JP7363583B2 - Manufacturing method of insulated circuit board - Google Patents

Description

The present invention relates to a method for manufacturing an insulated circuit board.

BACKGROUND ART As a circuit board formed by bonding a metal plate and a ceramic substrate, for example, insulated circuit boards described in Patent Documents 1 and 2 are known. The insulated circuit boards described in Patent Documents 1 and 2 include a ceramic substrate made of AIN (aluminum nitride), Al ₂ O ₃ (alumina), Si ₃ N ₄ (silicon nitride), etc. A circuit layer formed by bonding a first metal plate is provided on one surface of the substrate, and a heat dissipation layer formed by bonding a second metal plate is provided on the other surface.
In such an insulated circuit board, the circuit layer is divided into a plurality of parts by grooves to form a plurality of circuit patterns, so that the pattern shape of the circuit layer and the pattern shape of the heat dissipation layer are different.

Patent No. 3211856 Japanese Patent Application Publication No. 2014-172802

Incidentally, the insulated circuit boards disclosed in Patent Documents 1 and 2 are joined by heating a stacked body in which a first metal plate, a ceramic substrate, and a second metal plate are stacked while applying pressure in the stacking direction. However, when bonding them together, if the shape and thickness of the first metal plate that serves as the circuit layer differs from the shape and thickness of the second metal plate that serves as the heat dissipation layer, the insulated circuit board may warp (with the circuit layer on the top). convex warpage) occurs. In particular, when the first metal plate is made of multiple metal plates and the second metal plate is made of one metal plate, the warpage becomes large and the direction of the warp (convex or concave toward the circuit layer side) ) will fall apart.
In order to reduce the warpage and control the direction of the warp, a press plate having a predetermined radius of curvature is used to perform the bonding during pressurization, but in this case, a positional shift of the first metal plate with respect to the ceramic substrate occurs. If this warpage is large or misalignment occurs, misalignment will easily occur when semiconductor elements, etc. are mounted on the circuit layer, so it is desirable for the insulated circuit board to have a small amount of warpage. There is.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing an insulated circuit board that can suppress misalignment during bonding, reduce the amount of warpage, and unify the direction of warp. purpose.

In the method for manufacturing an insulated circuit board of the present invention, a first metal plate is placed on one side of a ceramic substrate, a second metal plate is placed on the other side of the ceramic substrate, and these laminates are stacked in the stacking direction. It has a joining process in which it is joined under pressure,
In the joining step, a first pressing plate having a convex curved surface pressing the first metal plate and a second pressing plate having a concave curved surface pressing the second metal plate are used to bond the ceramic of the first metal plate. A first surface opposite to the substrate is pressed by the convex curved surface via a first contact plate made of a flat plate, and a second surface of the second metal plate opposite to the ceramic substrate is pressed. The laminate is heated in a deformed state while being sandwiched between the first contact plate and the second contact plate by pressing the surface with the concave curved surface through a second contact plate made of a flat plate. ,
The first press plate and the second press plate are made of plate materials having a Young's modulus of 100 GPa or more, and the first contact plate and the second contact plate have a Young's modulus of 1 GPa or more and 70 GPa or less and a thickness of 0. It is set to 5 mm or more and 50 mm or less.
Note that the Young's modulus and thickness of the first contact plate and the second contact plate are values at 25°C.

In the present invention, the laminate of the first metal plate, the ceramic substrate, and the second metal plate is pressed while being warped in the opposite direction to the direction of warpage that may occur after the insulated circuit boards are joined. Warpage can be suppressed and the direction of warpage can be unified.

Here, when directly pressing the first surface of the first metal plate with the convex curved surface of the first pressing plate and directly pressing the second surface of the second metal plate with the concave curved surface of the second pressing plate, first, the convex curved surface of the second pressing plate The tip of the curved surface contacts the center of the first surface, and the range of contact with the first surface gradually expands from the center to the outer circumferential side and is pressed. On the other hand, in the case of the concave curved surface, its outer peripheral edge contacts the outer peripheral edge of the second surface, and the range of contact with the second surface expands from the outer peripheral edge toward the center and is pressed. In this case, each of the convex curved surface and the concave curved surface cannot press the entire area of the first surface of the first metal plate and the second surface of the second metal plate from the beginning. The pressure may cause the first metal plate and the second metal plate to slip on the ceramic substrate, causing positional deviation.

