PIEZOELECTRIC CERAMIC RESONATOR AND FABRICATION METHOD THEREOF

Abstract: The invention relates to a piezoelectric ceramic resonator and manufacturing method thereof. More particularly, the invention relates to a piezoelectric ceramic resonator comprising a piezoelectric ceramic body (21) having an upper surface and a lower surface facing opposite with each other, and side surfaces connecting said upper surface and said lower surface; a first electrode and a second electrode each of which has integrally formed long and short electrode films; and a plurality of lead pins (30), one end (32) of each said lead pin is connected to either of said electrodes, wherein said long electrode film of said first electrode contacts said upper surface of said piezoelectric ceramic body and said short electrode film of said first electrode contacts one side surface of said piezoelectric ceramic body, and said long electrode film of said second electrode contacts said lower surface of said piezoelectric ceramic body and said short electrode film of said second electrode contacts the other side surface of said piezoelectric ceramic body; said long electrode film of said first electrode is separated from said short electrode film of said second electrode by a predetermined spacing, and said short electrode film of said first electrode is separated from said long electrode film of said second electrode by a predetermined spacing; and said long electrode film of said first electrode and said long electrode film of said second electrode have portions opposite with each other with said piezoelectric ceramic body between them.

Description: PIEZOELECTRIC CERAMIC RESONATOR AND FABRICATION METHOD THEREOF BACKGROUND OF THE INVENTION The types of resonators useful in electronics applications include LC and RC resonators, quartz-crystal resonators, and piezoelectric ceramic resonators. Each type has a limited range of operating frequencies: the operating frequencies of of LC and RC resonators range from about 100 Hz to about 150 MHZ, those of quartz resonators range from about 3 kHz to about 200 MHZ,, and those of. piezoelectric ceramic resonators range from about 10 kHz to about 100 MHZ. Piezoelectric ceramic resonators, which were invented in 1978, have undergone rapid development due to the explosive growth of the market for integrated circuits. Piezoelectric ceramic resonators are widely used in oscillators which provide reference signal (clock) for one-chip microcomputers, and in electronic parts for an automobile, copiers, facsimiles, printers, phones, video tape recorders, televisions, home appliances and toys. Piezoelectric ceramic resonators use the advantage of the characteristic of the included piezoelectric body that when an alternating voltage is applied to the body, the body is resonated at a certain frequency. Resonating modes for the piezoelectric body includes area oscillating mode, thickness oscillating mode, and thickness twisting oscillating mode, etc. The area oscillating modes are typically used for resonators having resonating frequencies from a few tens of kHz to a few MHZ, while the thickness oscillating modes and thickness twisting oscillating modes are used for resonators having resonating frequencies of more than a few MHZ. One advantage of piezoelectric ceramic resonators over other types of resonators is their highly stable oscillating frequency. Piezoelectric ceramic resonators have a Q value intermediate between those of quartz-crystal resonators and LC or RC resonators. The oscillating frequency temperature coefficient when constructing an oscillating circuit with a piezoelectric ceramic resonator has a stability of about the order of 10 "5 /°C( +30 ppm/deg) in the temperature range of -20 to 80°C. Piezoelectric ceramic resonators are also compact and light. An typical example of currently available piezoelectric ceramic resonators has an width of about 10 mm, a height of about 10 mm, and a thickness of about 3.5 mm. The overall dimensions of the typical piezoelectric ceramic resonator is only about half that of a corresponding quartz-crystal resonator. Finally, since tuning of an oscillating circuit with a piezoelectric ceramic resonator is not necessary, piezoelectric ceramic resonators are suitable for mass production: they are easy and inexpensive to manufacture. In addition, the resonating frequency of a piezoelectric ceramic resonator is determined in the manufacturing stage and thus, volumes for tuning, trimmers and condensers are not necessary when in use. The thickness oscillating mode and the thickness twisting oscillating mode use the oscillation in the thickness direction of the piezoelectric ceramic resonator. Therefore, the oscillating frequency depends on the thickness of a piezoelectric ceramic resonator. The thickness oscillating mode and the thickness twisting oscillating mode use an energy closing effect resulting from