JP2012190950A - Conductive pattern member for substrate for power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive pattern member for a substrate for a power module which obtains strong adhesiveness between a ceramic substrate and a conductive pattern layer and improves assembly workability.SOLUTION: A conductive pattern member 10 is formed by tentatively fixing a conductive pattern layer 6 to a brazing material foil 9 in the lamination state. Multiple welded portions 12, formed by welding the brazing material foil 9 on a surface of the conductive pattern layer 6, are provided so as to be located along at least two facing sides of an outer periphery of the conductive pattern layer 6 or located at end parts of the two sides.

Description

  The present invention relates to a conductor pattern member used for manufacturing a power module substrate used in a semiconductor device that controls a large current and a large voltage.

  As a conventional power module, a metal layer forming a conductor pattern layer is laminated on one surface of a ceramic substrate, and an electronic component such as a semiconductor chip is soldered on the conductor pattern layer, and the other side of the ceramic substrate A structure in which a metal layer to be a heat dissipation layer is formed on the surface and a heat sink is bonded to the heat dissipation layer, or a structure in which an aluminum heat sink is directly bonded to a ceramic substrate without providing a metal layer to be a heat dissipation layer Power modules are known. In a power module substrate used in this type of power module, a metal layer is joined to the surface of the ceramic substrate by soldering or brazing.

For example, in Patent Document 1, the brazing material foil is temporarily fixed to the surface of the ceramic substrate by the surface tension of the volatile organic medium, and the conductor pattern layer punched from the base material is temporarily fixed to the surface of the brazing material foil. Is heated to form a power module substrate.
In Patent Document 2, a plurality of protrusions are formed on the surface of the active metal brazing paste layer, and a conductor pattern layer (metal plate) is placed on the active metal brazing paste layer via the protrusions. The ceramic substrate and the conductor pattern layer are joined by heating in a non-oxidizing atmosphere. Until the active metal brazing paste layer is melted, the conductive pattern layer is disposed through the protrusions. Therefore, even if the conductive pattern layer thermally expands when the temperature rises, the active metal brazing paste on the ceramic substrate It is disclosed that bonding can be performed with high positional accuracy without being dragged to the conductor pattern layer and protruding outside.

Japanese Patent No. 4311303 Japanese Patent No. 3954912

  However, in the method for manufacturing a power module substrate described in Patent Document 1, when the brazing material foil and the conductor pattern layer are temporarily fixed to the ceramic substrate, the brazing material foil and the conductor pattern layer are misaligned. Are likely to be bent. In this case, the brazing material directly under the conductor pattern layer may be insufficient locally, and strong bondability may not be obtained. Also in Patent Document 2, not only is it difficult to manage the viscosity of the active metal brazing paste, but also the position of the paste tends to occur because the conductor pattern layer is placed at the paste application position.

  The present invention has been made in view of such circumstances, and it is possible to obtain a strong bondability between a ceramic substrate and a conductor pattern layer, and to improve assembly workability. A conductor pattern member is provided.

A conductor pattern member for a power module substrate of the present invention is formed by temporarily fixing a conductor pattern layer and a brazing material foil in a laminated state, and welding the brazing material foil to the surface of the conductor pattern layer. A plurality of welded portions are provided so as to be positioned along at least two opposite sides of the outer edge of the conductor pattern layer or at end portions of the two sides.
Since the conductor pattern layer and the brazing material foil are integrated by welding, the conductor pattern layer and the brazing material foil are not displaced in the subsequent lamination process or joining process, and the assembly workability can be improved. In addition, a plurality of welds are provided so as to be positioned along at least two opposite sides of the outer edge of the conductor pattern member or at the end portions of the two sides, and the conductor pattern layer and the brazing material foil are welded. The brazing foil is not easily turned or bent, and as a result, the brazing foil can be spread over the entire surface. Thereby, a ceramic substrate and a conductor pattern layer can be joined firmly.

In the conductor pattern member for a power module substrate of the present invention, the weld portion may be formed so as to overlap two opposite sides of the outer edge of the conductor pattern layer.
Since the conductor pattern layer and the brazing material foil are welded at the outer edge, it is possible to reliably prevent the brazing material foil from being turned over or bent.

In the conductor pattern member for a power module substrate of the present invention, the welded portion may be formed in a linear shape along the two sides.
Since the range of a welding part can be made comparatively long, a conductor pattern layer and brazing material foil can be joined reliably.

