JP2001023855A - Manufacture of multilayer ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing superior multilayer ceramic electronic component, capable of preventing the occurrence of a structural defect like delamination and having small firing distortions. SOLUTION: The multilayer ceramic electronic component is made by alternately laminating a plurality of ceramic green sheets 1 and internal electrodes 2 to form a laminated green block and then cutting the laminated green block to a predetermined form and firing it. Here, the internal electrode 2 is composed of a first internal electrode 2a, formed of a conductive paste on the surface of the ceramic green sheet 1 and a second internal electrode 2b, formed of the conductive paste in a thickness of C, such that it overlaps only the outer peripheral portion A of the first internal electrode 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a multilayer ceramic electronic component.

[0002]

2. Description of the Related Art A conventional method of manufacturing a multilayer ceramic electronic component will be described by taking a multilayer ceramic capacitor as an example.

[0003] First, ceramic dielectric powder, an organic binder, and an organic solvent are weighed in predetermined amounts and then kneaded to prepare a ceramic slurry.

Next, a ceramic slurry is applied to the surface of a carrier film made of a polyethylene terephthalate film to produce a ceramic green sheet.

Next, an internal electrode is formed on the surface of the ceramic green sheet by a gravure printing method or the like using a conductive paste made of a conductive metal powder such as silver-palladium, an organic solvent, a binder, etc., and then dried. An electrode is formed to produce a ceramic green sheet.

Thereafter, a predetermined number of ceramic green sheets on which internal electrodes are formed are repeatedly laminated by heating and pressing to produce a laminated green block.

Next, a green chip is manufactured by cutting the laminated green block into a predetermined shape. The obtained green chip has a structure in which one end of an internal electrode is alternately exposed at different end faces on both end faces opposed to each other in the longitudinal direction with a ceramic layer interposed therebetween.

Then, after firing the green chip at a predetermined temperature, a conductive paste containing silver or the like as a main component is applied to both exposed end surfaces of the internal electrode and baked to form a multilayer ceramic having an external electrode. Complete the capacitor.

[0009]

When the internal electrodes are formed by using the conductive paste composed of the conductive metal powder, the organic solvent, the binder and the like in the above-mentioned manufacturing method, the printing method and the viscosity suitable for the conductive paste or the internal resistance are determined. Depending on the size of the electrode, the outer peripheral portion (A) of the internal electrode is thinner than the central portion (B) as shown in FIG. For this reason, the laminability of the ceramic green sheets on which the internal electrodes are formed is deteriorated, and it is difficult to perform multi-lamination. Further, if the thickness of the internal electrode is reduced to alleviate this, disconnection of the internal electrode is likely to occur. In particular, recent multilayer ceramic capacitors require ceramic green sheets to be thinner and smaller in size due to the demand for small size and large capacity, and multi-layered ceramic green sheets are required. The adhesiveness of the internal structure decreases, and problems such as delamination of internal structural defects are likely to occur. Similarly, in the case of a middle-layered product, delamination or cracks occur inside the element after firing,
There are problems such as complicated process condition management and reduced product yield.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method for forming an internal electrode on a ceramic green sheet surface using a conductive paste comprising a conductive metal powder, an organic solvent, a binder and the like. In order to correct the thickness of the outer peripheral portion of the primary internal electrode, a secondary internal electrode is formed on the outer peripheral portion where the thickness of the primary internal electrode is thin, and the intended purpose is achieved by making the thickness of the entire internal electrode uniform. Can be achieved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention relates to a multilayer ceramic electronic component in which a laminated green block in which a plurality of ceramic green sheets and internal electrodes are alternately laminated is cut into a predetermined shape and then fired. Forming a primary internal electrode on the ceramic green sheet surface using a conductive paste, drying the internal electrode, and then forming a secondary internal electrode using a conductive paste so as to overlap only with the outer peripheral portion of the primary internal electrode. A method of manufacturing a ceramic electronic component, in which the secondary internal electrode is overlapped only on the outer peripheral portion of the primary internal electrode to correct the thinness of the outer peripheral portion of the formed primary internal electrode, so that the whole has a uniform thickness. Since the entire thickness of the internal electrode is uniform to form the internal electrode, the thickness of the entire internal electrode can be reduced.
By using a ceramic green sheet with a reduced thickness of the entire internal electrode, the thickness step at the peripheral portion of the internal electrode is reduced, and when the ceramic green sheets on which the internal electrodes are formed are multi-layered, the internal electrode and the ceramic green sheet are used. In addition, the adhesiveness between the ceramic green sheets is improved, and the occurrence of delamination of the sintered body can be prevented. Further, the obtained sintered body has a small internal strain between the internal electrode forming portion and the internal electrode non-forming portion, and has high thermal shock resistance and high reliability.

