JP2023071204A - package - Google Patents

Abstract

To provide a package capable of sufficiently suppressing warpage or stress caused by a thermal expansion difference at low cost while sufficiently securing hat dissipation characteristics of the package.SOLUTION: A package 51 comprises a cavity CV which is sealed by a lid body 80. A ceramic frame body 61 encloses the cavity CV in a planar view. A first heat sink layer 30 comprises: a first surface S1 including an inner region RI opposed to the cavity CV and an outer region RO supporting the ceramic frame body 61; and a second surface S2 at an opposite side of the first surface S1. The first sink layer 30 includes a first ceramic layer 31 and a plurality of first metal vias 32. The first ceramic layer 31 forms the first surface S1 and the second surface S2, and a plurality of first via holes VH1 is provided between the first surface and the second surface. The plurality of first metal vias 32 is disposed in the plurality of first via holes VH1 of the first ceramic layer 31.SELECTED DRAWING: Figure 3

Description

The present invention relates to packages, and more particularly to packages having a cavity to be sealed by a lid.

Packages having cavities are often used to house electronic components such as power semiconductor devices. After the electronic component is mounted in the cavity of the package, the cavity is hermetically sealed by bonding the lid to the package. This provides an electronic device having electronic components protected from the external environment. The bottom surface of the heat sink (the surface opposite to the surface on which the electronic components are mounted) is usually attached to a supporting member that supports it. The support member is, for example, a mounting board or a heat dissipation member. The support member is brought into thermal contact with the bottom surface of the heat sink. Through the heat sink, heat from the electronic component is efficiently discharged to the outside of the package (typically to the support member). Thereby, the temperature rise of the electronic component is suppressed to about 150° C., for example. On the other hand, depending on the external environment in which the electronic device is placed, the temperature of the package may drop below freezing. Therefore, electronic devices are exposed to heat cycles caused by these temperature differences.

According to the technique disclosed in Japanese Patent Application Laid-Open No. 2003-282751 (Patent Document 1), a Cu (copper) or Cu-based metal plate is used as a heat sink plate. Cu is inexpensive and has a high thermal conductivity exceeding 300 W/m·K. Therefore, the heat dissipation property of the heat sink plate can be improved while suppressing the material cost of the heat sink plate. According to this technique, first, a semiconductor element is mounted on a heat sink plate by brazing. Next, a frame to which external connection terminals are bonded in advance is bonded onto the heat sink plate so as to surround the semiconductor element. By using a low-melting-point bonding material for this bonding, the frame is bonded at a temperature lower than the brazing temperature of the semiconductor element. Next, the cavity is sealed by joining a cover to the upper surface of the frame. An electronic device is thus obtained.

According to Japanese Patent Laying-Open No. 2015-204426 (Patent Document 2), the package has a heat sink plate and a ceramic frame. A heat sink plate is a rectangular metal plate that dissipates heat generated from electronic components mounted on its upper surface. The ceramic frame is joined to the heat sink plate so as to surround the portion where the electronic component is mounted. The joining is performed by brazing. The brazing temperature is about 780°C. The ceramic frame is made of alumina or aluminum nitride, for example. The heat sink plate is a metal plate. This metal plate has a high thermal conductivity and can reduce the warpage of the package due to the difference in thermal expansion coefficient when brazed with the ceramic frame.

Japanese Patent Laying-Open No. 2005-243819 (Patent Document 3) discloses that CPC (registered trademark) is widely used for heat sinks. CPC is a composite metal plate (composite material) having a Cu—Mo (molybdenum) alloy layer and Cu layers provided above and below it. The coefficient of linear expansion of CPC is lower than that of Cu. Therefore, by using CPC instead of Cu as a heat sink material, the coefficient of linear expansion of the heat sink can be brought close to that of ceramic.

Japanese Patent Application Laid-Open No. 2003-282751 JP 2015-204426 A JP 2005-243819 A

In the technique disclosed in JP-A-2015-204426, the metal plate used as the heat sink is selected to have a high thermal conductivity and a small difference in thermal expansion from the ceramic frame during brazing. A typical material intended to meet such requirements is CPC, as described in JP-A-2005-243819 mentioned above. When CPC is used as the heat sink material, package warpage or stress due to the difference in thermal expansion between the heat sink and the ceramic frame can be reduced compared to when Cu is used. However, CPC or similar materials are significantly more expensive than Cu. Therefore, it is desirable to reduce package warpage or stress while using less expensive materials. If a ceramic material is used as a heat sink material instead of a metal material, the difference in thermal expansion can be suppressed. Heat dissipation characteristics tend to be insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and its object is to sufficiently suppress the warpage or stress caused by the difference in thermal expansion while sufficiently ensuring the heat dissipation characteristics of the package. to provide a package that can

The package has a cavity to be sealed by a lid. The package includes a ceramic frame that surrounds the cavity in plan view, and a first heat sink layer. The first heat sink layer has a first side with an inner region facing the cavity and an outer region supporting the ceramic frame, and a second side opposite the first side. The first heat sink layer includes a first ceramic layer and a plurality of first metal vias. The first ceramic layer has a first surface and a second surface, and a plurality of first via holes are provided between the first surface and the second surface. A plurality of first metal vias are disposed within the plurality of first via holes in the first ceramic layer.

