1-Port type surface acoustic wave device

Abstract: Disclosed is a 1-port type surface acoustic wave device which can be produced by using the same tools as used for the production of a 2-port type surface acoustic wave device and which makes it possible to achieve a substantial improvement in terms of impact resistance. A 1-port surface acoustic wave resonator 10 includes a surface acoustic wave substrate 11, on one main surface of which there are formed two dummy bump electrodes 16 in addition to two input/output bump electrodes 15 formed at the forward ends of input/output extraction electrodes 14.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 1-port type surface acoustic wave device consisting of a 1-port surface acoustic wave resonator and a base substrate which are connected together by solder bump bonding. 2. Description of the Related Art Figs. 5 through 7 show the construction of a conventional 1-port type surface acoustic wave device consisting of a base substrate and a 1-port surface acoustic wave resonator placed thereon and connected thereto by solder bump bonding. Fig. 5 is a plan view of the 1-port surface acoustic wave resonator; Fig. 6 is a plan view of the base substrate; and Fig. 7 is a sectional view of the 1-port type surface acoustic wave device. As shown in Fig. 5, this 1-port surface acoustic wave resonator, indicated by numeral 10, includes a surface acoustic wave substrate 11. In the substantially central portion of one main surface of the surface acoustic wave substrate 11, there is provided an IDT electrode 12. Reflector electrodes 13 are provided on either side of the IDT electrode 12. Further, there are provided two input/output extraction electrodes 14 that are led out from the IDT electrode 12. A round input/output bump electrode 15 is formed at the forward end of each extraction electrode 14. The base substrate, which is indicated by numeral 20, is formed of a ceramic material, such as alumina. As shown in Fig. 6, on one main surface of the base substrate 20, there is provided a rectangular-loop-like bonding land 21 for allowing the base substrate to be soldered to a metal cap 30. Further, there are formed two round input/output electrode lands 22 for connecting and securing the 1-port surface acoustic wave resonator 10 to the base substrate electrically and mechanically, and two extraction electrodes 23 which are respectively connected to the input/output electrode lands 22 and which serve to effect a desired electrical connection. On the other main surface of the base substrate 20, there are formed input/output terminal electrodes (not shown) which are connected to the extraction electrodes 23 through through-holes 25 or the like. As shown in Fig. 7, in the conventional 1-port type surface acoustic wave device, the 1-port surface acoustic wave resonator 10 is joined to the base substrate 20 by a face down system. That is, that surface of the 1-port surface acoustic wave resonator 10 on which the electrodes shown in Fig. 5 are formed is faced downwards and, in this condition, the input/output bump electrodes 15 of the 1-port surface acoustic wave resonator 10 are connected and secured, electrically and mechanically, to the input/output electrode lands 22 of the base substrate 20 by means of solder bumps 51. Then, the metal cap 30, one side of which is open, is joined to the bonding land 21 of the base substrate 20 by means of solder 52, whereby the 1-port surface acoustic wave resonator 10 is sealed in the package formed by the base substrate 20 and the metal cap 30. As described above, the 1-port surface acoustic wave resonator has two input/output terminals; in the conventional 1-port type surface acoustic wave device, the 1-port surface acoustic wave resonator 10 is joined to the base substrate 20 by solder bump bonding between the two input/output bump electrodes 15 and the two input/output electrode lands 22 of the base substrate 20, which correspond to the input/output bump electrodes 15, that is, by solder bump bonding at two positions. Apart from the above-described 1-port type surface acoustic wave device, which is equipped with a 1-port surface acoustic wave resonator, there exists a 2-port type surface acoustic wave device which has a construction similar to that of the 1-port type surface acoustic wave device and which has a 2-port surface acoustic wave resonator with two IDT electrodes that is joined to a base substrate by solder bump bonding. The 2-port surface acoustic wave resonator has four terminals: two input/output terminals and two grounding terminals. Generally speaking, bump electrodes and electrode lands corresponding to the four terminals are formed on the 2-port surface acoustic wave resonator and the base substrate. The bump electrodes and the electrode lands which correspond to each other are connected together by solder bump bonding. Thus, the conventional 1-port type surface acoustic wave device has a problem in that, even when it is formed by using a surface acoustic wave resonator and a base substrate which have the same sizes as those of a 2-port type surface acoustic wave device, it is impossible to use the same tools for its production as those used for the production of the 2-port type