A flip chip structure

Abstract

The application discloses a flip chip structure, relates to the chip technical field, and is used for reducing the chip junction shell thermal resistance, increasing the temperature uniform distribution of the chip, reducing the local temperature of the chip, improving the upper limit of the chip power, and solving the chip heat dissipation problem of the closed space. The flip chip structure comprises a chip body, a substrate and a shell, the chip body is arranged on the substrate; the shell has a first opening end and a first closed end which are oppositely arranged, and the first opening end is arranged on the substrate. A connecting part extending to the center of the shell is arranged on the inner wall of the shell, the connecting part is matched with the chip body, the connecting part is sealingly connected with the side of the chip body away from the substrate, the connecting part is used for forming a first cavity and a second cavity in the cavity of the shell, the chip body is arranged in the second cavity, and a phase change material is arranged in the first cavity and / or the second cavity.

Description

Technical Field

[0001] This invention relates to the field of chip technology, and more particularly to a flip-chip structure. Background Technology

[0002] Flip-chip packaging technology, as one of the mainstream chip packaging technologies, boasts advantages such as high computing power, high speed, high bandwidth, low latency, low power consumption, multifunctionality, and system-level integration. Flip-chip packaging can reduce the resistance and inductance between the chip and the substrate, improving signal transmission speed and performance. Furthermore, based on the chip's doping characteristics, transistor performance improves as temperature decreases; flip-chip packaging can enhance the chip's heat dissipation performance, effectively reducing the chip's junction temperature, thereby improving the chip's computing performance and stability.

[0003] The junction-to-case thermal resistance (JTR) of a flip chip refers to the thermal resistance between the chip junction and the package shell, and is an important indicator of the chip's heat dissipation performance. The package shell is typically made of nickel-plated copper, with the back of the bare chip contacting the inner surface of the package shell via a thermal interface material, resulting in a relatively high JTR. Aircraft-borne electronic equipment primarily uses flip chips such as FPGAs (Field Programmable Gate Arrays). Due to limitations imposed by gravity variations, temperature changes, enclosed spaces, lack of air / liquid supply, and size and weight, the main heat dissipation method for flip chips is a back-side metal heat sink connected by a thermal interface material, passively absorbing the heat dissipation during chip operation using the heat capacity of the metal structure. However, with increasing chip integration and rising heat output and heat flux density, traditional metal heat sinks are no longer sufficient for heat dissipation requirements. Furthermore, because chips have multiple heat-generating junctions with uneven heat distribution and varying power densities, localized overheating problems can occur. Summary of the Invention

[0004] The purpose of this invention is to provide a flip-chip structure that reduces the chip junction thermal resistance, increases the uniformity of chip temperature distribution, reduces local overheating of the chip, increases the chip power limit, and solves the heat dissipation problem of chips in enclosed spaces.

[0005] To achieve the above objectives, the present invention provides a flip-chip structure, comprising a chip body, a substrate, a housing, and a phase change material. The chip body is disposed on the substrate. The housing has a first open end and a first closed end disposed opposite to each other, the first open end being disposed on the substrate. A connecting portion extending towards the center of the housing is provided on the inner wall of the housing. The connecting portion cooperates with the chip body and is sealed to the side of the chip body away from the substrate, thereby forming a first cavity and a second cavity within the housing. The chip body is located within the second cavity, and the phase change material is accommodated within the first cavity and / or the second cavity.

[0006] When the above technical solution is adopted, since the connecting part cooperates with the chip body and is sealed to the side of the chip body away from the substrate, the cavity of the housing forms a first cavity and a second cavity. When a phase change material is disposed in the first cavity, the phase change material can directly contact the side of the chip body away from the substrate and generate heat exchange. The phase change material can directly absorb the heat of the chip body and carry away the heat, thereby reducing the temperature of the chip body. Furthermore, when a phase change material is disposed in the second cavity, the chip body is located in the second cavity, and the phase change material can directly contact the chip body and generate heat exchange. The phase change material can directly absorb the heat of the chip body and carry away the heat, thereby reducing the temperature of the chip body.

