JP4299421B2 - Manufacturing method of ceramic circuit board - Google Patents

Description

[0001]
BACKGROUND 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 board with an active metal brazing material.
[0002]
[Prior art]
In recent years, as circuit boards such as power module boards and switching module boards, through an active metal brazing material in which at least one of titanium, zirconium, hafnium and hydrides thereof is added to a silver-copper alloy on a ceramic board. A ceramic circuit board in which a metal circuit board made of copper or the like is directly bonded is used.
[0003]
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. In the case of a sintered material, it is specifically manufactured by the following method.
[0004]
That is,
(1) First, an organic solvent and a solvent are added to and mixed with 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 paste.
(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, etc. to form a mud and this is a well-known doctor blade. After obtaining a plurality of ceramic green sheets by adopting a tape forming technique such as a method and a calender roll method, it is formed into a predetermined dimension, and then the ceramic green sheets are stacked up and down as necessary and in a reducing atmosphere. Firing is performed at a temperature of about 1600 ° C., and the ceramic green sheet is 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 paste interposed therebetween.
(4) Finally, the brazing 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 passed through the ceramic substrate. A ceramic circuit board is manufactured by joining a brazing material made of silver-copper alloy and joining the brazing material to a metal circuit board.
[0005]
In order to effectively prevent oxidative corrosion on the exposed surface of the brazing material and the metal circuit board, and at the same time, to strengthen the bonding with an adhesive material such as solder for bonding and fixing an electronic component such as a semiconductor element to the metal circuit board, A metal such as nickel is deposited by using a technique such as plating.
[0006]
[Problems to be solved by the invention]
However, in this conventional method of manufacturing a ceramic circuit board, the metal circuit board is bonded to the ceramic board after a metal circuit board having a predetermined pattern made of copper or the like is placed on the ceramic board with a brazing paste interposed therebetween. The brazing paste is heated at a temperature equal to or higher than the liquidus temperature in a reducing atmosphere. The metal paste has a drawback that the adjacent metal circuit boards are electrically short-circuited.
[0007]
Therefore, in order to eliminate the above-described drawbacks, it is conceivable to reduce the thickness of the brazing paste to, for example, less than 10 μm.
[0008]
However, if the thickness of the brazing material paste is reduced, when the metal circuit board is mounted on the ceramic substrate, the stress due to the difference in thermal expansion coefficient between the ceramic substrate and the metal circuit board is reduced. As a result, the material cannot absorb effectively, and as a result, the above-described stress induces a defect that the ceramic substrate is cracked or broken.
[0009]
The present invention has been devised in view of the above-mentioned drawbacks, and its purpose is to generate a metal circuit board on a ceramic substrate without causing an electrical short between adjacent metal circuit boards, and to generate cracks in the ceramic substrate. It is an object of the present invention to provide a method of manufacturing a ceramic circuit board that can be firmly bonded without being performed.
[0010]
[Means for Solving the Problems]
The method for producing a ceramic circuit board of the present invention comprises:
(1) An active metal brazing material comprising a silver powder, a copper powder and / or a silver-copper alloy powder, and an active metal powder comprising at least one of titanium, zirconium, hafnium and hydrides thereof; Producing a brazing paste containing an agglomerate formed by joining high melting point metal powder having a melting point of 1200 ° C. or higher by point joining;
(2) placing a metal circuit board on the ceramic substrate with the brazing paste interposed therebetween;
(3) A brazing paste disposed between the ceramic substrate and the metal circuit board is heated in a non-oxidizing atmosphere, and the ceramic substrate is made of a silver-copper alloy containing aggregates via active metal powder. Joining the brazing material and joining the brazing material to the metal circuit board;
It is characterized by comprising.
[0011]
The method for producing a ceramic circuit board according to the present invention is characterized in that the agglomerates are contained in an amount of 3 to 20% by weight based on the active metal brazing material.
[0012]
Furthermore, the method for producing a ceramic circuit board according to the present invention is characterized in that the aggregate has an average diameter of 10 to 100 μm.
[0013]
According to the method for producing a ceramic circuit board of the present invention, the metal circuit board is bonded to the ceramic substrate by an average diameter of 10 formed by bonding high melting point metal powder having a melting point of 1200 ° C. or higher on the ceramic substrate by spot bonding. A metal circuit board having a predetermined pattern made of copper or the like is placed with a brazing paste containing 3 to 20% by weight of agglomerates of 100 to 100 μm in the active metal brazing material, and then placed in a reducing atmosphere in a reducing atmosphere. Since it is performed by heating to a temperature of 900 ° C., even if the brazing paste is heated at a temperature equal to or higher than the liquidus temperature of the brazing material, the aggregate is formed between the ceramic substrate and the metal circuit board. The brazing material paste does not greatly melt and spread as a spacer, and as a result, the occurrence of an electrical short circuit between adjacent metal circuit boards is effectively prevented.
