WO2017217236A1

WO2017217236A1 - Heat sink with circuit board and method for producing same

Info

Publication number: WO2017217236A1
Application number: PCT/JP2017/020317
Authority: WO
Inventors: 幹雄大高; 熊谷　正樹
Original assignee: 株式会社Uacj
Priority date: 2016-06-16
Filing date: 2017-05-31
Publication date: 2017-12-21
Also published as: JP2017224748A

Abstract

Provided are: a heat sink (1) with a circuit board, which is able to be suppressed in cracking of a ceramic plate (52) for a long period of time; and a method for producing this heat sink (1) with a circuit board. This heat sink (1) comprises a heat sink main body (2), a low expansion plate (3), an intermediate aluminum plate (4) and a circuit board (5). The heat sink main body (2) has a base part (21) that is in the form of a flat plate. The low expansion plate (3), which has a lower linear expansion coefficient than the heat sink main body (2), the intermediate aluminum plate (4) and the circuit board (5) are laminated on the base part (21) with brazing filler material layers being respectively interposed therebetween. The circuit board (5) comprises: a backside metal layer (51) that is laminated on the intermediate aluminum plate (4) with a brazing filler material layer being interposed therebetween; a ceramic plate (52) that is laminated on the backside metal layer (51); and a circuit metal layer (53) that is laminated on the ceramic plate (52).

Description

Heat sink with circuit board and manufacturing method thereof

The present invention relates to a heat sink with a circuit board and a manufacturing method thereof.

Power converters such as inverters and converters incorporate a heat sink with a circuit board having a circuit board in which metal plates are bonded to both surfaces of a ceramic plate and a heat sink bonded to one metal plate in the circuit board. (For example, patent document 1). On the other metal plate of the circuit board, a semiconductor element constituting the power circuit is mounted by soldering. In addition, the heat sink and the metal plate in this type of heat sink with a circuit board may be made of an aluminum material (including aluminum and an aluminum alloy; the same shall apply hereinafter) for the purpose of weight reduction.

The circuit board is bonded to the heat sink by the following method. First, an object to be processed is assembled by laminating a heat sink, a brazing material, and a circuit board in this order. Then, the workpiece is heated while pressing the circuit board toward the heat sink, and the brazing material is melted. Thereafter, by cooling the workpiece and solidifying the brazing material, the metal plate and the heat sink on the circuit board can be joined via the brazing material.

Japanese Patent Laying-Open No. 2015-153925

However, since the thermal expansion coefficient of the ceramic plate in the circuit board is different from the thermal expansion coefficient of the aluminum material constituting the heat sink, a difference occurs in the thermal expansion amount between the ceramic plate and the heat sink due to heating during brazing. When the object to be processed is cooled in such a state, the brazing material is solidified before the contraction of the ceramic plate and the heat sink is completed. As a result, in the heat sink with a circuit board after brazing is completed, warpage and residual stress are generated in the ceramic plate.

Moreover, the circuit board after brazing is restrained by the heat sink through the brazing material. Therefore, for example, when soldering the semiconductor element or when the temperature of the circuit board and the heat sink rises due to heat generation of the semiconductor element, a tensile stress is generated near the center of the ceramic plate and the ceramic plate is warped. And when these tensile stress and curvature are too large, there exists a possibility that a crack may generate | occur | produce in a ceramic board.

The present invention has been made in view of such a background, and an object of the present invention is to provide a heat sink with a circuit board capable of suppressing cracking of a ceramic plate over a long period of time and a method for manufacturing the same.

One aspect of the present invention includes a base portion having a flat plate shape, a heat sink body made of an aluminum material,
A low expansion plate having a linear expansion coefficient lower than that of the heat sink body, and disposed on the base portion;
An intermediate aluminum plate disposed on the low expansion plate;
A circuit board disposed on the intermediate aluminum plate;
A brazing material layer interposed between the base portion and the low expansion plate, between the low expansion plate and the intermediate aluminum plate, and between the intermediate aluminum plate and the circuit board;
The circuit board is
A back metal layer made of an aluminum material and laminated on the intermediate aluminum plate via the brazing material layer;
A ceramic plate laminated on the back metal layer;
A heat sink with a circuit board, comprising a circuit metal layer made of an aluminum material and laminated on the ceramic plate.

Another aspect of the present invention is a method of manufacturing a heat sink with a circuit board according to the above aspect,
A lower wax foil placed on the base portion, the low expansion plate placed on the lower wax foil, an intermediate wax foil placed on the low expansion plate, and the intermediate wax The intermediate aluminum plate placed on the foil, the upper brazing foil placed on the intermediate aluminum plate, and the circuit board placed so that the upper brazing foil and the back metal layer are in contact with each other Assembling the workpiece having
In the method for manufacturing a heat sink with a circuit board, the object to be processed is collectively brazed by heating the object to be processed while pressing the circuit board toward the base part.

The low expansion plate, the intermediate aluminum plate, the back metal layer, the ceramic plate, and the circuit metal layer are sequentially laminated on the base portion of the heat sink with a circuit board (hereinafter referred to as “heat sink”). Yes. That is, in the heat sink, the base portion made of aluminum material and the circuit metal layer are arranged on the outermost side in the laminated structure described above, and the low expansion coefficient is lower on the inner side than the aluminum material. A plate and the ceramic plate are arranged. An intermediate aluminum plate made of an aluminum material and a back metal layer are disposed between the low expansion plate and the ceramic plate.

In this way, in a laminated structure in which a layer made of an aluminum material and a layer made of a material having a lower linear expansion coefficient than that of the aluminum material are arranged symmetrically, warping that occurs in the ceramic plate at the time of brazing, etc. The direction is the direction opposite to the direction of warpage occurring in the low expansion plate. As a result of canceling out the warpage of both, the warpage of the ceramic plate during brazing can be reduced, and the warpage of the ceramic plate caused by a temperature change after brazing can be reduced. As a result, cracking of the ceramic plate can be suppressed over a long period of time.

Further, in the manufacturing method of the above aspect, the above-described components are arranged inside the outer frame portion and the workpiece is assembled, and then brazed together. Thereby, the said heat sink can be produced easily.

It is a top view of the heat sink with a circuit board in an Example. FIG. 2 is a cross-sectional view taken along line II-II in FIG. It is a partially expanded sectional view of the outer periphery edge vicinity of the low expansion board in the test body F2 of Example 6. FIG.

In the above heat sink, the heat sink body has a flat base portion. On one side of the base portion in the thickness direction, a low expansion plate is laminated via a brazing material layer. Further, a heat radiating fin such as a pin fin, a plate fin, or a corrugated fin, which is configured separately from the heat sink main body, may be attached to the other side in the thickness direction of the base portion. These heat radiation fins can also be formed integrally with the heat sink body.

The thickness of the base part is preferably 0.5 to 1.5 times the thickness of the circuit metal layer. In this way, by making the thickness of the circuit metal layer and the thickness of the base portion approximately the same, the warpage occurring in the ceramic plate and the warpage occurring in the low expansion plate can be more effectively offset. As a result, the warpage of the ceramic plate can be more effectively reduced.

In order to more effectively reduce the warpage of the ceramic plate, it is preferable to bring the thickness of the base portion close to the thickness of the circuit metal layer. From this point of view, the thickness of the base portion is more preferably 1.0 to 1.5 times the thickness of the circuit metal layer, and further preferably 1.0 to 1.2 times.

Further, the heat sink main body may further have an outer frame portion standing from the outer peripheral edge of the base portion and disposed around the low expansion plate, the intermediate aluminum plate, and the circuit board. The outer frame portion can easily suppress displacement of the low expansion plate, the intermediate aluminum plate, and the circuit board during brazing. In addition, the molten wax can be held inside the outer frame portion during brazing. As a result, the above-described component parts can be brazed more reliably.

The height of the outer frame portion is preferably 0.9 to 1.1 times the height of the circuit metal layer. By setting the height of the outer frame portion within the specific range, brazing can be performed more easily when the heat sink is manufactured. In addition, the workability in the work of mounting a semiconductor element or the like on the circuit board can be further improved. Here, the height of the outer frame portion and the height of the circuit metal layer are heights measured with reference to the back surface of the plate surface on which the low expansion plate is disposed in the base portion.

When the height of the outer frame portion is less than 0.9 times the height of the circuit metal layer, the position of the circuit board or the like is likely to shift during brazing, and the solder flows out of the outer frame portion. , Etc. may occur. When the height of the outer frame portion exceeds 1.1 times the height of the circuit metal layer, there is a risk of increasing the mass of the heat sink body. In this case, in the work of mounting a semiconductor element or the like on the circuit board, workability may be reduced due to the presence of the outer frame portion.

The material of the heat sink body can be appropriately selected from known aluminum and aluminum alloys according to required mechanical properties, corrosion resistance, workability, and the like.

For example, the heat sink body may be made of a 6000 series aluminum alloy. The 6000 series aluminum alloy has a high creep strength. Therefore, in this case, creep deformation of the heat sink body can be further suppressed. As a result, a change in the shape of the heat sink can be suppressed more effectively, and as a result, the reliability of the heat sink can be further improved.

The low expansion plate is laminated on the base part and joined to the base part via a brazing material layer. The thickness of the low expansion plate is preferably 0.4 to 3.5 times the thickness of the ceramic plate. Thus, by making the thickness of the ceramic plate and the thickness of the low expansion plate approximately the same, it is possible to more effectively offset the warpage generated in the ceramic plate and the warp generated in the low expansion plate. As a result, the warp of the ceramic plate can be effectively reduced.

In order to more effectively reduce the warpage of the ceramic plate, it is preferable to bring the thickness of the low expansion plate close to the thickness of the ceramic plate. From this viewpoint, the thickness of the low expansion plate is more preferably 0.4 to 2.5 times the thickness of the ceramic plate, and further preferably 0.5 to 2.0 times.

The linear expansion coefficient of the low expansion plate and the ceramic plate is preferably 2 to 10 ppm / K. In this case, since the linear expansion coefficient of the low expansion plate is approximately the same as the linear expansion coefficient of the ceramic plate of the circuit board, the warpage generated in the ceramic plate and the warpage generated in the low expansion plate can be effectively offset. Can do. As a result, the warpage of the ceramic plate can be effectively reduced and cracking of the ceramic plate can be suppressed over a long period of time. From the viewpoint of suppressing cracking of the ceramic plate for a longer period, the linear expansion coefficient of the low expansion plate and the ceramic plate is more preferably 2 to 9 ppm / K, and further preferably 3 to 8 ppm / K. preferable.

Examples of the material having a linear expansion coefficient in the specific range include metals such as tungsten (W), tungsten alloy, molybdenum (Mo), molybdenum alloy, and iron (Fe) -nickel (Ni) 36% alloy; alumina ( Ceramics such as Al ₂ O ₃ ), aluminum nitride (AlN), and silicon nitride (Si ₃ N ₄ ); laminated material in which a metal plate with a low linear expansion coefficient such as tungsten and molybdenum and a copper plate are laminated; diamond dispersed composite copper A composite material such as a material or a ceramic dispersed copper material can be employed.

The linear expansion coefficient of the low expansion plate is more preferably 0.5 to 2.5 times the linear expansion coefficient of the ceramic plate. In this case, stress and warpage generated in the ceramic plate during and after brazing can be more effectively offset. As a result, cracking of the ceramic plate can be suppressed over a longer period.

In order to more effectively reduce the warpage of the ceramic plate, it is preferable to bring the linear expansion coefficient of the low expansion plate closer to the linear expansion coefficient of the ceramic plate. From this point of view, the linear expansion coefficient of the low expansion plate is more preferably 0.5 to 2.0 times, more preferably 0.7 to 2.0 times the linear expansion coefficient of the ceramic plate, A ratio of 0.75 to 1.5 times is particularly preferable.

The low expansion plate is preferably made of metal. Metals have higher toughness than ceramics. Therefore, the low expansion plate made of metal can easily follow the deformation of the heat sink body when the heat sink body is thermally expanded.

The shape of the low expansion plate is not particularly limited as long as it is a shape that can be arranged inside the outer frame portion. For example, the low expansion plate may have a square shape or a rectangular shape. In this case, in a plan view as viewed from the thickness direction of the low expansion plate, the corner portion can be rounded so that the corner portion at the outer peripheral edge of the low expansion plate has an arc shape. In this case, stress concentration at the corners of the ceramic plate that occurs during and after brazing can be more effectively mitigated. As a result, cracking of the ceramic plate can be suppressed over a longer period.

Further, the low expansion plate may have a lattice structure. In this case, the low expansion plate can be further reduced in weight, and thus the heat sink can be further reduced in weight.

The intermediate aluminum plate is laminated on the low expansion plate via a brazing material layer. The intermediate aluminum plate may be made of aluminum having a purity of 99.0 to 99.85%, for example. By setting the purity of the low expansion plate to 99.0% or more, the thermal conductivity of the intermediate aluminum plate can be further increased. As a result, the cooling performance of the heat sink can be further improved. On the other hand, when the purity of the low expansion plate becomes excessively high, the material cost increases. By setting the purity of the low expansion plate to 99.85% or less, an increase in material cost can be avoided.

Further, the intermediate aluminum plate may be made of a 6000 series aluminum alloy. The 6000 series aluminum alloy has a high creep strength. Therefore, in this case, creep deformation of the intermediate aluminum plate due to stress received from the ceramic substrate can be more effectively suppressed. As a result, a change in the shape of the heat sink can be suppressed more effectively, and as a result, the reliability of the heat sink can be further improved.

On the intermediate aluminum plate, a circuit board is laminated via a brazing material layer. The circuit board has a three-layer structure in which a circuit metal layer, a ceramic plate, and a back metal layer are sequentially laminated. As the circuit metal layer and the back surface metal layer, a plate material made of known aluminum or aluminum alloy can be employed.

The thickness of the circuit metal layer and the thickness of the back surface metal layer may be the same or different. The thickness of the circuit metal layer and the thickness of the back metal layer are preferably in the range of 0.1 to 1.0 mm. By setting these thicknesses to 0.1 mm or more, the heat of the heating element mounted on the circuit board can be efficiently diffused. As a result, the cooling performance of the heat sink can be further improved. On the other hand, when these thicknesses are excessively large, there is a risk of dimensional accuracy being lowered. From the viewpoint of avoiding a decrease in dimensional accuracy, the thickness of the circuit metal layer and the thickness of the back surface metal layer are preferably 1.0 mm or less.

The ceramic plate is made of a ceramic material having a linear expansion coefficient of 2 to 10 ppm / K. Specifically, oxide ceramics such as alumina, and nitride ceramics such as aluminum nitride and silicon nitride can be employed as the material of the ceramic plate.

The outer peripheral edge of the intermediate aluminum plate extends outward from the outer peripheral edge of the back metal layer and protrudes toward the circuit board side, and the outer peripheral edge of the low expansion plate is the intermediate aluminum plate The outer peripheral edge may extend outward and may protrude toward the circuit board. In this case, the heat sink can be manufactured more easily.

That is, in manufacturing the heat sink, first, the above-described components are prepared by a conventional method. Here, in preparing the low expansion plate and the intermediate aluminum plate, press punching processing or shear cutting processing may be performed on these base plates so as to have a predetermined dimension. While these processes have the advantages of high productivity and low processing costs, burrs are generated at the outer peripheral edges of the low expansion plate and the intermediate aluminum plate after processing. Such burrs may cause troubles in manufacturing or quality in subsequent processes. However, when processing for removing burrs is added, there is a possibility that advantages in terms of productivity and processing cost are impaired.

In order to avoid these problems, the outer peripheral edge of the intermediate aluminum plate extends outward from the outer peripheral edge of the back metal layer, and the outer peripheral edge of the low expansion plate is the outer peripheral edge of the intermediate aluminum plate. What is necessary is just to produce a low expansion board and an intermediate | middle aluminum board so that it may extend outside rather than. Thereby, the burr | flash of a low expansion board and an intermediate | middle aluminum board can be made to project to the circuit board side in the lamination direction of a base part and a circuit board, without contacting with the material laminated | stacked on these. As a result, it is possible to obtain an advantage of press punching or the like while avoiding problems in manufacturing or quality due to burrs.

In this case, the gap between the low expansion plate and the intermediate aluminum plate and the gap between the intermediate aluminum plate and the back metal layer can be reduced. As a result, the effect of further improving the cooling performance can be expected.

In order to sufficiently obtain the above effect, the protrusion amount of the outer peripheral edge of the low expansion plate, that is, the distance from the outer peripheral edge of the intermediate aluminum plate to the outer peripheral edge of the low expansion plate is 0.1 mm or more. I just need it. Similarly, the protrusion amount of the outer peripheral edge of the intermediate aluminum plate, that is, the distance from the outer peripheral edge of the back metal layer to the outer peripheral edge of the intermediate aluminum plate may be 0.1 mm or more.

The upper limit of these protrusion amounts is not particularly limited, but it is preferable that the protrusion amount is 4.0 mm or less from the viewpoint of miniaturization of the heat sink.

Examples of the heat sink with the circuit board will be described below. In addition, the aspect of the heat sink with a circuit board of this invention and its manufacturing method is not limited to the following aspects, A structure can be changed suitably in the range which does not impair the meaning of this invention.

Example 1
As shown in FIGS. 1 and 2, the heat sink 1 of this example includes a heat sink body 2, a low expansion plate 3, an intermediate aluminum plate 4, and a circuit board 5. As shown in FIG. 2, the heat sink body 2 is made of an aluminum material, and has a base portion 21 that has a flat plate shape. The low expansion plate 3 has a lower linear expansion coefficient than the heat sink main body 2 and is disposed on the base portion 21. The intermediate aluminum plate 4 is disposed on the low expansion plate 3. The circuit board 5 is disposed on the intermediate aluminum plate 4.

A brazing material layer (not shown) is interposed between the base portion 21 and the low expansion plate 3, between the low expansion plate 3 and the intermediate aluminum plate 4, and between the intermediate aluminum plate 4 and the circuit board 5. Yes. The circuit board 5 is made of an aluminum material, and is made of a back metal layer 51 laminated on the intermediate aluminum plate 4 via a brazing material layer, a ceramic plate 52 laminated on the back metal layer 51, and an aluminum material, And a circuit metal layer 53 laminated on the ceramic plate 52.

As shown in FIGS. 1 and 2, the heat sink body 2 of the present example includes a base portion 21, an outer frame portion 22, and heat radiating fins 23. As shown in FIG. 1, the heat sink body 2 has a rectangular shape in a plan view when viewed from the thickness direction of the base portion 21. In the heat sink main body 2 of this example, the dimension in the vertical direction (long side direction) is 110 mm, and the dimension in the horizontal direction (short side direction) is 90 mm. Moreover, the thickness of the base part 21 of this example is 0.4 mm. The heat sink body 2 of this example is made of JIS A3003 alloy.

As shown in FIG. 2, the low expansion plate 3 is laminated on one plate surface 211 of the base portion 21 via a brazing material layer (not shown). In addition, a large number of radiating fins 23 are provided upright on the other plate surface of the base portion 21, that is, the back surface 212 of the plate surface 211 on which the low expansion plate 3 is laminated. The radiating fin 23 of this example has a cylindrical shape with a diameter of 1.5 mm and a height of 10 mm. Moreover, the radiation fin 23 is arrange | positioned in the square area | region of 75 mm in one side in the planar view seen from the thickness direction of the base part 21. FIG.

The outer frame portion 22 is erected on the outer peripheral edge portion 213 of the base portion 21, and is disposed around the low expansion plate 3, the intermediate aluminum plate 4, and the circuit board 5 as shown in FIGS. 1 and 2. Yes. Also, between these members and the outer frame portion 22, as shown in FIG. 2, between the base portion 21 and the low expansion plate 3 and between the low expansion plate 3 and the intermediate aluminum plate 4 during brazing. And the brazing material 11 which flowed out between the intermediate aluminum plate 4 and the back surface metal layer 51 is held.

In this example, the height H1 of the outer frame portion 22 with respect to the back surface 212 of the base portion 21 is 1.0 times the height H2 of the circuit metal layer 53. Specifically, the height H1 of the outer frame portion 22 and the height H2 of the circuit metal layer 53 in the heat sink 1 of this example are both 3.0 mm.

As shown in FIG. 2, the low expansion plate 3 is laminated on the base portion 21 via a brazing material layer (not shown). The low expansion plate 3 of this example is a nickel plate having a thickness of 0.64 mm. The typical linear expansion coefficient of nickel is 13.3 ppm / K, which is lower than the typical linear expansion coefficient of aluminum material (23 to 24 ppm / K).

On the low expansion plate 3, an intermediate aluminum plate 4 is laminated via a brazing material layer (not shown).

On the intermediate aluminum plate 4, a back metal layer 51 of the circuit board 5 is laminated via a brazing material layer (not shown). In the circuit board 5 of this example, a 0.4 mm-thick back metal layer 51 made of an aluminum material, a 0.32 mm-thick ceramic plate 52 made of aluminum nitride, and a 0.4 mm-thick circuit metal layer 53 made of an aluminum material are sequentially formed. It has a stacked three-layer structure.

In this example, as shown in Table 1, any one of JIS A3003 alloy plate, pure aluminum plate (purity 99.50%) and JIS A6063 alloy plate is used as intermediate aluminum plate 4, and three types of heat sinks 1 (test Body A1 to A3) were produced. The test specimen was produced by the following method.

First, the A3003 alloy plate was forged and the radiating fins 23 were erected. Next, the plate surface opposite to the surface on which the heat radiating fins 23 were erected was cut to form a recess having a depth of 2.6 mm, and the heat sink body 2 was produced. Moreover, the low expansion plate 3 was produced by cutting a nickel plate having a thickness of 0.64 mm into the same dimensions as the back surface metal layer 51.

An intermediate aluminum plate 4 was produced by cutting an A3003 alloy plate, a pure aluminum plate and an A6063 alloy plate having a thickness of 0.82 mm into the same dimensions as the low expansion plate 3. A commercially available product was used for the circuit board 5. In addition, a 0.1 mm thick brazing foil made of an Al—Si (aluminum-silicon) alloy was cut into the same dimensions as the low expansion plate 3 to prepare an upper brazing foil, an intermediate brazing foil, and a lower brazing foil.

After preparing these members, the lower brazing foil, the low expansion plate 3, the intermediate brazing foil, the intermediate aluminum plate 4, the upper brazing foil, and the circuit board 5 are placed on the base portion 21 in this order, and the workpiece Assembled. A jig was attached to the object to be processed, and the object to be processed was heated to 600 ° C. in a nitrogen gas atmosphere in a state where the circuit board 5 was pressed to the base portion 21 side, and brazing was performed. Specimens A1 to A3 were produced as described above.

Further, in this example, for comparison with the test bodies A1 to A3, the test body R in which the circuit board 5 was directly brazed on the base portion 21 was produced. The test body R has the same configuration as the test bodies A1 to A3 except that the low expansion plate 3 and the intermediate aluminum plate 4 are not provided.

These test bodies A1 to A3 and test body R were evaluated for warpage of the circuit board 5 after brazing, warpage of the circuit board 5 during soldering, cooling performance and durability.

-Warping of the circuit board 5 after brazing After removing the test body after brazing from the jig, the difference in height between the central part and the outer peripheral end of the circuit board 5 is measured. The amount of warpage. The circuit board 5 after brazing was curved so that the circuit board 5 side in the stacking direction of the base portion 21 and the circuit board 5 was convex. The warping amount of the circuit board 5 after brazing was as shown in Table 1.

-Warpage of the circuit board 5 at the time of soldering Assuming the soldering work to the circuit board 5, the amount of warpage of the circuit board 5 in a state where the test body was heated to 270 ° C was measured. In the state heated to 270 ° C., the direction of warping of the circuit board 5 is opposite to that before heating, and the base part 21 side in the stacking direction of the base part 21 and the circuit board 5 is curved to be convex. It was. The amount of warping of the circuit board 5 in this state was as shown in Table 1.

-Cooling performance A water cooling jacket was attached to the side of the radiating fin 23 of each specimen, and a coolant was allowed to flow at a constant flow rate in the water cooling jacket. Then, a heating element was placed on the circuit metal layer 53 to generate heat with a constant output. In addition, LLC (Long-Life Coolant) 50% was used as a refrigerant | coolant, and the flow volume was 12 L / min. The heating value of the heating element was 800W.

This state was maintained, and the temperature of the heating element when the steady state was reached was measured. Then, assuming that the temperature of the heating element in the test body R is Tr (K) and the temperature of the heating element in the test bodies A1 to A3 is Ts (K), the rate of decrease in cooling performance R (%) is calculated by the following equation. . The reduction rate R of the cooling performance was as shown in Table 1.
R = (Ts−Tr) / Tr × 100

Durability Using a temperature cycle tester, a temperature cycle test was conducted by repeating 1000 cycles of a heating step of holding at 150 ° C. for 30 minutes and a cooling step of holding at −50 ° C. for 30 minutes. The amount of warpage of the circuit board 5 after the temperature cycle test was measured, and the change from the amount of warpage of the circuit board 5 before the temperature cycle test was calculated. The change in the warpage amount by the temperature cycle test was as shown in Table 1.

As can be understood from Table 1, specimens A1 to A3 having a laminated structure in which a layer made of an aluminum material and a layer made of a material having a lower linear expansion coefficient than the aluminum material are arranged symmetrically are brazed. The amount of subsequent warping was small, and cracking of the ceramic plate 52 did not occur when heated to 270 ° C. Moreover, since the test body A3 used the A6063 alloy plate with high material strength as the intermediate aluminum plate 4, the change in the amount of warpage after the temperature cycle test was small, and particularly excellent durability was exhibited.

On the other hand, since the test body R does not have the low expansion plate 3, the ceramic plate 52 was cracked when heated to 270 ° C.

(Example 2)
In this example, the material of the ceramic plate 52 is variously changed. Of the reference numerals used in and after the present embodiment, the same reference numerals as those used in the above-described embodiments represent the same constituent elements as those in the above-described embodiments unless otherwise specified.

In this example, specimens B1 to B10 were produced in the same manner as in Example 1 except that the configurations of the low expansion plate 3, the intermediate aluminum plate 4 and the ceramic plate 52 were changed as shown in Table 2. In Table 2, as the linear expansion coefficient of the low expansion plate 3, the magnification when the linear expansion coefficient of the ceramic plate 52 is set to 1 is described together with the value.

Then, these specimens were evaluated by the same procedure as in Example 1. The evaluation results are as shown in Table 3.

As can be understood from Tables 2 and 3, the test bodies B1 to B10 employ molybdenum having a higher thermal conductivity than nickel as the low expansion plate 3, and therefore, compared to the test bodies A1 to A3 (see Table 1). Cooling performance improved.

Of these specimens, the specimens B1 to B3 and B6 to B8 have a linear expansion coefficient of the low expansion plate 3 that is 0.7 to 2.0 times the linear expansion coefficient of the ceramic plate 52. Therefore, the amount of warping of the circuit board 5 during soldering can be reduced as compared with the specimens A1 (see Table 1), B4, and the like in which the linear expansion coefficient of the low expansion plate 3 is outside the above range.

(Example 3)
In this example, the thickness of the low expansion plate 3 is variously changed. In this example, the height H1 of the outer frame portion 22 in the heat sink body 2 is changed to 3.5 mm, and the configurations of the low expansion plate 3, the intermediate aluminum plate 4 and the ceramic plate 52 are changed as shown in Table 4. Prepared specimens C1 to C5 in the same manner as in Example 1. In Table 4, as the thickness of the low expansion plate 3, along with the value, the magnification when the thickness of the ceramic plate 52 is set to 1 is described. The thickness of the intermediate aluminum plate 4 is adjusted so that the height H2 of the circuit metal layer 53 is 3.5 mm.

These specimens were evaluated by the same procedure as in Example 1. The evaluation results are as shown in Table 5.

In the test bodies C1 to C5, since the linear expansion coefficient of the low expansion plate 3 is 0.7 to 2.0 times the linear expansion coefficient of the ceramic plate 52, the amount of warping at the time of soldering is determined by the test bodies B1 to B10 ( (See Table 3).

Further, as shown in Tables 4 and 5, in the test bodies C1, C2, and C4, the thickness of the low expansion plate 3 is 0.5 to 2.0 times the thickness of the ceramic plate 52. Therefore, these specimens were able to further reduce the amount of warping of the circuit board 5 than the specimen C3 or the like in which the thickness of the ceramic plate 52 was outside the above range.

Example 4
In this example, the thickness of the base portion 21 is variously changed. In this example, a molybdenum plate having a thickness of 1.0 mm (linear expansion coefficient 5.0 ppm / K) as the low expansion plate 3 and an aluminum nitride plate having a thickness of 0.64 mm (linear expansion coefficient 4.5 ppm / K) as the ceramic plate 52. Specimens D1 to D5 were produced in the same manner as in Example 1 except that the structure of the heat sink body 2 and the intermediate aluminum plate 4 was changed as shown in Table 6. In Table 6, as the thickness of the base portion 21, the value when the thickness of the circuit metal layer 53 is set to 1 is described together with the thickness. The thickness of the intermediate aluminum plate 4 is adjusted so that the height H2 of the circuit metal layer 53 is 3.5 mm.

These specimens were evaluated by the same procedure as in Example 1. The evaluation results are as shown in Table 7.

In the test bodies D1 to D5, the linear expansion coefficient of the low expansion plate 3 is 0.7 to 2.0 times the linear expansion coefficient of the ceramic plate 52. 3)).

Also, as shown in Tables 6 and 7, in the test bodies D2 to D4, the thickness of the base portion 21 is 1.0 to 1.5 times the thickness of the circuit metal layer 53. Therefore, these test bodies were able to further reduce the amount of warping of the circuit board 5 than the test bodies D1 and the like in which the thickness of the base portion 21 was outside the above range.

(Example 5)
In this example, the height H2 of the circuit metal layer 53 is changed. In this example, a molybdenum plate having a thickness of 1.0 mm (linear expansion coefficient 5.0 ppm / K) as the low expansion plate 3 and an aluminum nitride plate having a thickness of 0.64 mm (linear expansion coefficient 4.5 ppm / K) as the ceramic plate 52. Specimens E1 to E2 were produced in the same manner as in Example 1 except that the structure of the heat sink body 2 and the intermediate aluminum plate 4 was changed as shown in Table 8. In Table 8, as the height H1 of the outer frame portion 22, the value and the magnification when the height H2 of the circuit metal layer 53 is set to 1 are described.

These specimens were evaluated by the same procedure as in Example 1. The evaluation results are as shown in Table 9.

The test bodies E1 to E2 were able to be brazed more easily because the height H1 of the outer frame portion 22 was 0.9 to 1.1 times the height H2 of the circuit metal layer 53.

(Example 6)
In this example, the influence of the

burrs

31 and 41 of the low expansion plate 306 and the intermediate aluminum plate 406 is evaluated. In this example, specimens F1 and F2 were produced as follows.

First, a plate of A6063 alloy is forged to radiate fins 23, and then a plate surface opposite to the surface where radiating fins 23 are erected is cut to form a recess having a depth of 2.6 mm. By forming, the heat sink main body 2 was produced. Next, press punching is performed on a pure aluminum plate having a thickness of 0.82 mm to produce

intermediate aluminum plates

4 and 406, and press-punching is performed on a molybdenum plate having a thickness of 1.0 mm to form

low expansion plates

3 and 306. Produced.

At this time, the intermediate aluminum plate 4 and the low expansion plate 3 used for the specimen F1 were subjected to press punching so as to have the same dimensions as the back surface metal layer 51. On the other hand, about the intermediate | middle aluminum plate 406 used for the test body F2, the press punching process was performed so that a dimension might become slightly larger than the back surface metal layer 51. FIG. The low expansion plate 306 used for the test body F2 was subjected to press punching so that the size was slightly larger than that of the intermediate aluminum plate 406.

A commercially available product was used as the circuit board 5. Further, a 0.1 mm thick brazing foil made of an Al—Si (aluminum-silicon) alloy was cut into the same dimensions as the

low expansion plates

3, 306 to prepare an upper brazing foil, an intermediate brazing foil, and a lower brazing foil. .

For the test body F1, the lower brazing foil, the low expansion plate 3, the intermediate brazing foil, the intermediate aluminum plate 4, the upper brazing foil, and the circuit board 5 are placed in this order on the base portion 21, and the workpiece is assembled. It was. On the other hand, for the test body F2, as shown in FIG. 3, the

burrs

31 and 41 formed in the press punching process protrude toward the circuit board 5 side in the stacking direction of the base portion 21 and the circuit board 5. As a result, the workpiece was assembled.

Thereafter, brazing was performed in the same manner as in Example 1 to prepare specimens F1 and F2.

In the specimen F2 after brazing, as shown in FIG. 3, the outer peripheral edge 411 of the intermediate aluminum plate 406 extends outward from the outer peripheral edge 511 of the back surface metal layer 51, and on the circuit board 5 side. It was protruding. Further, the outer peripheral edge 311 of the low expansion plate 306 extended outward from the outer peripheral edge 411 of the intermediate aluminum plate 406 and protruded toward the circuit board 5 side. More specifically, the outer peripheral edge 411 of the intermediate aluminum plate 406 extended 0.1 mm outward from the outer peripheral edge 511 of the back surface metal layer 51. Further, the outer peripheral edge 311 of the low expansion plate 306 extended outward by 0.1 mm from the outer peripheral edge 411 of the intermediate aluminum plate 406.

Evaluation was performed in the same manner as in Example 1 using the specimens F1 and F2 obtained as described above. The evaluation results were as shown in Table 10.

As shown in Table 10, in the test bodies F1 and F2, the linear expansion coefficient of the low expansion plate 3 is 0.7 to 2.0 times the linear expansion coefficient of the ceramic plate 52. Was able to be suppressed to be equal to or higher than that of the test specimens B1 to B10 (see Table 3). Further, as shown in FIG. 3, the test body F <b> 2 includes the base portion 21 and the circuit board without the

burrs

31 and 41 of the low expansion plate 306 and the intermediate aluminum plate 406 being in contact with the material laminated thereon. 5 protrudes toward the circuit board 5 in the stacking direction. Therefore, compared with the test body F1, the gap between the low expansion plate 306 and the intermediate aluminum plate 406 and the gap between the intermediate aluminum plate 406 and the back surface metal layer 51 could be reduced. As a result of the above, it is considered that the specimen F2 was able to improve the cooling performance as compared with the specimen F1.

Claims

A heat sink body made of an aluminum material, including a base portion having a flat plate shape,
A low expansion plate having a linear expansion coefficient lower than that of the heat sink body, and disposed on the base portion;
An intermediate aluminum plate disposed on the low expansion plate;
A circuit board disposed on the intermediate aluminum plate;
A brazing material layer interposed between the base portion and the low expansion plate, between the low expansion plate and the intermediate aluminum plate, and between the intermediate aluminum plate and the circuit board;
The circuit board is
A back metal layer made of an aluminum material and laminated on the intermediate aluminum plate via the brazing material layer;
A ceramic plate laminated on the back metal layer;
A heat sink with a circuit board, comprising a circuit metal layer made of an aluminum material and laminated on the ceramic plate.
2. The heat sink with a circuit board according to claim 1, wherein the intermediate aluminum plate is made of aluminum having a purity of 99.0 to 99.85%.
2. The heat sink with a circuit board according to claim 1, wherein the intermediate aluminum plate is made of a 6000 series aluminum alloy.
The heat sink with a circuit board according to any one of claims 1 to 3, wherein the thickness of the low expansion plate is 0.4 to 3.5 times the thickness of the ceramic plate.
The heat sink with a circuit board according to any one of claims 1 to 4, wherein a linear expansion coefficient of the low expansion plate is 0.5 to 2.5 times a linear expansion coefficient of the ceramic plate.
The heat sink with a circuit board according to any one of claims 1 to 5, wherein the thickness of the base portion is 0.5 to 1.5 times the thickness of the circuit metal layer.
The circuit board heat sink according to any one of claims 1 to 6, wherein the heat sink body is made of a 6000 series aluminum alloy.
The heat sink body further includes an outer frame portion that is erected from an outer peripheral edge of the base portion and is arranged around the low expansion plate, the intermediate aluminum plate, and the circuit board. The height of the outer frame portion is 0.9 to 1.1 times the height of the circuit metal layer when the back surface of the plate surface on which the low expansion plate is disposed is used as a reference. Item 8. The heat sink with a circuit board according to any one of Items 1 to 7.
The outer peripheral edge of the intermediate aluminum plate extends outward from the outer peripheral edge of the back metal layer and protrudes toward the circuit board side, and the outer peripheral edge of the low expansion plate is the intermediate aluminum plate The heat sink with a circuit board according to any one of claims 1 to 8, wherein the heat sink extends outward from an outer peripheral edge of the circuit board and protrudes toward the circuit board.
A method for manufacturing a heat sink with a circuit board according to any one of claims 1 to 9,
A lower wax foil placed on the base portion, the low expansion plate placed on the lower wax foil, an intermediate wax foil placed on the low expansion plate, and the intermediate wax The intermediate aluminum plate placed on the foil, the upper brazing foil placed on the intermediate aluminum plate, and the circuit board placed so that the upper brazing foil and the back metal layer are in contact with each other Assembling the workpiece having
A method of manufacturing a heat sink with a circuit board, wherein the object to be processed is heated in a lump by heating the object to be processed while pressing the circuit board toward the base part.