surface acoustic wave device. For example, the tool used in providing solder bumps on the base substrate and the tool used in effecting solder bump bonding when forming a 1-port type surface acoustic wave device must be different from those used when forming a 2-port type surface acoustic wave device. That is, when producing the above-described 1-port type surface acoustic wave device, it is impossible to use the tools for producing a 2-port type surface acoustic wave device. Thus, it is difficult for the same tools to be used in the production of different types of surface acoustic wave devices, which means that the administration of the tools is rather irksome, resulting in a high cost in terms of administration and production. Further, in the conventional 1-port type surface acoustic wave device, the 1-port surface acoustic wave resonator is only joined to the base substrate by means of two solder bumps, so that the conventional 1-port type surface acoustic wave device exhibits a rather poor impact resistance when, for example, it is dropped. US-A-5,400,950 discloses a method for flip-chip bonding a flip chip to a substrate, which may be a ceramic substrate, printed wiring board, flexible circuit, or a silicon substrate, in which a number of input/output solder bumps are reflowed to both bond the flip chip to the circuit board as well as provide the necessary electrical connection between the flip chip and the circuit board's circuitry. In order to overcome the tendency for the input/output solder bumps to draw the flip chip excessively close to the circuit board, "dummy" solder bumps are present in sufficient numbers. SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide a 1-port type surface acoustic wave device which can be produced by using the same tools as those used for the production of a 2-port type surface acoustic wave device and which can be improved in terms of impact resistance. This object is achieved with a device having the features of claim 1. In the above-described construction, at least four bump electrodes are formed on the 1-port surface acoustic wave resonator, and at least four electrode lands corresponding to the bump electrodes are formed on the base substrate on which the 1-port surface acoustic wave resonator is to be placed, wherein the 1-port surface acoustic wave resonator can be produced by using the same tools as used in the production of a 2-port type surface acoustic wave device of a similar construction, which means it is possible to produce different kinds of surface acoustic wave devices by using the same tools, thereby achieving a reduction in the number of tools. Further, the 1-port surface acoustic wave resonator is connected and secured to the base substrate by at least four solder bumps, whereby a substantial improvement is achieved in terms of impact resistance as compared with the conventional device. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view of a 1-port surface acoustic wave resonator in accordance with an embodiment of the present invention; Fig. 2 is a plan view of a base substrate in accordance with an embodiment of the present invention; Fig. 3 is a sectional of a 1-port type surface acoustic wave device in accordance with an embodiment of the present invention; Figs. 4(a) through 4(d) are plan views of 1-port surface acoustic wave resonators in accordance with other embodiments of the present invention; Fig. 5 is a plan view of a conventional 1-port surface acoustic wave resonator; Fig. 6 is a plan view of a conventional base substrate; and Fig. 7 is a sectional of a conventional 1-port type surface acoustic wave device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will now be described with reference to the drawings. Figs. 1 through 3 show the construction of a 1-port type surface acoustic wave device in accordance with an embodiment of the present invention. Fig. 1 is a plan view of a 1-port surface acoustic wave resonator; Fig. 2 is a plan view of a base substrate; and Fig. 3 is a sectional of a 1-port type surface acoustic wave device. In the drawings, the components which are the same as or equivalent to those of the conventional example are indicated by the same reference numerals, and a detailed description of such components will be omitted. As shown in Fig. 1, in the 1-port surface acoustic wave resonator of this embodiment, indicated by numeral 10, there are formed two round dummy bump electrodes 16 in addition to the two input/output bump electrodes 15 formed at the forward ends of the input/output extraction electrodes 14. Further, in the base substrate of this embodiment, indicated by numeral 20, two round dummy electrode lands 24 are formed in addition to the two input/output electrode lands 22. The two input/output bump electrodes 15 and the two dummy bump electrodes 16 are arranged diagonally on either side of the IDT electrode 12 on the surface acoustic wave substrate 11. The input/output electrode lands 22 and the dummy electrode lands 24, which correspond to the input/output bump electrodes 15 and the dummy bump electrodes 16, are also arranged diagonally on the base substrate 20. As shown in Fig. 3, in the 1-port type surface acoustic wave device of this embodiment, the 