According to the package described above, firstly, the first heat sink layer includes a plurality of first metal vias, so that the heat dissipation characteristics of the package can be sufficiently ensured. Secondly, since the first heat sink layer includes the first ceramic layer, it is possible to sufficiently suppress warpage or stress of the package due to the difference in thermal expansion between the first heat sink layer and the ceramic frame. Thirdly, the structure in which metal vias are provided in the ceramic layer as the first heat sink layer can be easily formed at a relatively low cost. As described above, it is possible to sufficiently suppress the warpage or stress of the package due to the difference in thermal expansion between the first heat sink layer and the ceramic frame while sufficiently ensuring the heat dissipation characteristics of the package at low cost.

The plurality of first metal vias may be arranged off the outer region of the first surface. In this case, the plurality of first metal vias can be arranged intensively in the inner region of the first surface that is particularly susceptible to heat. As a result, the heat dissipation path can be effectively arranged without unnecessarily increasing the proportion of the plurality of first metal vias in the first heat sink layer.

The package may further include a first metal layer provided on the first surface of the first heat sink layer and connecting the plurality of first metal vias. In this case, heat is distributed on the first surface. Thereby, the heat dissipation characteristics of the package can be further improved.

The first metal layer may be disposed on the inner region of the first surface away from the outer region of the first surface. In this case, the first metal layer can be concentrated on the inner region of the first surface that is particularly susceptible to heat. As a result, the thermal expansion of the first metal layer can suppress the adverse effect of the warp or stress of the package, and the heat dissipation characteristics of the package can be further improved.

When the first metal via is made of a via material having a thermal conductivity of 200 W/m·K or higher, the heat dissipation characteristics of the package can be further enhanced. If the via material contains copper, the thermal conductivity of the via material can be easily increased. If the via material further comprises tungsten, formation of the first heat sink layer is facilitated by co-firing the first ceramic layer and the first metal vias. Thereby, the first heat sink layer can be formed at a lower cost.

When the first ceramic layer is made of a material containing alumina, the first ceramic layer can be made of a typical ceramic material for packaging. Although the use of alumina, a material with poor thermal conductivity compared to metal, reduces the average thermal conductivity of the first heat sink layer, the reduction is at least partially compensated by the plurality of first metal vias. . As a result, it is possible to avoid the heat dissipation characteristics of the package from becoming too small.

If the ceramic frame and the first ceramic layer are made of the same material, a difference in thermal expansion between the ceramic frame and the first ceramic layer can be avoided.

When the volume ratio of the plurality of first metal vias in the first heat sink layer is 20% or more, the heat dissipation characteristics of the package can be more sufficiently secured. When the volume ratio of the plurality of first metal vias in the first heat sink layer is 60% or less, the warpage or stress of the package due to the difference in thermal expansion between the first heat sink layer and the ceramic frame is more sufficiently suppressed. can do. In addition, since the volume ratio of the first ceramic layer to the first heat sink layer is large, the green sheet that becomes the first ceramic layer is less likely to be damaged by firing in the manufacturing process of the first heat sink layer.

The plurality of first metal vias may include metal vias that taper from the first side to the second side of the first heat sink layer. This tapered shape increases the efficiency of heat transfer from the first surface to the second surface through the first metal via. As a result, the heat dissipation characteristics of the package can be more sufficiently ensured without increasing the proportion of the plurality of first metal vias in the first heat sink layer.

The package may further include a second metal layer. A second metal layer is provided on the second surface of the first heat sink layer and connects the plurality of first metal vias. This distributes the heat on the second surface. Therefore, the heat dissipation characteristics of the package can be further enhanced.

The second metal layer may extend over the inner region and the outer region of the first surface in plan view. In this case, the heat is distributed more widely on the second surface. Thereby, the heat dissipation characteristics of the package can be further improved.

The package may further include a second heat sink layer. The second heat sink layer has a third side facing the second metal layer and a fourth side opposite the third side. The second heat sink layer includes a second ceramic layer and a plurality of second metal vias. The second ceramic layer has third and fourth surfaces, and a plurality of second via holes are provided between the third and fourth surfaces. A plurality of second metal vias are disposed within the plurality of second via holes in the second ceramic layer. According to this structure, the heat transferred in the thickness direction by the plurality of first metal vias is diffused in the in-plane direction by the second metal layer, and then further transferred in the thickness direction by the plurality of second metal vias. . Thereby, the heat dissipation characteristics of the package can be further improved.

The plurality of second metal vias of the second heat sink layer are not only metal vias included in the inner region of the first surface of the first heat sink layer in plan view, but also at least in the outer region of the first surface of the first heat sink layer. Partially contained metal vias may also be included. In this case, the heat conduction paths are more widely distributed in the second heat sink layer. Therefore, the heat dissipation characteristics of the package can be further enhanced.

Objects, features, aspects and advantages of the present invention will become more apparent with the following detailed description and accompanying drawings.

