JPH11233370A - Ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic capacitor, capable of preventing cracks in the ceramic capacitor element. SOLUTION: A ceramic capacitor element 1 has terminal electrodes 11 and 12 with its each facing opposite end face. One end of metal terminals 2 and 3 are respectively connected to the terminal electrode 11 and 12. For the ceramic capacitor element 1, the average coefficient of linear expansion in the temperature range of 25 deg.C to -55 deg.C is assumed to be α1, that in 25 deg.C to 125 deg.C as α2 , and that of the metal terminal 2 and 3 in -55 deg.C to 125 deg.C as β, and the inequalities β<1.3α2 and β>0.7α1 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a ceramic capacitor. The present invention relates mainly to a multilayer chip type ceramic capacitor suitable for use as a smoothing capacitor for a switching power supply.

[0002]

2. Description of the Related Art Heretofore, as a smoothing capacitor for a switching power supply, an aluminum electrolytic capacitor has been mainly used. However, market demands for miniaturization, improved reliability, and the like have increased, and in response to this, there has been an increasing demand for small, highly reliable ceramic capacitors.

In general, since heat is generated around the power supply, an aluminum substrate having good heat dissipation is used as the substrate. However, a temperature change around the power supply due to turning on / off of the power supply is large, and a large thermal stress is generated in the ceramic capacitor mounted on the aluminum substrate having a high coefficient of thermal expansion. This thermal stress causes cracks in the ceramic capacitor and causes problems such as short-circuit failure and ignition.

In order to eliminate troubles such as ignition, it is important to reduce thermal stress generated in a ceramic capacitor. As a means to alleviate thermal stress,
No. 46258, JP-A-4-171911 and JP-A-4-259205 disclose soldering a metal plate to a terminal electrode of a ceramic capacitor and mounting the metal plate on an aluminum substrate. A structure is disclosed that prevents direct soldering to an aluminum substrate.

Usually, in order to sufficiently absorb the thermal stress caused by expansion and contraction of the aluminum substrate, the leg portion of the metal plate from the terminal portion soldered to the aluminum substrate to the connection portion with the ceramic capacitor should be as small as possible. It needs to be longer. However, in the conventional product, when the length of the metal plate is lengthened, the height of the ceramic capacitor is inevitably increased. Therefore, the length of the metal plate leg is set to a size within the allowable height of the substrate. Need to be restricted to

For this reason, in the conventional product, the length of the legs of the metal plate cannot be increased, and if the product is used for a long time in an environment (-55 to 125.degree. In addition, cracks are generated near the ends of the ceramic capacitor, and there is a high risk of fire. There is a serious problem with respect to reliability.

Conventionally, the metal plate has been made of phosphor bronze, silver, copper, stainless steel, aluminum, nickel silver, or the like. However, these metallic materials have an average linear expansion coefficient significantly larger than the average linear expansion coefficient of the ceramic dielectric material constituting the ceramic capacitor. For this reason, when used as a power supply peripheral part having a large temperature change, a large stress is applied particularly to a connection part of the metal plate due to a difference in an average linear expansion coefficient between the ceramic capacitor element and the metal plate, and the end of the ceramic capacitor is subjected to the stress. In some cases, cracks occurred near the part, causing troubles such as poor conduction and ignition.

[0008]

The problem to be solved by the present invention is as follows.
An object of the present invention is to provide a ceramic capacitor that can reliably prevent cracks, breakage, and the like from occurring in a ceramic capacitor element in a temperature range from 5 ° C. to 125 ° C.

[0009]

To solve the above-mentioned problems, a ceramic capacitor according to the present invention includes at least one ceramic capacitor element and at least one pair of metal terminals. The ceramic capacitor element has terminal electrodes on opposite side end faces, and each of the metal terminals is connected to one of the terminal electrodes.

[0010] The ceramic capacitor element is at 25 ° C.
From -55 ° C to α₁And 25 ° C
Is the average linear expansion coefficient from_TwoAnd when
α₁<Α_TwoMeet. The metal terminal is at -55 ° C to 12
The average linear expansion coefficient up to 5 ° C is β And β <1.3
α_TwoAnd β > 0.7α₁Meet.

Average linear expansion coefficient α₁, Α_TwoAnd β But the above
If the condition is satisfied, the temperature range from -55 ° C to 125 ° C
Around the ceramic capacitor element
It has been confirmed that loss can be reliably prevented.
Was.

When the main component of the dielectric is barium titanate, the average linear expansion coefficient of the ceramic dielectric is α ₁ ≦
7 × 10 ⁻⁶ and α ₂ ≧ 9 × 10 ⁻⁶ . When the main component of the ceramic dielectric is a lead-based composite perovskite, α ₁ ≦ 2 × 10 ⁻⁶ and α ₂ ≧ 3 × 10 ⁻⁶ .

