JPS6318357B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ceramic multilayer wiring board used for hybrid integrated circuit components. (Prior Art) Conventionally, as shown in FIG. 5, a multilayer wiring board used in a hybrid integrated circuit has a ceramic green sheet 21 coated with a high melting point metal mainly composed of a high melting point metal such as tungsten or molybdenum. A conductor paste layer and a plurality of insulating paste layers each having an opening 23 through which a part of the conductor paste layer is exposed are stacked together, a paste layer identical to the conductor paste layer is printed in the opening 23 of the top layer, and then the paste layer is placed in a reducing atmosphere. to form a high melting point metal conductor layer 22 and an insulating layer 2.
4 is formed, an iron metal plating layer 25 made of nickel or the like is applied on the metal conductor layer 22, and an oxidation-resistant protective layer made of a gold-silver alloy layer is screen printed, then melted, and then a thick layer of silver or the like is applied on top of that. It is known that a ceramic multilayer wiring board is obtained by printing a film conductor paste layer and firing it at about 850° C. in an oxidizing atmosphere to form an iron metal plating layer 25, an oxidation-resistant protective layer 26 and a thick film conductor layer 27. was. Further, as shown in FIG. 6, for example, an iron metal plating layer 25 such as nickel and an oxidation-resistant protective layer 26 made of a gold-silver alloy are directly placed on the high melting point metal conductor layer 22 exposed in the opening 23 of the uppermost layer. There were also known examples of providing . (Problems to be solved by the invention) In the ceramic multilayer wiring board having the above structure,
Compared to a board that does not have an oxidation-resistant protective layer on the high-melting-point metal conductor layer, oxygen can be prevented from entering the high-melting-point metal conductor layer, but depending on the type of thick film paste used to make the thick film conductor layer, the oxidation-resistant protective layer There was a drawback that the oxidation prevention function of the layer and the conductor oxidation prevention function of the outer peripheral insulating layer of the exposed conductor part were impaired. In other words, in both the conventional examples shown in Figures 5 and 6, when silver paste with a small Pd/Ag ratio is used as the thick film paste, the thick film conductor layer not only has no oxygen blocking effect but also lacks oxidation protection. The drawback is that the gold-silver alloy in the layer reacts with the thick film paste, reducing the gold/silver ratio and reducing the amount of oxygen barrier, making it impossible to effectively prevent oxygen from entering the iron metal plating layer. Ta. In addition, in the example shown in Figure 5, if there is a large amount of metal oxides such as lead and zinc, which have a weaker bonding force with oxygen than tungsten and molybdenum in the glass component of the thick film paste, Another drawback was that the conductor oxidized. The purpose of the present invention is to eliminate the above-mentioned problems and provide a ceramic multilayer wiring board that can prevent oxygen from entering the board and provide stable conductivity regardless of the type of thick film paste. . (Means for Solving the Problems) The ceramic multilayer wiring board of the present invention has acid-resistant exposed conductor parts of a ceramic board in which insulating layers made of ceramic and conductor layers mainly composed of a high-melting point metal are laminated alternately. In a ceramic multilayer wiring board on which a oxidation-resistant protective layer is formed and a thick-film conductor layer that is sintered in an oxidizing atmosphere is formed, Ag and Pd are the main components between the oxidation-resistant protective layer and the thick-film conductor layer. It is a noble metal powder and is characterized by providing an auxiliary conductor layer in which the amount of Pd in the noble metal component is 10 mol% or more. (Function) The details of the present invention will be explained one by one for each step with reference to FIGS. 1 and 2. First, a ceramic green sheet 1 containing alumina, beryllia, etc. as the main components was prepared by a known doctor blade method, etc., and cut into the dimensions required for a hybrid integrated circuit board.