1 is a schematic perspective view showing the configuration of an electronic device according to Embodiment 1, partly omitted so that the inside of a cavity can be seen; FIG. 2 is a schematic cross-sectional view along line II-II of the electronic device of FIG. 1; FIG. 3 is a schematic cross-sectional view showing the configuration of a package as a component of the electronic device of FIG. 2; FIG. FIG. 4 is a schematic cross-sectional view showing the configuration of a package of a comparative example; 5 is a schematic cross-sectional view showing the configuration of an electronic device using the package of FIG. 4; FIG. FIG. 3 is a graph illustrating temperature dependence of coefficient of linear expansion (CTE) of each of copper (Cu), alumina (Al ₂ O ₃ ), and composite material (CPC). The simulation results (solid line) of the relationship between the volume ratio S _B of the first metal vias in the first heat sink layer and the thermal resistance Θ _jc of the first heat sink layer are plotted against the thermal resistance Θ _jc when CPC is used for the heat sink plate. is a graph diagram shown together with the simulation result (broken line). 6 is a schematic cross-sectional view showing the configuration of a package according to Embodiment 2; FIG. FIG. 11 is a schematic cross-sectional view showing the configuration of a package according to Embodiment 3;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings. In this specification, metal can mean either a pure metal or an alloy unless otherwise specified. The value of the linear expansion coefficient (CTE: Coefficient of Thermal Expansion) is _L25 at a temperature of 25°C (room temperature) and _LT at a temperature T,
{(L _T −L ₂₅ )/(T−25)}/L ₂₅
defined by If the coefficient of linear expansion is anisotropic, the one in the in-plane direction is adopted.

<Embodiment 1>
FIG. 1 is a schematic perspective view showing the configuration of an electronic device 90 according to Embodiment 1. FIG. FIG. 2 is a schematic cross-sectional view of electronic device 90 of FIG. 1 along line II-II. The electronic device 90 has a package 51 , a lid 80 and electronic components 8 . The electronic device 90 may also have an adhesive layer 70 . Further, the electronic device 90 may have wires 9 (wiring members). In FIG. 1, the illustration of the lid 80 and the adhesive layer 70 is partially omitted so that the inside of the cavity CV of the package 51 can be partially seen. The electronic component 8 may be a power semiconductor element, in which case the electronic device 90 is a power module. The power semiconductor device may be for radio frequency (RF) applications, in which case the electronic device 90 is an RF power module. Although one electronic component 8 is illustrated in FIGS. 1 and 2 , a plurality of electronic components 8 may be mounted on the package 51 .

FIG. 3 is a schematic cross-sectional view showing the configuration of the package 51 as a component of the electronic device 90 (FIG. 2). When the package 51 is prepared for manufacturing the electronic device 90, the electronic components 8 are not yet mounted as shown in FIG. The package 51 has a cavity CV to be sealed by the lid 80 . The package 51 includes a ceramic frame 61 , a first heat sink layer 30 , lead frames 65 (metal terminals), a first metal layer 10 and a second metal layer 20 .

The ceramic frame 61 surrounds the cavity CV in plan view (projection onto a plane perpendicular to the thickness direction). The outer edge of the ceramic frame 61 may have a rectangular shape as shown in FIG. 1, and the size of each side is, for example, 10 mm or more and 40 mm or less. The thickness of the ceramic frame 61 is, for example, 0.1 mm or more and 1 mm or less. When the thickness is 0.1 mm or more, it is easy to form a green sheet that becomes the ceramic frame 61 by firing. When the thickness is 1 mm or less, the dimension of the wire 9 (FIG. 2) in the thickness direction (vertical direction in FIG. 2) is prevented from becoming excessively large, thereby avoiding the inductance of the wire 9 from being excessively large.

The first heat sink layer 30 has a first surface S1 and a second surface S2 opposite to the first surface S1. Each of the first surface S1 and the second surface S2 may be a flat surface perpendicular to the thickness direction. The first surface S<b>1 has an inner region RI facing the cavity CV through the first metal layer 10 and an outer region RO supporting the ceramic frame 61 . The first heat sink layer 30 includes a first ceramic layer 31 and a plurality of first metal vias 32 .

The first ceramic layer 31 has a first surface S1 and a second surface S2, and a plurality of first via holes VH1 are provided between the first surface S1 and the second surface S2. The thickness of the first ceramic layer 31 is, for example, 0.1 mm or more and 3.0 mm or less. When the thickness is 0.1 mm or more, it is easy to form a green sheet that becomes the first ceramic layer 31 by firing. When the thickness is 3.0 mm or less, it is easy to ensure the heat dissipation of the first heat sink layer 30 . The first ceramic layer 31 may be made of a material containing alumina, for example substantially made of alumina. The ceramic frame 61 and the first ceramic layer 31 may be made of the same material, and in this case, the interface between the ceramic frame 61 and the first ceramic layer 31 may be virtual. This virtual boundary surface may be defined as an extrapolated surface of the inner region RI of the first surface S1 of the first heat sink layer 30, for example. The ceramic frame 61 and the first ceramic layer 31 are integrally formed as a ceramic member. This formation is typically performed by firing a laminate of green sheets that will form the ceramic frame 61 and green sheets that will form the first ceramic layer 31 .

