Method for manufacturing a heat dissipation lid

Abstract

The embodiment of the present application provides a preparation method of a heat dissipation cover, and relates to the technical field of semiconductor packaging. The method comprises the following steps: providing a substrate, the substrate has a bonding area, the bonding area is located on at least part of the surface of one side of the substrate along the thickness direction of the substrate; forming a barrier layer on the bonding area, the side of the barrier layer away from the substrate is provided with a passivation layer; removing the passivation layer; forming a protective layer on the side of the barrier layer away from the substrate; and forming a heat conduction layer on the side of the protective layer away from the barrier layer. The preparation method of the heat dissipation cover forms a protective layer on one side of the barrier layer, inhibits the formation of the passivation layer, maintains the activation state of the surface of the barrier layer, and prevents the decomposition of the protective layer when the heat conduction layer is formed, so that the heat conduction layer is directly in contact with the barrier layer, thereby preventing the increase of thermal resistance caused by the metal compound formed by the gold layer, and preventing the decrease of the reliability of the bonding interface caused by the residues retained on the bonding interface when the flux is used.

Description

Technical Field

[0001] This application relates to the field of semiconductor packaging technology, and in particular to a method for preparing a heat sink. Background Technology

[0002] Processors and accelerators used in data centers and high-performance computing generate a large amount of heat during operation. If this heat cannot be dissipated in time, the chip temperature will rise sharply, leading to performance degradation. Typically, an integrated heat spreader (IHS) is used to bond the semiconductor chip to the IHS using a solder-based thermal interface material (TIM). The high thermal conductivity and mechanical compliance of indium-based or tin-based solders enable efficient heat conduction. A layer of nickel is electroplated on the surface of the IHS as a diffusion barrier layer and a bonding interface.

[0003] In related technologies, during the fabrication of the heat sink cover, a gold layer is formed on the nickel surface to improve the wettability of the solder and inhibit nickel oxidation, or a strong flux is used during the bonding process to improve the wettability of the solder.

[0004] However, the gold layer mentioned above is prone to react with indium or tin to form metal compounds, which leads to an increase in thermal resistance; when using flux, residues are easily left at the bonding interface, resulting in a decrease in the reliability of the bonding interface. Summary of the Invention

[0005] This application provides a method for preparing a heat sink to reduce thermal resistance and improve the reliability of the bonding interface.

[0006] This application provides a method for preparing a heat dissipation cap, including:

[0007] A substrate is provided, the substrate having a bonding region located on at least a portion of the surface of the substrate on one side along the thickness direction of the substrate.

[0008] A barrier layer is formed in the bonding region, and a passivation layer is formed on the side of the barrier layer away from the substrate.

[0009] Remove the passivation layer.

[0010] A protective layer is formed on the side of the barrier layer that faces away from the substrate.

[0011] A heat-conducting layer is formed on the side of the protective layer away from the barrier layer. During the formation of the heat-conducting layer, the protective layer undergoes thermal decomposition.

[0012] In the above-mentioned method for preparing the heat sink, it is possible to form a heat-conducting layer, specifically including:

[0013] The thermally conductive layer is bonded to the side of the protective layer away from the barrier layer by hot-press reflow soldering, and the barrier layer and the thermally conductive layer are metallurgically bonded.

[0014] In the above-described method for preparing a heat sink, it is possible to include, after removing the passivation layer and before forming the protective layer, the following steps:

[0015] Microporous or microprotrusion structures are formed on the side of the barrier layer away from the substrate using nanoimprinting or laser etching processes.

[0016] After the thermally conductive layer is formed, the thermally conductive layer and the barrier layer are metallurgically bonded through a microporous structure or a micro-protrusion structure.

[0017] In the above-described method for preparing a heat sink, it is possible to include, after forming the protective layer and before bonding the thermally conductive layer to the barrier layer, the following steps:

[0018] The protective layer is treated with infrared pulses or lasers to pre-decompose it.

[0019] In the above-mentioned method for preparing the heat dissipation cover, it is possible to achieve that the protective layer includes at least two organic compound layers, and the molecular weight of the at least two organic compound layers gradually increases along the direction from the barrier layer to the heat-conducting layer.

[0020] In the above-mentioned method for preparing the heat dissipation cover, it is possible to achieve that the protective layer includes at least two organic compound layers, and the thickness of the at least two organic compound layers gradually increases along the direction from the barrier layer to the heat-conducting layer.

