JP7243201B2 - Manufacturing method of insulated circuit board with heat sink and insulated circuit board with heat sink - Google Patents

Description

The present invention relates to a method for manufacturing an insulating circuit board with a heat sink, in which a heat sink is bonded to an insulating circuit board such as a power module board used in a semiconductor device that controls large currents and high voltages, and an insulating circuit board with a heat sink.

As a power module substrate, a circuit layer made of aluminum or an aluminum alloy is formed on one side of an insulating layer made of a ceramic substrate such as aluminum nitride, and a metal layer is formed on the other side. is known. Such an insulated circuit board with a heat sink generally has a larger volume on the side opposite to the circuit layer than the volume of the circuit layer, and the heat sink is made of aluminum alloy or copper harder than the aluminum forming the circuit layer. ing. For this reason, such an insulated circuit board with a heat sink warps convexly toward the circuit layer side.

As a method for improving the warpage of such an insulating circuit board with a heatsink, for example, a method for manufacturing a power module board with a heatsink described in Patent Document 1 is known. In this manufacturing method, the heat sink is formed of a material having a high yield stress with respect to the metal layer, and when the heat sink and the power module substrate are joined together, the laminate of the heat sink and the power module substrate is aligned with the heat sink in the stacking direction. A power module substrate with a heatsink with reduced warpage is obtained by keeping the substrate in a heated state for a predetermined period of time and then cooling it.

JP 2015-76551 A

Since the power module substrate with a heat sink manufactured by the method for manufacturing a power module substrate with a heat sink described in the above-mentioned Patent Document 1 has a small amount of warpage, the effect on the module performance of the power module using this is small. rice field. However, when an LED element is used as an electronic component and an insulated circuit board with a heat sink is used as an LED heat dissipation module with a light distribution control function, the mounting position and angle of the LED element on the mounting surface of the circuit layer must be extremely precise. Since it must be controlled, even a slight convex warp, which did not pose a problem when used as a power module, causes the optical axis of each light source to shift, making it difficult to use as an LED heat dissipation module.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing an insulating circuit board with a heat sink and an insulating circuit board with a heat sink that can improve the flatness of a circuit layer that serves as a mounting surface for electronic components and the like. With the goal.

A method for manufacturing an insulated circuit board with a heatsink according to the present invention includes bonding a heatsink to a surface opposite to the circuit layer of an insulated circuit board in which a circuit layer is bonded to one surface of a ceramic substrate , and further bonding the insulation A joining step of curving the whole of the circuit board and the heat sink to the circuit layer side in a convex shape , and after the joining step, polishing the center portion located inside the outer peripheral portion of the convex surface of the circuit layer to flatten the mounting. and a polishing step for forming a surface.

Here, when the insulated circuit board with a heat sink is warped convexly toward the circuit layer, when an LED element or the like is mounted on this circuit layer and used as an LED heat dissipation module, the LED element (LED light source) emits light The optical axis of light deviates, and the light distribution control function deteriorates. On the other hand, in the present invention, the insulating circuit board with a heat sink is formed by polishing the convex surface of the circuit layer after bonding the heat sink to the insulating circuit board in the bonding step, thereby forming a flat mounting surface. It is possible to improve the flatness of the mounting surface on which the components such as are mounted. Moreover, the flatness of the mounting surface can be improved by a simple method of polishing the convex surface of the circuit layer.

An insulated circuit board with a heat sink of the present invention is an insulated circuit board with a heat sink in which a circuit layer is formed on one side of a ceramic substrate and a heat sink is arranged on the side opposite to the circuit layer of the insulated circuit board. , the insulated circuit board with a heat sink as a whole has a convex shape along the side of the circuit layer, and a flat mounting surface is formed in the central portion located inside the outer peripheral portion of the convex surface of the circuit layer. is

In the present invention, the heat sink is configured to have a convex curved surface, that is, the entire insulated circuit board with the heat sink is convexly curved toward the circuit layer. Even if the entire insulated circuit board with a heat sink is warped in a convex shape, a flat mounting surface is formed at least in the center of the convex surface of the circuit layer. can be used and is suitable for use.

According to the present invention, it is possible to improve the flatness of the circuit layer that serves as the mounting surface for electronic components and the like.

1 is a cross-sectional view showing an LED module in which an LED element is attached to an insulating circuit board with a heat sink according to one embodiment of the present invention; FIG. It is a figure which shows the manufacturing process of the LED module of the said embodiment. It is a sectional view showing the LED module concerning the example of a changed completely type of the above-mentioned embodiment. FIG. 11 is a cross-sectional view showing an LED module according to another modified example of the embodiment;

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an LED module 40 according to this embodiment, and FIG. 2 is a diagram showing a manufacturing process of the LED module 40. FIG.

[Schematic configuration of LED module]
The LED module 40 according to this embodiment is configured by mounting the LED element 30 on the insulating circuit board 1 with a heat sink, as shown in FIG. Such an LED module 40 is configured by being attached to a housing (not shown), and is used, for example, as a headlamp of an automobile.

[Configuration of insulation circuit board with heat sink]
This insulating circuit board 1 with a heatsink is obtained by bonding a heatsink 20 to an insulating circuit board 10 . Specifically, the insulating circuit board 10 is a so-called power module board, and one LED element 30 is mounted on the upper surface of the insulating circuit board 10 as shown in FIG. In addition, although the LED element 30 is provided in this embodiment, it is not limited to this, and is, for example, an electronic component including a semiconductor, such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). , FWD (Free Wheeling Diode), etc. are selected.

In this case, although not shown, the LED element 30 is provided with an upper electrode portion on the upper portion and a lower electrode portion on the lower portion. By bonding, the LED element 30 is mounted on the convex surface 121 of the circuit layer 12 . For example, in the present embodiment, four are mounted on the mounting surface Ar2 located inside the outer peripheral portion Ar1 of the convex surface 121 of the circuit layer 12 . Also, the upper electrode portion of the LED element 30 is connected to the circuit electrode portion of the circuit layer 12 or the like via a lead frame or the like joined by solder or the like, and the LED module 40 is manufactured.

[Configuration of insulation circuit board]
The insulating circuit board 10 includes a ceramic substrate 11 , a circuit layer 12 formed on one surface of the ceramic substrate 11 , and a metal layer 13 formed 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 metal layer ₁₃ , and is made of, for example, aluminum nitride (AlN), silicon nitride ( _Si3N4 ), alumina ( _{Al2O3 )} . etc., and its thickness is 0.2 mm to 1.2 mm.

The circuit layer 12 is bonded to the ceramic substrate 11 . This circuit layer 12 is made of pure aluminum with a purity of 99% by mass or more (for example, pure aluminum in the 1000s according to JIS standards, particularly 1N90 (purity of 99.9% by mass or more: so-called 3N aluminum) or 1N99 (purity of 99.99% by mass). % or more: so-called 4N aluminum), aluminum alloys such as A6063 series, etc. can be used, and the thickness is set to 0.05 mm to 0.2 mm.In addition, pure copper such as oxygen-free copper, or It is also possible to use copper alloys.
A mounting surface 122 positioned at the center of the convex surface 121 of the circuit layer 12 is formed in a rectangular shape in a plan view and is composed of a flat surface. For example, the mounting surface 122 is formed in a rectangular shape of 13 mm square, and the amount of warp is set to 10 μm or less. Although the size of the mounting surface 122 is a 13 mm square rectangle, it is not limited to this, and may be, for example, a 50 mm square rectangle. Also in this case, the amount of warpage is set to 10 μm or less. That is, regardless of the size of mounting surface 122, the amount of warpage is preferably set to 10 μm or less.

The metal layer 13 is made of pure aluminum or an aluminum alloy with a purity of 99% by mass or more, and JIS standard 1000 aluminum, particularly 1N99 (purity of 99.99% by mass or more: so-called 4N aluminum) can be used. The thickness is set between 0.6 mm and 1.6 mm. It is also possible to use pure copper such as oxygen-free copper, or a copper alloy.

The circuit layer 12 and the metal layer 13 are laminated in the order of the circuit layer 12, the ceramic substrate 11, and the metal layer 13 via, for example, an Al--Si or Al--Si--Mg brazing material. are pressed in the stacking direction and heated to be joined to form the insulated circuit board 10 .

[Heat sink configuration]
The heat sink 20 joined to the insulating circuit board 10 is formed by forging an aluminum alloy such as A6063 series. The metal layer 13 of the insulating circuit board 10 is laminated on the upper surface of the heat sink 20 via an Al--Si--Mg brazing material. are joined together to form the insulated circuit board 1 with a heat sink.
In this embodiment, the entire insulating circuit board 1 with a heat sink is convexly warped toward the circuit layer 12 . That is, the surface of the heat sink 20 opposite to the insulating circuit board 10 is formed in a convex curved shape.

Next, a method for manufacturing the insulating circuit board 1 (LED module 40) with a heat sink according to this embodiment will be described.
Such an insulated circuit board 1 with a heat sink has a bonding process of bonding the heat sink 20 to the surface of the ceramic substrate 11 of the insulated circuit board 10 opposite to the circuit layer 12, and the convex surface 121 of the circuit layer 12 after the bonding process. and a polishing step of polishing to form a flat mounting surface 122 at the center thereof.

[Joining process]
In the bonding step, as shown in FIG. 2A, the circuit layer 12 is bonded to one surface of the ceramic substrate 11, and the heat sink is attached to the metal layer 13 of the insulated circuit substrate 10 having the metal layer 13 bonded to the other surface. 20 is joined. Specifically, an Al-Si-Mg-based brazing material is applied to the upper surface of the heat sink 20, the metal layer 13 of the insulated circuit board 10 is laminated thereon, and these are pressed in the lamination direction. By heating, the heat sink 20 is joined to the insulating circuit board 10 to form the insulating circuit board 1 with the heat sink.
In the bonding process, when the insulated circuit board 10 and the heat sink 20 are pressurized and heated, they are flat and not warped. As shown in FIG. 2(b), the entire insulated circuit board 1 with a heat sink has a shape that protrudes toward the circuit layer 12 side.

[Polishing process]
After the bonding process, after the insulated circuit board 1 with a heat sink is brought to room temperature, as shown in FIG. Execute the process. In this polishing step, the central portion of the circuit layer 12 is polished with polishing paper or polishing cloth. For example, wet polishing is performed with emery paper of No. 200 to No. 4000 under a pressure of 0N or more and 5N or less. As a result, the warp amount of the mounting surface 122 is set to 10 μm or less. At this time, if the emery paper is less than No. 200, the emery paper is too coarse to make the mounting surface 122 evenly flat. takes time. Moreover, if the pressure applied to the emery paper exceeds 5 N, the pressure is too great, making it difficult to uniformly flatten the mounting surface 122 . Further, in this embodiment, since the circuit layer 12 is polished by wet polishing, the circuit layer 12 can be polished and processed while being cooled, and both the emery paper and the circuit layer 12 can be prevented from burning.

In this embodiment, emery paper is used, but sand paper or the like may be used. Further, although wet polishing is used in the present embodiment, dry polishing may be used. That is, any method can be used as long as the amount of warpage of the mounting surface 122 can be reduced to 10 μm or less.

Then, the LED module 40 shown in FIG. 1 is obtained by mounting the LED element 30 on the mounting surface 122 of the insulating circuit board 1 with a heat sink manufactured by the manufacturing method described above.

In the present embodiment, the insulated circuit board 1 with a heatsink is formed by bonding the heatsink 20 to the insulated circuit board 10 by a bonding process, and then polishing the central portion of the convex surface 121 of the circuit layer 12 to obtain a flat mounting surface 122. is formed, the flatness of the mounting surface 122 of the circuit layer 12 on which the LED element 30 is mounted can be improved. Moreover, the flatness of the mounting surface 122 can be improved by a simple method of polishing the convex surface 121 of the circuit layer 12 . Moreover, even if the entire insulating circuit board 1 with a heat sink is warped in a convex shape, the flat mounting surface 122 is formed at least in the center of the convex surface 121 of the circuit layer 12, so that the LED element 30 can be properly mounted. can be used and is suitable for use.

In addition, detailed configurations are not limited to those of the embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the above-described embodiment, the LED element 30 is mounted on the mounting surface 122 of the circuit layer 12, but other electronic components may be mounted. That is, the present invention can be applied not only to LED modules but also to power modules and the like.

In the above embodiment, the insulating circuit board 10 is composed of the ceramic substrate 11, the circuit layer 12, and the metal layer 13, but the invention is not limited to this. For example, the circuit layer 12A includes, as shown in FIG. and a second circuit layer 15.

Although the insulated circuit board 10 is provided with the metal layer 13 in the above embodiment, it is not limited to this. For example, as shown in FIG. 4, the insulated circuit board 10 may not have the metal layer 13 . In this case, the heat sink 20 may be directly bonded to the surface of the ceramic substrate 11 opposite to the circuit layer 12 . Also, the heat sink 20 may have a plurality of pin-like fins protruding from the surface opposite to the insulating circuit board 10 .

As an insulating circuit board, a ceramic board made of aluminum nitride (AlN) and having a size of 20 mm x 20 mm in a plan view and a thickness of 0.635 mm was provided. A heat sink having an outer diameter of 50 mm×50 mm and a thickness of 5 mm was joined to the metal layer of the metal layer joined to manufacture an insulated circuit board with a heat sink. For joining these, the circuit layer, the ceramic substrate, and the metal layer are laminated via an Al-Si-Mg brazing material, and these are pressed in the lamination direction and heated to manufacture an insulated circuit board. A heat sink was laminated on this with an Al--Si--Mg brazing filler metal interposed therebetween, and these were bonded together by applying pressure and heating in the direction of lamination to produce an insulated circuit board with a heat sink. In Example 1, the central portion of the circuit layer was wet-polished with No. 1000 emery paper under a pressure of 0.5 N for 30 seconds to form a flat mounting surface of 13 mm×13 mm. An LED module was formed by mounting four LED light sources in the center of the mounting surface so as to form two vertical and two horizontal (2×2).

On the other hand, in Comparative Example 1, no treatment was applied to the circuit layer of the insulating circuit with a heat sink manufactured by the above method, and four single LED light sources were placed in the center of the circuit layer, two vertically and two horizontally (2 ×2) to form an LED module.
For the LED modules of Example 1 and Comparative Example 1 manufactured in this way, the ratio of the amount of light traveling straight to the total amount of light (light amount ratio) was evaluated.

(Warpage amount of circuit layer (mounting surface))
The amount of warpage of the mounting surface is obtained by measuring the mounting surface (13 mm × 13 mm) located inside the outer peripheral portion of the upper surface of the circuit layer, using Thermoire PS200 manufactured by AkroMetrix, and obtaining the least square surface from the profile of the measurement surface. Using the least squares surface as a reference, the difference between the highest point and the lowest point was measured as the amount of warpage.

(Light intensity ratio)
The light amount ratio is the ratio of the amount of light traveling straight to the total amount of light, and was measured using an illuminometer (LM331 manufactured by AS ONE). Specifically, the distance from the tip of the LED light source to the detection part of the illuminometer was set to 1000 mm, the diameter of the LED light source was set to 10 mm, and the diameter of the detection part was also set to 10 mm. Under this condition, the ratio of the amount of light traveling straight from the LED light source (light detected by the detection unit) to the total amount of light from the LED light source was calculated. Table 1 shows the results.

As is clear from Table 1, in Example 1 in which the central portion of the circuit layer was polished to form a flat mounting surface, the warpage amount of the mounting surface was as small as 5 μm, so the light intensity ratio was as high as 33.2%. . Also, in Example 2, although the amount of warp was larger than that in Example 1, it was as small as 10 μm, so the light amount ratio was as high as 20.6%. On the other hand, in Comparative Example 1 in which the circuit layer was not polished, the amount of warpage at the central portion of the circuit layer was as large as 30 μm, so the light amount ratio was as low as 12.1%. For this reason, it was found that by polishing the central portion of the circuit layer to form a flat mounting surface, the amount of warping of the mounting surface can be reduced, and it can be used appropriately as an LED module.

1 Insulated circuit board with heat sink 10 Insulated circuit board 11 Ceramics substrate 12 12A Circuit layer 121 Convex surface 122 Mounting surface 13 Metal layer 14 First circuit layer 15 Second circuit layer 20 Heat sink 30 LED element 40 LED module

Claims (2)

A heat sink is bonded to a surface opposite to the circuit layer of an insulating circuit board in which a circuit layer is bonded to one surface of a ceramic substrate, and the bonded insulating circuit board and the heat sink as a whole are placed on the circuit layer side. A joining step of warping in a convex shape ;
and a polishing step for forming a flat mounting surface by polishing a center portion located inside an outer peripheral portion of the convex surface of the circuit layer after the bonding step. Method. An insulated circuit board with a heat sink in which a circuit layer is formed on one side of a ceramic substrate and a heat sink is arranged on the side opposite to the circuit layer of the insulated circuit board,
The entire insulated circuit board with a heat sink has a shape protruding along the circuit layer side,
Further, the insulated circuit board with a heat sink is characterized in that a flat mounting surface is formed in the central portion located inside the outer peripheral portion of the convex surface of the circuit layer.

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