The plurality of first metal vias 32 are arranged inside the plurality of first via holes VH1 of the first ceramic layer 31 . The plurality of first metal vias 32 are arranged outside the outer region RO of the first surface S1. The volume ratio of the plurality of first metal vias 32 to the first heat sink layer 30 is preferably 20% or more and 60% or less. The first metal via 32 is made of a via material having a thermal conductivity of 200 W/m·K or more. In order to obtain high thermal conductivity, the via material preferably contains Cu. The upper limit of the thermal conductivity of the via material is usually about 450 W/m·K even if a high thermal conductive material is used. The via material may further contain W (tungsten). In other words, the via material may be a Cu—W alloy or a mixed structure of Cu and W. By including W in addition to Cu, it becomes easy to form both the first ceramic layer 31 and the first metal via 32 by simultaneous firing. When co-firing is performed, the proportion of W is preferably 30% by volume or more and 80% by volume or less. The first metal vias 32 may be formed by sintering metal powder. The metal powder may be sintered after being dispersed in a paste and filled into the via hole. It should be noted that the above description of the method of forming the metal via is not limited to the first metal via 32, and may be the same for other metal vias to be described later.

The area of each first metal via 32 on the first surface S1 is, for example, 0.001 mm ² or more and 0.2 mm ² or less. The shape of each first metal via 32 on the first surface S1 may be elliptical or substantially circular. When the shape is a circle, its diameter is, for example, 0.01 mm or more and 0.5 mm or less. These favorable conditions are the same on the second surface S2.

The first metal layer 10 is provided on the first surface S<b>1 of the first heat sink layer 30 and connects the plurality of first metal vias 32 . The first metal layer 10 is arranged on the inner region RI of the first surface S1 away from the outer region RO of the first surface S1. The first metal layer 10 constitutes the bottom surface MT of the cavity CV. The first metal layer 10 comprises a first metallized layer 11 directly provided on the first surface S1 of the first heat sink layer 30 and a first metallized layer 11 provided on the first surface S1 of the first heat sink layer 30 via the first metallized layer 11. and a first plating layer 12 formed thereon.

The first metallized layer 11 may be formed by sintering metal powder. The metal powder may be sintered after it has been applied onto the ceramic layer while dispersed in a paste. The material of the first metallization layer 11 may be similar to the via material described above. The thickness of the first metallized layer 11 is, for example, 0.005 mm or more and 0.05 mm or less. When the thickness is within this range, it is easy to apply the manufacturing method using screen printing of the above paste. The above descriptions of the forming method, material, and thickness range may be applied not only to the first metallized layer 11 but also to other metallized layers to be described later.

The thickness of the first plating layer 12 is, for example, 0.001 mm or more and 0.05 mm or less. When the thickness is 0.05 mm or less, it is easy to carry out the plating process within an industrially acceptable time. The first plating layer 12 may contain a Cu plating layer. The first plating layer 12 may have a laminated structure of a Cu plating layer and an Ag (silver) layer plated thereon. Note that the above description of the thickness range and material may be applied not only to the first plated layer 12 but also to other plated layers to be described later.

The second metal layer 20 is provided on the second surface S<b>2 of the first heat sink layer 30 and connects the plurality of first metal vias 32 . The second metal layer 20 straddles the inner region RI and the outer region RO of the first surface S1 in plan view. The second metal layer 20 includes a second metallized layer 21 directly provided on the second surface S2 of the first heat sink layer and a second metallized layer 21 provided on the second surface S2 of the first heat sink layer 30 via the second metallized layer 21. and a second plating layer 22 formed thereon.

The lead frame 65 constitutes an electrical path connecting the inside and outside of the cavity CV. The material of the lead frame 65 may contain Cu, for example, consists essentially of Cu. A lead frame 65 is provided on the ceramic frame 61 . A bonding material (not shown) may be provided between the lead frame 65 and the ceramic frame 61 to bond them together. This bonding material may be formed by Ag sinter bonding, in which case it is a mixture of thermosetting resin (eg, epoxy resin or silicone resin) and Ag particles.

Next, an example method of manufacturing the electronic device 90 (FIG. 2) will be described below.

Referring to FIG. 3, package 51 (FIG. 3) is first prepared. Referring to FIG. 2, electronic component 8 is mounted on bottom surface MT of cavity CV of package 51 . This mounting may be done by soldering. In other words, a solder material may be used as the mounting material 7 for mounting the electronic component 8 . Electronic component 8 is then electrically connected to lead frame 65 by wire 9 . Wires 9 may be formed by wire bonding.

A lid 80 is prepared. The lid 80 may be made of a ceramic material, which may contain alumina as a main component, eg substantially alumina. Alternatively, the lid body 80 may contain resin. The resin is, for example, liquid crystal polymer. An inorganic filler may be dispersed in the resin, and the inorganic filler is, for example, silica particles. By dispersing the inorganic filler in the resin, the strength and durability of the lid 80 can be enhanced.

Next, the lid 80 is placed on the ceramic frame 61 provided with the lead frame 65 via the adhesive layer 70 . The adhesive layer 70 contains a thermosetting resin in this example, and is in a semi-cured state at the time of placement. The adhesive layer 70 is provided on the ceramic frame 61 so as to surround the cavity CV. The adhesive layer 70 may have a portion provided on the ceramic frame 61 via the lead frame 65, as shown in FIG. The thickness of the adhesive layer 70 between the lid 80 and the package 51 is, for example, 100 μm or more and 360 μm or less. The lid 80 may have an inner surface 81i facing the cavity CV (FIG. 1) and an opposite outer surface 81o, and typically the inner surface 81i has the frame shape of the ceramic frame 61. A frame portion 81p, which is a projection having a frame shape roughly corresponding to the . In this case, the adhesive layer 70 is in contact with the frame portion 81p.

