JPS6128207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a ceramic capacitor of the type in which a metal cap is fitted onto a ceramic tube (cylindrical body) having a pair of electrodes, and more particularly, to The present invention relates to a method of manufacturing a ceramic capacitor with an improved method of coupling the capacitor and the metal cap.

The ceramic body for constructing a ceramic capacitor is
For example, it is made by molding and sintering a mixture of a ceramic material whose main component is barium titanate (BaTiO ₃ ) or strontium titanate (SrTiO ₃ ) and a binder. However, the molded product is fired. Sintering shrinkage of about 20% occurs with variations, and the dimensions of the porcelain body also vary. Therefore, when manufacturing a cylindrical porcelain capacitor with a metal cap, a metal cap with a spring is fitted onto a porcelain tube.

Incidentally, it is desirable that the bond between the porcelain tube having the electrode and the metal cap be strong. For this reason, US Pat. No. 3,233,028 discloses that a metal cap is fitted and then molded with a synthetic resin.

On the other hand, in order to keep the electrical characteristics of the cylindrical ceramic capacitor stable over a long period of time, it is required to substantially isolate the interior (hollow part) of the ceramic tube from the outside air. Therefore, the above-mentioned U.S. Patent No. 3233028
No. 1, it is disclosed that the hollow part is filled with silicone gel.

However, the above-mentioned US Pat. No. 3,233,028 does not disclose that a metal cap and a porcelain tube (capacitor element) having an electrode are firmly bonded together before molding with a synthetic resin.

Further, there is no disclosure of protecting the hollow portion of a porcelain tube without filling the hollow portion with silicone gel or the like.

In order to strengthen the bond between the porcelain tube and the metal cap and to protect the inside of the porcelain tube hermetically, solder or conductive adhesive is attached to the boundary area between the electrode on the porcelain tube and the metal cap,
It is conceivable to firmly connect the metal cap and the electrode electrically and mechanically, and to hermetically seal the inside of the porcelain tube with solder or conductive adhesive. However, solder or conductive adhesive can penetrate between the metal cap and the magnetic tube, often creating a short between one electrode and the other.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a ceramic capacitor that can firmly connect a ceramic tube having electrodes to a metal cap and protect the ceramic tube.

To achieve the above object, the present invention provides a cylindrical ceramic dielectric body (ceramic tube) having first and second electrodes formed on the outer circumferential surface near one end and the outer circumferential surface near the other end, respectively. ,Ten~
Soaking in 40% rosin alcohol solution,
next, drying the rosin adhering to the cylindrical porcelain dielectric;
fitting first and second metal caps onto the first and second electrodes, each having a solder layer at a portion that contacts the electrodes and having a function as a terminal;
Next, melting the solder layer by heating to electrically connect the first and second electrodes and the first and second metal caps with the solder layer;
The present invention relates to a method for manufacturing a cylindrical ceramic capacitor having a metal cap, characterized in that it includes:

According to the above invention, a cylindrical porcelain dielectric material having electrodes is treated with a 10 to 40% rosin alcohol solution, and this is dried to form a rosin film, so that the solder layer of the metal cap can be used to form a rosin film. Not only is the bonding with the electrodes good and easy to achieve, but the rosin film also acts effectively to insulate between the electrodes, protect the electrodes, and prevent moisture, making it possible to provide a capacitor with excellent characteristics.

Embodiments of the present invention will be described below based on the drawings.

Example 1 To explain the cylindrical porcelain capacitor according to the first example of the present invention in the order of steps, first, a mixture of a dielectric ceramic material containing strontium titanate (SrTiO ₃ ) as a main component and a binder is extruded. The ceramic tube 20 shown in FIG. 1 is formed by molding it into a long hollow cylinder using a machine, then cutting it to an appropriate length, firing it, and then polishing (chamfering) the end face. .

