JP4104429B2 - Module structure and module using it - Google Patents

Module structure and module using it Download PDF

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Publication number
JP4104429B2
JP4104429B2 JP2002323337A JP2002323337A JP4104429B2 JP 4104429 B2 JP4104429 B2 JP 4104429B2 JP 2002323337 A JP2002323337 A JP 2002323337A JP 2002323337 A JP2002323337 A JP 2002323337A JP 4104429 B2 JP4104429 B2 JP 4104429B2
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Prior art keywords
module
heat sink
metal
metal plate
circuit board
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JP2004158659A (en
Inventor
正浩 伊吹山
学 宇都
勲 杉本
秀幸 江本
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電気化学工業株式会社
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L2924/00Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001Technical content checked by a classifier
    • H01L2924/0002Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a module comprising a ceramic circuit board on which a heat generating electrical component such as a power element is mounted and a metal heat sink, and more particularly to a module suitably used for a power supply and a module structure used therefor.
[0002]
[Prior art]
In recent years, with the advancement of power electronics, devices controlled by power devices such as IGBTs and MOS-FETs are rapidly increasing. In particular, mobile devices such as electric railways and vehicles are rapidly becoming power devices. In addition, with increasing interest in environmental issues, electric cars and hybrid cars that use a gasoline engine and an electric motor have begun to be marketed, and the demand for power modules mounted on them is expected to increase. For such applications, exceptionally high reliability is required for the purpose of use.
[0003]
In a conventional power module, aluminum oxide (Al) is used to release heat generated in a semiconductor element or the like so that the temperature of the semiconductor element does not rise above a predetermined temperature. 2 O 3 ), Silicon nitride (Si 3 N 4 ), Mounting a semiconductor element on a ceramic circuit board such as aluminum nitride (AlN) by soldering, and soldering it to a heat sink made of a metal such as copper (Cu) or aluminum (Al) Met.
[0004]
However, in the case of such a structure, cracks may occur in the solder layer between the ceramic circuit board and the heat sink when subjected to repeated thermal cycles accompanying the operation of the semiconductor element or temperature changes in the operating environment. . The crack is generated in the solder layer because of a thermal stress generated by a difference in thermal expansion between the ceramic substrate and the heat sink. The presence of cracks in the solder layer (hereinafter also simply referred to as “solder cracks”) reduces the heat dissipation of the semiconductor element, increases the temperature of the semiconductor element, and as a result, deteriorates the semiconductor element. Reduce the reliability of the entire power module.
[0005]
In addition, with higher integration and higher power of semiconductor devices, higher heat dissipation is required, and from the viewpoint of environmental pollution, the use of lead-free solder is desired. However, the so-called lead-free solder has a problem that although it has a higher thermal conductivity than the Pb—Sn-based solder that is widely used at present, the reliability is inferior.
[0006]
In order to avoid these problems, it has been studied to use an Al—SiC composite material or Cu—Mo composite material having a thermal expansion coefficient closer to that of a ceramic substrate as a heat sink, but it is special compared to a conventional metal heat sink. In addition to being manufactured by the method, there is a problem that the cost of the processing step and the surface treatment step is high, and it is much more expensive than a metal heat sink.
[0007]
On the other hand, an attempt has been made to avoid the occurrence of solder cracks and improve heat dissipation at the same time by directly joining the heat sink and the ceramic circuit board using a brazing material instead of solder (Japanese Patent Laid-Open No. 9-97865). No. JP, 10-270596, A).
[0008]
However, in this case, the thermal stress generated by the thermal expansion difference between the ceramic circuit board and the metal heat sink tends to cause separation of the bonding interface and cracking of the ceramic board, and the semiconductor element on the ceramic circuit board. Since the stress applied to the lower solder also increases, there is a problem that solder cracks under the semiconductor element are more likely to occur. In addition, due to the heat history that is received under the power module assembly process and actual use conditions, the shape and warpage of the heat sink changes greatly, causing inconvenience when assembling the power module, and heat dissipation due to reduced adhesion between the heat sink and the heat dissipation block. Sexual decline may occur.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and the object thereof is a module structure composed of a ceramic circuit board and a metal heat sink, depending on the power module assembly process and the thermal history received under actual use conditions. Highly reliable over a long period of time with little change in shape, easy to assemble, and unlikely to cause peeling at the bonding interface, cracks in the ceramic substrate, cracks in the solder layer, etc., and good heat dissipation The object is to provide a module capable of maintaining the sex.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have conducted various experimental studies, and in a structure in which a stress buffer layer is provided between a ceramic substrate and a metal heat sink, the metal that becomes the metal heat sink and the stress buffer layer. When various measures are taken on the plate, it is found that the resulting module structure undergoes little change in shape and warpage and does not impair heat dissipation even when subjected to a thermal history under the assembly process or actual usage conditions. This has led to the present invention.
