JP2001148568A - Manufacturing method of ceramic circuit board - Google Patents

Abstract

(57) Abstract: A brazing material for brazing a metal circuit board to a ceramic substrate melts and spreads, causing an electrical short circuit between adjacent metal circuit boards. An active metal brazing material comprising a brazing material powder comprising silver powder, copper powder and / or silver-copper alloy powder, and an active metal powder comprising at least one of titanium, zirconium, hafnium and hydrides thereof. And a solder paste containing an agglomerate 2a formed by joining a high melting point metal powder having a melting point of 1200 ° C. or more by point joining, to produce a metal circuit board on a ceramic substrate 1 using the active metal brazing material. 3 is brazed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic circuit board in which a metal circuit board is joined to a ceramic substrate by an active metal brazing material.

[0002]

2. Description of the Related Art In recent years, as a circuit substrate such as a power module substrate or a switching module substrate, an active metal obtained by adding at least one of titanium, zirconium, hafnium and a hydride thereof to a silver-copper alloy on a ceramic substrate. A ceramic circuit board is used in which a metal circuit board made of copper or the like is directly joined via a brazing material.

Such a ceramic circuit board is generally made of an electrically insulating ceramic material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a silicon nitride sintered body, and a mullite sintered body. When it is made of an aluminum oxide sintered body, it is specifically manufactured by the following method.

[0004] (1) First, an organic solvent and a solvent are added to an active metal powder obtained by adding at least one of titanium, zirconium, hafnium and a hydride thereof to a silver-copper alloy to prepare a brazing material paste. I do. (2) Next, a ceramic raw material powder such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide is mixed with an appropriate organic binder, plasticizer, solvent and the like to form a slurry, which is then formed into a well-known doctor blade. After obtaining a plurality of ceramic green sheets by employing a tape forming technique such as a method or a calendar roll method, forming a predetermined size, and then laminating the ceramic green sheets up and down as necessary, and in a reducing atmosphere, About 1600 ° C
And the ceramic green sheets are sintered and integrated to form a ceramic substrate made of an aluminum oxide sintered body. (3) Next, a metal circuit board made of copper or the like is placed on the ceramic substrate with the brazing material paste interposed therebetween. (4) Finally, the brazing material paste disposed between the ceramic substrate and the metal circuit board is heated to a temperature of about 900 ° C. in a non-oxidizing atmosphere, and the active metal powder is applied to the ceramic substrate via the active metal powder. A ceramic circuit board is manufactured by joining a brazing material made of a silver-copper alloy and joining the brazing material to a metal circuit board.

Incidentally, the brazing material and the exposed surface of the metal circuit board are effectively prevented from being oxidized and corroded and, at the same time, are firmly bonded to an adhesive such as solder for bonding and fixing electronic components such as semiconductor elements to the metal circuit board. For this purpose, a metal such as nickel is applied by using a technique such as a plating method.

[0006]

However, in this conventional method of manufacturing a ceramic circuit board, the joining of the metal circuit board to the ceramic substrate is performed by forming a predetermined pattern made of copper or the like with a brazing material paste interposed on the ceramic substrate. After placing the metal circuit board, place it in a reducing atmosphere for about 900
° C, and since the brazing material paste is heated at a temperature equal to or higher than the liquidus temperature, it is greatly melted and spread. Had the drawback of being electrically short-circuited.

Therefore, it is conceivable to reduce the thickness of the brazing material paste to, for example, less than 10 μm in order to solve the above-mentioned disadvantage.

However, when the thickness of the brazing material paste is reduced, when the metal circuit board is mounted on the ceramic substrate, a stress generated between the ceramic substrate and the metal circuit board due to a difference in thermal expansion coefficient between the two. Cannot be effectively absorbed by the brazing material. As a result, cracks and cracks are generated in the ceramic substrate due to the stress.

The present invention has been devised in view of the above-mentioned drawbacks, and has as its object to form a metal circuit board on a ceramic substrate without causing an electrical short between adjacent metal circuit boards and breaking the metal circuit board. It is an object of the present invention to provide a method for manufacturing a ceramic circuit board which can be firmly bonded without generating any problem.