[0014]
At the same time, a space having a predetermined thickness is secured between the metal circuit board and the ceramic substrate by an agglomerate in which high melting point metal powder having a melting point of 1200 ° C. or higher is joined by spot bonding, and a predetermined amount of brazing material is placed in the space. Because of the interposition, the stress generated by the difference in thermal expansion coefficient 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 cracked.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings.
1 and 2 are cross-sectional views showing an embodiment of a wiring board produced 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.
[0016]
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, or a silicon nitride sintered body, and has a metal on its upper surface. A circuit board 3 is brazed via an active metal brazing material layer 2.
[0017]
The ceramic substrate 1 functions as a support member for supporting the metal circuit board 3 brazed to the upper surface thereof.
[0018]
The metal circuit board 3 brazed to the upper surface of the ceramic substrate 1 is made of a metal material such as copper and serves to supply electric signals and electric power to semiconductor elements and the like mounted on the ceramic circuit substrate.
[0019]
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 since the brazing material itself is active, it is directly attached on the ceramic substrate 1. .
[0020]
Thus, according to the above-described 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 through an adhesive such as solder, and the metal circuit board 3 is used as an external electric circuit. If connected, electronic components such as semiconductor elements are electrically connected to an external electric circuit through the metal circuit board 3.
[0021]
Next, a method for manufacturing the ceramic circuit board will be described.
(1) First, the ceramic substrate 1 is manufactured.
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, or a silicon nitride sintered body. In the case of a sintered material, an appropriate organic binder, plasticizer and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide to form a mud and the mud A ceramic green sheet (ceramic green sheet) is formed by adopting a well-known doctor blade method or calendar roll method. Thereafter, the ceramic green sheet is appropriately punched and laminated, and about 1600 are laminated. Manufactured by firing at a high temperature of ℃.
(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, by applying a conventionally known metal processing method such as a rolling method or a punching method to an ingot such as copper, a predetermined thickness of 500 μm is provided. Shaped into a pattern.
[0022]
When the metal circuit board 3 is formed of oxygen-free copper, the oxygen-free copper is not oxidized by the oxygen present in the copper during the brazing process, and the active metal brazing material And the bonding to the ceramic substrate 1 through the brazing material layer 2 becomes strong. Therefore, the metal circuit board 3 is preferably formed of oxygen-free copper.
(3) Next, an active metal brazing paste is produced.
The active metal brazing paste comprises a brazing powder composed of silver powder and copper powder and / or a silver-copper alloy powder, and an active metallic powder composed of at least one of titanium, zirconium, hafnium and hydrides thereof. 3-20% by weight of an aggregate 2a having an average diameter of 10 to 100 μm formed by joining high melting point metal powder having a melting point of 1200 ° C. or higher to the active metal brazing material by point joining, and adding an appropriate organic solvent and solvent And kneaded.
(4) Next, the active metal brazing paste is applied onto a predetermined pattern on the upper surface of the ceramic substrate 1 by using a conventionally known screen printing technique, for example, with a thickness of 30 to 50 μm and printed on the predetermined pattern. The metal circuit board 3 is placed on the applied active metal brazing paste.
[0023]
Finally, an active metal brazing paste disposed between the ceramic substrate 1 and the metal circuit board 3 is applied to a hydrogen gas atmosphere or hydrogen / nitrogen gas while applying a load of 50 to 100 g to the metal circuit board 3. In a non-oxidizing atmosphere of the atmosphere, it is heated to 900 ° C. to disperse the organic solvent or solvent of the active metal brazing material paste and melt the brazing material to form the upper surface of the ceramic substrate 1 and the lower surface of the metal circuit board 3. By joining, the metal circuit board is attached to the upper surface of the ceramic substrate 1. In this case, in the active metal brazing material paste, an aggregate 2a formed by joining high melting point metal powders having a melting point of 1200 ° C. or higher by point joining is added, so that the ceramic substrate 1 and the metal circuit board 3 A space having a predetermined thickness is ensured between the two, and the brazing material is not greatly melted and spread. As a result, the occurrence of an electrical short circuit between adjacent metal circuit boards is effectively prevented. At the same time, a space having a predetermined thickness is secured between the metal circuit board 3 and the ceramic substrate 1 by the aggregate 2a in which high melting point metal powder having a melting point of 1200 ° C. or more is bonded by spot bonding, and a predetermined amount of space is secured in the space Since the brazing material is interposed, the stress generated by the difference in the thermal expansion coefficient between the metal circuit board 3 and the ceramic substrate 1 is absorbed by the brazing material, and the ceramic substrate 1 is not cracked or cracked.
