Integrated heat sink type insulated circuit board

Abstract

The integrated heat sink type insulating circuit board includes: a heat sink (20) having a top plate portion (21) and heat radiating fins (22); an insulating resin layer (12) formed on the top plate portion (21) of the heat sink (20); and a circuit layer (13) disposed on the surface of the insulating resin layer (12) opposite to the heat sink (20) and composed of a metal sheet. When the maximum length of the top plate portion (21) of the heat sink (20) is set as L, the warpage amount of the top plate portion (21) of the heat sink (20) is set as Z, the warpage amount with the joint surface side of the top plate portion (21) of the heat sink (20) and the insulating resin layer (12) being convex is set as a positive warpage amount, and the curvature of the heat sink (20) is defined as C = |(8 × Z) / L 2 |, the peel strength P (N / cm) of the insulating resin layer (12) and the maximum curvature C max (1 / m) of the heat sink (20) when heated from 25°C to 300°C max is P / C max > 60.

Description

Technical Field

[0001] The present invention relates to a radiator-integrated insulating circuit board, which includes: a radiator having a top plate portion and heat dissipation fins; an insulating resin layer formed on the top plate portion of the radiator; and a circuit layer formed on one surface of the insulating resin layer.

[0002] This application claims priority based on Japanese Patent Application No. 2020-044215 filed on March 13, 2020, and incorporates its content herein. Background Art

[0003] Power modules, LED modules, and thermoelectric modules have the following structure: on an insulating circuit board in which a circuit layer made of a conductive material is formed on one surface of an insulating layer, a power semiconductor element, an LED element, and a thermoelectric element are joined. In addition, as the insulating layer, a layer made of ceramics or a layer made of an insulating resin has been proposed.

[0004] As an insulating circuit board having an insulating resin layer, for example, in Patent Document 1, a heat dissipation fin-integrated insulating circuit board is proposed in which a radiator having heat dissipation fins and a circuit layer are insulated by an insulating resin sheet.

[0005] Moreover, in Patent Document 2, a composite component is disclosed in which a heat dissipation base substrate is bonded to at least one surface of a heat generation component by a thermally conductive insulating adhesive film. In Patent Document 2, in order to suppress cracks from occurring in the thermally conductive insulating adhesive film due to stress, the relationship between the shear adhesive force and the thermal stress and the relationship between the elongation at break and the thermal strain are specified, where the stress is generated by the expansion or contraction of the heat dissipation component and the heat generation component accompanying temperature changes.

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-204700

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2019-041111

[0008] However, in a radiator-integrated insulating circuit board in which an insulating resin layer is formed on the top plate portion of a radiator having heat dissipation fins and a circuit layer is formed on the insulating resin layer, warping sometimes occurs due to temperature changes. In particular, in a radiator having heat dissipation fins, the thickness of the portion where the heat dissipation fins are formed is different from the portion where the heat dissipation fins are not formed, so there is a tendency to easily generate warping.

[0009] When warping occurs in the radiator-integrated insulating circuit board, it is possible that the end portion of the circuit layer peels off from the insulating resin layer or the peeling progresses to the inside of the insulating resin layer.

[0010] Here, in Patent Document 2, stress and strain within the plane are evaluated, but stress in a direction perpendicular to the plane is not considered. Therefore, peeling of the circuit layer or internal peeling of the insulating resin layer is not addressed. Summary of the invention

[0011] The present invention is made in view of the above situation, and aims to provide a heat sink-integrated insulating circuit substrate with excellent reliability that can suppress peeling between the circuit layer and the insulating resin layer or internal peeling of the insulating resin layer even when warping occurs due to temperature changes.

[0012] In order to solve the aforementioned problems, the heat sink integrated insulating circuit substrate of the present invention is characterized in that it comprises: a heat sink having a top plate portion and heat dissipation fins; an insulating resin layer formed on the top plate portion of the heat sink; and a circuit layer, which is arranged in a circuit pattern on the surface of the insulating resin layer on the opposite side of the heat sink and is composed of a metal sheet. When the maximum length of the top plate portion of the heat sink is set to L, the warping amount of the top plate portion of the heat sink is set to Z, the convex deformation of the top plate portion of the heat sink on the bonding surface side with the insulating resin layer is set to a positive warping amount, and the curvature of the heat sink is defined as C = |(8×Z) / L 2 |, the peel strength P (N / cm) of the insulating resin layer and the maximum curvature C of the heat sink when heated from 25°C to 300°C max (1 / m) ratio P / C max P / C max >60.