[0010]

The method of manufacturing a ceramic circuit board according to the present invention comprises: (1) a brazing filler metal powder comprising silver powder, copper powder and / or silver-copper alloy powder, titanium, zirconium, hafnium and the like. Of an active metal brazing material comprising an active metal powder comprising at least one of the following hydrides, and an agglomerate obtained by joining points of a high melting point metal powder having a melting point of 1200 ° C. or more by point joining. (2) placing a metal circuit board on the ceramic substrate with the brazing material paste interposed therebetween;
(3) A brazing material paste disposed between the ceramic substrate and the metal circuit board is heated in a non-oxidizing atmosphere, and a silver-copper alloy containing an aggregate is formed on the ceramic substrate via an active metal powder. And joining the brazing material to the metal circuit board.

Further, in the method of manufacturing a ceramic circuit board according to the present invention, the aggregate is preferably 3 to 2 with respect to the active metal brazing material.
It is characterized by containing 0% by weight.

Further, in the method for manufacturing a ceramic circuit board according to the present invention, the aggregate has an average diameter of 10 to 100 μm.

According to the method for manufacturing a ceramic circuit board of the present invention, the bonding of the metal circuit board to the ceramic substrate is performed by bonding a high melting point metal powder having a melting point of 1200 ° C. or more on the ceramic substrate by point bonding. A metal circuit board having a predetermined pattern made of copper or the like is placed with a brazing material paste containing 3 to 20% by weight of an agglomerate having a diameter of 10 to 100 μm based on the active metal brazing material, and then placed in a reducing atmosphere. Medium, since the heating is performed by heating to a temperature of about 900 ° C., even if the brazing material paste is heated at a temperature equal to or higher than the liquidus temperature of the brazing material, the agglomerate forms a ceramic substrate and a metal circuit board. The solder paste does not greatly melt and spread as a spacer between the metal plates, and as a result, an electrical short circuit between adjacent metal circuit boards is effectively prevented from occurring.

At the same time, a space having a predetermined thickness is secured between the metal circuit board and the ceramic substrate by an aggregate obtained by joining high melting point metal powders having a melting point of 1200 ° C. or higher by point bonding. Since the brazing material is interposed, the stress generated due to the difference in the coefficient of thermal expansion between the metal circuit board and the ceramic substrate is absorbed by the brazing material, and it is possible to effectively prevent the ceramic substrate from being cracked or broken. .

[0015]

Next, the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 are cross-sectional views showing one embodiment of a wiring board manufactured by the manufacturing method of the present invention, wherein 1 is a ceramic substrate, 2 is a brazing material layer, and 3 is a metal circuit board.

The ceramic substrate 1 is made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, an aluminum nitride sintered body, and a silicon nitride sintered body. On the upper surface, a metal circuit board 3 is brazed via an active metal brazing material layer 2.

The ceramic substrate 1 functions as a supporting member for supporting the metal circuit board 3 brazed on the upper surface thereof.

The metal circuit board 3 brazed to the upper surface of the ceramic substrate 1 is made of a metal material such as copper.
It functions to supply electric signals and electric power to semiconductor elements and the like mounted on the ceramic circuit board.

Further, the brazing material for brazing the metal circuit board 3 to the upper surface of the ceramic substrate 1 is made of an active metal brazing material, and is directly attached onto the ceramic substrate 1 because the brazing material itself has activity. Will be.

Thus, according to the above-mentioned ceramic circuit board, electronic components such as semiconductor elements are electrically connected to the metal circuit board 3 on the upper surface of the ceramic substrate 1 via an adhesive such as solder, and the metal circuit board 3 is externally connected. When connected to an electric circuit, electronic components such as semiconductor elements are electrically connected to an external electric circuit via the metal circuit board 3.

