JP2003068966A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integral ceramic circuit board with built-in terminals which is capable of ensuring bending accuracy for the built-in terminals, precisely aligning the built-in terminals with the sockets or the like of a resin case when the integral ceramic circuit board is mounted in the resin case, and resultantly making an electronic part such as a semiconductor device mounted on it operate stably. SOLUTION: A metal circuit plate 2 formed of oxygen-free copper is joined to the surface of a ceramic board 1 through the intermediary of an active metal brazing material 4, the metal circuit plate 2 is partially extended and bent almost at a right angle with respect to the ceramic board 1 to serve as terminals 3 for the formation of a ceramic circuit board. A cutout 5 is provided to each side of the folded part of the terminal 3, and the total depth of the cutout 5 provided to the folded part amounts to 20 to 50% of the width of the terminal 3. The terminal 3 can be precisely bent at a desired position at which the cutout 5 is provided.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal-equipped ceramic circuit board in which a part of a metal circuit board is extended as a terminal. In recent years, as a circuit board such as a power module board or a switching module board, a ceramic substrate in which a metal circuit board made of copper or the like is directly bonded on a ceramic substrate via an active metal brazing material. Is used. [0003] Such a ceramic substrate with a metal circuit board is
When a ceramic substrate made of an aluminum oxide sintered body is used, it is specifically manufactured by the following method. First, a brazing material paste is prepared by adding an organic solvent and a solvent to an active metal powder obtained by adding at least one of titanium, zirconium, hafnium and a hydride thereof to a silver-copper alloy. Next, an appropriate organic binder, a plasticizer, a solvent and the like are added to raw material powders such as aluminum oxide, silicon oxide, magnesium oxide and calcium oxide to form a slurry, which is then formed into a slurry by a well-known doctor blade method. After obtaining a plurality of ceramic green sheets by adopting tape forming technology such as or calender roll method, it is formed to predetermined dimensions,
Next, the ceramic green sheets are laminated one above the other as necessary and fired at a temperature of about 1600 ° C. in a reducing atmosphere, and the ceramic green sheets are sintered and integrated to form a ceramic substrate made of an aluminum oxide sintered body. Form. Next, a metal circuit board made of copper or the like is placed on a ceramic substrate with a brazing material paste interposed therebetween. Finally, the brazing material paste disposed between the ceramic substrate and the metal circuit board is heated and melted at a temperature of about 900 ° C. in a non-oxidizing atmosphere. And a metal circuit board. The ceramic circuit board manufactured in this manner is an IGBT (Insulated Gate Bipolar Transistor).
And MOS-FET (Metal Oxide Semiconductor-Field
After electronic components such as a semiconductor element such as an effect transistor are mounted via an adhesive such as solder, terminals for external input / output are assembled in a resin case integrally molded to form a semiconductor module. The semiconductor module is used in a wide range of applications from industrial equipment such as robots to driving units for trains and electric vehicles, and is required to have high reliability under severe environments. However, the production of the terminal-integrated molded resin case requires a molding die, and the production cost is high. Therefore, the production cost of the semiconductor module is disadvantageously increased. Further, after assembling the ceramic circuit board in the terminal-integrated resin case, it is necessary to electrically connect the terminal portion and the ceramic circuit board with a bonding wire or the like. Therefore, a ceramic circuit board in which terminals are directly bonded to a metal circuit board by soldering or ultrasonic bonding, or a terminal-integrated ceramic circuit board in which a part of a metal portion of a circuit pattern is extended as a terminal. It is being adopted. However, when the terminals are joined to the metal circuit board using solder, the melting point is higher than the heating temperature so that the joining does not come off due to the subsequent heating temperature when mounting electronic components such as semiconductor elements. Due to the need for high-temperature solder, a thermal cycle caused by heating to a high temperature at this time may cause cracks due to the difference in thermal expansion between the metal circuit board and the ceramic substrate, or an epoxy type that has a heat resistance of only about 250 ° C However, there is a problem that the solder resist cannot be used. In addition, heat generated when a semiconductor element is mounted and used as a semiconductor module