[0024]
The brazing material powder made of the active metal brazing material silver powder and the copper powder and / or the silver-copper alloy powder serves to join the ceramic substrate 1 and the metal circuit board 3, for example, from eutectic alloy. In this case, it is formed of a eutectic alloy containing 72% by weight and 28% by weight of silver and copper, respectively.
[0025]
Further, when the particle size of the brazing material powder is less than 1 μm, the specific surface area of the brazing material powder is increased, and a large amount of oxygen is present in the oxide film formed on the surface of the brazing material powder. There is a risk that the wettability of the ceramic substrate 1 and the metal circuit board 3 will be reduced, and the bonding strength between the ceramic substrate 1 and the metal circuit board 3 will be reduced. Accordingly, the particle size of the brazing material powder is preferably 1 μm or more.
[0026]
Further, the active metal powder made of at least one of titanium, zirconium, hafnium and hydrides thereof has a function of firmly bonding the brazing material to the ceramic substrate 1, and when the active metal powder is less than 2% by weight, If the absolute amount is insufficient, there is a risk that the brazing material cannot be firmly bonded to the ceramic substrate 1, and if it exceeds 5% by weight, a fragile reaction layer is formed between the active metal and the ceramic substrate 1. As a result, there is a risk that the adhesive strength between the brazing material and the ceramic substrate 1 is lowered. Therefore, the amount of the active metal added is preferably in the range of 2 to 5% by weight.
[0027]
Furthermore, the agglomerate 2a is formed of a powder of a refractory metal having a melting point of 1200 ° C. or higher, such as tungsten, molybdenum, manganese, etc. For example, if the refractory metal powder is molybdenum, about It is manufactured by heating to a temperature of 2000 ° C. and holding it for about 5 minutes to join the powders together by point joining, then gradually cooling to room temperature and classifying them to a predetermined diameter.
[0028]
Since the refractory metal has a melting point of 1200 ° C., which is sufficiently higher than the liquidus temperature of the brazing material, the agglomerate 2a melts even when the brazing material is heated to a temperature higher than the liquidus temperature. In addition, a spacer having a predetermined thickness can be reliably ensured between the ceramic substrate 1 and the metal circuit board 3.
[0029]
If the diameter of the agglomerate 2a is less than 10 μm, it becomes difficult to secure a space of a predetermined thickness between the ceramic substrate 1 and the metal circuit board 3, and if it exceeds 100 μm, the active metal brazing paste is applied to the ceramic substrate. When printing and coating on the upper surface of the upper surface using a conventionally known printing technique such as a screen printing method, it is difficult for the aggregate 2a to be caught by a mesh of the screen and to be printed and coated in a predetermined pattern. Therefore, the diameter of the aggregate 2a is preferably in the range of 10 to 100 μm, more preferably in the range of 20 to 50 μm.
[0030]
Furthermore, when the diameter of the refractory metal powder such as tungsten, molybdenum, manganese, etc. forming the aggregate 2a is less than 1 μm, the specific surface area increases, and many oxide films are formed on the surface of the refractory metal powder. There is a risk that oxygen is present, and the wettability of the active metal brazing material to the ceramic substrate 1 and the metal circuit board 3 is reduced by the oxygen, and the bonding strength between the ceramic substrate 1 and the metal circuit board 3 is reduced. If the thickness exceeds 6 μm, the number of joints between the refractory metal powders is small and the mechanical strength of the agglomerate 2a becomes weak. When the metal circuit board 3 is brazed to the ceramic substrate 1, the refractory metal of the agglomerate 2a It is difficult to ensure a space with a predetermined thickness between the ceramic substrate 1 and the metal circuit board 3 due to scattering between the powders. Therefore, it is preferable that each refractory metal powder forming the aggregate 2a has a diameter in the range of 1 to 6 μm.
[0031]
Furthermore, when the amount of the aggregate 2a added to the brazing material is less than 3% by weight, it becomes difficult to secure a space having a predetermined thickness between the ceramic substrate 1 and the metal circuit board 3, and 20% by weight. If it exceeds%, 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 amount of the aggregate 2a added to the brazing material is preferably in the range of 3 to 20% by weight.