an oscillation generated by superimposed portions of electrodes formed on certain portions of a piezoelectric ceramic resonator. Since oscillation occurs only at certain portions of the piezoelectric ceramic resonator in the thickness oscillating mode and the thickness twisting oscillating mode, it is important to form a void around the oscillating portions when packaging the piezoelectric ceramic resonator so that the oscillation is not constrained. In order to form the void inside the piezoelectric ceramic resonator, both ends of the piezoelectric ceramic resonator 1 is held by lead pins 2 as shown in Figure la. Then, as shown in Figures lb and lc, a wax having a low melting point is applied to the piezoelectric ceramic resonator. Then, as shown in Figure Id, the exterior surface of the piezoelectric ceramic resonator 1 with lead pins 2 connected thereto is coated with a porous resin 8 and cured. Then, as shown in Figure le, the resonator is heated under vacuum so that the wax inside the resonator is eliminated and a void for oscillation is formed inside the resonator. As shown in Figures 2a through 2e, a prior art piezoelectric ceramic body has electrode films 3 and 4 which are disposed on the body's upper and lower surfaces, respectively. Portions of the electrode films are superposed on the ceramic body disposed between the films. Each electrode film is electrically connected to a lead pin 2 or 10 at either end of the ceramic body. The surfaces of the body except the upper surface and the lower surface do not have electrode films. Therefore, as shown in Figure 2e, lead pins each of which has two branches 11 or 12 are needed to electrically connect the electrode 3 on the upper surface of the ceramic body and the electrode 4 on the lower surface of the ceramic body which corresponds to the electrode 3. Examples of such lead pins 2, 10 are shown in Figures 2c and 2d, respectively. These lead pins are manufactured by press working of metal plates with press dies. Conventionally, a ceramic body is inserted between the branches 11, 12 of lead pins 2, 10. Then, the branches are squeezed to temporarily fix the body 1 and the lead pins 2, 10. Then, the body and the branches of the lead pins are assembled by forming soldered portions 9 shown in Figure la. This method requires complex procedures and a precision of high degree. Specifically, inserting the body into the space between the branches is a very precise mechanical procedure. Therefore, yield is low unless the level of automatic production facilities meet a certain standard and improving the level has its own limit. In addition, the prior art requires lead pins 2, 10 having complex shapes. Such lead pins are manufactured by metal stamping. This procedure is costly because large amount of material is needed to make the lead pins and precise metal press dies must be used. Therefore, an object of the invention is to provide a piezoelectric ceramic resonator employing lead pins of simple shape, which enable reduced costs of manufacture and assembly and improves manufacturing yield by simplifying the assembly of lead pins and ceramic bodies. The above and other objects can be accomplished by providing a piezoelectric ceramic resonator comprising a piezoelectric ceramic body having an upper surface and a lower surface facing opposite with each other, and side surfaces connecting the upper surface and the lower surface, a first electrode and a second electrode each of which has integrally formed long and short electrode films, and a plurality of lead pins, one end of each lead pin is connected to either of said electrodes. The long electrode film of the first electrode contacts the upper surface of the piezoelectric ceramic body and the short electrode film of the first electrode contacts one side surface of the piezoelectric ceramic body, and the long electrode film of the second electrode contacts the lower surface of the piezoelectric ceramic body and the short electrode film of the second electrode contacts the other side surface of the piezoelectric ceramic body. The long electrode film of the first electrode is separated from the short electrode film of the second electrode by a predetermined spacing, and the short electrode film of the first electrode is separated from the long electrode film of the second electrode by a predetermined spacing. The long electrode film of the first electrode and the long electrode film of the second electrode have portions opposite with each other with the piezoelectric ceramic body between them. Preferably, the short electrode film of the first electrode extends to the lower surface of the piezoelectric ceramic body, and the short electrode film of the second electrode extends to the upper surface of the piezoelectric ceramic body. An embodiment of the present invention provides a piezoelectric ceramic resonator comprising a piezoelectric ceramic body having