[0013] According to the heat sink integrated insulating circuit substrate of this configuration, the peel strength P (N / cm) of the insulating resin layer is related to the maximum curvature C of the heat sink when heated from 25°C to 300°C. max (1 / m) ratio P / C max P / C max >60, sufficient peel strength can be ensured against stress caused by warping, and even when the heat sink is warped due to temperature changes, peeling between the circuit layer and the insulating resin layer or internal peeling of the insulating resin layer can be suppressed.

[0014] Here, in the heat sink integrated insulating circuit substrate of the present invention, the thickness t of the circuit layer is C The thickness t of the top plate portion of the heat sink H Ratio t C / t H Can satisfy 0.5≤t C / t H ≤1.5.

[0015] At this time, the thickness t of the circuit layer disposed through the insulating resin layer C and the thickness t of the top plate portion of the radiator H The ratio t C / t H is not very different, and the warpage amount can be controlled to be low.

[0016] Moreover, in the radiator-integrated insulating circuit board of the present invention, the peeling strength P (N / cm) of the insulating resin layer and the maximum curvature C of the radiator when heated from 25°C to 300°C max (1 / m) The ratio P / C max can be P / C max >90.

[0017] At this time, sufficient peeling strength can be further ensured for the stress caused by warpage, and even when warpage occurs in the radiator due to temperature change, peeling between the circuit layer and the insulating resin layer or internal peeling of the insulating resin layer can be suppressed.

[0018] Moreover, in the radiator-integrated insulating circuit board of the present invention, the insulating resin layer may contain an inorganic material filler.

[0019] At this time, since the thermal conductivity of the insulating resin layer can be ensured, the heat dissipation characteristics are excellent, and heat from the heat source mounted on the circuit layer can be effectively dissipated on the radiator side.

[0020] According to the present invention, there can be provided a radiator-integrated insulating circuit board that can suppress peeling between the circuit layer and the insulating resin layer or internal peeling of the insulating resin layer even when warpage occurs due to temperature change, and has excellent reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic explanatory diagram of a power module including the radiator-integrated insulating circuit board according to the embodiment of the present invention.

[0022] Figure 2 is an explanatory diagram showing the relationship between the warpage amount and the curvature of the radiator-integrated insulating circuit board according to the embodiment of the present invention.

[0023] Figure 3 is an explanatory diagram showing a method for measuring the peeling strength of the insulating resin layer of the radiator-integrated insulating circuit board according to the embodiment of the present invention.

[0024] Figure 4 is a flowchart illustrating an example of a method for manufacturing the radiator-integrated insulating circuit board according to the embodiment of the present invention.

[0025] Figure 5 is Figure 4 A schematic explanatory diagram of a method for manufacturing a heat sink integrated insulating circuit board as shown. Detailed implementation mode

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0027] Figure 1 The heat sink integrated insulating circuit board 10 of the embodiment of the present invention and the power module 1 using the heat sink integrated insulating circuit board 10 are shown.

[0028] Figure 1 The power module 1 shown includes a heat sink integrated insulating circuit board 10 and a semiconductor element 3 joined to one surface ( Figure 1 the upper surface in ) of the heat sink integrated insulating circuit board 10 by a solder layer 2.

[0029] The semiconductor element 3 is made of a semiconductor material such as Si. The solder layer 2 for joining the heat sink integrated insulating circuit board 10 and the semiconductor element 3 is, for example, a solder material of the Sn - Ag system, Sn - Cu system, Sn - In system, or Sn - Ag - Cu system (so-called lead-free solder material).

[0030] The heat sink integrated insulating circuit board 10 includes a heat sink 20, an insulating resin layer 12 formed on one surface ( Figure 1 the upper surface in ) of the top plate portion 21 of the heat sink 20, and a circuit layer 13 formed on one surface ( Figure 1 the upper surface in ) of the insulating resin layer 12. In addition, the above semiconductor element 3 is joined to one surface ( Figure 1 the upper surface in ) of the circuit layer 13.

