JPH0682921B2 - Method for manufacturing ceramic printed circuit board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a ceramic printed circuit board used as an electronic substrate.

[Background technology]

2. Description of the Related Art A printed circuit board provided inside an inverter or the like is mounted with an electric component, an IC, or the like, through which a large current is applied and which generates a large amount of heat. For this reason, it is required that the substrate of the printed circuit board made of an insulating material has excellent withstand voltage characteristics and high thermal conductivity.

In order to satisfy this requirement, a ceramic that is fired into a sintered body is used as the insulating material of the substrate.

A printed circuit board provided with this ceramic sintered substrate is shown in FIGS. 6 (a), 6 (b) and 7. FIG. As shown in the figure,
This ceramic printed circuit board 1 is a ceramic sintered substrate 2
And a conductor layer 3 bonded to the surface thereof to form a wiring circuit,
It has a metal layer 4 bonded to its back surface and bonded to an external heat dissipation fin (not shown). Such a ceramic wiring circuit board 1 is mainly manufactured by the following three methods.

(Manufacturing method) A paste made of W, W-Mo, or Mo-Mn is baked at a high temperature on the front and back surfaces of the ceramic sintered substrate by using the W paste method, the W-Mo method, and the Mo-Mn method, and then 5 Form a 15 μm metallization layer. After that, Ni on this metallized layer
Is thinly plated to form a Ni layer, and a copper plate is attached onto the Ni layer by brazing to manufacture a ceramic wiring circuit board.

This method is the most common method. However, according to this method, a hydrogen-reducing atmosphere furnace of 1500 ° C. or higher is required at the time of metallization, which causes a problem of high cost. Also, during the brazing process, a copper plate
There is also a problem that air enters between the Ni layer and air bubbles, and the air bubbles reduce the heat dissipation of the ceramic wiring circuit board.

(Manufacturing method) Place a metal such as a copper plate to be a conductor layer or metal layer punched out in a circuit pattern on a ceramic sintered substrate, control the O ₂ concentration, and directly in an N ₂ atmosphere at 1000 to 1100 ° C. The direct bond method of adhering is used.

According to this manufacturing method, there is a problem that it is very difficult to control the atmosphere and the temperature of the furnace used for joining a metal such as a copper plate and the ceramic sintered substrate. Further, since it is difficult to apply a force from the outside to each of the copper plate and the ceramic sintered substrate when they are bonded to each other, air enters the bonding surface to generate air bubbles,
Swelling occurs in the conductor layer and metal layer of the ceramic printed circuit board. If the thickness of the metal is increased, the ceramic wiring circuit board may warp or cracks may occur in the ceramic sintered substrate due to the difference in the coefficient of thermal expansion. There is also a problem that it is very difficult to form a highly accurate pattern.

(Manufacturing method) A paste made of W, W-Mo, or Mo-Mn is baked at a high temperature on the front and back surfaces of the ceramic sintered substrate by using the W paste method, the W-Mo method, and the Mo-Mn method, and then 5 Form a 15 μm metallization layer. After that, Ni on this metallized layer
Is thinly plated to form a Ni layer, and a Cu layer of 100 to 250 μm is further formed by electroplating.

When a ceramic wiring circuit board is manufactured by this method, as shown in FIG. 6 (a), since the wiring circuit pattern is arranged in an island shape, a conductive material is used to conduct each of these islands. It becomes very difficult to take Since the Cu layer is formed to a desired thickness by electroplating, there are problems that the thickness is uneven and the pattern accuracy is difficult to obtain.

As described above, if ceramic is used as the insulating material for the printed circuit board, it is sufficient if the thickness of the insulating layer made of this ceramic is 20 to 300 μm. In order to further improve the heat dissipation of this ceramic printed circuit board, the ceramic substrate may be made thinner. However, if the thickness of the ceramic substrate is reduced in order to improve the heat dissipation of the ceramic wiring circuit board according to the above-mentioned manufacturing methods, there is a problem that the strength of the ceramic wiring circuit board decreases.

Currently, the main ceramic materials used are alumina, aluminum nitride, silicon carbide, beryllia and the like. Copper is generally used as the metal used as the conductor layer and the metal layer. Since copper is very active, it is plated with Ni or the like.