Therefore, the average linear expansion coefficient β of the metal terminal
In the case where the main component of the dielectric is made of barium titanate and the case where the main component of the dielectric is made of a lead-based composite perovskite, it is necessary to consider the respective average linear expansion coefficients α1 and α2 and to determine the above condition. is there.

Other objects, configurations and advantages of the present invention will be more specifically described with reference to the accompanying drawings. The accompanying drawings merely show examples.

[0015]

FIG. 1 is a front view of a ceramic capacitor according to the present invention, and FIG. 2 is a front sectional view of the ceramic capacitor shown in FIG. The illustrated ceramic capacitor includes one ceramic capacitor element 1 and a pair of metal terminals 2 and 3. The ceramic capacitor element 1 has terminal electrodes 11 and 12 on both end surfaces facing each other in the direction of the length L.

Referring to FIG. 2, the ceramic capacitor element 1 has a large number (for example, 100 layers) of internal electrodes 101 and 102 inside a ceramic dielectric substrate 100. One end of the internal electrode 101 is connected to the terminal electrode 11,
The other end is an open end, one end of the internal electrode 102 is connected to the terminal electrode 12, and the other end is an open end.

The ceramic capacitor element 1, and the average linear expansion coefficient alpha ₁ to -55 ° C. from 25 ° C., when the average coefficient of linear expansion of up to 125 ° C. from 25 ° C. was alpha _2, alpha ₁ <
meet the α _2.

Of the metal terminals 2 and 3, the metal terminal 2 is a terminal
Connected to electrode 11. Metal terminal 3 is connected to terminal electrode 12
Have been. Metal terminals 2 and 3 are between -55 ° C and 125 ° C
Average coefficient of linear expansion up to β And β <1.3α_Two
And β > 0.7α₁Meet. Then this
These conditions will be described.

(A) β <1.3α_TwoAbout β ≤α_TwoAnd α_Two<Β <1.3α_TwoDivided into cases like
explain.

(A1) β ≤α_TwoFor β ≤α_TwoThe temperature range from 25 ° C to 125 ° C.
In the figure, the ceramic capacitor element 1 has a metal terminal
Since the elongation is larger than a few,
A compressive stress is generated in the sensor element 1. Therefore, β ≤
α_TwoWhen set to satisfy
Crack in ceramic capacitor element 1
Will not occur.

(A2) α_Two<Β <1.3α_TwoFor β > Α_TwoTemperature range from 25 ° C to 125 ° C
The ceramic capacitor element 1 has a metal terminal 2
Because the elongation is smaller than 3, ceramic capacitors
The element 1 generates a tensile stress. Where β <1.
3α_TwoWithin the range, the ceramic capacitor element 1
Even if tensile stress occurs, the stress is small, so
No racking occurs.

[0022] (B) 0.7α ₁ <by case analysis on the beta ≧ alpha ₁ and 0.7α ₁ <β _{<α 1} range for beta will be described.

(B1) β ≧ α₁In the case of -55 to 25 ° C, 25 ° C as a reference
Then, the ceramic capacitor element 1 and the metal terminals 2, 3
Will shrink with temperature. β ≧ α₁Place that is
In this case, the ceramic capacitor
Since the shrinkage of the element 1 becomes smaller,
A compressive stress is generated in the element 1. Therefore, ceramic
No crack is generated in the capacitor element 1.

(B2) 0.7α₁<Β <α₁If α₁> Β In the temperature range from -55 ° C to 25 ° C
Means that the ceramic capacitor element 1 has a metal terminal 2
3 shrinks more than ceramic capacitor element 1
Generates tensile stress. Where 0.7α₁<Β
If it is within the range, pull on the ceramic capacitor element 1.
Even if stress occurs, the stress is small, so cracks may occur.
Does not occur.

When the main component of the dielectric is barium titanate, the ceramic capacitor element 1 has α ₁ ≦ 7 ×
10 ⁻⁶ and α ₂ ≧ 9 × 10 ⁻⁶ . Dielectric substrate 1
When the main component of 00 is composed of a lead-based composite perovskite, α ₁ ≦ 2 × 10 ⁻⁶ and α ₂ ≧ 3 × 10 ⁻⁶ .
Therefore, the average linear expansion coefficient β of the metal terminals 2 and 3 is different when the main component of the dielectric substrate 100 is made of barium titanate and when it is made of a lead-based composite perovskite. It is necessary to determine α2 in consideration of the above condition.

