JPH03270002A - Laminated inductor and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate a disconnection and to make an insulating property good by sintering a laminated inductor in which an insulator layer having a melting point lower than the sintering temperature of a magnetic substance and a conductor is laid between the magnetic substance and the conductor. CONSTITUTION:A glass sheet is used as an electrical insulator layer. An SiO2-PbO-based component, an SiO2-ZnO-based component or an SiO2-Al2O3-PbO-based component is used as the component for the glass sheet. It is desirable to use the component whose melting point is lower than and close to the sintering temperature of a magnetic substance layer and a conductor layer and whose behavior at a sintering process is similar to the layers; a material which easily relaxes the difference in a contraction rate between the magnetic substance layer and the conductor layer due to the existence of the electrical insulator layer is selected. In addition, when a hot pressurization sintering method which makes a sintering operation possible even at a low temperature is used at the same time, a more effective manufacturing operation can be executed. By the method, it is possible to execute the sintering operation which makes the difference in a contraction behavior extremely small even in the magnetic substance layer, the conductor layer and the electrical insulator layer whose contraction rate differs largely. From a viewpoint that, by the hot pressurization sintering method, the shape of a final product can be obtained directly and that a cutting process and a grinding process can be shortened or omitted, a hot press or a hot hydrostatic pressure press is suitable.

Description

[Detailed description of the invention] B1 Purpose of the invention [Industrial application field] The present invention relates to a multilayer inductor.

[Conventional technology]

Conventional multilayer inductors generally use a ferrite magnetic material mainly composed of iron oxide as the magnetic material, and a paste made by kneading ferrite powder with a known binder and solvent such as methyl cellulose or butyral resin is processed into a thin layer by a printing method to create a magnetic layer. A conductor layer is made of Ag-Pd.
, Ag, other alloys or metal powders and a binder are printed on the magnetic layer, or a laminate is formed by stacking the thin layers obtained by each printing, and the laminate is sintered. It was created by processing the magnetic material in a furnace at the required sintering temperature and time.

However, in general, the Ag-Pd alloy of the conductor part is 700 to 8
While sintering is completed at around 00°C, sintering of the magnetic layer requires a temperature of 1000°C or higher. There is a difference in shrinkage during sintering between the body layer and the Ag-P layer.
Since the thickness of the layer such as d is as thin as several tens of micrometers, continuity cannot be maintained during sintering and it often breaks, resulting in a disconnection state. Also, when baking the external electrode terminals onto the inductor after sintering, the shrinkage rates of the magnetic layer and the conductor part during sintering are different, as mentioned above, so the internal electrodes and external electrodes do not join completely, but only locally. Since the area becomes smaller, a problem arises in that DC resistance increases.

Furthermore, when sintered at high temperatures, there is a drawback that properties deteriorate due to a reaction between the ferrite of the magnetic layer and the metal (eg, Ag-Pd) of the conductive layer. On the other hand, if the sintering temperature is lowered (for example, lower than 1000"C), the ferrite itself in the magnetic layer will not be sufficiently sintered, resulting in an incomplete sintered body with insufficient density.
There were drawbacks in that the inductor did not have sufficient mechanical strength and its magnetic properties were also insufficient.

[Problem to be solved by the invention]

In order to eliminate these drawbacks, the present invention uses an electrical insulator such as a glass sheet, which has a relatively lower melting point than the magnetic layer and the conductive layer, between the bonding surfaces of the magnetic layer and the conductive layer. The purpose of the present invention is to provide a multilayer inductor that does not cause wire breakage and has good insulation properties by combining layers with a hot-pressure sintering process if necessary, and also provides a durable and compact multilayer inductor, as well as a method for manufacturing the same. be.

Structure of the Invention [Means for Solving the Problems] The present invention provides an electric insulator layer having a melting point lower than the respective sintering temperatures of the magnetic material and the conductive material at the joint between the magnetic material layer and the conductive material layer. By sintering, defects such as deterioration of characteristics due to the reaction between the magnetic layer and the conductive layer and disconnection between internal electrodes can be eliminated, and by using the hot press method in the sintering process of the manufacturing process mentioned above, The present invention provides a multilayer inductor with a complicated pattern and an ultra-thin shape, which has not been available before, and a method for manufacturing the same.

That is, the present invention provides a multilayer inductor in which a magnetic layer made of a ferromagnetic material and a conductive layer formed in a coil shape are superimposed in the stacking direction, in which the above-mentioned layer is formed on the joining surface of the magnetic layer and the conductive layer. A multilayer inductor characterized by forming an electrical insulating layer having a melting point lower than the sintering temperature of the magnetic material and the conductive material, and in the production of the above-described multilayer inductor, the sintering process is performed by a hot pressing method. Provided is a method for manufacturing a multilayer inductor characterized in that it is processed.

[Effect]

By sintering a multilayer inductor in which an insulating layer with a melting point lower than the sintering temperature of the former two is interposed between the magnetic material and the conductive material, breakage of the conductive material in the sintered laminate can be prevented. Furthermore, by sintering the laminated body of the laminated inductance with the insulating layer interposed therebetween using a hot pressing method, it is possible to increase the density without causing failure of the conductor.
Multilayer inductors with high characteristics can be manufactured.

〔Example〕

In this example, a glass sheet is used as the electrical insulator layer,
The components of the glass sheet are 5iO2-PbO system, 5i
02-ZnO system and 5j02-A120a-PbO system were used. It is desirable to use a material whose melting point is lower and closer to the sintering temperature of the magnetic layer and the conductive layer, and whose behavior during the sintering process is similar. A material that can easily alleviate the difference is selected.