As described above, the conventional ceramic printed circuit board has various problems and drawbacks.

It has been desired to provide a ceramic wiring circuit board that solves this problem.

[Object of the Invention]

The present invention has been made in view of such circumstances, and an object thereof is to supply a ceramic wiring circuit board which is inexpensive, has good heat dissipation, and has good withstand voltage.

[Disclosure of Invention]

In order to achieve the above object, the present invention is a method for producing a ceramic printed circuit board comprising a conductor layer for forming a wiring circuit on the front surface of a ceramic substrate and a metal layer having a heat dissipation effect on the back surface, A ceramic substrate having recesses formed on both sides in advance is characterized in that a conductor layer for forming a wiring circuit is formed in the recess on one side and a metal layer having a heat dissipation function is embedded in the recess on the other side. The gist is the method of manufacturing a ceramic printed circuit board.

The present invention will be described in detail below with reference to its embodiments.

1 (a), (b) and FIG. 2 show an embodiment of a ceramic wiring circuit board according to the present invention. As shown in the figure, the ceramic printed circuit board 5 includes a ceramic sintered substrate 6, a conductor layer 7 which is bonded to the surface so as to be embedded and forms a wired circuit, and a back surface of the ceramic sintered substrate 6. And a metal layer 8 which is bonded so as to be embedded in the above and is bonded to an external heat dissipation fin (not shown). This ceramic wiring circuit board 5
As shown in FIGS. 3 and 4, first, the conductor layer 7
And the ceramic sintered substrate 6 in which the embedded portions 9 and 10 in which the metal layer 8 is embedded is formed is prepared and manufactured.

This ceramic sintered substrate 6 is produced by any of the following methods.

A ceramic green sheet with a thickness of 0.5 to 2.0 mm is extruded or created by a doctor blade method,
After cutting into a desired size, a conductor layer to be a wiring circuit pattern and an embedded portion in which a metal layer adhered to the heat radiation fin is embedded are ground by using a milling method. The ceramic green body thus formed is fired at a high temperature (1200 to 1800 ° C.) to produce the ceramic sintered substrate.

Using a slurry solution method, ceramic green is cast into a ceramic green body so as to have a structure equivalent to that of the ceramic sintered substrate. After that, this ceramic green body is thoroughly dried to a high temperature (1200
To 1800 ° C.) to produce the ceramic sintered substrate.

A ceramic green body is formed by an injection molding method so as to have a structure similar to that of the ceramic sintered substrate, and a ceramic sintered substrate is produced through a bisque firing and a main firing process.

A direct pressure press method using the adjusted ceramic powder is used to form a ceramic green body having a desired size and shape and fire it to produce this ceramic sintered substrate.

The ceramic sintered substrate is prepared by using a semi-dry method, embossing method, hot pressing method, hydrostatic pressing method, HIP method or the like.

The surface-embedded portion 9 of the ceramic sintered substrate 6 thus produced has the same shape as the wiring circuit pattern. The CC ′ cross section of the ceramic sintered substrate 6 shown in FIG. 3 is shown in FIG. As shown in the figure, the depth t ₃ of the embedding portion 9 is set to 50 to 1000 μm, preferably 150 to 500 μm, in consideration of the resistance value of the conductor layer, heat dissipation and the like. The ceramic sintered substrate 6
The embedded portion 10 on the back surface is designed so that the heat dissipation of the metal layer 8 to be embedded is improved, and is formed almost all over the back surface. The embedded portion 10 is preferably formed on the entire back surface, but may be divided. The depth t ₄ of the embedded portion 10 is 50 to 1000 μm.
And it is preferable that the depth is deep. In the production of this ceramic sintered substrate 6, in order to reduce the cost and satisfy its heat dissipation, the depth t ₄ of the embedded portion 10 is set to 15
It is preferable to set it to 0 to 500 μm. The thickness t ₂ of the ceramic material between the back surface of the conductor layer 7 and the back surface of the metal layer 8 is set to 20 to 1000 μm in consideration of withstand voltage and heat dissipation, and preferably,
20 to 100 μm. The thickness t ₁ of the frame portion other than the embedded portions 9 and 10 of the ceramic sintered substrate 6 is preferably 0.5 to 2.0 mm in consideration of the strength of the ceramic sintered substrate 6.