Due to the vibration, cracks are easily generated inside the solder, and the reliability may be deteriorated. Also, in the terminal bonding by ultrasonic bonding, for example, since the ultrasonic oscillation horn is pressed with a pressure of about 10 to 50 MPa on the surface of the terminal bonding portion brought into contact with the metal circuit board, this high pressure is partially It is applied to the ceramic substrate immediately below the terminal joining portion via the metal circuit board and the joining brazing material. In addition, heat of about 500 ° C or more generated by ultrasonic vibration may momentarily cause minute partial cracks in the ceramic substrate immediately below the terminal joint, and as a result, the mechanical strength of the ceramic circuit board is reduced. There has been a problem that the reliability may be significantly deteriorated due to the decrease. For this reason, a terminal-integrated ceramic circuit board having a simpler structure, a reduced number of mounting steps, and a high reliability, in which a part of a metal circuit board is extended as a terminal portion, has been used. . In this case, electronic components such as semiconductor elements are mounted on a metal circuit board, connected to the metal circuit board with aluminum wires, and then the terminals are bent substantially perpendicularly to the ceramic circuit board and mounted on a resin case. The semiconductor module is completed. [0013] However, the conventional terminal-integrated ceramic circuit board has a thickness so that a large current can flow through the terminal portion, which is formed by extending a part of the metal circuit board. The problem is that it is difficult to bend accurately at a desired position when bending the terminal portion substantially perpendicularly to the ceramic substrate for mounting on a resin case because the terminal portion is formed of a thick and wide copper plate. there were. for that reason,
When mounting the terminal-integrated ceramic circuit board on the resin case, the terminal part and the socket to which the terminal part of the resin case is joined by fitting are not aligned, and the terminal part cannot be connected to a predetermined part. As a result, it becomes impossible to operate electronic components such as semiconductor elements to be mounted, so that a step of correcting a positional shift between the terminal portion and the socket is required, which causes a problem that mass productivity is reduced. Was. Also, even in the case of misalignment between the terminal portion and the socket that can be connected, the contact area between the terminal portion and the socket is reduced, the fitting force between the terminal portion and the socket is weak, and the terminal portion is easily detached, The mechanical and electrical connection reliability is reduced, for example, the contact resistance between the terminal and the socket is increased, and there is a problem that it is not possible to operate electronic components such as mounted semiconductor elements stably. I do. Such a problem tends to be particularly pronounced when a plurality of terminals are formed on the ceramic circuit board. SUMMARY OF THE INVENTION The present invention has been completed in view of the above problems, and has as its object to ensure sufficient accuracy of the bending position of the terminal portion of the terminal-integrated ceramic circuit board and to make the terminal-integrated ceramic circuit board a resin. Provided is a ceramic circuit board in which there is no displacement between a terminal portion and a socket of a resin case even when mounted on a case, and as a result, electronic components such as semiconductor elements to be mounted can be operated stably. It is in. According to the ceramic circuit board of the present invention, a metal circuit board made of oxygen-free copper is joined to the surface of the ceramic substrate via an active metal brazing material. A ceramic circuit board having a terminal portion extended and bent substantially perpendicularly to the ceramic substrate, wherein the terminal portion has a total depth on both sides of the bent portion corresponding to the width of the terminal portion. It is characterized by providing notches of 20% to 50%. According to the ceramic circuit board of the present invention, the terminal portion where a part of the metal circuit board made of oxygen-free copper is extended has a total depth on both sides of the bent portion with respect to the width of the terminal portion. Since the notch of 20% to 50% is provided, it is possible to bend precisely at the desired position where the notch is provided, and the terminal portion when mounting the terminal-integrated ceramic circuit board in the resin case is provided. And the socket of the resin case and the like can be displaced, and as a result, electronic components such as semiconductor elements to be mounted can be operated stably. Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a side view showing an embodiment of a ceramic circuit board according to the present invention, and FIG. 2 is a plan view thereof. In these figures, 1 is a ceramic board, 2 is a metal circuit board, and 3 is a metal board. The terminal portion 4 is an active metal brazing material, and 5 is a notch. The ceramic substrate 1 has a substantially square shape, and a metal circuit board 2 made of oxygen-free copper is joined to the surface of the ceramic substrate 1 via an active metal brazing material 4. The ceramic substrate 1 functions as a support member for supporting the metal circuit board 2 and is made of aluminum oxide (Al).