Next, a method of manufacturing the above ceramic circuit board will be described. (1) First, the ceramic substrate 1 is manufactured. The ceramic substrate 1 is made of an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, an aluminum nitride sintered body,
It is made of an electrically insulating material such as a silicon nitride sintered body, for example,
When it is made of an aluminum oxide-based sintered body, an appropriate organic binder, a plasticizer, and a solvent are added to raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to form a slurry, and the slurry is formed. A ceramic green sheet (ceramic green sheet) is formed by employing a conventionally known doctor blade method or calender roll method, and thereafter, the ceramic green sheet is subjected to an appropriate punching process and a plurality of the ceramic green sheets are laminated. It is manufactured by firing at a high temperature of about 1600 ° C. (2) Next, the metal circuit board 3 is manufactured. The metal circuit board 3 is made of a metal material such as copper. For example, a predetermined well-known metal processing method such as a rolling method or a punching method is applied to an ingot (lumps) of copper or the like to obtain a predetermined thickness of 500 μm. Shaped into a pattern.

When the metal circuit board 3 is formed of oxygen-free copper, the oxygen-free copper is activated without the surface of copper being oxidized by the oxygen existing in the copper during brazing. The wettability with the metal brazing material is improved, and the ceramic substrate 1
Bonding through the brazing material layer 2 is strengthened. Therefore,
It is preferable that the metal circuit board 3 is formed of oxygen-free copper. (3) Next, an active metal brazing material paste is manufactured. The active metal brazing material paste comprises a brazing material powder composed of silver powder, copper powder and / or silver-copper alloy powder, and an active metal powder composed of at least one of titanium, zirconium, hafnium and hydrides thereof. 3-20% by weight of agglomerates 2a having an average diameter of 10-100 μm, which are obtained by joining high melting point metal powders having a melting point of 1200 ° C. or more by spot joining to an active metal brazing material, and an appropriate organic solvent and solvent are added and mixed. It is manufactured by kneading. (4) Next, the active metal brazing material paste is applied to a predetermined pattern with a thickness of, for example, 30 to 50 μm on the upper surface of the ceramic substrate 1 using a well-known screen printing technique, and is printed on the predetermined pattern. The metal circuit board 3 is placed on the applied active metal brazing material paste.

Finally, the active metal brazing material paste disposed between the ceramic substrate 1 and the metal circuit board 3 is applied to the metal circuit board 3 while applying a load of 50 to 100 g to a hydrogen gas atmosphere or a hydrogen gas atmosphere. Heating to 900 ° C. in a non-oxidizing atmosphere of a nitrogen gas atmosphere to diffuse the organic solvent and the solvent of the active metal brazing material paste and to melt the brazing material, so that the upper surface of the ceramic substrate 1 and the metal circuit board 3
By bonding to the lower surface of the ceramic substrate 1
A metal circuit board will be attached to the upper surface of. In this case, the active metal brazing material paste has a melting point of 1200.
Since agglomerates 2a formed by joining metal powders having a high melting point of not less than ° C. by point joining are added, a space of a predetermined thickness is secured between the ceramic substrate 1 and the metal circuit board 3, so that the brazing material is largely melted. It does not spread, thereby effectively preventing an electrical short circuit between adjacent metal circuit boards. At the same time, a space of a predetermined thickness is secured between the metal circuit board 3 and the ceramic substrate 1 by the agglomerate 2a in which high melting point metal powders having a melting point of 1200 ° C. or more are joined by point bonding. Since the brazing material is interposed, the stress generated due to the difference in the thermal expansion coefficient between the metal circuit board 3 and the ceramic substrate 1 is absorbed by the brazing material, so that cracks and cracks do not occur in the ceramic substrate 1.

The active metal brazing filler metal powder composed of silver powder and copper powder and / or silver-copper alloy powder serves to join the ceramic substrate 1 and the metal circuit board 3. In the case of a eutectic alloy, it is formed of a eutectic alloy containing 72% by weight and 28% by weight of silver and copper, respectively.

When the particle size of the brazing material powder is less than 1 μm, the specific surface area of the brazing material powder increases, so that a large amount of oxygen is present in an oxide film formed on the surface of the brazing material powder,
Due to the oxygen, the wettability of the active metal brazing material to the ceramic substrate 1 and the metal circuit board 3 is reduced, and there is a risk that the bonding strength between the ceramic substrate 1 and the metal circuit board 3 is reduced. Accordingly, the brazing powder has a particle size of 1 μm.
It is preferable to set m or more.