Next, the lid body 80 is pressed against the ceramic frame body 61 with a predetermined load. An appropriate load depends on the dimensional design of the package 51, but is, for example, about 500 g or more and 1 kg or less. The adhesive layer 70 is heated while being pressed with a load. The heated adhesive layer 70 first changes to a softened state. This reduces the viscosity of the adhesive layer 70 . As a result, the adhesive layer 70 is wetted and spread. After that, the adhesive layer 70 changes to a hardened state as the curing reaction by heating progresses, and as a result, the adhesive layer 70 bonds the lid 80 and the ceramic frame 61 to each other.

The adhesive layer 70 may contain at least one of epoxy resin, phenol resin and silicone resin as a main component. Epoxy resins are particularly preferred because they have well-balanced heat resistance, mechanical strength and chemical resistance. In order to preferably have these characteristics, the content of the epoxy resin as the main component is preferably 20 to 40 wt%, and the balance may be composed of subcomponents such as a curing agent. Specifically, the subcomponents include, for example, 1 to 10 wt% curing agent, 50 to 70 wt% inorganic filler, 0.5 to 2 wt% coupling agent, and 0.5 to 2 wt% catalyst. and 0.1-5 wt % of a low stress agent. A phenoxy resin compound may be used as the curing agent. Silica may be used as the inorganic filler. Organic phosphorus or boron salts may be used as catalysts. Silicone may be used as a low stress agent. The adhesive layer 70 may have a bending elastic modulus smaller than that of the lid 80 .

As described above, as shown in FIGS. 1 and 2, a configuration is obtained in which the lid 80 seals the cavity CV. In other words, electronic device 90 (FIGS. 1 and 2) is obtained. The bottom surface BT of the electronic device 90 (in other words, the bottom surface BT of the package 51) is attached to the support member 100 (FIG. 2). The support member 100 is, for example, a mounting board or a heat dissipation member. The first heat sink layer 30 may have penetrations (not shown) through which fasteners (eg, screws) for attachment to the support member 100 pass.

Next, a first example of a method for manufacturing the package 51 (FIG. 3) will be described below.

A green sheet to be the first ceramic layer 31 is formed. A first via hole VH1 is formed in the green sheet by, for example, laser processing or punching. The first via hole VH1 is filled with a CuW paste (that is, a paste containing a mixed powder of Cu and W) that forms the first metal via 32 . Further, a CuW paste layer that becomes the first metallized layer 11 is applied on the first surface S1 of the green sheet. Further, a CuW paste layer that becomes the second metallized layer 21 is applied onto the second surface S2 of the green sheet. A green laminated body is formed by laminating the green sheet to be the ceramic frame 61 on the first ceramic layer 31 .

Next, the green laminated body is fired, for example, at about 1500.degree. A ceramic laminate is thus obtained. Next, the first plating layer 12 and the second plating layer 22 are formed on the first metallization layer 11 and the second metallization layer 21, respectively. Next, the lead frame 65 is bonded onto the ceramic frame 61 by, for example, the Ag sinter bonding described above.

The package 51 is obtained by the above.

Next, a second example of the method of manufacturing the package 51 (FIG. 3) will be described below.

A green sheet to be the first ceramic layer 31 is formed. A first via hole VH1 is formed in the green sheet by, for example, laser processing or punching. A green laminated body is formed by laminating the green sheet to be the ceramic frame 61 on the first ceramic layer 31 . Next, the green laminate is fired at a firing temperature of about 1500° C., for example. A ceramic laminate is thus formed.

Next, the first via hole VH<b>1 of the first ceramic layer 31 is filled with a Cu paste (that is, a paste containing Cu powder) that will become the first metal via 32 . Also, a Cu paste layer that will become the first metallized layer 11 is applied onto the first surface S<b>1 of the first ceramic layer 31 . Also, a Cu paste layer that will become the second metallized layer 21 is applied onto the second surface S<b>2 of the first ceramic layer 31 . Next, the Cu paste is fired at a firing temperature (for example, 600° C. to 800° C.) lower than the firing temperature of the ceramic laminate. Thereby, the first metal via 32, the first metallized layer 11 and the second metallized layer 21 are formed.

Next, the first plating layer 12 and the second plating layer 22 are formed on the first metallization layer 11 and the second metallization layer 21, respectively. Next, the lead frame 65 is bonded onto the ceramic frame 61 by, for example, the Ag sinter bonding described above.

The package 51 is obtained by the above.

Both of the above-described first and second examples of methods of manufacturing package 51 can be implemented at low cost using typical multi-layer ceramic process technology. Especially in the first example, since the first ceramic layer 31 and the first metal via 32 are fired simultaneously, the manufacturing cost can be further reduced. On the other hand, in the second example, high thermal conductivity can be obtained by applying a composition with a high Cu ratio (for example, substantially 100%) as the composition of the first metal via 32 .

