Monolithic microwave integrated circuit (MMIC) assembly and method for realizing same.

Abstract

The integrated circuit assembly includes an integrated circuit formed on one side of a substrate and a thermal spreading layer composed of silver ink printed directly on the opposite side of the substrate from the integrated circuit, the thermal spreading layer removing heat generated by the integrated circuit. The assembly also includes a heat sink thermally attached to the thermal spreading layer opposite the substrate, the heat sink being attached to the thermal spreading layer by printing the same material as the thermal spreading layer on the heat sink and pressing the spreading layer against the heat sink.

Description

[Technical Field]

[0001]

[0001] This disclosure relates generally to thermal spreaders for removing heat from integrated circuits, and more particularly to monolithic microwave integrated circuit (MMIC) assemblies that include a thermal spreading layer comprised of silver ink printed on the backside of a substrate. [Background technology]

[0002]

[0002] MMICs, sometimes called chips or dies, are generally fabricated by epitaxially growing layers of some semiconductor material, such as GaN, InP, silicon, etc., on some crystalline substrate, depending on the type of MMIC being made and what application it is intended for, such as a power amplifier, radio frequency switch, etc. As manufacturing and growth techniques improve, and as more components can be formed in smaller areas, the power density of MMICs continues to increase significantly, which creates many design challenges regarding adequate heat removal to prevent device degradation. MMICs are usually mounted on some type of heat sink to remove heat from the device and allow the power density of the device to be increased without degradation from overheating.

[0003] In one known heat removal design for an MMIC, a thermal spreading layer, such as a copper-diamond (CuDi) or silver-diamond (AgDi) metal matrix having a thickness of about 0.01 inches, is soldered to the backside of a substrate, e.g., a silicon carbide (SiC) substrate, using, for example, a gold-tin (AuSn) solder preform, on which the MMIC is formed. The matrix is ​​then adhesively attached, e.g., using Namics silver epoxy, to a heat sink, such as a block of copper, aluminum, tungsten, etc., where the heat sink may be part of a hermetically sealed housing for the MMIC.

[0004]

[0004] Thermal spreading layers for this purpose are designed to effectively spread heat throughout the spreading layer in order to rapidly and efficiently transfer heat from the MMIC to a heat sink. However, thermal spreading layers of the type mentioned above, which employ a metal preform matrix soldered to the MMIC substrate using preformed solder, are typically expensive, difficult to align and construct, and difficult to effectively thermally couple to the substrate. Summary of the Invention [Means for solving the problem]

[0005] The following discussion discloses and describes an integrated circuit assembly including an integrated circuit, such as an MMIC, formed on one side of a substrate and a thermal spreading layer composed of silver ink printed directly on the opposite side of the substrate, the thermal spreading layer conducting away heat generated by the integrated circuit. The assembly also includes a heat sink thermally coupled to the thermal spreading layer opposite the substrate, the heat sink being attached to the thermal spreading layer by printing the same material as the thermal spreading layer on the heat sink and pressing the spreading layer against the heat sink.

[0006]

[0006] Additional features of the disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an isometric view of an integrated circuit assembly including an MMIC and a printed metal heat spreading layer. [Figure 2] FIG. 2 is a side view of the integrated circuit assembly shown in FIG. [Figure 3]FIG. 2 is an illustration of an aerosol jet printer that can be used to print a heat spreading layer for the integrated circuit assembly shown in FIG. 1. [Figure 4] FIG. 2 is an illustration of an inkjet printer that can be used to print a heat spreading layer for the integrated circuit assembly shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0008]

[0011] The following discussion of embodiments of the disclosure directed to an integrated circuit assembly including a thermal spreading layer comprised of silver ink printed on the backside of a substrate is merely exemplary in nature and is in no way intended to limit the disclosure or its applications or uses.

[0009]

[0012] FIG. 1 shows an isometric view and FIG. 2 shows a side view of an integrated circuit assembly 10 including an integrated circuit 12, e.g., a GaN MMIC, fabricated or grown on a substrate 14, such as a SiC substrate, on which the integrated circuit 12 may be fabricated to include components for any suitable device, such as a power amplifier. The integrated circuit assembly 10 includes a thermally conductive heat spreading layer 18 printed from the integrated circuit 12 onto the backside of the substrate 14 using any suitable thermally conductive ink material, such as silver ink, to any suitable thickness, such as 0.012 inches (0.305 mm) using any suitable printing technique. The printing process typically provides a thickness of material of approximately 0.00254 mm (0.0001 inches) for each printing cycle. A thin layer 20 of thermally conductive ink material is also printed onto the top surface 22 of a heat sink 24, such as a metal block of aluminum, copper, tungsten, etc. The heat sink 24 may be part of a thermally conductive, hermetically sealed housing for the integrated circuit 12 and other integrated circuits. While layer 20 is still wet, spreading layer 18 is pressed into contact with layer 20, resulting in spreading layer 18 along with substrate 14 being adhered to heat sink 24 in a thermally coupled arrangement. By eliminating the solder preform used in known designs to thermally couple integrated circuits to heat spreaders, better thermal coupling can be achieved in a combination of less complex and less expensive processes.