[0032]
It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiments, the ceramic substrate 1 is made of an aluminum-based ceramic. In the example shown in the figure, the electronic component generates a large amount of heat, and when it is desired to efficiently remove this heat, the ceramic substrate 1 is made of an aluminum nitride sintered body or silicon nitride having high thermal conductivity. The ceramic substrate 1 may be formed of a mullite sintered body having a low dielectric constant when the electric signal is to be propagated through the metal circuit board 3 at a high speed.
[0033]
Further, if a metal made of nickel and having good conductivity, corrosion resistance and good wettability with the brazing material is deposited on the surface of the metal circuit board 3 by a plating method, the metal circuit board 3 and the external electric circuit 3 The electrical connection with the circuit is good, and electronic components such as semiconductor elements can be firmly bonded to the metal circuit board 3.
[0034]
Further, if the nickel plating layer is an amorphous alloy of nickel-phosphorus containing 8 to 15% by weight of phosphorus, the surface oxidation of the nickel layer can be prevented well, and the phosphorus (P ) Is less than 8% by weight, the nickel plating layer has a nickel-phosphorus polycrystal structure which is easily oxidized, and the electronic components such as semiconductor elements are firmly and electrically connected to the metal circuit board 3 via an adhesive such as solder. When the nickel plating layer is formed when the nickel plating layer is formed, it is impossible to form a nickel-phosphorus amorphous alloy by precipitating phosphorus alone or preferentially. 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.
[0035]
Furthermore, if the thickness of the nickel plating layer deposited on the surface of the metal circuit board 3 is less than 1.5 μm, the surface of the metal circuit board 3 cannot be completely covered with the nickel plating layer, The oxidative corrosion of the metal circuit board 3 cannot be effectively prevented, and if it exceeds 3 μm, the internal stress inside the nickel plating layer becomes large, and the ceramic substrate 1 is warped or cracked. In particular, when the thickness of the ceramic substrate 1 is as thin as 700 μm or less, warping or cracking of the ceramic substrate 1 becomes remarkable. Therefore, the nickel plating layer deposited on the surface of the metal circuit board 3 preferably has a thickness in the range of 1.5 μm to 3 μm.
[0036]
【The invention's effect】
According to the method for producing a ceramic circuit board of the present invention, the metal circuit board is bonded to the ceramic substrate by an average diameter of 10 formed by bonding high melting point metal powder having a melting point of 1200 ° C. or higher on the ceramic substrate by spot bonding. A metal circuit board having a predetermined pattern made of copper or the like is placed with a brazing paste containing 3 to 20% by weight of agglomerates of 100 to 100 μm in the active metal brazing material, and then placed in a reducing atmosphere in a reducing atmosphere. Since it is performed by heating to a temperature of 900 ° C., even if the brazing paste is heated at a temperature equal to or higher than the liquidus temperature of the brazing material, the aggregate is formed between the ceramic substrate and the metal circuit board. The brazing material paste does not greatly melt and spread as a spacer, and as a result, the occurrence of an electrical short circuit between adjacent metal circuit boards is effectively prevented.
[0037]
At the same time, a space having a predetermined thickness is secured between the metal circuit board and the ceramic substrate by an agglomerate in which high melting point metal powder having a melting point of 1200 ° C. or higher is joined by spot bonding, and a predetermined amount of brazing material is placed in the space. Because of the interposition, the stress generated by the difference in thermal expansion coefficient 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 cracked.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a ceramic circuit board manufactured by the manufacturing method of the present invention.
FIG. 2 is an enlarged cross-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)

(1) An active metal brazing material comprising a silver powder, a copper powder and / or a silver-copper alloy powder, and an active metal powder comprising at least one of titanium, zirconium, hafnium and hydrides thereof; Producing a brazing paste containing an agglomerate formed by joining high melting point metal powder having a melting point of 1200 ° C. or higher by point joining;
(2) placing a metal circuit board on the ceramic substrate with the brazing paste interposed therebetween;
(3) A brazing paste disposed between the ceramic substrate and the metal circuit board is heated in a non-oxidizing atmosphere, and the ceramic substrate is made of a silver-copper alloy containing aggregates via active metal powder. Joining the brazing material and joining the brazing material to the metal circuit board;
A method of manufacturing a ceramic circuit board comprising: 2. The method of manufacturing a ceramic circuit board according to claim 1, wherein the aggregate is contained in an amount of 3 to 20% by weight based on the active metal brazing material. 2. The method of manufacturing a ceramic circuit board according to claim 1, wherein the aggregate has an average diameter of 10 to 100 [mu] m.

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