FIG. 4 is a schematic cross-sectional view showing the configuration of a package 59 of a comparative example. FIG. 5 is a schematic cross-sectional view showing the configuration of an electronic device 99 using the package 59 of FIG. The package 59 has a ceramic frame 29 bonded onto the heat sink plate 39 with a bonding material 26 instead of the ceramic frame 61 (FIG. 3: Embodiment 1). Ceramic frame 29 is typically made of alumina (Al ₂ O ₃ ). The bonding material 26 has fluidity when formed, and as shown in FIG. 4, flows inward from the inner peripheral surface of the ceramic frame 29 (the surface facing the cavity CV). The flow-in distance is, for example, 0.025 mm or more and 0.25 mm or less, depending on the process conditions. As a result, when the electronic component 8 is mounted in the cavity CV, the electronic component 8 needs to be separated from the inner peripheral surface of the ceramic frame 29 by the distance or more in the in-plane direction. Therefore, as the distance increases, the length of the wire 9 also increases, and as a result, the inductance of the wire 9 also increases. An increase in the inductance of wire 9 is usually undesirable. According to the present embodiment described above, such problems can be avoided.

FIG. 6 is a graph illustrating the temperature dependence of the coefficient of linear expansion (CTE) of each of copper (Cu), alumina (Al ₂ O ₃ ) and composite material (CPC). Cu has a significantly larger coefficient of linear expansion than that of Al ₂ O ₃ , which is a typical ceramic material. Therefore, when the heat sink plate 39 is made of Cu in the package 59 of the comparative example, there is a large difference between the linear expansion coefficient of the heat sink plate 39 and the linear expansion coefficient of the ceramic frame ₂₉ made of _Al2O3 . Due to this difference, the warpage or stress of the package 59 due to the difference in thermal expansion between the heat sink plate 39 and the ceramic frame 29 also increases. On the other hand, using CPC instead of Cu greatly reduces this difference. Therefore, the warpage or stress of the package 59 due to the difference in thermal expansion is also relatively small. However, CPC (or similar material) is significantly more expensive than Cu.

FIG. 7 shows simulation results (solid line) of the relationship between the volume ratio S _B of the first metal vias 32 occupying the first heat sink layer 30 (FIG. 3) and the thermal resistance Θ _jc of the first heat sink layer 30 . FIG. 5 is a graph diagram shown in FIG. 4 together with a simulation result (broken line) of thermal resistance Θ _jc when CPC is used; From this result, it can be seen that the thermal resistance Θ _jc of the first heat sink layer 30 can be suppressed to less than twice the thermal resistance Θ _jc in the case of CPC by setting the volume ratio S _B to 20% or more. Furthermore, it can be seen that by setting the volume ratio S _B to 30% or more, the thermal resistance Θ _jc of the first heat sink layer 30 can be suppressed to approximately 1.5 times or less of the thermal resistance Θ _jc in the case of CPC. Furthermore, by setting the volume ratio S _B to 40% or more, the thermal resistance Θ _jc of the first heat sink layer 30 can be made approximately equal to the thermal resistance Θ _jc in the case of CPC.

The above simulation is performed under the following conditions. The thermal resistance Θ _jc is the temperature difference (unit: K) between the top surface of the semiconductor chip as the electronic component 8 (FIG. 2) and the bottom surface BT of the package 51, expressed as the output of the electronic component (unit: W). excluding A chip as the electronic component 8 has a thermal conductivity of 200 W·m/K on the assumption that it is substantially made of Si. Assuming that the mounting material 7 is made of Ag, the mounting material 7 has a thermal conductivity of 420 W·m/K. The ceramic frame 61 (FIG. 3) has a thermal conductivity of 17.8 W·m/K assuming that it is made of Al ₂ O ₃ . Assuming that the first plating layer 12 and the second plating layer 22 are made of Cu, they have a thermal conductivity of 391 W·m/K. The first metallized layer 11 and the second metallized layer 21 have a thermal conductivity of 280.5 W·m/K assuming that they are made of a CuW alloy (composition ratio is 50:50). Assuming that the support member 100 (FIG. 2) is made of Al, it has a thermal conductivity of 236 W·m/K. The total thickness of the first heat sink layer 30, the first metal layer 10, and the second metal layer 20 is 1 mm. Each thickness of the first plating layer 12 and the second plating layer 22 is 50 μm. Each thickness of the first metallized layer 11 and the second metallized layer 21 is 10 μm. CPC as the heat sink plate 39 in the comparative example has a thickness of 1 mm and a thermal conductivity of 200 W·m/K. 2 and 5, the configuration of lead frame 65 and above is not considered in the simulation, but this can be ignored for the purpose of comparing thermal resistance Θ _jc . It is considered to be a thing.

According to the present embodiment, firstly, since the first heat sink layer 30 includes the plurality of first metal vias 32, the heat dissipation characteristics of the package 51 can be sufficiently ensured. Secondly, by including the first ceramic layer 31 in the first heat sink layer 30, warpage or stress of the package 51 due to the difference in thermal expansion between the first heat sink layer 30 and the ceramic frame 61 can be sufficiently suppressed. can be done. Thirdly, the structure in which metal vias are provided in the ceramic layer as the first heat sink layer can be easily formed at a relatively low cost. From the above, it is possible to sufficiently suppress the warpage or stress of the package 51 due to the difference in thermal expansion between the first heat sink layer 30 and the ceramic frame 61 while ensuring the heat dissipation characteristics of the package 51 at low cost. It is possible.

