JPH0619316U - Surface mount piezoelectric resonator - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a surface-mounted piezoelectric resonator that has improved heat resistance and excellent vibration resistance and impact resistance. [Structure] A ceramic plate-shaped base 21, a mounting electrode 22 formed on the bottom surface of the base, a holding electrode 23 formed on the upper surface of the base so as to be electrically connected to the mounting electrode,
A holding member 24 which is pressed against the holding electrodes by a pair of welding electrodes 27 having a minute gap to energize and weld between the welding electrodes,
It comprises a piezoelectric piece 25 held by this holding member, and a bottomed box-shaped cover 26 which covers the upper surface of the base and hermetically fixes the opening to the plate surface of the base.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surface-mounted piezoelectric resonator, and more particularly to improvement of a piezoelectric piece holding structure.

[0002]

[Prior art]

 Recently, piezoelectric resonators are widely used as a reference for frequency, time, etc. in various electronic devices. In particular, quartz oscillators that use quartz as a piezoelectric body are used in large quantities because they have excellent chemical and physical properties, and in addition to advances in manufacturing technology, they are inexpensive and have high performance. Conventionally, as such a crystal oscillator, one having a structure as shown in FIG. 4, for example, is known. That is, a thin metal plate such as Kovar is press-molded to obtain an oval base 1. Then, two terminals 2 are inserted into the base 1 and filled with an insulating material such as molten glass to insulate and hold each other. Then, the base end of a holding member 3 having a spring property such as a piano wire is wound around and fixed to the tip of the terminal 2, and the clip 4 is formed at the tip. Then, the crystal piece 5 is inserted between the facing surfaces of the holding member 3, the peripheral portion thereof is held by the clip 4, and a conductive adhesive is applied to fix the quartz piece 5. The base 1 is covered with a bottomed tubular cover 6 having an oval cross section, and the opening edge of the cover 6 is hermetically sealed to the base 1 by resistance welding or the like. The crystal piece 5 is formed into a plate by cutting a crystal of quartz at a predetermined angle with respect to the crystal axis. Then, electrodes are formed on the front and back plate surfaces by vapor deposition or the like, and the electrodes are led out to both ends, respectively, and the lead-out ends are sandwiched by the clips 4 and electrically connected to the terminals 2.

However, in recent years, it has been desired to reduce the size and weight of electronic devices and automate the assembly process. For this reason, there is a tendency for electronic parts such as resistors, capacitors and integrated circuits to be of the surface mount type without lead terminals. When assembling electronic equipment using surface-mounting electronic components like this, for example, apply cream solder, etc. to the parts to be soldered, and use an automatic machine such as a chip mounter to place all components at the prescribed positions on the printed circuit board. To place. Then, there is a method in which the printed circuit board is passed through a tunnel furnace or the like to heat and melt the solder, thereby collectively performing the component mounting work in a short time. In the assembly of electronic equipment using such surface-mounted electronic components, lead holes are drilled at specified positions on the printed circuit board, and the lead terminals of the components are inserted and soldered as before. It can be automated more easily and can be smaller in size and lighter in weight than those mounted by using the same method. For this reason, piezoelectric vibrators used for such electronic devices are also desired to be surface-mounted type without lead terminals. FIG. 5 is an assembled perspective view showing an example of such a surface-mounted piezoelectric vibrator. A mounting electrode (not shown) is formed on the bottom surface of a plate-shaped ceramic base 11, and this mounting electrode is used as a conductive pattern of a printed circuit board. It is soldered to and mounted. Then, the holding electrode is formed on the upper surface of the base 11 by being electrically connected to the mounting electrode. Then, a pair of holding members 12 formed by molding a thin metal plate are fixed to the above-mentioned holding electrodes by a conductive adhesive having a good heat resistance, for example, a polyimide-based adhesive, and electrical conduction is achieved. Then, the piezoelectric piece 13 is placed on the holding member 12, and a conductive adhesive or the like is applied and held. The piezoelectric piece 13 is formed, for example, by cutting a crystal of artificial quartz at a predetermined angle with respect to the crystal axis to form a plate, and forming an electrode on the plate surface. Then, the opening of the bottomed box-shaped cover 14 is fixed to the plate surface of the base 11 with molten glass, an adhesive or the like to hermetically seal. However, in such a structure, an adhesive is used to fix the holding member 12 to the base 11. For this reason, sufficient mechanical strength could not be obtained, and the holding member 12 sometimes came off the base 11 when violent vibration, impact, etc. acted from the outside. In addition, this kind of adhesive also has insufficient heat resistance, and it was necessary to severely limit the heating conditions when soldering the mounting electrodes when mounting on a printed circuit board or the like. Further, this type of conductive adhesive generates gas when it is heated to a high temperature when it is mounted on a printed circuit board, and this component adheres to the surface of the piezoelectric piece 13 and remarkably impairs resonance characteristics. There was a problem of deterioration.