The material of the ceramic sintered substrate 6 is alumina,
There are oxide ceramics such as zirconia, magnesia, zircon, beryllia, mullite and cordierite, nitride ceramics such as aluminum nitride, silicon nitride and titanium nitride, and carbide ceramics such as silicon carbide. These are used as a single substance. Alternatively, it may be used as a complex. Materials other than the above may be ceramics, glass, silicon single crystal, silicon polycrystal, etc. which are generally called.

The ceramic printed circuit board 5 is manufactured using the ceramic sintered substrate 6 produced by any one of the above methods. This ceramic wiring circuit board 5 is mainly composed of the following 3
Manufactured in any of the usual ways.

(Manufacturing method 1) Ag, Ag / Pd, Au,
A noble metal paste obtained by mixing a metal powder such as Pt or Pd with a glass frit, or a noble metal paste obtained by mixing any powder of alumina and silica with the noble metal paste is applied or filled. Alternatively, a base metal paste obtained by mixing metal powder such as Cu or Ni and any one of glass frit, alumina powder, silica powder and the like is applied or filled in the same manner as the noble metal paste.
The ceramic sintered substrate having the noble metal paste or base metal paste applied or filled in the embedded portion is fired at 800 to 1000 ° C. to form a metal layer bonded to the heat radiation fin. The above-mentioned coating or filling and firing operations may be repeated several times to form the metal layer as described above.

A conductor layer is formed on the surface-embedded portion of the ceramic sintered substrate in the same manner as in the above-described method for forming the metal layer to form a wiring circuit. The metal layer and the conductor layer are formed. If necessary, the front and back surfaces should be polished. The surface of the metal layer and the conductor layer is plated with Au or Ni for oxidation prevention to form a ceramic wiring circuit board.

Since this ceramic printed circuit board is manufactured as described above, the manufacturing cost is low and the resistance value of the conductive layer is very small. In addition, the accuracy of the wiring circuit pattern becomes very high. In this ceramic wiring circuit board, as shown in FIGS. 1 to 5, a conductor layer and a metal layer are embedded to reduce the back surface distance between them. Moreover, the ceramic wiring circuit board in which the insulating material between the respective back surfaces has good thermal conductivity has very good heat dissipation and high withstand voltage characteristics.

(Manufacturing Method 2) In this method, the prepared ceramic sintered substrate is used as a ceramic wiring circuit board by using a wet metallizing method. An alkali-dissolving salt such as NaOH or KOH, an inorganic acid such as phosphoric acid or hydrofluoric acid, or an etching agent containing an additive in the alkali-dissolving salt or the inorganic acid is used on the entire surface of the ceramic sintered substrate. And finely roughen. After that, it is thoroughly washed with water, neutralized and dried. Palladium is nucleated and activated on the neutralized and dried ceramic sintered substrate, and electroless plating of Ag, Au, Cu, Ni or the like is performed to form a conductor layer and a metal layer. In this way, a thin metal layer is formed on the entire surface of the ceramic sintered substrate, and then a plating resist is applied or printed except for the embedding portion and the chuck portion when performing electrolytic plating. Next, Au, Pt, Ag were embedded in the embedded parts on the front and back of this ceramic sintered substrate.
Etc., or electroless plating is performed until a noble metal such as Cu or Ni or a base metal such as Cu or Ni is embedded to form a conductor layer and a metal layer. The method of applying the electrolysis and electroless plating is a general method. After the completion of this electroplating, the plating resist is peeled off, and if necessary, the front and back surfaces are polished and surface-conditioned, and then quick etching is performed to remove the thin metal layer. Finally, the surfaces of the conductor layer and the metal layer are plated with Ni or Au to form a protective coat for preventing oxidation of the respective layers.