According to a second aspect of the present invention, a primary internal electrode and a secondary internal electrode are formed using a conductive paste made of a conductive metal powder, an organic solvent, a binder, a common material (a material for forming a ceramic layer), and the like. 2. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein each of the electrodes is formed by using a gravure printing method. In order to form a secondary internal electrode so as to overlap an outer peripheral portion of the formed primary internal electrode, the method comprises the steps of: In addition, the printing position accuracy of the secondary internal electrode is important, but as a desirable printing method, formation by a metal roll such as a gravure printing method with less deformation and distortion of a printed image is optimal.

According to a third aspect of the present invention, the conductive paste of the secondary internal electrode is obtained by adding a common material (a material for forming a ceramic layer) to the conductive metal powder by up to 50%. 2. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein an outer peripheral portion of the internal electrode is an interface in which a thickness step significantly appears with a ceramic green sheet surface on which the internal electrode is not formed. It is difficult to apply the pressing force evenly when manufacturing the green block, but to alleviate this, by adding a common material to the conductive paste used for the secondary internal electrode, the ceramic green sheet and the internal electrode can be combined in the firing process. This improves the conformability, suppresses the generation of stress at the interface, and can provide a stable sintered body. It is also possible to use a conductive paste for the primary internal electrode to which a common material is added.

According to a fourth aspect of the present invention, the thickness after the formation of the secondary internal electrode is made to overlap only with the outer peripheral portion of the primary internal electrode so as to be equal to the thickness of the central portion of the primary internal electrode. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the thickness of the outer peripheral portion of the primary internal electrode is reduced by forming the secondary internal electrode so that the thickness of the entire internal electrode becomes substantially uniform after the formation of the secondary internal electrode. For correction, the secondary internal electrode is formed so as to overlap only with the outer peripheral portion thereof. The thickness of the entire internal electrode after the formation of the secondary internal electrode becomes uniform, and the internal electrode can be thinned.

An embodiment of the present invention will be described below by taking a multilayer ceramic capacitor as an example.

First, a ceramic dielectric powder containing barium titanate as a main component, polyvinyl butyral as a binder, dibutyl phthalate as a plasticizer, and methyl ethyl ketone as a solvent are weighed in predetermined amounts, and then zirconia balls are used as dispersion media for 40 hours. Milling is performed to produce a ceramic slurry.

Separately, a predetermined amount of ethyl cellulose as a binder and methyl ethyl ketone as an organic solvent are weighed and dispersed by a mixer to prepare a vehicle. To this, nickel powder having an average particle size of 0.5 μm is added, and the mixture is preliminarily kneaded by a mixer. Further, dispersion was performed using three rolls to prepare a conductive paste for a primary internal electrode. In addition, as a paste for the secondary internal electrode, a common material shown in (Table 1) was further added to the conductive paste.

[0018]

[Table 1]

Next, as shown in FIG. 1, a ceramic slurry was applied to the surface of a polyethylene terephthalate carrier film treated with a release agent by a roll coating method and dried to form a 7 μm thick ceramic for an effective layer. A green sheet 1 and a ceramic green sheet for an ineffective layer having a thickness of 50 μm are prepared.

Next, a conductive paste for the primary internal electrode 2a is applied to one surface of the ceramic green sheet 1 having a thickness of 7 μm by using a gravure printing method, and then dried at 100 ° C. for 30 seconds to perform the primary internal electrode 2a (central portion B, outer periphery). Form part A). The thickness of the primary internal electrode 2a is 2 μm as shown in Table 1 so that no electrode break occurs inside the sintered body.
m.

Subsequently, the conductive paste for the secondary internal electrode 2b is superimposed only on the outer peripheral portion A of the primary internal electrode 2a by using a gravure printing method (Table 1). Is applied, followed by drying at 100 ° C. for 20 seconds to produce a ceramic green sheet on which the internal electrodes 2 are formed so that the entire thickness becomes approximately 2 μm.

Separately, three ceramic green sheets each having a thickness of 50 μm are stacked and laminated and pressed at a pressure of 50 kg / cm ² to produce a ceramic green sheet having an ineffective layer.

Thereafter, the ceramic green sheet 1a having the internal electrode 2 formed thereon is laminated under pressure at a pressure of 50 kg / cm ² on the ceramic green sheet of the ineffective layer, and then the carrier film is peeled off. Subsequently, the above operation is repeated 201 times to produce a laminated green block. The lamination of the ceramic green sheets 1a is performed alternately for each layer.
In the longitudinal direction. Finally stacked ceramic green sheets invalid layer was pressure laminated at a pressure 50 Kg / cm ^2, to prepare a green laminate block make this pressurization a pressure 500 Kg / cm ^2.

