JPS58112319A - Conductive paint for laminated condenser internal electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive paint useful as an internal electrode of a ceramic multilayer capacitor.

Generally, the manufacturing method of multilayer capacitors is to produce an unfired dielectric formed using a dielectric composition in which ceramic dielectric powder such as a composite perovskite compound containing titanium oxide, barium titanate, and lead is uniformly dispersed in an organic vehicle. A conductive paint consisting of a conductive powder and an organic vehicle is screen printed on the body sheet to form an 'rtt electrode layer, and then a green dielectric sheet with an electrode layer made in the same manner is formed. Stack the desired number of sheets, and finally stack a dielectric sheet on which no electrodes are printed and compress this, or alternatively screen print the dielectric composition and conductive paint alternately.
By drying, an unfired laminate having dielectric layers and internal electrode layers alternately is obtained, and after cutting this into a predetermined size, the dielectric is heated at a high enough temperature to sinter, e.g.
It is formed in a furnace at 1,400°C, and external electrodes are attached to the sides of the laminate that forms the main body.

Conventionally, as conductive powder for internal electrode coatings, metals such as platinum, palladium, silver, gold, nickel, and steel, which can withstand high-temperature firing, and their oxides have been used.

The organic vehicle includes a mixture of fatty components such as ethyl cellulose, nitrocellulose, rosin, and holiteruben atuh, and organic solvents such as terpineol, butyl carpitol, butyl cellosolve, and kerosene, and if desired, plasticizers such as diethyl phthalate and dibutyl phthalate, and wax. is used with the addition of

In recent years, with the demand for smaller size and higher performance of electronic devices, there has been a demand for multilayer capacitors that are smaller and have larger capacities. For this reason, research has been conducted to further reduce the thickness of both the dielectric layer and the electrode layer while maintaining good performance. In addition, to obtain a high-performance multilayer capacitor that can be used in a high frequency range, the electric resistance of the internal electrodes is further increased, for example, by 2 x #Ω-
There is a need to reduce this to below m. However, with conventional conductive paint, the baked electrode 111# has many voids and has a mesh-like structure, and the surface is rough and uneven, resulting in a low resistivity. required a considerable film thickness. Also, if you try to reduce the film thickness, the porosity will increase, making the resistivity even higher, and as a result, the dielectric loss will increase, and eventually the capacitor will become unusable due to wire breakage and a drop in withstand voltage, making the internal electrodes thinner, There was a limit to the reduction in resistivity.

As a result of various studies, the present inventors decided to incorporate special ingredients into a composition consisting of a conductive powder and an organic vehicle.
Therefore, we have completed a conductive paint that can meet the above-mentioned requirements.

That is, the present invention is a conductive paint for internal electrodes of multilayer capacitors, which is characterized by containing an organic phosphorus compound in addition to conductive powder and an organic vehicle.

The organic phosphorus compounds used in the present invention are completely decomposed and scattered by firing, and include phosphoric acid esters, phosphorous acid esters, phosphoric acid amides, thio+7m esters,
Examples include phosphines.

Phosphate esters are particularly preferred, such as allyl esters such as triphenyl phosphate, tricresyl phosphate, and cresyl diphenyl phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, and tri(2-ethylhexyl) phosphate. Alkyl esters, alkyl diallyl esters such as octyldiphenyl phosphate, tris-phosphate
Halogen-substituted products such as β-chloroethyl, tris-β-chloropropyl phosphate, tris-dibromopropyl phosphate, and chlorinated polyphosphate esters are preferably used. Two or more of these compounds may be used in combination.

By blending these organic phosphorus compounds, an extremely thin and dense electrode layer with good sinterability is formed, which has a much better specific resistance value than conventional ones, can withstand high frequency use, and has dielectric loss characteristics. It is also possible to further reduce the film thickness of the electrode without sacrificing the characteristics such as. For example, in the past, the practical limit was 4 to 5 μm at most, but according to the present invention, the thickness can be reduced to about 1 μm. This is because, first, in the process of baking the conductive paint,
With conventional paints, after the paint film dries, the resin component in the vehicle rapidly decomposes and scatters around 600-400°C, and as a result, when the fired film is observed, it does not shrink much after drying.
In contrast, in the present invention, the addition of the additive slows down the decomposition rate of the resin, and the electrode layer gradually forms in the thickness direction. This is believed to be because the porosity becomes extremely small as it contracts and comes into close contact with the dielectric layer, and secondly, the sinterability of the conductive powder becomes very good.