In the conductor pattern member for a power module substrate of the present invention, the welded portion may be formed so as to overlap at least a corner portion of the outer edge of the conductor pattern layer.
By welding the corners, the brazing foil can be surely prevented from being bent or bent even when the welds are locally scattered.

  The method for manufacturing a power module substrate of the present invention is a method for manufacturing a power module substrate in which a conductor pattern layer is formed on at least one surface of a ceramic substrate, and the conductor pattern member and the ceramic substrate described above are laminated. It has a lamination process, and the joining process of carrying out brazing by heating in the state which pressed the conductor pattern member and the said ceramic substrate, It is characterized by the above-mentioned.

  According to the present invention, by assembling the conductor pattern layer and the brazing material foil as a conductor pattern member, the assembly workability of the power module substrate can be improved, and the conductor pattern layer and the ceramic substrate can be improved. In the meantime, it is possible to prevent the brazing material foil from being turned over or bent, and to join them firmly.

It is a figure explaining the conductor pattern member for the board | substrate for power modules of 1st Embodiment of this invention, (a) is a front view, (b) is a longitudinal cross-sectional view. It is a figure explaining the manufacturing method of the conductor pattern member of 1st Embodiment of this invention. It is the schematic which shows the joining apparatus of brazing material foil. It is a principal part enlarged view of the ultrasonic welding machine which is a part of apparatus shown in FIG. It is a side view of the power module using the conductor pattern member of this invention. It is a figure explaining the continuous welding part which is scattered. It is a figure explaining the manufacturing method of the conductor pattern member of 2nd Embodiment of this invention. It is a figure explaining the conductor pattern member of other embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 5 shows a power module 1 manufactured using a conductor pattern member for a power module substrate manufactured according to the present invention. The power module 1 is joined to a power module substrate 3 having a ceramic substrate 2 made of ceramics, an electronic component 4 such as a semiconductor chip mounted on the surface of the power module substrate 3, and the power module substrate 3. The heat sink 5 is made up of.

  The power module substrate 3 is configured such that the conductor pattern layer 6 is disposed on the upper surface side of the ceramic substrate 2 and the heat radiation layer 7 is disposed on the lower surface side. The conductor pattern layer 6 and the heat dissipation layer 7 are both formed of pure aluminum or an aluminum alloy. The conductor pattern layer 6 and the heat dissipation layer 7 are brazed to the ceramic substrate 2 with an Al—Si or Al—Ge brazing material foil. The electronic component 4 is joined to the upper surface of the conductor pattern layer 6 via the solder layer 8. Further, a heat sink 5 is disposed on the lower surface of the heat dissipation layer 7 so that heat from the electronic component 4 can be dissipated to the outside through the heat sink 5.

  As shown in FIG. 1, the power module substrate 3 is a conductor pattern in which a part of the conductor pattern layer 6 and the brazing material foil 9 is temporarily fixed in advance, and the conductor pattern layer 6 and the brazing material foil 9 are integrated. The member 10 is formed, and the conductor pattern member 10 and the ceramic substrate 2 are joined via the brazing material foil 9. The conductor pattern layer 6 and the brazing material foil 9 are temporarily fixed by the brazing material foil joining apparatus 100 shown in FIG.

The joining apparatus 100 includes a feeding device 110 that is a traveling unit that travels in a state where the strip-shaped brazing material foil 90 is overlapped on the strip-shaped base material 60 that becomes the conductor pattern layer 6, and the base material 60 and the brazing material foil 90. An ultrasonic welding machine 120 which is a welding means for ultrasonic seam welding and a press working machine 130 which is a pressing means for punching the base material 60 together with the brazing material foil 90 along the outline of the conductor pattern layer 6 are provided.
Also, reference numerals 140, 150, 160, and 170 in FIG. 3 denote a base material supply device 140 that supplies a base material wound in a coil shape, a cleaning device 150 that cleans the supplied base material 60, and a base material 60, respectively. 1 shows a leveler 160 for smoothing and a brazing material foil supply device 170 for supplying a brazing material foil 90.

  As shown in FIG. 4, the ultrasonic welder 120 includes a pair of disk-shaped horns 21 connected to vibrators 22 that generate ultrasonic vibrations, and a base material placed on a stage 23. By moving the horn 21 in contact with the brazing material foil 90 on the line 60, the linear welded portion 12 (see FIG. 2) can be formed.

