferably disposed by the face-down method in the same manner as the first aspect of the invention. In the second aspect of the invention, the surface wave surf ace of the lead terminals between the ton surface of 9 element is joined by bumps on the top and consequently, a space is formed the lead terminals and the surface wave conveying surface so that the excitation and conveyance of surface waves are not hindered. Also in this case, when the resin forming the packaging resin layer is applied and hardened, intrusion of the resin into this space is prevented by the surface tension of the molten resin. Consequently, the packaging resin layer can be produced with a space which exposes the surface wave conveying surface reliably formed therein.

Also, since the lead terminals and surface wave element are joined by the above-mentioned bumps, i.e. connected without using bonding wires, the thickness of the entire surface wave device can be reduced.

Further, in the second aspect of the invention, the packaging resin layer is preferably formed with first and second resin layers, the compression stress added to the surface wave element from the packaging resin can be alleviated by the first resin layer, and the strength of the packaging resin can be maintained by the second resin layer.

According to both the first and second aspects of the invention, the surface wave element is reliably enclosed within the packaging resin layer and the surface wave conveying surface is reliably exposed in the above-mentioned space. Thus, it is difficult for deterioration of characteristics to occur with time, and a surface wave device having excellent reliability can be provided. In addition, because joining of the surface wave element and the base or the lead terminals is carried out by means of the bumps and bonding wires are not used, the thickness of the entire SAW device can be reduced. Thus, it is possible to provide a SAW device which is suitable for applications wherein compactness is in great demand.

The present invention can be widely applied in SAW devices using various SAW elements such as SAW resonators, SAW filters, SAW delay lines, elastic convolvers, etc. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described with reference to the accompanying drawings, wherein:

FIG. I is an exploded perspective view for illustrating an example of a conventional SAW device.

FIG. 2 is an exploded perspective view for illustrating another example of a conventional SAW device.

FIG. 3 is a perspective view showing yet another example of a conventional SAW device.

FIG. 4 is a cross-sectional view of a SAW device of a first embodiment.

FIG. 5 is a plan view of a SAW element used in the f irst embodiment.

FIG. 6 is a cross-sectional view showing a SAW device of a second embodiment.

11 FIG. 7 is a cross-sectional view showing a SAW device of a third embodiment.

FIG. 8 is a cross-sectional view for illustrating a SAW device of a fourth embodiment.

FIG. 9 is a cross-sectional view for illustrating a SAW device of a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

FIG. 4 is a cross-sectional view for explaining a SAW device according to a first embodiment of the present invention. The SAW device 21 of the present embodiment has a base 22. The base 22 can be formed from an insulative ceramic such as alumina, etc. and the surface of the base 22 can be formed with a suitable insulative material such as some other insulative ceramic or synthetic resin, etc. Solder bumps 23 and 24 are formed on the base 22. The solder bumps 23 and 24, are provided for fixing a SAW element 25 onto the base 22 and for electrically connecting the SAW element 25 to a wiring pattern (not shown) formed on the base 22.

In the present embodiment, although the solder bumps 23 and 24 are used, the bumps 23 and 24 may be formed using another material, for example silver solder, as long as the material can fix the SAW element 25 and achieve electrical connection.

The SAW element 25 is fixed to the base 22 by a face-down method such that the surface wave conveying surface 25a of the SAW element is facing downward opposite to an upper surface of the base 22. The electrode structure of the SAW element 25 will be explained referring to the plan view of FIG. 5.

12 The SAW element 25 has a structure wherein a pair of IDTs 27 and 28 are formed on the surface of a rectangular surface wave base 26 separated by a predetermined distance. Each IDT 27 and 28 has a pair of comb-teethshaped electrodes 27a, 27b, 28a and 28b, the fingers of the electrodes mutually interfitting with each other. Also, terminal electrodes 29a to 29d are formed so as to electrically connect the comb-teeth-shaped electrodes 27a, 27b, 28a and 28b. The terminal electrodes 29a to 29d form portions which join the solder bumps 23 and 24 described previously. In other words, the terminal electrodes 29a to 29d are electrically connected by the solder bumps 23 and 24 to a wiring pattern formed on the base 22.