Next, a pin coated with a conductive paint made of silver powder, glass frit, resin, and solvent, ie, silver paint, is inserted into the hollow part of the ceramic tube 20, that is, the through hole 21.
The roller coated with the silver paint is brought into contact with the outer circumferential surface 22 of the 0, and the silver paint is applied only to a predetermined area and baked at 500 to 800°C to form the inner electrode as shown in FIG. A first electrode 23 and a second electrode 24 as an outer electrode are formed. The first electrode 23 in this embodiment is the tube 20
It is formed on the wall of the through hole 21, that is, on the inner circumferential surface of the tube 20, with a blank space of about 0.3 mm from the right end 25 of the tube 20, and is led out to the outer circumferential surface 22 via the left end 26 of the tube 20. On the other hand, the second
The electrode 24 of the tube 20 has first and second separation regions 27 and 28 between it and the first electrode 23.
It is formed on the outer peripheral surface 22 of.

The dimensions of the ceramic tube 20 having the pair of electrodes 23 and 24 shown in FIG. 1 are as follows: the length of the tube 20 is approximately 7 mm, the outer diameter is approximately 1.78 mm
Since the diameter of the through hole 21 is about 1 mm and the thickness of the first and second electrodes 23, 24 is about 10 μm, the outer diameter of the cylindrical capacitor element on which the electrodes 23, 24 are formed is about 1.8 mm. be. Further, the left and right ends 25 and 26 of the tube 20 are polished (chamfered) to form curved surfaces with a radius of about 0.25 mm. This left and right end 2
Polishing steps 5 and 26 are necessary to smoothly press fit the tube 20 into the metal cap.

Next, the ceramic tube 20 having the first and second electrodes 23, 24 is placed in an alcoholic solution of rosin (pine resin) with a low chlorine content of preferably 0.03% or less (preferably 10 to 40%, more preferably 20%). The first and second electrodes 23,
24 and the first and second separation regions 27, 28
A rosin film of about several angstroms is formed on top of the rosin film. Since this rosin film is extremely thin, it is omitted in many drawings such as FIG. 1, but is indicated by the numeral 29 in the enlarged view of FIG. 8. This rosin film 29 helps solder bonding between the first and second electrodes 23, 24 and the metal cap in a later process, prevents oxidation of the first and second electrodes 23, 24, and also serves as a moisture-proof film. also has a resistivity of about 10 ¹⁵ Ωcm, so the first and second separation regions 27 and 2
8 also functions as an insulating film for insulating and separating the first and second electrodes 23 and 24.

2-4 illustrate a metal cap 30 for fitting onto a ceramic tube 20 or capacitor element having a pair of electrodes 23, 24 shown in FIG. This metal cap 30 is press-formed from a cold-rolled steel plate, and is formed into a cup shape with a cylindrical portion 32 and a bottom portion 33, and further includes four slits 34 cut from one end 31, and a bottom portion 33. It has four protrusions 35 for press-contacting the electrodes provided between the four slits 34.
The diameter of the inscribed circle of the four protrusions 35 that protrude inward from the inner circumferential surface 36 of the cylindrical portion 32 is slightly larger than the outer diameter of the electrode 23 indicated by the chain line. Further, in order to facilitate press-fitting of the tube 20, the protrusion 35 is formed in a hemispherical or trapezoidal shape.

In this embodiment, the inner diameter of the cylindrical portion 32 is 1.85 mm, and the diameter of the inscribed circle of the four protrusions 35 arranged at approximately equal intervals on the inner peripheral surface 36 is 1.75 mm. Therefore, the height of the protrusion 35 is 0.05 mm. Also, since the thickness of the metal cap 30 is 0.15 mm, its outer diameter is 2.15 mm.
mm. The depth from one end 31 of the metal cap 30 to the bottom 33 is 1.4 mm, and a slit 34 having a width of about 0.05 mm is formed at about 2/3 of the depth. The diameter of the inscribed circle of the protrusion 35 is preferably in the range of 93.8% to 99.8%, more preferably 93.8% to 99.5%, and more preferably 97.1% of the outer diameter of the first and second electrodes 23 and 24. % to 97.6% is most preferred. If the inscribed circle of the protrusion 35 is too large, the ceramic tube 20 having the pair of electrodes 23, 24 and the metal cap 30 may be defective due to looseness or omission, or the gap between the electrodes 23, 24 and the metal cap 30 may be Poor electrical contact, and
On the other hand, if the inscribed circle of the protrusion 35 is too small, the metal cap 30 may cause damage or micro-cracks to the ceramic tube 20 during press-fitting. This increases the number of defects in which the insulation resistance does not reach a predetermined value.

