JPH09162323A - Ceramic package, surface mount piezoelectric oscillator and method for forming electrode of ceramic package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease joining strength of a metal member such as support, etc., and in variations in the joining strength by a method wherein a connection electrode is formed in a condition that its part is embedded in a ceramic package. SOLUTION: A ceramic substrate 1 serving as a ceramic package is composed of rectangular alumina, and an alumina coat 2 is provided near its outer periphery. Inwardly of the alumina coat 2, connection electrodes 3, 4 are provided. A part of the connection electrodes 3, 4 is embedded in the ceramic package and the connection electrodes 3, 4 are 20μm or more in a thickness. Further, pressing is used as a method for embedding a part of the connection electrodes 3, 4. Thereby, a joining face of the ceramic package to a metallized face is increased and joining strength between the ceramic package and a metallized face is enhanced, so that joining strength of a metal member being a substance to be joined is stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator, a piezoelectric single crystal oscillator, a piezoelectric ceramic oscillator or the like used as a reference oscillation source of communication equipment or a clock source of a microcomputer, and more particularly to mounting on a printed wiring board. The present invention relates to a method for forming electrodes of a ceramic package such as a surface-mounted piezoelectric vibrator in consideration of the above.

[0002]

2. Description of the Related Art A conventional technique will be described by taking a crystal oscillator as an example. A surface mount type crystal oscillator using a ceramic package is provided with connection electrodes on the upper surface of a ceramic substrate, and these connection electrodes have a structure in which, for example, tungsten is metallized and nickel plating and gold plating are performed on the upper surface. Then, a metal support is mounted on the connection electrode by a technique such as laser welding or spot welding, and a rectangular AT-cut crystal plate is mounted on the support, which is electrically connected by a conductive bonding material. Mechanically. Then, it was covered with a cap to hermetically seal it.

[0003]

However, when a support is mounted on the connection electrode of the ceramic substrate by laser welding, spot welding, or the like, the following causes are caused by the strength of the connection electrode and the variation in the thickness of the connection electrode. There was a problem. That is, since the thickness of the connection electrode on the ceramic substrate is thin (for example, 10 μm or less. This is because the thickness of the connection electrode when the metallization of the connection electrode is applied only once by screen printing and metal-plated is about 10 μm.
It's about. ), The bonding strength of the support, which is the bonded product, may be weakened, or the ceramic substrate, which is the bonded product, may be damaged or destroyed. On the contrary, by increasing the thickness of the connection electrode on the ceramic substrate (for example, 20 μm or more. This was screen-printed twice or more), the above-mentioned problem is solved, but the support on the upper surface of the connection electrode is solved. The flatness of the welded surface deteriorates and an uneven portion is formed (especially, the central portion is lower than the peripheral portion, and the height difference is about 10 μm). A gap is created between the connection electrode of the ceramic substrate, which is a joint, and a splash phenomenon occurs during welding, which causes variations in the joint strength of the support. This is because when forming a metallized electrode on the green sheet before firing,
The metallized electrode on the green sheet is thought to be caused by the gradual firing from the peripheral portion to the central portion, and it has been considered that it cannot be conventionally solved.

The present invention has been made in order to solve the above problems, and is a more reliable ceramic package that does not reduce the bonding strength of metal members such as supports and does not cause variations in the bonding strength, and An object of the present invention is to provide a surface mount type piezoelectric vibrator and an electrode forming method for a ceramic package.

[0005]

In order to solve the above problems, a ceramic package and a surface mount type piezoelectric vibrator according to the present invention have a structure in which a part of the connection electrode is embedded in the ceramic package to reduce the thickness of the connection electrode. It was set to 20 μm or more. The method is characterized in that the method of embedding a part of the connection electrode is performed by pressing.

By embedding a part of the connection electrode in the ceramic package, the number of joint surfaces between the ceramic package and the metallization is increased (increase in surface area),
The bonding strength between the ceramic package and the metallization (connection electrode) is improved, and the bonding strength of the metal member (support) which is the object to be bonded is also stable. By setting the thickness of the connection electrode to 20 μm or more, it is possible to improve the welding strength of the metal member (support) that is the object to be bonded, so that the bonding strength of the metal member (support) is also improved, and the bonding target It does not cause damage or destruction of certain ceramic packages.
By pressing, the adhesion at the interface between the ceramic package and the metallization can be improved, and the connection electrodes on the upper surface of the ceramic package can be smoothed, and variations in welding strength can be suppressed when mounting the subsequent metal member (support). . For the above reasons, the impact resistance of the ceramic package can be improved. Further, it is possible to stabilize the electrical characteristics of the piezoelectric vibrator and improve the impact resistance performance of the surface mount piezoelectric vibrator.

[0007]

Embodiments of the present invention will now be described with reference to the drawings, taking a surface mount type crystal resonator using a ceramic package as an example. 1 is an exploded perspective view showing an embodiment of the present invention, and FIG. 2 is a view showing a part of a manufacturing process of the present invention.