[0010]

[0013] The spreading layer 18 may be printed onto the substrate 14 using any suitable printing process, such as inkjet printing, aerosol jet printing, screen printing, and selective plating. Figure 3 is an illustration of an aerosol jet printing apparatus 30, showing one suitable example. The apparatus 30 includes a container 32 of ink material 34, here a composition of silver particles, which receives an atomized gas, such as nitrogen, at an inlet 36 to generate an aerosol 38 that is delivered through a tube 40 where the aerosol 38 is heated by a heater 42. The heated aerosol 38 is delivered to a nozzle 44 which receives a sheath gas 46 at an inlet 48 to contain the aerosol 38 as it is emitted from the nozzle 44 and directed onto a substrate 50 as a printed trace 52, where the direction and amount of aerosol 38 sprayed from the nozzle 44 is controlled by a computer 54.

[0011]

[0014] 4 is an illustration of an inkjet printing apparatus 60, showing another suitable example. The apparatus 60 includes a tube 62 that confines an ink material 64, here a silver composition, which receives a compressed gas, such as air, at an inlet 66 that forces the material 64 out of a nozzle 68 and onto a substrate 70 as a printed trace 72, where the direction and amount of ink sprayed from the nozzle 68 is controlled by a computer 74.

[0012]

[0015] The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. Those skilled in the art will readily appreciate from such discussion and from the accompanying drawings and claims that various changes, modifications, and variations can be made therein without departing from the spirit and scope of the disclosure, as defined in the following claims.

Claims

1. A substrate; an integrated circuit formed on one side of the substrate; a thermal spreading layer printed on an opposite side of the substrate from the integrated circuit, the thermal spreading layer removing heat generated by the integrated circuit; a heat sink thermally attached to the thermal spreading layer opposite the substrate; a thin layer of the same material as the thermal spreading layer printed on the heat sink; Equipped with the thin layer being the only layer between the thermal spreading layer and the heat sink.

2. The assembly of claim 1 , wherein the thermal spreading layer is printed directly onto the substrate.

3. The assembly of claim 1 , wherein the thermal spreading layer is a silver composition.

4. The assembly of claim 1 , wherein the heat sink is attached to the thermal spreading layer by pressing the spreading layer against the thin layer on the heat sink.

5. 10. The assembly of claim 1, wherein the heat sink is part of a hermetically sealed housing for the integrated circuit.

6. The assembly of claim 1 , wherein the substrate is a silicon carbide substrate.

7. 10. The assembly of claim 1, wherein the integrated circuit is a monolithic microwave integrated circuit (MMIC).

8. The assembly of claim 1 , wherein the thermal spreading layer is approximately 0.012 inches thick.

9. The assembly of claim 1 , wherein the thermal spreading layer is printed onto the substrate using an aerosol printer or an inkjet printer.

10. A substrate; a monolithic microwave integrated circuit (MMIC) formed on one side of the substrate; a thermal spreading layer comprised of silver ink printed directly on the opposite side of the substrate from the MMIC, the thermal spreading layer removing heat generated by the MMIC; a heat sink thermally attached to the thermal spreading layer opposite the substrate; a thin layer of the same material as the thermal spreading layer printed on the heat sink; Equipped with only the thin layer is formed between the thermal spreading layer and the heat sink; an integrated circuit assembly attached to the thermal spreading layer by pressing the spreading layer against the thin layer on the heat sink;

11. The assembly of claim 10 , wherein the heat sink is part of a hermetically sealed housing for the integrated circuit.

12. 11. The assembly of claim 10, wherein the thermal spreading layer is approximately 0.012 inches thick.

13. The assembly of claim 10 , wherein the thermal spreading layer is printed onto the substrate using an aerosol printer or an inkjet printer.

14. 1. A method for providing an integrated circuit assembly, comprising: providing a substrate; forming an integrated circuit formed on one side of the substrate; printing a thermal spreading layer on the opposite side of the substrate from the integrated circuit, the thermal spreading layer removing heat generated by the integrated circuit; thermally attaching a heat sink to the thermal spreading layer opposite the substrate; Including, the step of attaching the heat sink to the thermal spreading layer includes printing a thin layer of the same material as the thermal spreading layer on the heat sink; The method, wherein only the thin layer is formed between the thermal spreading layer and the heat sink.

15. The method of claim 14 , wherein printing the thermal spreading layer comprises printing the spreading layer directly onto the substrate.

16. The method of claim 14 wherein the thermal spreading layer is a silver composition.

17. The method of claim 14 , wherein attaching the heat sink to the thermal spreading layer comprises pressing the spreading layer against the thin layer on the heat sink.

18. The method of claim 14 , wherein printing the thermal spreading layer onto the substrate comprises using an aerosol printer or an inkjet printer.

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