[0007] Compared to existing traditional technologies, the heat transport path of a flip chip is primarily upward: the heat generated by the chip is transported to the housing via a first thermal interface material on the back of the chip, and then to the metal heat sink for heat dissipation via a second thermal interface material. The presence of the first thermal interface material within the flip chip structure results in a relatively high junction-to-case thermal resistance, limiting the chip's heat dissipation capacity. The flip chip structure provided by this invention eliminates the thermal interface material and utilizes phase change heat transfer, allowing the phase change material to directly contact the chip body and directly cool it. This reduces junction-to-case thermal resistance, improves the uniformity of chip temperature distribution, mitigates localized overheating, increases the chip's power limit, and meets the requirements for efficient heat dissipation and rapid temperature equalization. Simultaneously, it solves the passive heat dissipation problem of flip chips in variable gravity enclosed environments. Attached Figure Description

[0008] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0009] Figure 1 A schematic diagram of a flip-chip structure provided in an embodiment of the present invention. Figure 1 ;

[0010] Figure 2 A schematic diagram of a flip-chip structure provided in an embodiment of the present invention. Figure 2 ;

[0011] Figure 3 A schematic diagram of a flip-chip structure provided in an embodiment of the present invention. Figure 3 .

[0012] Figure label:

[0013] 1-Chip body, 11-Micro-nano reinforced surface structure, 2-Substrate, 3-Housing shell, 31-First cavity,

[0014] 32-Second cavity, 33-Return liquid column, 34-Connecting part, 41-Gas-liquid phase change material, 42-Solid-liquid phase change material, 421-Metal nanoparticles, 5-Skeleton structure. Detailed Implementation

[0015] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0016] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0017] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0018] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] Electronic chips are trending towards higher integration, higher power, and higher heat flux density. Excessive junction temperature in electronic chips can negatively impact chip lifespan and reliability. The thermal design of electronic chips requires consideration of heat dissipation area, limited space, and the operating environment; it is a systemic problem involving the intersection of electronics, heat transfer, materials science, and micromachining, as well as multi-physics coupling. With the diversification of integrated circuit applications, data centers, AI, and high-performance computing are placing higher demands on advanced packaging, leading to rapid development and continuous innovation in packaging technology. The electronic packaging substrate, acting as a bridge connecting the chip body and the printed circuit board (PCB), provides mechanical support, environmental protection, electrical signal interconnection, and heat dissipation for the chip.

[0021] Flip-chip packaging technology, as one of the mainstream chip packaging technologies, can improve the heat dissipation performance of chips, effectively reduce the junction temperature of chips, and thus improve the computing performance and stability of chips. The junction-to-case thermal resistance (JTR) of a flip-chip refers to the thermal resistance between the chip junction and the package shell, and is an important indicator for measuring the chip's heat dissipation performance. The package shell is generally made of copper metal material with nickel plating on the outer surface. The back of the bare chip contacts the inner surface of the package shell through a first thermal interface material, resulting in a relatively high JTR. Aircraft-borne electronic equipment mainly uses flip-chips such as FPGAs. Due to limitations such as gravity variations, temperature variations, enclosed spaces, lack of air and liquid supply, and volume and weight, the main heat dissipation path for flip-chips is through a back metal heat sink connected by a second thermal interface material, passively absorbing the heat dissipation during chip operation using the heat capacity of the metal structure. However, with the increasing integration of chips and the growing heat power and heat flux density, traditional metal heat sinks can no longer meet the chip's heat dissipation requirements. Simultaneously, because chips have multiple heat-generating junctions with uneven heat distribution and different power densities, localized overheating problems can occur.