[0031] The heat sink 20 includes a top plate portion 21 and heat dissipation fins 22 protruding from the other surface ( Figure 1 the lower surface in ) of the top plate portion 21.

[0032] The heat sink 20 has the following structure: while diffusing heat in the surface direction in the top plate portion 21, it dissipates heat to the outside through the heat dissipation fins 22. Therefore, the heat sink 20 is made of a metal with excellent thermal conductivity, for example, made of copper or a copper alloy, aluminum or an aluminum alloy. In the present embodiment, it is made of an aluminum alloy (A6063).

[0033] Here, the thickness of the top plate portion 21 of the heat sink 20 is preferably set within a range of 0.5 mm or more and 6.0 mm or less.

[0034] In addition, the radiator 20 may have a structure in which the heat dissipation fins 22 are needle-shaped fins, or may have a structure in which the heat dissipation fins 22 are formed in a comb shape. Moreover, it is preferable that the volume ratio of the heat dissipation fins 22 in the portion where the heat dissipation fins 22 are formed is in the range of 10% or more and 40% or less.

[0035] The insulating resin layer 12 is a layer that prevents electrical connection between the circuit layer 13 and the radiator 20 and is made of an insulating resin.

[0036] In the present embodiment, in order to ensure the strength of the insulating resin layer 12 while ensuring thermal conductivity, it is preferable to use a resin containing an inorganic material filler. Here, as the filler, for example, alumina, boron nitride, aluminum nitride, etc. can be used. From the viewpoint of ensuring the thermal conductivity of the insulating resin layer 12, the content of the filler is preferably 50% by mass or more, more preferably 70% by mass or more. And the upper limit of the content of the filler is not particularly limited and can be 95% by mass or less.

[0037] Moreover, as the thermosetting resin constituting the insulating resin layer 12, an epoxy resin, a polyimide resin, a silicone resin, etc. can be used. Here, if it is a silicone resin, it can contain 70% by mass or more of the filler, and if it is an epoxy resin, it can contain 80% by mass or more of the filler. And the upper limit of the content of the filler is not particularly limited and can be 95% by mass or less.

[0038] In addition, in order to sufficiently ensure the insulation of the insulating resin layer 12, it is preferable that the thickness of the insulating resin layer 12 is 25 μm or more, preferably 50 μm or more. On the other hand, in order to further ensure the heat dissipation of the radiator integrated insulating circuit board 10, it is preferable that the thickness of the insulating resin layer 12 is 300 μm or less, more preferably 200 μm or less.

[0039] As Figure 5 shown, the circuit layer 13 is formed by bonding a metal sheet 33 made of a metal with excellent conductivity to one surface ( Figure 5 the upper surface in this case) of the insulating resin layer 12. As the metal sheet 33, copper or a copper alloy, aluminum or an aluminum alloy, etc. can be used. In the present embodiment, as the metal sheet 33 constituting the circuit layer 13, a metal sheet obtained by punching a rolled plate of oxygen-free copper can be used.

[0040] A circuit pattern is formed in the circuit layer 13, and one surface ( Figure 1 the upper surface in this case) is the mounting surface for mounting the semiconductor element 3.

[0041] Here, in the radiator integrated insulating circuit board 10 of the present embodiment, the thickness t C of the circuit layer 13 (metal sheet 33) and the thickness t H of the top plate portion 21 of the radiator 20C / t H Preferably, 0.5 ≤ t C / t H ≤ 1.5.

[0042] Specifically, preferably, the thickness t of the circuit layer 13 (metal sheet 33) C is set within the range of 0.3 mm or more and 3.0 mm or less, and the thickness t of the top plate portion 21 of the heat sink 20 H is set within the range of 0.5 mm or more and 6.0 mm or less, and satisfies the above ratio t C / t H .