an upper surface and a lower surface facing opposite with each other, a first electrode contacting the upper surface of the piezoelectric ceramic body, a second electrode contacting the lower surface of the piezoelectric ceramic body, and a plurality of lead pins, one end of each lead pin being connected to either of the electrodes, wherein the first electrode and the second electrode have portions opposite with each other with the piezoelectric ceramic body between them. Preferably, the lead pins have a shape of wires, and the lead pins have flat portions which are electrically connected to the electrodes. In addition, the piezoelectric ceramic resonator of the present invention may comprise an integral condenser. An embodiment of the present invention provides a method of fabricating a piezoelectric ceramic resonator, the method comprising the steps of: preparing a piezoelectric ceramic body having an upper surface and a lower surface facing opposite with each other, and side surfaces connecting the upper surface and the lower surface; installing first and second electrodes on the piezoelectric ceramic body, each of the first electrode and the second electrode having integrally formed long and short electrode films; the long electrode film of the first electrode contacting the upper surface of the piezoelectric ceramic body and the short electrode film of the first electrode contacting one side surface of the piezoelectric ceramic body, and the long electrode film of the second electrode contacting the lower surface of the piezoelectric ceramic body and the short electrode film of the second electrode contacting the other side surface of the piezoelectric ceramic body; the long electrode film of the first electrode being separated from the short electrode film of the second electrode by a predetermined spacing, and the short electrode film of the first electrode being separated from the long electrode film of the second electrode by a predetermined spacing; and the long electrode film of the first electrode and the long electrode film of the second electrode having portions opposite with each other with the piezoelectric ceramic body between them; fixing one ends of lead pins, which are wires cut by a predetermined length, on a tape parallel with one another and with a constant spacing; applying solder paste on the other ends of the lead pins which are not fixed on the tape; attaching the lower surface of the ceramic body on the ends of the lead pins in order to electrically connect two adjacent lead 30, on which solder paste has been applied, to the first and second electrodes; reflow curing the solder paste by heat treating the ceramic bodies and the lead pins; applying wax on portions of the electrodes corresponding to the middle portion of the ceramic body; coating the ceramic body with a porous resin layer; eliminating the wax by heating the ceramic body; and coating an air-tight resin layer on the porous resin layer. An embodiment of the present invention also provides a method of fabricating a piezoelectric ceramic resonator. The method comprises the steps of : installing the first and second electrodes on the piezoelectric ceramic body; fixing one ends of the lead pins, which are wires cut by a predetermined length, on a tape parallel with one another and with a constant spacing; applying solder paste on the other ends of the lead pins which are not fixed on the tape; attaching the lower surface of the ceramic body on the ends of two adjacent lead pins on which solder paste has been applied, in order to electrically disconnect one of the two ends to the second electrode and to electrically connect the other of the two ends to the second electrode; applying solder paste on the portion of the ceramic body at which the lead pins attached in order to electrically connect the end of the lead pin which are not electrically connected to the second electrode to the first electrode on the upper surface; reflow curing the solder paste by heat treating the ceramic bodies and the lead pins; applying wax on portions of the electrodes corresponding to the middle portions of the upper surface and the lower surface of the ceramic body; coating the ceramic body with a porous resin layer; eliminating the wax by heating the ceramic body; and coating an air-tight resin layer on the porous resin layer. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is embodied in greater detail by means of the accompanying drawings, wherein: Figures la - If are schematic drawings showing a packaging process of a prior art piezoelectric ceramic resonator. Figure la is a perspective view showing a piezoelectric ceramic body with two lead pins soldered thereto. Figure lb is a perspective view showing the process of applying wax on the superposed portions of electrode films positioned on the upper surface and the lower surface of the piezoelectric ceramic body. Figure lc is a perspective view showing a vibrating portion of the piezoelectric ceramic body covered with wax. Figure Id is a perspective view showing the state of the piezoelectric ceramic body coated with a porous resin after wax is applied. Figure le is a perspective view showing a process of eliminating wax by heating the wax under vacuum to allow the evaporated wax to exit through the porous resin. Figure If is a perspective view showing the state that the piezoelectric ceramic body with a void around the vibrating portion of the body formed by wax elimination is isolated from the surroundings by coating the outer surface of the porous resin with a sealing paint. Figures 2a - 2e show configurations of lead pins and a piezoelectric ceramic body of a conventional piezoelectric ceramic resonator. Figure 2a is a perspective view of a conventional piezoelectric ceramic body viewed from above. Figure 2b is a perspective view of the conventional piezoelectric ceramic body of Fig. 2a viewed from below. Figures 2c and 2d are perspective views of the conventional piezoelectric ceramic body of Fig. 2a showing two types of lead pins. Figure 2e is a sectional view of the conventional piezoelectric ceramic body of Fig. 2a showing the assembled state of the piezoelectric ceramic body and the lead pins.. Figure 3a is a perspective view of the piezoelectric ceramic body according to an embodiment of the present invention viewed from above. Figure 3b is a perspective view of the piezoelectric ceramic body of Fig. 3a viewed from below. Figure 3c is a perspective view of the piezoelectric ceramic body of Fig. 3a showing lead pins made of wire. Figure 3d is a perspective view of the piezoelectric ceramic body of Fig. 3a showing the piezoelectric ceramic body with two lead pins soldered thereto. Figure 3e is a perspective view of the piezoelectric ceramic body of Fig. 3a showing a resonator having an integral condenser. Figure 4 is a sectional view of a piezoelectric ceramic body according to an embodiment of the present invention. Figure 5 is a sectional view of a complete piezoelectric ceramic resonator according to an embodiment of the present invention. Figure 6 is a sectional view of a complete piezoelectric ceramic resonator having an integral condenser according to an embodiment of the present invention. Figure 7 is a schematic drawing showing lead wires fixed on a tape with a constant spacing. Figure 8 is a sectional view of a piezoelectric ceramic resonator according to a embodiment of the present invention. Figures 9a - 9d are drawings illustrating process steps of fabricating a piezoelectric ceramic resonator according to another embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figures 3a, 3b and 4 show a piezoelectric ceramic body 21 according to the invention. The body 21 is substantially a parallelepiped having an upper surface, a lower surface, end surfaces and side surfaces. A long electrode film 22 and a short electrode film 23 are formed on the upper surface of the body 21 with a predetermined spacing between them. Similarly, a long electrode film 25 and a short electrode film 26 are formed on the lower surface with a predetermined spacing between them. The long electrode film 22 on the upper surface and the long electrode film 25 on the lower surface are disposed opposite on the longitudinally middle portions of the ceramic body with the ceramic body between them for oscillation of the ceramic body 21. An electrode film 27 electrically connecting the long electrode film 22 on the upper surface and the short electrode film 26 on the lower surface, and an electrode film 24 electrically connecting the short electrode film 23 on the upper surface and the long electrode film 25 on the lower surface are formed on the end surfaces of the ceramic body. That is, the electrode structure of the piezoelectric ceramic resonator according to the invention is, as shown in Figure 4, a structure in which electrodes on the upper surface and on the lower surface face each other on the middle portion of the ceramic body for oscillation of the piezoelectric ceramic body; the electrodes are insulated from each other; and each electrode extends on the opposite surface through the end surface of the ceramic body. Figure 3d shows that the lead pins 30 are soldered to the ends 32 of the lower surface of the piezoelectric ceramic body so that they are electrically connected to the electrode films 25, 26. It can be seen that the lead pins are connected on the ends of a common surface while maintaining the function same as the prior art. By the above construction of electrodes, it is possible to eliminate the need of lead pins having branches of complex shape as in the prior art, and to use lead pins of a simple shape as shown in Figure 3c. This simple shape makes it possible to manufacture lead pins by simply cutting lead wires without complex procedures of press