JP4256282B2 - Heat sink material manufacturing method and heat sink ceramic package - Google Patents

Description

The present invention relates to a method for manufacturing a heat sink material and a ceramic package with a heat sink.

  Conventionally, Cu—W composite materials and Cu—Mo composite materials have been used for heat sinks for electronic components. The Cu—W composite material is obtained by impregnating a sintered body of W powder with molten Cu and rolling it. The Cu—Mo composite material is obtained by impregnating molten Cu with a molten Cu powder and rolling it. A clad material (so-called CMC clad material) obtained by rolling a Mo plate between a pair of Cu plates is also used. The CMC clad material is excellent in thermal conductivity with other parts because the surface layer portion is Cu, but has a weakness that the workability is low because the inner layer portion made of Mo is brittle.

On the other hand, recently, a composite clad material (so-called CPC clad material) obtained by rolling a Cu-Mo composite between a pair of Cu plates has been provided (Patent Document 1 below). This CPC clad material is excellent in both properties of workability and thermal conductivity, and therefore the demand is expanding.
JP 2001-358266 A

  When manufacturing a ceramic package with a heat sink for mounting a semiconductor chip using the heat sink material as described above, a heat sink molded (cut) to a predetermined size and a separately prepared ceramic package are brazed with an Ag brazing material or the like To do. Also, when a semiconductor chip is mounted on a ceramic package with a heat sink, as shown in FIG. 1, the semiconductor chip is brazed with Au—Sn brazing material or the like directly on the heat sink or via a Cu thin plate or the like. There is a problem that the heat sink is warped due to the thermal history during the brazing process.

  In Patent Document 1, the warp generated in the heat sink is reduced by adjusting the thickness ratio between the upper and lower Cu plates and the Cu-Mo composite or by devising the rolling method of the Cu-Mo composite. Techniques to do this are disclosed. If the warp of the heat sink is small, it is easy to ensure the bonding strength between the ceramic package and the heat sink, and further the bonding strength between the semiconductor chip and the heat sink.

  By the way, while it is desired to reduce the warpage of the heat sink, there are users who have a desire to control the warping direction.

Accordingly, an object of the present invention is to provide a method of manufacturing a heat sink material that can control the direction of warping that occurs . It is another object to provide a ceramic package with a heat sink manufactured using the heat sink material.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-described problems, the present invention provides a heat sink material having a structure in which a Cu-Mo composite is interposed between a pair of Cu plates and bonded to each other, and the thickness between one Cu plate and the other Cu plate Assuming that

Since the above heat sink materials have different heat capacities, the heat sink material has a certain regularity in the warping direction when a ceramic package or a semiconductor chip is brazed. That is, the direction of warpage can be predicted in advance, and the direction of warpage can be positively controlled. In addition, since the thickness of one Cu plate and the other Cu plate is kept different, the problem of a decrease in thermal conductivity on the one surface side hardly occurs.

The heat sink material of the present invention can be manufactured as follows. That is, a heat sink material having a joint structure between a Cu-Mo composite and a Cu plate by rolling a Cu-Mo composite obtained by impregnating molten Cu into a Mo powder compact with a pair of Cu plates. In this method, one Cu plate is reduced in thickness after the rolling, and the thickness is different from that of the other Cu plate. When producing a clad material of a Cu-Mo composite and a Cu plate, the quality becomes unstable unless the Cu-Mo composite is sandwiched between Cu plates and rolled. Therefore, a method of reducing the thickness of one Cu plate after rolling as in the present invention is preferred.

  Further, as a specific method for making the thickness of one Cu plate different from the other Cu plate, a method of reducing the thickness of one Cu plate by polishing, grinding or etching can be shown. These methods have low technical difficulty and low cost. It can also contribute to managing a highly accurate plate thickness. In addition, the method of increasing the thickness of one Cu plate after the rolling and making the thickness different from that of the other Cu plate can be similarly adopted. As a specific method in that case, a method of forming a Cu film on the surface of one Cu plate by plating, vapor deposition, sputtering or the like can be shown. If it is a method of forming a plating film, you may make it form the plating film (what is called differential thickness plating) from which thickness differs.

In addition, a Cu-Mo composite is interposed between a pair of Cu plates and joined together, and a heat sink and a heat sink are configured so that the thicknesses of one Cu plate and the other Cu plate are different from each other. Among the pair of Cu plates, a ceramic package with a heat sink provided with a ceramic package brazed onto the main surface of the thick Cu plate can be provided. This ceramic package with a heat sink has a certain regularity in the warping direction. That is, the direction of warpage can be predicted in advance, and the direction of warpage can be positively controlled. In addition, since the thickness of one Cu plate and the other Cu plate is kept different, the problem of a decrease in thermal conductivity on the one surface side hardly occurs.