The horn 21 and the vibrator 22 are supported by a ball screw mechanism having ball screw shafts 24a and 25a and slide units 24b and 25b screwed to the ball screw shafts 24a and 25a so as to be movable in the horizontal direction.
Specifically, a pair of slide units 25b are movably attached to a ball screw shaft 25a extending in the running direction of the base material 60, and each slide unit 25b is perpendicular to the ball screw shaft 25a (the width of the base material 60). A ball screw shaft 24a extending in the direction) is attached, and a slide unit 24b is movably attached to each of the ball screw shafts 24a.
One end of each of the ball screw shafts 24a and 25a is connected to an individual moving motor (not shown). When each moving motor is rotated, the ball screw shafts 24a and 25a rotate, and accordingly, the slide unit. 24b and 25b move in the axial direction of the ball screw shafts 24a and 25a.
The ball screw shaft 25a is formed of a left and right threaded part a1 and a right threaded part a2 with a male threaded part formed as a left and right reverse thread with a central part as a boundary. The slide units 25b provided on both sides of the ball screw shaft 25a are guided by the male screw portions a1 and a2 of the ball screw shaft 25a and move symmetrically.
A vibrator 22 is attached to each slide unit 24b. A disk-shaped horn 21 is connected to each of the vibrators 22, and these horns 21 are arranged in parallel to the direction perpendicular to the traveling direction. 21 is moved on the stage 23 by the slide unit 24b while being in contact with the brazing material foil 90 on the base material 60, so that the two linear welds 12 can be connected to the base material 60 and the brazing material foil at a time. It can be formed along 90 width directions.

  In the stage 23, the upper surface portion on which the base material 60 is placed is formed in a convex arc shape with a curvature along the traveling direction of the base material 60 and the brazing material foil 90, and vertically moved by a lifting mechanism such as a cylinder. It can be configured to be raised to a predetermined position where the upper surface of the brazing foil 90 and the horn 21 are brought into contact with each other. Further, at the front and rear positions of the position where the pair of horns 21 are arranged, there are provided work holders 26 for holding the overlapped belt-like base material 60 and brazing material foil 90 between the stage 23. . A holding means for holding the base member 60 and the brazing filler metal foil 90 along the surface of the stage 23 is configured by the work presser 26 and the lifting mechanism of the stage 23.

Further, as shown in FIG. 2, the press machine 130 welds the base material 60 and the brazing material foil 90, then forms pilot holes 13 at both ends of the welded portion 12, and uses the pilot holes 13 as guides. The base material 60 is punched out together with the brazing material foil 90.
The pilot hole 13 is formed at the end of the welded portion 12 so as to overlap at least a part of the welded portion 12 along the width direction. Further, as will be described later, the punching punch 131 is configured to integrally punch the base material 60 and the brazing material foil 90 so that the welded portion 12 overlaps a part of the outline.

  The method of manufacturing the power module substrate 3 using the brazing material foil joining apparatus 100 configured as described above is a pattern in which the conductive pattern layer 6 and the brazing material foil 9 are temporarily fixed in a laminated state and the conductive pattern member 10 is punched out. It comprises a forming step, a laminating step for laminating the conductor pattern member 10 and the ceramic substrate 2 so that the brazing material foil 9 is interposed, and a joining step for brazing the laminated laminate.

  In the pattern forming step, the conductor pattern member 10 is formed using the bonding apparatus 100 described above. First, as shown in FIG. 3, the belt-like base material 60 and the brazing material foil 90 are supplied from the supply devices 140 and 170, and the base material 60 and the brazing material foil 90 are caused to travel to a predetermined position by the feeding device 110. They are placed in a state of being stacked on the stage 23. The travel of the feeding device 110 is stopped and the stage 23 is raised, whereby the base material 60 and the brazing material foil 90 are held between the stage 23 and the work presser 26. Since the upper surface portion of the stage 23 is formed in a convex arc shape, the base material 60 and the brazing filler metal foil 90 are held in close contact with each other while warping upward along the upper surface portion.