[0011]
That is, the present invention is a module structure in which a ceramic circuit board is bonded to a metal heat sink via a metal plate (A) containing aluminum as a main component, and the metal plate containing aluminum as a main component. The module structure is characterized in that the thickness of (A) is 400 μm or more and 1200 μm or less.
[0012]
Preferably, the metal heat sink is made of an aluminum alloy having a Vickers hardness of 30 HV or higher after heat treatment at 630 ° C. for 4 minutes.
[0013]
The metal plate (A) is preferably bonded to a ceramic circuit board and a metal heat sink via a brazing material. When a brazing material containing Al as a main component and containing Mg and at least one selected from the group consisting of Cu, Zn, Ge, Si, Sn, and Ag is used, a highly reliable joint is obtained. It is done.
[0014]
More preferably, the module structure is used, and the exothermic electricity mounted at a desired position on the metal plate (B) on which the circuit is formed provided on the opposite side of the metal plate (A) of the ceramic circuit board. A module in which a part is provided and a cutout is provided on the surface of the metal plate (A) and / or the metal heat sink, and the cutout is the exothermic electrical component when a cross section of the module is assumed. This module is provided in a region other than the frustum region formed by drawing a straight line group of 45 ° vertically downward from the edge in contact with the metal plate (B).
[0015]
The notch is a surface of the metal plate (A) that is in contact with the metal heat sink, or a surface of the metal heat sink covered with the ceramic substrate when viewed from the side where the heat-generating electrical component of the module is present, or It is preferable that the module is provided on the surface of the metal heat sink that is not covered with the ceramic substrate when viewed from the side where the heat-generating electrical component of the module is present.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below.
The ceramic substrate used in the present invention may be any ceramic substrate as long as it satisfies the required characteristics such as electrical insulation, thermal conductivity, and mechanical strength, but is a nitriding ceramic that has high thermal conductivity. Aluminum (AlN), or silicon nitride (Si that combines high strength and relatively high thermal conductivity 3 N 4 ) Is more preferable.
[0017]
The module structure of the present invention has a structure in which a ceramic circuit board is bonded to a metal heat sink. Two methods are known for reducing thermal stress in bonding of different materials. In the first method, a heat sink having a low coefficient of thermal expansion is used in order to reduce the difference in thermal expansion between the two materials. However, this method has a cost problem as described above. The second method is a method adopted by the present invention, which is based on the idea of inserting a stress buffer layer between a metal heat sink and a ceramic circuit board to absorb thermal strain, and has a low elasticity. This is a method of performing thermal stress relaxation by plastic deformation using an index material as an intermediate layer (stress relaxation layer).
[0018]
In the present invention, a metal plate mainly composed of aluminum having a thickness of 400 μm or more and 1200 μm or less is used as the stress buffer layer. As described above, the stress relaxation layer must have a low elastic modulus and yield strength as its mechanical properties. However, in the present invention, for application to the application, it has high thermal conductivity from the surface of heat dissipation, does not melt when soldering a semiconductor element, and further has sufficient strength with a ceramic substrate and a metal heat sink. It is necessary to satisfy the requirements such as being able to be joined.
[0019]
As a result of intensive studies on various materials and thicknesses, the present inventors have arrived at the present invention in order to find a stress relaxation layer that satisfies the above requirements. In the present invention, a metal plate mainly composed of aluminum is selected for the stress relaxation layer, and this is used as the metal plate (A). As the metal plate (A), for example, aluminum having a JIS designation of 1000 series, among them high purity aluminum having a purity of 99% by mass or more, more preferably high purity aluminum having a purity of 99.9% by mass or more may be used.
[0020]
In the present invention, the metal plate (A) has a thickness of 400 μm to 1200 μm, preferably 600 μm to 1000 μm. When the thickness exceeds 1200 μm, the stress generated by the metal plate (A) and the heat sink may reach the metal plate (B) side and adversely affect the durability of the solder under the silicon chip. Further, it is not preferable because the pattern accuracy is deteriorated and the cost is increased when the pattern is formed by etching. If the thickness is less than 400 μm, the action as a buffer layer may be insufficient due to hardening due to element diffusion from the joint portion, or the Al buffer layer may not withstand repeated stress due to thermal cycling and may break.
[0021]
The present invention has a feature that the reliability of the power module can be ensured even when copper or aluminum having high thermal conductivity or an alloy containing them as a main component is used as the metal heat sink. Since an Al alloy is light and inexpensive, it is suitable as a heat sink. In that case, it is preferable to use an aluminum alloy having a Vickers hardness of 30 Hv or more, more preferably 60 Hv or more after heat treatment at 630 ° C. for 4 minutes. good.
[0022]
When the Al alloy having the above characteristics is used as a heat sink, the warpage of the obtained module structure can be extremely reduced in cooperation with the thickness of the metal plate (A) being in a suitable range. In addition, even when subjected to thermal history under the power module assembly process or its actual use conditions, the change in shape and warpage of the module structure is small, and the separation of the bonding interface and the breakage of the metal plate (A) as the buffer layer are prevented As a result, damage to the semiconductor element and increase in thermal resistance can be prevented, and the various reliability of the power module is positively affected.