₂ O ₃ ) sintered body, mullite (3Al ₂ O ₃ · 2SiO ₂ )
It is formed of an electrically insulating material such as a sintered body of silicon, a sintered body of silicon carbide (SiC), a sintered body of aluminum nitride (AlN), and a sintered body of silicon nitride (Si ₃ N ₄ ). When the ceramic substrate 1 is formed of, for example, an aluminum oxide sintered body, an organic binder, a plasticizer, and a solvent suitable for a raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide. Is added and mixed to form a slurry, and the slurry is used to form a ceramic green sheet (ceramic green sheet) by employing a conventionally known doctor blade method or calender roll method. It is manufactured by subjecting a sheet to appropriate punching, stacking a plurality of the sheets, and firing at a high temperature of about 1600 ° C. The ceramic substrate 1 has a thickness of 0.2 to 1.0 m.
The value of m is generated in order to satisfy the demand for miniaturization and thinning of the ceramic circuit board, to suppress cracking of the ceramic substrate 1 when the metal circuit board 2 is joined, and to occur from a semiconductor element mounted. This is preferable from the viewpoint of improving the heat transfer of 100 ° C. or more. When the thickness of the ceramic substrate 1 is less than 0.2 mm, cracks and the like tend to occur easily in the ceramic substrate 1 due to stress generated when the metal circuit board 2 is joined to the ceramic substrate 1. On the other hand, 1.
If it exceeds 0 mm, it will be difficult to cope with the thinning of the ceramic circuit board, and it will be difficult to radiate the heat of 100 ° C. or more generated from the mounted semiconductor element through the ceramic board 1 satisfactorily. There is. The metal circuit board 2 is made of oxygen-free copper, and is joined to the surface of the ceramic substrate 1 via the active metal brazing material 4 as follows. First, a silver braze powder made of silver-copper alloy powder, an aluminum braze powder made of aluminum-silicon alloy powder, etc., and an active metal such as titanium, zirconium, hafnium or at least one hydride thereof are used. An active metal brazing material paste obtained by adding and mixing an active metal brazing material containing 2 to 5% by weight of active metal powder and an appropriate organic solvent / solvent is applied to the surface of the ceramic substrate 1 by using a conventionally known screen printing technique. To print in a predetermined pattern corresponding to the metal circuit board 2. In addition, since the part which becomes the terminal part 3 of the metal circuit board 2 is used by being bent substantially perpendicularly with respect to the ceramic substrate 1, the active metal brazing material paste is not printed on that part. Then, the metal circuit board 2 is placed on the pattern of the active metal brazing material paste, and the metal circuit board 2 is placed in a vacuum or in a neutral atmosphere or a reducing atmosphere at a predetermined temperature (approximately).
At 900 ° C.), the active metal brazing material is melted and the metal circuit board 2 is joined to the surface of the ceramic substrate 1. Thus, the metal circuit board 2 is joined to the surface of the ceramic substrate 1 via the active metal brazing material 4. The metal circuit board 2 made of oxygen-free copper is obtained by subjecting an ingot of oxygen-free copper to a conventionally known metal working method such as a rolling method or a punching method.
It has a thickness of 0.5 mm and is manufactured in a desired circuit wiring pattern shape. At this time, the terminal portion 3 integrated with the circuit wiring pattern and the notch 5 in the bent portion are also formed at the same time. The thickness of the metal circuit board 2 is set to 20 to 50 A in order to satisfy the demand for miniaturization and thinning of the ceramic circuit board.
