JPH1025164A - Burning method of laminated ceramic electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for burning a laminated ceramic electronic part, capable of reducing the peeling or scratching of an outside electrode and burning many product having a uniform shape, color and characteristic by loading a specific laminated element for burning [an (a) element] in a rotatable sheath having a penetrating hole, burning under a non-oxidizing atmosphere with heating at a higher temperature than that of curing of the outside electrode paste and also starting the rotation of the sheath from a lower temperature than that of initiating the sintering of the (a) element. SOLUTION: This method for burning a laminated ceramic electronic part is to start the rotation of a sheath at 300-1000 deg.C, at a rotation speed of capable of avoiding the flying out of the laminated ceramic element for burning from a penetrating hole in the sheath with loading a similar powder in the sheath. A paste for an inside electrode and an outside electrode consists of a metal oxide (e.g.; NiO) as a main component. As to the burning process shown in the figure, 1-100ppm oxygen concentration is maintained in a range of just after the start of burning to 100-1200 deg.C, and the oxygen concentration is lowered to 10<-10> -10<-20> atm simultaneously with the beginning of the volume contraction due to the sintering of an (a) element to metallize the outside electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for firing a multilayer ceramic electronic component such as a multilayer varistor.

[0002]

2. Description of the Related Art In a conventional method for firing a multilayer ceramic electronic component, firing is performed without rotating an element to be fired in a furnace.

[0003]

In the above firing method, when a large number of elements to be fired are put into the sheath, the heat and atmosphere transmitted to the individual elements to be fired become non-uniform, and as a result, the characteristics after firing vary. However, there is a problem that the problem easily occurs.

Accordingly, the present invention is to make the heat history and atmosphere history transmitted to each element to be fired during firing uniform by rotating the sheath, and to specify the rotation start temperature to prevent external electrode defects. Reduce, always uniform shape, color,
It is an object of the present invention to provide a large number of multilayer ceramic electronic components having characteristics.

[0005]

In order to achieve this object, a method for firing a multilayer ceramic electronic component according to the present invention comprises applying an external electrode paste to a multilayer ceramic fired element in which an internal electrode and a ceramic sheet are stacked. Next, the multilayer ceramic fired element is put into a rotatable sheath having at least one through-hole, and when fired in a non-oxidizing atmosphere, the temperature of the external electrode paste is higher than a temperature at which the external electrode paste is hardened and the multilayer ceramic fired element is fired. Starting the rotation of the sheath from a temperature lower than the temperature at which the element to be fired starts sintering,
According to this method, defects such as peeling and fraying of the external electrode are reduced, and since the sheath is rotating, a uniform shape,
It becomes possible to fire a large number of multilayer ceramic electronic components having different colors and characteristics, and the above object can be achieved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is to apply an external electrode paste to a laminated ceramic fired element in which internal electrodes and ceramic sheets are alternately laminated,
Next, the multilayer ceramic fired element is put into a rotatable sheath having at least one through hole, and then, when the multilayer ceramic fired element is fired in a non-oxidizing atmosphere, the temperature at which the external electrode paste is hardened is set. This is a firing method for a multilayer ceramic electronic component in which the rotation of the sheath is started at a high temperature and a temperature lower than the temperature at which the multilayer ceramic fired element starts sintering. In addition, a multilayer ceramic electronic component having a uniform shape, color, and characteristics can always be fired according to the atmosphere history.

According to a second aspect of the present invention, there is provided the method for firing a multilayer ceramic electronic component according to the first aspect, wherein the rotation start temperature of the sheath is in a range of 300 ° C. to 1000 ° C., thereby reducing defects of external electrodes. In addition, a multilayer ceramic electronic component having a uniform shape, color, and characteristics can be constantly fired by uniform heat history and atmosphere history.

The invention according to claim 3 is the method for firing a multilayer ceramic electronic component according to claim 1, wherein the rotational speed of the sheath is such that the multilayer ceramic element to be fired does not jump out of the through hole of the sheath. , Reduce the failure of external electrodes,
With uniform heat history and atmosphere history, always uniform shape,
The multilayer ceramic electronic component having the color and characteristics can be fired.

