CN212113698U - A high thermal conductivity heat sink - Google Patents

Abstract

The utility model provides a heat dissipation device with high thermal conductivity. The device is composed of a base plate with high thermal conductivity, an enclosing frame and a cover plate in sequence from bottom to top; at least one layer of HTCC substrate is arranged on the base plate with high thermal conductivity and inside the enclosing frame. At least one side of the upper and lower surfaces of the single-layer HTCC substrate is used for placing heating devices; the side connecting the HTCC substrate with the high thermal conductivity base plate is not placed with heating devices. The high-heat-conductivity heat-dissipating device provided by the utility model utilizes a large-area HTCC base plate and a diamond-aluminum base plate, which solves the heat dissipation problem of the high heat flux density heating chip of the microwave power module.

Description

A high thermal conductivity heat sink

technical field

The utility model relates to the field of microwave power modules, in particular to a heat dissipation device with high thermal conductivity.

Background technique

Microwave power modules are widely used in military and civilian fields such as radar, electronic countermeasures, and communications. With the development of GaN third-generation semiconductor materials, the integration and power continue to increase, the heat generation of microwave power modules has doubled, and the heat flow of X-band power chips. The density reaches 200W/cm2 or even higher, which poses a great challenge to the heat dissipation capability of the module, especially the heat conduction.

At present, in the domestic military or civilian fields, the heat sink of the heating chip of the microwave power module mostly adopts the second-generation thermal management materials such as tungsten copper, copper-molybdenum copper, etc. For example, it is mentioned in the patent CN201310001249.X "Laminated Structure Heat Sink Material and Preparation Method" The copper-molybdenum-copper heat sink material adopts three-layer composite to realize the preparation of molybdenum-copper or tungsten-copper heat sink. The copper-molybdenum-copper heat sink material mentioned in the patent CN200910213372.1 "Copper-Molybdenum-Copper Heat Sink Material and Preparation Method". The package shell is Kovar, Al-Si and other first- to third-generation thermal management materials, such as the Kovar package shell mentioned in the patent CN201810044629.4 "Preparation method of Kovar alloy wall for electronic packaging", patent CN201510812388.X The aluminum-silicon shell packaging material mentioned in "a preparation method of gradient aluminum-silicon electronic packaging material". In some high-end application fields, the fourth-generation heat sink materials such as diamond aluminum and diamond copper have been gradually applied. The heat sink material mentioned in the patent CN201520980982.5 "Diamond Copper Heat Sink Material". Although the thermal conductivity of diamond-based composite materials is as high as about 600W/m/K, which is about 3 times that of aluminum, due to the existence of diamond particles, it is difficult to process and high in cost. Generally, the flat structure can only be realized by grinding. For the package shell of the microwave power module, it is necessary to design the power supply and radio frequency interface to install the connection terminals, and there must be fine and complex structures such as threads, chamfers, stepped holes, etc., which can only be completed by machining, thus limiting the diamond base The application of composite materials on packaging shells, so the application of diamond matrix composite materials on packaging shells has not been reported.

In addition, in microwave power modules, LTCC substrates are widely used. With the expansion of substrate functions and the improvement of integration, the usable area of power chip heat sinks gradually decreases. In high frequency bands such as Ka, the heat sink area is even comparable to that of chips. play a heat-expanding effect. Under the demand of high thermal conductivity, HTCC (High Temperature co-fired Ceramic, high temperature co-fired ceramic) substrates are also gradually used, such as the substrate material mentioned in the patent CN201811144572.1 "A four-channel microwave T/R component", patent The HTCC substrate mentioned in CN201520794769.5 "a high-density assembly structure of a TR component" also has the problem of insufficient heat spreading area of the heat sink.

On the whole, in order to improve the heat dissipation capacity of high-power microwave power modules, it is urgent to solve the technical problems of how to realize the application of diamond-based high thermal conductivity materials as packaging shells, and how to improve the thermal expansion capacity of heat sinks.

Utility model content

The purpose of the present utility model is to solve the above problems, and proposes a high thermal conductivity heat dissipation device. At least one layer of HTCC substrate, at least one of the upper and lower surfaces of the single-layer HTCC substrate is used for placing heating devices; the side of the HTCC substrate connected to the high thermal conductivity base plate is not placed with heating devices.

