JP2007266224A - Power module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat dissipation of a power module on which an electronic component is loaded. <P>SOLUTION: The power module is provided with a circuit board 2 on which the electronic component 1 is placed on a center of an upper face and a water cooled jacket 3 having a passage which is brought into contact with a lower face of the circuit board 2 and makes cooling water flow just below a contact part. A center of the lower face of the circuit board 2 projects to a lower side compared to an outer peripheral part of the lower face, A part which is brought into contact with the circuit board 2 in the water cooled jacket 3 is depressed to a passage-side along the lower face of the circuit board 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power module having improved heat dissipation by being fixed to a water cooling jacket.

  In recent years, electronic components such as power control devices used in automobiles and the like have become higher in voltage due to the hybridization of the driving system of automobiles, and thus power modules equipped with electronic components are required to have high heat dissipation. It is coming.

  In a conventional power module, a circuit board on which electronic components are mounted is generally fixed to a water cooling jacket via a heat sink such as copper.

A conventional power module is shown in FIG. As shown in FIG. 2, 21 is an electronic component, 22 is a circuit board, 22a is an electric circuit board that is a part on the upper surface side of the circuit board 22, 22b is an insulating board that is a part on the lower surface side of the circuit board 22, and 23 is This is a water cooling jacket for cooling the circuit board 22. For example, the electric circuit board 22a is formed by bonding copper or aluminum to both surfaces of a ceramic substrate using an active brazing material or the like, and forming a circuit by etching or the like. The water-cooling jacket 23 is usually formed with a water channel in consideration of heat dissipation. The insulating substrate 22b is made of a resin or a ceramic material in order to maintain insulation between the electric circuit substrate 22a and the water cooling jacket 23. In addition, since the heat generated from the electronic component 21 is radiated to the water cooling jacket 23 through the electric circuit board 22a, a ceramic material having a high heat dissipation characteristic is more preferable.
JP 2002-26469 A

  Conventionally, the contact surfaces of the circuit board and the water cooling jacket have been increased in flatness to increase the contact area to ensure heat dissipation. However, in recent years, higher heat dissipation has been required. Therefore, the power module of the present invention has been completed in view of the above problems, and its purpose is to improve the heat dissipation of the power module.

  A power module according to the present invention includes a circuit board on which an electronic component is placed at the center of the upper surface, and a water cooling jacket having a flow path for contacting the lower surface of the circuit board and allowing cooling water to flow directly under the contact part And a portion of the water-cooling jacket that is in contact with the circuit board extends along the lower surface of the circuit board. It is characterized by a depression on the roadside.

  The power module of the present invention is characterized in that the lower surface side portion of the circuit board is made of an insulating substrate.

  The power module of the present invention is characterized in that the insulating substrate is made of a silicon nitride sintered body.

  The power module according to the present invention is characterized in that the circuit board has a gently convex curved surface from the outer periphery of the lower surface to the center of the lower surface.

  The power module of the present invention is characterized in that the upper surface of the circuit board is flat.

  A power module according to the present invention includes a circuit board on which an electronic component is placed at the center of the upper surface, and a water cooling jacket that is in contact with the lower surface of the circuit board and has a flow path for flowing cooling water immediately below the contact portion. In the power module provided, the lower surface central portion of the circuit board protrudes below the outer periphery of the lower surface, and the portion that contacts the circuit board of the water cooling jacket is recessed toward the flow path side along the lower surface of the circuit board, Since the flow path in the central portion of the circuit board is narrowed, the flow rate of the cooling water flowing through that portion is increased, so that heat dissipation can be improved.

  In the power module of the present invention, the lower portion of the circuit board is made of an insulating substrate, so that the central portion projects only the shape of the insulating substrate while maintaining the electric circuit portion on the upper surface of the circuit board in a flat plate structure. It can be a structure. Therefore, it becomes difficult for distortion to occur in the electric circuit portion, and the reliability applied to the electric circuit portion can be improved by reducing the stress applied to the electric circuit portion when the circuit board and the water cooling jacket are brought into close contact with each other.

  Since the power module according to the present invention uses a silicon nitride sintered body as an insulating substrate, it has higher heat dissipation and higher strength characteristics than a resin or the like. When the substrate and the water cooling jacket are brought into close contact with each other, even if pressure is applied to the extent that the water cooling jacket is depressed by the lower surface of the insulating substrate, cracking does not occur in the insulating substrate, so that more stable heat dissipation can be achieved.

  In the power module of the present invention, the circuit board has a gentle convex curved surface from the outer periphery of the lower surface to the center of the lower surface, so that it is easy to follow when the water-cooling jacket is depressed, and the adhesion is improved and the flow path is improved. Since the deformation of the flow rate becomes gentle, the flow velocity resistance of the cooling water becomes small, and the heat dissipation can be further improved by facilitating the flow of the cooling water.