A specific example of a lead-based composite perovskite (relaxer) -based porcelain dielectric material that can be used in the present invention is a composition formula of Pb (Mg _1/3 Nb _2/3 ) O ₃ -Pb (Mg _1/2 W _{1 / 2} ) Some are represented by O ₃ —PbTiO ₃ . This composition formula is generally expressed as PMN-
Expressed as PMW-PT. In addition, PMN-PNN-
PT, PMN-PZT-PT, PMN-PNN-PMW
Those expressed by a general formula such as -PT can also be used.

Preferably, the internal electrode 101 is formed such that a gap ΔL 1 is generated between the open end thereof and the terminal electrode 12. The internal electrode 102 has an open end and a terminal electrode 1.
1 so that an interval ΔL2 is generated. The intervals ΔL1 and ΔL2 are given by the shortest distance between the open ends and the terminal electrodes 11 and 12. Specifically, the interval △ L1
The line segment S11 drawn in the thickness direction of the ceramic dielectric substrate 100 from the tip of the hanging portion 121 attached to the front and back surfaces of the ceramic dielectric substrate 100 in the terminal electrode 12, and the line segment S11 Ceramic dielectric substrate 1
00 and a line segment S12 drawn in the thickness direction. The interval ΔL2 is set between the tip of the hanging portion 111 attached to the front surface and the back surface of the ceramic dielectric substrate 100 in the terminal electrode 11 and the ceramic dielectric substrate 10
It is given as an interval between a line segment S21 drawn in the thickness direction of 0 and a line segment S22 drawn in the thickness direction of the ceramic dielectric substrate 100 from the tip of the open end.

In FIG. 2, the ceramic capacitor element 1 has a horizontal arrangement in which the electrode surfaces of the internal electrodes 101 and 102 are parallel to the horizontal plane. The ceramic capacitor element 1 is rotated by about 90 degrees from the position shown in FIG. And internal electrode 1
The vertical arrangement may be such that the electrode surfaces of 01 and 102 are perpendicular to the horizontal plane.

The metal terminal 2 has one end 21 connected to the terminal electrode 11, a folded portion 22 at an intermediate portion, and a terminal portion 23 connected to the outside beyond the folded portion 22. The metal terminal 3 also has one end 31 connected to the terminal electrode 12, a folded portion 32 at an intermediate portion, and a terminal portion 33 connected to the outside beyond the folded portion 32. The metal terminals 2 and 3 are made of a material having low electric resistance and excellent spring properties. The thickness is not limited, but is typically about 0.1 mm. One end 21, 3 of metal terminal 2, 3
1 is connected to terminal electrodes 11 and 12 by bonding materials 4 and 5.

FIG. 3 is a partial sectional view showing a state where the ceramic capacitor shown in FIGS. 1 and 2 is mounted on a circuit board. The ceramic capacitor is mounted on the circuit board 70. Conductive patterns 71 and 72 are provided on the surface of the circuit board 70. The terminal portion 23 of the metal terminal 2 provided on the ceramic capacitor is
The terminal portion 33 of the metal terminal 3 is soldered to the conductor pattern 71 by solder 82.
Soldered to.

Here, in the ceramic capacitor according to the embodiment, at least one pair of metal terminals 2, 3
Are connected to the terminal electrodes 11 and 12 of the ceramic capacitor element 1 at one ends 21, 31 and have folded portions 22 and 32 at an intermediate portion, and a terminal connected to the outside beyond the folded portions 22 and 32. Parts 23 and 33 are provided. The metal terminals 2 and 3 having such a structure are connected to the terminal electrodes 11 of the ceramic capacitor element 1 from the terminal portions connected to the external conductor such as the substrate by the folded portions 22 and 32 provided at the intermediate portion.
The length (height) to one end connected to 12 is enlarged by the folded portions 22 and 32 provided at the intermediate portion.

For example, with reference to the terminal portions 23 and 33,
The height to the connection position of the metal terminals 2 and 3 by the joining materials 4 and 5 is the component height H in the conventional case without the folded portions 22 and 32, but in the present invention, the folded portion 2 is
The path length h to the top of 2, 32 becomes the length, and the height dimension is greatly increased. By adjusting the positions of the tops of the folded portions 22 and 32, the path length h can be suppressed to be lower than the component height H allowed for the ceramic capacitor having the entire length L.

Moreover, the folded portions 22 and 32 have a kind of spring action. Therefore, the bending and thermal expansion of the circuit board 70 are absorbed by the spring action of the folded portions 22 and 32, and the mechanical stress and the thermal stress generated in the ceramic capacitor element 1 can be reduced.
By selecting the structures and shapes of the folded portions 22 and 32, the distance from the terminal portions 23 and 33 attached to the circuit board 70 to the attachment portions to the terminal electrodes 11 and 12 of the ceramic capacitor element 1 can be increased by 2 to 5 times as compared with the related art. To prevent cracks from occurring in the ceramic capacitor element 1. Therefore, the aluminum circuit board 70
Even when the capacitor is used as a smoothing capacitor for a switching power supply, which is often mounted on a power supply, it is possible to avoid the occurrence of cracks and the danger of fire caused by the cracks.