Further, the active metal powder comprising at least one of titanium, zirconium, hafnium and hydrides thereof has an effect of firmly bonding the brazing material to the ceramic substrate 1, and when the active metal powder is less than 2% by weight. There is a danger that the brazing material cannot be firmly bonded to the ceramic substrate 1 due to an insufficient amount of the active metal, and a fragile reaction layer between the active metal and the ceramic substrate 1 exceeds 5% by weight. Is formed thick, and as a result, there is a risk that the adhesive strength between the brazing material and the ceramic substrate 1 is reduced. Therefore, the addition amount of the active metal is 2 to 5% by weight.
It is preferable to keep the range.

Further, the agglomerate 2a is made of a powder of a high melting point metal such as tungsten, molybdenum, manganese or the like having a melting point of 1200 ° C. or more. For example, if the high melting point metal powder is molybdenum, a reducing atmosphere is used. By heating to a temperature of about 2000 ° C. and holding the powder for about 5 minutes, the powders are joined by point joining, and then gradually cooled to room temperature.
It is manufactured by classifying to a predetermined diameter.

Since the high melting point metal has a melting point of 1200 ° C., which is sufficiently higher than the liquidus temperature of the brazing material, even when the brazing material is heated to a temperature higher than the liquidus temperature, the aggregates 2a remain A spacer having a predetermined thickness can be reliably secured between the ceramic substrate 1 and the metal circuit board 3 without melting.

If the diameter of the agglomerate 2a is less than 10 μm, it is difficult to secure a space of a predetermined thickness between the ceramic substrate 1 and the metal circuit board 3.
When the thickness exceeds 0 μm, when the active metal brazing material paste is printed and applied on the upper surface of the ceramic substrate 1 by using a printing technique such as a conventionally known screen printing method, the aggregates 2a are caught by a mesh of the screen and printed and applied in a predetermined pattern. It becomes difficult. Accordingly, the aggregate 2a has a diameter of 10
To 100 μm, more preferably 20 to 50 μm.
It is preferable to set it in the range of m.

Further, when the diameter of the high melting point metal powder such as tungsten, molybdenum, manganese or the like forming the aggregate 2a is less than 1 μm, the specific surface area increases, and the oxide film formed on the surface of the high melting point metal powder is reduced. And the oxygen reduces the wettability of the active metal brazing material to the ceramic substrate 1 and the metal circuit board 3, and reduces the bonding strength between the ceramic substrate 1 and the metal circuit board 3. There is a danger, and if it exceeds 6 μm, the number of bonding points between the high melting point metal powders is small, so that the mechanical strength of the aggregate 2a becomes weak, and when the metal circuit board 3 is brazed to the ceramic substrate 1, the aggregate 2a Variations occur between the high melting point metal powders, and it becomes difficult to secure a space of a predetermined thickness between the ceramic substrate 1 and the metal circuit board 3. Therefore, it is preferable that each high melting point metal powder forming the aggregate 2a has a diameter of 1 to 6 μm.

Further, if the amount of the aggregate 2a added to the brazing material is less than 3% by weight, it becomes difficult to secure a space of a predetermined thickness between the ceramic substrate 1 and the metal circuit board 3, On the other hand, if the content exceeds 20% by weight, the bonding area of the brazing material to the ceramic substrate 1 and the metal circuit board 3 becomes narrow, and the brazing strength of the metal circuit board 3 to the ceramic substrate 1 tends to decrease. Therefore, the aggregate 2
The amount of a added to the brazing material is preferably in the range of 3 to 20% by weight.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Although an example in which the electronic component generates a large amount of heat and an efficient removal of this heat is described, the ceramic substrate 1 may be formed of an aluminum nitride sintered body having a high thermal conductivity or an aluminum nitride sintered body. The ceramic substrate 1 may be formed of a mullite sintered body having a low dielectric constant when an electric signal is to be propagated to the metal circuit board 3 at high speed.

When a metal made of nickel and having good conductivity, good corrosion resistance and good wettability with the brazing material is applied to the surface of the metal circuit board 3 by plating, the metal circuit board 3 Good electrical connection between the metal circuit board 3 and an external electric circuit, and electronic components such as semiconductor elements can be firmly adhered to the metal circuit board 3.

