JP2010219441A - Package for housing electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component housing package made of ceramics and equipped with a radiator plate having less thermal deformation and an excellent heat dissipation property. <P>SOLUTION: In the electronic component housing package, an electronic component 4 such as a semiconductor element and the like is housed in a cavity 3 formed with a frame body 2 joined to an upper face of the radiator plate 1 which is formed by alternately laminating five layers or more in total of a copper layer 1a and a molybdenum layer 1b, and has an uppermost layer formed with clad material of the copper layer 1a; a lid body 5 is jointed to an upper face of the frame body 2 to seal the cavity 3 hermetically; the ratio of total thickness of a plurality of molybdenum layers 1b having a thickness 0.2 mm or less to the radiator plate 1 is 10-14%; and a thickness of an uppermost layer of the radiator plate 1 on the side where the electronic component 4 is loaded is composed of a copper layer having a thickness 0.2 mm or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic component storage package on which an electronic component such as a semiconductor element is mounted, and more particularly to a ceramic electronic component storage package having excellent heat dissipation.

  Ceramics are excellent in heat resistance, corrosion resistance, electrical conductivity and mechanical strength, and have little loss in the high frequency range, so they are suitable for frame bodies for housing semiconductor elements for wireless base stations such as mobile phones. . This package is also required to have a high heat dissipation property, but ceramics have a low thermal conductivity, so that a sufficient heat dissipation effect cannot be expected with the frame alone. Therefore, usually, a metal heat sink is attached to the ceramic frame.

As the package having the above structure, a package in which a metal heat sink is joined to a ceramic frame through a metallized film of a refractory metal such as tungsten (W) or molybdenum (Mo) is known. . Such a package is excellent in heat dissipation because a metal having a large thermal conductivity is used for the heat sink. However, metals not only have a higher thermal conductivity than ceramics, but also have a higher thermal expansion coefficient. Therefore, in general, when a metal heat sink is brazed to a ceramic frame, a crack is generated in the frame due to a difference in expansion or contraction between the heat sink and the frame due to a temperature change, or the heat sink and the frame. The phenomenon that the adhesiveness is reduced occurs at the joint portion. In this case, since the thermal resistance at the joint between the frame and the heat sink increases, the heat dissipation of the package decreases.
In order to cope with such a problem, conventionally, research and development have been actively conducted on a package provided with a heat radiating plate that has excellent heat dissipation and is less likely to be warped and deformed due to temperature change.

For example, Patent Document 1 discloses a heat radiating metal member having a name “heat radiating metal member and a package for an electronic component using the same” that reduces the amount of warping when the package body is joined, and an electronic device in operation. An invention relating to a package for an electronic component that can diffuse heat generated from the component well to the outside is disclosed.
In the invention disclosed in Patent Document 1, a heat radiating metal member is formed of a copper (Cu) -tungsten (W) -based composite metal material, and in particular, the thermal expansion coefficient of the composite metal material is 7.5 × 10 ^−6. As described above, the content is set to 8.5 × 10 ⁻⁶ or less, and the copper content of the composite metal material is set to 7% or more and 13% or less.
In such a heat dissipating metal member, when the ceramic package body is joined to the upper surface, the thermal stress generated between the heat dissipating metal member and the ceramic package body is reduced, and the joining strength between the two is improved. At the same time, the amount of warpage of the metal member for heat dissipation is reduced.

Next, Patent Document 2 discloses an invention relating to an inexpensive package having the name “high heat radiation type electronic component storage package” and improving the flatness of the upper surface of the heat sink plate to increase the bonding reliability of the electronic component. Has been.
In the invention disclosed in Patent Document 2, the first copper plate is clad-bonded or brazed to a metal plate made of a copper (Cu) -molybdenum (Mo) alloy plate or a copper (Cu) -molybdenum (Mo) composite plate. In the heat sink plate joined by attaching, the second copper plate having the same thickness as that of the first copper plate is formed on the side to be joined to the ceramic frame of the metal plate, and the outer peripheral edge is the inner peripheral side wall surface of the ceramic frame. And brazed so as to be close to each other.
In the package having such a structure, the first copper plate and the second copper plate are bonded to each other with a substantially balance on both sides with the metal plate as the center. Therefore, the package is generated due to a difference in thermal expansion coefficient between the metal plate and the copper plate. Warpage can be balanced over almost the entire surface. In addition, heat generated from the electronic component can be quickly transmitted to the heat sink plate to dissipate heat.

JP 2001-135759 A JP 2007-115793 A

  However, the invention disclosed in Patent Document 1 which is the above-described prior art has a small amount of copper in the heat radiating metal member, so that the heat conductivity of the heat radiating metal member becomes too small, and sufficient heat dissipation. The effect may not be obtained.

