JPH04262562A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device having high heat dissipation and a reduced weight by securing a heat sink having a spongy metal skeleton to part of a surface of a ceramic board. CONSTITUTION:A chip placing plate 17 is brazed on a metallized layer of a ceramic board 1 with a brazing material 19A in a cavity 3 at a center of the board 1, an IC chip 2 is placed on the plate 17, and chip pads are connected to bonding conductors 4 via wires 4A. Further, in order to protect the chip 2, a cap 15 is sealed at a lower side of the cavity by using a brazing material 19. A heat sink 11 having a spongy metal skeleton is connected to the surfaces of the board 1 for constituting a face down package and the plate 17 via solder 13. Thus, a semiconductor device having high heat dissipation and a reduced weight can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor devices, and more particularly to the structure of a heat sink for a semiconductor device that consumes a large amount of power.

0002

[Prior art] Recent high-polar LSIs and MOSLSIs
In semiconductor devices such as the There is. In particular, as patterns become finer, element dimensions and wiring widths become smaller, the degree of integration improves, and power consumption increases. Therefore, the heat generation density (power/volume) increases dramatically. Furthermore, an increase in the number of input/output pins due to the increase in the functions of semiconductor devices is unavoidable.

Under these circumstances, a pin grid array (hereinafter referred to as PGA) with a face-up structure as shown in FIG. 4 has been proposed as a general semiconductor device package that mounts a conventional large chip with many pins. There is. This PGA is a full grid PGA in which external leads 6 are attached to the entire back surface of the ceramic substrate 1. A cavity 6 is provided in the center of the ceramic substrate 1, and a bonding conductor 4 provided around the cavity is connected to an external lead 6 extending toward the outside of the substrate via an internal conductor 5. Then, the IC chip 2 is fixed in the cavity 3, and the chip pad and the bonding conductor 4 are connected by a wire 4A. In addition, a metal cap 8 is attached to the metal seal ring 7.
The seal ring 7 and the outer periphery of the metal cap 8 are electrically resistance welded to seal the cap. Therefore, P of this structure
The GA can have a package structure that allows high-density mounting of many pins in a minimum area.

Next, when mounting this PGA on a printed circuit board 21A, the external leads 6 of the package are inserted into the through hole 10 up to the lead stopper 6A and soldered using a solder flow. The distance between the bottom of the ceramic substrate 1 and the printed board 21A is 1 mm to relieve stress after fixing with the solder 13A.
They are spaced apart. However, this soldered-mounted PGA has a drawback in that the heat radiation effect is small because the chip heat radiation surface is on the printed board side. As a countermeasure for this, as shown in FIG.
A structure in which heat sinks 16A are connected at intervals of mm has been proposed.

[0005] In this heat sink 16A, a hole is provided in the aluminum plate into which the external lead 6 of the PGA can be inserted, and the hole is concave so that it can be closely attached to the bottom and side surfaces of the ceramic substrate 1. . The aluminum surface processed into this shape is anodized to provide insulation. If this is mounted by soldering as shown in FIG. 5, heat can be rapidly radiated from the back surface of the ceramic substrate 1 due to thermal conduction. However, the PGA of this structure also has the disadvantage that the heat sink 16A has a small specific surface area that is related to the hole-drilling workability and heat dissipation properties, so the heat dissipation effect is small and the cost is high.

FIG. 6 shows a PGA with a face-down structure, and the mounting density is slightly lower, but the heat sink is Cu-
Since it can be directly bonded to the chip mounting board 17 made of W alloy, the heat dissipation effect is high. However, in order to increase heat dissipation into the air, the heat sink 16B itself needs to have a large surface area, but a fin-type heat sink has its limitations. For example, when the external dimensions are length and width 43 mm, height 7.5 mm, fin groove width 1 mm, and fin width 1 mm, the specific surface area (surface area m2 / volume m3
) was 860.

[0007]

Problems to be Solved by the Invention Among the conventional semiconductor devices described above, the face-up structure PGA shown in FIG.
Although this structure allows the highest density per unit area and is suitable for increasing the number of pins, it has poor heat dissipation because the printed circuit board and the bottom of the package are not in contact with each other in the mounting structure. As shown in Figure 5, an improved structure is one in which a heat sink is attached to the front, side, and back surfaces of the ceramic substrate (between the printed circuit board and the package external conductor). ,
The disadvantage was that the heat sink was difficult to manufacture and expensive. In addition, in the face-down structure shown in Fig. 6,
Heat dissipation was also poor because the connection area between the package and the heat sink was small.

Furthermore, since conventional heat sinks for both face-up and face-down structures mainly use aluminum, silicone resin 12 is used on ceramic substrate 1.
If stress relaxation due to the difference in thermal expansion is not achieved by adhering the ceramic substrate with a bonding agent or the like, a phenomenon will occur in which the ceramic substrate will crack. Therefore, there was a drawback that heat conduction was inhibited by the resin adhesive.

[0009]

[Means for Solving the Problems] A semiconductor device of the present invention includes:
A ceramic substrate having a cavity, a semiconductor chip mounted in the cavity, an external lead provided on the bottom or peripheral part of the ceramic substrate, and a spongy lead fixed to at least a part of the surface of the ceramic substrate. A heat sink having a metal skeleton is included.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a sectional view of a first embodiment of the present invention, showing the case where the present invention is applied to a PGA with a face-down structure.