[0021] In the above-mentioned method for preparing the heat dissipation cover, it is possible to use infrared thermal imaging or mass spectrometry to detect the decomposition state of the protective layer during the formation of the heat-conducting layer.

[0022] In the above-mentioned method for preparing the heat dissipation cover, it is possible to form a protective layer, including forming a protective layer in an inert gas.

[0023] In the above-mentioned method for preparing the heat dissipation cover, it is possible to achieve thermal decomposition of the protective layer when the bonding temperature of the heat-conducting layer is greater than or equal to the melting point of the protective layer and less than or equal to the melting point of the heat-conducting layer.

[0024] In the above-described method for preparing the heat sink, the removal of the passivation layer can be achieved by:

[0025] The passivation layer is removed by chemical reduction treatment, acid activation treatment, plasma treatment or temperature-controlled heat treatment.

[0026] In the above-mentioned method for preparing the heat dissipation cover, it is possible to remove the passivation layer in an inert gas.

[0027] In the above-mentioned method for preparing the heat dissipation cover, it is possible to make at least one of indium-based alloys and tin-based alloys as the heat-conducting layer.

[0028] In the above-mentioned method for preparing the heat sink, it is possible to use copper or a copper alloy as the substrate.

[0029] The method for preparing a heat sink provided in this application involves forming a barrier layer in the bonding region of the substrate and forming a protective layer on the side of the barrier layer away from the substrate after removing the passivation layer. The protective layer can be adsorbed on the surface of the barrier layer and inhibit the formation of the passivation layer to maintain the active state of the barrier layer surface. This prevents the increase in thermal resistance caused by the metal compound formed by the gold layer and prevents the reliability of the bonding interface from being reduced due to the residues left at the bonding interface when using flux.

[0030] Furthermore, during the formation of the heat-conducting layer, the protective layer undergoes thermal decomposition, resulting in a direct metallurgical bond between the heat-conducting layer and the barrier layer. This improves the reliability of the bonding interface between the heat-conducting layer and the barrier layer, further reduces heat buildup, and simplifies the structure of the heat sink. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] Figure 1 A schematic diagram of the manufacturing process of the heat sink provided in the embodiments of this application;

[0033] Figure 2 A schematic diagram of the manufacturing method of the heat sink provided in the embodiments of this application. Figure 1 ;

[0034] Figure 3 A schematic diagram of the manufacturing method of the heat sink provided in the embodiments of this application. Figure 2 ;

[0035] Figure 4 A schematic diagram of the manufacturing method of the heat sink provided in the embodiments of this application. Figure 3 ;

[0036] Figure 5 A schematic diagram of the preparation method of the heat sink provided in the embodiments of this application. Figure 4 .

[0037] Explanation of reference numerals in the attached figures:

[0038] 10. Substrate; 20. Barrier layer; 21. Passivation layer; 30. Protective layer; 40. Thermal conductive layer.

[0039] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0040] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0041] Processors and accelerators used in data centers and high-performance computing generate a large amount of heat during operation. If this heat cannot be dissipated in time, the chip temperature will rise sharply, leading to performance degradation. Typically, an integrated heat spreader (IHS) is used to bond the semiconductor chip to the IHS using a solder-based thermal interface material (TIM). The high thermal conductivity and mechanical compliance of indium-based or tin-based solders enable efficient heat conduction. A layer of nickel is electroplated on the surface of the IHS as a diffusion barrier layer and a bonding interface.

[0042] In related technologies, during the fabrication of heat sinks, a gold layer is formed on the nickel surface to improve solder wettability and inhibit nickel oxidation. However, the gold layer is prone to react with indium or tin to form metal compounds, which leads to an increase in thermal resistance. Alternatively, a strong flux is used during the bonding process to improve solder wettability, but residues are easily retained at the bonding interface, which reduces the reliability of the bonding interface.

[0043] This application provides a method for preparing a heat sink cover. A barrier layer is formed in the bonding area of ​​the substrate, and a protective layer is formed on the side of the barrier layer away from the substrate after removing the passivation layer. The protective layer can be adsorbed on the surface of the barrier layer and inhibit the formation of the passivation layer to maintain the active state of the barrier layer surface. This prevents the increase in thermal resistance caused by the metal compound formed by the gold layer and prevents the reliability of the bonding interface from being reduced due to the residue left at the bonding interface when using flux.