[0022] To address the problems existing in the prior art, see [link to relevant documentation]. Figures 1 to 3 As shown, this embodiment of the invention provides a flip-chip structure, including a chip body 1, a substrate 2, a housing 3, and a phase change material. The chip body 1 is disposed on the substrate 2. The housing 3 has a first open end and a first closed end disposed opposite to each other, with the first open end disposed on the substrate 2. A connecting portion 34 extending towards the center of the housing 3 is provided on the inner wall of the housing 3. The connecting portion 34 cooperates with the chip body 1 and is sealed to the side of the chip body 1 away from the substrate 2, so that the cavity of the housing 3 forms a first cavity 31 and a second cavity 32. The chip body 1 is located in the second cavity 32, and the phase change material is accommodated in the first cavity 31 and / or the second cavity 32.

[0023] When the above technical solution is adopted, since the connecting part 34 cooperates with the chip body 1 and the connecting part 34 is sealed to the side of the chip body 1 away from the substrate 2, the cavity of the housing 3 forms a first cavity 31 and a second cavity 32. When a phase change material is disposed in the first cavity 31, the phase change material can directly contact the side of the chip body 1 away from the substrate 2 and generate heat exchange. The phase change material can directly absorb the heat of the chip body 1 and carry away the heat of the chip body 1, thereby reducing the temperature of the chip body 1. In addition, when a phase change material is disposed in the second cavity 32, the chip body 1 is located in the second cavity 32, and the phase change material can directly contact the chip body 1 and generate heat exchange. The phase change material can directly absorb the heat of the chip body 1 and carry away the heat of the chip body 1, thereby reducing the temperature of the chip body 1.

[0024] Compared to existing technologies that use efficient phase change heat sinks such as vapor chambers to dissipate heat from the chip body 1, the flip chip structure in this invention allows the phase change material to directly contact the chip body 1, enabling direct cooling of the chip body 1. This reduces junction thermal resistance, improves the temperature uniformity of the flip chip, mitigates localized overheating, increases the power limit of the flip chip, and meets the requirements for efficient heat dissipation and rapid temperature uniformity. Furthermore, phase change heat dissipation solves the problem of passive heat dissipation in flip chips operating in variable gravity enclosed environments.

[0025] In specific implementation, the substrate 2 and the housing 3 can be bonded using at least one of silicone-based sealant, polyurethane-based sealant, and polyacrylate-based sealant. The lower surface of the chip body 1 is connected to the substrate 2 via a bottom-filling and solder bump encapsulation process. The connecting part 34 can be a plate-shaped structure made of the same material as the housing 3. The plate-shaped structure and the housing 3 can be integrally formed or welded together. A notch is made in the center of the plate-shaped structure to connect with the side of the chip body 1 away from the substrate 2. The ratio of the notch area to the cross-sectional area of ​​the housing 3 can be less than or equal to 1:10.

[0026] In one possible implementation, the phase change material includes a gas-liquid phase change material 41 and a solid-liquid phase change material 42. The gas-liquid phase change material 41 has the technical advantages of high thermal conductivity, good temperature uniformity, lightweight and fast response, while the solid-liquid phase change material has high heat storage capacity and can be used to absorb the large amount of heat released by the chip body 1 during short-term operation. It is a typical passive heat dissipation technology with significant energy saving effect.

[0027] In one example, see Figure 1As shown, the gas-liquid phase change material 41 can be placed only in the first cavity 31. In this case, the liquid phase change material is in direct contact with the side of the chip body 1 away from the substrate 2, and quickly absorbs heat and vaporizes into gaseous phase change material, carrying away a large amount of heat from the chip body 1. When the gaseous phase change material comes into contact with the lower temperature area of ​​the shell 3, the gaseous phase change material will condense into liquid phase change material. The liquid flows to the side of the chip body 1 away from the substrate 2 by its own gravity, completing a heat exchange cycle. In this way, the cooling effect of the chip body 1 is achieved, the junction thermal resistance is reduced, and the flip chip power, computing power and temperature uniformity can be improved, increasing the upper limit of chip power.

[0028] Further, see Figure 1 and Figure 3 As shown, when the first cavity 31 is used to contain the gas-liquid phase change material 41, at least one liquid return column 33 is provided in the first cavity 31. One end of the liquid return column 33 is supported on the inner wall of the housing 3, and the other end is supported on the side of the chip body 1 away from the substrate 2.