  Moreover, in the invention disclosed in Patent Document 2, there is no description about the ratio of copper and molybdenum constituting the metal plate to be the heat sink plate. Therefore, when these ratios are not appropriate values, there is a possibility that the effect of suppressing heat distortion of the heat sink plate and the heat dissipation effect are not sufficiently exhibited.

  The present invention has been made in response to such a conventional situation, and an object of the present invention is to provide a ceramic electronic component storage package including a heat radiating plate that has less heat deformation and excellent heat dissipation. .

In order to achieve the above object, the electronic component storage package according to the first aspect of the present invention includes a copper layer and a molybdenum layer having a thickness of 0.2 mm or less alternately stacked in total, and the copper layer is the outermost layer. And a ceramic frame bonded to one side of the heat sink, and the ratio of the thickness of the molybdenum layer to the heat sink is 10 to 14% in total. It is a feature.
The electronic component storage package having such a structure has an effect that the thermal conductivity of the heat radiating plate is not greatly reduced and only the thermal expansion coefficient is reduced.

According to a second aspect of the present invention, in the electronic component storage package according to the first aspect, the outermost layer on the side where the frame of the heat sink is joined is made of a copper layer having a thickness of 0.2 mm or more. It is a feature.
In the electronic component storage package having such a structure, since the copper layer on the surface on which the electronic component is mounted is thick, the effect of diffusing heat in the direction perpendicular to the thickness direction is enhanced.

  As described above, in the electronic component storage package according to claim 1 of the present invention, it is possible to prevent the occurrence of cracks in the frame body due to the thermal deformation of the heat radiating plate and improve the heat dissipation of the package. .

  In the electronic component storage package according to the second aspect of the present invention, the heat dissipation of the package can be further improved as compared with the invention according to the first aspect.

(A) is a top view of the Example of the electronic component storage package which concerns on embodiment of this invention, (b) is an enlarged view of the XX arrow cross section of the figure (a), ( (c) is a figure for demonstrating the layer structure of the heat sink of the figure (b). It is the experimental result which investigated the relationship between the coefficient of thermal expansion and the ratio of molybdenum about the clad material of copper and molybdenum. It is the experimental result which investigated the relationship between the thermal conductivity and the ratio of molybdenum about the clad material of copper and molybdenum. It is the result of performing a reliability test using a plurality of clad materials (5 layers) made of copper and molybdenum and having different molybdenum ratios for the heat sink of the electronic component storage package of this example. It is the experimental result which investigated the relationship between the thermal expansion coefficient and the copper thickness of the outermost layer about the clad material (5 layers) of copper and molybdenum. It is the experimental result which investigated the relationship between the thermal conductivity and the copper thickness of the outermost layer about the clad material (5 layers) of copper and molybdenum. It is the result of having measured the thermal resistance of the heat sink using the clad material (5 layers) which consists of copper and molybdenum and from which the copper thickness of the outermost layer differs in the heat sink of the electronic component storage package of a present Example.

  An electronic component storage package according to an embodiment of the present invention will be described with reference to FIGS.

  Fig.1 (a) is a top view of the Example of the electronic component storage package based on embodiment of this invention, (b) is an enlarged view of the XX arrow cross section of the figure (a). (C) is a figure for demonstrating the layer structure of the heat sink of the figure (b). In addition, illustration of the cover body is abbreviate | omitted in Fig.1 (a), and the heat sink in FIG.1 (b) is expanded and shown in the thickness direction in FIG.1 (c).

As shown in FIGS. 1A to 1C, the electronic component storage package of the present embodiment includes a heat sink 1 and a cavity 3 formed by a frame 2 joined to the upper surface of the heat sink 1. An electronic component 4 such as a semiconductor element is accommodated, and a lid 5 is joined to the upper surface of the frame 2 to hermetically seal the cavity 3.
The heat sink 1 is made of five layers of clad materials in which copper layers 1a and molybdenum layers 1b are alternately laminated and the outermost layer is constituted by the copper layer 1a. And the ratio of the thickness of the molybdenum layer 1b with respect to the heat sink 1 is 10 to 14% in total, and the thickness of each molybdenum layer 1b is all 0.2 mm or less. Further, the outermost layer on the side where the electronic component 4 of the heat sink 1 is mounted is constituted by a copper layer having a thickness of 0.2 mm or more.
The frame 2 is made of a ceramic such as alumina (Al ₂ O ₃ ) or aluminum nitride (AlN), and a metallized film 6 made of a conductor wiring pattern such as tungsten or molybdenum is formed on both surfaces thereof. And the heat sink 1 and the external connection terminal 7 are joined to both surfaces of the frame body 2 via the metallized film 6 using a brazing material such as Ag—Cu brazing. The external connection terminals 7 are joined to a wiring circuit pattern formed on an external substrate (not shown) using solder or the like.
The electronic component 4 housed in the cavity 3 is joined to the upper surface of the heat sink 1 coated with Au plating using a brazing material made of AuSi or the like, and connected to the external connection terminal 7 by a bonding wire 8. Yes. A lid 5 made of resin, ceramic, metal, or the like is bonded to the upper surface of the external connection terminal 7 using an insulating adhesive 9 such as resin or glass. The mounting portions 10 provided at both ends in the longitudinal direction of the heat sink 1 are screwed to a base or the like provided on the external substrate for the purpose of attaching the electronic component storage package to the external substrate. It is used for