[0044] Furthermore, during the formation of the heat-conducting layer, the protective layer undergoes thermal decomposition, resulting in a direct metallurgical bond between the heat-conducting layer and the barrier layer. This improves the reliability of the bonding interface between the heat-conducting layer and the barrier layer, further reduces heat buildup, and simplifies the structure of the heat sink.

[0045] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0046] This application provides a method for manufacturing a heat sink cover. The heat sink cover is a pre-installed heat dissipation structure within a high-performance semiconductor package and is integrally fixed to the package substrate. It directly covers the bare chip, effectively compensating for insufficient thermal conductivity of the chip itself, eliminating localized high-temperature hotspots, and making the chip surface temperature more uniform. Simultaneously, the heat sink cover provides physical isolation and protection for the chip, shielding it from squeezing, scratching, and impacts that may occur during assembly, testing, and installation, protecting critical structures such as the silicon wafer, bonding wires, and interposers. Furthermore, the heat sink cover enhances the rigidity of the overall package structure, suppressing warping deformation between the package structure and the chip under high-temperature reflow soldering and long-term thermal cycling conditions, reducing solder joint breakage and gold wire detachment, and improving the reliability and lifespan of the semiconductor package.

[0047] Figure 1 This is a schematic flowchart of the method for preparing the heat sink provided in the embodiments of this application, referring to... Figure 1 As shown, the preparation method includes:

[0048] S100: Provides a substrate having a bonding region located on at least a portion of the surface of the substrate along its thickness direction. The substrate 10 serves as the main support structure for the heat sink, enabling rapid heat dissipation from the chip, eliminating localized hot spots, improving chip temperature uniformity, providing mechanical protection for the chip, enhancing the overall rigidity of the package cover, suppressing warping deformation, and forming a sealed environment to protect the internal structure.

[0049] As one feasible implementation, the substrate 10 is copper or a copper alloy. Copper-based materials have high thermal conductivity and good processability, which can meet the requirements of heat dissipation and structural strength of the heat sink, making them suitable as the main body supporting the heat sink, allowing heat to be rapidly diffused to the external heat dissipation structure via the substrate 10. For example, the substrate 10 can be processed from pure copper sheet, oxygen-free copper sheet, or copper alloy sheet.

[0050] The bonding region is located on at least a portion of the surface of the substrate 10 on one side of the thickness direction. It is understood that the bonding region is a connection region facing the chip side. The subsequent barrier layer 20 and thermal conductive layer 40 are formed in this region in order to effectively transfer heat along the thickness direction and reduce the interface thermal resistance.

[0051] Reference Figure 2As shown, after the bonding region is defined on the surface of the substrate 10, the method further includes: S200: forming a barrier layer in the bonding region, wherein the side of the barrier layer away from the substrate has a passivation layer.

[0052] The barrier layer 20 is used to suppress the outward diffusion of the metal from the substrate 10, prevent the formation of brittle intermetallic compounds, and also provide a controllable surface chemical environment for subsequent interface layers. Exemplarily, the barrier layer 20 may be a nickel base layer, a nickel-phosphorus layer, a cobalt layer, a titanium layer, or other metal layers with diffusion-blocking capabilities, and may be formed by electroplating, electroless plating, or physical deposition to obtain a continuous and dense coverage on the surface of the substrate 10.

[0053] In this process, the surface of the barrier layer 20 away from the substrate 10 undergoes an oxidation reaction to form a passivation layer 21. For example, when the barrier layer 20 is a nickel base layer or a nickel-phosphorus layer, the passivation layer 21 can be nickel monoxide, a light oxidation product at room temperature, which is a gray-black thin film; it can also be nickel trioxide, a long-term oxidation product under high temperature and high humidity, which is a dark black powdery oxide layer; or it can be basic nickel carbonate, which is generated when the air contains sulfides and carbon dioxide, and appears as a black-brown corrosion spot.

[0054] Reference Figure 3 As shown, after the passivation layer 21 is formed on the surface of the barrier layer 20, the process further includes: S300: removing the passivation layer.

[0055] In this embodiment, removing the passivation layer 21 can restore the chemical activity of the surface of the barrier layer 20, enabling the subsequently formed protective layer 30 to establish a stable metallurgical bond with the barrier layer 20, while avoiding the influence of the passivation layer 21 residue on the wetting and connection of the heat-conducting layer 40.

