JPH0368195A - Laminated ceramic board and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve insulation between conductors in reliability even if pinholes occur at the burning of a ceramic layer by a method wherein an insulating layer, which is burnable at a temperature lower than the lowest temperature at which the ceramic layer can be burned, is formed on the surface of the ceramic layer. CONSTITUTION:An alumina printed layer 4a, to which an opening is provided so as to expose a part of a high melting metal inner conductor 3, is formed, and a via-fill conductor layer 5 of high melting point metal conductor is formed in the opening so as to be electrically connected to the inner conductor 3. In the same manner as above, an alumina printed layer 4b, a via-fill conductor 5b, and an alumina printed layer 4c are successively formed. A high melting point metal inner conductor 6 is formed into a prescribed pattern, an alumina printed layer 7a, a via-fill conductor layer 8a, an alumina printed layer 7b,... are successively formed, and a glass printed layer 9 is formed on the uppermost layer 7c. By this setup, even if defects such as pinholes or the like occur in the alumina printed layers 7a, 7b, and 7c, the glass printed layer 9 gets into the defects concerned to prevent a ceramic laminated board of this design from decreasing in insulation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises forming a ceramic layer and a high melting point metal conductor layer alternately, and electrically connecting the high melting point metal conductor layer to form a conductor layer. This invention relates to a ceramic laminate substrate.

[Conventional technology]

Various processes have been developed to form this type of ceramic multilayer substrate. Among these, the green sheet method is often used as a method suitable for multilayering, and the green sheet method is further divided into a printing lamination method and a sheet lamination method.

In particular, the printing lamination method is used for circuit boards with built-in capacitors, etc., taking advantage of the fact that the thickness of each ceramic layer is thinner than that of the sheet lamination method, resulting in a larger parasitic capacitance.

[Problem to be solved by the invention]

By the way, in this printing lamination method, after printing and forming the inner layer conductor, for example, about three layers of aluminum base paste are printed and then fired. It has become clear that if foreign matter such as dirt, dust, squeegee rubber powder, or air gets mixed in when printing this alumina paste, this foreign matter will also be fired during the substrate firing process, causing defects such as pinholes in the alumina layer. .

This defect poses a problem because it may cause a short circuit between the thick film conductor formed on the surface of the substrate and the inner layer conductor in a later process, which causes a decrease in insulation reliability.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to improve the insulation reliability between each conductor.

[Means to solve the problem]

In order to achieve the above object, the ceramic laminate substrate of the present invention has a ceramic layer and a high melting point metal conductor layer having a melting point higher than the lowest firing temperature of the ceramic layer, and In a ceramic laminated substrate formed by electrically connecting to a high melting point metal conductor layer to form a conductor layer, an insulating layer that can be fired at a temperature lower than the lowest temperature at which the ceramic layer can be fired is formed on the surface of the ceramic layer. It is characterized by what it did.

Further, the method for manufacturing a ceramic multilayer substrate of the present invention involves alternately laminating ceramic layers and high melting point metal conductor layers having a melting point higher than the firing temperature of the ceramic layers, and simultaneously firing them at a predetermined firing temperature. forming an insulating layer on the surface of the ceramic layer and firing the insulating layer at a temperature lower than the firing temperature; and electrically connecting the high melting point metal conductor layer on the insulating layer. The method is characterized by comprising a step of forming a conductor layer so as to do so.

[Effect]

With the above structure, even if defects such as pinholes occur in the ceramic layer during firing of the ceramic layer and the high-melting point metal conductor layer, the insulating layer is formed on top of this and fired. Defects can be plugged.

As a result, the conductor layer formed on the insulating layer and the refractory metal conductor layer are completely insulated, improving insulation reliability.

〔Example〕

Hereinafter, the present invention will be explained using embodiments shown in the drawings. FIG. 1 shows a cross-sectional structure of an embodiment of the present invention. In the figure, numeral 1 is an alumina tape, and a through hole 2 is formed in the alumina tape 1, which is made of W (tungsten) or M.

A high melting point metal conductor such as (molybdenum) is buried.

An inner layer conductor 3 made of a refractory metal conductor layer having a predetermined pattern is formed on the alumina tape 1.

Then, a printed layer 4a having an opening such that a part of the inner layer conductor 3 is exposed is formed thereon, and a via fill conductor layer 5a made of a high melting point metal conductor layer is further formed in the opening.
is formed in such a way that it is electrically connected to the inner layer conductor. Similarly, an aluminum-containing printed layer 4b, a via-fill conductor layer 5b, and an aluminum-containing printed layer 4c are sequentially formed thereon.

Then, an inner layer conductor 6 made of a high melting point metal conductor layer is provided thereon.
is formed in a predetermined pattern and further includes a printed layer 7a
, via-fill conductor layer 8a, alumina print layer 7b, via-fill conductor layer 8b, alumina print layer 7c, and via-fill conductor layer 8c are sequentially laminated.