In contrast, in the present invention, the first contact plate is disposed between the convex curved surface and the first surface, and the second contact plate is disposed between the concave curved surface and the second surface. When the pressing starts, first, the tip of the convex curved surface contacts the center of the first contact plate. This first contact plate has a Young's modulus of 1 GPa or more and 70 GPa or less, and a thickness of 0.5 mm or more and 50 mm or less, so it is bent by the pressing force of the tip of the convex curved surface. The first metal plate is also pressed by the outer peripheral portion of the first contact plate that is not in contact with the first metal plate. That is, even if only the center of the first contact plate is pressed, the state in which the entire surface of the first metal plate is pressed is maintained. As the pressure on the convex curved surface progresses, the pressure expands from the center of the first contact plate toward the outer circumference, but even in this case, the first contact plate is appropriately bent to press the entire surface of the first metal plate. The state is maintained. The same applies to the second contact plate, and while being pressed by the concave curved surface, the state in which the second contact plate presses the entire surface of the second metal plate is maintained. Therefore, it is possible to suppress the occurrence of misalignment of the first metal plate and the second metal plate with respect to the ceramic substrate in the bonding process.
In addition, since the first contact plate and the second contact plate are formed of flat plates, when placing the laminate sandwiched between the first contact plate and the second contact plate between the convex curved surface and the concave curved surface, , these can be arranged horizontally, and positional shifts that occur when arranging the laminate can be suppressed.

Note that when the Young's modulus of the first contact plate and the second contact plate is less than 1 GPa and the thickness is less than 0.5 mm, the tip of the convex curved surface contacts the center of the first contact plate, and the first contact plate Even if the first contact plate is bent, the pressing force against the peripheral edge of the first metal plate is low, and there is a risk of positional displacement. On the other hand, if the Young's modulus of the first contact plate and the second contact plate exceeds 70 GPa and the thickness exceeds 50 mm, excessive force will be required to deflect them, and the load applied during joining will deform them. Therefore, it may not be possible to suppress warping.

In the method for manufacturing an insulated circuit board according to the present invention, the first metal plate may include a plurality of metal plates arranged side by side in a surface direction of the ceramic substrate.
When the first metal plate is composed of a plurality of metal plates, there is a high possibility that the plurality of metal plates will be displaced due to the pressure of the convex curved surface. Even in this case, the state in which the first contact plate contacts and presses the entire surfaces of the plurality of metal plates when pressing on the convex curved surface is maintained. That is, the present invention is particularly effective when the first metal plate is composed of a plurality of metal plates, and can suppress misalignment of the first metal plate and the second metal plate with respect to the ceramic substrate.

In a preferred embodiment of the method for manufacturing an insulated circuit board of the present invention, the radius of curvature of the convex curved surface and the concave curved surface is preferably 100 mm or more and 5000 mm or less.
If the radius of curvature of the convex curved surface and the concave curved surface is less than 100 mm, the radius of curvature is too small and there is a risk that cracks may occur in the insulated circuit board, and the first metal plate is likely to be deformed into a concave shape after bonding. On the other hand, if it exceeds 5000 mm, the radius of curvature is too large, and the effect of suppressing warpage after bonding of the insulated circuit board is poor.

According to the present invention, it is possible to suppress misalignment during bonding of the first metal plate and the second metal plate to the ceramic substrate, reduce the amount of warpage, and unify the direction of warp.

FIG. 1 is a cross-sectional view showing a power module using an insulated circuit board according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a method of manufacturing the insulated circuit board shown in FIG. 1, and is a cross-sectional view showing a state in which metal plates are arranged on both sides of a ceramic substrate. FIG. 2 is a cross-sectional view illustrating a method of manufacturing the insulated circuit board shown in FIG. 1, and is a cross-sectional view showing a state in which a laminate is placed in a bonding device and contact plates are placed on both surfaces thereof. FIG. 2 is a cross-sectional view illustrating a method for manufacturing the insulated circuit board shown in FIG. 1, and is a cross-sectional view showing a state in which a laminate is being pressed by a bonding device.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

A heat sink 20 is joined to an insulated circuit board 10 manufactured by the method for manufacturing an insulated circuit board according to the present invention, thereby forming an insulated circuit board 1 with a heat sink.

