JPS5950618B2 - Manufacturing method of ferrite element assembly - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a ferrite element assembly in which two or more ferrite elements are joined together.

BACKGROUND ART A bonded body in which a plurality of ceramic bodies are bonded together has been developed in response to demands for miniaturization and integrated circuits of electronic circuits, and is often used in microwave integrated circuit elements.

A bonded body in which a porcelain dielectric magnesium aluminate or manganese titanate element is used as a substrate and a porcelain magnetic yttrium iron garnet element is integrally bonded to this substrate is:
This type is known as an integrated microwave non-reciprocal element substrate. Such a bonded body can be formed by (1) placing the porcelain raw material powder for the other element on an already sintered substrate and hot-pressing it, or (2) forming it for each porcelain element separately. Either a raw material powder molded body or a calcined molded body is prepared and formed by hot pressing in a state where they are brought into contact with each other as desired, or (3) each element body is planned to be joined as a sintered body or a single crystal body. It is bonded to the body by hot pressing with a thin glass plate interposed as flux on the surface. No organic adhesives such as epoxy resins are used. This is because, in this type of bonded body, the bonding surfaces must be in close contact with each other with substantially no voids, and it is not possible to leave an adhesive layer at the bonding interface. However, these current methods are not satisfactory for the reasons described below.

First of all, in these bonded bodies, there is a first requirement that the bonding surfaces be brought into close contact without intervening an adhesive layer at the bonding interface, and that the boundaries of each element body must be clear. In response to this request, in method (1), in which porcelain raw material powder is applied to one side of the element, a solid phase reaction occurs during sintering by hot pressing, and based on the high activity of the powder, the bonding interface of the element is Deep interdiffusion in the direction perpendicular to the interface, which occurs from one side to the other and from the other to one side, cannot be prevented. In this case, mutual diffusion occurs rapidly and is extremely difficult to control. Therefore, in the resulting zygote, the elementary body boundaries are unclear.
In method (2), in which a bonded body is obtained from a molded body obtained by pressure-molding the raw material powder, it is difficult to handle the powder molded body because it lacks mechanical strength. In addition, since the large shrinkage deformation during sintering is different regardless of whether a powder molded body or a calcined molded body is used, it is possible to avoid making the joint interface not in the planned plane and making it unclear. do not have. Furthermore, in method (3) in which a thin glass plate is interposed as a flux, the thickness of the thin glass plate is required to obtain a good flux effect, and this glass component is distributed within the structure of the bonded surface of the pixel body after the bonded body is formed. . No matter how you choose the flux glass, you will never choose the same material as the element to be bonded, so the bonded body obtained in this way will have a material with a different composition other than the element remaining near the bonding interface. . Therefore, bonded bodies are not preferred because they deteriorate magnetic properties and increase magnetic resistance. The present invention eliminates the drawbacks of the current methods and provides a method for obtaining a ferrite element bonded body in which the element bodies are directly brought into close contact with each other without intervening foreign matter at the bonding interface.

In other words, the coefficient of thermal expansion of two or more ferrite bodies, either already bonded bodies or single crystal bodies, is approximated to within ±5%, and each of the opposing surfaces to be joined is polished with No. 600 abrasive grains. The surfaces to be joined are selected to have a smoothness higher than that of the finished surface, and the corresponding surfaces to be joined are brought into direct opposing contact and a pressure of 50 to 500 kg/cm2 is applied perpendicularly to the opposing surfaces for at least 10 minutes at a temperature 600 to 200°C lower than the melting point. The method of manufacturing a ferrite element assembly is characterized in that a mutual diffusion layer is formed and the ferrite element assembly is joined together. Each element to be joined by the method of the invention is therefore an already sintered or monocrystalline ferrite solid.