Further, the nickel plating layer contains 8 to 15 phosphorus.
If the nickel-phosphorus amorphous alloy is contained in the nickel plating layer, the surface oxidation of the nickel layer can be prevented well, and the phosphorous (P) contained in the nickel plating layer becomes 8%.
When the content is less than 5% by weight, the nickel plating layer has a polycrystalline structure of nickel-phosphorus which is easily oxidized, and electronic components such as semiconductor elements are firmly and electrically connected to the metal circuit board 3 through an adhesive such as solder. If the content exceeds 15% by weight, when forming a nickel plating layer, phosphorus is deposited alone and preferentially, making it impossible to form a nickel-phosphorus amorphous alloy. Therefore, the amount of phosphorus contained in the nickel plating layer is specified in the range of 8 to 15% by weight, and preferably in the range of 10 to 15% by weight.

Further, when the thickness of the nickel plating layer applied to the surface of the metal circuit board 3 is less than 1.5 μm, the surface of the metal circuit board 3 can be completely covered with the nickel plating layer. It is impossible to effectively prevent the metal circuit board 3 from being oxidized and corroded. If the thickness exceeds 3 μm, the internal stress inside the nickel plating layer becomes large and the ceramic substrate 1 may be warped or cracked. Would. In particular, when the thickness of the ceramic substrate 1 is as thin as 700 μm or less, warpage or cracking of the ceramic substrate 1 becomes remarkable. Therefore, it is preferable that the thickness of the nickel plating layer applied to the surface of the metal circuit board 3 be in the range of 1.5 μm to 3 μm.

[0036]

According to the method for manufacturing a ceramic circuit board of the present invention, a metal circuit board is bonded to a ceramic substrate by point bonding of a high melting point metal powder having a melting point of 1200 ° C. or more on the ceramic substrate. Has an average diameter of 10 to 100 μm
After placing a metal circuit board of a predetermined pattern made of copper or the like with a brazing material paste containing 3 to 20% by weight of the aggregate of the active metal brazing material with respect to the active metal brazing material, this is placed in a reducing atmosphere.
Since it is performed by heating to a temperature of about 900 ° C., even if the brazing material paste is heated at a temperature equal to or higher than the liquidus temperature of the brazing material, the agglomerates remain between the ceramic substrate and the metal circuit board. Thus, the brazing material paste does not melt and spread widely by acting as a spacer, thereby effectively preventing an electrical short circuit between adjacent metal circuit boards.

At the same time, a space having a predetermined thickness is secured between the metal circuit board and the ceramic substrate by the aggregate obtained by joining the high melting point metal powder having a melting point of 1200 ° C. or more by point bonding. Since the brazing material is interposed, the stress generated due to the difference in the coefficient of thermal expansion between the metal circuit board and the ceramic substrate is absorbed by the brazing material, and it is possible to effectively prevent the ceramic substrate from being cracked or broken. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a ceramic circuit board manufactured by a manufacturing method of the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 2 ... Brazing material layer 2a ... Aggregate 3 ... Metal circuit board

Claims (3)

[Claims] (1) Silver powder and copper powder and / or silver
A brazing filler metal powder comprising a copper alloy powder and at least one of titanium, zirconium, hafnium and hydrides thereof;
An active metal brazing material comprising an active metal powder comprising a seed;
A step of producing a brazing material paste containing an agglomerate obtained by joining point melting points of a high melting point metal powder having a melting point of 1200 ° C. or more; and (2) forming a metal on a ceramic substrate with the brazing material paste interposed therebetween. (3) heating the brazing material paste disposed between the ceramic substrate and the metal circuit board in a non-oxidizing atmosphere, and setting the ceramic board on the ceramic substrate via active metal powder; Joining a brazing material made of a silver-copper alloy containing an aggregate and joining the brazing material to a metal circuit board. 2. The method according to claim 1, wherein the agglomerates are contained in an amount of 3 to 20% by weight based on the active metal brazing material.
3. The method for manufacturing a ceramic circuit board according to item 1. 3. An aggregate having an average diameter of 10 to 100 μm.
2. The method for manufacturing a ceramic circuit board according to claim 1, wherein the average diameter of the ceramic circuit board is the average diameter of the ceramic circuit board.