Considering that in the past, when baking conductive paints, we used materials that were as easy to decompose as possible in order to completely decompose and remove the resin used, it would have been unexpected to slow down the decomposition rate. This was elucidated for the first time by the present inventors. The reason why the sinterability of the powder improves is not clear, but it is likely that the addition of an organic phosphorus compound improves the dispersibility of the conductive powder in the paint, and the process of decomposition of the organic phosphorus compound during firing improves the conductivity. It is thought that this is related to a direct effect on the sintering of the powder.

Since the additives of the present invention are ultimately burned out during firing, they have the advantage of not deteriorating the performance of laminated air conditioners even if they are added in large amounts, unlike when metal oxides are used. There is also.

As the resin component of the M-machine vehicle of the present invention, conventionally used resins such as ethyl cellulose, nitrocellulose, and boliterbene resin can be used, and good results can be obtained with any of them, but in particular, relatively flame-retardant resins or mixtures of these with oils and fats can be used. It is preferable to include VC because a more uniform and dense electrode layer can be formed due to the synergistic effect with the organic phosphorus compound. Only this flame-retardant resin can be used, and suitable oils include semi-drying oils such as olive oil, non-drying castor oil, soybean oil and cottonseed oil.

Other components of the vehicle, ie, solvents, plasticizers, etc., may be those commonly used and are appropriately blended depending on the required suitability of the coating.

The total amount of the organic phosphorus compound and organic vehicle used in the paint is about 20 to 150 parts by weight based on 100 parts by weight of the conductive powder.

Although it is effective to add a small amount of organic phosphorus compound, it is practically preferable to add 51 parts or more of the organic phosphorus compound to 100 parts by weight of the conductive powder. Even if a large amount is blended, there is no problem as long as it is within the range that can form a paint.

As the conductive powder and bed, one or more of high melting point metals such as platinum, palladium, silver, gold, nickel, copper, oxides and alloys thereof are used. Furthermore, it is not outside the scope of the invention to include additives such as metal oxides, which are often added to improve the characteristics of capacitors.

Next, the present invention will be explained with reference to Examples. Although the case where all of the palladium is used as the conductive powder has been described here, the same effect can be obtained with other conductive powders.

Example 1 Palladium powder 100 parts by weight Tricresyl phosphate 10 I Ethyl cellulose
9 Terpineol 5
1 I diptylphthalate 81 or more components were kneaded in a roll mill to obtain a conductive paint.

Examples 2 to 16, Comparative Examples 1 to 2 Conductive paints having the compositions shown in Table 1 were obtained in a different manner from Example 1. Examples 7 to 9 are examples in which triphenyl phosphate or tri(2-ethylhexyl) phosphate was used instead of tricresyl phosphate, and Comparative Examples 1 to 2 are examples in which no organic phosphorus compound was blended.

The conductive paint of each example and comparative example was screen printed on an all-alumina substrate, dried at 250°C for 6 hours, and then 250C/
The temperature was raised at a rate of 1 hour, and firing was performed at a peak temperature of 1350°C for 3 hours. The thickness and specific resistance of the fired film were measured, and the results are shown in Table 1. The dry film thickness was approximately 8 μm in all cases.

(The following is a blank space) As is clear from Table 1, when the conductive paint of the present invention is used, an extremely thin electrode film with excellent conductivity can be obtained. Although an alumina substrate was used in the experiment, the results showed exactly the same tendency even if an unfired ceramic sheet was used.

Next, the conductive paints of Example 4 and Comparative Example 1 were screen printed on an alumina substrate with different film thicknesses, and fired under the same conditions as in the previous example. The relationship between the film thickness and resistivity after firing was investigated for each of them, and as is clear from Figure 1 (Fig. (curve A). The conventional paint of Comparative Example 1 cannot withstand use under 6 μm lightning, and has a higher specific resistance value than that of the present invention even when the film thickness is large (curve B). This indicates that the fired film has many voids and is not dense.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between fired film thickness and specific resistance when the present invention and conventional conductive paints are used. Curve mA is the case when the present invention paint is used, and curve B is when the conventional paint is used. . Patent applicant Shoei Chemical Industry Co., Ltd.

Claims (2)

[Claims] (1) A conductive paint for internal electrodes of multilayer capacitors consisting of conductive powder, an organic vehicle, and an organic phosphorus compound. (2) The organic vehicle is at least rosin, phenol or v'
The conductive paint for internal electrodes of a multilayer capacitor according to claim 1, which contains two or more kinds of i.