The bending and thermal expansion of the circuit board 70 are
It is absorbed by the folded portions 22 and 32 provided on the metal terminals 2 and 3, and the folded portions 22 and 32
An increase in height can be avoided. In the case of the embodiment, the path length h exhibiting the spring action is determined by the folded portions 22, 32.
By adjusting the position of the top of the ceramic capacitor, it is possible to keep the overall length L lower than the component height H of the ceramic capacitor. Therefore, for the metal terminals 2 and 3, the terminal portions 23 and 33 on the circuit board 70 side are increased without increasing the component height H.
Of the circuit board 70 by the metal terminals 2 and 3 and the effect of absorbing thermal expansion are improved, and the mechanical stress and heat generated in the ceramic capacitor element 1 are increased. Stress can be reduced.

The folded portions 22 and 33 are located at positions where the tops are lower than the tops of the ceramic capacitor element 1. That is, h <H. With such a structure, the component height H can be kept low.

As the joining materials 4 and 5 for joining the metal terminals 2 and 3 and the terminal electrodes 11 and 12, a resin-containing conductive adhesive or solder can be used. Metal terminal 2,
According to the connection structure in which the connection electrodes 3 and the terminal electrodes 11 and 12 are connected by the bonding materials 4 and 5 made of a conductive adhesive containing a resin, almost no thermal shock is applied. There is no danger of cracks. Therefore, the reliability is improved.

The conductive adhesive preferably contains silver particles as a conductive component. When the particles are silver particles, the conductivity can be improved. In particular, flat silver particles having a particle diameter of 3 μm or more are preferable. With silver particles having such a particle size and shape, the filling amount of silver particles in the resin can be increased, and good conductivity can be secured. However, if the particle size of the silver particles is too large, the dispersibility in the resin becomes worse and the adhesive strength is reduced. Therefore, it is necessary to determine the maximum particle size of the silver particles to be used in consideration of the adhesive strength.

The ceramic capacitor according to the present invention comprises:
Since it is used in a wide temperature range of 55 to 125 ° C., a thermosetting resin having stable temperature resistance characteristics in such a temperature range is suitable as a resin constituting the conductive adhesive. ing. Specifically, epoxy resin type,
Examples include urethane resin-based, polyimide resin-based, or acrylic resin-based thermosetting resins.

As the joining materials 4 and 5 for connecting the metal terminals 2 and 3 and the terminal electrodes 11 and 12, solders other than the above-described conductive adhesives can be used. A solder having a melting point of 250 ° C. or more and 400 ° C. or less is particularly suitable.

As shown in FIG. 3, when the ceramic capacitor is soldered to the circuit board 70, a soldering process is performed at a temperature of about 250 ° C. In this soldering process, the metal terminals 2, 3 and the terminal electrodes 11, 12
The joining materials 4, 5 connecting the two must not melt. Therefore, it is necessary to use solder having a melting point of 250 ° C. or more as the bonding materials 4 and 5.

However, when solder having a melting point exceeding 400 ° C. is used as the joining material 4, 5, the metal terminals 2, 3
When soldering to the terminal electrodes 11 and 12, heat exceeding 400 ° C. is applied to the ceramic capacitor element 1, and a thermal crack occurs in the ceramic capacitor element 1. Therefore, a solder having a melting point of 400 ° C. or less is used.

When solder is used as the joining materials 4 and 5, the metal terminals 2 and 3 exhibit non-adhesiveness to the solder at least on the surface opposite to the external connection surfaces of the terminal portions 23 and 33. It is preferable to have a coating film. This will be described with reference to FIG.

In the embodiment shown in FIG. 4, the metal film 201 having good solderability is formed on both sides of the base 200, that is, on the side of the external connection surface to be soldered to the outside (outside). On the other side, a coating film 202 to which no solder adheres or hardly adheres is adhered. When such metal terminals 2 and 3 are used, solder does not adhere to the surfaces of the terminal portions 23 and 33 as shown in FIG. The space is not filled with solder. Therefore, the spring properties of the metal terminals 2 and 3 are not impaired.

