JPH05267849A - Manufacture of ceramic multilayer circuit board - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a method for manufacturing a ceramic multilayer circuit board, which is capable of sufficiently impregnating a through-hole-filled refractory metal conductive layer with copper in a fired ceramic multilayer circuit board. To do. [Structure] Through-hole is made of a porous refractory metal conductive layer 1
The ceramic multi-layer circuit board 11 filled with 2 is fired to produce a jig for copper impregnation, which is composed of an outer container 1, an inner container 2 and a load plate 3 made of ceramics having poor wettability with copper for copper impregnation. An air hole 4 is provided at a position corresponding to a through hole on the bottom of the outer container, the inner container is slidable in the outer container, and a through hole 5 is provided at a position corresponding to the through hole on the bottom.
Copper plate 6 provided with and melting and load plate 3 thereon
And a ceramic multilayer circuit board 1
1 is arranged between the outer container 1 and the inner container 2 and heated to a temperature equal to or higher than the copper melting point to melt the copper plate 6, and the copper melted by the load plate 3 is permeated into the porous refractory metal conductive layer 12. To configure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multilayer circuit board, and more particularly to an improvement in a method of impregnating a porous refractory metal filling a through hole of the board with copper.

[0002]

_2. Description of the Related Art A ceramic multilayer circuit board is 1500 to 1600 ° C. if its firing temperature is alumina (Al ₂ O ₃ ).
And 1800 ° C for aluminum nitride (AlN).
Since the temperature is high, the metal filling the through hole is tungsten (W) or molybdenum (Mo), which are refractory metals, in consideration of co-firing possibility and harmony of thermal expansion coefficient. However, tungsten and molybdenum have the drawback of high resistance.

Proposed methods to remedy this drawback are:
In this method, a conductor such as tungsten is made porous when fired and impregnated with copper or the like to reduce the resistance. In this case, the composition of the conductor paste (tungsten paste) for filling the through holes and forming the wiring layer is tungsten powder, ethyl cellulose as a binder, terpineol as a solvent, and ceramic powder (AlN powder) for adjusting the shrinkage ratio as a porosity imparting agent. Terephthalic acid is added. In the conductor paste, which is a mixture of these, terephthalic acid is insoluble in the solvent and burns out during firing.

When the through holes of the green sheet are filled with such a conductor paste, printed on the wiring layer, and the green sheets are laminated and fired, the mixed terephthaleic acid in the conductor paste is volatilized and there Become pores, and the fired conductive layer (tungsten layer) is porous. In order to impregnate the pores of this porous conductive layer with copper, on the fired ceramics multilayer circuit board, copper pellets are placed, in a reducing atmosphere, heated to a temperature higher than the copper melting point to melt copper, Infiltrate the conductive layer. Since the conductive layer contains low resistance copper, the electric resistance can be lowered.

[0005]

As described above, copper is infiltrated, but copper and ceramics (especially Al
Since N) has poor wettability, ceramics may repel copper and copper may not sufficiently impregnate the metal conductive layer of the through hole. If this happens, the resistivity cannot be lowered sufficiently.

An object of the present invention is to provide a method of manufacturing a fired ceramic multilayer circuit board, which is capable of sufficiently impregnating a through-hole-filled refractory metal conductive layer with copper.

[0007]

The above-mentioned object is to produce a ceramic multilayer circuit board in which through holes are filled with a porous refractory metal conductive layer by firing, and to produce molten copper in the refractory metal conductive layer. In a method of manufacturing a ceramics multilayer circuit board comprising impregnation, a copper impregnation jig is prepared which comprises an outer container, an inner container and a load plate of ceramics having poor wettability with copper for copper impregnation. An air hole is provided at a position corresponding to a through hole on the bottom of the container, the inner container is slidable in the outer container, a through hole is provided at a position corresponding to the through hole on the bottom, and a melting copper plate and the above The load plate is housed, and the ceramic multilayer circuit board is arranged between the outer container and the inner container, and is heated to a temperature equal to or higher than the copper melting point to melt the copper plate, and the load plate melts And the copper is accomplished by the method of manufacturing a ceramic multilayer circuit board, wherein the infiltrating refractory metal conductive layer of the porous.