In particular, the sintered body must be sintered to such an extent that it will not undergo substantial shrinkage and deformation during subsequent heating or hot pressing steps. The surfaces to be joined of each element body are polished with abrasive grains so that they come into close contact when facing each other and are polished to a level of smoothness. In this sense. There is no need for a mirror finish. After the bonded body is formed, no substance is applied or sprayed on the opposing surfaces to be bonded, nor is it sandwiched between the surfaces when they are placed facing each other.
The bonded body forming process is a heating and pressing process. Each element body is placed in a furnace so that opposing surfaces to be joined are brought into contact with each other and pressurized. First, the temperature inside the furnace is raised to a high temperature. The atmosphere in the furnace is controlled to, for example, an oxygen atmosphere as desired. Since each element body is a sintered body or a single crystal body, there is no need to worry about deformation. The element body placed at a desired high temperature is then pressurized. When the temperature and pressure conditions are set appropriately, plastic flow occurs on the surfaces to be joined of each of the opposing contacting elements, and although the overall shape is hardly deformed, some of the Both surfaces to be joined are in close contact regardless of unevenness. When the pressure is removed or the pressure is maintained at a high temperature, ion diffusion occurs between the two elements at the bonding interface, and both elements are firmly bonded by forming a mutual diffusion region near the interface. This diffusion region is formed only near the bonding interface, and the diffusion rate is slow, so it is extremely easy to control the region formation. Even if there is an atmospheric gas such as oxygen trapped in the opposing gap when the surfaces to be joined of each element body are placed in opposing contact with each other, will such a gas be absorbed by the pixel body during this mutual diffusion? or be removed into the atmosphere and virtually disappear. If the bonded body is pressurized in this step, the pressure is removed; if not, the bonded body is left to cool slowly to obtain a ferrite element body bonded body. The favorable manufacturing conditions for forming a bonded body in this manner will be described below.

First, we will discuss the polishing of the surfaces to be joined. For example, manganese-zinc ferrite with the same chemical composition, (MnO)
. ．． . , (ZnO) 0.19 (Fe2O3) 0.52, one side is a single crystal and the other is a sintered polycrystal.
0, 600, or 800, each with a smooth finish and facing each other, and heated at 1000℃ in a nitrogen atmosphere at 50kg/cm
・Heat and pressurize. After forming the bonded body, it was cooled, and a vertical section cut perpendicular to the bonded surface was mirror-polished and etched, and then observed using an optical microscope. In the example combination of abrasive bodies using No. 600 or No. 800 abrasive grains, grain boundaries similar to those seen in a normal sintered polycrystalline structure are observed and integrated due to plastic flow and mutual diffusion at the joint interface.

FIG. 1 is a microscopic structure diagram of a bonded body formed by No. 600 abrasive finishing example, and it can be seen that the interface between the sintered polycrystalline body 1 and the single crystalline body 2 is tightly integrated. Observations similar to this example can also be made for the 800 finish example,
In the No. 400 finish combination example, voids extending along the bonding interface as shown in FIG. 2 are observed. Unlike the independent spherical voids observed, for example, in sintered bodies, these voids significantly increase the magnetic resistance in the direction perpendicular to the joint surface and further impair the strength of the joint, so such abrasive finishing is rejected. Must-have. Mark the appropriate example of this relationship with a circle, and mark the unsuitable example. Mark the first
Display in table. From Table 1, it is necessary to prepare the surfaces to be joined for each element body so that they are smooth enough to be finished with at least No. 600 abrasive grain.

Next, the temperature conditions required for pressurization will be described. 1st
As shown in the table, manganese-zinc ferrite single-crystal and polycrystalline bodies with the same composition were prepared at 900°C, 950°C, or 1000°C in a nitrogen atmosphere for each example in which the alumina abrasive grain No. 600 finish and the surfaces to be bonded were placed facing each other. 50kg/℃
A pressure of m2 was applied for 10 minutes each and then cooled. As a result of taking a vertical cross section of the joint surface of each joint, mirror polishing it, etching it, and observing it with an optical microscope, we found that in the pressurized examples at 950°C and 1000°C, voids extending along the joint interface were observed as in the example in Figure 1. Not observed. However, in the case of pressurization at 900° C., plastic flow interdiffusion is impaired, and elongated voids are observed as in the example in FIG. 2. This temperature is therefore not suitable and requires at least 950°C. For this reason, a range 600° C. lower than the melting point is limited on the low temperature side. The pressurizing temperature may be as high as about 1550° C., which is the melting point of this ferrite, at least 200° C. lower. Next, the pressure conditions to be applied will be described.