According to a fourth aspect of the present invention, there is provided the method for firing a multilayer ceramic electronic component according to the first aspect of the present invention, wherein the powder is mixed into the sheath and fired to reduce the noise between the external electrodes. Also, the rotation of the multilayer ceramic fired element in the sheath can be made smooth.

According to a fifth aspect of the present invention, there is provided the multilayer ceramic electronic component according to the first aspect, wherein the internal electrode and the external electrode paste of the multilayer ceramic fired element are formed of a material containing a metal oxide as a main component. In the firing method, firing is performed in a non-oxidizing atmosphere to reduce the metal oxide and metallize it, thereby forming an electrode.

According to a sixth aspect of the present invention, there is provided the method for firing a multilayer ceramic electronic component according to the fifth aspect, wherein NiO is used as the metal oxide. And a Ni electrode is formed.

According to a seventh aspect of the present invention, the temperature at which the multilayer ceramic element starts sintering is lower than the first firing atmosphere in a temperature range lower than the temperature at which the multilayer ceramic element starts sintering. 2. The method for firing a multilayer ceramic electronic component according to claim 1, wherein the second firing atmosphere in a higher temperature range has a lower oxygen concentration than the second firing atmosphere. Can be prevented.

[0013] According to the present invention, the switching temperature between the first baking atmosphere and the second baking atmosphere is set at 1000 ° C.
The firing method of a multilayer ceramic electronic component according to claim 7, which is performed at a temperature of up to 1200 ° C., which can prevent delamination inside the multilayer ceramic element to be fired due to volume shrinkage and disconnection of an electrode.

According to a ninth aspect of the present invention, the oxygen concentration in the first firing atmosphere is 1 to 100 ppm and the oxygen concentration in the second firing atmosphere is 10 ^-10 to 10 ^-20 atm. And firing of the multilayer ceramic electronic component due to volume shrinkage and disconnection of the electrodes can be prevented.

Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

In FIG. 3, reference numeral 1 denotes a multilayer varistor element.
A plurality of internal electrodes 2 are provided inside the ceramic sheet 1a.
And external electrodes 3 are provided at both ends thereof. Ceramic sheet 1a
Is composed mainly of SrTiO ₃ and Nb as a sub-component.
It is formed by adding ₂ O ₅ , Ta ₂ O ₅ , MnO ₂ , SiO _{2 and the} like. The internal electrode 2 is a metal containing Ni as a main component, NiO as a main component, and Li as a subcomponent.
It is formed by adding ₂ CO ₃ and reacting. Further, the external electrode 3 is formed such that the lower layer 3a is a metal mainly composed of Ni, mainly composed of NiO, and Li ₂ CO ₃ is added and reacted as an auxiliary component, and the upper layer 3b is formed of Ag, Ag. −
It is formed of Pb or the like.

FIG. 4 shows a manufacturing process. As shown in (4), a ceramic sheet 1a was produced by mixing raw materials, calcining, pulverizing, slurrying, and sheet forming.

Next, the ceramic sheet 1a and the internal electrode 2
Were laminated (5) and cut (6) to obtain a laminate. afterwards,
After debubbling and calcining in air (7) and chamfering (8), only the exposed end face of the internal electrode 2 of the laminate is removed.
A Ni external electrode paste to be the lower layer 3a was applied (9).

Thereafter, as shown in FIG. 2, the laminated varistor element 1 coated with the lower layer 3a of the external electrode is packed in a cylindrical sheath 13 made of alumina and having through holes at both end surfaces. Baking powder of the same composition as
The ground powder was mixed as a powder. Thereafter, the sheath 13 was set in a rotatable tubular furnace 14 made of alumina and fired in a non-oxidizing atmosphere (10) under the conditions shown in FIG.

At this time, the inside of the tubular furnace 14 was placed around the sheath 13 and heat insulating materials 15 were placed on both sides thereof. Also,
Atmospheric gas flowed in from the inlet 16 and flowed out from the outlet 17.

According to this method, the heat insulating effect inside the tubular furnace 14 and the stability of the atmosphere gas are obtained, and as a result, the firing can be performed with good reproducibility.

After firing, an Ag external electrode paste to be the upper layer 3b is applied (11) on the lower layer 3a, and the Ag external electrode paste is applied in the air.
70 for re-oxidation of the multilayer varistor element 1 simultaneously with baking
The multilayer varistor element 1 shown in FIG. 3 was manufactured by heating (12) in a temperature range of 0 to 900 ° C.