working metal plates. Preferably, the lead pins 30 made of lead wires have flat tips 31 which are worked to be flat for stable connection with the electrode films 25, 26 of the ceramic body 21, as shown in Figure 3c. Figure 3e shows a piezoelectric ceramic resonator including an integral condenser. The integral condenser type resonator includes the piezoelectric ceramic body 21, a dielectric body 33, lead pins 30 soldered between the ceramic body and the dielectric body, and a lead pin attached to the lower surface of the dielectric body. In this way, the present invention enables easy manufacturing of a product having 3 lead pins and an advantage of not requiring a separate condenser for oscillation when making a electronic circuit. Manufacturing method of the piezoelectric ceramic resonator according to the invention includes the following steps. (a) Electrode films are formed on a piezoelectric ceramic body. (b) Lead pins 30 are fixed on a board 40 with tape 41 by an automatic fixing device (not shown). The lead pins 30 are placed parallel with a constant spacing as shown in Figure 7. For the automatic fixing device, a device for attaching lead wires, which is used for attaching lead wires on film condensers, may be used. The device provides enough positional precision required for soldering the lead pins to the ceramic body. (c) The board 40 on which the lead pins has been fixed is moved. An automatic device applies solder paste on the flat tips 31 of the lead pins 30. (d) The ceramic body is placed on the flat tips 31 of two adjacent lead pins 30 on which solder paste has been applied. (e) The board 40 together with the ceramic bodies and the lead pins are entered into a reflow heat treatment furnace to cure the solder paste thereby fixing the ceramic bodies and the lead pins. (f) Wax 7 is applied on the middle portion of the ceramic body 21. Then the entire exterior of the ceramic body is coated with a porous resin to form a porous resin layer 8. (g) After the porous resin layer 8 is hardened, the wax 7 is eliminated by heating the ceramic body in a vacuum oven. (h) An air tight layer 13 is formed by coating the exterior surface of the porous resin layer 8 with epoxy resin. Figure 5 shows the cross-section of the piezoelectric ceramic resonator made by the above method. Figure 6 shows the cross-section of the piezoelectric ceramic resonator with integral condenser. Figure 8 shows the cross-section of a piezoelectric ceramic resonator according to a variant of the invention. The piezoelectric ceramic body 51 shown in Figure 8 differs from the piezoelectric ceramic body 21 shown in Figure 4 in that the body 51 does not have the short electrode film 23 on the upper surface and the short electrode film 26 on the lower surface. Precise adjusting of the position of the lead pins 30 relative to the ceramic body 51 and the applying position of the solder paste makes it possible to solder the lead pins with the electrode films 24, 27 on the end surfaces of the body without the short electrode films 23, 26. Preferably, the position of the lead pins 30 are adjusted so that the tips 31 are aligned with the end surfaces of the piezoelectric ceramic body 41, or as shown in Figure 8, the tips 31 protrudes slightly beyond the end surface, and thus, melted solder is easily moved to the electrode films 24, 27 on the end surfaces of the ceramic body to wet the electrode films, thereby soldering the electrode films 24, 27 with the tips 31 of the lead pins 30 is facilitated. Figure 8 shows that the electrode films 24, 27 and the tips 31 are soldered together. Although figure 8 shows that the electrode films 24, 27 are attached to the end surfaces of the piezoelectric ceramic body 51, they can be attached to the side surfaces of the body 51. Figures 9a - 9d show the cross-section of a piezoelectric ceramic resonator according to another variant of the invention and manufacturing steps for the resonator. This variant uses the piezoelectric ceramic body of the prior art shown in Figures 2a and 2b. Such arrangement is possible by adding a second applying step of solder paste on the portion of the ceramic body at which the lead pins are attached after the step (d) of placing the ceramic body on the lead pins and before the step (e) of fixing the ceramic body and the lead pins. Figure 9a shows the step of first applying of solder paste on the flat tips 31 of the lead pins 30. Figure 9b shows the step of placing the ceramic body 1 on the solder paste applied on the flat tips 31 of two adjacent lead pins 30. Figure 9c shows the step of second applying solder paste on the portion of the ceramic body at which the flat tips 31 of the lead pins are attached. Figure 9d shows the ceramic body 1 and the flat tips 31 of the lead pins 30 which have been fixed by curing the solder paste in a reflow treatment furnace. In this variant also, it is preferable that the position