JP3738600B2 - Surface mount type piezoelectric components - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface mount piezoelectric component using a package formed by seam welding a metal lid to a ceramic substrate.
[0002]
[Prior art]
Piezoelectric components such as crystal resonators, crystal oscillators, and filters are widely used in mobile communication devices such as mobile phones. In recent years, there is an increasing demand for smaller and thinner devices, and there is a demand for smaller and thinner piezoelectric components used in these devices, and surface-mounted piezoelectric components using ceramic packages have attracted attention. ing.
[0003]
FIG. 2 is a cross-sectional view of a conventional surface mount piezoelectric component. The multilayer ceramic substrate 13 has a three-layer structure including a lower stage 13a, a middle stage 13b, and an upper stage 13c. The electrode metallized layer 4 is formed on the middle stage 13b, and the bottom surface of the multilayer ceramic base 13 is formed by via holes 8 penetrating the multilayer ceramic base 13. The input / output terminal metallization layer 5 is electrically connected. On the electrode metallized layer 4, the piezoelectric element 2 is bonded by the conductive adhesive 14, and the piezoelectric element 2 is held in the vibration space 3 using the step of the multilayer ceramic substrate 13. A metal ring 15 is brazed onto the bonding metallization layer 7 formed on the upper stage 13c of the multilayer ceramic substrate 13 via a metal brazing material 9 such as silver brazing. A flat metal lid 12 is seam welded to the metal ring 15 to hold the piezoelectric element in an airtight manner.
[0004]
The thickness of the multilayer ceramic base 13 is about 0.3 mm for the lower stage 13a, about 0.2mm for the middle stage 13b, and about 0.2mm for the upper stage 13c. The thicknesses are about 0.2 mm and 0.1 mm, respectively, and the total height of the surface-mount type piezoelectric component is about 1.0 mm.
[0005]
[Problems to be solved by the invention]
The conventional surface-mount type piezoelectric component described above has a problem that it is difficult to reduce the thickness of the package because a multilayer ceramic substrate having a three-layer structure is used so as to secure a vibration space of the piezoelectric element.
[0006]
In addition, when seam welding a metal lid to a metal ring, heat and pressure from the welding electrode are directly applied to the multilayer ceramic substrate located directly below the metal ring, causing cracks in the multilayer ceramic substrate and impairing airtightness. There is also a problem that reliability as a piezoelectric component is lowered.
[0007]
When the thickness of the ceramic substrate of each layer is reduced in order to reduce the thickness of the package, the generation of the cracks becomes more remarkable because the package strength decreases.
[0008]
The present invention solves the above-described problems, and an object of the present invention is to provide a surface-mount type piezoelectric component capable of reducing the thickness of the package and maintaining the reliability.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a metallized layer for an electrode on the upper surface of a ceramic substrate, holds a piezoelectric element on a metal brazing material formed on the metallized layer for the electrode, A shell-like metal ring is brazed onto a metallization layer for bonding formed in the periphery, and a metal lid is seam welded onto the shell-like metal ring.
[0010]
According to the present invention, since the piezoelectric element is held on the metal brazing material formed on the metallized layer for electrodes, the vibration space of the piezoelectric element can be secured even when a single-layer ceramic substrate is used. The surface mount piezoelectric component can be thinned.
[0011]
Further, since heat generated when seam welding the metal lid can be radiated to the outside by the shell-shaped metal ring having a large surface area, the heat is not directly transmitted to the ceramic substrate. In addition, since the pressure from the welding electrode can be reduced by the spring effect of the shell-shaped metal ring, no pressure is directly applied to the ceramic substrate. For this reason, a crack is not generated in the ceramic substrate, and airtightness can be maintained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1A is a cross-sectional view of a surface-mounted crystal resonator according to the present embodiment, FIG. 1B is a top view with a part of the crystal resonator omitted, and FIG. 1C is a bottom view of the crystal resonator. .
[0013]
An electrode metallization layer 4 made of tungsten or the like is formed on the upper surface of the ceramic substrate 1, and is electrically connected to an input / output terminal metallization layer 5 formed on the lower surface of the ceramic substrate 1 by a via hole 8 penetrating the ceramic substrate 1. .
[0014]