In this embodiment, the laminated varistor element 1 has a width × length × height (W × L × T) of 1.2.
The shape was 5 × 2.0 × 1.0 (mm), and the processing amount in firing in a non-oxidizing atmosphere (10) was 20,000 to 50,000 / batch.

In the multilayer varistor element 1 obtained from the first embodiment, variations in dimensions, color unevenness, and electrical characteristics among the multilayer varistor elements 1 were very small. Further, no defect such as peeling of the Ni external electrode of the lower layer 3a and blurring occurred. When the inside of the multilayer varistor element 1 was observed, delamination and the Ni internal electrode 2 were observed.
No defects such as cuts were found.

Originally, if the Ni external electrode of the lower layer 3a is emphasized, if the sheath 13 is not rotated, that is, it is stationary, or if it is baked at a high temperature of 1000 ° C. or more, a good product without peeling or fraying can be obtained. Multilayer varistor element 1
When importance is placed on the variation in the shape, color, and characteristics of the element, firing the element while the sheath 13 is rotated results in a uniform heat history and atmosphere history for each element to be fired.

Therefore, when the laminated varistor element 1 to which the Ni external electrode paste of the lower layer 3a is applied in advance is fired in a large amount as in the first embodiment, the method of rotating the sheath 13 becomes very important.

Therefore, in the first embodiment, the above-mentioned problem was solved by roughly taking two improvement measures.

First, the rotation start temperature of the sheath 13 is set to 3
Second, the switching of the oxygen concentration in the non-oxidizing atmosphere is performed at 1000 ° C. to 1200 ° C.
It is to be carried out within the range.

The former mainly serves to reduce defects such as peeling or fraying of the Ni external electrode of the lower layer 3a and variations in the shape, color and characteristics of the multilayer varistor element 1. When the rotation is started from a state in which the rotation start temperature of the sheath 13 is less than 300 ° C. and the applied Ni external electrode paste of the lower layer 3 a is not yet cured, the sheath is peeled off or adheres to the inner wall of the multilayer varistor element 1 or the sheath 13. The phenomenon of blurring is likely to occur. Conversely, the rotation start temperature of the sheath 13 is set to 1000 ° C.
If the temperature is higher than the temperature, that is, from the temperature range in which the multilayer varistor element 1 starts sintering, the variation in the shrinkage rate and the reduction rate of the multilayer varistor element 1 tends to increase.

Further, the latter switching of the oxygen concentration in the non-oxidizing atmosphere mainly affects the internal structural delamination of the multilayer varistor element 1 and the reduction of the Ni internal electrode 2 cut. Immediately after the start of firing, in the region from 1000 ° C to 1200 ° C,
By firing in a non-oxidizing atmosphere having an oxygen concentration of about 1 to 100 ppm, volume shrinkage due to metallization of the applied Ni internal electrode 2 is suppressed, and a region exceeding 1000 ° C. to 1200 ° C., that is, firing of the multilayer varistor element 1 is performed. At the same time as volume shrinkage due to sintering starts, the oxygen concentration is increased to 10 ^-10 to 10 ^-20.
It is reduced to atm, and the Ni internal electrode 2 and the Ni external electrode of the lower layer 3a are metallized. By performing this method, delamination and breakage of the Ni internal electrode 2 can be reduced. Also,
By lowering the oxygen concentration after the sheath 13 is rotated, the effect of reducing the exfoliation of the Ni external electrode of the lower layer 3a can be simultaneously obtained.

Here, items considered to be important in the firing method according to the present invention will be described.

(1) In order to prevent exfoliation of the Ni external electrode of the lower layer 3a, it is desirable to start the rotation of the sheath 13 from a temperature range lower than the oxygen concentration is lowered.

(2) When the number of rotations is 1 to 4 r / min, the rotation of the multilayer varistor element 1 at the sheath 13 tends to occur smoothly.

(3) Characteristics are more stable when the non-oxidizing atmosphere gas does not directly hit the multilayer varistor element 1.

