JPS6346595B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing ceramic multilayer wiring boards used in hybrid integrated circuit components. Conventionally, the first method for manufacturing hybrid integrated circuit boards has been
As shown in the figure, a first conductor layer 2 whose main component is a high melting point metal such as tungsten or molybdenum is formed on a ceramic green sheet 1, and an insulating layer 2 is formed on the first conductor layer 2 by opening a part of the conductor layer 2. After the layer 3 is printed and formed, it is fired in a reducing atmosphere, and then a thick film conductor paste such as silver is printed on the openings of the first conductor layer 2 and the insulating layer 3 and fired in an oxidizing atmosphere to form the second layer 3.
It is known that a ceramic multilayer wiring board can be obtained by forming a conductor layer 4 of. However, since the second conductor layer 4 is fired in an oxidizing atmosphere, the first conductor layer 2 is oxidized and its electrical resistance becomes high, making it unsuitable for use as a hybrid integrated circuit board. For this reason, attempts have been made to plate the openings of the first conductor layer 2 with an oxidation-resistant noble metal such as gold, or to make the composition of the first conductor layer 2 oxidation-resistant. However, with the plating method, the thickness of the gold plating cannot be adjusted.
Even if the thickness is 2μ, if the firing temperature of the thick film paste is 700℃ or higher, the first conductor layer will be oxidized and the first conductor layer will be oxidized.
Even if platinum was added to the conductor layer 2, if the firing temperature was increased to 650° C. or higher, the first conductor layer would be oxidized, making it unsuitable for use as a hybrid integrated circuit board. Therefore, there are restrictions on the selection of thick film pastes that can be used for the second conductor layer. The present invention has been made to eliminate the above-mentioned drawbacks, and is a ceramic multilayer structure obtained by firing a thick film conductor layer in an oxidizing atmosphere on a ceramic substrate provided with a conductor layer mainly composed of a high-melting point metal. In a method of manufacturing a wiring board, a conductor layer containing a high-melting point metal as a main component is plated with nickel, and then a noble metal layer containing 25 to 90% by weight of silver and 10 to 75% by weight of gold as a main component is formed on the nickel plating. but silver is 25~90
% by weight, the sum of gold and palladium is 10-75% by weight,
Furthermore, a ceramic multilayer wiring is produced by forming a noble metal layer containing palladium in a range of 30% by weight or less, melting the noble metal layer by heat treatment, printing a thick film conductor layer on the melted noble metal layer, and firing it in an oxidizing atmosphere. This is a method of manufacturing a substrate. The details of the present invention will be sequentially explained for each step of the method of the present invention according to the flowchart shown in FIG. 2 and the block diagram shown in FIG. First, a ceramic green sheet 1 containing alumina, beryllia, etc. as a main component is adjusted by a known doctor blade method or the like to prepare a ceramic green sheet 1 having dimensions required for a hybrid integrated circuit board. Next, a conductive paste whose main component is a high melting point metal such as tungsten or molybdenum, that is, a metal whose melting point is higher than the firing temperature of the ceramic green sheet 1 and whose electrical resistance is low, is prepared and applied as a screen onto the ceramic green sheet 1. The first conductor layer 2 having a desired circuit pattern is printed by printing or transfer printing. Next, an insulating layer 3 is formed on the first conductive layer 2 by screen printing or transfer printing with an insulating paste so that a part of the first conductive layer 2 is opened. The first conductor layer opened by the insulating layer 3 is for electrical connection with the second conductor layer as will be explained later. The insulating paste used has the same components as the ceramic green sheet. The number of the first conductor layer and the insulating layer is not limited to one layer, respectively. For example, as shown in FIG. 4, a plurality of conductor layers 2, 2 and a plurality of insulating layers 3, 3 may be used. In this case, the opening for electrically connecting the conductor layers is formed using the same component as the first conductor layer. The ceramic green sheet on which the first conductive layer and the insulating layer are printed is fired in a reducing atmosphere. The firing conditions are determined by the composition of the ceramic green sheet and the components of the high melting point metal paste, but the firing conditions are 1400℃.