[Power module configuration]
Then, by mounting the semiconductor element 30 and the like on the surface of this insulated circuit board 1 with a heat sink, an electronic component is manufactured as shown in FIG. 1. Examples of the semiconductor element 30 include a power semiconductor element, an LED element, a thermoelectric conversion element, and the like. In this embodiment, a power module 100 (electronic component) using a power semiconductor element as the semiconductor element 30 will be described.
Note that the power module 100 including the heat sink 20 is used, for example, while being attached to a cooler or the like.

[Configuration of insulated circuit board]
The insulated circuit board 10 includes a ceramic substrate 11 , a circuit layer 12 laminated on one surface of the ceramic substrate 11 , and a heat dissipation layer 13 laminated on the other surface of the ceramic substrate 11 .
The ceramic substrate 11 is an insulating material that prevents electrical connection between the circuit layer 12 and the heat dissipation layer 13, and is made of, for example, aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), etc. is 0.2 mm to 1.2 mm. Further, the planar size of the ceramic substrate 11 is set to, for example, 30 to 160 mm x 30 to 160 mm.

The circuit layer 12 is formed on one surface of the ceramic substrate 11, and is divided into two circuit patterns (small circuit layers 120a and 120b). This circuit layer 12 is composed of two copper plates made of pure copper such as oxygen-free copper or a copper alloy such as zirconium-added copper alloy.
The heat dissipation layer 13 is formed on the other surface of the ceramic substrate 11, and is made of a copper plate made of pure copper such as oxygen-free copper or a copper alloy such as zirconium-added copper alloy. In other words, the shape of the circuit layer 12 and the shape of the heat dissipation layer 13 are different.
Further, the thickness of the circuit layer 12 and the heat dissipation layer 13 is set to 0.4 mm to 1.6 mm, which is slightly smaller than the ceramic substrate 11.

[Method for manufacturing insulated circuit board]
Next, a method for manufacturing the insulated circuit board 10 of this embodiment will be described.
The manufacturing method includes arranging first metal plates 121 and 122 corresponding to the circuit layer 12 (corresponding to the two small circuit layers 120a and 120b) on one surface of a ceramic substrate 11 with a brazing material foil 14 in between. , a second metal plate 130 serving as a heat dissipation layer 13 is placed on the other surface of the ceramic substrate 11 via a brazing material foil 14, and these are laminated by an insulated circuit board manufacturing apparatus 60 (hereinafter referred to as manufacturing apparatus 60). It has a joining process of heating while being pressed in the direction and joining by brazing.

(Configuration of insulated circuit board manufacturing equipment)
Here, in the insulated circuit board 10, since the size of the first metal plates 121, 122, which become the circuit layer 12 (two small circuit layers 120a, 120b), and the size of the second metal plate 130 are different, the circuit layer is layered after bonding. There is a tendency for a convex warp with 12 on the upper side to occur. In order to suppress this warping, in this embodiment, the manufacturing apparatus 60 is used to deform the ceramic substrate 11 into a concave shape with the circuit layer 12 on the upper side, while deforming the ceramic substrate 11 in a direction opposite to the direction of the warp that occurs after bonding. The first metal plates 121, 122 and the second metal plate 130 are joined.

As shown in FIGS. 3 and 4, this manufacturing apparatus 60 laminates a laminate 40 of first metal plates 121 and 122, a ceramic substrate 11, and a second metal plate 130, which are arranged side by side in the surface direction of a ceramic substrate 11. It is provided with a first pressing plate 61 and a second pressing plate 62 that press in the direction. The first pressing plate 61 has a convex curved surface 611 that can press the first surfaces 121A, 122A of the first metal plates 121, 122 opposite to the ceramic substrate 11. Further, the second pressing plate 62 has a concave curved surface 621 that can press the second surface 130A of the second metal plate 130, which is the surface opposite to the ceramic substrate 11.
In addition, when the manufacturing apparatus 60 presses the laminate 40 with the first pressing plate 61 and the second pressing plate 62, a first contact plate 71 disposed between the convex curved surface 611 and the first surfaces 121A and 122A. and a second contact plate 72 disposed between the concave curved surface 621 and the second surface 130A.