Although the above IDTs 27 and 28 and the terminal electrodes 29a to 29d can be formed of any suitable conductive material, using electrodes made of aluminum, which is relatively inexpensive, is preferable.

The SAW element 25 is a transversal type SAW filter with the IDTs 27 and 28 arranged to be separated by a predetermined distance. One of the IDTs 27 and 28 functions as the input IDT and the other functions as the output IDT. Returning to FIG. 4, although the SAW element 25 is fixed to the top of the base 22 with the surface wave conveying surface 25a arranged to be the lower surface of the SAW element 25, in this case, a space 30 having a depth corresponding to the thickness of the solder bumps 23 and 24 is formed between the surface wave conveying surface 25a and the upper surface 22a of the base 22.

13 Also, in the SAW device 21 of the present embodiment, a packaging resin layer 31 is arranged to cover the SAW element 25. The packaging resin layer 31 preferably includes a thermosetting resin such as epoxy resin for example, and can be formed by hardening through the application of heat. In such a case, the resin in its molten state does not intrude into the space 30. Since the thickness of the bumps 23 and 24 is extremely small in the order of 50-100 pm, flowing of the resin into the space 30 is prevented due to the surface tension of the molten resin. Consequently, the thickness of the bumps 23 and 24 and the viscosity of the molten resin may be selected such that the space 30 is reliably formed.

In the SAW device 21 of the present embodiment, in a state where the space 30 is formed in the interior as described above, the SAW element 25 is covered by the packaging resin layer 31. Consequently, because the surface wave conveying surface 25a is exposed in the space 30, the filter characteristic is not easily affected by the packaging resin layer 31. Furthermore, because the periphery of the SAW element 25 is covered by the packaging resin layer 31, the combteeth-shaped electrodes etc. of the SAW element 25 do not easily deteriorate due to the surrounding atmosphere and other causes. Thus, a surface wave device whose characteristics do not easily deteriorate with time can be provided.

Further, since the SAW device 21 has a structure where the SAW element 25 is attached to the base 22 using the solder bumps 23 and 24 and the SAW element 25 is covered by the packaging resin layer 31, 14 i.e. it is not necessary to join the SAW element 25 to the base 22 using bonding wires, the thickness of the entire device can be significantly reduced.

FIG. 6 is a cross-sectional view showing a SAW device 41 according to a second embodiment of the present invention. The SAW device 41 of the second embodiment has substantially the same structure as the first embodiment with the exception of an indented portion 22b formed in the upper surface of the base 22. Accordingly, only those points which differ from the first embodiment will be explained, and the explanation of the first embodiment will be referred to regarding points other than these.

The indented portion 22b is preferably formed in an area facing the surface wave conveying surface 25a of the SAW element 25, and only the portion of the surface wave conveying surface where the indented portion 22b is formed is reliably exposed to the space 30. In other words, because the indented portion 22b is formed, even where the thickness of the bumps 23 and 24 is very small, the surface wave conveying surface 25a can be reliably exposed in the space 30. In other words, in the first embodiment, the depth of the space 30 is controlled by the thickness of the solder bumps 23 and 24. In the second embodiment, the indented portion 22b is provided. Therefore, the space 30 can be reliably formed even when the thickness of the solder bumps 23 and 24 is very small and consequently precise control of the thickness of the solder bumps 23 and 24 is not necessary.

is FIG. 7 is a cross-sectional view for explaining a SAW device of a third embodiment of the present invention. The SAW device 51 of the third embodiment has substantially the same structure as the first embodiment with the exception that the packaging resin layer 52 differs from that of the first embodiment. Accordingly, the first embodiment will be referred to by using the same reference numerals which will be assigned to portions which are the same as those in the first embodiment.

The packaging resin layer 52 has a first resin layer 53 forming an inner portion of the packaging resin layer 52 adjacent the SAW element 75 and a second resin layer 54 formed outside of the first layer 53 forming an outer portion of the packaging resin layer 52. The first resin layer 53 is preferably formed by a resin material which is relatively soft compared to the second resin layer 54. This first resin layer 53 is provided to prevent deterioration of the characteristics of the SAW element 25 due to the compression stress from the packaging resin layer 52. Accordingly, as the resin material forming the first resin layer 53, a material having a suitable hardness which does not easily give rise to deterioration of the characteristic of the SAW element 25 can be used.