Same as above, each combination of single-crystal element and polycrystal element with No. 600 finish on the planned surface to be joined was made under the same temperature condition of 1000°C in nitrogen atmosphere, and the pressure was 10 g/CTn2, 1 kg/d.
, 50 kg/Cm· were applied for 10 minutes for comparison. cooling. According to the optical microscope observation of the vertical cross section of the bonded surface, which was carried out in the same manner, in the case where a pressure of 10 g/Cnl was applied, the re-elementary body peeled off during polishing of the observation tissue piece, making observation impossible.
In the example of applying 1 kg/Cm2, an extended void along the bonding interface similar to that observed in the example in Fig. 2 is created, but when applying 50 kg
/Cm2. In the case of application, a good bonding interface is exhibited without any voids. Therefore, a pressure of 50 kg/Cm2 or more is required. Regarding the pressure application time, the application time was set to 1 minute, 5 minutes, and 10 minutes for each combination of single-crystal and polycrystalline elements with a No. 600 finish on the surface to be joined, 950°C in a nitrogen atmosphere, and a pressure of 50 kg/Cm2. Instead, I let the comparison pass. After cooling, optical microscope observation of the vertical cross section of the joint surface was performed in the same manner.
In the example after 10 minutes, the tissue piece for observation peeled off during polishing, making observation impossible.In the example after 5 minutes, an extended gap along the bonding interface was observed, whereas in the example after 10 minutes, no gaps were observed.゛It rarely achieves complete bonding. Therefore, even if the conditions for the smoothness of the surfaces to be joined, the temperature, and the applied pressure are well selected, the time required to maintain the joint under pressure is at least 10 minutes. The ferrite bodies to be joined undergo plastic flow and mutual diffusion actively at the joining interface when the surfaces to be joined are polished and the temperature, pressure, and holding time in the heating and pressurizing process are adjusted to the conditions described above. If so, there is no problem even if the composition of the elementary bodies is different.

However, in this case, if the coefficient of thermal expansion is not taken into consideration, one or both of the elements will break due to the difference in shrinkage rate during the cooling process after being joined at high temperatures. Therefore, each ferrite element body must be a single crystal body or well sintered to reach the shrinkage rate at the bonding temperature, and must not be a pre-sintered body. The molar ratio chemical compositions (1), (2), (
3), (4), (5), (6), and (7) all contain manganese-zinc polycrystalline ferrite sintered at 1350°C in nitrogen and a chemical composition of (MnO) 0.280 (ZnO) 0. 19
5 (Fe2O3) 0.525 of manganese zinc single crystal ferrite, the surfaces to be bonded were polished to a mirror surface, the corresponding surfaces were brought into opposing contact, and the bonding temperature and pressure of 50 kg/cm2 were held in nitrogen at 950°C or 1150°C. They were bonded by applying pressure for 10 minutes. When the bonded interface was observed under a microscope for each bonded example in the same manner as described above, no voids were observed along the interface, but in some cases cracks were observed near the interface.

For each bonding example, the thermal expansion coefficient ratio of the polycrystalline and single-crystalline pixel bodies facing each other on the horizontal axis is taken as the bonding temperature on the vertical axis. As shown in the figure. FIG. 4 shows a microscopic structure diagram of the bonding interface for an example of the cross mark in FIG. 3. It will be understood from FIG. 3 why the thermal expansion coefficient ratio is kept within ±5%.

This is a bonding example obtained in the example, and the chemical composition is Fe2O.
352 mol %, MnO 29 mol %, ZnOl 9 mol % single crystal and polycrystalline manganese zinc ferrite sintered at 1350°C. The surfaces to be joined were polished to mirror surfaces and faced each other, and 50 kg was prepared at 1000°C in a nitrogen atmosphere. A pressure of /Cm2 was applied and held for 10 minutes and then allowed to cool. At the bonding interface, it was difficult to identify the pixel body, and the polycrystalline side could be recognized from the pore distribution.

A ring-shaped sample in which the bonding surface is included in the magnetic path from a thin plate cut perpendicular to the bonding surface, and each ring-shaped sample containing only a single crystal or polycrystalline region are processed by ultrasonic processing to perform winding. A magnetic element was fabricated. IKH. The magnetic permeability is maximum in the example of the magnetic material element formed only from a single crystal region, is minimum in the example of the element formed only from the polycrystalline region, and exhibits an intermediate value in the example of the magnetic material element according to the example. Therefore, it is recognized that the magnetic element according to the example is in a magnetically perfect state without increasing the magnetic resistance at the junction interface.

[Brief explanation of drawings]

Fig. 1 is a microscopic structure diagram of a vertical cross section of the joining surface of a ferrite element assembly obtained in Examples and Comparative Examples. Figure 4 shows the presence or absence of cracks near the bonding interface with × and ○ marks for the ferrite element assembly.
FIG. 2 is a microscopic microstructure diagram showing a vertical cross-section of the bonded surface of the stamped bonded body.

Claims (1)

[Claims] 1 Approximate the thermal expansion coefficient of two or more ferrite bodies, which are either pre-sintered bodies or single-crystal bodies, within ±5%, and polish each opposing joint surface with No. 600 abrasive grains. The surfaces to be joined should be brought into direct opposing contact with each other at a temperature of 600 to 200°C above the melting point.
A method for manufacturing a ferrite element assembly, characterized in that a pressure of 50 to 500 kg/cm^2 is applied perpendicularly to the opposing surfaces for at least 10 minutes at a low temperature to form a mutual diffusion layer and join them together. .