Next, after cutting and separating the laminated green block into a predetermined green chip shape, these are stored in a firing setter, and the binder is removed from room temperature to 400 ° C. for about 30 hours in a burnout furnace. After that, firing is performed in a firing furnace to 1280 ° C. for about 20 hours to produce a sintered body. The obtained sintered body has a structure in which one end of the internal electrode 2 is alternately exposed with a dielectric ceramic layer interposed therebetween and is exposed to different end faces facing each other.

Next, after forming external electrodes on both end surfaces of the sintered body where the internal electrodes 2 are exposed, a plating process is performed on the surfaces of the external electrodes to improve solderability, thereby producing a multilayer ceramic capacitor. did. The obtained multilayer ceramic capacitor was subjected to a high-temperature accelerated load accelerated life test evaluation in which the number of internal structural defects was generated and four times the rated voltage was applied for 1000 hours in a temperature chamber at 85 ° C. The results are shown in Table 1 together with the formed thickness of the secondary internal electrode 2b.

Sample numbers No. 1, 3, 7, 12 in the table
Is a comparative example.

As shown in Table 1, the primary internal electrode 2a
In the case of only, the central portion B is thicker than the outer peripheral portion A. To correct this, the secondary internal electrode 2b is replaced with the primary internal electrode 2a.
Of the internal electrode 2C so as to overlap only the outer peripheral portion A of the
When (thickness C) is formed, if the thickness difference between the central portion B and the outer peripheral portion (A + C) of the internal electrode 2 exceeds ± 0.5 μm, the tendency of occurrence of structural defects increases, and the insulation resistance in the life test is increased. Deterioration occurs. This is because if the thickness difference between the central portion B and the outer peripheral portion (A + C) of the internal electrode 2 becomes large, it becomes difficult to uniformly apply the pressing force during the production of the laminated green block, which promotes internal structural defects and deterioration of insulation resistance. It is considered something.

If the amount of the common material is more than 50%, the effect of suppressing the generation of structural defects is obtained. It is not preferable because the electrode 2 is deformed and the insulation resistance is deteriorated in the life test.

In the present invention, the thickness of the ceramic green sheet, the number of layers, the firing conditions,
Similar results can be obtained regardless of the type of the metal powder of the conductive metal paste.

[0030]

As described above, according to the present invention, in order to compensate for the thinning of the outer peripheral portion of the primary internal electrode, the secondary internal electrode is formed so as to overlap only with the outer peripheral portion of the primary internal electrode. By reducing the difference in thickness between the central portion and the outer peripheral portion, the overall formed thickness of the internal electrode can be reduced. As a result, the thickness step at the boundary between the formation portion and the non-formation portion of the internal electrode is reduced. Thus, it is possible to prevent the occurrence of internal structural defects and the like. Further, by making the internal electrodes thin with a uniform thickness, it becomes an effective means for providing a highly reliable multilayer ceramic electronic component with small distortion.

[Brief description of the drawings]

FIG. 1 is a sectional view of an internal electrode according to an embodiment of a multilayer ceramic electronic component of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic green sheet 2 Internal electrode 2a Primary internal electrode 2b Secondary internal electrode A Thickness of outer peripheral part of primary internal electrode B Thickness of central part of primary internal electrode C Thickness of secondary internal electrode formation

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 5E001 AB03 AC03 AC04 AC09 AE02 AE03 AF00 AF06 AH01 AH06 AH09 AJ01 5E082 AA01 AB03 BC33 EE04 EE18 EE35 EE41 FG06 FG26 FG27 FG54 GG10 GG26 HH43 JJ03 JJ01 LL03

Claims (4)

[Claims] 1. A multilayer ceramic electronic component in which a laminated green block in which a plurality of ceramic green sheets and internal electrodes are alternately laminated is cut into a predetermined shape and then fired, the internal electrodes are coated with a conductive paste on the surface of the ceramic green sheets. A method for manufacturing a multilayer ceramic electronic component, wherein a secondary internal electrode is formed by using a conductive paste so as to overlap with only the outer peripheral portion of the primary internal electrode after forming and drying the primary internal electrode. 2. A primary internal electrode and a secondary internal electrode are each formed by a gravure printing method using a conductive paste made of a conductive metal powder, an organic solvent, a binder, a common material (a material for forming a ceramic layer), and the like. The method for manufacturing a multilayer ceramic electronic component according to claim 1. 3. The multilayer ceramic electronic device according to claim 1, wherein the conductive paste of the secondary internal electrode is obtained by adding a common material (a material forming a ceramic layer) to the conductive metal powder up to 50% based on the conductive metal powder. The method of manufacturing the part. 4. The secondary internal electrode is formed so as to have a thickness equal to the thickness of the central portion of the primary internal electrode so as to overlap only with the outer peripheral portion of the primary internal electrode. 2. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the thickness of the entire electrode is made substantially uniform.