[0023]
Any aluminum alloy may be used for the heat sink as long as it has the above characteristics. Examples of such alloys include aluminum alloys obtained by adding an appropriate amount of one or more of Si or Mg to Al, for example, JIS names 2000 series, 5000 series, 6000 series, or 7000 series.
[0024]
The content of Si and Mg is preferably about 0.1 to 4.0% by mass from the viewpoint of physical properties and workability, but if exceeding this, the Vickers hardness is 30 Hv or more, preferably 60 Hv or more. This is excellent in that the shape change and warpage change, which are the characteristics of the module structure, are reduced. In addition, the Al alloy used in the present invention may contain other components and impurities as long as the above characteristics are satisfied. An Al alloy containing 2.0% by mass or more of Mg, Cu, or Zn is excellent in that the Vickers hardness and bending strength are high, and the shape change and warpage change of the obtained module structure are small. Furthermore, it is sufficient that the aluminum alloy constitutes the skeleton of the heat sink material, and it is not necessary that the entire heat sink is the aluminum alloy.
[0025]
Although the Vickers hardness of the Al alloy for heat sink suitable for the present invention is shown, the bending strength after high-temperature annealing is measured, and at that time, it can also be expressed by load and displacement. After heating a test piece having a thickness of 5 mm and a width of 5 mm at 600 ° C. for 10 minutes and measuring a three-point bending strength with a span of 30 mm, the load when the displacement is 200 μm is 200 N or more, preferably 300 N or more. The same effect as above can be obtained.
[0026]
Moreover, the shape of the heat sink may be a plate having a flat back surface or a fin formed. Moreover, you may have a structure which a cooling medium can pass through. In this case, it is preferable because the overall size of the power control device including the power module and the cooling measure can be reduced and the cost can be reduced.
[0027]
In the module structure of the present invention, the metal plate (A) may be bonded to the metal heat sink via a brazing material or lead-free solder because of its material, shape, workability, and bonding strength. preferable.
[0028]
When Pb-Sn solder is used for bonding between the heat sink and the ceramic circuit board, as described above, the reliability is reduced due to solder cracks associated with the thermal cycle, environmental problems, and the solder wettability of aluminum is poor. Although there is a problem that it must be processed by plating or the like, it is not preferable, but the problem is solved by brazing. Furthermore, in the present invention, it is more preferable that the metal plate (A) mainly composed of aluminum is joined to the ceramic circuit board via a brazing material.
[0029]
In the present invention, the brazing material for joining the heat sink and the metal plate (A), and the metal plate (A) and the ceramic substrate may be appropriately selected according to the type of the metal heat sink. In particular, when this brazing material contains Al as a main component and contains Mg and at least one selected from the group consisting of Cu, Zn, Ge, Si, Sn and Ag, a highly reliable joint Is obtained. The amount of Mg contained in the brazing material is suitably 0.1 to 2.0% by mass, and if it is less than 0.1% by mass, sufficient bonding cannot be obtained, and if it is more than 2.0% by mass, the joint part In some cases, the thermal shock resistance of the steel is reduced, and undesirable operations occur in the operation of the joining furnace. As an aluminum alloy suitable for the brazing material of the present invention, for example, those having an appropriate composition of JIS names 2000 series, 3000 series, 5000 series, 6000 series, and 7000 series can be used.
[0030]
The brazing material may be either an alloy or an alloy, and may be any form of foil, powder, mixed powder, or mixed powder containing a compound that retains the metal component at a bonding temperature or lower, or a combination thereof. May be used. The alloy foil is superior in terms of heat cycle resistance at the joint, difficulty in forming microvoids, and ease of handling. In particular, an aluminum alloy foil of JIS designation 2017 is preferably used for joining the metal plate (A) and the ceramic substrate.
[0031]
Further, in order to join the heat sink and the metal plate (A), the joining temperature needs to be lower than the melting point of the heat sink, and if necessary, the amount of components other than Al is increased to lower the melting point of the brazing material composition. Good. For example, the most preferable result is obtained when the Al alloy foil is combined with silver foil or silver powder. Moreover, regarding the thickness of the brazing material, when the thickness is 10 to 60 [mu] m, preferably 10 to 40 [mu] m, a strong bond with good reproducibility and good heat cycleability is obtained.
[0032]
When joining an Al alloy heat sink and a metal plate (A) containing aluminum as a main component, heating and joining are generally performed in a vacuum. At this time, if the unevenness and surface roughness of both joint surfaces are large, In some cases, poor bonding occurs frequently or the heat cycle resistance of the bonded portion is inferior. Moreover, if it joins in nitrogen, the influence of the surface shape of the member to join will become larger, and it will become easy to produce a joining defect in the outer peripheral part of a metal plate (A). In particular, when an extruded material is used for the heat sink, the extrusion marks on the surface cause poor bonding and peeling in the heat cycle test.