0.1 to 1.0 in terms of satisfying the specification of electric resistance for transmitting a high current signal, and preventing cracking of the ceramic substrate 1 when the ceramic substrate 1 is joined to the ceramic substrate 1.
mm is preferred. When the thickness of the metal circuit board 2 is less than 0.1 mm, the electric resistance becomes large, so that a high current signal of 20 to 50 A tends to be difficult to flow favorably. On the other hand, 1.0m
m, it becomes difficult to cope with thinning,
The stress generated when the ceramic substrate 1 and the metal circuit board 2 are joined tends to easily cause cracks and the like in the ceramic substrate 1. Since the metal circuit board 2 is made of oxygen-free copper, the oxygen-free copper is used as an active metal brazing material 4 at the time of brazing.
Is not oxidized by oxygen present in oxygen-free copper, and has good wettability, so that it can be firmly bonded to the ceramic substrate 1. The terminal 3 extends as a part of the metal circuit board 2 and is formed integrally with the metal circuit board 2. Terminal 3
Is preferably processed so that its Vickers hardness is 100 Hv or more. Vickers hardness of terminal 3 is 100Hv
The reason for the above is that the tough pitch copper used as a normal terminal has a Vickers hardness of 80 Hv or more, so that the terminal integrated type ceramic circuit board can be mounted on a resin case. Deformation of part 3
This is because bending is eliminated, and as a result, electronic components such as semiconductor elements to be mounted can be operated stably. Suitable processing methods for setting the Vickers hardness of the terminal portion 3 to 100 Hv or more include electroless nickel plating, impact processing, and solder film forming processing. The electroless nickel plating on the terminal portion 3 is performed, for example, by electroless nickel plating containing phosphorus.
After that, a heat treatment is performed at a temperature of 250 ° C. or more to crystallize nickel-phosphorus to make Vickers hardness 100 Hv or more. At this time, the amount of phosphorus contained in the nickel film is preferably 8% by weight or more. If the phosphorus content is 8% by weight or less, the crystallization of the nickel-phosphorus compound is not sufficient, and as a result, the Vickers hardness of the terminal portion 3 is 100H.
This is because there is a tendency not to exceed v. In addition, other than phosphorus, a compound is formed with nickel to have a Vickers hardness of 10
Boron or the like may be used as long as it is 0 Hv or more. The thickness of the electroless nickel plating is 1.5
μm or more is preferred. 1.5μ thickness of electroless nickel plating
If it is less than m, the effect of increasing the Vickers hardness of the terminal portion 3 is small, and there is a tendency that a Vickers hardness of 100 Hv or more cannot be obtained. Further, the heat treatment at a temperature of 250 ° C. or higher is performed because if the heat is not applied, the crystallization of the nickel-phosphorus compound does not proceed at all and the Vickers hardness does not increase. This heat treatment may be performed by heat-treating the ceramic circuit board after forming the plating film, or by using heat treatment when mounting electronic components such as semiconductor elements on the ceramic circuit board having the plating film formed thereon by soldering or the like. Good. The impact processing on the terminal portion 3 includes, for example, sand blasting, wet blasting (a method of injecting abrasive grains and water by air pressure), and pressing with a mold.
In the case of impact processing by blasting, the blast processing may be performed only on the terminal portion 3, or the entire ceramic circuit board may be blasted to also serve as a step of removing foreign matter.