Among these, it is preferable that the first pressing plate 61 and the second pressing plate 62 have a larger planar size than the first contact plate 71 and the second contact plate 72. Further, the first pressing plate 61 and the second pressing plate 62 are formed of a plate material (for example, stainless steel material, ceramics such as aluminum nitride) having a Young's modulus of 100 GPa or more. The thickness of the first pressing plate 61 and the second pressing plate 62 is preferably 5 mm or more and 100 mm or less.
The convex curved surface 611 of the first pressing plate 61 is a convex curved surface with a radius of curvature R of 100 mm or more and 5000 mm or less. Further, the concave curved surface 621 of the second pressing plate 62 is a concave curved surface whose radius of curvature R corresponding to the convex curved surface 611 is 100 mm or more and 5000 mm or less. Specifically, the convex curved surface 611 is a convex curved surface that slopes downward from the virtual line C1 extending in the thickness direction through the center of the insulated circuit board 10 shown in FIG. , is a concave curved surface having an upward slope from the virtual line C1 to the peripheral edge.

Note that if the radius of curvature R of the convex curved surface 611 and the concave curved surface 621 is less than 100 mm, the radius of curvature is too small and there is a risk that cracks may occur in the insulated circuit board 10, and the first metal plates 121 and 122 may have a concave shape after bonding. Deformation tends to remain. On the other hand, if it exceeds 5000 mm, the radius of curvature is too large, and the effect of suppressing warping of the insulated circuit board 10 after bonding is poor.

It is preferable that the first contact plate 71 and the second contact plate 72 have the same or larger planar size than the first metal plates 121, 122 and the second metal plate 130, respectively. The first contact plate 71 and the second contact plate 72 have a Young's modulus of 1 GPa or more and 70 GPa or less, and a thickness w1 of 0.5 mm or more and 50 mm or less, and are made of, for example, a carbon plate, a carbon composite, a graphite sheet, etc. Consisting of Note that the Young's modulus and thickness of the first contact plate 71 and the second contact plate 72 are values at 25°C.
When the Young's modulus of the first contact plate 71 and the second contact plate 72 is less than 1 GPa and the thickness w1 is less than 0.5 mm, the tip of the convex curved surface 611 contacts the center of the first contact plate 71. Therefore, even if the first contact plate 71 is bent, the pressing force against the peripheral edges of the first metal plates 121 and 122 is weak, resulting in positional displacement. On the other hand, if the Young's modulus of the first contact plate 71 and the second contact plate 72 exceeds 70 GPa and the thickness w1 exceeds 50 mm, excessive force will be required to deflect them, which will be applied during bonding. Since it becomes difficult to deform under load, it may not be possible to suppress warping.
Therefore, in this embodiment, the Young's modulus of the first contact plate 71 and the second contact plate 72 is set to be 1 GPa or more and 70 GPa or less, and the thickness w1 is set to 0.5 mm or more and 50 mm or less.

(Method for manufacturing an insulated circuit board using manufacturing equipment)
To manufacture the insulated circuit board 10 using such a manufacturing apparatus 60, first, as shown in FIG. A laminate 40 is formed by laminating a brazing material (for example, Ag--Cu--Ti based) through a brazing material foil 14.
Note that in this embodiment, the brazing material foil 14 is used, but the present invention is not limited to this, and a brazing material paste may also be used. In this case, the brazing material paste may be applied to the ceramic substrate 11 or may be applied to the first metal plates 121 and 122 and the second metal plate 130.

As shown in FIG. 3, the first contact plate 71 is placed on the first metal plate 121, 122 side of the laminate 40, and the second contact plate 72 is placed on the second metal plate 130 side. It is placed between the convex curved surface 611 and the concave curved surface 621 with the laminate 40 sandwiched therebetween. Thereafter, the first pressing plate 61 and the second pressing plate 62 press these in the stacking direction.