  In a preferred embodiment, the ceramic package can be brazed onto the main surface of the Cu plate adjusted to be thick among the Cu plates constituting the heat sink. If it does in this way, as shown to Fig.3 (a), the side which brazed the ceramic package 5 will become concave shape. Then, it becomes easy to screw the heat sink 3 to the support 20. In addition, the heat sink 3 and the support 20 are easily brought into close contact with each other by adjusting the tightening degree of the screw 21.

  The ceramic package is preferably composed of alumina ceramic, aluminum nitride ceramic or glass ceramic.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a high-frequency circuit component 100 used in a mobile communication base station or the like. The high-frequency circuit component 100 is obtained by mounting semiconductor chips 13 and 13 on a ceramic package 1 with a heat sink. The ceramic package 1 with a heat sink includes a heat sink 3 and a ceramic package 5 brazed on the main surface of the heat sink 3 with an Ag brazing material. The ceramic package 5 includes a package main body 11 having a frame shape and leads 7 and 9 attached to the package main body 11.

  The package body 11 is made of, for example, alumina ceramic, aluminum nitride ceramic, or glass ceramic. The leads 7 and 9 are made of a metal material such as Kovar or 42 alloy (both are trade names), and are brazed to the upper surface of the package body 11. The package body 11 is brazed to the heat sink 3 on the lower surface side. For such brazing, an Ag brazing material (a brazing material containing the most Ag among metal components) is used. The semiconductor chip 13 is mounted on the heat sink 3 in the cavity 11p of the ceramic package 5 directly or via a metal thin plate (Cu thin plate is preferable) having a thickness of about 300 μm. An Au-based brazing material (for example, Au—Sn brazing material) is used for mounting the semiconductor chip 13. The electrodes of the semiconductor chips 13 and 13 and the leads 7 and 9 are connected by bonding wires.

The heat sink 3 is made of a clad material (heat sink material) in which Cu plates 32 and 34 are placed above and below the Cu-Mo composite 30 and rolled, and the Cu-Mo composite 30 and the Cu plates 32 and 34 are joined to each other. It was produced. The heat sink 3 has a good thermal conductivity because the surface layer portion is made of Cu. As shown in FIG. 2, the thickness d ₁ (0.3 mm) of the first Cu plate 32 on the side where the ceramic package 5 is brazed is equal to the thickness d ₃ (0.1 mm) of the second Cu plate 34 on the opposite side. Is bigger than. The thickness _d 2 of the Cu-Mo complex 30 (1.5 mm) is greater than the sum of the thickness of the first Cu plate 32 _{d 1} and the thickness _{d 3} of the second Cu plate 34.

  By adopting such a ratio, it is possible to control the direction of warpage generated in the heat sink 3 when the ceramic package 5 or the semiconductor chip 13 is brazed. Specifically, the direction of the warp generated in the heat sink 3 can be controlled to be concave on the side where the ceramic package 5 is disposed (the side on which the semiconductor chip 13 is mounted). One reason for controlling the warping direction is as follows.

  The high-frequency circuit component 100 of FIG. 1 is used by being attached to a support body 20 (support substrate) with a fastening member 21 such as a screw or a bolt as shown in the schematic diagram of FIG. The screw holes and bolt holes are provided on the outer peripheral portion of the heat sink 3, avoiding the central portion where the semiconductor chip 13 is mounted. Therefore, the fastening member 21 presses the outer peripheral portion of the heat sink 3 toward the support 20. At this time, as shown in FIG. 3A, when the warp generated in the heat sink 3 is concave on the side where the ceramic package 5 is disposed, the warp is naturally corrected. Moreover, since the support body 20 and the heat sink 3 adhere | attach firmly, the heat conductivity from the heat sink 3 to the support body 20 is favorable.

  On the other hand, as shown in FIG. 3 (b), in the case of the heat sink 3 'in which the warping direction is not controlled and the arrangement side of the ceramic package 5 is convex, even if the fastening member 21 is tightened, the heat sink 3' and the support 20 A gap reflecting the warp of the heat sink 3 ′ is generated between the heat sink 3 ′ and the heat sink 3 ′ and the support 20 are not sufficiently adhered. The thermal conductivity from the heat sink 3 'to the support 20 is inferior to that of the present invention in FIG.

  The cause of the warp generated in the heat sink 3 in the brazing process is mainly due to the difference in thermal expansion coefficient from the ceramic package 5. The more homogeneous the material, the harder it is to predict whether the direction of warpage will be in the direction of FIG. 3 (a) or the direction of FIG. 3 (b). As described above, there is no problem even if some warping occurs in the direction of FIG. 3A, but it is not preferable that warping occurs in the direction of FIG. Therefore, it is not sufficient that the warp is small, and it is important to control the warp direction as in the present invention.