Next, the role played by the molybdenum layer 1b in the heat sink 1 constituting the electronic component storage package of this embodiment will be described.
FIG. 2 shows the experimental results of investigating the relationship between the coefficient of thermal expansion and the molybdenum ratio for copper and molybdenum clad materials. The horizontal axis represents the ratio of molybdenum to the entire cladding material (that is, the ratio of the thickness of the molybdenum layer to the thickness of the entire cladding material), and the vertical axis represents the thermal expansion coefficient of the entire cladding material. Symbol “▲” and symbol “●” indicate measurement data when the clad material is naturally cooled from 400 ° C. and 800 ° C. to room temperature, respectively. The thermal expansion coefficient was measured in a nitrogen atmosphere using a Bruker thermal expansion measuring apparatus according to the method described in JISH7404. The size of the sample is 20 mm (length) × 4 mm (width) × 1.5 mm (thickness). Moreover, the thermal expansion coefficients of copper and molybdenum are 20 × 10 ⁻⁶ (/ ° C.) and 5 × 10 ⁻⁶ (/ ° C.), respectively.
In FIG. 2, the coefficient of thermal expansion of the cladding material decreases as the ratio of molybdenum to the entire cladding material increases. That is, in order to suppress thermal deformation of the cladding material, it is necessary to make the molybdenum layer relatively thick with respect to the entire cladding material. In order to further reduce the thermal deformation of the cladding material, the cladding material may be formed by sandwiching a copper layer having a large thermal expansion coefficient from above and below with a molybdenum layer having a small thermal expansion coefficient. In general, both surfaces of a heat dissipation plate used in a package for housing a semiconductor element are subjected to brazing or plating. Therefore, when the clad material having the above structure is used as a heat sink, it is desirable to have a structure of at least five layers with a copper layer that can be easily brazed or plated as the outermost layer.

FIG. 3 shows the experimental results of investigating the relationship between the thermal conductivity and the molybdenum ratio for the copper and molybdenum clad material. The horizontal axis represents the ratio of molybdenum to the entire cladding material (that is, the ratio of the thickness of the molybdenum layer to the thickness of the entire cladding material), and the vertical axis represents the thermal conductivity (W / m ° C.) of the entire cladding material. Yes. In addition, after calculating | requiring the thermal diffusivity prescribed | regulated to JISH7801 using the laser flash method thermal constant measuring apparatus by a vacuum Riko company, it carried out by the method of calculating the average value of a specific heat and a density from the volume ratio of copper and molybdenum. . The size of the sample is 10 mm (diameter) × 1.5 (thickness). The thermal conductivities of copper and molybdenum are 390 (W / m ° C.) and 142 (W / m ° C.), respectively.
As shown in FIG. 3, when the ratio of molybdenum to the entire cladding material is increased, the thermal conductivity of the cladding material is decreased. However, when the ratio of molybdenum to the entire cladding material exceeds 14%, the thermal conductivity of the cladding material is lower than 360 W / m ° C., and there is a possibility that a sufficient heat dissipation effect cannot be obtained when used for a heat sink. . Therefore, in the clad material used for the heat sink, it is desirable that the thickness of the molybdenum layer be 14% or less of the total thickness of the heat sink.

FIG. 4 shows the result of a reliability test using a plurality of clad materials made of copper and molybdenum and having different molybdenum ratios for the heat sink of the electronic component storage package of this example. Specifically, the temperature of the electronic component storage package (100 samples) attached with each clad material as a heat sink is changed from −65 ° C. to 150 ° C., and the presence or absence of cracks generated in the frame 2 is visually observed. confirmed. In FIG. 4, the horizontal axis represents the ratio of molybdenum to the entire cladding material (that is, the ratio of the thickness of the molybdenum layer to the total thickness of the cladding material), and the vertical axis represents the package in which cracks occurred in the frame 2. It represents a percentage (%).
As shown in FIG. 4, when the ratio of molybdenum to the entire cladding material is smaller than 10%, cracks are generated in the frame 2. This is probably because the frame 2 is structurally weaker to stresses such as bending than a plate-like ceramic.
In this way, cracks may occur in the frame body 2 due to thermal deformation of the heat radiating plate 1. Therefore, in the clad material used for the heat radiating plate 1, the thickness of the molybdenum layer 1 b is set to the heat radiating plate as in this embodiment. It is desirable to be 10% or more of the thickness of 1. If the thickness of each molybdenum layer 1b constituting the clad material exceeds 0.2 mm, it becomes difficult to process the clad material by press punching or the like, so that the thickness of the molybdenum layer 1b is 0.2 mm or less. It is desirable to do.

