JPS5943807B2 - Manufacturing method of cylindrical ceramic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an improved method for making cylindrical ceramic capacitors.

A conventional cylindrical ceramic capacitor is generally constructed as shown in FIG.

That is, an internal electrode 3 is formed on the inner circumferential surface 2 of a cylindrical ceramic body 1 that serves as a dielectric of a capacitor, an external electrode 5 is formed on the outer circumferential surface 4, and a lead-out portion of the internal electrode 3 to the outer circumferential surface is formed. 3a is covered with a metal cap 6, and external electrode 5 is also covered with a similar metal cap 6.

Since the metal cap 6 and the electrodes 3 and 5 are bonded by solder 7 by solder dipping, the solder 7 is also attached to the outer surface of the metal cap 6 and the outer electrodes, particularly the outer electrode 5.

8 is a protective film made of epoxy, phenol-modified epoxy, etc. for moisture proofing and electrical insulation, and lead wire 9
It is provided on the entire outer circumferential surface except for.

Generally, the above-mentioned cylindrical ceramic capacitor is mounted on, for example, a printed circuit board, and solder-bonded to a circuit by dipping the printed circuit board in solder.

When soldering like this, the temperature is about 270℃ and the temperature is about 10 seconds.
heat is added to the capacitor lead wire.

Furthermore, heat may be applied to the capacitor not only during soldering described above but also during connection or use of the capacitor.

When heat exceeding the melting point of the solder 7 is applied to the completed capacitor, the solder 7 melts and undergoes significant thermal expansion.

For this reason, the solder 7 passes under the protective film 8 and flows in the direction of the lead wire 9, adversely affecting the external circuit, or flows into the hollow part of the capacitor, causing damage between the external electrode 5 and the internal electrode 3. Deterioration of characteristics or short circuit may occur.

Further, due to the leakage or deterioration of the solder 7 on the outer surface of the metal cap 6, moisture or the like may enter between the metal cap 6 and the protective film 8, causing deterioration of the capacitor characteristics.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for mass-producing cylindrical ceramic capacitors whose characteristics are less likely to deteriorate.

The present invention for achieving the above object will be described with reference to the reference numerals in the drawings showing the embodiments for easy understanding.
From the inner peripheral surface 14 to the outer peripheral surface 15 of the cylindrical ceramic body 13
An internal electrode 16 is provided so as to extend to one end, and an external electrode 1 is provided at a portion including the other end of the outer circumferential surface 15 of the ceramic body 13 and electrically isolated from the internal electrode 16.
7 to complete the capacitor element 11, the cylindrical portion 18, the closed portion 20 of the cylindrical portion 18, and the closed portion 20
A pair of metal caps 12 are prepared, each consisting of a lead wire 21 led out from the center of the outer peripheral surface of 16, and the other of the pair of metal caps 12 is fitted onto the ceramic body 1.
3, a step of fitting onto the external electrode 17 at the other end of the outer circumferential surface 15; a step of providing a non-solder adhesion film 22 on most of the outer surfaces of the pair of metal caps 12; 11 fitted with the pair of metal caps 12 and provided with the solder non-adhesion film 22, and immersed in molten solder to separate the spaces between the pair of metal caps 12 and the internal and external electrodes 16.1γ, respectively. A cylindrical ceramic capacitor comprising a step of soldering and a step of providing an insulator coating layer 25 so as to cover the outer periphery of the pair of metal caps 12 and the capacitor element 11 except for the lead-out portion of the lead wire 21. It is related to the manufacturing method.

According to the above invention, since the solder non-adhesion film 22 is provided on the outer surfaces of the pair of metal caps 12 and then immersed in molten solder, adhesion of solder to the outer surfaces of the metal caps 12 is prevented, and the inside of the metal caps 12 is and external electrode 16,1
7 can be achieved by soldering.

Therefore, when the capacitor completed with the insulating coating layer 25 is heated in order to connect it to an external circuit, the solder on the outer surface of the metal cap 12 melts and flows out, resulting in a problem that the characteristics deteriorate. It is possible to mass-produce capacitors that do not cause this problem.

Next, embodiments of the present invention will be described with reference to the drawings.

2 to 9 are for explaining the cylindrical ceramic capacitor and its manufacturing method according to the present invention, in which FIG. 2 shows a capacitor element 11 provided with electrodes, and FIGS. 5 shows the metal cap 12, FIGS. 6 and 7 show the metal cap 12 fitted to the capacitor element 11 and masked, and FIG. 8 shows the metal cap 12 bonded to the capacitor element 11 by soldering. Fig. 9 shows the completed cylindrical magnetic capacitor.

As shown in FIG. 2, the capacitor element 11 has an internal electrode 16 provided on a part of the inner circumferential surface 14 and outer circumferential surface 15 of a cylindrical ceramic body 13, and an outer circumferential electrode 16 facing the internal electrode 16 on the inner circumferential surface. An external electrode 17 is provided on the surface 15.

In this embodiment, both ends 13 of the cylindrical ceramic body 13
a and 13b are polished to have roundness.