of the lead pins 30 relative to the piezoelectric ceramic body 1 and the applying position of solder paste are adjusted precisely, and that the tips 31 are aligned with the end surfaces of the piezoelectric ceramic body 1, or the tips 31 protrudes slightly beyond the end surface of the body. < Example > A ceramic body made of PZT[Pb(ZrTi)O 3 ] and having a length of 8 mm, a width of 1 mm, and a thickness of 0.28 mm was prepared, and electrode films were attached on the body as shown in Figures 3a, 3b and 4. Lead pins were made from 0.55 mm diameter lead wires, and connecting portions of the lead pins were worked to be flat as shown in Figure 3c. The lead pins 30 and the ceramic body 21 were soldered to be electrically connected together, as shown in Figure 3d. After soldering, wax was applied on the oppositely superposed portions of the electrode films as shown in Figures lb and lc, and then a porous resin layer was formed with phenol epoxy resin as shown in Figure Id. Then the body was kept at 120°C under vacuum for 20 minutes to eliminate the wax inside. After eliminating the wax completely, as shown in Figure If, the exterior surface of the ceramic body was coated with thick epoxy resin to isolate the ceramic body from the surroundings, and a piezoelectric ceramic resonator having a resonating frequency of 4.0 MHz was obtained. The piezoelectric ceramic resonator according to the invention has the following advantages: The present invention solves the problems of difficulties in assembling and corresponding reduction of the yield when a piezoelectric ceramic resonator employ lead pins made by press working from metal plates. It is possible to reduce manufacturing cost because lead pins made from wires are cheaper than lead pins made from metal plates by press working. The piezoelectric ceramic resonator according to the present invention simplifies assembling and thus improves the yield. It is possible to manufacture lead pins at 20% of the cost in the prior art. In the prior art, the cost of lead pins covers about 50% of the entire material cost. It will be understood that the invention may be modified in other specific forms without departing from the spirit or central characteristics thereof. The present example and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.

Claims: We claim: 1. A piezoelectric ceramic resonator comprising: a piezoelectric ceramic body having an upper surface and a lower surface facing opposite with each other, and side surfaces connecting said upper surface and said lower surface; a first electrode and a second electrode each of which has integrally formed long and short electrode films; and a plurality of lead pins, one end of each said lead pin is connected to either of said electrodes, wherein said long electrode film of said first electrode contacts said upper surface of said piezoelectric ceramic body and said short electrode film of said first electrode contacts one side surface of said piezoelectric ceramic body, and said long electrode film of said second electrode contacts said lower surface of said piezoelectric ceramic body and said short electrode film of said second electrode contacts the other side surface of said piezoelectric ceramic body; said long electrode film of said first electrode is separated from said short electrode film of said second electrode by a predetermined spacing, and said short electrode film of said first electrode is separated from said long electrode film of said second electrode by a predetermined spacing; and said long electrode film of said first electrode and said long electrode film of said second electrode have portions opposite with each other with said piezoelectric ceramic body between them. 2. The piezoelectric ceramic resonator according to Claim 1, wherein said short electrode film of said first electrode extends to said lower surface of said piezoelectric ceramic body, and said short electrode film of said second electrode extends to said upper surface of said piezoelectric ceramic body. 3. The piezoelectric ceramic resonator according to Claim 1 or Claim 2, wherein said lead pins have a shape of wires. 4. The piezoelectric ceramic resonator according to Claim 3, wherein said lead pins have flat portions which are electrically connected to said electrodes. 5. The piezoelectric ceramic resonator according to any one of Claims 1, 2, and 4, wherein said piezoelectric ceramic resonator further comprises an integral condenser. 