5 minutes to 180 minutes at ~1800°C. After firing, a nickel plating layer 5 is formed by nickel plating on the first conductor layer 2 exposed in the opening of the insulating layer. The reason for nickel plating is to improve the wettability with precious metals, which will be explained later, and to improve the first conductor layer when firing the second conductor layer in an oxidizing atmosphere.
This is to prevent oxidation of the conductor layer. Therefore,
The thickness of the nickel plating may be selected depending on the type of noble metal, its heat treatment temperature, and the firing temperature of the second conductor layer, but is usually 1 to 5 microns. The selection of electrolytic and electroless plating methods for nickel plating is determined depending on whether or not a plating electrode is required. After nickel plating, heat treatment at 800 to 1200°C to improve the adhesion strength between the nickel plating layer and the first conductor layer.
Heat treatment may be performed in a reducing atmosphere for 5 to 30 minutes. Next, the main components are 90-25% by weight of silver and 10-75% by weight of gold.
The nickel-plated layer 5 is made of a noble metal layer 6 whose main component is a precious metal with a range of % by weight (including those in which part of gold is replaced with palladium of 30% by weight or less).
Form on top. The methods include simply placing a metal or alloy foil on the nickel plating layer, forming it by plating, and forming it using a printing paste. In the case of printing, the appropriate thickness is about 30μ. The reason why the precious metal components are specified above is that when the thick film conductive paste is melted in the subsequent process and then fired in an oxidizing atmosphere, if the silver content is 90% by weight or more, oxygen will be dissolved in the molten precious metal. This is because the oxygen barrier properties are impaired and the nickel plating surface is oxidized, increasing the conduction resistance.The reason why the main components other than silver are gold and palladium is that they are completely dissolved in silver, so oxygen in the silver is removed. This is because it has the effect of suppressing solid solution.
The reason why gold is 75% by weight and palladium is 30% by weight or less is because the underlying nickel dissolves into the precious metal during melting, reducing the purity of the precious metal, forming an oxide film on the surface of the precious metal, and increasing conduction resistance. This is to prevent this from happening. However, if the silver content exceeds 90% by weight, or the total amount of gold or gold and palladium is less than 10% by weight, the oxygen blocking effect of the melted alloy will be weakened, and the
Since conductivity is impaired due to oxidation during firing in an oxidizing atmosphere at ℃, the content of silver must be 90% by weight or less, and the content of gold or gold and palladium must be 10% by weight or more. Next, the ceramic substrate on which the noble metal layer 6 is formed is heat treated. The heat treatment temperature depends on the components of the precious metal layer, but is selected depending on the firing temperature of the second conductor layer, which is below 1450°C, which is the melting temperature of nickel, and will be described later, and is between 960°C and 1400°C, which is the temperature at which the noble metal layer melts.
℃ for 5 to 30 minutes. A second conductive layer 7 forming a desired circuit pattern is printed on the noble metal layer 6 and insulating layer 3 of the heat-treated ceramic substrate 1 using a thick film conductive paste containing silver or the like as a main component. The second conductive layer is not limited to a conductive paste, and a resistive paste or the like can be used as necessary. Next, the printed second conductor layer is fired in an oxidizing atmosphere to obtain a ceramic multilayer wiring board. The firing conditions depend on the ingredients of the thick film paste, but the temperature is 700 to 850.
°C, 50-20 minutes. Example In addition to 90% by weight of alumina as a ceramic component,
After mixing additives such as silica and magnesia with organic binders such as polyvinyl butyral and creating a ceramic green sheet with a thickness of 0.8 mm using the doctor blade method, 98% by weight of tungsten powder and 2% by weight of silica are placed on the ceramic green sheet. A first conductor layer is formed by screen printing using a metallization paste prepared by adding a printing aid to the metallization component of After forming an insulating layer by screen printing, leaving an opening with a diameter of 0.5 mm for electrical connection with the second conductor layer, the dew point is 35°C.