Pressing with a mold may be performed, for example, by using a device in which the terminal 3 is put into a mold and only the terminal 3 is hit with a hammer or the like. The solder film forming process on the terminal portion 3 includes, for example, a solder film forming process by solder plating and a solder film forming process by solder dipping. As the solder, a Pb-Sn-based or Sn-Ag-based solder containing Sn is used. The Sn forms the copper and the Cu—Sn alloy of the terminal portion 3, thereby increasing the Vickers hardness of the terminal portion 3. The terminal portion 3 has cutouts 5 on both sides of the bent portion so that the total depth is 20% to 50% of the width of the terminal portion 3. By providing the notch 5, it is possible to bend accurately at a desired position, and to eliminate the positional deviation between the terminal portion 3 and the socket of the resin case when the terminal-integrated ceramic circuit board is mounted on the resin case. As a result, electronic components such as semiconductor elements to be mounted can be operated stably. If the total depth of the notches 5 on both sides of the bent portion is less than 20% of the width of the terminal portion 3, the width of the bent portion is not sufficiently small with respect to the width of the terminal portion 3. It is difficult for stress to concentrate on the bent portion, and it becomes difficult to bend accurately at a desired position. If the total depth of the notches 5 exceeds 50% of the width of the terminal portion 3, the strength of the bent portion is reduced, and the terminal portion 3 may be broken at the bent portion when bent. is there. Even if it does not break at the time of bending, there is a risk that the terminal portion 3 may break due to repeated bending acting on the bent portion due to the difference in thermal expansion between the resin case and the ceramic circuit board after mounting on the resin case. is there. Even if it does not break, the bent terminal portion 3 is likely to be twisted and cannot be mounted on a resin case. Further, the depth of the notch 5 is preferably substantially equal on both sides of the bent portion. This is because if there is an extreme difference in the depth of the notch 5, the bent terminal portion 3 is likely to be twisted. In order for the terminal portion 3 to be bent substantially perpendicularly to the ceramic substrate 1, the notches 5 on both sides of the bent portion are formed by connecting the notches 5 on both sides with the extending direction of the terminal. Are arranged so as to intersect substantially at a right angle. The shape of the notch 5 is not particularly limited,
As shown in FIG. 2, by forming a shape such as an arc shape or a triangular shape in which stress is easily concentrated at the tip of the notch 5, the line connecting the tip of the notch 5 on both sides and the bending position are matched. The bending position accuracy can be further improved. Further, as shown in FIG. 3 in a plan view similar to FIG. 2, if the width of the metal circuit board 2 at one or both sides of the notch 5 is larger than the width of the terminal portion 3, it becomes easier to bend. . Further, if the portion for increasing the width is provided at the tip end side of the terminal portion 3, when the terminal-integrated ceramic circuit board is mounted on the resin case, the terminal portion 3 is prevented from excessively entering the socket or the like of the resin case. It can also be used as a stopper. The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the metal circuit board 2 is directly brazed to the ceramic substrate 1 via the active metal brazing material 4, but the metal circuit board 2 is previously formed on the surface of the ceramic substrate 1 by tungsten or molybdenum. The metal circuit board 2 may be bonded to the metallized metal layer via the active metal brazing material 4. In the above-described embodiment, the metal circuit board 2 previously formed in a circuit wiring pattern shape is brazed to the ceramic substrate 1 via the active metal brazing material 4. After the metal plate having the shape is brazed, unnecessary metal portions may be removed by etching to form the circuit wiring pattern and the terminal portion 3 having the notch 5. According to the ceramic circuit board of the present invention,
A metal circuit board made of oxygen-free copper is joined to the surface of the ceramic substrate via an active metal brazing material, and a part of the metal circuit board is extended and bent substantially perpendicularly to the ceramic substrate. The terminal portion is provided with a notch having a total depth of 20% to 50% with respect to the width of the terminal portion on both sides of the bent portion. It is possible to bend precisely at a desired position provided, and it is possible to eliminate a positional displacement between a terminal portion and a socket of the resin case when mounting the terminal-integrated ceramic circuit board on the resin case, and to provide a predetermined portion. As a result, it was possible to provide a ceramic circuit board capable of stably operating electronic components such as semiconductor elements to be mounted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing an example of an embodiment of a ceramic circuit board according to the present invention. FIG. 2 is a plan view showing an example of an embodiment of the ceramic circuit board of the present invention. FIG. 3 is a plan view showing another example of the embodiment of the ceramic circuit board of the present invention. [Description of Signs] 1: Ceramic substrate 2: Metal circuit board 3: Terminal section 4: Active metal brazing material 5: Notch

Claims (1)

Claims: 1. A metal circuit board made of oxygen-free copper is joined to the surface of a ceramic substrate via an active metal brazing material, and a part of the metal circuit board is extended to form the ceramic substrate. A terminal portion that is bent substantially perpendicular to the terminal portion, wherein the terminal portion has a total depth of 20% to 50% with respect to the width of the terminal portion on both sides of the bent portion. A ceramic circuit board having a notch.