[0033]
These problems can be solved by using Al alloy foil or alloy powder containing Mg in combination with Ag powder or Ag foil. The combined use of such an alloy and Ag is epoch-making in that a highly reliable bond with sufficient durability can be obtained even in a nitrogen atmosphere. Moreover, it is preferable also when the Vickers hardness after the heat treatment of the heat sink is high or when the bending strength is high, because a strong joint portion that hardly causes peeling can be obtained. According to this method, since it can join in nitrogen, it can join in a normal nitrogen atmosphere continuous furnace, and it has the feature that manufacturing cost can be reduced significantly.
[0034]
For brazing, if the brazing material is an alloy foil, it is sandwiched between the heat sink and the metal plate (A), or between the metal plate (A) and the ceramic substrate, and heated in vacuum, nitrogen or inert gas. And join. When a mixture of alloy powder or metal powder is used as the brazing material, a roll coater or screen printing is applied to either one of the surfaces when the heat sink and the metal plate (A) or the metal plate (A) and the ceramic substrate are joined. It may be applied by a machine. If the coating amount is too small, sufficient bonding cannot be performed. If the coating amount is too large, the brazing material may flow and flow out of the joint, which may be inconvenient, or a hard and fragile layer may be formed at the interface, impairing the reliability of the bonding. . 1 to 5 mg / cm as coating amount 2 The degree is preferred.
[0035]
When joining heat sink and metal plate (A) using Al alloy brazing foil and Ag powder together, just apply silver powder to one surface of brazing foil, heat sink or metal plate (A) Thus, the effect of using silver together can be obtained. Moreover, the coating amount of silver powder is 1 to 3 mg / cm. 2 The degree is sufficient.
[0036]
In the present invention, lead-free solder may be used for joining the metal heat sink and the metal plate (A). Since lead-free solder is harder and less likely to be plastically deformed than Pb-Sn solder, it is usually said that solder cracks are likely to occur due to thermal cycling. In the present invention, a sufficiently reliable module structure Can be obtained. Reliability can be ensured by using Sn-Ag-Cu solder or Sn-Zn solder as lead-free solder. In particular, Sn-Ag (3 mass%)-Cu (0.5 mass%) Should be used.
[0037]
The metal plate (B) provided on one side of the ceramic substrate and serving as a circuit on which a heat-generating electrical component is mounted may be anything as long as it is a highly conductive metal, but is inexpensive and has a high thermal conductivity. High copper, aluminum, or alloys thereof are preferably used. Moreover, as said copper and aluminum, a high purity thing with high electrical conductivity and high plastic deformation ability with respect to stress generation is preferable.
[0038]
In the present invention, the notch portion is provided at a specific position on the upper surface and / or the lower surface of the metal plate (A) and / or the metal heat sink provided so as to be in contact with the heat sink on the heat sink side of the ceramic substrate. This occurs due to a difference in thermal expansion coefficient between the ceramic substrate and the heat sink caused by heat treatment such as when a heat-generating electrical component such as a semiconductor element is mounted while maintaining heat dissipation in the state where the notch is not present. This is because the distortion of the metal plate (A) caused by the thermal stress is relieved by the notch and the deformation of the module structure accompanying the temperature history can be reduced.
[0039]
The notch introduction position in the present invention is a frustum region formed by drawing a straight line group of 45 ° vertically downward from an edge in contact with the metal plate (B) of the exothermic electrical component when a cross section of the module is assumed. It is an area other than. By specifying the notch at the above position, the heat dissipation generated from the electrical components and circuits such as the semiconductor elements in the module is not deteriorated, and thus the semiconductor element malfunctions without increasing the temperature of the semiconductor elements. This is because it is possible to prevent the occurrence of a phenomenon such as shortening the service life due to the occurrence of the phenomenon.
[0040]
The notch introduction position is limited by the size, shape, and mounting position of the heat-generating electrical component to be mounted. In order to reduce the deformation of the heat dissipation structure, the cutout portion introduced from the heat sink side into the metal plate (A) provided to be in contact with the heat sink on the heat sink side of the ceramic substrate is most effective. The larger the depth of the notch is, the more effective it is to reduce deformation of the release module structure, and it is preferable to divide the metal plate, but it is not always necessary to divide. The width, the number, and the shape of the cutouts are not particularly limited as long as they are not included in the region that deteriorates heat dissipation.
[0041]
Moreover, the same effect is acquired by introduce | transducing a notch part in the part which contact | connected the metal plate (A) of the heat sink. In this case, it is possible to introduce a notch by, for example, performing simple groove processing on the heat sink surface, and there is an effect of excellent productivity. In this case as well, the larger the depth of the cutout portion, the more effective, but the depth is preferably ½ or less of the thickness of the heat sink. This is because if the deeper cutout is provided, the module structure obtained by joining the ceramic circuit board and the heat sink may be greatly deformed. The width, the number, and the shape of the cutouts may be any method as long as they are provided within the specific range.