A glass printing layer 9 is formed on the uppermost aluminum printing layer 7c. Further, in order to properly connect the uppermost via fill conductor layer 8c and the thick film conductor 11, a bonding auxiliary layer 1o made of plating with a metal such as Ni, Cu, or Au, or an organic metal, etc. is provided on the via fill conductor layer 8c. is formed. Finally, Cu, Cu,
Ni.

The ceramic laminated substrate of this embodiment is constructed by forming a thick film conductor that is more effective than materials such as Ag and Au. Various chip elements and the like are then formed on the thick film conductor 11 of the ceramic laminated substrate constructed in this way.

Next, the manufacturing process of the ceramic multilayer substrate of this example will be explained in more detail using the flowchart of FIG. First, an alumina green sheet tape to be used as alumina cheese 1 is prepared (step A), and the tape is punched to form through holes 2 (step B). Then, the through hole 2 is filled with a high melting point metal conductor layer by press-fitting or printing (step C), and
Step D): Print a high-melting point metal conductor that will become the inner layer conductor 3 on the tape using a screen printing method, followed by step 100.
Dry the conductor at a temperature of ˜150° C. (Step E). Then, print alumina paste, which will become the printing layer 4a, on this conductor and tape (step F).
Then, the aluminum paste is dried (Step G), and a via fill conductor, which will become the via fill conductor layer 5a, is printed in the opening of the paste (Step H).
, and then continue to dry the conductor (step ■).

Thereafter, the steps from Step F to Step I are repeated to obtain the required thickness (in this example, it is repeated once) to form the alumina paste and via fill conductor that will become the alumina printing 1i14b and the via fill conductor layer 5b. . Then, on top of this, alumina paste is further printed to form the alumina printing layer 4c (step J).
The alumina paste is then dried (step K).

Through the series of steps from chip D to step K described above, -required wiring is formed. Then, by repeating these steps as necessary, multilayer wiring is formed on the tape. Note that in this embodiment, steps D~
The process in step 1 is repeated once, and the conductor becomes the inner layer conductor 6, alumina print layer 7a, via fill conductor layer 8a, aluminum main print layer 7b, via fill conductor Ji8b and alumina print layer 7C. and forming an alumina paste.

Thereafter, a high melting point metal conductor that will become the via fill conductor layer 8c is printed in the same manner (step L), and this conductor is subsequently dried (step M). After that, the substrate in this state is heated to a temperature of about 350'C. After 16 hours of calcination (step N), temperature of 1600°C, Nz 10Hz
Simultaneously firing for 24 hours in +HzO atmosphere (
Step ○). Note that the melting point of the high melting point metal conductor used as the material for the inner layer conductor 3.6 and the via fill conductor layers 5a, 5b, 8a, 8b, and 8c is required to be higher than the lowest temperature at which aluminum can be fired. Ru.

Next, a thick film glass layer that will become the glass printing layer 9 is printed on the entire surface of the alumina printing layer 7C except for the via fill conductor layer 8c exposed on the alumina printing NIC (Step P),
The glass layer is dried at a temperature of 125-150"C (step Q), and then fired for 1 hour at a temperature of 850-900"C in air or N2 atmosphere (step R).

The material of the glass layer to be used at this time is: - Glass used as thick film interlayer glass for boat fishing can be used, and an organic solvent containing glass components, oxides serving as glass crystal nuclei, and ceramics can be used. It is sufficient to print a paste in which a filler such as the like is dispersed. Moreover, by repeating steps P and Q as necessary, a multilayer glass printing layer 9 can be formed.

Next, Ni, Cu or Au is applied to the via fill conductor layer 8c.
The bonding auxiliary layer 10 is formed by plating the top layer (step S) and sintering this plating layer (step T). Incidentally, the sintering process in Step T may be omitted, and the joining aid JailO may be formed by printing a paste of Pt or the like and firing it at a temperature of 850 to 900°C.

Furthermore, the same effect can be obtained even if the thick film glass layer forming steps from P to Q and the bonding layer forming steps S and T are performed in the reverse order. In addition, when the next step of firing the thick film conductor (step ①) is performed in air, the bonding layer is formed first, and the bonding layer is W as the base.

It is also necessary to form an oxidation-resistant layer that can prevent via fill from oxidizing, which is more dangerous than metals that are easily oxidized such as Mo.

Next, Cu,
In order to print a thick film conductor that is more effective than Ni, Ag, or Au based materials (Step U), this conductor is dried and then exposed to a temperature of 850°C, air or N! Baking is performed in the atmosphere for 1 hour,
The manufacturing process of the ceramic multilayer substrate of this example is completed (step ①).

Therefore, in this embodiment formed as described above, each layer formed up to Step M is fired simultaneously in Steps N and O, and then the glass printing layer 9 is fired. As a result, even if defects such as pinholes occur in the alumina print layers 7a, 7b, and 7c during the firing process in steps N and 0, the glass print layer 9 will not fit into the defects when forming the glass print layer 9. It is possible to fill the defect and prevent initial or durability test seating between the upper and lower conductors through the defect.