The height of the protrusion 35 formed on the metal cap 30 is 0.03 to 1.8 mm with respect to the outer diameter of the electrodes 23 and 24.
Preferably it is in the range 0.05mm, most preferably in the range 0.03-0.04mm.

The metal cap 30 is a ceramic tube 2.
Since the cylindrical portion 32 must be deformed to a larger diameter by the press-fitting, annealing is performed at approximately 600° C. for approximately 30 minutes in this embodiment.
When annealing is performed and the slit 34 is provided in this manner, an elliptical deformation of approximately 20% occurs by pressing the outer circumference of the cylindrical portion 32 with a force of 1.3 kg. This amount of deformation is suitable for press-fitting a capacitor element, and can also be obtained by using brass as the metal cap material instead of iron and annealing at about 500° C. for about 20 minutes.

Although omitted in FIGS. 2 to 4, the metal cap 30 has a copper plating layer 38 of approximately 1 μm on the iron base 37, as shown in FIG. It has a solder layer 39 of about 4 μm on top. This solder layer 39 is a solder layer having a ratio of 8 to 12% lead and 88 to 92% tin, preferably 10% lead and 90% tin, and is formed by plating. The solder layer 39 connects the protrusion 35 to the first or second electrode 23, 24.
However, it is not used to internally hermetically seal the metal cap 30 and tube 20. Therefore, the thickness of the solder layer 39 is preferably in the range of 3 to 10 μm. Further, in this embodiment, the solder layer 39 is provided around the entire circumference of the metal cap 30, but it may be provided by coating only on the protrusion 35 or the vicinity thereof.

As is clear from FIGS. 2 to 4, a lead wire 40 for connection to an external circuit is electrically welded to the center of the bottom 33 of the metal cap 30. This welding of the lead wire 40 is performed using a ceramic material having electrodes.
Although this may be carried out after fitting the metal cap 30 to the tube 20, in this embodiment, it is carried out immediately before fitting the metal cap 30 in order to facilitate automation.

Next, a fifth
As shown in the figure, the first metal cap 30 and the second metal cap 41 are fitted. The structure of the second metal cap 41 is completely the same as that of the first metal cap 30, so each part is given the same reference numeral and the explanation thereof will be omitted. In this embodiment, in order to efficiently fit the first and second metal caps 30 and 41 using an automated device, the ceramic tube 20 having a pair of electrodes 23 and 24, that is, the capacitor element, is fixed. The first metal cap 30 is
This is done by moving from left to right in the figure and simultaneously moving the second metal cap 41 from right to left.
The first and second metal caps 30 and 41 are each provided with a protrusion 35, and the inner diameter of one end 31 is larger than the outer diameter of the first and second electrodes 23 and 24, so that the cylindrical portion 32 Inside, electrode 2
The tube 20 with 3 and 24 is easily inserted. As the first and second metal caps 30 and 41 continue to move, the protrusion 3 of the first metal cap 30
5 bites into the first electrode 23, and the protrusion 35 of the second metal cap 41 bites into the second electrode 24. At this time, the right end 25 and left end 26 of the ceramic tube 20 are chamfered, and the protrusion 35 is chamfered.
is formed in a hemispherical shape, so that the first and second electrodes 23, 24 and the first and second metal caps 3
The engagement of the protrusions 35 of 0 and 41 starts smoothly. As the first and second metal caps 30 and 41 move, the first and second metal caps 30 and 41 initially move.
0 and 41 are elastically deformed by the action of the slit 34, but finally exceed the elastic limit and undergo plastic deformation, and are firmly electrically and mechanically connected to the first and second electrodes 23 and 24, respectively.