As shown in FIG. 1, a ceramic substrate 1 as a ceramic package is made of rectangular alumina, is processed into a thin plate, and has a notch on its side surface. Around the outer circumference of the ceramic substrate 1, for example, a circumferential alumina coat 2 having a thickness of about 30 μm is provided. Connection electrodes 3 and 4 are provided inside the alumina coat. Vias 3 for guiding these electrodes to the back surface of the ceramic substrate 1 are provided for the connection electrodes 3 and 4.
1, 41 (through holes are provided and filled with a metal electrode material). The vias 31 and 41 connect the connection electrodes 3 and 4 on the front surface to the back surface electrode (not shown). The connection electrodes and the back surface electrode have a structure in which, for example, tungsten is metallized, and the upper surface is plated with nickel and gold. For example, the thickness of the electrode is about 3
The thickness of 0 μm and the connection electrode are made equal to the film thickness of the alumina coat. And the supports 5 and 6 are Cu-Ni-
It is made of a metal plate such as a Zn-based alloy, nickel silver, or SUS, and has a substrate coupling portion 51, 61, an element mounting portion 52, 62, and a coupling portion 53,
And 63. 5, of this support
The substrate connecting portions 51 and 61 of 6 are electromechanically joined to the connecting electrodes 3 and 4 by, for example, laser welding or spot welding. In this way, the supports 5 and 6 are provided on the ceramic substrate 1 so as to face each other. Then, a rectangular AT-cut crystal plate 7 having an excitation electrode 71 (only the surface is shown) is formed.
Are mounted on the element mounting portions 52 and 62 of the supports 5 and 6, and electromechanical connection is performed by a conductive bonding material (not shown). The cap 8 is made of the same alumina as the ceramic substrate, is of a reverse concave type, and its outer peripheral dimension is designed to be equal to the dimension of the alumina coat, and the alumina coat and the cap are joined with a sealing glass (not shown). Is hermetically sealed by.

Next, a method of manufacturing the ceramic package of the surface mount type crystal resonator as described above will be described.
(See FIG. 2) (a) A green sheet (ceramic substrate) is produced by kneading a ceramic powder, which is a ceramic raw material, and a binder, and forming the mixture into a sheet. Then, a through hole is provided and a metal electrode material (for example, tungsten) is filled in the through hole to form a via. (B) After that, metallization which is a part of the connection electrode and the back surface electrode is formed in the vicinity of the via on the surface of the green sheet. This metallization is formed by mixing fine metal powder (for example, tungsten) with an organic binder and applying a paste-like material by screen printing or the like. (C) After that, in order to correct the flatness of the connection electrode portion among these metallizations, a press (a smooth press is particularly preferable) is performed. This smoothes the metallized green sheet by applying pressure from at least the upper direction. In this way, by flattening the metallization electrode of the connection electrode portion, the flatness (particularly, the central portion becomes lower than the peripheral portion) is always deteriorated when the thickness of the metallized electrode is increased to some extent. These are improved and the flatness becomes extremely good, and a part of metallization is embedded in the green sheet (ceramic substrate after firing). (D) Then, the green sheet on which the metallized electrode is formed is cut into a desired size and fired in, for example, humidified hydrogen or humidified forming gas (telefunken method) to mechanically bond the ceramic substrate and the metallized electrode. . (E) Then, at least the connection electrode portion of the metallized electrode is plated with nickel and gold.

The metallization electrode is not limited to tungsten, but molybdenum, Mo-Mn, and Mo-Mn can be used as T.
It may have a configuration in which i, Zr, Fe or SiO ₂ , CaO or the like is added. Further, the metal plating may be one using nickel kovar instead of nickel, and one using silver, copper or silver palladium instead of gold.
Further, the method of embedding a part of the connection electrode is not limited to the smooth press, and other press forms may be used, and a recess may be formed in the area of the connection electrode of the ceramic substrate in advance, and the recess may be filled with metallization. Good.

In the embodiment of the present invention, only the surface mount type crystal resonator is used as an example. However, the same package can be used for the piezoelectric single crystal resonator and the piezoelectric ceramic resonator. it can. Further, it can be diverted to a surface mount type crystal filter and can be applied to a crystal oscillator or the like. That is, it is possible to apply it to any electronic component having a structure in which a metal member such as a support is welded onto the connection electrode and the element is mounted on the metal member.
Further, in the embodiment of the present invention, the glass-sealed ceramic package has been described, but it goes without saying that the invention can be applied to a seam-sealed package.

[0012]

According to the present invention, it is possible to provide a highly reliable ceramic package in which the bonding strength between the connecting electrode and the ceramic package is improved, and to stabilize the electric characteristics of the piezoelectric vibrator, and to provide a surface mount type piezoelectric vibrator. It is possible to provide a highly reliable surface mount type piezoelectric vibrator capable of improving the impact resistance performance and a method for forming an electrode of a ceramic package for a piezoelectric vibrator.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a part of the manufacturing process of the present invention.

[Explanation of symbols] 1 ceramic substrate 2 alumina coat 3,4 connection electrode 5,6 support 7 crystal plate 8 cap

Claims (5)

[Claims] 1. A ceramic package having a connection electrode formed by welding a metal member, wherein the connection electrode is partially embedded in the ceramic package. . 2. A surface mount type piezoelectric vibrator comprising a ceramic package having a connection electrode, a support member welded to the connection electrode of the ceramic package, a piezoelectric vibrating plate, and a lid for sealing. , Connecting electrodes and lead-out electrodes are formed on the ceramic package, and at least the connecting electrodes are formed by metal plating on the metallization, and a part of the metallization is embedded in the ceramic package. A surface-mounted piezoelectric vibrator characterized by being used. 3. A ceramic package or a surface mount type piezoelectric vibrator, wherein at least a thickness of a connection electrode is at least 20 μm or more. 4. The surface mount piezoelectric vibrator according to claim 1 or 2, wherein at least the thickness of the connection electrode is at least 20 μm or more. 5. A step of forming a green sheet by forming a ceramic raw material and a binder into a sheet shape, and a step of forming a metallization which is a part of a connecting electrode and a lead electrode on the surface of the green sheet, A method for forming an electrode of a ceramic package, comprising: a step of pressing a metallization; a step of cutting the green sheet having the metallization formed into a desired size and firing; and a step of forming a metal plating on the metallization.