[0029] The liquid return column 33 serves two purposes: mechanically, it supports the chip body 1 and the housing 3, preventing the housing 3 from denting or the chip body 1 from warping; in terms of heat transfer, it increases the heat conduction channel between the chip body 1 and the housing 3, shortens the liquid return distance, facilitates the liquefied phase change material to flow back along the liquid return column 33, allows the condensate to quickly return to the heating surface, and achieves gas-liquid two-phase flow separation, reducing the total flow pressure drop and thus improving the heat transfer performance of the phase change heat dissipation structure.

[0030] Furthermore, please refer to Figure 1 and Figure 3 When the first cavity 31 is used to contain the gas-liquid phase change material 41, a micro-nano reinforced surface structure 11 is provided on the side of the chip body 1 away from the substrate 2 to enhance the heat dissipation capacity of the chip body 1 and improve the cooling effect on the chip body 1. Specifically, the micro-nano reinforced surface structure 11 can be disposed in the central region of the side of the chip body 1 away from the substrate 2, and the ratio of the area of ​​the central region to the area of ​​the side of the chip body 1 away from the substrate 2 is less than 9:10. The micro-nano reinforced surface structure 11 includes at least one of the following: a micro-nano micropillar array structure surface, a wetting characteristic surface, a coating surface, an electrochemical deposition surface, and a femtosecond laser etched surface.

[0031] In another example, refer to Figure 2As shown, solid-liquid phase change material 42 can be filled in both the first cavity 31 and the second cavity 32, thus enabling passive heat dissipation of the flip chip under extreme conditions of a variable gravity enclosed space. When the first cavity 31 is used to accommodate the solid-liquid phase change material 42, a framework structure 5 is provided inside the first cavity 31. Similarly, when the second cavity 32 is used to accommodate the solid-liquid phase change material 42, a framework structure 5 is provided inside the second cavity 32. The framework structure 5 can be a porous material with high thermal conductivity, and the solid-liquid phase change material 42 is placed within the pores of the porous material. In specific implementations, the framework structure 5 includes at least one of foamed metal or foamed graphite. Foamed metal has advantages such as low price, easy welding, controllable porosity, and structural stability. Foamed graphite has advantages such as low density and high emissivity. Both materials can be in close contact with the inner wall of the first cavity 31 or the second cavity 32. By encapsulating and integrating foamed metal or foamed graphite and solid-liquid phase change materials within the housing 3, compared to traditional flip chips, the use of foamed materials as a framework for support can enhance the heat transfer capability of solid-liquid phase change. This is a new method for achieving passive heat dissipation of flip chips under extreme conditions of variable gravity enclosed space.

[0032] In the third example, such as Figure 3 As shown, a gas-liquid phase change material 41 can be placed in the first cavity 31, and a solid-liquid phase change material 42 can be placed in the second cavity 32. This integrates the gas-liquid phase change material 41 and the solid-liquid phase change material 42 within the flip-chip structure, achieving integrated high heat flux density cooling and high power density heat storage, thus enhancing the flip-chip structure's ability to withstand instantaneous high heat flux shocks. Simultaneously, the multi-phase coupling thermal control technology, integrating the gas-liquid phase change material 41 in the first cavity 31 and the solid-liquid phase change material 42 in the second cavity 32, leverages the high thermal conductivity of the gas-liquid phase change material 41 and the strong heat storage capacity of the solid-liquid phase change material 42 to overcome the technical bottleneck of the solid-liquid phase change material 42's low thermal conductivity, thereby improving the internal heat exchange capacity of the flip-chip structure.