In this way, the ceramic wiring circuit board manufactured is
The ceramic sintered substrate has a large adhesion to the conductor layer and the metal layer, the wiring circuit pattern has high accuracy, and the cost is low. Moreover, the resistance value of the conductor layer is very small. Since the ceramic sintered substrate is used as an insulating material, this ceramic wiring circuit board has very good heat dissipation and high withstand voltage.

(Manufacturing Method 3) The front and back embedding portions of the ceramic sintered substrate are lightly sandblasted, and the front and back portions other than this embedding portion are masked with a metal plate. After that, metal is sprayed on the embedded portion. This metal spraying method uses a generally melted method. This metal is a noble metal such as Au, Pd, Pt, or Ag, a base metal such as Ni, Cu, Fe, or an alloy. After the front and back buried portions are filled with the metal, the ceramic sintered substrate is heated at a high temperature of 500 to 1000 ° C. and annealed. If necessary, the front surface and the back surface are surface-aligned, and the metal attached other than the wiring circuit pattern is removed by etching. After that, Ni or Au plating is applied to the surfaces of the conductor layer and the metal layer formed of this metal to form a protective coat for preventing oxidation of the respective layers.

The ceramic printed circuit board manufactured in this manner has a circuit formed of a low resistance conductor and has a high-precision wired circuit pattern as in the manufacturing methods 1 and 2. Furthermore, this ceramic printed circuit board is inexpensive, has good heat dissipation, and has high withstand voltage.

Next, Examples 1 to 3 of the ceramic wiring circuit board manufactured by using each of the conductor paste, the wet metallizing method and the metal spraying method will be described.

(Example 1) A ceramic wiring circuit manufactured using the conductor paste of the manufacturing method 1 will be described below.

Table 1 shows the manufacturing method of the ceramic sintered substrate, each dimension of the ceramic sintered substrate shown in FIG. 5 and its material, the kind of the conductor paste used for the conductor layer and the metal layer, and the firing atmosphere. And the firing atmosphere temperature.

Under the conditions shown in Table 1, a ceramic sintered substrate was prepared, a metal was embedded in the embedded portion, and then the front and back surfaces were polished and surface-polished. The surface of the conductor layer and the metal layer thus formed was subjected to electroless plating of Ni or Au to manufacture a ceramic wiring circuit board, and its characteristics were evaluated.

The evaluation method is shown below, and the evaluation results are shown in Table 1.

As can be seen from Table 1, the ceramic wiring circuit board according to the present invention sufficiently satisfies the required withstand voltage characteristics, has very good heat dissipation characteristics, and has high wiring circuit pattern accuracy.

(Example 2) A ceramic wiring circuit board manufactured by using the wet metallizing method (electroless plating, electrolytic plating) of the manufacturing method 2 is shown below.

Table 2 shows the manufacturing method of the ceramic sintered substrate, each dimension of the ceramic sintered substrate shown in FIG. 5 and its material, chemicals for treating the surfaces of the conductor layer and the metal layer, and the temperature thereof. showed that. As the surface treatment method with this chemical, a method of dipping this ceramic sintered substrate in the chemical or a method of coating the surface of the ceramic sintered substrate with a chemical was used.

As shown in Manufacturing Method 2, the whole surface of the ceramic sintered substrate was subjected to etching treatment to roughen it, and then was thoroughly washed with hot water and washed with water to be neutralized. After that, electroless plating was applied to the entire surface of this ceramic sintered substrate to impart conductivity. This ceramic sintered substrate was subjected to electrolytic plating by printing or applying a plating resist on other portions except for the portion (embedded portion) where metal deposition was required by electrolytic plating. Each type of electrolytic and electroless plating is second
Shown in the table. A metal was embedded in the embedded portions on the front and back surfaces of the ceramic sintered substrate, the plating resist was peeled off, and the front and back surfaces of this substrate were polished and conditioned. After that, the electroless plating of the underlayer was removed by quick etching. The etching liquid used in this quick etching is generally used. The metal portions exposed on the front and back surfaces of the ceramic sintered substrate were electrolessly plated with Ni or Au to form a protective coat for preventing oxidation and protecting the surface of the metal portion.

The thus-produced ceramic printed circuit board was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

As shown in Table 2, it was found that the ceramic wiring circuit board manufactured by the wet metallizing method described above had a required withstand voltage property, good heat dissipation and a highly accurate wiring circuit pattern.

