JPH0226872A - Window for high frequency transmission - Google Patents

Abstract

PURPOSE:To prevent the breaking of a window material due to thermal stress produced by high-frequency waves with high output by using AlN-based ceramics having a specified heat conductivity or above and superior high-frequency wave transmitting property. CONSTITUTION:This window for transmitting microwaves is made of AlN-based ceramics having >=50W/m.K heat conductivity. AlN ceramics contg. >=95vol.% AlN and having <=10 dielectric constant, <=0.001 dielectric loss and >=20kg/mm<2> bending strength is preferably used in the form of a dense sintered body having <5% porosity. In the case of a low AlN content, the heat conductivity of the ceramics is reduced and the window material is broken by heat generated by the absorption of microwaves. In the case of only AlN, it is difficult to obtain a dense sintered body and airtightness is not ensured, so a small amt. of a sintering aid is desirably added.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention (a) Industrial Application Field The present invention relates to a long-life high-frequency transmission window that is excellent in vacuum tightness and high-frequency transmission.

(b) Conventional technology High-frequency waves such as high-power microwaves are used as energy in accelerators, etc., but vacuum tightness is maintained when inputting and outputting microwaves to high-vacuum microwave generation equipment such as Talistron. In addition, a window is used to transmit microwaves and not attenuate them. As a window material, it has high strength and low dielectric loss (
A material with a small tan δ) is preferable, and is mainly made of U, O,
Ceramics are used.

(c) Problem to be solved by the invention Conventional β, 0. Window materials made of aluminum are inexpensive and have excellent airtightness and dielectric loss. The problem has come into focus.

Therefore, there has been a need to develop window materials with higher performance.

B6 Structure of the Invention (a) Means for Solving the Problem As a result of various studies on microwave transmission windows, the present inventors have found that extremely high performance can be achieved by using ceramics containing AlN (aluminum nitride) as the main component. It was discovered that a window of That is, the window of the present invention is characterized in that ceramics containing AItN as a main component is used as the window material.

FIG. 1 shows a specific example of the invention.

(b) Function The microwave transmission window of the present invention is made of ceramics containing Aff N as a main component. Preferably, it is a dense sintered body containing 95% or more of AnN by volume and having a porosity of less than 5%, and a thermal conductivity of 50 w/mk or more and a dielectric constant of 10.
Below, dielectric loss is 0.001 or less, bending strength is 20k
Use AIN ceramic consisting of 100 g/mm" or more.

When the content of Al2N is small, the thermal conductivity becomes small,
Window materials are destroyed by the heat generated by absorption of microwaves.

Since it is difficult to obtain a dense sintered body using only AuN and airtightness cannot be ensured, it is desirable to add a small amount of sintering aid. As a sintering aid, an oxide of the I1ra group such as Y2O5 or an Ila group oxide such as CaO can be added in an amount of 10% by weight or less. The sintering aid may deteriorate the dielectric properties of MN, so it is preferable to keep it in a small amount.

Furthermore, if the porosity increases, airtightness cannot be maintained, making it difficult to function as a window material.

When the dielectric constant and dielectric loss increase, the microwave transmittance decreases, and the heat generated by the window material becomes significant.

The AρN ceramics are attached to the waveguide by a known method. However, care must be taken because the thermal expansion difference between the waveguide and metal materials such as Cu is large, resulting in large brazing strain.

High melting point metallization (W.

After N1 plating, airtight brazing can be performed using Ag brazing.

This will be explained below using examples.

Example AβN powder (average particle size 0.4μ, oxygen content 1.0% by weight, metal impurities 0.1% or less) with Y 20
3 powder was added in an amount of 1.0% by weight, and 10 parts by weight of paraffin wax was added thereto, and after drying, a pressed body of φ60×10T was obtained using a -axis press at 2t/C[11].

After removing the binder in N2, the pressed body was sintered in N2 at 1900°C for 5 hours, and the obtained sintered body was ground all around to obtain a diameter of 50X.
A 5T window material was manufactured. Apply W paste to the outer periphery of the ceramic, bake it at 1600℃ in N2, and
1 plating was applied to 2μ. Furthermore, a microwave window was manufactured by soldering Ag into a φ50 Cu waveguide.

When conducted in a microwave transmission experiment, A (120).

The microwave attenuation was at the same level as the window material, and the window material was not destroyed even when the microwave output was increased by 100%.

As described in detail about the invention, according to the present invention, it is possible to realize a high-performance high-frequency window that has excellent transmittance and can withstand the transmission of high-power high-frequency waves, and is extremely practical. .

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention. The symbols in the figure indicate the following. ■ is the window ■ is the waveguide ■ is the airtight brazed part in Figure 1 ■ 114;

Claims (1)

[Claims] (1) A high-frequency transmission window characterized by using ceramics whose main component is AlN, which has a thermal conductivity of 50 w/mk or more and is excellent in high-frequency transmission.