JPH0148672B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a technology for connecting W or Mo conductors and Cu conductors in a multilayer wiring board formed by alternately forming Cu conductor wiring and glass coating layers on a co-fired multilayer board of W or Mo conductors. . Recently, multilayer wiring boards that combine co-fired multilayer board technology of W or Mo conductors and thick film multilayer wiring technology using Cu conductor materials have become available. This method has high conductivity of Cu conductor,
Less likely to cause migration, W or Mo
It is approximately 20% shorter than the signal speed of a conductor (thick film formation method), making it ideal for high-speed applications such as computers and television tuners. Moreover, the Cu wiring layer formed on the upper part of the multilayer wiring board can also be used as a design change part when mounting different types of LSIs. The conventional method for making this multilayer wiring board is to screen print a paste prepared by using W or Mo powder in a solvent on a green sheet provided with through holes to fill the through holes and form wiring parts, and then print the paste as desired. A number of the substrates are laminated and bonded, and after removing the resin, they are sintered in a non-oxidizing zero atmosphere to obtain a multilayer substrate with the W or Mo portion exposed on the upper surface. On this exposed W or Mo
After applying Ni plating and printing Cu paste on top of it and baking it in a nitrogen atmosphere, the top surface is covered by screen printing with glass paste and baking it in a nitrogen atmosphere. The Cu paste printing, baking, glass paste printing, and baking steps were repeated to form desired 2 to 5 layers. According to this conventional method, the adhesion between the W or Mo conductor + Ni plating + Cu conductor is good, but by repeating the Cu paste baking and glass paste baking processes, it is possible to make good connections up to three layers. However, as the number of times of baking increases as the product is made up of 4 to 5 layers, the bond at the connection portion becomes weaker, and connection failures are becoming more common. No matter how many layers are laminated by increasing the number of times of baking, the present invention maintains a strong bond without causing abnormalities in the connection and wiring parts, and when used as a multilayer wiring board, conduction resistance does not change over time. As a result of intensive research to create something, I discovered the following method. The gist of the present invention will be described with reference to an abbreviated sectional view of a multilayer wiring board in FIG. 1A and a partially enlarged sectional view in FIG. In a method of connecting W or Mo conductors 2 and Cu conductors 3 of a multilayer wiring board formed by alternately forming multiple layers with glass coating layers 4, Ni plating 5 is applied to the connection portions 7 of the W or Mo conductors 2, and Further, Ni paste 6 is printed on top and baked in a hydrogen/nitrogen atmosphere, and then Cu paste 3 is printed and baked in a nitrogen atmosphere to form a connection between W or Mo conductor 2 and Cu conductor 3. It is. By adopting the present invention, a strong connection with almost no change in conduction resistance can be achieved even after repeated baking 10 times, and it can also be used in practical conduction tests as a multilayer wiring board.
Even after 4,000 hours, no abnormalities were observed and the process is currently continuing. The reason why the conductor connection method of the present invention was able to make a strong connection is that a Ni layer, which easily reacts with both, is interposed between W or Mo and Cu, and the W or Mo layer, which is oxidized in a nitrogen atmosphere, is plated with Ni. This is thought to be due to the fact that the Ni paste coating ensured complete coverage (direct Ni paste coating was insufficient), and that the Ni paste coating bit into the uneven surface in contact with the Cu paste, forming an even stronger reaction bonding layer. Ru. The reason why Cu and glass were baked in a nitrogen atmosphere was to prevent the strength of the glass layer from deteriorating due to hydrogen. Examples will be described below, but the present invention is not limited thereto within the scope of the gist of the present invention. A slurry with an alumina content of 96% prepared by adding plasticizers, dispersants, solvents, etc. was casted onto a carrier film using a known doctor blade method to form a green sheet with a thickness of 0.5 mm.
This was cut to a size of 120 x 60 mm to make 10 pieces, nine of these pieces were made with through holes for connection to the upper and lower layers, and basest made of W metal powder was filled into these holes. Form the desired circuit wiring on the top surface of the above 10 sheets using W paste by screen printing,
After drying, 10 sheets were stacked and pressed together, with 10 sheets as the top layer and 1 sheet with no conduction to the bottom layer as the bottom layer. After removing the resin, this was sintered at 1550°C in a mixed atmosphere of hydrogen and nitrogen to obtain a multilayer board. Ni plating is applied to a thickness of 3 to 5 μm on the W metallization exposed on the top surface of this substrate, and a paste made of Ni powder is applied on top to a thickness of 15 to 20 μm.
M was applied by clean printing and baked at 850°C in a mixed atmosphere of hydrogen and nitrogen. Next, the desired circuit wiring is routed over the Ni metallization.
The thickness was measured using commercially available Dupont Ci paste (No.9922).
Form wiring by screen printing 15 to 20 μm,
Baked at 850°C in a nitrogen atmosphere. Screen printing was repeated twice on the top surface of this Cu metallization with commercially available Dupont glass paste (No. 4175) to form a coating layer with a thickness of 30 to 40 μm, and after drying, it was baked at 850°C in a nitrogen atmosphere. Ta. The above steps of printing circuit wiring with Cu paste, baking, glass paste coating printing, and baking were repeated to form five layers, and the desired multilayer wiring board was manufactured. Comparative Example A multilayer wiring board was manufactured in the same manner as in the example except that the Ni paste printing and baking steps were omitted on a co-fired multilayer board with 10 layers of W wiring formed using the same method as in the above example. Table 1 shows the conduction resistance measured for each layer of Cu paste wiring printed, baked, glass paste printed, and baked on the co-fired substrate of W wiring in the above Examples and Comparative Examples.

[Table] (Note) × indicates a disconnection.
As is clear from Table 1, Ni on W metallization
The comparative product, which is plated and metallized with Cu, has a higher conduction resistance as the number of times it is baked increases.
), a disconnection occurs. On the other hand, with the product of the present invention consisting of W metallization, Ni plating, Ni paste baking, and Cu metallization, there is no increase in conduction resistance even when the number of baking increases, and no abnormality was observed in the 5-layer product, resulting in good conductor connection. The multilayer wiring board has been completed, and the practical energization test for this board is currently continuing without any abnormalities after 4,000 hours.

[Brief explanation of drawings]

FIG. 1A shows an abbreviated sectional view of the multilayer wiring board of the present invention, and FIG. 1A shows an enlarged view of circle B in the figure. 1... Ceramic substrate, 2... W or Mo circuit wiring, 3, 3'... Cu conductor wiring, 4... Glass coating layer, 5... Ni plating, 6... Ni paste baking layer, 7... Connection Department.

Claims (1)

[Claims] 1 Cu on a co-fired multilayer substrate of W or Mo conductor
In a method for connecting a W or Mo conductor and a Cu conductor in a multilayer wiring board formed by alternately forming multiple layers of conductor wiring and glass coating layers, Ni is added to the connection portion of the W or Mo conductor.
It is characterized by plating, printing Ni paste thereon, baking it in a hydrogen/nitrogen atmosphere, and then printing Cu paste and baking it in a nitrogen atmosphere to form a connection between the W or Mo conductor and the Cu conductor. Conductor connection method for multilayer wiring boards.