The plurality of first metal vias 32 are arranged away from the outer region RO of the first surface S1. As a result, the plurality of first metal vias 32 can be arranged intensively in the inner region RI of the first surface S1, which is particularly susceptible to heat. Therefore, the heat dissipation paths can be effectively arranged without unnecessarily increasing the ratio of the plurality of first metal vias 32 in the first heat sink layer 30 .

The package 51 further includes a first metal layer 10 provided on the first surface S<b>1 of the first heat sink layer 30 and connecting the plurality of first metal vias 32 . Thereby, heat is dispersed on the first surface S1. Therefore, the heat dissipation characteristics of the package 51 can be further enhanced.

The first metal layer 10 is arranged on the inner region RI of the first surface S1 away from the outer region RO of the first surface S1. As a result, the first metal layer 10 can be arranged intensively in the inner region RI of the first surface S1, which is particularly susceptible to heat. Therefore, the heat dissipation characteristics of the package 51 can be further improved while suppressing the adverse effects of the thermal expansion of the first metal layer 10 on the warp or stress of the package.

The first metal via 32 is made of a via material having a thermal conductivity of 200 W/m·K or more. Thereby, the heat dissipation characteristic of the package 51 can be further improved.

The via material includes copper. Thereby, the thermal conductivity of the via material can be easily increased.

The via material further includes tungsten. This makes it easier to form the first heat sink layer 30 by simultaneously firing the first ceramic layer 31 and the first metal vias 32 . Therefore, the first heat sink layer 30 can be formed at a lower cost.

The first ceramic layer 31 is made of a material containing alumina. This allows the first ceramic layer 31 to be made of a typical ceramic material for high frequency packages. Although the use of alumina, a material with poor thermal conductivity compared to metal, reduces the average thermal conductivity of the first heat sink layer 30, the reduction is at least partially due to the plurality of first metal vias 32. compensated. As a result, it is possible to prevent the heat radiation characteristic of the package 51 from becoming too small.

The ceramic frame 61 and the first ceramic layer 31 are made of the same material. Thereby, a difference in thermal expansion between the ceramic frame 61 and the first ceramic layer 31 can be avoided.

The volume ratio of the plurality of first metal vias 32 to the first heat sink layer 30 is 20% or more and 60% or less. By setting the volume ratio to 20% or more, the heat dissipation characteristics of the package 51 can be more sufficiently ensured. By setting the volume ratio to 60% or less, warpage or stress of the package 51 due to the difference in thermal expansion between the first heat sink layer 30 and the ceramic frame 61 can be more sufficiently suppressed. In addition, since the volume ratio of the first ceramic layer 31 to the first heat sink layer 30 is large, the green sheet that becomes the first ceramic layer 31 is less likely to be damaged by firing in the manufacturing process of the first heat sink layer 30 .

Package 51 further includes a second metal layer 20 . The second metal layer 20 is provided on the second surface S<b>2 of the first heat sink layer 30 and connects the plurality of first metal vias 32 . Thereby, heat is dispersed on the second surface S2. Therefore, the heat dissipation characteristics of the package 51 can be further enhanced.

The second metal layer 20 straddles the inner region RI and the outer region RO of the first surface S1 in plan view. Thereby, the heat is dispersed more widely on the second surface S2. Therefore, the heat dissipation characteristics of the package 51 can be further enhanced.

<Embodiment 2>
FIG. 8 is a schematic cross-sectional view showing the structure of the package 52 according to the second embodiment. In package 52, first metal via 32T is provided in first via hole VHT1 instead of first metal via 32 in first via hole VH1 in package 51 (FIG. 3: Embodiment 1). The first metal via 32T in the first via hole VHT1 is tapered from the first surface S1 of the first heat sink layer 30 toward the second surface S2. As a modification, both the first metal via 32 (FIG. 3) and the first metal via 32T (FIG. 8) may be used.

According to this embodiment, the first metal vias 32T are tapered from the first surface S1 of the first heat sink layer 30 toward the second surface S2. This shape enhances the efficiency of heat conduction from the first surface S1 to the second surface S2 by the first metal via 32T. Therefore, the heat dissipation characteristics of the package 52 can be more sufficiently ensured without increasing the proportion of the plurality of first metal vias 32T in the first heat sink layer 30 .

<Embodiment 3>
FIG. 9 is a schematic cross-sectional view showing the configuration of a package 53 according to the third embodiment.

The package 53 has a second metal layer 23 instead of the second metal layer 20 in the package 51 (FIG. 3: Embodiment 1). The second metal layer 23 , like the second metal layer 20 , connects the plurality of first metal vias 32 on the second surface S<b>2 of the first heat sink layer 30 . The second metal layer 23 may be formed of only a metallized layer without including a plated layer. In other words, the second metal layer 23 may consist only of a sintered body of metal powder. The second metal layer 23 straddles the inner region RI and the outer region RO of the first surface S1 in plan view.