Temperature increase rate 300℃/hour, 1550℃ in hydrogen atmosphere,
After holding for 2 hours, sintering was performed at a cooling rate of 600°C/hour. Next, the first part of the opening of the sintered ceramic substrate is
A 3μ thick nickel layer was deposited on the conductor layer by electroless plating in a hydrogen boride bath. Next, the plated ceramic substrate was heat treated at 1200℃ for 30 minutes in a hydrogen atmosphere, and then screen printed with a paste having the noble metal composition shown in Table 1 to a printing thickness of about 30μ.
The noble metal was melted at 1400°C for 10 to 30 minutes to match the melting point of the paste with each noble metal composition. Next, after silk-screen printing silver-platinum paste (Showa Kagaku product number D-4021) and silver-palladium paste (Showa Kagaku product number D-4344), which are thick film conductive pastes, Those printed with paste (D-4021) were heated at 700℃ in air for 10 minutes, and those printed with silver-palladium paste (D-4344) were heated at 850℃ in air.
After baking for 10 minutes, the first conductor layer 2 is formed as shown in Figure 5.
A ceramic multilayer wiring board having a plurality of second conductor layers 4, 4 provided thereon was obtained. In order to compare with the present invention, in addition to the above ceramic multilayer wiring board, one in which only the first conductor layer 2 was formed and one in which the first conductor layer 2 was plated with nickel and then heat treated were prepared. A second conductor layer was formed using the same thick film conductive paste as the wiring board. The electrical resistance between the second conductor layers of the ceramic multilayer wiring board thus obtained was measured. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, the ceramic multilayer wiring board obtained by the present invention has a second conductor layer,
In other words, a circuit pattern formed by printing a thick film paste and firing it in an oxidizing atmosphere has a low electrical resistance, and the method can be easily implemented using the equipment conventionally used for manufacturing ceramic multilayer wiring boards. This is a major contribution to the development of the electronics industry.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a conventional ceramic multilayer wiring board, FIG. 2 is a process flowchart for explaining the present invention, and FIGS. 3 to 5 are ceramic multilayer wiring obtained by the present invention. FIG. 2 is a sectional view of a main part showing an example of a substrate. DESCRIPTION OF SYMBOLS 1... Ceramic substrate, 2... First conductor layer, 3...
Insulating layer, 4, 7... Second conductor layer, 5... Nickel plating layer, 6... Precious metal layer.

Claims (1)

[Claims] 1. In a method for manufacturing a ceramic multilayer wiring board obtained by firing a thick film conductor layer on a ceramic substrate provided with a conductor layer containing a high melting point metal in an oxidizing atmosphere, The conductor layer as the main component is plated with nickel, and then a noble metal layer containing 25 to 90% by weight of silver and 10 to 75% by weight of gold as the main components is formed on the nickel plated, and then the noble metal layer is melted by heat treatment. A method for manufacturing a ceramic multilayer wiring board, which comprises printing a thick film conductor layer on the molten noble metal layer and firing it in an oxidizing atmosphere. 2. In a method for manufacturing a ceramic multilayer wiring board obtained by firing a thick film conductor layer on a ceramic substrate provided with a conductor layer mainly composed of a high melting point metal in an oxidizing atmosphere, the conductor layer mainly composed of a high melting point metal is used. After forming a noble metal layer on the nickel plating, the main components of which are 25 to 90% by weight of silver, 10 to 75% by weight of gold and palladium in total, and 30% by weight or less of palladium, and then heat-treated. A method for manufacturing a ceramic multilayer wiring board, characterized by melting the noble metal layer, printing a thick film conductor layer on the melted noble metal layer, and firing it in an oxidizing atmosphere.