The coating film 202 to which the solder does not adhere or hardly adheres may be adhered over the entire length of the metal terminals 2 and 3 or may be partially adhered including the terminal portions 23 and 33. Good. The coating film 202 may be formed of a metal oxide film or one selected from wax, resin, or silicone oil. As a means for forming the metal oxide film, a metal film which is easily oxidized on the surface of the base 200, for example, Ni
Alternatively, a method in which Cu or the like is adhered by plating and oxidized by natural leaving or the like can be adopted. The metal film 201
It can be configured as a plating film of Sn or Pb-Sn.

The description will be continued with reference to FIGS. 1 and 2 again.
The terminal portions 23 and 33 are arranged at intervals below the ceramic capacitor element 1. With such a structure, an increase in the area occupied by the substrate due to the terminal portions 23 and 33 can be suppressed, and a capacitor with a minimum mounting area can be obtained.

In the ceramic capacitor shown in FIGS. 1 and 2, the folded portion 22 of the metal terminal 2 includes a first bent portion 221 and a second bent portion 222. The first bent portion 221 is bent in a direction away from the terminal electrode 11, and the second bent portion 222 is bent at a distance from the first bent portion 221 in a direction parallel to the end face. The portion of the metal terminal 2 from the tip to the first bent portion 221 is connected to the terminal electrode 11.

Similarly, the folded portion 32 of the metal terminal 3 is
It includes a first bent portion 321 and a second bent portion 322. The first bent portion 321 is bent in a direction away from the terminal electrode 12, and the second bent portion 322 is bent at a distance from the first bent portion 321 in a direction parallel to the end face. The metal terminal 3 is first
The portion reaching the bent portion 321 is connected to the terminal electrode 12.

According to the above structure, the first bent portion 221,
321, the second bent portions 222 and 322 to the terminal portion 23,
The part that reaches 33 has a spring action,
The spring action can absorb the deflection and thermal expansion of the substrate.

The metal terminal 2 has a third bent portion 223. The third bent portion 223 includes the folded portion 22 and the terminal portion 23.
And partition. In addition, the metal terminal 3 has a third bent portion 32.
3 The third bent part 323 partitions the folded part 32 and the terminal part 33. Therefore, the first bent portion 221,
The portion from 321 to the third bent portions 223 and 323 is
It has a spring action, and the deflection and thermal expansion of the substrate can be absorbed by the spring action.

The metal terminals 2, 3 are bent at the third bent portions 223, 323 in a direction in which the terminal portions 23, 33 approach the ceramic capacitor element 1. The terminal portions 23 and 33 of the metal terminals 2 and 3 are arranged at intervals below the ceramic capacitor element 1, thereby suppressing an increase in the area occupied by the terminals 23 and 33 on the substrate and reducing the mounting area. Minimized.

Further, a gap ΔL1 is generated between the open end of the internal electrode 101 and the terminal electrode 12, and the internal electrode 102
In the case of the structure in which the gap ΔL2 is generated between the open end of the metal terminal and the terminal electrode 11, the interface between the metal terminal and the conductive adhesive, which is liable to crack, break, etc., and the conductive adhesive There is no overlap between the internal electrodes 101 and 102 near the application area. For this reason, the danger of causing a short circuit due to a crack and resulting ignition or the like is drastically reduced.

In FIG. 1 and FIG.
1, 321 and the second bent portions 222, 322 are approximately 9
Although it is bent at an angle of 0 degrees, the angle may be other than 90 degrees. Further, the first bent portions 221 and 321 and the second bent portions 222 and 322 may be bent into a shape having no definite angle, for example, an arc shape.

FIG. 5 is a front view showing another embodiment of the ceramic capacitor according to the present invention. In the figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals,
Description is omitted. In this embodiment, the bonding materials 4 and 5 are partially attached to the terminal electrodes 11 and 12. With such a structure, the path length h causing the spring action is:
The value obtained by adding the path length h1 from the terminal portions 23 and 33 to the second bent portions 222 and 322 and the path length h2 from the first bent portions 221 and 321 to the mounting portion (h = h1 + h).
2). This path length h is larger than the dimension of the component height H. Accordingly, for the metal terminals 2 and 3, the path length h from the board-side terminal portions 23 and 33 to the ceramic capacitor element mounting portion is increased without increasing the component height H, and the absorbing action against the bending and thermal expansion of the board. Can be improved.

FIG. 6 is a front sectional view showing another embodiment of the ceramic capacitor according to the present invention. In the figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the terminal electrodes 11,
12 is formed only on the side end surface. With such a structure, the distance between the internal electrode 101 and the terminal electrode 12 △ L
1 and the interval ΔL between the internal electrode 102 and the terminal electrode 11
2 may be set with reference to the side end surface of the ceramic dielectric substrate 100.
2 can be increased, and a larger acquisition capacity can be secured.

