JPH03173213A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive device with high reliability by coating the entire piezoelectric substance with a 1st resin, making the substance energized with a conductive member except a part and coating the substance with a 2nd resin. CONSTITUTION:A piezoelectric substance 5 provided with input and output electrode pairs 1, 2 comprising interdigital electrode digits, an earth electrode 3, and an absorbing member 4 is bonded to a cold terminal 11 and a hot terminal 10, and the cold terminal 11 are connected to the input electrode pairs 1, 2 of the piezoelectric substance 5 and the earth electrode 3 with use of lead wires 8, respectively. The entire piezoelectric substance 5 is coated with a thermoplastic resin such as a PPS resin, an aromatic group polyester or polyether sulfone or a thermosetting resin(1st resin) 12 such as an epoxy resin. Except a part where the hot terminal 10 and the resin 12 are brought into contact with each other, the resin 12 is coated by a conductive member 12 to be in continuity with the cold terminal 11 to provided the shield effect. In order to prevent the deterioration in the air-tightness at the contact part between the terminal 11 and the resin 12, a thermosetting resin (2nd resin) 14 such as an epoxy resin is used for sealing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to surface wave devices such as VIP surface wave filters and RF surface wave oscillators used in television receivers, video tape recorders, and the like.

BACKGROUND OF THE INVENTION A conventional surface acoustic wave device will be described below. FIG. 3 is a perspective view of a conventional surface acoustic wave device, with a portion cut away. In Fig. 3, an input electrode pair 1, an output electrode pair 2, and a ground electrode 3 are formed by photolithography on the surface of a piezoelectric substrate made of lithium niobate, lithium tantalate, etc., and an epoxy resin or the like is applied by a printing method. The piezoelectric body 6 consisting of the formed absorber 4 is adhesively fixed to a metal stem 6 with an adhesive such as epoxy resin, and the lead terminal 7 of the stem 6, the input electrode pair 1, the output electrode pair 2, and the ground electrode 4 are connected as leads. Connect with wire 8 and weld cap 9 and stem 6. An electric signal is applied to the input electrode pair 1 of the piezoelectric body 5 to generate a surface acoustic wave, which is propagated and extracted as an electric signal from the output 'iTf;, W pair 2, giving it bandpass characteristics.

Problems to be Solved by the Invention However, in the above conventional configuration, the metal stem 6
The housing is constructed using a metal cap 9, and when sealed, it is welded by resistance heating to isolate it from the outside air and protect the minute electrode pair. However, the heating during welding was uneven, and if there was dirt such as dust or dirt caught on the welding surface, the heating became even more uneven, and in some cases the isolation from the outside air was not complete. Note that punched metal scraps, plating scraps, etc. remained inside the cap 9 during processing, and during use, they fell onto the electrode pair and caused a short circuit between the electrode teeth. Furthermore, the stem 6 has a structure in which the lead terminals 7 are fixed to a perforated metal plate using a glass material, which has the problem of being expensive.

The present invention solves the above-mentioned conventional problems, and aims to provide a low-cost and highly reliable surface acoustic wave device.

Means for Solving the Problems In order to achieve this object, the surface wave device of the present invention has the following features:
It has a structure in which a resin is used as an interior material, a second resin is used as an exterior material, and a part of the surface of the first resin is covered with a conductive member.

Function: With this configuration, since an insulating resin is used for the interior material, there are no quality problems such as short circuits, and since resin is also used for the exterior material, a highly reliable surface acoustic wave device can be obtained at a low cost.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a plan sectional view of a surface acoustic wave device according to an embodiment of the present invention, and FIG. 2 shows a partially cutaway plan view thereof.

In FIGS. 1 and 2, the same parts as in FIG. 3 are given the same numbers. In FIG. 1, a piezoelectric body 6 provided with an input electrode pair 1 consisting of comb-shaped electrode teeth, an output electrode pair 2 consisting of comb-shaped electrode teeth, a ground electrode 3, and an absorbing material 4 is glued onto a cold terminal 11, and Terminal 10 or cold terminal 1
1 to the input/output electrode pair 1.2 of the piezoelectric body 6 and the ground electrode 3
are connected with lead wires 8. The entire piezoelectric body 6 constructed as described above is made of pps resin (polyphenylene sulfide resin), wholly aromatic polyester which is a type of liquid crystal polymer, thermoplastic resin such as polyether sulfone, or thermosetting resin such as epoxy resin. First resin 1
Cover with 2. By adjusting the molding and curing conditions of the first resin 12, a gap of several microns or more can be formed between the input/output electrode pair 1, 2 and the ground electrode 3 and the first resin 12 by utilizing resin contraction during molding. , excitation/propagation of surface acoustic waves
Avoid interfering with reception. Except for the portion where the hot terminal 1o and the first resin 12 are in contact, the first resin 12 is covered with a conductive member 13 to be electrically connected to the cold terminal 11 and to provide a shielding effect. For the conductive member 13, a conductive film or a metal plating film formed by using a pad printing method using metal foil such as aluminum foil, silver paste, copper paste, etc. is used. Note that in order to strengthen the bond between the cold terminal 11 and the conductive member 13, a conductive paste may be applied and hardened to the bonded portion. In order to prevent deterioration of airtightness at the contact portion between the terminal and the first resin 12, the second resin 14 is sealed with a thermosetting resin such as epoxy resin.

As described above, since an insulating resin is used for the interior material of the first resin 12, the piezoelectric body 6 can be uniformly sealed without generating metal debris. Since a highly reliable thermosetting resin used for semiconductors is used as the second resin 14 for the exterior material, it is possible to achieve a highly airtight seal. The conductive member can also provide a shielding effect similar to that of a metal cap. The resin coating also has the effect of being cheaper than a metal cap.

Note that a surface acoustic wave resonator having resonance characteristics by combining a comb-shaped electrode pair and a reflector can also have the same structure as the surface acoustic wave device of the present invention.

Effects of the Invention As described above, the present invention covers the entire piezoelectric body with the first resin, makes the entire piezoelectric body conductive with a conductive member except for a part, and then covers the piezoelectric body with the second resin.
By using a resin-coated structure, it is possible to realize a low-cost, highly reliable surface acoustic wave device.

[Brief Description of the Drawings] Fig. 1 is a plan sectional view of a surface wave device according to an embodiment of the present invention, Fig. 2 is a partially cutaway plan view, and Fig. 3 is a partially cutaway view of a conventional surface wave device. FIG. 6...Piezoelectric body, 10...Hot terminal,
11. Old... Cold terminal, 12... First resin, 13... Conductive member, 1 4... Second resin. Figure 1

Claims (1)

[Claims] At least one electrode pair consisting of comb-shaped electrode teeth for exciting and receiving surface acoustic waves is provided on the piezoelectric body, the piezoelectric body is entirely covered with a first resin, and then covered with a second resin, A surface wave device in which the surface of the first resin except for the area around the hot terminal of the piezoelectric body is covered with a conductive member, and the conductive member is electrically connected to the area around the cold terminal.