A metal brazing material 10 such as silver brazing is formed on the metallized layer 4 for electrodes, and the piezoelectric element 2 is held on the metal brazing material 10 by a conductive adhesive 14 such as a silver paste. The vibration space 3 of the element 2 is secured. The height of the metal brazing material 10 was about 50 to 100 μm including the electrode metallized layer 4. The metal brazing material 10 is formed by placing a rod-shaped metal brazing material (not shown) on the electrode metallization layer 4 and heating it to rise at the end of the electrode metallization layer 4 due to surface tension.
[0015]
A metallization layer 7 for bonding is formed around the upper surface of the ceramic substrate 1, and a shell-like metal ring 11 made of kovar material (iron 54% -nickel 28% -cobalt 18%) or the like is formed on the metal brazing material 9. It is brazed. The shell-shaped metal ring 11 was formed by drawing a metal flat plate having a thickness of about 0.1 mm by a press means and punching out the center of the bottom surface. A flat metal lid 12 is joined to the shell-shaped metal ring 11 by seam welding. The bonding metallization layer 7 is electrically connected to the ground terminal metallization layer 6 formed on the lower surface of the ceramic substrate 1 by a via hole 8 penetrating the ceramic substrate 1.
[0016]
The ceramic substrate 1 according to this embodiment has a thickness of about 0.3 mm, the shell-shaped metal ring 11 has a height of about 0.3 mm, and the metal lid 12 has a thickness of about 0.1 mm. The total height of the piezoelectric parts is about 0.7 mm, realizing a reduction in thickness.
[0017]
With such a configuration, the piezoelectric element 2 is held on the metal brazing material 10 formed so as to be raised on the electrode metallization layer 4, so that the vibration space of the piezoelectric element 2 can be secured even if the single-layer ceramic substrate 1 is used. Thus, the surface mount type piezoelectric component can be thinned.
[0018]
Further, the heat generated when the metal lid 12 is seam welded is radiated to the outside by the shell-shaped metal ring having a large surface area, and the heat is not directly transmitted to the ceramic substrate 1. Further, the pressure from the welding electrode is also reduced by the spring effect of the shell-shaped metal ring, and no pressure is directly applied to the ceramic substrate 1. For this reason, cracks are not generated in the ceramic substrate 1, and airtightness can be maintained. In other words, according to this embodiment, the package can be thinned while maintaining airtightness.
[0019]
In the above-described embodiment, the crystal resonator has been described as an example. However, the present invention is not limited to this, and other piezoelectric parts such as a crystal filter can be used. In addition, the shell described in the present specification refers to a shape in which a metal flat plate is formed by drawing. For example, as disclosed in JP-A-61-99374, airtightness for piezoelectric parts and connectors is used. Widely used for terminals. The shell-shaped metal ring in the present invention refers to an outer ring shape that is obtained by removing the central portion of the bottom surface of the shell described above.
[0020]
【The invention's effect】
As described above, according to the present invention, the vibration space of the piezoelectric element can be secured by using a single-layer ceramic substrate, so that the surface-mounted piezoelectric component can be thinned.
[0021]
In addition, by adopting a shell-shaped metal ring, the heat and pressure applied to the ceramic substrate during seam welding can be reduced, and the reliability of surface-mount type piezoelectric components can be maintained without cracking the ceramic substrate. can do. Furthermore, the amount of expensive metal material such as Kovar material used can be reduced compared to the metal ring, and the material cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a surface mount piezoelectric component according to an embodiment of the present invention;
FIG. 2A is a cross-sectional view of the surface-mounted piezoelectric component, FIG. 2B is a top view with a portion of the surface-mounted piezoelectric component omitted, and FIG. 2C is a bottom view of the surface-mounted piezoelectric component. Cross-sectional view of surface-mount type piezoelectric parts 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 Ceramic base | substrate 2 Piezoelectric element 3 Vibration space 4 Metallized layer 5 for electrodes Metallized layer 6 for input / output terminals Metallized layer 7 for earthing terminals Metallized layer 8 for joining Via hole 9, 10 Metal brazing material 11 Shell-shaped metal ring 12 Metal lid 13 Multilayer ceramic substrate 13a Lower stage 13b Middle stage 13c Upper stage 14 Conductive adhesive 15 Metal ring

Claims (1)

An electrode metallization layer is formed on the upper surface of the ceramic substrate, a piezoelectric element is held on the metal brazing material formed on the metallization layer for the electrode, and a shell is formed on the metallization layer for bonding formed around the upper surface of the ceramic substrate. A surface-mount type piezoelectric component characterized by brazing a metal-like metal ring and seam-welding a metal lid on the shell-like metal ring.

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