However, if there are variations in the diameter of the ceramic tube 20, one or two of the four protrusions 35 may
does not contact the first and second electrodes 23 and 24. Therefore, the solder layer 39 of the metal caps 30, 41 is melted by heat treatment at about 350° C. for about 30 seconds, and the solder is interposed between the protrusion 35 and the first and second electrodes 23, 24. Achieve electrical and mechanical coupling. Further, even in the protrusion 35 that has already bitten into the first and second electrodes 23 and 24, the protrusion 3
5 and its vicinity and the first and second electrodes 23, 24
By interposing solder between the two, the electrical and mechanical connection is further strengthened. In addition, the rosin film 2 mentioned above
9 aids in the solder bonding described above.

Next, the lead wire 4 of the first metal cap 30
0, and the lead wire 42 of the second metal cap 41
Straighten with a strainer. The lead wires 40 and 42 are connected at this stage without completing the porcelain capacitor.
A pair of lead wires 40 and 42 are used to straighten the bend.
This is to uniformly and easily form a seal layer and an exterior insulating layer, which will be described later, while rotating the ceramic tube 20 and the pair of metal caps 30, 41 about the axis. In this embodiment, as described above, the pair of metal caps 30, 41 are already firmly connected to the pair of electrodes 23, 24, so even if the lead wires 40, 42 are pulled with a strainer, the metal caps 30, 41
There is almost no possibility that 1 will come off from the electrodes 23 and 24 of the ceramic tube 20.

Next, bisphenol A type epoxy resin,
Prepare an insulating paint consisting of a filler and a hardening agent,
The roller coated with this is applied to the boundary area between the first and second metal caps 30, 41 and the first and second electrodes 23, 24 on the ceramic tube 20, and cured. At this time, in order to prevent the air inside the tube 20 from expanding and blowing out due to heating during the curing process or subsequent processes, the ceramic tube 2 is covered with metal caps 30 and 41 in advance.
0 to 250℃~350℃ higher than the maximum temperature of the subsequent process
After heating the tube 20 and expelling a portion of the air inside the tube 20, an insulating paint for sealing is applied. Of course,
Instead of heating, the sealing insulating paint may be applied after some or all of the air in the tube 20 is exhausted by vacuum means. The application of the insulating paint is carried out by moving the roller coated with the insulating paint to the metal cap 3 with the pair of lead wires 40 and 42 supported by bearings.
0, 41 and the electrodes 23, 24, the tube 20 on which the metal caps 30, 41 are attached rotates with the pair of lead wires 40, 42 as the axis, and the coating is carried out while the tube 20 is rotating. The insulating paint is applied relatively uniformly all around the boundary area. After that, the insulating paint is cured at about 150℃ for about 20 minutes.
A sealing layer 43 having a thickness of approximately 70 μm is formed on the metal caps 30, 41. Note that the sealing layer 43 is also formed on the slit 34 and the metal cap 30,
41 and the inside of the tube 20 are made airtight.
At this time, the slit 34 is extremely narrow (approximately 0.05 mm)
Therefore, it can be easily sealed with insulating paint. In this sealing process, even if the insulating paint penetrates deeply into the metal caps 30 and 41, since they are insulators, the first electrode 23 and the second electrode 2
4 short circuit does not occur. The sealing layer 43 has a temperature of -65°C.
It is required to withstand heat cycles in the range of ~130°C, have good adhesion and moisture resistance, and be insulating. In order to satisfy such conditions, in this example, bisphenol A type epoxy resin was mixed with talc (Mg ₃ Si ₄ O ₁₀ (OH) ₂ ), calcium carbonate (AaCO ₃ ), and silica (SiO ₂ ). An insulating paint with a viscosity of approximately 48,000 cps is used, which contains approximately 31.5% filler and an acid anhydride curing agent. According to this insulating paint, the shore D that can withstand heat cycles is approximately 65.
A sealing layer 43 having a hardness of . Further, the water absorption rate of the seal layer 43 after boiling for 1 hour is 0.1% or less. Also, the metal cap 30 with the sealing layer 43,
The adhesive strength between 41 and electrodes 23 and 24 is approximately 100 kg/
^cm2 . Furthermore, the resistivity of the seal layer 43 is approximately 2.7×
10 ¹⁴ Ωcm. Further, as shown in FIG. 6, a product provided with a sealing layer 43 was immersed in a sealing test liquid at 125° C. to examine whether bubbles were continuously generated or not, but no bubbles were generated at all.