Further, the form of the copper impregnating jig may be changed. In that case, a copper impregnating jig consisting of an outer container, an inner container and a load plate made of a ceramic having poor wettability with copper is prepared. , The outer container has a bottom, the inner container is slidable in the outer container, and a through hole is provided at a position corresponding to a through hole in the bottom and accommodates a melting copper plate and the load plate thereon. The load plate is provided with an air hole at a position corresponding to a through hole, the copper plate is disposed between the outer container and the inner container, and the ceramic multilayer circuit board is provided with the inner container and the load plate. Placed between and to melt the copper plate by heating above the copper melting point, and permeating the copper melted by the load plate into the porous refractory metal conductive layer through the through holes of the inner container. Characteristic ceramic multilayer circuit board The foregoing objects are achieved by the production method.

The refractory metal is preferably tungsten or molybdenum.

[0010]

According to the present invention, the copper plate is melted by heating, and at that time, the surrounding outer container and inner container are materials having poor wettability, so that the copper is repelled, and the pressure from the load plate causes the entire liquid copper to melt. Join. The pressurized molten copper is (1) extruded downward from the through hole at the bottom of the inner container, or (2) extruded upward from the through hole at the bottom of the inner container to fill the porous through hole. It reaches the metal conductive layer and infiltrates like a capillary phenomenon and infiltrates the whole.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings by way of embodiments and comparative examples of the present invention. First, a ceramic multilayer circuit board is manufactured as follows. Aluminum nitride powder, binder, solvent,
Mix with a dispersant to make sludge and make a green sheet by the doctor blade method. A through hole is formed in this green sheet by punching, and each of the tungsten paste (conductor paste) samples 1 to 11 having the composition shown in Table 1 is printed to fill the through hole and form a wiring layer. The tungsten paste is a mixture of tungsten powder (particle size: 2 μm), ethyl cellulose, terpineol, ceramic powder (AlN powder) and terephthalic acid. Paste sample 1 does not contain terephthalic acid.

[0012]

[Table 1]

Eight green sheets of this conductor paste printing are laminated under pressure, the outer shape is cut, and the binder is removed (degreasing).
Nitrogen (N ₂₎ atmosphere 500 ° C. in carried out at 4 hours, followed by, 1800 ° C. The firing in a nitrogen (N ₂₎ atmosphere, 12
Do in time. The through-hole filled tungsten layer after firing is made porous by bubbles due to burning of terephthalic acid. In the case of the paste sample 1 containing no terephthalic acid, it does not become porous by firing, but becomes a dense tungsten layer.

EXAMPLE As shown in FIGS. 1 to 3, a copper impregnating jig comprising an outer container 1, an inner container 2 and a load plate 3 made of ceramics (AlN) having poor wettability with copper is prepared. Air holes 4 are formed in the bottom of the outer container 1 at positions corresponding to the through holes (below the tungsten layer 12 of the ceramic multilayer circuit board 11), for example, 16
The number is provided (however, the number is six in FIG. 3).
The inner container 2 is made slidable inside the outer container 1,
At the position corresponding to the through hole on the bottom (tungsten layer 12
A through hole 5 is provided). These air holes 4
The diameter of the through hole 5 is slightly larger than the diameter of the through hole. The load plate 3 is an AlN plate of approximately the same size as the inner size of the inner container 2 (Fig. 2), and a copper plate 6 is provided between the load plate 3 and the inner container 2.
It is designed to sandwich.