However - a magnetic layer with significantly different shrinkage rates within the shell;
Since a conductive layer and an electrically insulating layer are used, it is very difficult to obtain a sintered body with a uniform structure by sintering using a normal powder metallurgy method. Therefore, by using a hot pressure sintering method that allows sintering even at low temperatures, more effective production can be achieved.

With this method, it is possible to sinter magnetic layers, conductive layers, and electrical insulating layers that have significantly different shrinkage rates with as little difference in shrinkage behavior as possible. The hot pressure sintering method can be done using any of the so-called hot presses, hot isostatic presses, and hot extrusions, but it is said that the final product shape can be obtained directly and the cutting and grinding processes can be shortened or omitted compared to conventional methods. From this point of view, hot press and hot isostatic press are suitable.

Examples will be specifically shown below.

(Example-1) Using Ni-Zn ferrite as the magnetic material, Ag-Pd alloy as the conductor for internal electrodes, and a thin layer formed of Ag paste powder as the terminal electrode for external connection,
A 5-in2 A120+-PbO glass sheet was printed as an electrical insulator layer on the joint, and the laminated body was then sintered at a temperature of 1000° C. for 60 minutes.

Observing the structure of the cross section of the obtained sintered body, A of the conductor part
The g-Pd alloy has a width of approximately 20 μm and is almost uniform and does not break. A glass layer of several μm is observed between the magnetic material and the conductive material, and the degree of adhesion is good, and the density as a laminate is 5. A sufficient sintered body of .2 g/Cm' was obtained, and all the samples were of good quality.

As a comparative example, a conventional manufacturing method, that is, a magnetic Ni-Z
A laminate made by printing and laminating paste-like powder of n-type ferrite and Ag-Pd as a conductive layer was heated at a temperature of 1000°C for 60 minutes.
A sample piece was obtained by sintering for a minute. The width of the Ag-Pd in the conductor part of the sintered body obtained by this conventional manufacturing method is uneven, and there are many cases in which the conductor part is undulating or broken, and moreover, the magnetic material and the conductor react with each other. It was observed from the cross-sectional structure that about 30% of the samples were defective. Further, the fired body obtained according to the present invention was subjected to a humidity resistance load test for 200 hours at a constant temperature and humidity of 40° C. and 90% RH, and all results were good. In the conventional type, short circuits often occur during energization due to the presence of moisture after several tens of hours, resulting in a failure rate of approximately 30%.

(Example-2) Bonding of thin layers formed of Ni-Zn ferrite as a magnetic material, Ag-Pd alloy (inner mold part) as a conductor, and paste-like powder of Ag (terminal electrode for external connection) A 5i02-PbO glass sheet was printed and laminated as an electrical insulator layer on the part, and then the laminated body was pressed at a temperature of 800°C for 5 minutes with a force of 0.5 ton/am'' using a hot press method. As a result, a sintered body of a laminated inductor having a density of 5°3 g/c1 was obtained.

As a result of observing the structure of the cross section of the obtained fired body, a uniform structure similar to that observed in Example-1 was obtained. In addition, in the sintered body manufactured by the conventional manufacturing method, it has been confirmed by composition analysis that the magnetic material and the conductive material begin to react and become alloyed, but in the sintered body obtained by the present invention, the magnetic material and the conductive material begin to react and become alloyed. Since the glass sheet was present at the junction between the body and the conductor, no reaction with Ag-Pd was observed.

Next, the obtained multilayer inductor was heated at 40°C x 90% R-
A humidity resistance load test was conducted for 200 hours in a constant temperature and humidity environment.

All of the sample pieces of this example were good, but the DC resistance of the conventional samples increased over time, and about 15% were defective.

Further, from observation of the cross-sectional structure of the joint between the internal electrode and the external electrode of the obtained sintered body of this example, it was confirmed that the internal electrode having a width of about 20 μm was uniformly joined to the external electrode. In inductors manufactured using conventional sintering methods, the external electrodes are bonded to the internal electrodes by baking.
The sintering property was poor, the bonding area was small, and the tensile strength was as low as 0.5 kg/cm2, which caused the product to peel off easily. However, since it was sintered as a single piece, its bondability was good and the tensile strength was 2.0 kg/cm+2, which was a good result.

C1 Effects of the Invention [Effects of the Invention] As described above, according to the present invention, an electrically insulating layer such as a glass sheet is placed on the joint surface of the magnetic layer and the conductive layer and sintered to form a uniform conductor. It has become possible to manufacture multilayer inductors. In addition, by placing an electrical insulating layer such as a glass sheet on the joint surface of the magnetic material layer and the conductive material layer and performing hot pressure sintering, it is possible to sinter at a low temperature and obtain a magnetic material with high density. It has become possible to provide a multilayer inductor with good electrical characteristics and a small volume and a large inductance value. Furthermore, the external electrode terminals were processed at the same time as the internal electrodes, and sintering enabled a durable connection.

In addition, as a ripple effect, an electrical insulating layer is formed between the magnetic layer and the conductive layer, making it possible to select materials with high properties even for magnetic materials with relatively low electrical resistance, resulting in an efficient multilayer type. Inductor can be provided.

Claims (2)

[Claims] 1. In a multilayer inductor configured such that a magnetic layer made of a ferromagnetic material and a conductive layer formed in a coil shape are superimposed in the lamination direction, the magnetic material and the conductive material are provided on the joint surface of the magnetic layer and the conductive layer. A multilayer inductor characterized by forming an electrical insulator layer having a melting point lower than the sintering temperature of the inductor. 2. 2. A method for manufacturing a multilayer inductor according to claim 1, wherein the sintering step is performed by hot pressing.