JPS61288486A - Manufacture of ferrite imbedded type substrate - 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 [Field of Industrial Application] The present invention relates to a method for manufacturing a circuit board in which a circuit is constructed by embedding ferrite in an alumina ceramic substrate and forming a desired conductive pattern on the surface thereof. The present invention relates to a method of manufacturing a substrate suitable for configuring, for example, a ferrite-embedded circulator, etc., although the present invention is not limited thereto.

[Conventional technology] Alumina ceramic, mixed substrate with ferrite disk, so-called "
"Ferrite embedded circulators" are conventionally known. This type of circulator has a lower loss than a monolithic type circulator whose substrate is made of ferrite only because the dielectric loss (tan δ) of alumina ceramics is smaller than that of ferrite material, and mixers, isolators, etc. are integrated. This technology is attracting attention because it has the advantage of being able to be integrated into integrated circuits.

In order to embed a ferrite disk in an alumina substrate, conventionally,
Two methods have been developed: One method is to form a circular hole 12 in a sintered alumina substrate lO and press-fit a tapered sintered ferrite disk 14 into the hole 12, as shown in FIG. 3A. be. The other one is a sintered ferrite disk 14 as shown in FIG. 3B.
In this method, the sintered alumina substrate 10 is fitted into a hole 12 formed in the sintered alumina substrate 10, and both are fixed with an adhesive such as glass.

[Problems to be Solved by the Invention] In this type of circulator, the loss largely depends on the degree of fit between the ferrite disk and the hole formed in the alumina substrate.

Therefore, in the case of the former, that is, press-fitting by taper processing,
In order to exhibit good characteristics and increase reliability, the holes in the ferrite disk and alumina substrate must be finished with an accuracy of about 1 to 3 μm. For this reason, the alumina substrate must be drilled with a laser beam and precision ground with a diamond grindstone, and the ferrite disk must also be tapered to a predetermined precision using a diamond grindstone or the like. Therefore, it has disadvantages of high cost and poor productivity.

Furthermore, the latter method of fixing using adhesive similarly requires considerable processing precision, and since adhesive is used, it is inevitably susceptible to heat and lacks reliability.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above,
The fit between the alumina sheet and the ferrite material does not require very strict precision, the alumina material is easy to drill, the bonding strength between the alumina material and the ferrite material is high, and there is little variation in electromagnetic properties. An object of the present invention is to provide a method for manufacturing a ferrite-embedded substrate.

[Means for Solving the Problems] The present invention, which can achieve the above objects, forms holes in a non-sintered sheet made of low-temperature sintered alumina material, fits sintered ferrite into the holes, and This is a method of manufacturing a ferrite-embedded substrate that is integrated by sintering.

When borosilicate glass powder is mixed with alumina powder, 80
It is possible to sinter at a relatively low temperature of about 0 to 900°C, and by adjusting the particle size of the raw material powder to 2 to 3 μm or less, it is possible to obtain the same strength as a normal alumina sintered body. I know it.

As shown in FIG. 1A, in the present invention, a hole 22 of a predetermined size is formed in the green (unsintered) sheet 2o of the glass-mixed alumina material for embedding the ferrite material. For example, the hole and the outer edge of the substrate can be simultaneously formed into a predetermined shape by punching with a press using a mold having a predetermined shape. Then, a ferrite plate 24, which has been sintered in advance and has a shape slightly larger than the hole 20, is fitted into the hole formed in the unsintered alumina sheet (see Figure B).

Next, the glass-alumina material is sintered at a low temperature of about 800 to 900°C, and is bonded and integrated with the ferrite plate.

Thereafter, the surface of the ferrite-embedded substrate 26 obtained by sintering is ground using a grinding wheel 28 or the like, as shown in FIG. (See the same diagram).

The ferrite to be used should be one that matches the required electromagnetic properties. For example, using a disc-shaped ferrite material such as YIG is a method in which multiple holes are formed in an alumina sheet and the ferrite material is embedded in them. For example, a plurality of circuit elements can be formed at the same time, and an integrated circuit in which mixers, isolators, circulators, etc. are integrated can also be realized.

Effect] Since holes are formed in the alumina sheet in an unsintered state, it can be done extremely easily with high precision using a press or the like. Further, since the ferrite plate is sintered in advance at a predetermined high temperature, it can exhibit sufficient electromagnetic properties. Further, since the re-sintering is performed at a low temperature, it does not have any adverse effect on the ferrite.

When the alumina sheet is sintered at a low temperature, the ferrite and alumina substrate can be bonded with sufficient strength and without gaps due to the adhesive strength of the glass contained inside and the shrinkage of the sheet during sintering. Since the alumina sheet shrinks, even the ferrite material can be formed to a certain sufficient degree of precision that good results can be obtained even without precision.

[Example] Alumina powder with a particle size of 1 to 3 μm or less and borosilicate glass (S i O * 70% by weight, Bz
26% by weight of Oa, 2% by weight of Nag, 2% by weight of AIto3, and 1% by weight of K) were blended in approximately equal weight ratios.

A mixture of this alumina powder and borosilicate glass59.
5% by weight, 3% ethyl alcohol as binder
3% by weight, 5.5% by weight of polyvinyl alcohol, and 2% by weight of diptylphthalate were added and mixed for 20 hours in a polyethylene pot containing alumina balls. Pour the mixed slurry into a predetermined thickness of 1 to 2 using the doctor blade method.
An alumina sheet of mm) was prepared. Next, from room temperature to 1
After gradually raising the temperature to 00° C. and removing the binder, it was punched into a predetermined shape by pressing using a mold. In this case, the hole in the alumina sheet is approximately 0.01 smaller than the ferrite disk.
``The diameter was reduced by about 0.02 mm.

On the other hand, a sintered YIG (yttrium-iron-garnet)-based ferrite disk, which had been pre-processed to a predetermined size, was fitted into the hole formed in the alumina unsintered sheet.
Sintering was carried out at ~900°C for 1-2 hours.

After sintering, the substrate surface was ground to make it smooth, and then strip lines were formed by gold plating, etching, and other methods.

Table 1 shows the characteristics of the alumina substrate and YIG ferrite.

Table 1 and FIG. 2 are diagrams showing an example of the characteristics of the embedded microstrip circulator thus obtained.

[Effects of the Invention] The present invention is a method of fitting a sintered ferrite material into a hole formed in a sheet of an unsintered low-temperature sintered alumina material and sintering it at a low temperature to integrate it. The accuracy of the fit between the ferrite disks only needs to be relatively loose, and drilling in the alumina sheet is extremely easy since it is done in an unsintered state, and the bonding strength between the alumina material and the ferrite material after sintering is very low. is sufficiently high, and since there is no gap between the two, variations in characteristics are reduced, and compared to conventional mating methods using taber processing or fixing methods using adhesives, it is easier to mass produce and can significantly reduce costs. It has some excellent effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the manufacturing procedure of a ferrite-embedded circulator to which the method of the present invention is applied, and FIG. 2 is a diagram showing an example of the characteristics of the circulator obtained by the present invention.
3A and B are 20...low-temperature sintered alumina unsintered sheet, 22...hole, 24...sintered ferrite disk, 26...ferrite embedded type substrate, 30...・Conductive pattern. Patent applicant Fuji Electrochemical Co., Ltd. Agent Shigeru Estimate Figure 1A Figure 2A Figure 3B

Claims (1)

[Claims] 1. A ferrite-embedded substrate characterized in that a hole is formed in a non-sintered sheet made of a low-temperature sintered alumina material, a sintered ferrite is fitted into the hole, and the ferrite is integrated by sintering at a low temperature. Production method.