[0042]
If notches are not provided at the interface between the metal plate and the heat sink due to restrictions on the size, shape, and mounting position of the heat-generating electrical components, deformation can be reduced even if it is provided on the upper surface and / or lower surface of the heat sink other than the bonding interface effective. In this case, the degree of freedom in selecting a place that is spatially separated from the parts that exhibit the important functions of modules such as exothermic electrical components, circuits, and ceramic substrates is increased, resulting in excellent productivity. The effect is obtained that the module can be provided at a lower cost.
[0043]
The ceramic circuit board used in the present invention is formed by joining ceramics to a metal plate for circuit (B) and a metal plate (A) mainly composed of aluminum, and then using conventional methods such as etching and machining. Or it can manufacture easily by forming the notch part of a metal plate (A). Or it can manufacture also by mounting and joining the metal plate (A, B) which formed the circuit and the notch part beforehand in the ceramic substrate.
[0044]
The module structure and module of the present invention can be obtained by applying a conventionally known method, but the method described later has good reproducibility and high productivity. Can be obtained.
[0045]
That is, a ceramic circuit board provided with a metal plate (B) having a circuit formed in advance on the front surface and a metal plate (A) mainly composed of aluminum serving as a stress relaxation layer on the back surface by brazing or the like is prepared. A method of joining a ceramic circuit board and a metal heat sink by placing a brazing material between the stress buffer layer side surface and the metal heat sink, or heating under pressure, or a circuit metal plate (B), a ceramic substrate In addition, a metal plate (A) mainly composed of aluminum as a stress buffer layer and a metal heat sink are sequentially arranged, and a brazing material is disposed between the metal plates and bonded simultaneously.
[0046]
Further, in order to form a module structure with a notch, a notch is introduced in advance into the surface of the metal plate (A) or metal heat sink of the ceramic circuit board by etching or machining, and then the ceramic circuit A method of joining a ceramic circuit board and a metal heat sink by placing a brazing material between the metal plate (A) of the board and the metal heat sink and heating under pressure, or a circuit metal board (B), a ceramic board, A method in which the metal plate (A) mainly composed of aluminum into which the notch portion is introduced and the metal heat sink are sequentially arranged, and a brazing material is disposed between the metal plates (A) and bonded simultaneously is preferable. Furthermore, in the latter method, the circuit metal plate (B) may be formed in advance, or may be formed by applying a method such as etching after bonding. Further, when a notch is introduced into a region other than the bonding interface of the heat sink, it may be provided after bonding.
[0047]
Next, electronic components such as semiconductor elements are mounted on the circuit of the module structure consisting of a ceramic circuit board and a metal heat sink by soldering, etc., and wire bonding is performed as necessary to complete the circuit. The inventive module can be obtained.
[0048]
When the metal heat sink is a solid plate, a power module mounted with a highly heat-generating electrical component such as a high-power semiconductor element assembled using the module structure of the present invention, through a high thermal conductive grease, Used by attaching to a heat dissipation unit such as a heat dissipation fin. If the heat sink has a fin shape, it is used as it is. Further, when the heat sink is in the form of a pipe through which the cooling medium passes, piping for passing the cooling medium is made and used.
[0049]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to this.
[0050]
[ reference Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2] As a ceramic substrate, a silicon nitride substrate having a thermal conductivity of 75 W / mK by laser flash method and an average value of three-point bending strength of 650 MPa is large. The thing of 34 * 34 * 0.635mm was prepared. Further, an Al plate (hereinafter referred to as an Al circuit plate) having a purity of 99.99% and a thickness of 0.4 mm as a metal plate for a circuit, and an Al plate for a stress buffer layer (hereinafter referred to as a buffer Al plate). ) Having various thicknesses as shown in Table 1 with a purity of 99.99% were prepared.
[0051]
The Al circuit board and the Al layer for buffer layer were overlapped on both the front and back surfaces of the silicon nitride substrate through JIS name 2017 Al foil (20 μm thickness), and pressurized in the vertical direction at 5 MPa. And 10 -3 While heating at a temperature of 635 ° C. in a vacuum of the Pa level, both of the Al plates were bonded to the silicon nitride substrate.
[0052]
After bonding, an etching resist was screen-printed on a desired portion on the surface of the Al plate, and a circuit pattern was formed by etching with a ferric chloride solution, thereby producing a ceramic circuit board.
[0053]
Next, a 50 × 50 × 4 mm JIS name 1050Al plate was prepared as a heat sink. Then, a 20 μm-thick JIS designation 2017 Al foil is sandwiched between the buffer Al plate bonded to the ceramic circuit board and the heat sink, and the whole is pressed vertically at 5 MPa with a graphite jig. -3 Heat treatment was performed under conditions of 600 ° C. for 4 minutes in a vacuum of Pa stage, and the ceramic circuit board was bonded to the heat sink. Electroless Ni plating was performed on the aluminum metal surface of the joined body to obtain a module structure. In this case, ten module structures each having the same configuration were produced.