[0033] In practice, the solid-liquid phase change material 42 is required to be a substance with a low boiling point, non-toxicity, chemical stability, and low susceptibility to chemical reactions with the inner wall of the casing 3 and the chip body 1. For example, the solid-liquid phase change material 42 includes at least one of n-tetradecane, n-octadecane, or gallium. Furthermore, in specific implementations, metal nanoparticles 421 can be composited within the solid-liquid phase change material 42 to further enhance the heat exchange of the solid-liquid phase change material 42 and improve the cooling effect on the chip body 1.

[0034] Similarly, the gas-liquid phase change material 41 is required to be non-toxic, chemically stable, and not prone to chemical reaction with the inner wall of the casing 3 and the chip body 1. For example, the gas-liquid phase change material 41 includes at least one of distilled water, electronic fluorinated liquid, deionized water, methanol, ethanol, or ethylene glycol.

[0035] As an option, the material of the shell 3 can be one of metal, low-temperature co-fired ceramic, high-temperature co-fired ceramic, Kovar alloy, or metal-based composite material. This enriches the material diversity of the shell 3 and makes it easier to select and set according to the actual situation.

[0036] In one possible implementation, the height of the housing 3 is 2mm to 200mm. For example, the height of the housing 3 can be 5mm, 10mm, 50mm, 100mm, 120mm, 150mm, 180mm, etc., without specific limitations. The height of the first cavity 31 is 1mm to 199mm, and the height of the second cavity 32 is 1mm to 199mm. For example, the height of the first cavity 31 can be 5mm, 20mm, 50mm, 100mm, 120mm, 150mm, 180mm, etc., and the height of the second cavity 32 can be 10mm, 30mm, 50mm, 100mm, 120mm, 150mm, 190mm, etc., without specific limitations, as long as a good cooling effect on the chip body 11 can be ensured. It should be noted that the height of the housing 3 refers to the vertical distance between the first open end and the first closed end of the housing 3. The height of the first cavity 31 refers to the vertical distance between the first closed end and the connecting part 34, and the height of the second cavity 32 refers to the vertical distance between the connecting part 34 and the substrate 2.

[0037] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0038] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flip-chip structure, characterized in that, include: Chip body; A substrate, wherein the chip body is disposed on the substrate; The housing has a first open end and a first closed end disposed opposite to each other, the first open end being disposed on the substrate; the inner wall of the housing is provided with a connecting portion extending toward the center of the housing, the connecting portion cooperating with the chip body, the connecting portion being sealed to the side of the chip body away from the substrate, for forming a first cavity and a second cavity in the cavity of the housing, the chip body being located in the second cavity; A phase change material is contained in the first cavity and the second cavity, and the phase change material located in the first cavity and the second cavity is in direct contact with the chip body; The phase change materials include gas-liquid phase change materials and solid-liquid phase change materials; When the first cavity contains the gas-liquid phase change material, at least one liquid return column is provided in the first cavity. One end of the liquid return column is supported on the inner wall of the shell, and the other end is supported on the side of the chip body away from the substrate. A micro-nano reinforced surface structure is provided on the side of the chip body away from the substrate. When the first cavity is used to contain the solid-liquid phase change material, a skeleton structure is provided inside the first cavity; when the second cavity is used to contain the solid-liquid phase change material, the skeleton structure is provided inside the second cavity.

2. The flip-chip structure according to claim 1, characterized in that, The skeleton structure includes at least one of foamed metal or foamed graphite.

3. The flip-chip structure according to claim 1, characterized in that, The solid-liquid phase change material includes at least one of n-tetradecane, n-octadecane, or gallium.

4. The flip-chip structure according to claim 1, characterized in that, The gas-liquid phase change material includes at least one of distilled water, electronic fluorinated liquid, deionized water, methanol, ethanol, or ethylene glycol.

5. The flip-chip structure according to claim 1, characterized in that, The shell is made of one of the following materials: metal, low-temperature co-fired ceramic, high-temperature co-fired ceramic, Kovar alloy, or metal-based composite material.

6. The flip-chip structure according to claim 1, characterized in that, The height of the shell is 2 mm to 200 mm, the height of the first cavity is 1 mm to 199 mm, and the height of the second cavity is 1 mm to 199 mm.

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