FIG. 5 shows the experimental results of investigating the relationship between the thermal expansion coefficient and the copper thickness of the outermost layer for the copper and molybdenum clad material (5 layers). The horizontal axis represents the copper thickness (mm) of the outermost layer, and the vertical axis represents the thermal expansion coefficient of the entire cladding material. Symbol “▲” and symbol “●” indicate measurement data when the clad material is naturally cooled from 400 ° C. and 800 ° C. to room temperature, respectively. Note that the measurement method of the thermal expansion coefficient and the size of the sample are the same as those in FIG. Further, the ratio of molybdenum to the entire cladding material is 12%.
FIG. 5 shows that the thermal expansion coefficient of the clad material is hardly influenced by the copper thickness of the outermost layer within the range of this measurement condition.

FIG. 6 shows the experimental results of investigating the relationship between the thermal conductivity and the copper thickness of the outermost layer for the copper and molybdenum clad material (5 layers). The horizontal axis represents the copper thickness (mm) of the outermost layer, and the vertical axis represents the thermal conductivity (W / m ° C.) of the entire cladding material. In addition, the measuring method of thermal conductivity is the same as the case of FIG. 3, and the same sample as the test of FIG. 5 was used.
FIG. 6 shows that the thermal conductivity of the clad material is hardly influenced by the copper thickness of the outermost layer within the range of this measurement condition.

FIG. 7 shows the result of measuring the thermal resistance of a heat sink using a plurality of clad materials (5 layers) made of copper and molybdenum and having different outermost copper thicknesses as the heat sink of the electronic component storage package of this example. It is. The horizontal axis represents the copper thickness (mm) of the outermost layer, and the vertical axis represents the thermal resistance (° C./W) of the entire cladding material. In addition, the measurement of thermal resistance was performed using the homemade measuring apparatus according to the method described in SEMI-STD G38-87 and G30-87. Further, the ratio of molybdenum to the entire cladding material is 12%.
As shown in FIG. 7, when the copper thickness of the outermost layer is 0.2 mm or more, the thermal resistance of the clad material becomes smaller than 0.55 ° C./W, and a sufficient heat dissipation effect as a heat sink can be expected. In addition, when the copper thickness of the outermost layer is 0.2 mm or more, the thermal conductivity of the clad material hardly changes as described in FIG. , Its thermal resistance is improved. This is considered to be due to the fact that by increasing the thickness of the copper layer 1a on the surface on which the electronic component 4 is mounted, the action of diffusing heat in the direction perpendicular to the thickness direction is enhanced, and the heat dissipation is improved.

  As described above, according to the electronic component storage package of the present embodiment, in the heat sink 1 made of the clad material of copper and molybdenum, by reducing the thermal expansion coefficient while suppressing the decrease in thermal conductivity, While preventing the generation of cracks in the frame 2 due to thermal deformation of the heat radiating plate 1, it is possible to obtain a sufficient heat radiating effect.

  In this embodiment, the clad material constituting the heat radiating plate 1 has five layers, but the present invention is not limited to this. That is, the clad material constituting the heat radiating plate 1 may be formed by laminating at least five copper layers 1a and molybdenum layers 1b alternately.

  The invention described in claim 1 and claim 2 can be applied to a ceramic electronic component storage package including a heat sink.

  DESCRIPTION OF SYMBOLS 1 ... Heat sink 1a ... Copper layer 1b ... Molybdenum layer 2 ... Frame 3 ... Cavity 4 ... Electronic component 5 ... Lid body 6 ... Metallized film 7 ... External connection terminal 8 ... Bonding wire 9 ... Insulating adhesive 10 ... Mounting part

Claims (2)

A copper plate and a molybdenum layer having a thickness of 0.2 mm or less are alternately laminated in a total of five or more layers, and the heat sink made of a clad material in which the copper layer constitutes the outermost layer;
A ceramic frame joined to one side of the heat sink,
The ratio of the thickness of the molybdenum layer to the heat sink is 10 to 14% in total. 2. The electronic component storage package according to claim 1, wherein an outermost layer on a side of the heat sink to which the frame body is joined is made of a copper layer having a thickness of 0.2 mm or more.