In this state, when the first pressing plate 61 and the second pressing plate 62 start pressing the laminate, as shown in FIG. come into contact with. The first contact plate 71 has a Young's modulus of 1 GPa or more and a thickness of 70 GPa or less and a thickness of 0.5 mm or more and 50 mm or less. The first metal plates 121 and 122 are also pressed on the outer circumferential portion of the first contact plate 71 with which the tip portions are not in contact. That is, even if only the center of the first contact plate 71 is pressed, the state in which the entire surfaces of the first metal plates 121 and 122 are pressed is maintained. As the pressing of the convex curved surface 611 progresses, the first contact plate 71 is expanded and pressed from the center to the outer circumferential side, but even in this case, the first contact plate 71 is appropriately bent and the first metal plate 121, The state in which the entire surface of 122 is pressed is maintained. The same applies to the second contact plate 72, and while being pressed by the concave curved surface 621, the second contact plate 72 is bent to maintain a state in which the entire surface of the second metal plate 130 is pressed. Therefore, it is possible to suppress the occurrence of misalignment of the first metal plates 121, 122 and the second metal plate 130 with respect to the ceramic substrate 11 in the bonding process.

Then, by heating this laminate 40 under further pressure in the stacking direction and then cooling it, the first metal plates 121 and 122 are joined to one surface of the ceramic substrate 11, and the second metal plate is bonded to the other surface. Metal plate 130 is joined. The brazing filler metal foil 14 is melted by heating, diffuses into the first metal plates 121 and 122 and the second metal plate 130, and firmly joins them to the ceramic substrate 11.
The bonding conditions at this time are not necessarily limited, but in a vacuum atmosphere, the pressure in the stacking direction is 0.1 MPa to 1.0 MPa, and the heating temperature is 800°C to 930°C for 20 minutes or more. It is preferable to hold the temperature for 120 minutes or less.

According to this manufacturing method, the laminate 40 of the first metal plates 121, 122, the ceramic substrate 11, and the second metal plate 130 is pressed while being warped in the opposite direction to the direction of warpage that may occur after the insulated circuit board 10 is bonded. By doing so, it is possible to suppress warping of the insulated circuit board 10 after bonding and to unify the direction of the warp. Further, even when a portion of the first contact plate 71 and the second contact plate 72 are pressed by the convex curved surface 611 and the concave curved surface 621, respectively, the first contact plate 71 and the second contact plate 72 are bent. Since the entire surfaces of the first surfaces 121A, 122A and the second surface 130A are kept in contact with each other and pressed, misalignment of the first metal plates 121, 122 and the second metal plate 130 with respect to the ceramic substrate 11 during the bonding process can be avoided. can be suppressed.
Note that, since the first contact plate 71 and the second contact plate 72 are formed of flat plates, the laminate 40 sandwiched between the first contact plate 71 and the second contact plate 72 is placed between the convex curved surface 611 and the concave curved surface 621. Even when disposed between them, they can be arranged horizontally, and positional deviations that occur when arranging the laminate 40 can be suppressed.

Furthermore, since the radius of curvature of the convex curved surface 611 of the first pressing plate 61 and the concave curved surface 621 of the second pressing plate 62 is set to 100 mm or more and 5000 mm or less, cracks etc. in the insulated circuit board 10 can be suppressed. , warpage can be reduced.

In this embodiment, since the first metal plates 121 and 122 are made of a plurality of metal plates, there is a high possibility that the plurality of metal plates 121 and 122 will be displaced due to the pressure of the convex curved surface 611. When pressed, the state in which the first contact plate 71 is in contact with the entire surfaces of the plurality of metal plates 121 and 122 is maintained. In other words, the manufacturing method of this embodiment is particularly effective when the first metal plate consists of a plurality of metal plates 121, 122, and even in this case, the first metal plate 121, 122 and the second metal plate relative to the ceramic substrate 11 are Misalignment of the plate 130 can be suppressed.

In addition, the detailed configuration is not limited to that of the embodiment, and various changes can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the first metal plate is made up of two metal plates 121 and 122, but the first metal plate may be made of one metal plate, or may be made of three or more metal plates. It may also be formed from a metal plate. Although there is no limitation on the method of manufacturing the first metal plate, it is particularly preferable to manufacture the first metal plate by a pressing method.