FIG. 7 is a front sectional view showing another embodiment of the ceramic capacitor according to the present invention. In the figure, the same components as those in FIG. In the embodiment shown in FIG. 7, two ceramic capacitor elements 110 and 120 are provided. The ceramic capacitor elements 110 and 120 are sequentially stacked, and the terminal electrodes 11 and 12 are connected in parallel by bonding materials 4 and 5. The terminal electrodes 11 and 12 are formed only on the side end surfaces of the ceramic dielectric substrate 100. According to this embodiment, a larger capacitance can be obtained as compared with FIG.

FIG. 8 is a front view showing another embodiment of the ceramic capacitor according to the present invention. In the figure, FIG.
2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the folded portion 22 of the metal terminal 2 includes an acute-angle bent portion 221, and the acute-angle bent portion 221 is bent at an acute angle in a direction substantially facing the end face of the ceramic capacitor element 1. Similarly, the folded portion 32 of the metal terminal 3 also includes an acute angle bent portion 321, and the acute angle bent portion 321 is bent at an acute angle in a direction substantially opposite to the end face of the ceramic capacitor element 1.

According to the above-described structure, the bending positions 221 and 32 are similar to those of the ceramic capacitors shown in FIGS.
The portion from 1 to the terminal portions 23 and 33 has a spring action, and the deflection and thermal expansion of the substrate can be absorbed by the spring action.

FIG. 9 is a front view showing another embodiment of the ceramic capacitor according to the present invention. In the figure, FIG.
2 are denoted by the same reference numerals, and description thereof will be omitted. Folded part 2 of metal terminals 2 and 3
2, 32 are bent in an arc shape. In this embodiment, the same operation and effect as those of the embodiment of FIGS.

FIG. 10 is a perspective view showing another embodiment of the ceramic capacitor according to the present invention, and FIG. 11 is a front view of the ceramic capacitor shown in FIG. In the figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the folded portion 22 of the metal terminal 2 includes an acute angle bent portion 221, and the acute angle bent portion 221 includes the ceramic capacitor elements 110 and 120.
Is bent at an acute angle in a direction substantially opposite to the end face of the horn. Similarly, the folded portion 32 of the metal terminal 3 also includes an acute angle bent portion 321, and the acute angle bent portion 321 is bent at an acute angle in a direction substantially opposite to the end face of the ceramic capacitor element 1. Holes 24 are provided in the metal terminals 2 and 3. In this embodiment, the same operation and effect as those of the embodiment of FIGS.

In any of the above embodiments, the metal terminal
Each of 2, 3 is the average from -55 ° C to 125 ° C
Linear expansion coefficient β With respect to β <1.3α_TwoMeet or
One, β > 0.7α₁Meet. As a result,
Long-term in environments with drastic temperature changes in the range of 125 ° C
It does not crack even if it is used for a long time,
No ceramic capacitors are obtained. Next, on this point
This will be described with reference to crack occurrence rate test data.

Examples 11 to 13 As a ceramic capacitor element, a rated voltage of 25 V, a capacitance of 22 μF, and a temperature characteristic E of 5.6 × 5.0 ×
A 2.3 mm lead-based dielectric was prepared. The above-mentioned ceramic capacitor element has a Ag-P inside a lead-based ceramic dielectric.
and an internal electrode made of Ag paste, which is an electrode baked with an Ag paste containing glass bullets, on both opposite ends of the ceramic dielectric. The lead-based ceramic capacitor element has an average linear expansion coefficient of −55 to 25 ° C. and an average linear expansion coefficient α1 = 0.5 to 2 × 10 ⁻⁶ , 25 to 125
The average coefficient of linear expansion at 2 ° C. was α2 = 4.2 × 10 ⁻⁶ .

Two of the above ceramic capacitor elements are
The terminal electrodes were aligned and overlaid, and the terminal electrodes were fixed by applying a conductive adhesive in which silver powder was dispersed. Next, only the part bent inside the metal plate having a thickness of 0.1 mm, which was subjected to silver plating (intermediate layer was nickel, Ni-Ag), was placed on the lower electrode side of the two-tiered ceramic capacitor. At a predetermined pressure. In this state,
The conductive adhesive was thermally cured by heating at 150 ° C. for 1 hour to produce a composite ceramic capacitor in which two ceramic capacitor elements and metal terminals were fixed at the ends. The shape of the metal terminal and the structure for attaching the metal terminal to the ceramic capacitor element were as shown in FIGS.

