JPH0377306A - Formation of electrode - Google Patents

Abstract

PURPOSE:To lower cost and to reduce irregularity in an electrode by a method wherein a glass frit film is formed on a dielectric ceramic, a copper film by an electroless plating operation is formed and the copper film is baked at a specific temperature in an atmosphere of an inert gas to form the electrode. CONSTITUTION:The surface of a dielectric ceramic 1 is coated, in 1mum or less, with a glass frit as a pretreatment; this assemble is baked at a temperature lower than the melting point of glass and at a temperature of 250 to 850 deg.C; a glass frit film 2 is formed. Then, this assembly is immersed in a hydrochloric- acid acidic solution of stannous chloride; it is washed with water and a sensitization treatment is executed. The assembly is immersed in a hydrochloric-acid acidic aqueous solution of palladium chloride; it is washed by water and an activation treatment is executed. Then, this assembly is immersed in an electroless plating liquid which is composed of copper sulfate, EDTA, Rochelle salt, caustic soda, formalin and a stabilizer to form a metal copper electrode. Then, this assembly is washed with water and dried; it is heat-treated at at 400 to 900 deg.C in an air current of nitrogen; after this heat treatment, a grinding face 4 at an end face is ground to obtain a dielectric resonance element.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for forming electrodes of dielectric ceramics, particularly a method for forming copper electrodes on dielectric cores used in dielectric ceramics and dielectric filters by electroless plating. Regarding.

(Prior Art) Conventionally, when forming an electrode on a high frequency dielectric ceramic, silver has generally been used as the electrode. When silver was used, the silver baking method was applied. For this purpose, silver powder is mixed with glass frit, other inorganic oxides, an organic binder, a dispersant, and a solubilizing agent to form a paste. Then, this paste is applied by means such as printing or dipping, and a silver electrode is formed on the dielectric ceramic by heat treatment. Further, in response to the recent demand for cost reduction of parts, various methods of forming electrodes by the instant method have been developed. This method involves first degreasing the surface of the dielectric ceramic, first roughening the surface with acid, etc., then sensitizing it with stannous chloride, etc., and then chemically reacting with palladium chloride (S
Palladium is precipitated by oxidation treatment (n"+Pd"'→Sr+"+Pd), followed by activation treatment, followed by copper silicate-ethylenedeaminetetramine (EDTA), Rochelle salt-
It was common practice to perform electroless plating of copper in a plating solution containing formalin-caustic soda, followed by washing and drying. Furthermore, a method of heat-treating the plated copper electrode in an inert gas has also been used.

(Case M that the invention attempts to confront) Dielectric loss Q0 of a dielectric resonant element in a dielectric ceramic
is determined by the Q of the dielectric ceramic itself and the Q of the electrode, and can be expressed as the following equation.

1/Qa=1/Q, +i/Q.

Here, the electrical conductivity of the metal constituting the electrode itself greatly contributes to the Q of the electrode, so silver, which has the highest leakage rate among metals, has conventionally been used as the electrode material. However, when using a conventional silver electrode, the presence of glass frit, inorganic oxide, etc. in the silver electrode reduces the original electrical conductivity of silver, and the electrical conductivity of copper is 5.81
It ended up being lower.

In the end, even though expensive silver is used, Q expressed by the above formula is lowered. Trying to increase Qo,
Glass lift has a contradictory problem in that if the amount of inorganic oxide etc. is reduced, the adhesion of the silver electrode will deteriorate.

Furthermore, there are many problems when forming copper electrodes using conventional electroless plating methods. That is, copper electrodes formed by electroless plating have poor adhesion and are not suitable for practical use even if they are electrolessly plated directly onto dielectric ceramics, so surface treatment with acid or the like is performed. However, dielectric ceramics are made up of many composition systems depending on their dielectric properties, and the sintering state of dielectric ceramics is not uniform, and the acid corrosion resistance and the selection of the acid used depend on many factors. They are intricately intertwined, so there is no one thing that can be decided on a competitive basis, and copper electrodes formed by electroless plating as they are have the drawbacks of lower conductivity and lower Q than copper foil. Furthermore, leaving it at high temperatures,
Heat treatment at high temperature or heat cycle test (-55℃)
There are problems such as deterioration of performance characteristics (particularly Q0 drop and resonance frequency drift).

The present invention solves the above-mentioned conventional problems, and aims to provide a method of forming a copper electrode at low cost and high reliability.

(Means for Solving the Problems) In order to achieve the above object, the present invention first applies a glass frit of 1 or less on the surface of a dielectric ceramic as a pretreatment, and bakes it at a temperature below the melting point of the glass to create a glass frit. Forms a frit film. Thereafter, it is sensitized with a stannous chloride solution and activated with a palladium chloride solution to form a copper electrode by electroless plating. Furthermore, after that, in an inert gas atmosphere, the temperature is 400 to 90°C, which is higher than the melting point of the glass frit.
A copper electrode is formed by heat treatment at 0°C.

(Function) Therefore, the electrode obtained by the above method is compared to the silver electrode obtained by the baked electrode method.

It is inexpensive and has little variation in electrodes, and when compared to electrodes made using conventional electroless plating methods, there is no problem with surface treatment of dielectric ceramics caused by acid, and the bonding is achieved using glass frit, which provides uniformity and high conductivity. It has very good dielectric properties, combining the characteristics of baked electrodes and plated electrodes.

(Example) FIG. 1 shows a manufacturing process in an example of the present invention. In FIG. 1, 1 is a dielectric ceramic, 2 is a glass frit film, 3 is a copper plating film, and 4 is a ground surface.

Next, the manufacturing process will be explained. First, as a dielectric ceramic, BaO-8s20. -Tie, system element (Bao
-NdiO, -Ti02 type elements) and Ba0-TiO type elements were used as test pieces. The test pieces are 64mm x 6°8m square and 9mm long.
5 cabinets, the afterword is 6.8 m5 x 6.8 squares and length 1.2.
4m! =I did. These elements are immersed in a suspension of powdered glass mainly composed of zinc borosilicate-alumina and zirconia to attach a glass frit of 1- or less, and then heated at a temperature in the range of 100 to 150°C. After drying, it is baked using an electric oven in the air at a temperature within the range of 200 to 900°C to form a glass film (Fig. 1 (b)).
Then, it was sensitized by immersing it in an acidic solution of stannous chloride in hydrochloric acid and washing with water.

Next, primary copper sulfate, ED"r A,
Rochelle salt, caustic soda 1. A gold scrap copper electrode (with a thickness of 10 to 20 microns) was formed by immersing it in an electroless plating solution consisting of formalin and a stabilizer (Fig. 1 (e)), then washing with water, drying, and placing it in a nitrogen stream. at 300-1000℃,
Heat treatment was performed for 30 to 60 minutes (FIG. 1(d)). After the heat treatment, the ground surface 4 of the end face was ground to form a dielectric resonant element.

Although dielectric ceramic was used in the above embodiment, other insulators or semiconductor ceramics may be used as long as the ceramic composition can withstand the heat treatment described above.

Table 1 Table 1 shows the processing conditions and characteristics when forming a copper electrode on a dielectric ceramic. In Table 1,
Example No. 1 is a case where the electrode is formed without pretreatment, and Q is low and adhesion strength cannot be obtained. No. 2
~N009 is an example in which a glass frit is heat-treated from a temperature below the melting point to a temperature above the melting point to form an electrode, and then heat-treated at 400 to 950°C in a nitrogen stream.

No, 4. It was found that when heat treatment was performed at a temperature higher than the melting point of the glass frit in the pretreatment as in No. 5, the bond of Q6 was also low, and the interface between the ceramic and the electrode was loose and swollen because no adhesion strength was obtained. Examples No. 6 to No. 9 are examples in which the melting point of the glass frit is changed. No,
, 12~No, 17. No. 19 to No. 22 are examples in which the material system of the dielectric ceramic was changed.

No, L4. No, 17. No. 22 was an example in which the pretreatment was performed at a temperature higher than the melting point of the glass bullet, and even though the ceramic material was changed, the QIl was low, and blistering occurred at the interface between the ceramic and the electrode. Comparative example No. 10° No. 11
．． No, 18. No. 23 is an example in which a copper electrode was formed by etching with a hydrofluoric acid mixture.

As a result, almost satisfactory characteristics were obtained depending on the material. However, there are many materials to choose from, and there is a great dependence on ceramic composition and loft, making it impossible to obtain satisfactory properties for some materials.

(Effects of the Invention) As is clear from the above examples, the present invention is lower in cost and more reliable than in the case where electrodes are formed by baking silver paste, etc., and has effects suitable for industrial mass production. .

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram of an embodiment of the present invention. 1...Dielectric ceramic, 2...Glass frit film, 3...Copper metal base film, 4...Grinded surface.

Claims (4)

[Claims] (1) Form a glass frit film on a dielectric ceramic, form a copper film by electroless copper plating on the glass frit film, and heat the copper film at 400°C to 900°C in an inert gas atmosphere. An electrode forming method characterized by forming an electrode on a dielectric ceramic by baking. (2) The method for forming an electrode according to claim 1, wherein the glass frit film is formed at a temperature below the melting point of the glass frit and from 250°C to 850°C. (3) Form a glass frit film on the dielectric ceramic, form a copper film by electroless copper plating on the glass frit film, and apply one type of copper, silver, or solder on the copper film. An electrode forming method characterized by forming an electrode film by electrolytic plating. (4) The electrode forming method according to claim (1), (2) or (3), wherein the electrode is formed by mechanically removing unnecessary portions of the electrode.