Reference numeral 11 indicated by a two-dot chain line in FIG. 2 indicates an outline of the conductor pattern layer 6 to be formed. By adjusting the distance between the pair of horns 21 to the distance along the width direction of the outline 11, the stage 23 is raised, and the substrate 60 and the brazing material foil 90 that are the workpieces are raised to a predetermined position. In this state, the horn 21 can be welded while being held in a convex arc shape.
At this time, the horn 21 is ultrasonically vibrated by the vibrator 22 and moved from one end to the other end in the width direction of the substrate 60 while rotating the horn 21, so that a linear shape as shown in FIG. Two welds 12 are formed at a time in the running direction (arrow A) at intervals. In addition, the joining width of these welding parts 12 is about 0.5-1.0 mm. Then, when the welding is completed, the stage 23 is lowered, and the base material 60 and the brazing material foil 90 are caused to travel again for a predetermined distance.
Thus, the base material 60 and the brazing material foil 90 in an overlapped state are repeatedly run and stopped intermittently by the feeding device 110, and the base material 60 and the brazing material foil 90 are intermittently welded.

The welded base material 60 and the brazing filler metal foil 90 are moved in the running direction by the feeding device 110 and are overlapped with at least a part of the welded portion 12 at the end in the width direction in the next press machine 130. Then, the pilot hole 13 is opened. Then, using the pilot hole 13 as a guide, the base material 60 and the brazing material foil 90 are simultaneously punched along the contour line 11 of the conductor pattern layer.
The base material 60 and the brazing material foil 90 are punched out in a state where they are joined at the welded portion 12. As described above, the distance between the pair of horns 21 is matched to the distance between the outlines 11 along the width direction of the substrate 60 among the outlines 11 of the conductor pattern layer. Conductive pattern member 10 is formed with the outer edge along outer line 11 in the width direction being welded.

Here, the manufacturing method of the board | substrate for power modules using this conductor pattern member 30 is demonstrated.
As described above, the conductor pattern layer 6 and the heat dissipation layer 7 made of the conductor pattern member 10 formed in the pattern forming step are laminated by brazing the ceramic substrate 2 with the brazing material foil 90 interposed, and a joining step for brazing. After that, it is bonded to the ceramic substrate 2.
Specifically, a laminated body in which the conductive pattern member 10 is laminated on the front and back surfaces of the ceramic substrate 2 with a brazing material foil 90 having a thickness of 15 μm, and a sheet made of carbon and graphite thin films having cushioning properties and heat resistance. Are alternately stacked in the stacking direction and stacked between pressurizing means, and these are charged in a vacuum furnace in a state of being pressurized in the thickness direction (stacking direction) with a load of 50 to 500 kPa. And by heating to 600-650 degreeC in this pressurization state, the ceramic substrate 2, the conductor pattern layer 6, and the thermal radiation layer 7 are soldered, and the board | substrate 3 for power modules is manufactured.
In this case, both ends (outer edges) of the outer shape of the conductor pattern member 10 are welded. Therefore, the conductor pattern layer 6 and the heat radiation layer 7 and the brazing filler metal foil 9 are not displaced in the subsequent laminating process and bonding process, and the assembly workability can be improved.

  A plurality of welds 12 are formed on the outer edge of the conductor pattern member so as to be positioned along at least two opposing sides of the outline 11 or at the ends of the two sides. In the front view of the conductor pattern 10 in FIG. 1A, these welds 12 are formed so as to be located at the ends of the two opposite sides 12a on the upper side and the two opposite sides 12b on the lower side. In other words, curling of the brazing material foil and bending are less likely to occur. As a result, it is possible to spread the brazing material foil over the entire surface of the laminated surface. Thereby, the ceramic substrate 2 and the conductor pattern layer 6 can be firmly joined.

  In the above-described series of power module substrate manufacturing methods, since the base material 60 and the brazing filler metal foil 90 are welded at intervals in the traveling direction, when continuously welding along the traveling direction. In comparison, the brazing material foil 90 is less likely to be wrinkled at the welded portion 12. In addition, the base material 60 and the brazing filler metal foil 90 are overlapped with each other by being bent into a convex arc shape, and the two welds 12 are formed at the same time, so that the generation of wrinkles can be further suppressed.

  In addition, the pilot hole 13 is opened as a guide during press working. However, since the punched material can be processed in one piece without being separated at the base material 60 and the brazing material foil 90, post-processing of the punched material is easy. In addition, it is possible to prevent the portion of the brazing material foil 90 from being mixed during pressing and damaging the conductor pattern layer 6.