  In the power module of the present invention, since the upper surface of the circuit board is flat, heat generated from the electronic component can be more effectively transmitted to the circuit board.

  Next, the power module of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of an example of an embodiment of a power module of the present invention. As shown in FIG. 1, 1 is an electronic component, 2 is a circuit board, 2a is an electric circuit board which is a part on the upper surface side of the circuit board 2, 2b is an insulating board which is a part on the lower surface side of the circuit board 2, It is a water cooling jacket for cooling the circuit board 2.

  The electronic component 1 is an element such as a MOS (Metal Oxide Semiconductor) or an IGBT (Insulated Gate Bipolar Transistor).

  In the electric circuit board 2a on the upper surface side of the circuit board 2, for example, metal circuit boards 11 and 12 are brazed to the upper and lower surfaces of the rectangular ceramic substrate 10 via an active metal brazing material. The ceramic substrate 10 acts as a support member for supporting the metal circuit boards 11 and 12, and is formed of, for example, a silicon nitride sintered body.

  A silicon nitride sintered body is made by mixing an appropriate organic binder, a plasticizer, and a solvent with raw material powders such as silicon nitride, aluminum oxide, magnesium oxide, yttrium oxide, etc., to form a slurry, and the slurry is conventionally known as a doctor blade. The ceramic green sheet (ceramic green sheet) is formed by adopting the method and calender roll method, and then the ceramic green sheet is punched appropriately to obtain a predetermined shape, and multiple sheets are laminated as necessary. Then, it is manufactured by firing at a high temperature of 1600 to 2000 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere.

  Since the ceramic substrate 10 made of this silicon nitride sintered body has a very high heat transfer coefficient of 60 W / m · K or more, the electronic component 1 mounted and fixed on the metal circuit board 11 generates heat during operation. Even so, the heat is efficiently dissipated to the outside through the ceramic substrate 10. As a result, the electronic component 1 is not heated to a high temperature by the heat, and the electronic component 1 is always operated at a suitable temperature in a stable and reliable manner. Can do.

  The ceramic circuit board 10 has metal circuit boards 11 and 12 attached to the upper and lower surfaces of the ceramic circuit board 10 through active metal brazing material. The active metal brazing material is used to join the ceramic circuit board 10 and the metal circuit boards 11 and 12 together. For example, titanium, tungsten, brazing material made of silver brazing material (silver: 72% by weight, copper: 28% by weight), aluminum brazing material (aluminum: 88% by weight, silicon: 12% by weight), etc. It is formed by adding 2 to 5% by weight of at least one of hafnium and / or its hydride.

  The attachment of the metal circuit boards 11 and 12 to the ceramic substrate 10 by the active metal brazing material is performed by placing the metal circuit boards 11 and 12 on the ceramic substrate 10 with the active metal brazing material sandwiched therebetween, and thereafter Is heated in vacuum or in a reducing atmosphere at a predetermined temperature (about 900 ° C. for silver brazing material, about 600 ° C. for aluminum brazing material) to melt the active metal brazing material and the ceramic substrate 10 and the metal circuit. This is done by joining the plates 11 and 12 together.

  Further, the metal circuit boards 11 and 12 attached to the ceramic substrate 10 through the active metal brazing material are made of a metal material such as copper or aluminum, and are rolled or punched into ingots (lumps) such as copper or aluminum. By applying a conventionally known metal processing method such as a method, for example, a thickness of 500 μm is produced in a predetermined pattern shape.

  When the metal circuit boards 11 and 12 are made of copper, if the metal circuit board is made of oxygen-free copper, the oxygen-free copper is oxidized by the oxygen present in the copper during brazing. As a result, the wettability with the active metal brazing material is improved, and the bonding to the ceramic substrate 10 through the active metal brazing material is strengthened. Therefore, the metal circuit board is preferably formed of oxygen-free copper.

  Such metal circuit boards 11 and 12 are first joined to the upper and lower surfaces of the ceramic substrate 10 with a metal plate such as a copper plate or an aluminum plate to be the metal circuit boards 11 and 12 through an active metal brazing material. An etching resist is printed on the surface of the metal plate in a predetermined circuit shape. And, using an etching solution such as ferric chloride or cupric chloride by an etching apparatus, spraying the etching solution on the surface of the metal plate from above and below to dissolve unnecessary metal parts to form a circuit, After completion of the etching, circuit-like metal circuit boards 11 and 12 are formed by a method of removing an etching resist applied to the metal circuit portion using an alkali solution such as sodium hydroxide.