(4) The maximum input amount of the multilayer varistor element 1 is about 1/3 to 1/2 of the volume of the sheath 13. If the input amount is further increased, the flow of the non-oxidizing atmosphere gas becomes worse, or There is a tendency that rotation of the multilayer varistor element 1 hardly occurs.

(5) Mixing powder is effective to prevent crackling between the Ni external electrodes of the lower layer 3a. This powder has the same composition as the laminated varistor element 1 and a particle size of 1
A relatively coarse powder of 00 to 500 μm is preferred.

(6) Although NiO was used as the electrode paste for the internal electrodes 2 and the external electrodes of the lower layer 3a, Ni is used as a starting paste in consideration of volume shrinkage due to metallization in a non-oxidizing atmosphere firing (10). It is considered that the adhesiveness to the ceramic sheet 1a and the added L
As a result of considering the effect of i ⁺ ions (valence control), manufacturing cost, and the like, it is better to use NiO as a metal oxide.
At this time, the average particle diameter of NiO is desirably 0.7 to 1.0 μm.

In the first embodiment, the multilayer varistor element 1 has been described as an example. However, the present invention is not limited to a multilayer capacitor and a multilayer ceramic thermistor if the multilayer body is coated with external electrodes in advance and fired in a non-oxidizing atmosphere. The present invention can be applied to a firing method for a multilayer ceramic electronic component such as the above.

[0039]

As described above, according to the present invention, the temperature at which the external electrode paste is hardened when the multilayer ceramic fired element coated with the external electrode paste is put into a rotatable sheath and fired in a non-oxidizing atmosphere. By starting rotation of the sheath at a higher temperature, defects such as exfoliation and fraying of external electrodes are reduced, and since the sheath is rotating, a large number of multilayer ceramic electronic components with uniform shape and color characteristics are fired. It becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a firing step according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a method of filling the sheath in one embodiment of the present invention.

FIG. 3 is a sectional view of a multilayer varistor element according to an embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of the laminated varistor element in one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer varistor element 2 Internal electrode 3a Lower layer 13 Saya

Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication // C04B 35/495 C04B 35/64 CB 35/00 J

Claims (9)

[Claims] An external electrode paste is applied to a multilayer ceramic fired element in which internal electrodes and ceramic sheets are alternately stacked, and then the multilayer ceramic fired element is placed in a rotatable sheath having at least one through hole. ,
Thereafter, when firing the multilayer ceramic fired element in a non-oxidizing atmosphere, the rotation of the sheath from a temperature higher than the temperature at which the external electrode paste hardens and lower than the temperature at which the multilayer ceramic fired element starts sintering. Starting method of firing multilayer ceramic electronic components. 2. The rotation start temperature of the sheath is 300 ° C. to 10 ° C.
2. The method for firing a multilayer ceramic electronic component according to claim 1, wherein the temperature is in the range of 00C. 3. The method for firing a multilayer ceramic electronic component according to claim 1, wherein the rotational speed of the sheath is such that the multilayer ceramic element to be fired does not protrude from the through hole of the sheath. 4. The method for firing a multilayer ceramic electronic component according to claim 1, wherein the powder is mixed into the sheath and fired. 5. The method for firing a multilayer ceramic electronic component according to claim 1, wherein the internal electrode and the external electrode paste of the multilayer ceramic fired element are formed of a material containing a metal oxide as a main component. 6. The method for firing a multilayer ceramic electronic component according to claim 5, wherein NiO is used as the metal oxide. 7. A first firing atmosphere in a temperature range lower than a temperature at which the multilayer ceramic fired element starts sintering, and a first firing atmosphere in a temperature range higher than a temperature at which the multilayer ceramic fired element starts sintering. 2. The method for firing a multilayer ceramic electronic component according to claim 1, wherein the firing atmosphere of (2) has a lower oxygen concentration. 8. The method for firing a multilayer ceramic electronic component according to claim 7, wherein the switching temperature between the first firing atmosphere and the second firing atmosphere is between 1000 ° C. and 1200 ° C. 9. The oxygen concentration of the first firing atmosphere is 1 to 1
At 00 ppm, the oxygen concentration in the second firing atmosphere is 10 ⁻¹⁰ to
The method for firing a multilayer ceramic electronic component according to claim 8, wherein the firing temperature is 10 ^-20 atm.