  In addition, in the pattern formation process of the above-mentioned 1st Embodiment, although the base material 60 and the brazing material foil 90 were welded linearly, as shown in FIG. It is also possible to configure a configuration in which the dotted continuous welds 14 are configured and temporarily fixed. In this case, wrinkles generated in the brazing material foil can be further reduced as compared with the linear welded portion.

  FIG. 7 is a diagram for explaining a method for producing a conductor pattern member according to the second embodiment of the present invention. In the pattern forming process of the first embodiment described above, the base material 60 and the brazing filler metal foil 90 are welded in a linear shape. However, as in the second embodiment shown in FIG. It is good also as a structure which overlaps and forms the dotted | punctate welding part 15 on the corner | angular part of the outline 11 of the conductor pattern layer 6, and fixes the conductor pattern layer 6 and the brazing material foil 9 temporarily. In this case, it is good to weld the halfway position of the side to the place where the side of outline 11 is long. Moreover, although the welding part 15 may perform ultrasonic welding for every point, it is preferable to weld many points simultaneously.

In this way, by welding the corners of the outline 11, even when the welded portions 15 are locally scattered, the brazing foil can be reliably prevented from being turned up or bent. Further, as in the first embodiment shown in FIG. 2, the brazing material foil is less likely to be wrinkled in the welded portion 15 as compared with the case where the linearly welded portion 12 is provided.
Moreover, although it is suitable to form the welding part 15 including the sharp tip of the corner | angular part of the outline 11, if the distance L1 from a sharp tip is small like the conductor pattern member 30 shown to Fig.8 (a). Further, since the brazing of the brazing material foil is difficult to occur, it may be formed away from the tip, like the welded portion 16 of the conductor pattern member 30. Further, when the linear welded portion 17 is provided as in the conductor pattern member 40 shown in FIG. 8B, the end portion (outer edge) along the outer shape is welded if the distance L2 from the outer shape is small. Even without it, the brazing foil is not easily turned over. Therefore, like the welding part 17 of the conductor pattern member 40, it may be formed away from the outer edge.
Other configurations are the same as those of the first embodiment, and the same reference numerals are given to common portions, and descriptions thereof are omitted.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the welded portion of the base material and the brazing material foil is provided not only on the conductor pattern outline, but also in other parts (for example, the central part) in addition to the welded part on the outline as in the above-described embodiment. It is good.
Further, the welding of the base material and the brazing material foil is not limited to ultrasonic welding, and welding by laser welding or the like is also possible.

DESCRIPTION OF SYMBOLS 1 Power module 2 Ceramic substrate 3 Power module substrate 4 Electronic component 5 Heat sink 6 Conductive pattern layer 7 Heat radiation layer 8 Solder layer 9 Brazing material foil 10, 30, 40 Conductive pattern member 11 Outline line of conductive pattern layer 12, 14, 15 , 16, 17 Welded part 13 Pilot hole 21 Horn 22 Vibrator 23 Stage 24a, 25a Ball screw shaft 24b, 25b Slide unit 26 Workpiece presser 60 Base material (band shape)
90 Brazing foil (band)
DESCRIPTION OF SYMBOLS 100 Joining apparatus of brazing filler metal 110 Feeding apparatus 120 Ultrasonic welding machine 130 Press processing machine 131 Punch punch 140,170 Supply apparatus 150 Cleaning apparatus 160 Leveler

Claims (5)

  A conductive pattern layer and a brazing material foil are temporarily fixed in a laminated state, and a weld formed by welding the brazing material foil to the surface of the conductive pattern layer is at least opposite to an outer edge of the conductive pattern layer. A plurality of conductor pattern members for a power module substrate, the plurality of conductor pattern members being provided so as to be positioned along two sides or at end portions of the two sides.   2. The conductor pattern member for a power module substrate according to claim 1, wherein the weld is formed so as to overlap two opposite sides of the outer edge of the conductor pattern layer.   The conductor pattern member for a power module substrate according to claim 1, wherein the welded portion is formed in a linear shape along the two sides.   The conductor pattern member for a power module substrate according to claim 1, wherein the welded portion is formed so as to overlap at least a corner portion of the outer edge of the conductor pattern layer.   A method for manufacturing a power module substrate in which a conductor pattern layer is formed on at least one surface of a ceramic substrate, wherein the conductor pattern member according to any one of claims 1 to 4 and the ceramic substrate are stacked. A method for manufacturing a power module substrate, comprising: a step of joining together by brazing by heating the conductive pattern member and the ceramic substrate in a pressurized state.

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