[0043] Moreover, in the heat sink integrated insulating circuit board 10 of the present embodiment, when the maximum length of the top plate portion 21 of the heat sink 20 (the maximum length of the surface perpendicular to the stacking direction of the heat sink integrated insulating circuit board 10) is set as L, the warpage amount of the top plate portion 21 of the heat sink 20 is set as Z, the warpage amount with a convex shape on the joint surface side of the top plate portion 21 of the heat sink 20 and the insulating resin layer 12 is set as a positive warpage amount, and the curvature of the heat sink 20 is defined as C = |(8 × Z) / L 2 |, the peeling strength P (N / cm) of the insulating resin layer 12 and the maximum curvature C of the heat sink 20 when heated from 25°C to 300°C max (1 / m) ratio P / C max is P / C max > 60. And, there is no particular limitation on the upper limit, but the ratio P / C max can be P / C max < 1000.

[0044] Here, as Figure 2 shown, from the maximum length L of the top plate portion 21 of the heat sink 20 and the warpage amount Z of the top plate portion 21 of the heat sink 20, the curvature C of the heat sink 20 is calculated as C = |(8 × Z) / L 2 |.

[0045] In addition, in the present embodiment, the top plate portion 21 of the heat sink 20 has a rectangular flat plate shape, and the length of the diagonal is the maximum length L. Moreover, the warpage amount Z is the difference between the maximum value and the minimum value in the height direction of the cross section along the diagonal (maximum length).

[0046] And, as Figure 3 shown, the peeling strength of the insulating resin layer 12 is the strength measured by stretching the end portion of the circuit layer 13 (metal sheet 33) upward with reference to the 90° peeling test specified in JIS K6854-1:1999.

[0047] In addition, in this peeling test, the rupture site can be any one of the bonding interface between the top plate portion 21 of the heat sink 20 and the insulating resin layer 12, the bonding interface between the insulating resin layer 12 and the circuit layer 13, and the inside of the insulating resin layer 12.

[0048] The ratio P / C of the peeling strength P (N / cm) of the insulating resin layer 12 to the maximum curvature C max (1 / m) of the heat sink 20 when heated from 25°C to 300°C max is P / C max When P / C > 60, the peeling strength is higher than the stress in the height direction caused by warping, thereby suppressing peeling of the insulating resin layer 12 caused by warping, etc.

[0049] Therefore, by optimizing the material of the resin constituting the insulating resin layer 12 according to the warping amount, or by designing the materials and thicknesses of the circuit layer 13 and the heat sink 20 according to the material of the resin constituting the insulating resin layer 12, and setting P / C max > 60, peeling of the insulating resin layer 12 caused by warping, etc. can be suppressed.

[0050] In addition, in order to more surely suppress peeling of the insulating resin layer 12 caused by warping, etc., it is preferable to make the above ratio P / C max greater than 90.

[0051] Next, with reference to Figure 4 and Figure 5 the manufacturing method of the heat sink integrated insulating circuit board 10 of the present embodiment will be described.

[0052] (Resin composition disposing step S01)

[0053] As Figure 5 shown, on one surface ( Figure 5 the upper surface in this case) of the top plate portion 21 of the heat sink 20, a resin composition 32 containing an inorganic material filler, a resin, and a curing agent is disposed. In the present embodiment, a sheet is used for the resin composition 32.

[0054] (Metal sheet arranging step S02)

[0055] Next, on one surface ( Figure 5 the upper surface in this case) of the resin composition 32, a plurality of metal sheets 33 that will form the circuit layer 13 are arranged in a circuit pattern.

[0056] (Pressing and heating step S03)

[0057] Next, through a pressing device, the heat sink 20, the resin composition 32, and the metal sheet 33 are pressed in the stacking direction and heated, thereby curing the resin composition 32 to form the insulating resin layer 12, and joining the top plate portion 21 of the heat sink 20 to the insulating resin layer 12 and the insulating resin layer 12 to the metal sheet 33.

[0058] In this pressing and heating step S03, it is preferable that the heating temperature is in the range of 120°C or higher and 350°C or lower, and the holding time at the heating temperature is in the range of 10 minutes or longer and 180 minutes or shorter. Also, the pressing load in the stacking direction is preferably in the range of 1 MPa or higher and 30 MPa or lower.

[0059] Here, the heating temperature is more preferably 150°C or higher, and further preferably 170°C or higher. On the other hand, the heating temperature is more preferably 320°C or lower, and further preferably 300°C or lower.

[0060] The holding time at the heating temperature is more preferably 30 minutes or longer, and further preferably 60 minutes or longer. On the other hand, the holding time at the heating temperature is more preferably 120 minutes or shorter, and further preferably 90 minutes or shorter.