By the way, in order for the seal layer 43 to withstand heat cycles, it is desirable that its hardness is in the range of 50 to 80 in Shore D, and most preferably about 65. Then, such a seal layer 43
is obtained by adding 25 to 35% filler to bisphenol A type epoxy resin. The filler may be a mixture of the aforementioned talc, calcium carbonate, and silica, or may be one or two selected from these. Of course, other fillers selected from commonly used fillers may also be used.

In the above embodiment, bisphenol A type epoxy resin is used, but in addition to this, the sealing layer 43 can be made with or without a filler added to polybutadiene resin, polyurethane resin, epoxy resin, silicone rubber, etc. It is also possible to form

After the formation of the sealing layer 43 is completed, an alcoholic solution of phenolic resin is applied to the ceramic tube 20 to further improve its moisture-proofing properties.
By curing at 150°C, the first
A covering insulating layer 44 is formed to a thickness of several angstroms. Next, the capacitor element is heated to a temperature at which the powder epoxy resin can be melted (approximately 200°C), and the heated capacitor element is rotated using a pair of lead wires 40 and 42 while the powder epoxy resin is melted. Contact the resin to melt and adhere it to the entire circumference, then heat at approximately 170℃ for 15 minutes (baking)
As a result, the second covering insulating layer 45 shown in FIG. 7 is formed so as to have an outer diameter of about 2.7 mm. Of course, the capacitor element is heated when forming the first and second covering insulating layers 44 and 45, but
Some or all of the air in the metal caps 30, 41 and the tube 20 is discharged in advance and hermetically sealed with the seal layer 43, so the air expands and blows out through the seal layer 43. 1st
And no pinholes are generated in the second covering insulating layers 44, 45.

In this embodiment, the first and second metal caps 30 and 41 are firmly connected to the first and second electrodes 23 and 24 by press-fitting and deformation, and are also connected by solder at the protrusion 35, Furthermore, since they are bonded by the sealing layer 43, the first and second insulating coating layers 44, 45 contribute only a small amount to the bonding between the metal caps 30, 41 and the electrodes 23, 24 of the ceramic tube 20. It's okay. For this reason, the first
The second covering insulating layers 44 and 45 are formed relatively thin.

Although not shown in FIG. 7, the ceramic capacitor is colored for a color code if necessary, and the porcelain capacitor is completed. The completed porcelain chirapacita is used by connecting a pair of lead wires 40, 42 to an electrical circuit.

The ceramic capacitor and its manufacturing method of this embodiment have the following merits.

(a) Since the sealing layer 43 is made of insulating paint, short circuits between electrodes will not occur even if the insulating paint penetrates inside.

(b) Since the seal layer 43 has elasticity or flexibility, it can withstand heat cycles of about -65 to 130°C.

(c) Since the sealing layer 43 has excellent adhesiveness and moisture resistance, it can protect the hollow portion of the ceramic tube 20, that is, the through hole 21 from the outside.

(d) Before forming the seal layer 43, the internal air is exhausted, so heating for forming the seal layer 43 or the first and second coating insulation layers 44, 4 is performed.
There is little risk of internal air blowing out due to heating etc. when forming 5.