[0054]
A silicon chip of 10 mm × 10 mm × 0.3 mm, the back of which is plated with Au on the Al circuit surface of the manufactured module structure, is soldered at 350 ° C. using solder with a mass ratio of lead and tin of 90:10, respectively. Joined.
About the obtained module, the heat cycle which makes -40 degreeC * 30 minutes-room temperature x10 minutes-> 125 degreeC x 30 minutes-room temperature x10 minutes 1 cycle was implemented 3000 times. Thereafter, the ultrasonic deep-flaw device was used to observe the presence or absence of peeling or cracking at the bonding interface between the ceramic substrate and the heat sink and between the ceramic substrate and the silicon chip. The results are also shown in Table 1.
[0055]
Except for Comparative Example 1, in any of the modules, no peeling of the joint due to heat cycle or generation of cracks in the silicon nitride substrate was observed. In Comparative Example 1, a part of the joint part was peeled off, and fatigue failure of the buffer Al plate occurred remarkably. In Example 1, fatigue failure was observed at the corner portion of the buffer layer Al plate. In Comparative Example 2, cracks were observed over the entire surface of the solder layer between the silicon chip and the circuit board, and in Example 5, some cracks were similarly observed in the solder layer.
[0056]
[Table 1]
[0057]
[ reference Examples 6, 7, 8, 9, 10, 11, Comparative Example 3] Using the seven types of heat sinks shown in Table 2, using the following procedure, a module was produced with 10 repetitions, and evaluated. Of the present invention reference Examples and comparative examples were used.
[0058]
As a ceramic substrate, an AlN (aluminum nitride) substrate having a size of 34 × 34 × 0.635 mm, a thermal conductivity of 180 W / mK by a laser flash method, and an average value of three-point bending strength of 400 MPa was prepared. In addition, two Al (aluminum) plates of 30 × 30 × 0.4 mm JIS name 1085 were prepared as metal plates to be provided on the surface of the AlN substrate with respect to the heat sink (hereinafter referred to as the back surface of the substrate). .
[0059]
The Al plate was overlapped on both the front and back surfaces of the AlN substrate via a JIS name 2017 Al foil (20 μm thickness) and pressed in the vertical direction at 10 MPa. And 10 -2 The Al plate and the AlN substrate were joined while being heated in a Pa vacuum at a temperature of 630 ° C. for 20 minutes. After bonding, an etching resist was screen-printed on a desired portion on the surface of the Al plate, and a circuit pattern was formed by etching with a ferric chloride solution, thereby producing a ceramic circuit board.
[0060]
Next, an aluminum plate having a composition shown in Table 2 having a size of 46 × 46 × 4 mm was prepared as a heat sink. Then, silver powder is screen-printed to 1.5 mg / cm on the surface of the ceramic circuit board placed in contact with the heat sink. 2 A JIS designation 2017 Al foil having a thickness of 20 μm is placed between the heat sink and the heat sink, and is pressed at 10 MPa in the vertical direction with a graphite jig in a nitrogen atmosphere at 510 to 600 ° C. for 4 minutes. Heat treatment was performed to join the heat sink and the ceramic circuit board. Finally, electroless Ni plating was performed on the entire surface of the substrate and the heat radiating plate to obtain a module structure.
[0061]
A 13 mm × 13 mm × 0.4 mm silicon chip plated with Au on the Al circuit surface of the fabricated module structure was used at 350 ° C. using solder with a lead and tin mass ratio of 90:10, respectively. Joined.
[0062]
About the module obtained by the said operation, the curvature amount of the silicon chip was measured. The amount of warpage was evaluated as a difference in height between both end portions and the central portion on the diagonal line of the silicon chip, and the average value of 10 pieces is shown in Table 3.
[0063]
[Table 2]
[0064]
[Table 3]
[0065]
[Example 12, Comparative Example 4]
As a ceramic substrate, a silicon nitride substrate (dimension 34 × 26 × 0.635 mm) having a thermal conductivity of 70 W / mK measured by a laser flash method and a three-point bending strength of 750 MPa was prepared. For both the metal plate (A) and the metal plate (B), an aluminum plate having a purity of 99.99% and a thickness of 0.4 mm was prepared.
[0066]
Aluminum plates were stacked on both front and back surfaces of the silicon nitride substrate via JIS name 2017 Al foil (20 μm thickness), and pressed from the vertical direction at 5 MPa. And 10 -3 While heating at a temperature of 635 ° C. in a vacuum of Pa level, both of the aluminum plates were bonded to the silicon nitride substrate.