  Further, when a metal circuit board having a good conductivity made of nickel and having good corrosion resistance and wettability with an active metal brazing material is deposited by plating, the metal circuit boards 11 and 12 are formed. Corrosion resistance can be improved, and electronic components, heat sinks, and the like can be firmly bonded to the metal circuit boards 11 and 12 via solder. Therefore, it is preferable that the metal circuit boards 11 and 12 have a metal surface having good conductivity made of nickel and having good corrosion resistance and wettability with the active metal brazing material deposited by plating.

  Further, when a plating layer made of nickel is deposited on the surfaces of the metal circuit boards 11 and 12, the surface oxidation of the plating layer made of nickel can be achieved by containing 8 to 15% by weight of phosphorus inside and forming an amorphous alloy of nickel-phosphorus. Can be prevented well and wettability with the active metal brazing material can be maintained for a long time. Therefore, when a plating layer made of nickel is deposited on the surfaces of the metal circuit boards 11 and 12, it is preferable to contain 8 to 15% by weight of phosphorus inside to form a nickel-phosphorus amorphous alloy.

  When a plating layer made of a nickel-phosphorus amorphous alloy is applied to the surfaces of the metal circuit boards 11 and 12, the nickel-phosphorus amorphous when the phosphorus content relative to nickel is less than 8% by weight or more than 15% by weight. It is difficult to form an alloy, and it is difficult to firmly bond the solder to the plating layer.

  In the case where a plating layer made of an amorphous alloy of nickel-phosphorous is applied to the surfaces of the metal circuit boards 11 and 12, the plating layer made of nickel applied to the surfaces of the metal circuit boards 11 and 12 also has a thickness. When the thickness is less than 1.5 μm, it becomes difficult to cover the entire surface of the metal circuit boards 11 and 12 with a plating layer made of nickel, and it becomes difficult to effectively prevent the oxidative corrosion of the metal circuit boards 11 and 12. On the other hand, if the thickness exceeds 3 μm, the internal stress inside the plating layer made of nickel becomes large, and the ceramic substrate 1 is likely to be warped or cracked. In particular, when the thickness of the ceramic substrate 1 is as thin as 700 μm or less, warpage, cracking, and the like of the ceramic substrate 1 are likely to be remarkable. Therefore, it is preferable that the plating layer made of nickel deposited on the surfaces of the metal circuit boards 11 and 12 has a thickness in the range of 1.5 μm to 3 μm.

  The insulating substrate 2b is preferably bonded to the lower surface of the ceramic substrate 10 via the metal circuit board 12. As a result, while the electric circuit board 2a on the upper surface side of the circuit board 2 is maintained in a flat plate structure, only the shape of the insulating substrate 2b can have a structure in which the center portion of the lower surface protrudes. Therefore, the electric circuit board 2a is less likely to be distorted, and the stress applied to the electric circuit board 2a when the circuit board 2 and the water cooling jacket 3 are brought into close contact with each other is reduced, so that the reliability of the electric circuit board 2a can be improved.

  In FIG. 1, the metal circuit layer 12 is a plate-like body bonded to the entire lower surface of the insulating substrate 2b. With such a configuration, the bonding strength between the metal circuit layer 12 and the insulating substrate 2b can be increased, and the heat transferred from the electronic component 1 to the circuit substrate 2 can be efficiently radiated to the water cooling jacket 3.

  For example, a rectangular ceramic plate is used as the insulating substrate 2b. This ceramic substrate is formed of, for example, a silicon nitride-based sintered body. The silicon nitride sintered body is manufactured in the same manner as the ceramic substrate 10 of the electric circuit board 2a.

  Further, in FIG. 1, the central portion is thicker than the peripheral portion so that the central portion of the lower surface of the insulating substrate 2b protrudes below the outer peripheral portion of the lower surface. As described above, as a method of manufacturing the central portion of the insulating substrate 2b so as to be thicker than the peripheral portion, polishing is performed by lapping, grinding, etc., and the central portion is thickened by pressing at the stage of the ceramic green sheet. There are a method of forming, and a method of forming a plurality of ceramic green sheets having different sizes in a stage of a ceramic green sheet or a state of a ceramic substrate after firing, or forming a stepped shape by superposing ceramic substrates.

  And the circuit board 2 which the lower surface center part protruded below the lower surface outer peripheral part by overlapping the insulating substrate 2b under the electric circuit board 2a. The electric circuit board 12 and the insulating board 2b may be in contact with each other, or the electric circuit board 12 and the insulating board 2b may be joined with an active metal brazing material or the like.