Using this copper impregnating jig, as shown in FIG. 1, the produced ceramic multilayer circuit board 11 is arranged between the outer container and the inner container, and the copper plate 6 is arranged between the inner container 2 and the load plate. 3, and the whole is heated above the melting point of copper in a hydrogen (H ₂ ) reducing atmosphere to melt the copper plate 6. 1230
During heating for 30 minutes at ℃, pressure (0.5-1.0 g /
cm ² ). Added molten copper to a porous tungsten layer 1
Infiltrate 2. After cooling, the ceramic multilayer circuit board 11 is removed from the copper impregnation jig, and both surfaces of the obtained board 11 are surface-polished to finish.

The resistance of the through-hole filled tungsten layer 12 of the ceramic multilayer circuit board 11 was measured for each of the tungsten paste samples 2-11 (Table 1) before copper impregnation and after impregnation and is shown in Table 2. Results were obtained. The resistance value was the best value among the 19 tungsten layers. In the paste sample 1, the resistance of the tungsten layer 12 of the substrate manufactured by firing was measured without performing the copper impregnation treatment. 1 and 3, the number of the through-hole filling tungsten layers 12 is nine and the number of the air holes 4 is nine.

[0017]

[Table 2]

Comparative Example Copper was applied to the through-hole-filled tungsten layer 12 (Samples 2 to 11 in Table 1) of the above-mentioned ceramic multilayer circuit board 11 according to a conventional method, as shown in FIG. With the copper pellets 13 placed on, the copper impregnation was performed by heating the copper pellets 13 to a temperature not lower than the melting point of the copper in a reducing atmosphere. The resistance of the tungsten layer 12 was measured before and after copper impregnation and the results shown in Table 3 were obtained. The resistance value was the best value among the 16 tungsten layers. The values for the paste sample 1 are as described above.

[0019]

[Table 3]

As can be seen from these tables, if the through-hole filled tungsten layer becomes porous, the resistance value becomes larger than that when it is dense (Sample 1), and the resistance value can be lowered by impregnating copper. it can. Even so, in the case of the comparative example (conventional example), only the sample 10 was lower than the resistance value of the tungsten layer in the sample 1 which was not made porous, and it can be said that the impregnation state is not good. The resistance value of the sample 10 is extremely low, and it is presumed that there is a special factor. On the other hand, in the case of the present invention, the copper impregnation jig improves the impregnation state in the tungsten layer from most of the paste, and the resistance value becomes lower than that of sample 1 except for samples 6 and 7. The degree of reduction in the resistance value is greater in the present invention than in the comparative example.

Further, another embodiment of the present invention is shown in FIGS. 5 and 6. As the copper impregnating jig, similar to the above-described embodiment, the outer container 21, the inner container 2 and the load plate 23 made of ceramic (AlN) having poor wettability with copper are used. There are no air holes, and the load plate 23 is provided with, for example, 16 air holes 24 (however, 9 in FIG. 6). The inner container 2 is the same as the above-mentioned embodiment, and the outer container 21
The inside is slidable, and the through hole 5 is provided at the bottom of the through hole 5 at the position corresponding to the through hole (above the tungsten layer 12).
Is provided. The diameters of the air holes 24 and the through holes 5 are slightly larger than the diameter of the through holes. Load plate 2
Reference numeral 3 is an AlN plate having substantially the same size as the inner size of the inner container 2 (FIG. 6), and is directly mounted on the ceramic multilayer circuit board 11.

Using this copper impregnating jig, as shown in FIG. 5, a copper plate 6 is arranged between an outer container and an inner container, and the produced ceramic multilayer circuit board 11 is placed on the inner container 2. ,
The load plate 3 is placed thereon, and the whole is heated above the copper melting point in a hydrogen (H ₂ ) reducing atmosphere to melt the copper plate 6. 1
During heating at 230 ° C. for 30 minutes, pressure (0.5 to 0.5) is applied to the load plate 3.
1.0 g / cm ² ) was added and molten copper was passed through the through hole 5 of the inner container 2.
To penetrate into the porous tungsten layer 12. After cooling, the ceramic multilayer circuit board 11 is removed from the copper impregnating jig, and both surfaces of the obtained board 11 are surface-polished to finish.