In FIG. 1, a cavity 3 is provided in the center of a ceramic substrate 1, and within this cavity 3, a chip mounting plate 17 made of a Cu-W alloy or the like is mounted on a metallized layer of the ceramic substrate 1. Cu brazing material 19
It is brazed at A. A bonding conductor 4 is provided on the ceramic substrate 1 around the cavity 3 and is connected to an external lead 6 via an internal conductor 5. An IC chip is mounted on the chip mounting board 17, and the chip pad and the bonding conductor 4 are connected by a wire 4A. Furthermore, in order to protect the IC chip 2, a cap 15 made of ceramic or metal is made of low melting point glass or Au.
- The lower side of the cavity is sealed using a soldering material 19 of Sn. On the surfaces of the ceramic substrate 1 and the chip mounting board 17 that constitute this face-down package,
A heat sink 11 having a spongy metal skeleton is bonded with solder 13 to improve heat dissipation. The material itself of this heat sink 11 has a total volume of 93 to 9
It has 8% pores, each pore is connected to its neighbor, and the specific surface area (m2/m3) has a value of 500 to 1700.

According to the first embodiment configured as described above, the external dimensions are 40 mm in length and width, and 7.5 mm in height.
When using a mm heat sink, the thermal resistance of the semiconductor device was improved to 4°C/W in the example, compared to 6°C/W for the conventional type semiconductor device at a wind speed of 1.5 m/sec. . Furthermore, since the heat sink has a porosity of 93 to 98%, it has become possible to reduce the weight.

Next, a method of manufacturing this heat sink will be explained. First, foam resin is injected and molded into a mold that matches the shape of the heat sink to prepare foam resin that has the same shape as the heat sink. Next, conductive treatment is applied to the surface of this foamed resin and the surfaces of the internal cells. Generally, carbon powder is electrodeposited. Next, electroplating is performed to form a metal skeleton. This skeleton is connected in a three-dimensional mesh like a sponge. The thickness of this skeleton can be controlled by the electroplating time. The metal material serving as the skeleton may be Ni, Ni-Cu, Cu, or any other material that can be plated. Next, the foamed resin trapped inside the plating is heated to be decomposed and removed. Next, alloying,
It is processed and made into a heat sink.

FIG. 2 is a sectional view of a second embodiment of the present invention, showing the case where the present invention is applied to a PGA having a face-up structure.

In FIG. 2, this PGA has an external lead 6
This is a full-grid PGA in which a cavity 3 is provided in the center of the ceramic substrate 1 on the side opposite to the mounting surface of the external leads 6, and a bonding conductor 4 is extended toward the outside of the substrate from the periphery of the cavity 3. and is connected to the external lead 6. Then, the IC chip 2 is fixed on the ceramic substrate 1 in the cavity 3, and the chip pad and the bonding conductor 4 are connected by wires 4A. Further, a metal cap 8 is placed on the metal seal ring 7, and the seal ring and the outer periphery of the cap are electrically resistance welded to seal the cap. Therefore, a package capable of high-density mounting with a large number of pins in a minimum area is completed. Next, the heat sink 11A is fixed with solder or resin to the surfaces of the ceramic substrate 1 and the metal cap 8 that constitute the package. Similarly, on the bottom and side surfaces of the ceramic substrate 1,
A concave heat sink 11B having a through hole is fixed by a fitting method or the like. In particular, in order to insulate the external leads 6 and the through holes 10, this heat sink 11B is made by impregnating the entire heat sink with molten aluminum to adhere aluminum to the metal surface, and then performing alumite treatment to form an oxide film of about 10 μm. It needs to be generated. The thus constructed second embodiment is mounted on the printed circuit board 21 by soldering to the external leads 6 in the same manner as in the prior art.

FIG. 3 is a sectional view of a third embodiment of the present invention, in which a heat sink 11C is soldered onto a Cu--W alloy chip mounting plate 17A constituting a flat package. In the third embodiment, as in the first embodiment, improvements in thermal resistance and weight reduction can be made.

[0017]

As described above, the present invention has the advantage that by using a heat sink having a spongy metal skeleton, a semiconductor device with good heat dissipation and reduced weight can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the invention.

FIG. 2 is a sectional view of a second embodiment of the invention.

FIG. 3 is a sectional view of a third embodiment of the invention.

FIG. 4 is a cross-sectional view of a conventional semiconductor device.

FIG. 5 is a cross-sectional view of a conventional semiconductor device.

FIG. 6 is a cross-sectional view of a conventional semiconductor device.

[Explanation of symbols]

1 Ceramic substrate 2 IC chip 3 Cavity 4 Bonding conductor 4A Wire 5 Internal conductor 6 External lead 6A Stopper 7 Seal ring 8 Metal cap 10 Through holes 11, 11A to 11C Heat sink 12
Silicon resin 13, 13A Solder 15 Cap 16, 16A, 16B Heat sink 17, 17
A Chip mounting plate 19, 19A Brazing material

Claims (1)

[Claims] 1. A ceramic substrate having a cavity, a semiconductor chip mounted in the cavity, an external lead provided on the bottom or peripheral part of the ceramic substrate, and fixed to at least a part of the surface of the ceramic substrate. and a heat sink having a spongy metal skeleton.