JPH1032460A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave(SAW) device capable of substantially improve the hermetic sealability of a metal cap and a base substrate. SOLUTION: A SAW element 20 is mounted on the base substrate 10, the base substrate 10 and the metal cap 30 are joined by solder 52 by a reflow soldering method and the SAW element 20 is sealed inside a package constituted of the base substrate 10 and the metal cap 30. The one whose entire surface is Ni plated is used for the metal cap 30.

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, and more particularly, to a surface acoustic wave device having a structure in which a SAW element mounted on a base substrate is sealed in a package composed of the base substrate and a metal cap. The present invention relates to a surface acoustic wave device.

[0002]

2. Description of the Related Art Conventionally, as a surface acoustic wave device in which a package structure is constituted by a base substrate and a metal cap, there is a device as shown in FIGS.

As shown in FIGS. 1 and 2, in this surface acoustic wave device, a SAW element 20 is mounted by soldering on a base substrate 10 made of an insulating ceramic such as alumina. The SAW element 20 is sealed by joining the metal cap 10 and the metal cap 30 with solder 52.

[0004] As shown in FIG. 1, on the upper surface of the base substrate 10, an annular ring-shaped bonding land 11 for bonding to a metal cap 30, electrode lands 12 a and 12 b for soldering the SAW element 20, and Electrode lands 12a, 1
Lead electrodes 13a and 13b are formed to be connected to 2b to achieve desired electrical connection. Although not shown, an input / output terminal electrode and a ground terminal electrode are formed on the lower surface of the base substrate 10, and the extraction electrode 13a serves as the input / output terminal electrode.
The extraction electrode 13b is connected to the ground terminal electrode by a through hole. One end of each of the two extraction electrodes 13b connected to the ground terminal electrode is connected to the bonding land 11 so that the bonding land 11 and the ground terminal electrode have the same potential.
Has been drawn from.

The SAW element 20 has an IDT and a reflector formed on the lower surface, and is mounted on the base substrate 10 in a face-down manner. That is, the terminal electrodes of the SAW element 20 are soldered to the electrode lands 1 of the base substrate 10 such that the surface on which the IDT and the reflector are formed is the lower surface.
2a and 12b, and are supported and fixed to the base substrate 10.

The metal cap 30 has a shape opened downward, and a flange 31 extending parallel to the base substrate 10 is formed all around the opening. Are bonded to the bonding lands 11.

The joining of the SAW element 20 and the metal cap 30 to the base substrate 10 is performed by a reflow soldering method.
It is sealed with 0. For this solder joining, the surface of the metal cap is plated, and conventionally, Ag plating or Au plating having good solder wettability has been applied.

[0008]

However, in the above-described conventional surface acoustic wave device, a fine gap is formed at a solder joint between the flange portion 31 of the metal cap 30 and the joint land 11 of the base substrate 10 to complete sealing. There was a problem that can not be obtained. And this cause is the metal case 3
Since the solder wettability of Ag plating, Au plating, or the like applied to the solder 52 is too good, the molten solder
Flowed to the upper surface of the flange portion 31 and the like, and the amount of solder at the solder joint portion was reduced or partially eliminated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface acoustic wave device capable of greatly improving the sealing between a metal cap and a base substrate.

[0010]

In order to achieve the above object, the present invention provides a base substrate having bonding lands formed thereon,
A SAW element mounted on the base substrate;
In a surface acoustic wave device comprising a metal cap soldered and bonded to the bonding land so as to seal the W element, the surface of the metal cap is Ni-plated.

According to the above configuration, the surface of the metal cap is plated with Ni having low solder wettability. Therefore, when the metal case is reflow-soldered to the bonding land of the base substrate, the metal case is soldered. The molten solder is prevented from flowing out of the surface (the lower surface of the flange portion). In other words, the solder preliminarily soldered to the joint lands on the base board does not flow to other than the joints, and a predetermined amount of solder can be secured at the solder joints, greatly improving the sealing between the metal case and the base board. it can.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface acoustic wave device according to the present invention will be described below. Since the overall structure is the same as that of the conventional surface acoustic wave device, it will be described with reference to FIGS.

That is, in the surface acoustic wave device according to the present invention, the SAW element 20 is mounted on the base substrate 10, and the base substrate 10 and the metal cap 30 are joined by the solder 52 by the reflow soldering method. Reference numeral 20 is sealed in a package including the base substrate 10 and the metal cap 30.

The entire surface of the metal cap 30 of this embodiment is covered with a Ni plating layer. That is, the conventional Ag
Although the metal case 30 plated with Au or plated with Au is used, in this embodiment, the metal case 30 plated with Ni is used.
Is used.

The metal case 3 thus plated with Ni
After performing reflow soldering under the same conditions as those using the conventional metal cap plated with Ag or Au, the result of comparison of the sealing test was as follows. It was confirmed that the sealing performance was significantly improved as compared with the conventional example.

A metal case 30 for use with a magnifying glass or a microscope.
Observation of the wrap-around of the solder 52 on the upper surface of the flange portion 11 also confirmed that the wrap-around amount of the present embodiment was significantly reduced as compared with the conventional example.

That is, in this embodiment, the metal case is plated with Ni having low solder wettability, and the flow of the molten solder to portions other than the solder joint surface of the metal case during reflow soldering is prevented. A predetermined amount of solder can be secured at the joint, and the sealing between the metal case and the base substrate is greatly improved.

In the above-described embodiment, the SAW element 20 is connected and fixed to the base substrate 10 by the solder 51. However, the connection and fixing of the SAW element 20 to the base substrate 10 are not limited to this. The element is fixed to the base substrate with an adhesive or the like, and SA is
Needless to say, the present invention can be applied to a surface acoustic wave device in which electrical connection between the W element and the base substrate is obtained.

[0019]

As described above, according to the surface acoustic wave device of the present invention, the surface of the metal cap is plated with Ni having low solder wettability, and the metal case is attached to the joint land of the base substrate. At the time of reflow soldering, the molten solder is prevented from flowing out of the metal case other than the solder joint surface. In other words, the solder preliminarily soldered to the joint lands on the base board does not flow to other than the joints, and a predetermined amount of solder can be secured at the solder joints, greatly improving the sealing between the metal case and the base board. it can.

Therefore, according to the present invention, a highly reliable surface acoustic wave device having good sealing performance can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining the present invention and a conventional surface acoustic wave device.

FIG. 2 is a cross-sectional view for explaining the present invention and a conventional surface acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Base board 11 Joining land 20 SAW element 30 Metal cap 31 Flange part

Claims (1)

[Claims] A base substrate on which a bonding land is formed;
A SAW element mounted on the base substrate;
A surface acoustic wave device comprising: a metal cap soldered and bonded to the bonding land so as to seal a W element; wherein the surface of the metal cap is Ni-plated. .