(e) Connect the protrusions 35 of the metal caps 30 and 41 to the electrode 2.
3 and 24, and before forming the seal layer 43, the inside and outside communicate with each other at a portion other than the protrusion 35, so that the air inside can be quickly discharged. becomes possible.

(f) Since the metal caps 30 and 41 are press-fitted and deformed, and the protrusions 35 are firmly electrically and mechanically connected to the electrodes 23 and 24, a process for straightening the bends in the lead wires can be performed before the capacitor is completed. It becomes possible. Therefore, while rotating the capacitor element around the lead wires 40 and 42, the seal layer 4
3. It becomes possible to form the first and second covering insulating layers 44 and 45 relatively uniformly and efficiently.

(g) Since the solder layer 39 is provided on the metal caps 30, 41 in advance and is melted, the protrusion 35 is also connected to the electrodes 23, 24 by solder, so that electrical and mechanical connections are maintained. It becomes even stronger.

(h) Since the rosin film 29 is formed on the ceramic tube 20 having the electrodes 23 and 24,
Not only is solder bonding easier, but the electrodes 23,
24 anti-oxidation, moisture-proofing, and electrical insulation effects are also produced.

(i) Since the right end 25 and left end 26 of the ceramic tube 20 are chamfered, insertion into the metal caps 30, 41 can be performed smoothly.

(j) Since the bond between the metal caps 30, 41 and the ceramic tube 20 is strong and sealed, it is possible to make the first and second covering insulation layers 44, 45 thinner.

Embodiment 2 In FIG. 9 showing a porcelain capacitor according to a second embodiment of the present invention, parts common to the porcelain capacitor shown in FIG. 7 are given the same reference numerals. In this embodiment, as in the first embodiment, a ceramic tube 20 having first and second electrodes 23 and 24 is prepared, and a rosin film (not shown) is formed around the outer periphery of the ceramic tube 20. The metal caps 30a, 41a of the metal caps attached to the ceramic tube 20 have recesses 51 formed at their bottoms, in which the respective lead wires 40, 4 are inserted.
The metal caps 30 and 41 are exactly the same as the metal caps 30 and 41 described in the first embodiment, except that the metal caps 2 and 2 are welded.
Therefore, detailed explanation of each part will be omitted.

First and second metal caps 30a and 41a are applied to the ceramic tube 20, ie, the capacitor element, having electrodes 23 and 24 in the same manner as in Example 1, and then heated to remove the first and second metal caps. The protrusion 35 is soldered to the first and second electrodes 23, 24 by the solder layer of the second metal cap 30a, 41a. Next, as in Example 1, part of the internal air is exhausted, and the seal layer 43 is formed of the same insulating material as in Example 1. However, in this second embodiment, the seal layer 43 is also formed in the region between the first metal cap 30a and the second metal cap 41a in order to utilize it for moisture proofing. Such a sealing layer 43 is easily formed by applying an insulating paint to a stepped roller having a convex outer peripheral surface and bringing it into contact with the capacitor elements with metal caps 30a and 41a. In this embodiment, the sealing layer 43 has a moisture-proof function, so the first covering insulating layer 4 in the first embodiment
4 is not provided, and only a single covering insulating layer 45a made of powdered epoxy resin is provided. In this case, since the metal caps 30a and 41a are provided with the recesses 51, the epoxy resin for forming the insulating coating layer 45a is prevented from flowing out to the lead wires 40 and 42, thereby inhibiting electrical connection. The insulating layer is less likely to adhere to the lead wires 40, 42.

Recess 51 in metal cap 30a, 41a
In addition to the function of preventing the epoxy resin from flowing out as described above, the lead wires 40 and 42 have a function of positioning the lead wires 40 and 42 at the center of the bottom portion 33 of the metal caps 30a and 41a. Furthermore, as shown in FIG. 10, when the pair of lead wires 40 and 42 are bent and electrically coupled to the wiring conductor 53 of the circuit board 52, the lead wires 40 and 42 are bent at positions close to both ends 55 and 56 of the cylindrical capacitor element 54. It becomes possible to bend the lead wires 40 and 42, and it becomes possible to shorten the distance from the bent portion 40a of one lead wire 40 to the bent portion 42a of the other lead wire 42.