In the above embodiment, the circuit layer 12 and the heat dissipation layer 13 are both formed of copper such as oxygen-free copper, or a zirconium-added copper alloy, but are not limited to this, and may be formed of aluminum or an aluminum alloy. You can leave it there. In this case, the circuit layer 12 and the heat dissipation layer 13 are made of a pure aluminum plate with a purity of 99% by mass or more, pure aluminum in the 1000 series according to the JIS standard, especially 1N90 (purity of 99.9% by mass or more: so-called 3N aluminum) or 1N99 (purity of 3N aluminum). 99.99% by mass or more: so-called 4N aluminum). Further, the circuit layer 12 and the heat dissipation layer 13 may have a two-layer structure, in which case the first layer, the circuit layer and the heat dissipation layer, are made of pure aluminum, and the second layer, the circuit layer and the heat dissipation layer, are made of pure aluminum. may be made of copper or an aluminum alloy such as A6063 or A3003.
Further, the composition of the circuit layer 12 and the composition of the heat dissipation layer 13 may be different. That is, the present invention can be applied to an insulated circuit board that may warp when the insulated circuit board 10 is joined.

In the above embodiment, an example was shown in which the laminate 40 of the first metal plates 121, 122, the ceramic substrate 11, and the second metal plate 130 is pressed by the first pressing plate 61 and the second pressing plate 62, but the invention is not limited to this. First, for example, a plurality of laminates 40 may be stacked and pressed at the same time.

In the above embodiment, the manufacturing apparatus 60 that includes the first contact plate 71 and the second contact plate 72 is used, but the present invention is not limited to this. The laminate 40 may be placed between the first press plate 61 and the second press plate 62 and bonded to the device 60 via a first contact plate 71 and a second contact plate 72 that are separately prepared.

For Examples 1 to 6 and Comparative Examples 1 to 12, a ceramic substrate 70 mm x 70 mm in plan view and 0.32 mm thick made of silicon nitride and two first metal sheets made of oxygen-free copper were used. plates (one sheet of 33 mm x 68 mm in plan view and 0.8 mm thickness and the other plate of 33 mm x 68 mm in plan view and 0.8 mm thickness), one second plate made of oxygen-free copper; A metal plate (68 mm x 68 mm in plan view, thickness 0.8 mm) is laminated in the order of the first metal plate, the ceramic substrate, and the second metal plate, using the insulated circuit board manufacturing apparatus of the above embodiment. I joined it. Note that the two first metal plates were arranged parallel to the surface of the ceramic substrate in a plan view with a gap of 2 mm between them.
The Young's modulus of the first press plate and the second press plate of the manufacturing apparatus, and the Young's modulus and thickness of the first contact plate and the second contact plate were as shown in Table 1. Further, the thickness of the first pressing plate and the second pressing plate is 20 mm, the radius of curvature R of the convex curved surface and the concave curved surface is 2000 mm, and the joining of the ceramic substrate, the first metal plate, and the second metal plate is as follows. An Ag-Cu-Ti brazing filler metal foil with a thickness of 10 μm was used. In addition, the manufacturing procedure is the same as in the above embodiment, in which a first metal plate is placed on one side of the ceramic substrate with a brazing metal foil interposed therebetween, and a second metal plate is placed on the other side with a brazing metal foil interposed therebetween. A laminate was formed by arranging the laminate, and this laminate was sandwiched between the first and second contact plates and placed between the first and second pressing plates, and these were heated and bonded while being pressed. The bonding conditions at this time were that the pressure in the stacking direction was 0.5 MPa in a vacuum atmosphere, and the heating temperature was maintained at 810° C. for 70 minutes. Note that 30 samples were prepared for each sample.

The positional accuracy and warpage of the insulated circuit boards of Examples 1 to 6 and Comparative Examples 1 to 12 manufactured using this procedure were evaluated.
To evaluate the positional accuracy, 20 samples were taken out of each sample, and using an image measuring device (Quick Scope) manufactured by Mitutoyo Co., Ltd., two first metal plates and a ceramic substrate were measured for each insulated circuit board. The distance shifted in either horizontal direction from each planned joining position was measured. When the average value of all of these shifted distances was larger than ±0.25 mm, it was determined to be unacceptable “B”, and when it was within ±0.25 mm, it was evaluated as good “A”.