  Next, a method for manufacturing the heat sink 3 will be described. First, a Cu—Mo composite material is produced. As shown in FIG. 4, Mo powder is shape | molded by powder shaping | molding methods, such as CIP method, and the plate-shaped Mo powder molded object 40 is obtained. A Cu plate 42 is placed on the Mo powder compact 40 and both are heated in an inert atmosphere at a temperature exceeding the melting point of Cu (about 1300 ° C.) to impregnate the Mo powder compact 40 with the molten Cu. The preliminary composite 30 ′ thus obtained is rolled with a roller to obtain a Cu—Mo composite 30 configured as a rolled body. This rolling process is performed in biaxial directions (XY directions) orthogonal to each other. By rolling in the biaxial direction, a low thermal expansion coefficient close to that of ceramic can be realized. The primary rolling process is a hot working performed by heating the preliminary composite 30 ′ to about 200 ° C., and the secondary rolling process is a cold working performed by cooling to room temperature. Moreover, Cu content rate in the Cu-Mo composite 30 shall be 30 to 40 mass%, for example.

  Next, the first Cu plate 32 is disposed on one surface side of the Cu—Mo composite 30 and the second Cu plate 32 is disposed on the other surface side, and after performing a joint heat treatment, rolling is performed. The first Cu 32 and the second Cu plate 32 are the same (same thickness and material). In the bonding heat treatment, the laminate 44 of the Cu—Mo composite 30 and the Cu plates 32 and 32 is held in an inert atmosphere at about 800 ° C. for several tens of minutes. The rolling process after the bonding heat treatment is performed before the laminated body 44 reaches room temperature (hot rolling process).

  As described above, the rolled plate 50 ′ in which the Cu plates 32 and 32 having the same thickness on the front surface side and the back surface side of the Cu—Mo composite 30 are joined is produced. Next, a thickness reduction process for reducing the thickness of the Cu plate 32 on one surface side is performed on the rolled plate 50 '. Specifically, the thickness of the Cu plate 32 on one surface side is reduced by grinding (including blasting), polishing, chemical etching, or a combination thereof. The thickness D to be reduced can be, for example, not less than ½ and not more than 2/3 of the thickness of the Cu plate 32. In this way, it is possible to obtain the heat sink material 50 in which the thicknesses of the Cu plate 34 on one side subjected to the thickness reduction process and the Cu plate 32 on the other side are different. The heat sink 3 is obtained by punching the heat sink material 50 into a certain size.

  The heat sink 3 obtained by punching out the heat sink material 50 is subjected to surface polishing, deburring, and Cu plating. After the Ag brazing material is coated on the Cu plate 32 side (the non-thinned side) of the heat sink 3 manufactured in this way, the ceramic package 5 manufactured separately is placed and reflowed to obtain the ceramic package 1 with a heat sink. It is done.

  Incidentally, although the manufacturing method shown in FIG. 4 includes a step of reducing the thickness of the Cu plate 32 on one surface side, a step of increasing the thickness of the Cu plate 32 is performed instead of this thickness reduction step. You may do it. This thickening step can be a step of forming a Cu film on the surface of the Cu plate 32 by, for example, plating, vapor deposition, or sputtering. For example, the surface polishing process and the deburring process are performed on a punched product obtained by punching the rolled plate 50 ′ described in FIG. 4 into a predetermined size. Then, a dry film (plating resist) is adhered to one side of each of these punched products, and an electrolytic Cu plating process is performed. In this way, the heat sink 3 in which the thicknesses of the Cu plate 32 on one side and the Cu plate 34 on the other side are different can be easily manufactured.

  In addition, by preparing two types of Cu plates 32 and 34 having different thicknesses in advance and joining and rolling the Cu plates 32 and 34 having different thicknesses on the Cu-Mo composite 30, one surface side You may make it produce the heat sink 3 from which the thickness of the Cu plate 32 of this and the Cu plate 34 of the other surface side differ.

Sectional drawing of the ceramic package with a heat sink. The cross-sectional schematic diagram of a heat sink. The cross-sectional schematic diagram explaining the curvature of a heat sink. Manufacturing process explanatory drawing of a heat sink.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic package with a heat sink 3 Heat sink 5 Ceramic package 11 Package main body 30 Cu-Mo composite body 32 1st Cu board 34 2nd Cu board 40 Mo powder compact 50 Heat sink material

Claims (3)

  By rolling a Cu-Mo composite obtained by impregnating molten Cu into a molded body of Mo powder between a pair of Cu plates having substantially the same thickness, the Cu-Mo composite and the Cu plate A method of manufacturing a heat sink material having a joining structure, wherein one of the Cu plates is reduced in thickness after the rolling, and the thickness is different from that of the other Cu plate.   By rolling a Cu-Mo composite obtained by impregnating molten Cu into a molded body of Mo powder between a pair of Cu plates having substantially the same thickness, the Cu-Mo composite and the Cu plate In the method of manufacturing a heat sink material having a joint structure, the thickness of one of the Cu plates is increased after the rolling, and the thickness is different from that of the other Cu plate. A heat sink configured such that a Cu-Mo composite is interposed between a pair of Cu plates and bonded to each other, and the thicknesses of one Cu plate and the other Cu plate are different from each other;
Of the pair of Cu plates constituting the heat sink , a ceramic package brazed onto the main surface of the thick Cu plate ;
A ceramic package with a heat sink.

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