Also, the second resin layer 54 is provided to protect the SAW device 51 from mechanical impacts from the outside, and is formed with a resin material which is hard compared to the first resin layer 53.

16 As an example of a combination of materials for forming the f irst and second resin layers as described above, the first resin layer preferably is formed by an epoxy resin and the second resin layer preferably includes a material whose hardness is increased by adding a predetermined amount of filling agent such as silica or the like to epoxy resin. In this way, by forming the first and second resin layers using the same thermosetting resin, hardening of the first and second resin layers can be performed by means of a single process. Indeed, as a material for forming the first and second resin layers, there is no specific limit thereto, and any suitable resin material can be used as long as the above functions can be achieved.

FIG. 8 is a cross-sectional view for explaining a SAW device according to a fourth embodiment of the present invention. The SAW device 61 of the present embodiment has a plurality of lead terminals 62 and 63. The lead terminals 62 and 63 are preferably formed by a suitable metallic material such as bronze, aluminum, stainless steel or an alloy thereof. Solder bumps 64 and 65 are formed on the surface in the vicinity of the front ends of the lead terminals 62 and 63. The SAW element 25 is attached by the face-down method above the solder bumps 64 and 65. In other words, the junction structure of the solder bumps 64 and 65 and the SAW element 25 is the same as the junction structure of the solder bumps 23 and 24 with the SAW element 25 in the first embodiment.

17 Internal ends 62a and 63a of the lead terminals 62 and 63 are separated by a predetermined distance as shown in the drawing. Accordingly, the surface wave conveying surface 25a of the SAW element 25 is exposed to a space between the lead terminals 62 and 63 and the space has a depth defined by the solder bumps 64 and 65.

Note that 66 indicates a carrier tape preferably arranged to adhere to the lead terminals 62 and 63. The carrier tape 66 is provided to convey the lead terminals 62 and 63 in a state where they are disposed in a predetermined positional relationship during manufacturing.

In other words, formation of the solder bumps 64 and 65 and joining of the SAW element 25 are performed with'the plurality of lead terminals 62 and 63 adhered on the carrier tape 66 in a predetermined positional relationship. Immediately thereafter, the first resin layer 67 is formed so as to cover the SAW element 25.

The first resin layer 67 is preferably formed by the same material as the first resin layer 53 used in the third embodiment. Also, the f irst resin layer 67 is applied so as to cover the upper surfaces of the lead terminals 62 and 63 and the SAW element 25. Further, all remaining portions of the lead terminals 62 and 63 with the exception of the extracted portions thereof are covered by a second resin layer 68. As the resin material for forming the second resin layer 68, the same material as the resin material for forming the second resin layer 54 used in the third embodiment can be used.

18 Also in the present embodiment, since the packaging resin layer 69 has the first resin layer 67 and the second resin layer 68, the compression stress added to the SAW element 25 from the packaging resin layer can be alleviated by the first resin layer 67. Also, mechanical impact resistance is increased by the second resin layer 68. Accordingly, in the same manner as in the third embodiment, a SAW device can be formed with excellent reliability.

Furthermore, in the present embodiment, the overall thickness of the device can be reduced because bonding wires are not used in the junction between the lead terminals 62 and 63 and the SAW element 25.

Note that, in the fourth embodiment, the packaging resin layer may also be formed by a single synthetic resin as in the first embodiment. Further, although the carrier tape 66 is used in the present embodiment, the carrier tape 66 may also be omitted. In other words, the plurality of lead terminals 62 and 63 may be disposed in a predetermined positional relationship inside a metal die, for example, and the steps of forming the solder bumps 64 and 65, joining the SAW element 25 and covering by the packaging resin layer may be performed.

FIG. 9 is a cross-sectional view for explaining a SAW device according to a fifth embodiment of the present invention. The SAW device 71 of the fifth embodiments formed using a printed circuit board 72. In other words, on the printed circuit board 72 on which transistors 73 and other electronic components are mounted, the SAW 19 element 25 is attached by the face-down method. The SAW element 25 is f ixed to, and achieves electrical connection with, the printed circuit board 72 by means of solder bumps 23 and 24 formed on the printed circuit board 72.