In order to obtain various functions as described above, the depth of the recess 51 is preferably in the range of 0.1 to 0.4 mm.
The diameter of lead wire 1 is preferably about 0.8 mm, which is slightly larger than the lead wires 40 and 42, which are 0.6 mm. In addition to the advantages based on the recess 51, this embodiment also has the advantages of items (a) to (j) described in the first embodiment.

Embodiment 3 In FIG. 11 showing a porcelain capacitor according to a third embodiment of the present invention, parts common to the porcelain capacitor shown in FIG. 7 are given the same reference numerals. In this third embodiment as well, a rosin film (4 not shown) is provided on the ceramic tube 20 having the first and second electrodes 23 and 24, and the first and second electrodes 23 and 24 are provided here. The second metal caps 61 and 62 are applied, the projections 35 are bitten into the first and second electrodes 23 and 24, and the sealing layer 43 is connected to the first and second electrodes 23 and 24 by soldering. It is also provided between the metal caps 62. In this embodiment, lead wires are not connected to the first and second metal caps 61 and 62, but a recess 51 similar to that shown in FIG. 9 is provided at the center of the bottom portion 33 of these caps. With a support shaft (not shown) in contact with this recess 51 and holding the capacitor element, a roller coated with an insulating sealing paint is brought into contact with the outer peripheral surface of the capacitor element to form an elastic insulating seal layer 43. Form. Next, an exterior covering insulating layer 63 is formed on the seal layer 43. At this time, the covering insulating layer 63 is not formed on the entire outer periphery, but the exposed surface 64 is formed on the cylindrical portion 32 of the first and second metal caps 61 and 62. Since this porcelain capacitor does not have lead wires, it has a pair of metal caps 61 and 62.
is used to couple the exposed surface 64 of the circuit board 65 to the wiring conductor 66 of the circuit board 65.

In addition to the advantages of providing the recessed portion 51, this embodiment has the advantages of (a), (b), and
It has the advantages of (c), (d), (e), (g), (h), (i), and (j).

Modifications Figures 12-14 show a modified metal cap 70. This metal cap 70 is also shown in Fig. 2~
Like the metal cap 30 shown in FIG.
5 and has a slit 34a cut from one end 31. The slit 34a is shown in Figure 2~
Unlike the case in Figure 4, it is V-shaped, and this V
A protrusion 35 is provided adjacent to the terminal end of the letter-shaped slit 34a. The height of the protrusion 35 is as shown in Figures 2 to 4.
Since the settings are the same as in the case shown in the figure, the pair of electrodes 2 of the ceramic tube 20 shown in FIG.
3 and 24. V-shaped slit 3
The width at one end 31 of 4a is approximately 0.2 mm, and the length of the cut is approximately 1/5 of the depth of 1.4 mm of the cylindrical portion 32.
It is approximately 0.28mm, which corresponds to . A recess 51 is provided in the bottom portion 33 as in the case of FIG. 9, and a lead wire 40 is connected thereto. This metal cap 7
0 can be used in place of the metal caps 30, 41 or 30a, 41a of the porcelain capacitor shown in FIG. 7 or 9. Also lead wire 4
If 0 is removed, it can be used in place of the metal caps 61 and 62 of the porcelain capacitor shown in FIG. In the case of this metal cap 70, the slit 34a is formed shallower than the protrusion 35, so when the capacitor element is press-fitted, the protrusion 35 is first elastically deformed, and then the protrusion 35 and its vicinity are plastically deformed, causing the capacitor element to deform. and metal cap 7
0 is strongly coupled. In this case, of course, the portion where the slit 34a is provided is deformed to have a larger diameter, which helps in press-fitting the capacitor element.

FIG. 15 shows a modified capacitor element for use in place of the capacitor element of FIG.
In this capacitor element, a common electrode 80 is provided in a hollow portion of a ceramic tube 20a, that is, a through hole 21a similar to that shown in FIG.
3a and 24a are provided. Therefore, a ceramic capacitor is formed in which the capacitance between the first electrode 23a and the common electrode 8 and the capacitance between the second electrode 24a and the common electrode are connected in series. In this case as well, the metal caps are of course coupled to the first and second electrodes 23a, 24a.

FIG. 16 shows yet another modification of the capacitor element. In this modification, from FIG. 15, the common electrode 8
0 is omitted, and the first and second electrodes 23a, 24 are provided only on the outer peripheral surface 22a of the ceramic tube 20a.
A is provided. Even with this configuration, 0.1~
A microcapacitor of 5 picoarad can be obtained. Of course, in this case as well, metal caps are applied to the first and second electrodes.

Although the embodiments and modifications of the present invention have been described above, various modifications are possible. For example, the porcelain tube 20 is not limited to the strontium titanate-based porcelain material, and may be formed of a barium titanate-based porcelain material, a titanium oxide-based porcelain material, or the like.
Further, the first and second electrodes 23 and 24 may have a two-layer structure including a nickel plating layer and a solder plating layer. In addition, the first and second electrodes 23, 2 are made of three layers: a silver coating baked layer, a nickel plating layer, and a solder plating layer.
4 may be formed. Further, as the rosin solution, a rosin with an activator added thereto may be used.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a porcelain tube having electrodes of a porcelain capacitor according to a first embodiment of the present invention. FIG. 2 is a front view of a metal cap for fitting onto the tube of FIG. 1; FIG. 3 is a right side view of the metal cap of FIG. 2. Fourth
The figure is a sectional view taken along the line -- of the metal cap shown in FIG. FIG. 5 is a cross-sectional view showing the tube shown in FIG. 1 in which the metal cap shown in FIG. 2 is fitted. 6th
This figure is a sectional view showing a state in which a sealing layer is provided on the capacitor of FIG. 5. FIG. 7 is a sectional view showing a completed ceramic capacitor by providing an exterior insulating layer on the capacitor of FIG. 6. FIG. 8 is an enlarged sectional view of the joint portion between the protrusion and the electrode. FIG. 9 is a sectional view showing a ceramic capacitor according to a second embodiment of the present invention. FIG. 10 is a partially vertical front view showing the ceramic capacitor of FIG. 9 mounted on a printed circuit board. FIG. 11 is a sectional view showing a state in which a ceramic capacitor and a printed circuit board are mounted according to a third embodiment of the present invention. FIG. 12 is a front view of the modified metal cap. FIG. 13 is a right side view of the metal cap of FIG. 12. 1st
FIG. 4 is a sectional view taken along the line -- in FIG. 13. FIG. 15 is a cross-sectional view of a porcelain tube with modified electrodes. FIG. 16 is a sectional view showing another example of a porcelain tube with deformed electrodes. In the symbols used in the drawings, 20 is a ceramic tube, 23 is a first electrode, and 24 is a ceramic tube.
2 is a second electrode, 27 is a first isolation region, 28 is a second isolation region, 29 is a rosin film, 30 is a first metal cap, 41 is a second metal cap, and 43 is a sealing layer.

Claims (1)

[Scope of Claims] 1. A cylindrical porcelain dielectric having first and second electrodes formed on the outer circumferential surface near one end and the outer circumferential surface near the other end, respectively, is soaked in a 10 to 40% rosin alcohol solution. Next, drying the rosin attached to the cylindrical porcelain dielectric; Next, at least the portions that contact the first and second electrodes have a solder layer and function as terminals. first and second metal caps having a
and a second electrode, and then melting the solder layer by heating to connect the first and second electrodes and the first and second metal caps with the solder layer. to electrically couple;
A method for manufacturing a cylindrical ceramic capacitor having a metal cap, the method comprising: