JPS61292988A - Copper metalized ceramic 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 Application of the Invention] The present invention relates to a copper metallized alumina substrate, and particularly to a highly reliable alumina substrate suitable for metallization by plating.

[Background of the invention]

In conventional ceramic substrates, as described in JP-A-59-36948, electrodes are formed by nickel plating on a tungsten conductor and then gold plating, or silver/palladium electrodes are formed. After that, parts are soldered. In this case, the conductor is tungsten or a thick film conductor such as silver or baladicum. This 1
7. ), the conductor resistance was high, making it unsuitable as a low-resistance conductor required for high-frequency circuits, etc. Next, as an example of lowering the resistance, alumina is treated with an alkali metal hydroxide solution and then heat-treated to roughen the surface of the alumina, as described in JP-A-58-104079. After that,
A method of metallizing by performing electroless copper plating is known. In this case, steel metallization on alumina is possible, but it is difficult to simultaneously form it reliably on tungsten. That is, between tungsten and copper, local batteries are likely to form, which is a disadvantage in terms of corrosion resistance. In particular, electroless copper plating has more pinholes than electroless nickel plating, so it is necessary to increase the thickness of the plating film. For this reason, it is not disadvantageous in terms of cost, but also has drawbacks such as the inability to obtain circuit characteristics due to thick plating film thickness that causes etching ellipse or unevenness when forming microstrip lines required for high-frequency circuits. (be.

[Purpose of the invention]

The object of the present invention is to apply nickel plating to the tungsten part using a plating method on a sintered body of a wet substrate printed with a tungsten conductor using a raw alumina sheet, and then apply steel plating to the nickel and alumina substrates. It is an object of the present invention to provide a copper metallized alumina substrate on which a copper metallized alumina substrate is simultaneously formed and patterned using an etching method.

[Invention 4! [Required] The alumina substrate to be used in the present invention may be one on which tungsten is arranged. This alumina substrate is generally made by printing a high-temperature sintered conductor such as tungsten on a raw alumina sheet.
It is sintered in a reduction furnace at a high temperature of about 1600°C.

The alumina of this substrate is roughened using an alkali metal hydroxide or the like, and the oxide on the tungsten surface is also removed. Thereafter, it is immersed in an activating solution consisting of palladium ions and an alkali-soluble complexing agent to replace tungsten and palladium, thereby plating palladium metal nuclei on the tungsten. After that, 5-30% dilute sulfuric acid or 5-30%
In 15% dilute hydrochloric acid, alkaline content is neutralized and at the same time, palladium hydroxide which has become a colloidal residue is washed away. Next, when electroless nickel plating is applied, nickel plating is selectively deposited on the activated tungsten. The thickness of the nickel plating is preferably 3 μm or more, and to further improve reliability, the thickness is preferably about 5 μm. Next, activation with palladium is performed on the nickel surface by immersing it in a hydrochloric acid solution (200-300 mlA) containing 0.01 t'/J to 0.05 f/7 palladium chloride.
Electroless copper plating is applied after adhesion promotion treatment with ~10% aqueous solution. The copper plating thickness may be approximately 1 to 5 μm.

Furthermore, an activation liquid containing palladium and tin ions is used to activate the copper plating and at the same time activate the alumina part. This activation liquid can be used, for example, in Hitachi Chemical's Cedar System or 8HI PLE's Sitalist 6.
It can be activated by a system such as F or accelerator 19.

After activation, a thick steel plating is applied to the entire substrate by electroless copper plating. The plating thickness at this stage may be determined depending on the purpose of the substrate used. Next, a desired circuit pattern is formed by masking and etching using a photoresist method or a printing method. According to the invention,
The substrate on which tungsten is placed can be metallized using the copper plating method, and since the copper metallization is performed later on the tungsten via the tungsten, there are fewer pinholes and corrosion due to local battery action is less likely to occur. . Furthermore, if you want to reduce the film thickness of the steel metallized pattern, plating only copper on tungsten will not only cause pinholes to occur, but when soldering is done on top of this, the copper plating film will diffuse into the solder. This may significantly impair connectivity. In the present invention, since nickel, which is difficult to diffuse into solder, is used, the connection reliability is also high.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

As an example, a single layer structure of tungsten wiring was used. As shown in FIG. 1, a tungsten conductor 2 was printed on an alumina green sheet 1 by screen printing, and then fired in a hydrogen atmosphere furnace at 1600°C. FIG. 2 shows a cross-sectional structure when the sintered substrate is plated with nickel plating 6 of 5 μm, partial copper plating 4 of 3 μm, and then overall steel plating 5 of 15 μm. Figure 5 shows the state in which photoresist is applied to the substrate in Figure 2, exposed and developed using a negative mask, the photoresist is left only in desired areas, and the photoresist is peeled off after etching with cupric chloride etching solution. shows. Tests were conducted on the connection strength and corrosion resistance of the boards completed in this way, and they showed that they were more reliable than conventional thick film method boards, and as shown in Figure 5, the steel metallization was applied directly to the needle surface of the board. A highly reliable steel metallized substrate that can be formed was obtained.

The plating process for manufacturing this substrate is shown in FIG. That is, preheating step 6 for preheating the substrate.
After the substrate was heated to about 250° C. with hot air, it was immersed in molten caustic soda at 30° C. for about 10 minutes to roughen the alumina surface 7. At this time, the tungsten part (tar).

The surface oxidation of Z was simultaneously removed and a strong metallic luster was observed. Next, after cooling 8 was carried out, neutralization 9 was carried out with 10 sulfuric acid. After washing with water, EDTA -2Nα1oy/l
, NaOH-too y/l, PtC1*o,
A first activation treatment of 1° was performed in an activating solution of 12 μm, and then an adhesion promotion treatment 11 was performed with 5% HCl. Subsequently, electroless nickel plating 12 was performed. Next, Pt
C1*oa, o1t/l, HCl2300ml/
After a second activation treatment 13 consisting of nickel and an adhesion promotion treatment 14 using 5% HCl, electroless copper plating 15 was conducted to plate steel only on the nickel.

Next, the third activation treatment 16 is carried out, but the liquid used is
Catalyst 6F manufactured by HIPLH Corporation was used. Furthermore, the same accelerator 19 was used in the adhesion promotion treatment 17. Next, electroless copper plating@20 was performed to metallize the entire board with steel, and Kmm copper steel plating 21 was performed to obtain a film thickness. Next, in a photo-etching step 22, a desired pattern is etched to complete the substrate in the shape shown in FIG.

〔Effect of the invention〕

According to the present invention, since the alumina substrate itself can be metallized with steel at the same time as the tungsten conductor disposed on the alumina substrate, it is particularly effective for high frequency circuits such as tuners that require wiring with low conductor resistance. Moreover, since electroless nickel plating is applied between the tungsten and the copper metallization, which has high corrosion resistance and fewer pinholes, corrosion due to local battery action is less likely to occur. Furthermore, since only the tungsten part is bonded with copper via nickel, the diffusion of copper into the solder during soldering stops at the nickel layer, resulting in high reliability. Of course, compared to Av/Pd thick film or nickel plated conductors, the solder wetting spread is also effective as a printed circuit board.

[Brief explanation of drawings]

FIGS. 1, 2, and 5 are diagrams showing the front side of the copper metallized alumina substrate according to the present invention. Figure 4 shows
FIG. 5 is a diagram showing the process of processing the substrate of FIG. 1 up to FIG. 5; 1. Alumina green sheet and its sintered body, 2.
...Tungsten paste and its sintered body, 6...
Nickel plating, 4... Partial steel plating, 5... Whole steel plating. Representative Patent Attorney Katsutoshi Ogawa ゛-゛Figure 1? Figure 2 lol Figure 3

Claims (1)

[Claims] Copper characterized by selectively plating electroless nickel only on the tungsten conductor on an alumina ceramic substrate, then applying electroless copper plating to the entire substrate, and then forming a copper pattern by etching. Metallized ceramic substrate.