[0061] The pressing load in the stacking direction is more preferably 3 MPa or higher, and further preferably 5 MPa or higher. On the other hand, the pressing load in the stacking direction is more preferably 15 MPa or lower, and further preferably 10 MPa or lower.

[0062] Through the above respective steps, the heat sink integrated insulating circuit board 10 of the present embodiment is manufactured.

[0063] According to the heat sink integrated insulating circuit board 10 according to the present embodiment configured as described above, the ratio P / C of the peel strength P (N / cm) of the insulating resin layer 12 to the maximum curvature C max (1 / m) of the heat sink 20 when heated from 25°C to 300°C max is P / C max > 60, so sufficient peel strength against the stress caused by warping can be ensured, and even when warping occurs in the heat sink 20 due to temperature change, peeling between the circuit layer 13 and the insulating resin layer 12 or internal peeling of the insulating resin layer 12 can be suppressed.

[0064] Also, in the present embodiment, when the thickness t C of the circuit layer 13 and the thickness t H of the top plate portion 21 of the heat sink 20 C The ratio t H Satisfies 0.5 ≤ t C / t HWhen it is ≤ 1.5, the thickness t of the circuit layer 13 disposed through the insulating resin layer 12 C and the thickness t of the top plate portion 21 of the heat sink 20 H are not very different, and the warpage amount can be controlled to be low.

[0065] Moreover, in the present embodiment, when the insulating resin layer 12 contains an inorganic material filler, the thermal conductivity of the insulating resin layer 12 can be ensured, and the heat dissipation characteristics are excellent, and the heat from the semiconductor element 3 mounted on the circuit layer 13 can be effectively dissipated on the heat sink 20 side.

[0066] The embodiments of the present invention have been described above, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the present invention.

[0067] In the present embodiment, the case of manufacturing the heat sink integrated insulating circuit board by the manufacturing method of the heat sink integrated insulating circuit board shown in Figure 4 and Figure 5 has been described, but it is not limited thereto.

[0068] And, in the present embodiment, the case where the heat sink is made of oxygen-free copper (OFC) and the circuit layer is made of aluminum alloy (A6053) has been described, but it is not limited thereto, and it can also be made of other metals such as copper or copper alloy, aluminum or aluminum alloy. And it can also be a structure in which a plurality of metals are laminated.

[0069] And, in the present embodiment, the case of mounting a semiconductor element on the heat sink integrated insulating circuit board to form a power module has been described, but it is not limited thereto. For example, an LED element can also be mounted on the circuit layer of the heat sink integrated insulating circuit board to form an LED module, or a thermoelectric element can be mounted on the circuit layer of the heat sink integrated insulating circuit board to form a thermoelectric module.

[0070] Examples

[0071] Hereinafter, the results of the confirmation experiment conducted to confirm the effects of the present invention will be described.

[0072] On the top plate portion of the heat sink having the structure shown in Table 1 (100 mm × 80 mm, the thickness is shown in Table 1), a sheet of the resin composition shown in Table 1 is disposed. On the sheet of the resin composition, a metal sheet forming a circuit layer shown in Table 1 is disposed. The heat sink, the sheet of the resin composition, and the metal sheet that are laminated are pressed in the lamination direction and heated to cure the resin composition to form an insulating resin layer, and the top plate portion of the heat sink is joined to the insulating resin layer and the insulating resin layer is joined to the metal sheet, thereby obtaining a heat sink integrated insulating circuit board. In addition, when the resin material of the sheet is polyimide, the pressing pressure in the lamination direction is 5 MPa, the heating temperature is 300 °C, and the holding time at the heating temperature is 60 minutes. When the resin material of the sheet is epoxy or silicone resin, the pressing pressure in the lamination direction is 10 MPa, the heating temperature is 200 °C, and the holding time at the heating temperature is 60 minutes.

[0073] As described above, for the obtained heat sink integrated insulating circuit board, the following items were evaluated respectively.

[0074] (Maximum curvature C max )

[0075] The warpage amount Z when heated to 300 °C was measured using a moiré three-dimensional shape measuring device (THERMOIRE PS200 manufactured by AKROMETRIX, Inc.).