Package 53 further includes a second heat sink layer 40 . The second heat sink layer 40 has a third surface S3 facing the second metal layer 23 and a fourth surface S4 opposite to the third surface S3. The third surface S3 may be in direct contact with the second metal layer. The second heat sink layer 40 includes a second ceramic layer 41 and a plurality of second metal vias 42 . The second ceramic layer 41 has a third surface S3 and a fourth surface S4, and a plurality of second via holes VH2 are provided between the third surface S3 and the fourth surface S4. The plurality of second metal vias 42 are arranged inside the plurality of second via holes VH2 of the second ceramic layer 41 . The plurality of second metal vias 42 are formed in at least the metal vias included in the inner region RI of the first surface S1 of the first heat sink layer 30 and the outer region RO of the first surface S1 of the first heat sink layer 30 in plan view. and partially contained metal vias.

Package 53 further includes a third metal layer 20A. The third metal layer 20</b>A is provided on the fourth surface S<b>4 of the second heat sink layer 40 and connects the plurality of second metal vias 42 . The third metal layer 20A straddles the inner region RI and the outer region RO of the first surface S1 in plan view. The third metal layer 20A includes the third metallized layer 21A directly provided on the fourth surface S4 of the second heat sink layer 40 and the third metallized layer 21A provided on the fourth surface S4 of the second heat sink layer 40 via the third metallized layer 21A. and the provided third plating layer 22A.

According to the present embodiment, the heat transferred in the thickness direction by the plurality of first metal vias 32 is diffused in the in-plane direction by the second metal layer 23, and then transferred in the thickness direction by the plurality of second metal vias 42. further transmitted in Thereby, the heat dissipation characteristic of the package 53 can be further improved.

The plurality of second metal vias 42 of the second heat sink layer 40 are not only the metal vias included in the inner region RI of the first surface S1 of the first heat sink layer 30 in plan view, but also the first metal vias of the first heat sink layer 30 . It also includes metal vias that are at least partially contained in outer region RO of surface S1. This allows the heat conduction paths to be more widely distributed in the second heat sink layer 40 . Therefore, the heat dissipation characteristics of the package 53 can be further enhanced.

7: mounting material 8: electronic component 9: wire (wiring member)
Reference Signs List 10: first metal layer 11: first metallized layer 12: first plated layer 20, 23: second metal layer 20A: third metal layer 21: second metallized layer 21A: third metallized layer 22: second plated layer 22A: Third plating layer 30: First heat sink layer 31: First ceramic layer 32, 32T: First metal via 40: Second heat sink layer 41: Second ceramic layer 42: Second metal via 51-53: Package 61 : Ceramic frame 65: Lead frame (metal terminal)
70: adhesive layer 80: lid 90: electronic device CV: cavity VH1, VHT1: first via hole VH2: second via hole

Claims (15)

A package having a cavity to be sealed by a lid,
a ceramic frame surrounding the cavity in plan view;
a first heat sink layer having a first surface having an inner region facing the cavity and an outer region supporting the ceramic frame, and a second surface opposite the first surface;
with
The first heat sink layer is
a first ceramic layer forming the first surface and the second surface and having a plurality of first via holes provided between the first surface and the second surface;
a plurality of first metal vias arranged in the plurality of first via holes of the first ceramic layer;
package, including. the plurality of first metal vias are positioned off the outer region of the first surface;
The package of Claim 1. further comprising a first metal layer provided on the first surface of the first heat sink layer and connecting the plurality of first metal vias;
3. Package according to claim 1 or 2. the first metal layer is disposed on the inner region of the first surface away from the outer region of the first surface;
4. Package according to claim 3. The first metal via is made of a via material having a thermal conductivity of 200 W/m·K or more,
5. A package according to any one of claims 1-4. the via material comprises copper;
6. Package according to claim 5. the via material further comprises tungsten;
7. Package according to claim 6. The first ceramic layer is made of a material containing alumina,
A package according to any one of claims 1-7. The ceramic frame and the first ceramic layer are made of the same material,
9. A package according to any one of claims 1-8. A volume ratio of the plurality of first metal vias in the first heat sink layer is 20% or more and 60% or less.
10. A package according to any one of claims 1-9. wherein the plurality of first metal vias comprises metal vias that taper from the first surface to the second surface of the first heat sink layer;
Package according to any one of claims 1 to 10. further comprising a second metal layer provided on the second surface of the first heat sink layer and connecting the plurality of first metal vias;
A package according to any one of claims 1 to 11. The second metal layer extends over the inner region and the outer region of the first surface in plan view,
13. Package according to claim 12. further comprising a second heat sink layer having a third side facing the second metal layer and a fourth side opposite the third side;
The second heat sink layer is
a second ceramic layer forming the third surface and the fourth surface and having a plurality of second via holes provided between the third surface and the fourth surface;
a plurality of second metal vias arranged in the plurality of second via holes of the second ceramic layer;
including,
14. Package according to claim 12 or 13. The plurality of second metal vias of the second heat sink layer are, in plan view, the metal vias included in the inner region of the first surface of the first heat sink layer and the first surface of the first heat sink layer. a metal via at least partially contained in the outer region of
15. Package according to claim 14.

Images