This makes the thickness of the metal layer reaching the lead-out portion 16a of the internal electrode 16 uniform.

Further, if the ends 13a and 13b are rounded in this way, the metal cap 12 can be easily fitted.

The internal electrode 16 and the external electrode 17 are each silver electrodes.

The mechanical dimensions of the cylindrical ceramic body 13 are, for example, 2 mm in outer diameter and 7 mm in length.

As shown in FIGS. 3 and 4, the metal cap 12 is formed into a tip shape, and has four projections 19, which can be elastically deformed or displaced, provided on the cylindrical portion 18 by press working.

Further, the vicinity of the end of the cylindrical portion 18 and the closing portion 20 are made thin by press working.

In this embodiment, the inner diameter of the cylindrical portion 18 is 2.1 m.
m, the height of the protrusion 9 is 0.1 mm, the inner diameter of the thin part near the end of the cylindrical part 18 is 2.24 mm, the thickness of the metal plate of the cap 12 is 0.2 mm, the thickness of the bottom part 20 is O, 14m
m.

The inner diameter of the open end of the cylindrical portion 18 is set to a size that allows insertion of even the largest diameter capacitor element 11 caused by variations, and the height of the protrusion 19 is set to a size that allows insertion of the capacitor element 11 of the smallest diameter caused by variations. It is sized so that it can be held elastically.

That is, even if there is variation in the outer diameter of the capacitor element 11 provided with the cylindrical ceramic body 13 and the electrodes, as long as the variation is within the allowable range, any capacitor element 1 can be used.
1 is elastically held by a protrusion 19.

The metal cap 12 described above is made by preparing a metal plate made of iron or brass, and first, by deforming the metal plate, the band-shaped protrusion 1 is formed.
9 are formed radially, and then the closing portion 20 is made thin with a press, and then cut into a disk shape and pressed into a tap shape.

In this embodiment, the lead wire 21 is welded after molding.

Capacitor element 11 as shown in FIG. 2 and FIGS. 3 to 5
Once the metal cap 12 as shown in the figure is prepared, next
As shown in FIGS. 6 and 7, a metal cap 12 is fitted onto the capacitor element 11.

At this time, the end portion 13a of the cylindrical ceramic body 13.

13b is rounded and the protrusion 19 is elastically displaced by elastic deformation of the metal cap.
The metal cap 12 can be fitted onto the capacitor element 11 relatively easily.

Moreover, once the metal cap 12 is installed in a predetermined position, the metal cap 12 will not be displaced due to the elastic holding by the projections 19.

After fitting the metal cap 12, as shown in FIG.
A non-solder adhesion film 22 is provided on the upper surface of 7.

For this solder non-adhesion film 22, a solder resist ink having a high heat distortion temperature, phenol resin #100 (manufactured by Origin Electric Co., Ltd.), or the like is suitable.

The non-solder adhesion film 22 covers the metal cap 12 and the external electrode 17.
The solder non-adhesion film 22 on the ceramic body 13 is provided not only on the ceramic body 13 but also on the ceramic body 13.
is formed as a result of applying it symmetrically to improve workability.

After the masking, that is, the formation of the solder-free film, is completed, the capacitor element 1 with the metal cap 12 fitted in a heating furnace is first placed in order to perform solder bonding and hermetic sealing.
1 and gradually increase the heating temperature to about 240-250℃.
A heat treatment is performed at °C for about 2 minutes, and the air inside the cylindrical ceramic body 13 is exhausted.

Next, following heat treatment, solder with a melting point of 187°C is applied to about 220°C.
The combined body of capacitor element 11 and metal cap 12, whose temperature has been raised by heat treatment, is immersed in a solder bath obtained by heating to ~240° C., and is naturally cooled after being pulled out of the solder bath.

As a result, the solder 24 intrudes into the gap 23 formed between the outer periphery of the capacitor element 11 and the inner periphery of the metal cap 12 based on the protrusion 19 as shown in FIG.

This penetration of the solder 24 progresses extremely well because the inside of the metal cap is in a reduced pressure state due to the heat treatment.

As a result, the solder 24 is embedded in the gap 23 as shown in FIG. 8, and the hermetic seal is completely achieved, and the metal cap 12 is firmly connected to the electrodes 16 and 17 of the capacitor element 11. .

During solder bonding by this solder dipping, since the solder non-adhesion film 22 is provided on the outer surface of the metal cap 12 and the external electrode 1γ, solder does not adhere there, and the solder 2
The adhesion amount and adhesion area of No. 4 are greatly regulated.

After soldering is completed, next, heat this at about 160°C below the solder melting point for about 2 minutes, and in the heated state, epoxy,
Contact with powder of a thermosetting synthetic resin such as phenol-modified epoxy to coat the outer circumferential surface excluding the lead wire 21, and then final heat treatment at about 160° C. for about 20 minutes. Then, a synthetic resin coating layer 25 is formed as shown in FIG.

Even if heat treatment is performed in this synthetic resin coating process, air will not be discharged from the inside through the gap because the cylindrical ceramic capacitor is hermetically sealed.