Further, the heating device is a chip, and the power of any chip except the lowermost chip is not greater than the power of the chip located below it.

Further, the high thermal conductivity base plate is a diamond-aluminum composite material, and the difference between the thermal expansion coefficients of the HTCC substrate and the high thermal conductivity base plate is greater than or equal to -3ppm/K and less than or equal to 3ppm/K.

Further, the HTCC substrate is one layer, the upper surface is provided with a cavity, the cavity is used for placing chips, the surface of the chip in the cavity is located between the upper and lower surfaces of the HTCC substrate, and the chip is located in the cavity. Dislocation distribution in the vertical direction.

Further, a multi-layer HTCC substrate is arranged in the enclosing frame, and the HTCC substrate is stacked on a high thermal conductivity base plate; except for the chips arranged on the upper surface of the uppermost HTCC substrate, other chips are arranged through the cavity on the surface of the HTCC substrate, The surfaces of the chips in the cavity are located between the upper and lower surfaces of the HTCC substrate where the chips are located, and the chips are staggered and distributed in the vertical direction.

Further, the bottom surface of the surrounding frame is provided with locating pins, and holes are drilled in the corresponding positions of the high thermal conductivity base plate for coordinating and positioning with the locating pins.

Compared with the prior art, the utility model has the following advantages:

(1) The large-area HTCC substrate is used to solve the difficult problem of heat expansion of the high heat flux density heating chip of the microwave power module;

(2) The use of diamond/aluminum composite bottom plate solves the problem of heat conduction temperature rise of the shell of the microwave power module, and at the same time, the effective secondary heat expansion further reduces the heat flow density and reduces the contact temperature rise between the module and the cold plate ;

(3) By using different types of materials for the bottom plate, enclosure and cover plate and composite connection, the problems of difficult processing, high density and high cost caused by the direct use of high thermal conductivity materials for microwave power modules are solved.

Description of drawings

FIG. 1 is an overall assembly view of the first embodiment.

FIG. 2 is an exploded view of the first embodiment.

FIG. 3 is an assembly view of the enclosure frame and the high thermal conductivity bottom plate of the first embodiment.

FIG. 4 is a schematic diagram of a traditional heat transfer mode of a microwave power module.

FIG. 5 is a schematic diagram of the heat transfer mode of the microwave power module applying the present invention.

FIG. 6 is a partial schematic diagram of the first embodiment.

FIG. 7 is a cross-sectional view taken along the line A-A in FIG. 6 .

The meanings of the symbols in the figure are:

Cover plate 1 , enclosure frame 2 , high thermal conductivity base plate 3 , upper layer HTCC substrate 4 , lower layer HTCC substrate 5 , low power chip 6 , high power chip 7 .

Detailed ways

The present utility model will be described in further detail below in conjunction with the accompanying drawings.

Aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure are not necessarily intended to include all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in greater detail below, can be implemented in any of a number of ways, since the concepts and embodiments disclosed herein do not Not limited to any implementation. Additionally, some aspects of the present disclosure may be used alone or in any suitable combination with other aspects of the present disclosure.

Example 1

The schematic diagrams of the high thermal conductivity heat dissipation device proposed by the present invention are shown in Figures 1 and 2 . An upper-layer HTCC substrate 4 and a lower-layer HTCC substrate 5 are packaged in the device; a low-power chip 6 and a high-power chip 7 are arranged on the HTCC substrate 4 and the lower-layer HTCC substrate 5 .

The base plate 3 with high thermal conductivity is a diamond-aluminum composite material. By adjusting the volume fraction of diamond, the thermal expansion coefficient of the base plate is matched with that of the HTCC substrate. Generally, the thermal expansion coefficient of the HTCC substrate is 4-5ppm/K (ppm/K is the temperature coefficient). When the volume fraction of diamond in the diamond aluminum reaches more than 70%, the thermal expansion coefficient of the diamond aluminum composite material can reach about 7ppm/K. , to meet the requirement that the difference between the thermal expansion coefficients of the two-layer welding interface is greater than or equal to -3ppm/K and less than or equal to 3ppm/K. On the surface of the high thermal conductivity base plate 3, in the preparation process such as high pressure casting, an aluminum metal layer can be directly formed. If the pressure infiltration process is used, it needs to be ground and then plated with a metal layer, such as titanium plating and then copper plating, so as to meet the requirements of the HTCC substrate. Requirements for large-area connections by soldering. The thickness of the single-sided aluminum metal layer or metal plating layer is controlled at 50um, which is equivalent to the thickness of general gold-tin solder. The thermal expansion coefficient has little effect, which can ensure the thermal matching of the base plate and the HTCC substrate, as well as the requirements for surface metallization of soldering. High thermal conductivity base plate and frame are connected by soldering.

The heat transfer path of the upper HTCC substrate 4 is far away. Since the upper layer is unobstructed, the low-power chip 6 can be surface-mounted or welded on the upper surface, or the low-power chip 6 can be welded through the cavity 5-1, as shown in Figures 6 and 7. The surface of the cavity 5-1 is located between the upper and lower surfaces of the HTCC substrate where it is located. The heat transfer path of the lower HTCC substrate 5 is close, and the high-power chips 7 arranged in an array can be welded. Since the upper surface of the lower HTCC substrate 5 needs to be welded with the lower surface of the upper HTCC substrate 4 in a large area, it can only be concave on the upper surface. In the cavity 5-1, the high-power chip 7 is soldered in the cavity 5-1, and the height of the chip soldered in the cavity 5-1 is lower than the surface of the HTCC substrate 4. The lower HTCC substrate 5 is welded to the high thermal conductivity base plate 3, and no chips are placed on the welding surface. The lower-layer HTCC substrate 5 and the upper-layer HTCC substrate 4 are connected by BGA or large-area soldering. The heat transfer path is (low-power chip 6 → upper-layer HTCC substrate 4 ) → (high-power chip 7 → lower-layer HTCC substrate 5 ) → high thermal conductivity base plate 3 . The low-power chip 6 and the high-power chip 7 should be dislocated in the vertical direction to form a reasonable heat dissipation path.

There are a variety of matching options for the frame 2 and the cover plate 1. If priority is given to low cost, Al6061 can be selected for the enclosing frame 2, which is generated in the preparation process of the high thermal conductivity base plate 3 such as high pressure casting or pressure infiltration, which avoids re-plating the metal layer, and Al4047 is selected for the cover plate 1; Silicon and other packaging shell processes are compatible, the frame 2 can choose aluminum silicon alloy (AlSi50), after nickel plating and gold plating, it is welded to the high thermal conductivity base plate 3, and the cover plate 1 chooses aluminum silicon alloy (AlSi27); if high strength and high reliability are considered , the enclosing frame 2 can choose titanium alloy (TC4), the connection method is similar to that of aluminum silicon alloy, and the cover plate 1 can choose titanium alloy (TA2). The enclosing frame 2 and the cover plate 1 are connected by a laser hermetic welding process. As shown in FIG. 3 , when the surrounding frame 2 is made of aluminum-silicon alloy or titanium alloy, in order to ensure the precise fixation of the large-sized surrounding frame and the high thermal conductivity bottom plate 3 during welding, the bottom surface of the surrounding frame 2 adopts circular or quadrangular positioning pins 2 -1. Drill holes in the corresponding position of the high thermal conductivity base plate 3 for matching and positioning. The surrounding frame 2 and the high thermal conductivity base plate 3 are connected by soldering.

The overall connection process of the device is two-step ladder welding and one-step sealing welding, specifically:

First, the high thermal conductivity base plate 3 and the surrounding frame 2 are welded, positioned and matched, and a fixture is used. The highest welding temperature is used, and gold-tin solder can be selected. The welding temperature is about 283°C to form a package housing without cover plate 1 .

Secondly, on the HTCC substrate, use gold-tin solder or conductive silver glue with a temperature resistance of more than 300 ° C to connect the chip and the HTCC substrate, including the connection between the high-power chip 7 and the lower HTCC substrate 5, and the low-power chip 6 and the upper HTCC substrate 4. , to form 2 single-layer HTCC substrates with heating chips; after that, superimpose the 2 single-layer HTCCs with heating chips, and weld them with the package shell in a large area, optional tin-lead solder, and the welding temperature is about 183 ℃.

Finally, laser hermetic welding is performed on the cover plate 1 and the package shell to ensure the air tightness requirements when applied to the microwave power module.

Embodiment 2

This embodiment is basically the same as the first embodiment, except that the lower surface of the upper HTCC substrate is provided with a cavity 5-1, and a low-power chip 6 is welded in the cavity 5-1, and the surface of the low-power chip 6 is located at between the upper and lower surfaces of the HTCC substrate.

Embodiment 3

This embodiment is basically the same as the first embodiment, except that the HTCC substrate in this embodiment is a single layer. The upper surface of the single-layer HTCC substrate is surface-mounted or welded with a low-power chip 6, and the side connected to the high thermal conductivity base plate 3 is not provided with a chip.

The utility model utilizes the large-area HTCC substrate to solve the problem of heat expansion of the heating chip with high heat flux density of the microwave power module;

The utility model utilizes the diamond/aluminum composite bottom plate to solve the problem of the heat conduction temperature rise of the shell of the microwave power module, and at the same time, the effective secondary heat expansion further reduces the heat flow density and reduces the contact temperature rise between the module and the cold plate ;

The utility model solves the engineering problems of difficult processing, high density and high cost caused by directly adopting high thermal conductivity materials for the microwave power module by adopting different types of materials for the bottom plate, the enclosing frame, the cover plate and the composite connection.

FIG. 4 shows a traditional heat transfer method with narrow heat transfer paths and large thermal resistance, while the heat transfer method of the third embodiment of the present invention is shown in FIG. 5 , with wide heat transfer paths, low heat flow and low thermal resistance.

To sum up, compared with the traditional molybdenum-copper heat sink and aluminum, aluminum-silicon or aluminum-carbon-silicon packaging shell, the high thermal conductivity heat dissipation device provided by the present invention has a wider effective heat transfer path, which can quickly dissipate the high thermal conductivity at the chip. The heat flux density is reduced to a low heat flux density, and the total thermal conduction resistance is small. The special composite structure design of the bottom plate, the enclosure frame and the cover plate is adopted to meet the production and processing requirements of easy processing, light weight, economy, air tightness, etc. A cold plate or radiator for heat exchange creates good prerequisites,

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection of the utility model.

Claims (6)

1. A high heat conduction heat dissipation device is characterized in that the device consists of a high heat conduction bottom plate (3), a surrounding frame (2) and a cover plate (1) from bottom to top in sequence; at least one layer of HTCC substrate is arranged on the high-heat-conductivity bottom plate (3) and in the enclosing frame (2), and at least one surface of the upper surface and the lower surface of the single-layer HTCC substrate is used for placing a heating device; and a heating device is not arranged on one side of the HTCC substrate connected with the high heat conduction bottom plate (3).

2. A heat sink with high thermal conductivity as claimed in claim 1, wherein the heat generating device is a chip, and the power of any chip except the lowest chip is not greater than that of the chip below the chip.

3. The high thermal conductivity heat sink according to claim 2, wherein the high thermal conductivity base plate (3) is a diamond-aluminum composite, and the difference between the thermal expansion coefficients of the HTCC substrate and the high thermal conductivity base plate (3) is equal to or greater than-3 ppm/K and equal to or less than 3 ppm/K.

4. The HTCC substrate of claim 3, wherein said HTCC substrate is a layer, and the upper surface of said HTCC substrate is provided with a cavity (5-1), said cavity (5-1) is used for placing a chip, and the surface of the chip in said cavity (5-1) is located between the upper surface and the lower surface of the HTCC substrate.

5. The high thermal conductivity heat sink according to claim 3, wherein multiple layers of HTCC substrates are disposed in the enclosure frame (2), and the HTCC substrates are stacked on the high thermal conductivity bottom plate (3); except the chips arranged on the upper surface of the uppermost HTCC substrate, other chips are arranged through a cavity (5-1) on the surface of the HTCC substrate, the surfaces of the chips in the cavity (5-1) are positioned between the upper surface and the lower surface of the HTCC substrate, and the chips are distributed in a staggered mode in the vertical direction.

6. The high heat conduction and dissipation device as claimed in claim 4 or 5, wherein the bottom surface of the enclosure frame (2) is provided with positioning pins (2-1), and holes are punched at corresponding positions of the high heat conduction bottom plate (3) to be matched with the positioning pins (2-1) for positioning.

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