[0004]

[Problems to be solved by the device]

 The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a surface-mounted piezoelectric resonator which has improved heat resistance and excellent vibration and shock resistance characteristics.

[0005]

[Means for Solving the Problems]

 According to the present invention, a ceramic plate-shaped base, a mounting electrode formed on the bottom surface of the base, a holding electrode formed on the upper surface of the base so as to be electrically connected to the mounting electrode, and a small gap formed on the holding electrode. A holding member pressed by a pair of welding electrodes and energized and welded between the welding electrodes, a piezoelectric piece held by this holding member, and an opening that covers the upper surface of the base to hermetically fix the opening to the plate surface of the base. It has a bottomed box-shaped cover.

[0006]

【Example】

 Hereinafter, an embodiment of the present invention will be described in detail with reference to an assembled perspective view shown in FIG. 1 and a side sectional view shown in FIG. Reference numeral 21 in the figure denotes a ceramic base having a thickness of 1.0 mm and a size of 12.0 mm × 5.5 mm, for example. The mounting electrode 22 is formed on the bottom surface of the base 21. The mounting electrode 22 is, for example, a metal thin film formed by a metallizing process. A holding electrode 23 is formed on the upper surface of the base 21. This holding electrode 23 is also a metal thin film formed by, for example, a metallizing process. Each of the electrodes 22 and 23 may be formed by embedding a thin metal plate in a predetermined shape, for example. A holding member 24 formed by molding a thin metal plate having a thickness of about 0.05 mm into a predetermined shape is welded to the holding electrode 23 by parallel welding at one end thereof. The holding member 24 is provided on the base 24a to be welded to the holding electrode 23, two arms 24b extending in parallel from the base 24a, and the tips of the two arms 24b. A holding portion 24c formed by folding back the portion and a stopper 24d formed by further cutting and raising the outer edge of the holding portion 24c are provided. Then, the piezoelectric piece 25 is placed on the holding portion 24c of the holding member 24, and a conductive adhesive is applied to hold it mechanically and to achieve electrical continuity. At this time, the piezoelectric piece 25 can be accurately and easily positioned at a predetermined position by the stopper 24d. Then, a bottomed box-shaped cover 26 is covered on the upper surface of the base 21, and the opening of the cover 26 is airtightly fixed to the plate surface of the base 21 by using an adhesive, molten glass or the like. In the above-mentioned parallel welding, for example, as shown in FIG. 3, the base portion 24a of the holding member 24 is pressed against the holding electrode 23 by a pair of welding electrodes 27 having a minute gap so as to be in close contact with each other. A large current is applied to the base 24a to weld it to the holding electrode 23.

With such a structure, the holding member 24 made of a thin metal plate is folded back in two by the arm portion 24b, one of the base portions 24a is welded to the holding electrode 23, and the other holding portion 24c is formed. The piezoelectric piece 25 is mounted. Therefore, since the arm portion 24b can be narrow and long, the elasticity of the member can be fully utilized. Therefore, mechanical strain does not occur when the conductive adhesive is applied and solidified to hold the piezoelectric piece 25 by the holding member 24. Since the piezoelectric member 25 is held by the holding member 24 having high elasticity, the piezoelectric member 25 is not damaged or changed in characteristics due to external vibration, impact, etc., and has good resonance characteristics. Can be obtained. Since the holding member 24 is welded to the holding electrode 23 by parallel welding, its mechanical strength is about twice as high as that using an adhesive, and even if it is heated during mounting, it does not generate gas. Good aging characteristics can be obtained without any generation.

[0008]

[Effect of device]

 As described in detail above, according to the present invention, it is possible to provide a surface-mounted piezoelectric resonator that has good vibration resistance and shock resistance, is suitable for mass production, and has a small shape.

[0009]

[Brief description of drawings]

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

FIG. 2 is a side sectional view of the embodiment shown in FIG.

FIG. 3 is a side view for explaining parallel welding of the embodiment shown in FIG.

FIG. 4 is an assembled perspective view showing an example of a conventional crystal resonator.

FIG. 5 is an assembled perspective view showing an example of a conventional surface mount type crystal unit.

[Explanation of symbols]

 21 Base 22 Mounting Electrode 23 Holding Electrode 24 Holding Member 24a Base 24b Arm 24c Holding 24d Stopper 25 Piezoelectric Piece 26 Cover 27 Welding Electrode

Claims (1)

[Scope of utility model registration request] 1. A ceramic plate-shaped base, a mounting electrode formed on the bottom surface of the base, a holding electrode formed on the upper surface of the base so as to be electrically connected to the mounting electrode, and a minute gap in the holding electrode. A holding member pressed by a pair of welding electrodes and energized and welded between the welding electrodes; a piezoelectric piece held by this holding member; and an opening that is covered on the upper surface of the base to hermetically fix the opening to the plate surface of the base. 1. A surface-mounted piezoelectric resonator comprising: a bottomed box-shaped cover described above.