Also, a packaging resin layer 74 is formed so as to cover the SAW element 25, the transistors 73 and other circuit components. Accordingly, as in the first embodiment, since the SAW element 25 is fixed on the printed circuit board 72, which functions as a base, without the used of bonding wires, the thickness of the SAW device 71 can be reduced compared to a conventional SAW device using -bonding wires.

Furthermore, in the same manner as the first embodiment, since a space 30 is defined between the surface wave conveying surface 25a of the SAW element 25 and the base 22, there is no possibility that the packaging and structure of the SAW element 25 hinders the excitation and conveyance of surface waves.

In this way, in the SAW device of the present invention, a previously existing printed circuit board 72 can be used as the base, and othercomponents such as transistors 73 etc. may be mounted on the printed circuit board 72 serving as the base.

Also, the packaging resin for enclosing the SAW element 25 may cover not only the SAW element but other circuit components as well. In addition, in the first to third embodiments and the fifth embodiment, although the packaging resin layer covers only the SAW element 25 and is arranged so as not to extend to the lower surface of the base, the packaging resin layer may also be formed so as to cover the lower surface of the base..

Claims

CLAIMS:

1. A surface acoustic wave device comprising:

a base having a lower surface and an upper surface; a plurality of bumps located on the upper surface of the base; a surface wave element mounted on the base with a surface wave conveying surface facing downward toward the upper surface of the base, the surface wave element being fixed to the base by the bumps and being electrically connected to the bumps; and a packaging resin layer located on the surface wave element and being arranged so as to not protrude into a space between the upper surface of the base and the surface wave conveying surface of the surface wave element and such that the resin layer covers at least the surface wave element.

2. A surface acoustic wave device according to claim 1, wherein an indented portion is located in the base in an area opposite to the surface wave conveying surface of the surface wave element.

3. A surface acoustic wave device according to claim 1, wherein the packaging resin layer comprises a first resin layer which is located adjacent the surface wave element and is relatively soft, and a second resin layer which is formed on the outside of the first resin layer and is relatively hard.

4. A surface acoustic wave device according to claim 2, wherein the packaging resin layer comprises a first resin layer which is located adjacent the surface wave element and is relatively soft, and 21 a second resin layer which is formed on the outside of the first resin layer and is relatively hard.

5. A surface acoustic wave device comprising:

a plurality of lead terminals; a plurality of bumps located on upper surfaces of the plurality of lead terminals; a surface wave element mounted on the plurality of lead terminals such that a surface wave conveying surface of the surface wave element is disposed facing downward toward the upper surfaces of the lead terminals, the surface wave element being fixed to the plurality of lead terminals by the bumps and being electrically connected to the bumps; and a packaging resin layer located on the surface wave element such that the packaging resin layer does not protrude into a space between the upper surface of the base and the surface wave conveying surface of the surface wave element and such that the resin layer covers at least the surface wave element.

6. A surface acoustic wave device according to claim 5, wherein the packaging resin layer comprises a first resin layer which is located adjacent the surface wave element and is relatively soft, and a second resin layer which is located on the outside of the first resin layer and is relatively hard.

7. A surface acoustic wave device according to claim 5, further comprising a base, the lead terminals being mounted on the base, the base including an indented portion at a location opposite to the surface wave conveying surface of the surface wave element.

22

8. A surface acoustic wave device according to claim 7, further comprising an adhesive member located in the indented portion and adhered to the lead terminals.

9. An electronic device comprising:

a printed circuit board; a plurality of bumps mounted on the printed circuit board; a surface wave element mounted on the printed circuit board such that a surface wave conveying surface of the surface wave element faces an upper surface of the printed circuit board, the surface wave element being fixed to the printed circuit board by the bumps and being electrically connected to the bumps; and a resin layer located on the surf ace wave element so as to not protrude into a space between the upper surface of the base and the surface wave conveying surface of the surface wave element and such that the resin layer covers at least the surface wave element.

10. The electronic component of claim 9, further comprising at least one transistor mounted on the printed circuit board, the resin layer covering the at least one transistor.

11. A surface acoustic wave device substantially as hereinbefore described with reference to Figures 4 to 9 of the accompanying drawings.