[0067]
After bonding, an etching resist is screen-printed on the desired portions of the upper and lower aluminum plate surfaces, and a circuit pattern is formed on the metal plate (B) by performing an etching treatment with a ferric chloride solution. A notch portion for strain relaxation was formed in A) to produce a ceramic circuit board. In addition, the notch portion is a region other than the frustum region formed by drawing a 45 ° straight line group vertically downward from the edge in contact with the metal plate (B) of the semiconductor element which is one of the exothermic electrical components to be mounted later. Provided in the area. Further, in Comparative Example 4, a ceramic circuit board was produced by the same method without providing a notch in the metal plate (A).
[0068]
Next, as a heat sink, a JIS name 1050 aluminum plate having four mounting screw holes of 60 × 140 × 4 mm was prepared. And while putting JIS name 2017 aluminum alloy foil between the two ceramic circuit boards and the aluminum plate, -3 Heating was performed at 590 ° C. for 10 minutes in a vacuum of Pa level, and the heat sink and the ceramic circuit board were joined to form a module structure.
[0069]
Next, the amount of change in warpage was measured assuming a temperature history before and after soldering of the semiconductor element. The method of measuring the amount of warpage is described. First, the shape at the bottom of the module structure after joining is measured from the end to the end in the longitudinal direction (span 140 mm) with a stylus-type contouring machine, corrected at both ends, and digitized. did. Thereafter, the module structure was subjected to a heat treatment at 360 ° C. for 10 minutes, and then the bottom shape was measured. The difference between before and after the heating was taken, and the maximum value was taken as the amount of change in warpage. The results are shown in Table 4.
[0070]
Next, for the evaluation of heat dissipation, after electroless nickel plating is performed on the entire surface of the obtained module structure, a 10 mm square semiconductor element is used at a predetermined position of the circuit in a reducing atmosphere, Soldering was performed at 360 ° C. The cross-sectional structures of the modules of Example 10 and Comparative Example 4 are shown in FIGS. 1 and 2, respectively. An aluminum heat dissipating unit was fastened to the bottom surface of the module member with four screws through silicone grease. The thermal resistance was obtained by cooling the heat radiating unit with water and measuring the temperature of the silicon element and the temperature of the aluminum radiating unit while passing a constant current in the thickness direction of the silicon element. The results are shown in Table 4.
[0071]
[Table 4]
[0072]
About the obtained module, the heat cycle which makes -40 degreeC * 30 minutes-room temperature * 10 minutes-> 125 degreeC * 30 minutes-room temperature * 10 minutes 1 cycle was implemented 3000 times. Thereafter, the presence or absence of peeling at the bonding interface between the ceramic substrate and the heat sink due to ultrasonic flaws was observed. In any of the modules, abnormalities such as peeling of the circuit board due to heat cycle and generation of cracks in the silicon nitride substrate were not observed.
[0073]
[Comparative Example 5]
A module was produced in the same manner as in Example 10 except that a notch to be introduced into the metal plate (A) was provided vertically below the silicon element. In the same manner as in Example 10, the amount of warpage change and thermal resistance before and after soldering of the semiconductor element were evaluated. The cross-sectional structure of the module is shown in FIG. 3, and the evaluation results are shown in Table 4.
[0074]
Example 13
A portion of the aluminum heat sink that is in contact with the ceramic circuit board, and is formed by drawing a 45 ° straight line group vertically downward from the edge in contact with the metal plate (B) of the semiconductor element to be mounted in a later process. A module was produced in the same manner as in Comparative Example 4 except that a groove having a width of 1 mm and a depth of 1.5 mm was formed in a region other than by a diamond cutter, and evaluation was performed in the same manner as in Comparative Example 4. FIG. 4 shows the cross-sectional structure of the module, and Table 4 shows the evaluation results.
[0075]
[Examples 14 and 15]
A module in which a ceramic circuit board was bonded to an aluminum heat sink by the same method as in Comparative Example 4 was produced. In Example 14, a groove with a width of 3 mm and a depth of 2 mm was formed at the position of the upper surface of the heat sink shown in FIG. 5 and at the position of the lower surface of the heat sink shown in FIG. Thereafter, modules were produced and evaluated by the same method as in Comparative Example 4. The evaluation results are shown in Table 4.
[0076]
【The invention's effect】
The module structure according to the present invention and the module using the same are less expensive even when subjected to a temperature history such as when a semiconductor is mounted while using an inexpensive metal heat sink, easy to assemble, and in actual use conditions Even when subjected to repeated temperature history below, there are features such as peeling at the bonding interface, fatigue failure of the aluminum layer, cracking of the ceramic substrate, cracking of the solder layer, etc., and excellent heat dissipation, It is suitable for power modules for various uses, particularly power modules for mobile devices, and is very useful in industry.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a module according to Embodiment 12 of the present invention.
2 is a cross-sectional view of a conventionally known module according to Comparative Example 4. FIG.
3 is a cross-sectional view of a conventionally known module according to Comparative Example 5. FIG.
FIG. 4 is a sectional view of a module according to Embodiment 13 of the present invention.