The resistance value of the tungsten layer 12 of the multilayer circuit board manufactured in this manner was almost the same as that of the embodiment.

[0024]

As described above, according to the manufacturing method of the present invention, the porous through-hole filling tungsten layer (refractory metal layer) can be sufficiently impregnated with copper, and the resistance value can be increased. Lower. Furthermore, in the conventional method,
There was a through hole that copper pellets placed due to vibration during the infiltration heat treatment shifted from the through hole position, or molten copper was repelled by ceramics and shifted from the through hole, and did not penetrate sufficiently into the porous tungsten layer. In the invention, this is not the case, and all the through-hole filled tungsten layers have good copper impregnation.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a copper impregnating jig and a ceramic multilayer circuit board according to a first embodiment of the present invention.

FIG. 2 is a top view of the copper impregnating jig of FIG.

3 is a bottom view of the copper impregnating jig of FIG. 1. FIG.

FIG. 4 is a schematic sectional view of a ceramic multilayer circuit board for explaining conventional copper impregnation.

FIG. 5 is a schematic cross-sectional view of a copper impregnating jig and a ceramic multilayer circuit board according to a second embodiment of the present invention.

FIG. 6 is a top view of the copper impregnating jig of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Outer container 2 ... Inner container 3 ... Load plate 4 ... Air hole 5 ... Through hole 6 ... Copper plate 11 ... Ceramic multilayer circuit board 12 ... Through hole filling tungsten layer 13 ... Copper pellet 21 ... Outer container 23 ... Load plate 24 … Through holes

Claims (3)

[Claims] 1. A ceramic multi-layer circuit board, which is produced by firing a ceramic multi-layer circuit board having through holes filled with a porous high-melting-point metal conductive layer, and impregnating the high-melting-point metal conductive layer with molten copper. In the manufacturing method of 1., for impregnating copper, a copper impregnating jig including an outer container (1), an inner container (2) and a load plate (3) made of a ceramic having poor wettability with copper is prepared. The bottom of the container (1) is provided with an air hole (4) at a position corresponding to a through hole, the inner container (2) is slidable in the outer container, and the bottom has a through hole (5) at a position corresponding to the through hole. ) Is provided and contains a melting copper plate (6) and the load plate (3) thereon, and the ceramic multilayer circuit board (1)
1) is placed between the outer container (1) and the inner container (2), heated to a temperature equal to or higher than the copper melting point to melt the copper plate (6), and the copper melted by the load plate (3) is removed. A method for manufacturing a ceramics multilayer circuit board, characterized in that the porous high-melting-point metal conductive layer (12) is permeated. 2. A ceramic multi-layer circuit board, which is produced by firing a ceramic multi-layer circuit board having through holes filled with a porous high-melting-point metal conductive layer, and impregnating the high-melting-point metal conductive layer with molten copper. In the manufacturing method of (1), an outer container (21), an inner container (2) and a load plate (23) made of ceramics having poor wettability with copper due to impregnation with copper
A copper impregnating jig is prepared, the outer container (21) has a bottom, the inner container (2) is slidable in the outer container, and the bottom has a through hole at a position corresponding to a through hole ( 5) is provided and contains a melting copper plate (6) and the load plate (23) thereon, and the load plate (23) is provided with air holes (24) at positions corresponding to through holes, The copper plate (6) is placed between the outer container (21) and the inner container (2), and the ceramic multilayer circuit board (11) is connected to the inner container (2) and the load plate (23). And melting the copper plate (6) by heating the copper plate above the melting point of copper and melting the copper melted by the load plate (23) through the through hole (24) of the inner container. Manufacture of a ceramic multilayer circuit board characterized by being impregnated into a metal conductive layer (12) Method. 3. The method according to claim 1, wherein the refractory metal is tungsten or molybdenum.