[0076] Moreover, as described in the column of the specific embodiment, from the maximum length L and the warpage amount Z of the top plate portion 21 of the heat sink, the maximum curvature C of the heat sink when heated from 25 °C to 300 °C was calculated max (1 / m).

[0077] (Peel strength P)

[0078] As described in the column of the specific embodiment, based on the 90° peel test standard specified in JIS K6854-1:1999, the peel strength P was measured by stretching the end portion of the circuit layer (metal sheet) upward.

[0079] (After heat treatment cracking)

[0080] The obtained heat sink integrated insulating circuit board was subjected to a heat treatment at 300 °C for 5 minutes, and the presence or absence of cracking of the insulating resin layer was confirmed. The case where cracking occurred was set as "yes", and the case where no cracking occurred was set as "no".

[0081] The evaluation results of the maximum curvature C max , the peel strength P, and the cracking after heat treatment are shown in Table 2.

[0082] [Table 1]

[0083]

[0084] [Table 2]

[0085]

[0086] According to Table 2, the ratio P / C of the peel strength P (N / cm) of the insulating resin layer to the maximum curvature C max (1 / m) of the heat sink when heated from 25°C to 300°C max In Comparative Examples 1-5 where P / C is 60 or less, cracking was confirmed after the heat treatment.

[0087] In contrast, in Invention Examples 1-18 where the ratio P / C of the peel strength P (N / cm) of the insulating resin layer to the maximum curvature C max (1 / m) of the heat sink when heated from 25°C to 300°C exceeds 60, no cracking was confirmed after the heat treatment. Moreover, even when the resin material is changed, by optimizing the maximum curvature (warpage amount) so that P / C max exceeds 60, the occurrence of cracking after the heat treatment can be suppressed. max From the above, it is confirmed that according to the invention examples, it is possible to provide a heat sink integrated insulating circuit board that can suppress the peeling between the circuit layer and the insulating resin layer or the internal peeling of the insulating resin layer even when warping occurs due to temperature changes, and has excellent reliability.

[0088] Industrial Applicability

[0089] Industrial Applicability

[0090] The heat sink integrated insulating circuit board according to the present invention can suppress the occurrence of internal peeling of the insulating resin layer constituting power modules, LED modules, thermoelectric modules, etc., and improve reliability. Therefore, it has industrial applicability.

[0091] Symbol Explanation

[0092] 10 Heat sink integrated insulating circuit board

[0093] 12 Insulating resin layer

[0094] 13 Circuit layer

[0095] 20 Heat sink

[0096] 21 Top plate portion

[0097] 22 Heat dissipation fins

Claims

1. A radiator integrated insulating circuit board, characterized in that, Comprising: a heat sink having a top plate portion and heat radiating fins; an insulating resin layer formed on the top plate portion of the heat sink; and a circuit layer disposed in a circuit pattern on a surface of the insulating resin layer opposite to the heat sink and composed of a metal sheet, When the maximum length of the top plate portion of the radiator is set as L, the warpage amount of the top plate portion of the radiator is set as Z, the deformation of the top plate portion of the radiator that is convex on the joint surface side with the insulating resin layer is set as a positive warpage amount, and the curvature of the radiator is defined as C = |(8 × Z) / L 2 |, The peel strength P of the insulating resin layer and the maximum curvature C of the heat sink when heated from 25°C to 300°C max The ratio P / C max is P / C max > 60, where the maximum curvature C max and the unit of the peel strength P are 1 / m and N / cm, respectively.

2. The heat sink integrated insulating circuit board according to claim 1, wherein, The thickness t of the circuit layer C and the thickness t of the top plate portion of the radiator H The ratio t C / t H satisfies 0.5 ≤ t C / t H ≤ 1.

5.

3. The heat sink integrated insulating circuit board according to claim 1 or 2, wherein, The peel strength P of the insulating resin layer and the maximum curvature C of the heat sink when heated from 25°C to 300°C max The ratio P / C max is P / C max > 90, where the unit of the maximum curvature C max and the peel strength P are 1 / m and N / cm, respectively.

4. The heat sink integrated insulating circuit board according to any one of claims 1 to 3, wherein, the insulating resin layer contains a filler of an inorganic material.

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