(Example 3) A ceramic wiring circuit board manufactured by using the metal spraying method represented by the manufacturing method 3 will be described below.

Table 3 shows the method for manufacturing the ceramic sintered substrate, the respective dimensions of the ceramic sintered substrate shown in FIG. 5 and the materials thereof. Table 3 also shows the metal sprayed to fill the buried portion and the annealing temperature.

Ceramic sintered substrates were prepared under the conditions shown in Table 3, and the embedded portions formed on the front and back surfaces of this sintered substrate were sandblasted. Masking was performed so as to cover a portion other than the embedded portion of the substrate, and then metal was sprayed. After the embedded portion was filled with the metal in this way, the front and back surfaces of this substrate were polished and surfaced, and unnecessary metal adhering to the substrate was removed by etching. Electroless plating of Ni or Au was applied to the exposed metal parts on the front and back surfaces of the substrate to form a protective coat for oxidation prevention and surface protection of the metal parts.

The ceramic wiring circuit board manufactured in this manner was evaluated by the same method as the evaluation method shown in Example 1. The evaluation results are shown in Table 3.

As can be seen from Table 3, the ceramic wiring circuit board manufactured by using this metal spraying method satisfies the required withstand voltage characteristics, has good heat dissipation, and has a highly accurate wiring circuit pattern. I understood it.

〔The invention's effect〕

As has been seen above, the ceramic printed circuit board obtained by the manufacturing method according to the present invention is provided with the conductor layer forming the wiring circuit on the front surface of the ceramic substrate and the metal layer having a heat dissipation effect on the back surface. Since the conductor layer and the metal layer are provided so as to be embedded in the ceramic wiring circuit board, the heat dissipation is good while satisfying the required withstand voltage characteristics, and a wiring circuit with higher precision is provided. Have a pattern. In addition, it can be manufactured at a very low cost, and the resistance value of the wiring circuit is small.

[Brief description of drawings]

FIG. 1 (a) is a perspective view of the ceramic printed circuit board according to the present invention seen from the front surface, FIG. 1 (b) is a perspective view seen from the back surface, and FIG. 2 is BB 'shown in FIG. 1 (b). A sectional view, FIG. 3 is an exploded perspective view of a conductor layer and a ceramic sintered substrate which constitute the ceramic wiring circuit board, FIG. 4 is an exploded perspective view of a metal layer and a ceramic sintered substrate, and FIG. 5 is FIG. 6 is a perspective view of a conventional ceramic printed circuit board seen from the surface, and FIG. 6 (b) is a cross-sectional view of CC ′ shown in FIG.
Is a perspective view of a conventional ceramic printed circuit board seen from the back side,
FIG. 7 is a sectional view taken along the line AA 'shown in FIG. 6 (a). 1,5 …… Ceramic wiring circuit board, 2,6 …… Ceramic sintered substrate, 3,7 …… Conductor layer, 4,8 …… Metal layer, 9,10 …… Embedded part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoru Ogawa, 1048, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Works Co., Ltd. Inventor Kiyotaka Waki 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) Reference JP 58-4996 (JP, A) JP 55-141786 (JP, A) JP 50-127174 (JP, A)

Claims (3)

[Claims] 1. A method of manufacturing a ceramic wiring circuit board, comprising a conductor layer for forming a wiring circuit on a front surface of a ceramic substrate and a metal layer having a heat radiation effect on a back surface thereof.
For the ceramic substrate with concave parts formed on both sides in advance,
A method for manufacturing a ceramic printed circuit board, characterized in that a conductor layer for forming a wiring circuit is formed in the concave portion on one side, and a metal layer having a heat radiation effect is buried in the concave portion on the other side. 2. The embedding depth of the conductor layer and the metal layer is 50 to 50.
The method for manufacturing a ceramic printed circuit board according to claim 1, wherein the method is 1000 μm. 3. The thickness between the back surface of the conductor layer and the back surface of the metal layer is 20 to
The method for producing a ceramic printed circuit board according to claim 1 or 2, wherein the method is 1000 μm.