If there is a gap, the synthetic resin coating will not be achieved properly due to the exhausted air, resulting in poor appearance.

As you can understand from the explanation so far, the metal cap 12
A non-solder adhesion film 22 is provided on most of the external electrode 1γ, and the solder 24 is restricted only to the boundary between the metal cap 12 and the electrode 15. Even if the solder 24 melts due to the heating, it will not flow out in the direction of the lead wire 21.

Note that the melting and flowing of the solder 24 is also prevented by the solder non-adhesion film 22.

Furthermore, even if the solder 24 thermally expands and the synthetic resin coating layer 25 does not follow this thermal expansion, and the escape area for the melted solder 24 is restricted, the total amount of the solder 24 is reduced, so the capacitor element 11 It does not reach the point where it flows into the inside of the body.

Furthermore, since no solder is interposed between the synthetic resin coating layer 25 and the upper surface of the metal cap 12, and the non-solder adhesion film 22 is interposed, solder leakage or deterioration is prevented by expansion and contraction of the solder due to thermal cycles. A capacitor with little characteristic deterioration can be provided without the formation of a moisture infiltration path.

Since the solder 24 is controlled by a masking method, the workability is improved.

Particularly in this embodiment, since the solder non-adhesion films 22 are provided symmetrically, manufacturing can be made more efficiently.

Further, in this embodiment, a protrusion 19 is provided on the metal cap 12 and its inner circumference is made non-circular so that a slit 23 is created between the protrusion 19 and the capacitor element 11, and the air inside is exhausted by heating. Since the solder is immersed in the capacitor body 11 and the metal cap 1, the solder smoothly penetrates into the gaps.
2 are firmly connected, and a hermetic seal is completely achieved.

In addition, since a hermetic seal is achieved, even if heating is subsequently performed for resin coating, air is exhausted from the inside and the resin coating does not peel off.

Furthermore, since the metal cap 12 in this embodiment has the elastically displaceable protrusion 19, the metal cap 12 can be easily and securely fitted onto the capacitor body 11.

In addition, since the inner diameter of the open end of the metal cap 12 is made smaller than the outer diameter of the capacitor element 11, the capacitor element 1
1 can be inserted smoothly.

In this embodiment, the ends 13a, 1 of the ceramic body 13
Since the capacitor element 3b is rounded, the capacitor element 11 can be inserted into the metal cap 12 very easily, and the end portion of the ceramic body 13 is less likely to be damaged.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be further modified.

For example, the metal cap 12 may be provided with a polygonal elastically deformable portion to elastically hold the capacitor element 11.

In short, the non-circular portion of the metal cap may have any shape.

Furthermore, the solder-free film 22 may be provided on all or part of the inner circumferential surface of the metal cap 12.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional cylindrical ceramic capacitor.
2 to 9 show one embodiment of the present invention, in which FIG. 2 is a sectional view of a capacitor element, FIG. 3 is a front view of a metal cap, and FIG. 4 is a cap shown in FIG. 3. Right side view of
Figure 5 is a vertical cross-sectional view of the cap shown in Figure 3, Figure 6 is a cross-sectional view of the capacitor element with the metal cap covered and a solder-free film provided, and Figure 7 is the line ■-■ in Figure 6. 8 is a sectional view taken along the line ■--■ in FIG. 9, and FIG. 9 is a sectional view of the completed cylindrical ceramic capacitor. In the symbols used in the drawings, 11 is a capacitor element, 12 is a metal cap, 13 is a ceramic element,
16 is an internal electrode, 17 is an external electrode, 18 is a cylindrical part, 19
22 is a protrusion, 22 is a solder-free film, 24 is solder, and 25 is a synthetic resin coating layer (insulating coating layer).

Claims (1)

[Scope of Claims] 1. An internal electrode 16 is provided to extend from the inner circumferential surface 14 of the cylindrical ceramic body 13 to one end of the outer circumferential surface 15, and is electrically separated from the internal electrode 16. a step of completing the capacitor element 11 by providing an external electrode 17 on a portion including the other end of the outer circumferential surface 15 of the ceramic body 13; and a step of completing the capacitor element 11;
A pair of metal caps 12 consisting of a lead wire 21 led out from the center of the outer peripheral surface of the ceramic body 13 are prepared, and one of the pair of metal caps 12 is connected to the inside of one end of the outer peripheral surface 15 of the ceramic body 13. fitting onto the electrode 16 and fitting the other of the pair of metal caps 12 onto the external electrode 17 at the other end of the outer peripheral surface 15 of the ceramic body 13; a step of providing a solder-free film 22 on most of the outer surface of the cap 12; and a step of providing the pair of metal caps 12 on the capacitor element 11;
a step in which the pair of metal caps 12 and the internal and external electrodes 16 and 17 are soldered together by fitting the metal caps 12 and the solder-free film 22 is immersed in molten solder; A method for manufacturing a cylindrical ceramic capacitor comprising the step of providing an insulating coating layer 25 so as to cover the outer circumferences of the pair of metal cables 12 and the capacitor element 11 except for the lead-out portions of the wires 21.