Prepare. Next, on the green sheet 1, a conductor paste whose main component is a high-melting point metal such as tungsten or molybdenum, that is, a metal with a melting point higher than the firing temperature of the ceramic green sheet 1 and a metal with a lower electric resistance, and a part of the conductor paste are applied. A green sheet 1 having an opening that exposes a portion of the green sheet and an insulating paste mainly made of the same ingredients are alternately printed by screen printing to form a high melting point metal conductor layer 2 made of conductor paste as shown in FIGS. 1 and 2. An insulating layer 3 made of insulating paste is formed. Note that the number of layers of the high melting point metal conductor layer 2 and the insulating layer 3 is not limited, and may be determined according to the purpose. Then, the ceramic green sheet 1 on which the paste forming the conductive layer 2 and the insulating layer 3 is printed is fired in a reducing atmosphere. The firing conditions are determined based on the composition of the ceramic green sheet 1 and the components of the conductor paste, and the firing is performed at 1400 to 1800°C for 5 to 180 minutes. After firing, an iron metal plating layer 4 such as nickel is formed on the exposed high melting point metal conductor layer 2. The purpose of plating with iron metal is to improve wettability with precious metals. The thickness of the iron metal plating layer 4 is suitably 1 to 5 microns. The method for forming the iron plating layer 4 is as follows:
Either electrolytic or electroless plating method may be used, and the selection is made depending on whether or not the electrode can be taken out. After forming the iron metal plating layer 4, heat treatment may be performed in a reducing atmosphere at 800 to 1200°C for 5 to 30 minutes in order to improve the adhesion strength between the iron metal plating layer 4 and the high melting point metal conductor layer 2. Next, a paste containing gold and silver is screen printed on the iron metal plating layer 4 to form a paste layer on the iron metal plating layer 4 that forms the oxidation-resistant protective layer 5 made of an alloy of gold and silver. . The thickness of the oxidation-resistant protective layer 5 varies depending on the firing temperature of the thick film conductor layer, but is approximately 15
~45μ is appropriate. Next, the ceramic wiring board on which the paste layer forming the oxidation-resistant protective layer 5 was formed was heated at 1000 to 1100
A heat treatment is performed in a non-oxidizing atmosphere at a temperature of 0.degree. C. to melt and alloy the paste layer, thereby forming an oxidation-resistant protective layer 5 made of a gold-silver molten alloy. The melting temperature is
The temperature is 1000℃ or higher, but in order to suppress diffusion into the oxidation-resistant protective layer made of an alloy of iron plating, the temperature is 1100℃.
The following melting temperatures are preferred: If the melting time is too long, the diffusion of the iron metal plating 4 into the oxidation-resistant protective layer 5 will increase, so a melting time of 5 to 30 minutes is appropriate. Further, on the oxidation-resistant protective layer 5 and the insulating layer 3 of the heat-treated ceramic substrate, the metal component is mainly composed of silver and palladium, and if palladium is 10 mol % or more, and glass is included, the glass component is lead oxide. A desired circuit pattern is printed using an auxiliary conductor paste containing 50% by weight or less of zinc oxide in total and a thick film conductor paste whose main component is silver or the like. Next, the printed matter is fired in an oxidizing atmosphere to form an auxiliary conductor layer 6 and a thick film conductor layer 7, thereby obtaining the ceramic multilayer wiring board of the present invention. The firing conditions depend on the components of the thick film paste, but the firing conditions are 800 to 850.
°C for 5 to 20 minutes is sufficient. Thereafter, passive elements such as resistors are formed on the thick film conductor layer 7, and other circuit component leads are wire bonded or soldered on the thick film conductor layer 7 to form an integrated circuit. (Example) Hereinafter, an example will be described with reference to FIGS. 3 and 4. A ceramic green sheet 1 having a thickness of 0.8 mm was prepared by mixing 90% by weight of alumina, additives such as silica and magnesia, and an organic binder such as polyvinyl butyral as ceramic components using a doctor blade method. Next, a conductive paste was prepared by adding ethyl cellulose as a printing aid to the metallizing components of 98% by weight of tungsten powder and 2% by weight of silica, and an insulating paste was prepared by adding ethylcellulose to the powder having the same composition as the green sheet as a printing aid. A part of the conductor paste was exposed and alternately printed on the green sheet 1 to obtain a laminate in which a conductor layer 2 and an insulating layer 3 were formed. Next, the laminate was heated at a heating rate of 300°C/hour in a mixed atmosphere of hydrogen and nitrogen with a dew point of 35°C, held at 1550°C for 2 hours, and then cooled at a cooling rate of 600°C/hour.