  The water cooling jacket 3 is made of a metal having excellent thermal conductivity, such as aluminum, and is hollow so that the refrigerant flows inside. For example, a hose capable of allowing a coolant to flow, for example, is attached to the open holes at both ends of an aluminum block that has a hollowed-out cylindrical hole or a plurality of through-holes. It has a port for it.

  The power module of the present invention is composed of a combination of the above components, and the connection method is as follows. Solder bonding is performed in a reducing atmosphere of about 230 ° C. to 350 ° C. with a solder paste printed or solder foil placed on a predetermined place on the metal circuit board 11 of the electric circuit board 2a and the electronic component 1 placed thereon. If necessary, the terminal of the electronic component 1 and the metal circuit board 11 are electrically joined with a bonding wire or the like.

  Next, the surface of the electric circuit board 2a on which the electronic component 1 is not mounted is placed on the water cooling jacket 3 via the insulating board 2b. At this time, the insulating substrate 2b has a central convex surface on the side of the water cooling jacket 3, and the electric circuit substrate 2a is placed between the electric circuit substrate 2a, the insulating substrate 2b, and the water cooling jacket 3 when mounted. In order to prevent an air layer from being formed by the undulations on the surfaces of the insulating substrate 2b and the water cooling jacket 3, and to prevent the heat dissipation from being disturbed, silicon grease or the like is preferably applied to a thickness of about 100 μm.

  When the electric circuit board 2a on which the electronic component 1 is mounted is joined to the water cooling jacket 3 via the insulating board 2b, a load is applied between the circuit board 2 and the water cooling jacket 3, and the convex portion at the center of the circuit board 2 is applied. By deforming the water cooling jacket 3, the flow path of the water cooling jacket 3 in the central portion of the circuit board 2 is narrowed, so that the flow velocity of that portion is increased and the power module can improve heat dissipation. Can do.

  And as a means for projecting the lower surface center part of the circuit board 2 below the lower surface outer peripheral part, it is possible to have a shape projecting by a step, but rather than projecting by such a step, the circuit board lower surface It is better to have a gentle convex curved surface from the outer peripheral part to the lower surface center part. This makes it easier to follow when the water-cooling jacket is recessed and improves adhesion, and the flow path is also gently deformed, so the flow rate resistance of the cooling water is reduced and the cooling water is easier to flow, improving heat dissipation. Can be made.

  In addition, the shape in which the center part of the lower surface of the circuit board 2 protrudes below the outer peripheral part of the lower surface is not limited to the method of manufacturing the central part of the insulating substrate 2b so as to be gently thicker than the peripheral part. . For example, the electric circuit board 2a may be brought into contact with the water cooling jacket 3 so that the lower surface center portion of the electric circuit board 2a protrudes downward without using the insulating substrate 2b. In this case, the metal circuit board 12 is brought into contact with the water-cooling jacket 3 so that the lower surface central portion of the metal circuit board 12 joined to the lower surface of the electric circuit board 2a protrudes downward, or the electric circuit board 2a. The ceramic plate 10 may be brought into direct contact with the water-cooling jacket 3 so that the center portion of the lower surface of the ceramic plate 10 protrudes downward.

  Further, the surface of the circuit board 2 that is in contact with the electronic component 1 is in contact with the electronic component 1 of the circuit board 2 in order to efficiently transfer the heat generated from the electronic component 1 to the water cooling jacket 3 through the circuit board 2. The side surface is preferably a flat surface.

  Note that the present invention is not limited to the above-described best mode, and various modifications can be made without departing from the scope of the present invention. For example, the ceramic substrate 10 constituting the electric circuit substrate 2a may be a resin substrate.

It is sectional drawing which shows an example of embodiment of the power module of this invention. It is sectional drawing which shows the conventional power module.

Explanation of symbols

1: Electronic component 2: Circuit board 2a: Electric circuit board 2b: Insulating board 3: Water-cooled jacket

Claims (5)

In a power module comprising: a circuit board having an electronic component placed on the center of the upper surface; and a water cooling jacket that is in contact with the lower surface of the circuit board and has a flow path for flowing cooling water directly under the contact portion The center portion of the lower surface of the circuit board protrudes below the outer peripheral portion of the lower surface, and the portion of the water cooling jacket that contacts the circuit board is recessed toward the flow path along the lower surface of the circuit board. A featured power module. The power module according to claim 1, wherein the lower surface side portion of the circuit board is made of an insulating substrate. The power module according to claim 2, wherein the insulating substrate is made of a silicon nitride sintered body. The power module according to any one of claims 1 to 3, wherein the circuit board has a gently convex curved surface from a lower surface outer peripheral portion to a lower surface central portion. The power module according to claim 1, wherein an upper surface of the circuit board is flat.

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