Moreover, the warpage evaluation was as follows.
The amount of warpage is measured using a dial gauge (manufactured by Mitutoyo) with a single point in the center. Place it on the surface plate with the circuit layer side facing down. Touch the probe to the center of the heat dissipation layer side and set that point as the zero point. Thereafter, a measuring element is brought into contact with the vicinity of the center of each of the two first metal plates on the circuit layer side, and the average value of the values is defined as the amount of warpage.
At this time, the direction of the warp was determined by setting a convexity toward the metal layer side when the amount of warpage was negative, and a convexity toward the circuit layer side when the amount of warpage was positive.
Twenty pieces were taken out from each of the prepared samples, and the direction and amount of warpage of each insulated circuit board was measured using the method described above.
If the average value of the amount of warpage of each sample is 30 μm or less and the warp direction is the same for all insulated circuit boards, it is evaluated as good "A", and if the average value of the amount of warp of each sample exceeds 30 μm. In the case where the direction of warpage was different even in one direction, it was evaluated as "B".
The positional accuracy and evaluation of warpage are shown in Table 1.

As is clear from Table 1, the Young's modulus of the first and second pressing plates is 100 GPa or more, the Young's modulus of the first and second contact plates is 1 GPa or more and 70 GPa or less, and the thickness is 0.5 mm to 50 mm. In Examples 1 to 6, both the positional accuracy evaluation and the warpage evaluation were good "A", and it was found that the positional shift of the circuit layer and the heat dissipation layer with respect to the ceramic substrate could be suppressed and the warpage could be reduced.
On the other hand, in Comparative Examples 1 and 4, the Young's modulus of the first and second contact plates was as low as 0.5 GPa, which caused positional deviation of the circuit layer and heat dissipation layer with respect to the ceramic substrate, making it impossible to evaluate the position accuracy. It was "B". In addition, in Comparative Examples 2 and 3, the Young's modulus of the first and second contact plates was too high at 100 GPa, so it was not possible to provide sufficient warpage in the opposite direction to the warpage that occurs on the insulated circuit board. The evaluation was "B".
In addition, in Comparative Examples 5 and 8, the thickness of the first and second contact plates was too thin at 0.3 mm, which caused misalignment of the circuit layer and heat dissipation layer with respect to the ceramic substrate, making it impossible to evaluate position accuracy. It was "B". In addition, in Comparative Examples 6 and 7, the thickness of the first and second contact plates was too thick at 60 mm, so it was not possible to provide sufficient warpage in the opposite direction to the warpage that occurs on the insulated circuit board. The evaluation was "B".
Furthermore, in Comparative Examples 9 to 12, since the Young's modulus of the first and second pressing plates was as low as 50 GPa, it was not possible to properly press the insulated circuit board, and it was also not possible to apply warpage in the opposite direction, resulting in positional accuracy. Both the evaluation and the warp evaluation were rated "B".

1 Insulated circuit board with heat sink 10 Insulated circuit board 11 Ceramic substrate 12 Circuit layer 13 Heat dissipation layer 20 Heat sink 30 Semiconductor element 61 First press plate 62 Second press plate 611 Convex curved surface 621 Concave curved surface 71 First contact plate 72 Second contact plate 120a, 120b Small circuit layer 121, 122 First metal plate (multiple metal plates)
121A, 122A First surface 130 Second metal plate 130A Second surface C1 Virtual line

Claims (3)

The method includes a bonding step of arranging a first metal plate on one surface of a ceramic substrate, arranging a second metal plate on the other surface of the ceramic substrate, and bonding these laminates while being pressed in the stacking direction. death,
In the joining step, a first pressing plate having a convex curved surface pressing the first metal plate and a second pressing plate having a concave curved surface pressing the second metal plate are used to bond the ceramic of the first metal plate. A first surface opposite to the substrate is pressed by the convex curved surface via a first contact plate made of a flat plate, and a second surface of the second metal plate opposite to the ceramic substrate is pressed. The laminate is heated in a deformed state while being sandwiched between the first contact plate and the second contact plate by pressing the surface with the concave curved surface through a second contact plate made of a flat plate. ,
The first pressing plate and the second pressing plate are made of plate materials having a Young's modulus of 100 GPa or more, and the first contact plate and the second contact plate have a Young's modulus of 1 GPa or more and 70 GPa or less and a thickness of 0.5 mm. A method for manufacturing an insulated circuit board, characterized in that the thickness is set to 50 mm or less. 2. The method of manufacturing an insulated circuit board according to claim 1, wherein the first metal plate includes a plurality of metal plates arranged side by side in a surface direction of the ceramic substrate. 3. The method of manufacturing an insulated circuit board according to claim 1, wherein the radius of curvature of the convex curved surface and the concave curved surface is 100 mm or more and 5000 mm or less.

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