1-port surface acoustic wave resonator 10 and the base substrate 20 are arranged such that the surface on which the bump electrodes 15 and 16 are formed and the surface on which the electrode lands 22 and 24 are formed are opposed to each other. The bump electrodes 15 and 16 and the electrode lands 22 and 24 are joined together by means of solder bumps 51, whereby the 1-port surface acoustic wave resonator 10 is connected and secured to the base substrate 20. In the construction of this embodiment, the two input/output bump electrodes 15 are arranged so as to be at the same positions as the input/output bump electrodes of a 2-port surface acoustic wave resonator of a similar construction, and the dummy bump electrodes 16 are arranged so as to be at the same positions as the grounding bump electrodes of this 2-port surface acoustic wave resonator. Similarly, the electrode lands 22 and 24 of the base substrate 20 of this embodiment are arranged so as to be at the same positions as the bump electrodes of a base substrate on which the above 2-port surface acoustic wave resonator is to be placed. In this way, in the 1-port surface acoustic wave resonator 10 and the base substrate 20 constituting the 1-port type surface acoustic wave device of this embodiment, the bump electrodes 15 and 16 and the electrode lands 22 and 24 are formed at the same positions as those of a 2-port type surface acoustic wave device of a similar construction, so that the 1-port type surface acoustic wave device of this embodiment can be produced by using the same tools as those used for the production of a 2-port type surface acoustic wave device of a similar construction. In other words, it is possible to use the same tools for the production of different kinds of surface acoustic wave devices, whereby the administration of the tools is facilitated and the operation of changing tools is simplified, thereby contributing to a reduction in production manhour. Further, in this embodiment, the 1-port surface acoustic wave resonator is connected and secured to the base substrate by four solder bumps, whereby a substantial improvement is achieved in terms of impact resistance as compared with the conventional device. The arrangement (forming positions) of the bump electrodes of the 1-port surface acoustic wave resonator and the electrode lands of the base substrate is not restricted to that of the above-described embodiment. It is also possible to adopt, for example, arrangements as shown in Figs. 4(a) through 4(d). Further, the number of dummy bump electrodes is not restricted to two. It is also possible to provide three dummy bump electrodes, as shown in Fig. 4(d). The number of dummy bump electrodes may be four or more. In this case also, the position at which each of the bump electrodes is formed corresponds to one of the positions where the bump electrodes of a 2-port surface acoustic wave resonator are formed. Further, it is also possible to form three or more dummy electrode lands on the base substrate. The number of dummy electrode lands on the base substrate may be larger than the number of dummy electrodes on the associated surface acoustic wave resonator. In this case, no solder for solder bump bonding is applied to the surplus dummy electrode lands. By thus forming a large number of electrode lands on the base substrate, it is possible to use the same base substrate for many types of surface acoustic wave resonator. While the above embodiment has been described with reference to a 1-port surface acoustic wave resonator of the type in which reflector electrodes are formed on either side of the IDT electrode, the present invention is also applicable to an end-surface-reflection type 1-port surface acoustic wave resonator, which has no reflector electrodes. As described above, the 1-port type surface acoustic wave device of the present invention can be produced by using the same tools as used for the production of a 2-port type surface acoustic wave device of a similar construction, which means it is possible to use the same tools for the production of different kinds of surface acoustic wave devices. As a result, the administration of the tools is facilitated, and a reduction in production manhour can be achieved, thereby making it possible to achieve a substantial reduction in cost. Further, the 1-port surface acoustic wave resonator is connected and secured to the base substrate by at least four solder bumps, whereby a substantial improvement is achieved in terms of impact resistance as compared with the conventional device.

Claims: A 1-port type surface acoustic wave device comprising: a 1-port surface acoustic wave resonator including a surface acoustic wave substrate on which two input/output bump electrodes and two dummy bump electrodes are formed; and a base substrate on which input/output electrode lands and dummy electrode lands are formed, wherein said 1-port surface acoustic wave resonator is joined to said base substrate by connecting the bump electrodes to the corresponding electrode lands by solder bump bonding.

Inventors: MORISHITA HIDEYA, NAKASHIMA KOJI, MORISHITA, HIDEYA, NAKASHIMA, KOJI
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: H03H9
IPC codes: H03H9