6. A method of fabricating a piezoelectric ceramic resonator, the method comprising the steps of: preparing a piezoelectric ceramic body having an upper surface and a lower surface facing opposite with each other, and side surfaces connecting said upper surface and said lower surface; installing first and second electrodes on the piezoelectric ceramic body, each of said first electrode and said second electrode having integrally formed long and short electrode films; said long electrode film of said first electrode contacting said upper surface of said piezoelectric ceramic body and said short electrode film of said first electrode contacting one side surface of said piezoelectric ceramic body, and said long electrode film of said second electrode contacting said lower surface of said piezoelectric ceramic body and said short electrode film of said second electrode contacting the other side surface of said piezoelectric ceramic body; said long electrode film of said first electrode being separated from said short electrode film of said second electrode by a predetermined spacing, and said short electrode film of said first electrode being separated from said long electrode film of said second electrode by a predetermined spacing; and said long electrode film of said first electrode and said long electrode film of said second electrode having portions opposite with each other with said piezoelectric ceramic body between them; fixing one ends of lead pins, which are wires cut by a predetermined length, on a tape parallel with one another and with a constant spacing; applying solder paste on the other ends of said lead pins which are not fixed on said tape; attaching said lower surface of said ceramic body on said ends of said lead pins in order to electrically connect two adjacent lead pins, on which solder paste has been applied, to said first and second electrodes; reflow curing said solder paste by heat treating said ceramic bodies and said lead pins; applying wax on portions of said electrodes corresponding to the middle portion of said ceramic body; coating said ceramic body with a porous resin layer; eliminating said wax by heating said ceramic body; and coating an air-tight resin layer on said porous resin layer. 7. A piezoelectric ceramic resonator comprising: a piezoelectric ceramic body having an upper surface and a lower surface facing opposite each other, a first electrode contacting said upper surface of said piezoelectric ceramic body, a second electrode contacting said lower surface of said piezoelectric ceramic body, and a plurality of lead pins, one end of each said lead pin being connected to either of said electrodes, wherein said first electrode and said second electrode have portions opposite with each other with said piezoelectric ceramic body between them. 8. The piezoelectric ceramic resonator according to Claim 7, wherein said lead pins have a shape of wires. 9. The piezoelectric ceramic resonator according to Claim 8, wherein said lead pins have flat portions which are electrically connected to said electrodes. 10. The piezoelectric ceramic resonator according to any one of Claims 7, 8, and 9, wherein said piezoelectric ceramic resonator further comprises an integral condenser. 11. A method of fabricating a piezoelectric ceramic resonator comprising a piezoelectric ceramic body having an upper surface and a lower surface facing opposite with each other, a first electrode contacting said upper surface of said piezoelectric ceramic body, a second electrode contacting said lower surface of said piezoelectric ceramic body, and a plurality of lead pins, one end of each said lead pin being connected to either of said electrodes, wherein said first electrode and said second electrode have portions opposite with each other with said piezoelectric ceramic body between them, the method comprising the steps of: installing said first and second electrodes on said piezoelectric ceramic body; fixing one ends of said lead pins, which are wires cut by a predetermined length, on a tape parallel with one another and with a constant spacing; applying solder paste on the other ends of said lead pins which are not fixed on said tape; attaching said lower surface of said ceramic body on said ends of two adjacent lead pins on which solder paste has been applied, in order to electrically disconnect one of said two ends to said second electrode and to electrically connect the other of said two ends to said second electrode; applying solder paste on the portion of said ceramic body at which said lead pins attached in order to electrically connect said end of said lead pin which are not electrically connected to said second electrode to said first electrode on said upper surface; reflow curing said solder paste by heat treating said ceramic bodies and said lead pins; applying wax on portions of said electrodes corresponding to the middle portions of said upper surface and said lower surface of said ceramic body; coating said ceramic body with a porous resin layer; eliminating said wax by heating said ceramic body; and coating an air-tight resin layer on said porous resin layer.

Inventors: JUNG JUNG MEE, JUNG, JUNG, MEE
Applicants: CORETECH CO LTD, JUNG JUNG MEE, CORETECH CO., LTD., JUNG, JUNG, MEE
Application year: 1998
Main classification: H03H9
IPC codes: H01L41, H03H3, H03H9