Sintered in time. Then, on the high melting point metal conductor layer 2 exposed on the obtained ceramic wiring board, an iron metal plating layer 4 made of nickel with a thickness of 3 μm was formed by electroless plating in a hydrogen boride bath. Next, the nickel-plated ceramic substrate was heat-treated at 950°C for 5 minutes in a hydrogen atmosphere, and then a paste made of gold and silver powder containing 25 mol% gold and 75 mol% silver with an acrylic binder added as a printing aid was used. Screen printing is performed on the iron metal plating layer 4 so that the printing thickness is approximately 30μ, and then
The pastes were melted and alloyed at 1100° C. according to the melting point of each composition paste to form a high melting point metal conductor layer 5 made of an alloy of gold and silver. Furthermore, after screen printing a thick film auxiliary conductor paste having the components shown in Table 1 on the high melting point metal conductor layer 5, a thick film conductor paste (Shoei Chemical D-
4022) was screen printed and baked at 850°C for 10 minutes in the air, and as shown in Figures 3 and 4, an iron plating layer 4 and an oxidation-resistant protective layer 5 were placed on the high melting point metal conductor layer 2, respectively. Thus, a ceramic multilayer wiring board of the present invention provided with an auxiliary conductor layer 6 and a thick film conductor layer 7 was obtained. In order to compare the deterioration of conductivity after oxidation firing of the ceramic multilayer wiring board thus obtained, the electrical resistance between the thick film conductor layers 7 was measured, and the oxidation of the conductor layer around the oxidation-resistant protective layer was also observed. did. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, the conduction resistance is low,
Samples with a judgment of 〇 for no oxidation of the conductor layer have a high palladium content in the metal components in the auxiliary conductor paste.
It can be seen that the total amount of lead oxide and zinc oxide is 7.5% by weight (10% by mole) or more, and the total amount of lead oxide and zinc oxide in the glass component in the auxiliary conductor paste is 50% by weight or less. The present invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the above-mentioned embodiment, the structure of the substrate was used as an example as shown in FIGS. 3 and 4, but any type of substrate can be used as long as there is an auxiliary conductor layer between the oxidation-resistant protective layer and the thick film conductor layer. Effects can be obtained. (Effects of the Invention) As is clear from the detailed explanation above, according to the ceramic multilayer wiring board of the present invention,
By forming the auxiliary conductor layer between the oxidation-resistant protective layer and the thick film conductor layer, oxygen can be prevented from penetrating into the high melting point metal conductor layer regardless of the type of thick film paste used to form the thick film conductor. This makes it possible to form a wide variety of pastes, which can be used in a wide variety of fields. Furthermore, since the auxiliary conductor layer contains more than a certain amount of palladium as a metal component, there is little deterioration of the oxygen blocking effect of the oxidation-resistant protective layer, and the amount of lead oxide and zinc oxide as glass components is less than a certain amount, so the conductor is exposed. It is possible to obtain a ceramic multilayer wiring board that is free from oxidation on the outer periphery of the parts and has stable conductivity.

[Brief explanation of the drawing]

1 and 2 are sectional views of essential parts of an embodiment of the ceramic multilayer wiring board according to the present invention, and FIGS.
The figure is a sectional view of a main part of another embodiment of a ceramic multilayer wiring board according to the present invention, and FIGS. 5 and 6 are sectional views of main parts of a conventional ceramic multilayer wiring board. 1,21...ceramic green sheet, 2,
22... High melting point metal conductor layer, 3, 24... Insulating layer, 4, 25... Iron metal plating layer, 5, 26... Oxidation-resistant protective layer, 6... Auxiliary conductor layer, 7, 27... Thickness Membrane conductor layer, 23...opening.

Claims (1)

[Scope of Claims] 1. An oxidation-resistant protective layer is formed on the exposed conductor portion of a ceramic substrate in which an insulating layer made of ceramic and a conductor layer mainly composed of a high-melting point metal are laminated alternately, and an oxidation-resistant protective layer is formed on the exposed conductor part, and an oxidation-resistant protective layer is formed on the exposed part of the conductor. In a ceramic multilayer wiring board on which a thick film conductor layer is formed, which is sintered inside, a noble metal powder containing Ag and Pd as main components is used between the oxidation-resistant protective layer and the thick film conductor layer, and the amount of Pd in the noble metal component is A ceramic multilayer wiring board characterized by providing an auxiliary conductor layer consisting of 10 mol% or more. 2. The ceramic multilayer wiring board according to claim 1, wherein when the auxiliary conductor layer contains glass, the total amount of lead oxide and zinc oxide in the glass component is 50% by weight or less.