FIG. 3 is a graph showing the relationship between the number of glass printing layers 9 additionally formed on the aluminum printing layer 7c and the defect (pinhole) depth. In order to evaluate the measurement results under the worst conditions, a defect (pinhole) with a diameter of 100 μm and a depth of 20 am was formed in advance on the alumina printing layer, and a glass printing layer 9 was printed on top of this. This is the value after firing. Moreover, the circle plot in FIG. 3 is the value when the glass film thickness is 20 μm, and the triangular plot is the value when the glass film thickness is 10 μm. From FIG. 3, it can be confirmed that the effect of forming the glass printing layer 9 is significant, and it can also be seen that increasing the number of layers produces a greater effect. In particular, when the glass film thickness is 20 μm and two glass printing layers 9 are formed, even a pinhole as large as 100 μm in diameter can be almost completely filled.

Fig. 4 is a graph showing the relationship between dielectric breakdown voltage and frequency (number of pieces), of which Fig. 4(a) shows the results when the glass printing layer 9 is not formed, and Fig. 4(b) shows the results when the glass printing layer 9 is not formed. The results when glass printing layer 9 was formed are shown. Note that 7 in the figure indicates the average value of the dielectric breakdown voltage. As can be seen by comparing FIGS. 4(a) and (b), when the glass printed layer 9 is formed, the number of ceramic multilayer substrates that break down at a relatively high dielectric breakdown voltage increases, and It can be seen that reliability has improved.

Although the present invention has been described above using the above-mentioned embodiments, the present invention is not limited thereto and can be modified in various ways, for example as shown below, without departing from the spirit thereof.

■The method for manufacturing the ceramic laminated substrate in the above example employs the printing lamination method, but it may also be manufactured by the layer lamination method. In this case, after laminating and firing a plurality of alumina green sheets, A glass printing layer may be formed thereon.

In addition, for reasons related to the manufacturing process of the layer lamination method, and for the thickness of one layer of alumina layer (approximately 60 μm) of the ceramic laminated substrate formed by the printing lamination method, the thickness of the alumina layer formed by the layer lamination method is Because the aluminum layer of the ceramic laminated substrate is sufficiently thick (approximately 200 to 250 μm), there is a relatively low possibility that foreign matter will be mixed in with the layer lamination method, and even if pinholes occur, Even so, there is a small possibility that it will reach the surface of the alumina layer, and therefore, the effects of the present invention are more remarkable when the printing lamination method is adopted. Needless to say, the method for manufacturing the ceramic laminate substrate may be a combination of the printing lamination method and the layer lamination method.

■The ceramic layer used in the present invention may include aluminum nitride a (/IN), mu'
14, C3A1zOs'2S i Ox), etc. can be used. Furthermore, a composite material consisting of glass and ceramics is used for the ceramic layer, and the inner layer conductor material is Ag, Cu, Ni. The glass layer is formed by a process, but instead of printing a paste-like glass layer, a film-like layer is placed on the surface of the 9 layers of 54 sheets in total, and this film-like layer is fired. It may be formed by. Furthermore, as the insulating layer referred to in the present invention, insulating materials other than glass, such as a composite material of ceramic and glass, can be used.
As shown in Figure 2, since it is formed and fired after co-firing the alumina layer etc. in step O, it is necessary to prevent the alumina layer etc. from being re-baked as much as possible when firing the insulating material. Therefore, the insulating material has the effect of improving the reliability of the cell.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a ceramic laminated board according to an embodiment of the present invention, Fig. 2 is a flowchart showing the manufacturing process of the embodiment, and Fig. 3 is a graph showing the relationship between the glass printing layer and defect depth. , FIGS. 4(a) and 4(b) are graphs showing the relationship between dielectric breakdown voltage and frequency. 1... Alumina tape, 3.6... Inner layer conductor, 4a
. 4b, 4c, 7a, 7b, 7cm aluminum printing layer. 5a, 5b, 8a, 8b, 8cm... Via fill conductor layer, 9... Glass printing layer, 11... Thick film conductor. In order to effectively close the holes, it is desirable to use a material that has a low viscosity during printing or firing (for example, 200,000 CPS or less).

Claims (2)

[Claims] (1) A ceramic layer and a high melting point metal conductor layer having a melting point higher than the lowest firing temperature of the ceramic layer are alternately laminated and are electrically connected to the high melting point metal conductor layer to form a conductor layer. What is claimed is: 1. A ceramic multilayer board comprising: an insulating layer sinterable at a temperature lower than the minimum temperature at which the ceramic layer can be sintered; an insulating layer formed on the surface of the ceramic layer. (2) Alternately laminating ceramic layers and refractory metal conductor layers having a melting point higher than the firing temperature of the ceramic layers, and firing them at a predetermined firing temperature at the same time; forming an insulating layer on the insulating layer and firing the insulating layer at a temperature lower than the firing temperature; and forming a conductive layer on the insulating layer so as to be electrically connected to the high melting point metal conductor layer. A ceramic laminate substrate and a method for manufacturing the same, characterized by comprising: