JP2018056275A - Circuit board-attached heat sink and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a circuit board-attached heat sink by which the cracking of a ceramic plate can be suppressed over a long period of time; and a method for manufacturing the circuit board-attached heat sink.SOLUTION: A circuit board-attached heat sink 1 comprises: a heat sink main body 2; a low-expansion plate 3; an intermediate plate 4; and a circuit board 5. The low-expansion plate 3 has a linear expansion coefficient lower than that of a copper material, and is bonded to a base part 21 of the heat sink main body 2. The intermediate plate 4 is bonded to the low-expansion plate 3. The circuit board 5 is disposed on the intermediate plate 4. The circuit board 5 has: a backside metal layer 51 bonded to the intermediate plate 4; a ceramic plate 52 laminated on the backside metal layer 51; and a circuit metal layer 53 laminated on the ceramic plate 52. A bonding portion of the base part 21 and low-expansion plate 3, a bonding portion of the low-expansion plate 3 and intermediate plate 4, and a bonding portion of the intermediate plate 4 and backside metal layer 51 have respective diffusion layers 20, 30 and 40 each including an element constituting a bonded member.SELECTED DRAWING: Figure 2

Description

  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. . On the other metal plate of the circuit board, a semiconductor element constituting the power circuit is mounted by soldering. As these metal plates, copper materials (including the same and copper alloys; the same shall apply hereinafter) are frequently used. The heat sink may be made of an aluminum material (including aluminum and an aluminum alloy; the same applies hereinafter) for the purpose of weight reduction.

  In this type of heat sink with a circuit board, when bonding dissimilar metals, diffusion bonding may be applied from the viewpoint of bonding reliability (Patent Document 1). In diffusion bonding, a metal plate and a heat sink are joined by heating the workpiece while pressing the circuit board against the heat sink after assembling the workpiece by superimposing the heat sink and the circuit board. .

Japanese Patent Laid-Open No. 2006-63145

  However, the thermal expansion coefficient of the ceramic plate in the circuit board is greatly different from the thermal expansion coefficient of the aluminum material constituting the heat sink. Therefore, when the object to be processed is cooled after the joining of the metal plate and the heat sink is completed, a difference occurs in the amount of contraction between the ceramic plate and the heat sink. As a result, warping and residual stress are generated in the ceramic plate in the heat sink with a circuit board after diffusion bonding is completed.

  The circuit board after diffusion bonding is constrained by a heat sink via a diffusion layer. For this reason, for example, when the temperature of the circuit board and the heat sink rises due to the soldering operation of the semiconductor element or 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 is a heat sink body made of an aluminum material provided with a base portion having a flat plate shape,
A low expansion plate having a linear expansion coefficient lower than that of the copper material and bonded onto the base portion;
An intermediate plate made of an aluminum material joined on the low expansion plate;
A circuit board disposed on the intermediate plate,
The circuit board is
A back metal layer made of a copper material joined on the intermediate plate;
A ceramic plate laminated on the back metal layer;
A circuit metal layer made of a copper material laminated on the ceramic plate,
The joint part between the base part and the low expansion plate, the joint part between the low expansion plate and the intermediate plate, and the joint part between the intermediate plate and the back metal layer are diffusions containing an element constituting the member to be joined. A heat sink with a circuit board having a layer.

Another aspect of the present invention is a method of manufacturing a heat sink with a circuit board according to the above aspect,
Performing a surface treatment to remove the natural oxide film present on the surfaces of the base portion, the low expansion plate, the intermediate plate and the back surface metal layer;
The base portion, the low expansion plate placed on the base portion, the intermediate plate placed on the low expansion plate, and the intermediate plate and the back metal layer are in contact with each other. Assembling an object to be processed having the circuit board placed thereon,
In the method of manufacturing a heat sink with a circuit board, the object to be processed is heated while pressing the circuit board toward the base portion, and the diffusion layer is collectively formed at the boundary between adjacent members by diffusion bonding.

  The low expansion plate, the intermediate 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”). . That is, the heat sink has the base portion made of an aluminum material and the circuit metal layer made of a copper material arranged on the outermost side in the laminated structure described above, and has a linear expansion coefficient on the inner side than the copper material. The low low expansion plate and the ceramic plate are disposed. An intermediate plate made of an aluminum material and a back metal layer are disposed between the low expansion plate and the ceramic plate.

  As described above, in a laminated structure in which a layer made of an aluminum material or a copper material and a layer made of a material having a lower linear expansion coefficient than these materials are arranged symmetrically, the above ceramics can be used when the temperature changes. The direction of the warp generated in the plate is opposite to the direction of the warp generated in the low expansion plate. As a result of canceling out the warpage of the two, it is possible to reduce the warpage of the ceramic plate at the time of completion of joining, and to reduce the warpage of the ceramic plate caused by the subsequent temperature change. As a result, cracking of the ceramic plate can be suppressed over a long period of time.

  Moreover, in the manufacturing method of said aspect, after superposing | stacking the components mentioned above and assembling the said to-be-processed object, diffusion bonding is performed collectively. 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. It is the II-II sectional view taken on the line of FIG. It is a partially expanded sectional view of the outer periphery edge vicinity of the low expansion board in the test body E2 of Example 5.

  In the heat sink, the heat sink body has a flat base portion. A low expansion plate is joined to one side of the base portion in the thickness direction via a diffusion 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 portion is preferably 1.0 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 viewpoint, the thickness of the base portion is more preferably 1.0 to 1.3 times the thickness of the circuit metal layer, and further preferably 1.0 to 1.2 times.

  The heat sink body may further include an outer frame portion that is provided upright from the outer peripheral edge of the base portion and is disposed around the low expansion plate, the intermediate plate, and the circuit board. The outer frame portion can easily suppress the displacement of the low expansion plate, the intermediate plate, and the circuit board placed on the base portion in the manufacturing process of the heat sink.

  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, it is possible to further suppress the displacement of the low expansion plate or the like 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 may be easily displaced in the manufacturing process of the heat sink. 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 joined to the base portion via the diffusion layer. The thickness of the low expansion plate is preferably 0.5 to 2.0 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 1.0 to 2.0 times the thickness of the ceramic plate, further preferably 1.25 to 1.75 times, and more preferably 1.5 to A ratio of 1.6 times is particularly preferable.

  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 coefficient of linear expansion is the same as that of the ceramic plate of the circuit board, the warp generated in the ceramic plate and the warp generated in the low expansion plate can be effectively offset. 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; A laminated material in which a metal layer having a low linear expansion coefficient such as molybdenum and a copper layer are laminated; a composite material such as a diamond dispersed composite copper material or a ceramic dispersed copper material can be employed.

  The low expansion plate preferably has a multilayer structure in which a plurality of metal layers are laminated. In this case, by arranging a metal layer that can be easily diffusion-bonded to the aluminum material on the plate surface to be bonded to the base portion or the intermediate plate, the base portion and Diffusion bonding with the intermediate plate can be performed more easily.

  As the low expansion plate having a multilayer structure, for example, a laminated material in which a copper layer is laminated on one side or both sides of a metal layer having a low linear expansion coefficient such as tungsten or molybdenum can be employed.

  The linear expansion coefficient of the low expansion plate is more preferably 0.85 to 2.3 times the linear expansion coefficient of the ceramic plate. In this case, stress and warpage generated in the ceramic plate during and after bonding 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 viewpoint, the linear expansion coefficient of the low expansion plate is more preferably 1.0 to 1.75 times the linear expansion coefficient of the ceramic plate, and even more preferably 1.1 to 1.5 times. It is especially preferable to set it as 1.2 to 1.3 times.

  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, the stress concentration on the corners of the ceramic plate that occurs during and after joining can be more effectively mitigated. As a result, cracking of the ceramic plate can be suppressed over a longer period.

  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 plate is joined to the low expansion plate via the diffusion layer. For example, the intermediate plate may be made of aluminum having a purity of 99.0 to 99.85%. By setting the purity of the low expansion plate to 99.0% or more, the thermal conductivity of the intermediate 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.

  The intermediate 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 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.

  A circuit board is disposed on the intermediate plate. 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. The back metal layer is joined to the intermediate plate via the diffusion layer. As the circuit metal layer and the back metal layer, a plate material made of known copper or copper 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 plate extends outward from the outer peripheral edge of the back metal layer, and the outer peripheral edge of the low expansion plate extends outward from the outer peripheral edge of the intermediate plate. And the outer periphery edge of the said intermediate | middle board and the outer periphery edge of the said low expansion board may each have the protrusion part which protruded in the said circuit board side. In this case, in the manufacturing process of the heat sink, positioning when the intermediate plate and the circuit board are overlaid on the low expansion plate can be performed more easily. As a result, the heat sink can be manufactured more easily. Moreover, since the clearance gap between a low expansion board and an intermediate board and the clearance gap between an intermediate board and a back surface metal layer can be made small, the effect of the further improvement of cooling performance can also be anticipated.

  The protrusion is positively formed on the outer peripheral edge of the intermediate plate and the low expansion plate by adding a step for forming the protrusion during the manufacturing process of the intermediate plate and the low expansion plate. May be. Further, for example, burrs or the like generated in the manufacturing process of the intermediate plate and the low expansion plate can be used as the protruding portion.

  That is, in manufacturing the heat sink, first, the above-described components are prepared by a conventional method. Here, in the preparation of the low expansion plate and the intermediate 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 cost, burrs are generated at the outer peripheral edges of the low expansion plate and the intermediate 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.

  Therefore, the outer peripheral edge of the intermediate plate extends outward from the outer peripheral edge of the back surface metal layer, and the outer peripheral edge of the low expansion plate extends outward from the outer peripheral edge of the intermediate plate. These problems can be avoided by producing a low expansion plate and an intermediate plate. In this case, the burr of the low expansion plate and the intermediate plate can be configured as the protruding portion, and contact between the burr of the low expansion plate and the intermediate plate and the components stacked on these components can be avoided. 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. Furthermore, in this case, it is also possible to achieve the operational effects of the above-described protrusions.

  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 plate to the outer peripheral edge of the low expansion plate should be 0.1 mm or more. That's fine. Similarly, the protrusion amount of the outer peripheral edge of the intermediate plate, that is, the distance from the outer peripheral edge of the back metal layer to the outer peripheral edge of the intermediate plate may be 0.1 mm or more.

  Although the upper limit of these protrusion amount is not specifically limited, From a viewpoint of size reduction of a heat sink, it is preferable that protrusion amount shall be 4.0 mm or less.

  Moreover, in the said manufacturing method, after preparing each component by a conventional method, the surface treatment which removes the natural oxide film which exists in the surface of a base part, a low expansion board, an intermediate | middle board, and a back surface metal layer is performed. As the surface treatment, for example, a method of washing these surfaces with an acid can be applied. By removing the natural oxide film, the diffusion layer can be easily formed in the subsequent diffusion bonding step.

  After performing the surface treatment described above, the parts to be processed are assembled by sequentially superimposing the parts. Thereafter, the object to be processed is heated to perform diffusion bonding while pressing the circuit board toward the base portion. When the object to be processed is heated in a vacuum, the atoms constituting each member diffuse to each other in the portion where the members to be bonded are in contact with each other.

  By this interdiffusion, a diffusion layer including an element constituting the member to be joined, that is, an element constituting the base portion and an element constituting the low expansion plate is formed between the base portion and the low expansion plate. The Further, similarly to the above, a diffusion layer containing an element constituting the member to be joined is formed between the low expansion plate and the intermediate plate and between the intermediate plate and the back surface metal layer. As a result, in the state where diffusion bonding is completed, adjacent members to be bonded are bonded via the diffusion layer.

The heating conditions in the diffusion bonding can be appropriately selected from known conditions according to the material of the member to be bonded. For example, when performing diffusion bonding between a copper material and an aluminum material, the degree of vacuum during heating is set to 10 ⁻¹ Pa or less, the heating temperature is set to 400 to 545 ° C., and the holding time is set to 0.5 to 6 hours. it can.

  Further, in manufacturing the heat sink, an insert metal is interposed between the base portion and the low expansion plate, between the low expansion plate and the intermediate plate or between the intermediate plate and the back surface metal layer, if necessary. Diffusion bonding of each component may be performed via an insert metal. In this case, at the time of diffusion bonding, atoms constituting both are diffused to each other at the contact portion between the member to be bonded and the insert metal.

  Therefore, when the insert metal remains after diffusion bonding, a diffusion layer containing both the element constituting the member to be joined and the element constituting the insert metal is formed between the member to be joined and the insert metal. Is done. In addition, when the insert metal disappears after diffusion bonding, a diffusion layer including both the element constituting the member to be joined and the element constituting the insert metal is formed between adjacent members to be joined. . As a result, in the state where the diffusion bonding is completed, the respective components are bonded via the diffusion layer.

  As the insert metal, for example, gold, silver, copper or titanium can be used. These insert metals may be formed on the surface of each member by cold spray, ion plating, vacuum deposition, sputtering, or the like, and an insert metal foil may be sandwiched between the members. The thickness of the insert metal can be set to 0.1 to 1.0 μm, for example.

  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 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 that of the copper material, and is bonded onto the base portion 21. The intermediate plate 4 is made of an aluminum material and is joined to the low expansion plate 3.

  The circuit board 5 is disposed on the intermediate plate 4. The circuit board 5 is made of a copper material, and is composed of a back surface metal layer 51 bonded onto the intermediate plate 4, a ceramic plate 52 laminated on the back surface metal layer 51, and a copper material. And a laminated circuit metal layer 53. The joint portion between the base portion 21 and the low expansion plate 3, the joint portion between the low expansion plate 3 and the intermediate plate 4, and the joint portion between the intermediate plate 4 and the back surface metal layer 51 are diffusions containing an element constituting the member to be joined. It has layers 20, 30, 40.

  As shown in FIGS. 1 and 2, the heat sink body 2 of this 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. Further, 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 bonded to one plate surface 211 of the base portion 21 via the diffusion layer 20. 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. As shown in 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 plate 4, and the circuit board 5 as shown in FIGS. 1 and 2. .

  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 joined to the base portion 21 via the diffusion layer 20. The low expansion plate 3 of this example is a nickel plate having a thickness of 0.64 mm. In addition, the typical linear expansion coefficient of nickel is 13.3 ppm / K, and has a lower linear expansion coefficient than the typical linear expansion coefficient (16-17 ppm / K) of a copper material. Further, the diffusion layer 20 contains aluminum that constitutes the base portion 21 and nickel that constitutes the low expansion plate 3.

  An intermediate plate 4 is laminated on the low expansion plate 3 via a diffusion layer 30. The diffusion layer 30 contains nickel constituting the low expansion plate 3 and aluminum constituting the intermediate plate 4.

  On the intermediate plate 4, a back metal layer 51 of the circuit board 5 is laminated via a diffusion layer 40. In the circuit board 5 of this example, a back metal layer 51 made of copper material having a thickness of 0.4 mm, a ceramic plate 52 made of silicon nitride having a thickness of 0.32 mm, and a circuit metal layer 53 made of copper material having a thickness of 0.4 mm are sequentially formed. It has a stacked three-layer structure. In addition, the diffusion layer 40 includes aluminum constituting the intermediate plate 4 and copper constituting the back surface metal layer 51.

  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 the intermediate plate 4, and three types of heat sinks 1 (test body) A1 to A3) were prepared. The test specimen was produced by the following method.

  First, the A3003 alloy plate material 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 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.

  Next, these components were washed with dilute hydrochloric acid for 3 minutes, and surface treatment was performed to remove the natural oxide films present on the surfaces of the base portion 21, the low expansion plate 3, the intermediate plate 4, and the back surface metal layer 51. And the low expansion board 3, the intermediate | middle board 4, and the circuit board 5 were mounted in this order on the base part 21, and the to-be-processed object was assembled. A jig was attached to the object to be processed, and the object to be processed was heated to 450 ° C. in a vacuum with the circuit board 5 pressed against the base part 21 side. After the temperature of the object to be processed reached 450 ° C., the temperature was maintained for 1 hour, and diffusion layers 20, 30, and 40 were collectively formed at the boundary between adjacent members to be bonded by diffusion bonding. The test bodies A1-A3 were produced by the above.

  In this example, for comparison with the test bodies A1 to A3, a test body R in which the circuit board 5 was directly bonded onto 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 plate 4 are not provided.

  About these test bodies A1-A3 and test body R, the curvature of the circuit board 5 after diffusion joining, the curvature of the circuit board 5 at the time of soldering, cooling performance, and durability were evaluated.

-Warping of the circuit board 5 after diffusion bonding After removing the test body after diffusion bonding from the jig, the difference in height between the center portion and the outer peripheral end portion of the circuit board 5 is measured. The amount of warpage. The circuit board 5 after diffusion bonding is curved so that the circuit board 5 side in the stacking direction of the base portion 21 and the circuit board 5 is convex. The warpage amount of the circuit board 5 after diffusion bonding 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, the temperature of the heating element in the test body R is Tr (K), the temperature of the heating element in the test bodies A1 to A3 is Ts (K), and the cooling performance reduction rate 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 performed by repeating 1000 cycles of a heating step held at 150 ° C for 30 minutes and a cooling step held 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 or a copper material and a layer made of a material having a lower linear expansion coefficient than these materials are symmetrically arranged. The warpage after diffusion bonding 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 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, a laminated material in which a plurality of metal layers are laminated is used as the low expansion plate 3. Specifically, the low expansion plate 3 of this example has a three-layer structure in which a copper layer having a thickness of 0.05 mm is laminated on both sides of a molybdenum layer having a thickness of 0.80 mm.

  Specimens B1 to B10 were produced in the same manner as in Example 1 except that the above-described laminated material was used for the low expansion plate 3 and the configurations of the intermediate 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.

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

  The low expansion plate 3 of this example is a laminated material having a three-layer structure having a copper layer and a molybdenum layer. Copper and molybdenum have a higher thermal conductivity than nickel. Therefore, as shown in Table 2 and Table 3, the cooling performance of the test bodies B1 to B10 was improved as compared to the test bodies A1 to A3 (see Table 1).

  Among these test bodies, the test bodies B1 to B3 and B6 to B8 have a linear expansion coefficient of the low expansion plate 3 that is 0.85 to 2.3 times that 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 each metal layer 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 main body 2 is changed to 3.5 mm, and the configurations of the low expansion plate 3, the intermediate plate 4, and the ceramic plate 52 are changed as shown in Table 4. Specimens C1 to C5 were produced in the same manner as in Example 2. 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 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, 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. (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. The structure of the heat sink body 2 and the intermediate plate 4 was changed as shown in Table 6. For molybdenum, the natural oxide film present on the surface can be removed by washing with hot water at 60 ° C. or higher. Therefore, in this example, the low expansion plate 3 was washed with hot water of 60 ° C. or higher for 3 minutes instead of dilute hydrochloric acid. Except for these points, specimens D1 to D5 were produced in the same manner as in Example 1. In Table 6, in the low expansion plate 3 of this example, 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 of the base portion 21. The thickness of the intermediate 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, since the linear expansion coefficient of the low expansion plate 3 is 0.85 to 2.3 times the linear expansion coefficient of the ceramic plate 52, the amount of warping during soldering is determined by the test bodies B1 to B10 (Table 3)).

  Moreover, as shown in Table 6 and Table 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)
This example is an example of the heat sink 105 having the low expansion plate 305 and the intermediate plate 405 provided with the protruding portions 31 and 41. In this example, specimens E1 and E2 were produced as follows.

  First, the A6063 alloy plate material is forged to dispose the heat dissipating fins 23, and then the plate surface opposite to the surface on which the heat dissipating fins 23 are disposed 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 plates 4 and 405, and press punching is performed on a molybdenum plate having a thickness of 1.0 mm to produce low expansion plates 3 and 305. did.

  More specifically, the stamping process was performed so that the intermediate plate 4 and the low expansion plate 3 used for the test body E1 had the same dimensions as the back surface metal layer 51. On the other hand, with respect to the intermediate plate 405 used for the test body E2, press punching was performed so that the dimensions were slightly larger than the back surface metal layer 51. Further, the low expansion plate 305 used for the test body E2 was subjected to press punching so that the size thereof was slightly larger than that of the intermediate plate 405. By these press punching processes, burrs were formed on the outer peripheral edges of the intermediate plates 4 and 405 and the low expansion plates 3 and 305 of this example.

  As the circuit board 5, a commercially available product was adopted.

  After each part is washed with acid or hot water of 60 ° C. or more to remove the natural oxide film existing on the surface, the low-expansion plate 3, the intermediate plate 4, and the circuit board 5 are placed on the base portion 21 for the specimen E 1. Were placed in this order, and the workpiece was assembled (not shown).

  On the other hand, for the test body E2, as shown in FIG. 3, the low expansion plate 305, the intermediate plate 405, and the circuit are formed so that the burr protrudes toward the circuit board 5 in the stacking direction of the base portion 21 and the circuit board 5. The substrates 5 were sequentially stacked to assemble the object to be processed. Thereafter, diffusion bonding was performed in the same manner as in Example 1 to prepare test bodies E1 and E2.

  As shown in FIG. 3, the test body E <b> 2 after diffusion bonding has the outer peripheral edge 411 of the intermediate plate 405 extending outward from the outer peripheral edge 511 of the back surface metal layer 51 and the outer periphery of the low expansion plate 305. The edge 311 extended outward from the outer peripheral edge 411 of the intermediate plate 405. Further, the outer peripheral edge 411 of the intermediate plate 405 and the outer peripheral edge 311 of the low expansion plate 305 had projecting portions 31 and 41 projecting to the circuit board 5 side, respectively.

  More specifically, the outer peripheral edge 411 of the intermediate plate 405 extended outward by 0.1 mm from the outer peripheral edge 511 of the back surface metal layer 51. Further, the outer peripheral edge 311 of the low expansion plate 305 extended outward by 0.1 mm from the outer peripheral edge 411 of the intermediate plate 405. The protrusions 31 and 41 are burrs formed on the outer peripheral edges 311 and 411 of the low expansion plate 305 and the intermediate plate 405 during the press punching process.

  Evaluation was performed in the same manner as in Example 1 using the specimens E1 and E2 obtained as described above. The evaluation results were as shown in Table 8.

  As shown in Table 8, in the test bodies E1 and E2, the linear expansion coefficient of the low expansion plate 3 is 0.85 to 2.3 times the linear expansion coefficient of the ceramic plate 52. Can be suppressed to be equal to or higher than those of the test bodies B1 to B10 (see Table 3). Further, as shown in FIG. 3, the test body E2 includes the base portion 21 and the circuit board without the protruding portions 31 and 41 of the low expansion plate 305 and the intermediate plate 405 coming into contact with the material laminated on the upper portion thereof. 5 protrudes toward the circuit board 5 in the stacking direction. Therefore, compared with the test body E1, the clearance gap between the low expansion board 305 and the intermediate board 405 and the clearance gap between the intermediate board 405 and the back surface metal layer 51 were able to be made small. As a result of the above, it is considered that the specimen E2 was able to improve the cooling performance as compared with the specimen E1.

DESCRIPTION OF SYMBOLS 1,105 Heat sink with a circuit board 2 Heat sink main body 20 Diffusion layer 21 Base part 3,305 Low expansion board 30 Diffusion layer 4,405 Intermediate board 40 Diffusion layer 5 Circuit board 51 Back surface metal layer 52 Ceramics board 53 Circuit metal layer

Claims (11)

A heat sink body made of an aluminum material provided with a base portion having a flat plate shape;
A low expansion plate having a linear expansion coefficient lower than that of the copper material and bonded onto the base portion;
An intermediate plate made of an aluminum material joined on the low expansion plate;
A circuit board disposed on the intermediate plate,
The circuit board is
A back metal layer made of a copper material joined on the intermediate plate;
A ceramic plate laminated on the back metal layer;
A circuit metal layer made of a copper material laminated on the ceramic plate,
The joint part between the base part and the low expansion plate, the joint part between the low expansion plate and the intermediate plate, and the joint part between the intermediate plate and the back metal layer are diffusions containing an element constituting the member to be joined. A heat sink with a circuit board having a layer.   The heat sink with a circuit board according to claim 1, wherein the intermediate plate is made of aluminum having a purity of 99.0 to 99.85%.   The heat sink with a circuit board according to claim 1, wherein the intermediate plate is made of a 6000 series aluminum alloy.   The thickness of the said low expansion board is a heat sink with a circuit board of any one of Claims 1-3 which is 0.5 to 2.0 times the thickness of the said ceramic board.   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 0.85 to 2.3 times a linear expansion coefficient of the ceramic plate.   The thickness of the said base part is a heat sink with a circuit board of any one of Claims 1-5 which is 1.0 to 1.5 times the thickness of the said circuit metal layer.   The heat sink with a circuit board according to claim 1, wherein the heat sink body is made of a 6000 series aluminum alloy.   The heat sink with a circuit board according to any one of claims 1 to 7, wherein the low expansion plate has a multilayer structure in which a plurality of metal layers are laminated.   The outer peripheral edge of the intermediate plate extends outward from the outer peripheral edge of the back metal layer, and the outer peripheral edge of the low expansion plate extends outward from the outer peripheral edge of the intermediate plate. The outer peripheral edge of the intermediate plate and the outer peripheral edge of the low expansion plate each have a protruding portion protruding toward the circuit board, respectively. Heat sink with circuit board. A method for manufacturing a heat sink with a circuit board according to any one of claims 1 to 9,
Performing a surface treatment to remove the natural oxide film present on the surfaces of the base portion, the low expansion plate, the intermediate plate and the back surface metal layer;
The base portion, the low expansion plate placed on the base portion, the intermediate plate placed on the low expansion plate, and the intermediate plate and the back metal layer are in contact with each other. Assembling an object to be processed having the circuit board placed thereon,
A method of manufacturing a heat sink with a circuit board, wherein the object to be processed is heated while pressing the circuit board toward the base part, and the diffusion layer is collectively formed at a boundary between adjacent members to be bonded by diffusion bonding. A method for manufacturing a heat sink with a circuit board according to any one of claims 1 to 9,
Performing a surface treatment to remove the natural oxide film present on the surfaces of the base portion, the low expansion plate, the intermediate plate and the back surface metal layer;
The base portion, the low expansion plate disposed on the base portion, the intermediate plate disposed on the low expansion plate, and the circuit board disposed on the intermediate plate, An object to be processed with an insert metal interposed in at least one of the base portion and the low expansion plate, between the low expansion plate and the intermediate plate, and between the intermediate plate and the back metal layer. Assembled,
A method of manufacturing a heat sink with a circuit board, wherein the object to be processed is heated while pressing the circuit board toward the base portion, and the diffusion layer is formed collectively by diffusion bonding.

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