As the metal terminals 2 and 3, the average linear expansion coefficient
Samples of Examples 11 to 13 using different metal materials
I got The material of the metal terminals 2 and 3 is
In Example 12, a 42 alloy (Fe 58 wt.
%, Ni 42 wt%).
Was used. The average linear expansion coefficient β of chromium of Example 11 is
4.5 × 10^-6Average linear expansion of 42 alloy of Example 12
The coefficient β is 4.4 × 10^-6It is. Therefore, Example 11,
0.7α for both 12 and 13₁<Β and β <
1.3α_TwoMeet.

Comparative Examples 11 to 25 Ceramic capacitors were prepared in the same manner as in Examples 11 to 13 except that the materials of the metal terminals 2 and 3 were changed. The materials and average linear expansion coefficients β of the metal terminals 2 and 3 used in Comparative Examples 11 to 25 are as shown in Table 1.

Each of the samples of Examples 11 to 12 and Comparative Examples 11 to 25 was soldered and fixed to an aluminum substrate, and a thermal shock was applied to evaluate the occurrence of cracks. The test conditions performed are as follows.

(1) Thermal shock test at low temperature (−55 to 25)
C. Heat cycle test) (1-1) 100 samples each of this product were soldered to an aluminum substrate and subjected to a thermal shock in a thermal shock test tank. (1-2) The heat cycle is from −25 ° C. (room temperature) to −5.
Rapid cooling to 5 ° C (cooling shock test tank), then 25 ° C (room temperature)
The cycle of returning to was set as one cycle. (1-3) The heat cycle is performed 500 times for each sample. (1-4) The product was removed from the aluminum substrate, an appearance test was performed, and electrical characteristics were examined. Then, the product was polished to evaluate internal cracks.

(2) High-temperature side thermal shock test (25 to 125)
(2-1) Heat cycle test at ℃) (2-1) Solder 100 pieces each of this product sample to an aluminum substrate and give a thermal shock in a thermal shock test tank. (2-2) The heat cycle is from 25 ° C. (room temperature) to 12
A cycle in which the temperature is rapidly raised to 5 ° C. and then rapidly cooled to 25 ° C. (room temperature) is defined as one cycle. (2-3) The heat cycle was performed 500 times for each sample. (2-4) The product was removed from the aluminum substrate, an appearance test was performed, and electrical characteristics were examined. Then, the product was further polished to evaluate internal cracks.

Table 1 shows the occurrence of cracks after the heat cycle in Examples 11 to 13 and Comparative Examples 11 to 25. As shown in Table 1, for lead-based ceramic capacitors,
In Comparative Examples 11 to 25, cracks do not occur in the thermal shock test at 25 → −55 ° C., but cracks occur at a probability of 54% to 100% in the thermal shock test at 25 → 125 ° C. In contrast, Examples 11 to 13 according to the present invention
In the thermal shock test at 25 → −55 ° C., and 2
No cracks were observed in any of the thermal shock tests at 5 to 125 ° C.

Next, for a ceramic capacitor using a general barium titanate-based dielectric material, the occurrence of cracks accompanying a thermal shock test was verified. Samples subjected to the verification are referred to as Examples 31 to 39 and Comparative Examples 31 to 39.
The structure of the sample is the same as that of the lead-based ceramic capacitor described above.

Metals used in Examples 31 to 39
The materials of the terminals 2 and 3 and the average thermal expansion coefficient β are shown in Table 2.
And 0.7α₁<Β and β <
1.3α_TwoMeet.

Comparative Examples 31 to 39 Examples 31 to 39 were made except that the material of the metal terminals 2 and 3 was changed.
Comparative Examples 31 to 39 Ceramic Capacitors
It was created. Metals used in Comparative Examples 31 to 39
The materials of the terminals 2 and 3 and the average coefficient of linear expansion β are shown in Table 2.
And 0.7α₁<Β and β <
1.3α_TwoDoes not meet. Comparative Example 39 had 0.7α₁<
satisfies β, but β <1.3α_TwoDoes not meet
No.

Each of the samples of Examples 31 to 39 and Comparative Examples 31 to 39 was soldered and fixed to an aluminum substrate, and a thermal shock was applied to evaluate the occurrence of cracks. The thermal shock test conditions are the same as those of the lead-based ceramic capacitor described above.

Examples 31 to 39 and Comparative Examples 31 to 39
Table 2 shows the occurrence of cracks after the heat cycle.
Show.As shown in Table 2, barium titanate-based ceramic capacitors
In the case of a densa, in Comparative Examples 31 to 38, 25 → −55 ° C.
Cracks did not occur in the thermal shock test of
87% to 100% probability in thermal shock test from 5 to 125 ° C
Cracks. 0.7α₁<Satisfies β
Also β <1.3α_TwoIn Comparative Example 39 which does not satisfy
In the thermal shock test at 5 → -55 ° C, there is a probability of 4%
Generate racks.