FIG. 5 is a sectional view of a module according to Embodiment 14 of the present invention.
FIG. 6 is a cross-sectional view of a module according to Embodiment 15 of the present invention.
[Explanation of symbols]
1 Ceramic substrate
2 Heat-generating electrical components (semiconductor elements)
3 Metal plate (B)
4 Metal plate (A)
5 Heat sink
A frustum region formed by drawing a 45 ° straight line group vertically downward from the edge of the exothermic electrical component in contact with the metal plate (A)
B Notch

Claims (8)

  1. The ceramic circuit board to the metal heat sink, using a first module structure formed by joining through a metal plate containing aluminum as its main component is less than a thickness of 400μm or more 1200 [mu] m, the first metal of the ceramic circuit board A heat-generating electrical component mounted at a desired position is provided on a second metal plate formed with a circuit on the opposite side of the plate, and a notch is provided on the surface of the first metal plate. A frustum formed by drawing a 45 ° straight line group vertically downward from an edge where the cutout portion is in contact with the second metal plate of the heat-generating electrical component when a cross section of the module is assumed A module provided in an area other than a partial area.
  2. The ceramic circuit board to the metal heat sink, using a first module structure formed by joining through a metal plate containing aluminum as its main component is less than a thickness of 400μm or more 1200 [mu] m, the first metal of the ceramic circuit board A module in which a heat-generating electrical component mounted at a desired position is provided on a second metal plate having a circuit formed on the side opposite to the plate, and a notch is provided on the surface of the metal heat sink. When the cross section of the module is assumed, the frustum region formed by drawing a 45 ° straight line group vertically downward from the edge where the notch is in contact with the second metal plate of the heat-generating electrical component A module characterized by being provided in a region other than.
  3. The ceramic circuit board to the metal heat sink, using a first module structure formed by joining through a metal plate containing aluminum as its main component is less than a thickness of 400μm or more 1200 [mu] m, the first metal of the ceramic circuit board An exothermic electrical component mounted at a desired position is provided on a circuit-formed second metal plate provided on the opposite side of the plate, and on the surfaces of the first metal plate and the metal heat sink. A module provided with a notch, wherein when the cross section of the module is assumed, a 45 ° straight line group is drawn vertically downward from the edge where the notch contacts the second metal plate of the heat-generating electrical component . A module provided in a region other than a frustum region to be formed.
  4. The module according to claim 1, wherein the notch is provided on a surface of the first metal plate on a side in contact with the metal heat sink.
  5. The cutout portion is provided on the surface of the metal heat sink covered with the ceramic circuit board when viewed from the side where the heat-generating electrical component of the module is present. module.
  6. 4. The cutout portion is provided on a metal heat sink surface not covered with a ceramic circuit board when viewed from a side of the module where the heat-generating electrical component is present. Modules.
  7. The module according to any one of claims 1 to 6, wherein the first metal plate uses a module structure formed by joining a ceramic circuit board and a metal heat sink via a brazing material. .
  8. The module according to claim 7, wherein the brazing material contains Al as a main component, and contains Mg and one or more selected from the group consisting of Cu, Zn, Ge, Si, Sn, and Ag.
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JP5019148B2 (en) * 2005-06-16 2012-09-05 日立金属株式会社 Ceramic circuit board and semiconductor module using the same
JP2007012725A (en) * 2005-06-29 2007-01-18 Fuji Electric Device Technology Co Ltd Semiconductor device
JP5061442B2 (en) * 2005-09-15 2012-10-31 三菱マテリアル株式会社 Insulated circuit board and insulated circuit board with cooling sink
WO2007032486A1 (en) * 2005-09-15 2007-03-22 Mitsubishi Materials Corporation Insulating circuit board and insulating circuit board provided with cooling sink section
JP4747284B2 (en) * 2005-09-15 2011-08-17 三菱マテリアル株式会社 Insulated circuit board with cooling sink
JP2008004871A (en) * 2006-06-26 2008-01-10 Mitsubishi Materials Corp Power module substrate, method of manufacturing the same and power module
JP5479181B2 (en) * 2010-03-30 2014-04-23 株式会社豊田中央研究所 Insulating substrate and module having the insulating substrate
JP5796299B2 (en) * 2011-02-02 2015-10-21 三菱マテリアル株式会社 Power module substrate with heat sink, manufacturing method of power module substrate with heat sink, and power module
JP5736807B2 (en) * 2011-02-02 2015-06-17 三菱マテリアル株式会社 Power module substrate with heat sink, manufacturing method of power module substrate with heat sink, and power module
JP5966790B2 (en) * 2012-09-12 2016-08-10 三菱マテリアル株式会社 Manufacturing method of power module substrate with heat sink
JP6252827B2 (en) * 2013-03-22 2017-12-27 三菱マテリアル株式会社 Aluminum heat exchanger, power module substrate with heat sink, and method of manufacturing aluminum heat exchanger

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