On the other hand, Examples 31 to 31 according to the present invention
In No. 39, no crack was observed in both the thermal shock test at 25 → −55 ° C. and the thermal shock test at 25 → 125 ° C.

Other Embodiments The internal electrodes of a ceramic capacitor element containing Ni as a main component were applied to Examples 11 to 13 and 31 to 39 to verify crack generation. Verification result, Example 1
Almost no significant difference was observed for all of 1 to 13 and 31 to 39. Therefore, by applying an internal electrode containing Ni as a main component to a ceramic capacitor element, it is possible to provide an inexpensive and reliable ceramic capacitor having corrosion resistance, little change over time.

[0076]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a ceramic capacitor that can reliably prevent cracks, breakage, and the like from occurring in the ceramic capacitor element. (B) A ceramic capacitor capable of reducing thermal stress and mechanical stress in a ceramic capacitor element can be provided.

[Brief description of the drawings]

FIG. 1 is a front view of a ceramic capacitor according to the present invention.

FIG. 2 is a front sectional view of the ceramic capacitor shown in FIG. 1;

FIG. 3 is a partial cross-sectional view showing a state when the ceramic capacitor shown in FIGS. 1 and 2 is mounted on a circuit board.

FIG. 4 is an enlarged sectional view showing an example of a metal terminal used in the ceramic capacitor according to the present invention.

FIG. 5 is a front view showing another embodiment of the ceramic capacitor according to the present invention.

FIG. 6 is a front sectional view showing still another embodiment of the ceramic capacitor according to the present invention.

FIG. 7 is a front sectional view showing still another embodiment of the ceramic capacitor according to the present invention.

FIG. 8 is a front view showing still another embodiment of the ceramic capacitor according to the present invention.

FIG. 9 is a front view showing still another embodiment of the ceramic capacitor according to the present invention.

FIG. 10 is a perspective view showing still another embodiment of the ceramic capacitor according to the present invention.

FIG. 11 is a front view showing still another embodiment of the ceramic capacitor shown in FIG. 10;

FIG. 12 is a front view showing a conventional ceramic capacitor.

[Explanation of symbols]

1, 110-140 Ceramic capacitor element 2, 3 Metal terminal 21, 31 One end

Claims (10)

[Claims] 1. At least one ceramic capacitor
Ceramic including element and at least one pair of metal terminals
A capacitor, wherein the ceramic capacitor elements are provided on opposite side end faces.
A terminal electrode, wherein each of said metal terminals is connected to one of said terminal electrodes
The ceramic capacitor element is 25 ° C to -55 ° C.
The average linear expansion coefficient up to α₁And 25 ° C to 125 ° C
The average linear expansion coefficient up to α_TwoAnd α₁<Α_TwoFull
However, the metal terminal has an average linear expansion from -55 ° C to 125 ° C.
The tension coefficient is β And β <1.3α_TwoMeet or
One, β > 0.7α₁Ceramic capacitors. 2. The ceramic capacitor according to claim 1, wherein a main component of the dielectric is barium titanate, and α ₁ ≦ 7 × 1.
A ceramic capacitor wherein 0 ^-6 and α ₂ ≧ 9 × 10 ^-6 . 3. The ceramic capacitor according to claim 1, wherein the main component of the dielectric is a lead-based composite perovskite, and α ₁ ≦
A ceramic capacitor in which 2 × 10 ⁻⁶ and α ₂ ≧ 3 × 10 ⁻⁶ . 4. The ceramic capacitor according to claim 1, wherein the ceramic capacitor element has an internal electrode containing Ni as a main component. 5. The ceramic capacitor according to claim 1, wherein each of said metal terminals has a leading end connected to one of said terminal electrodes and a middle part connected to an intermediate part. A ceramic capacitor having a folded portion and having a terminal portion connected to the outside behind the folded portion. 6. The ceramic capacitor according to claim 1, wherein the metal terminal and the terminal electrode are connected by a conductive adhesive containing a resin. Are ceramic capacitors. 7. The ceramic capacitor according to claim 6, wherein the conductive adhesive has a conductive component:
A ceramic capacitor containing silver particles having a particle size of 3 μm or more. 8. The ceramic capacitor according to claim 6, wherein the resin of the conductive adhesive is an epoxy resin, a urethane resin, a polyimide resin, or an acrylic resin thermosetting. Ceramic capacitor mainly composed of at least one selected from conductive resins. 9. The ceramic capacitor according to claim 1, wherein the metal terminal and the terminal electrode are connected by solder. 10. The ceramic capacitor according to claim 9, wherein the solder has a melting point of 250 ° C. or higher.
Ceramic capacitor in the range below 00 ° C.