[0056] In some embodiments, by controlling the removal intensity to only remove the surface passivation layer 21, roughening or localized corrosion of the barrier layer 20 can be avoided, thereby maintaining the diffusion blocking function and interface smoothness of the barrier layer 20. The key to this removal process is to maintain the continuity of the barrier layer 20 while peeling off the deactivated layer, so that the subsequent protective layer 30 can uniformly cover the activated surface, thereby improving the forming consistency of the thermally conductive layer 40 and significantly reducing poor soldering, voids, and increased interface thermal resistance caused by oxidation residues.

[0057] Reference Figure 4 As shown, after removing the passivation layer 21, the process further includes: S400: forming a protective layer on the side of the barrier layer away from the substrate.

[0058] The protective layer 30 is used to temporarily protect the barrier layer 20 after the passivation layer 21 is removed, preventing the barrier layer 20 from re-oxidizing or becoming surface-contaminated during subsequent handling, storage, or heating, thereby maintaining the barrier layer 20 in an active state after the passivation layer 21 is removed. It should be noted that the protective layer 30 is applied and formed immediately after the passivation layer 21 is removed.

[0059] For example, the protective layer 30 can be an organic solderability preservative (OSP) capable of temporarily maintaining the activity of the metal surface, such as a thermally decomposable polymer, a low-residue resin, or an organic thin film material containing active functional groups. The layers are formed by spin coating, spraying, printing, vapor deposition, or lamination to create a multi-layered protective layer 30, thereby controlling the oxidation state of the barrier layer 20. This protective layer 30 can employ a continuous coverage structure ranging from nanometer to submicrometer scale, with its thickness controlled to effectively isolate external oxygen and moisture without creating an excessively thick thermal barrier.

[0060] Reference Figure 5 As shown, after the protective layer 30 is formed, the process further includes: S500: forming a heat-conducting layer on the side of the protective layer away from the barrier layer, during which the protective layer undergoes thermal decomposition.

[0061] The thermally conductive layer 40 is a functional layer for heat dissipation connection, which is in direct contact with external heat sources or heat dissipation components to establish a low thermal resistance heat transfer path.

[0062] As one feasible implementation, the thermally conductive layer 40 is at least one of an indium-based alloy and a tin-based alloy.

[0063] Indium-based alloys have a low melting point and good flexibility, enabling them to form dense contacts under low thermal stress; tin-based alloys are easy to reflow molded and have good process compatibility. Both indium-based and tin-based alloys can achieve a stable metallurgical bond with the barrier layer 20 under hot-press reflow soldering conditions, thereby reducing interfacial thermal resistance and improving thermal diffusion efficiency after encapsulation.

[0064] For example, the thermally conductive layer 40 can be formed by printing, pre-forming placement, plating, or reflow soldering, depending on the configuration of the target package structure and the thermal interface material.

[0065] In this embodiment, the barrier layer 20 is first used to isolate the diffusion of the substrate 10, then the passivation layer 21 is removed to restore the interface activity, then the protective layer 30 is used to maintain the surface state, and finally the thermally conductive layer 40 is formed to establish a heat conduction path. By causing the protective layer 30 to undergo thermal decomposition during the formation of the thermally conductive layer 40, the thermally conductive layer 40 is made to directly contact the barrier layer 20. This allows the heat sink to ensure low thermal resistance heat transfer while taking into account interface stability and reflow process adaptability. It can also effectively prevent the reduction in the reliability of interface bonding caused by gold layer embrittlement, flux residue or passivation deactivation in related technologies, thereby meeting the requirements of high power density semiconductor packaging.

[0066] As one feasible implementation, forming a thermally conductive layer 40 specifically includes: bonding the thermally conductive layer 40 to the side of the protective layer 30 away from the barrier layer 20 by a hot-press reflow soldering process, wherein the barrier layer 20 and the thermally conductive layer 40 are metallurgically bonded.

[0067] Thermopressive reflow soldering is a composite soldering process that simultaneously applies mechanical pressure, heats up, and applies a vacuum or protective atmosphere. It is used for metallurgical bonding between bare dies and integrated heat sinks within semiconductor packages. Thermopressive reflow soldering achieves a stable thermally conductive connection with low thermal resistance between the bare die and the heat sink. Simultaneously, the pressure filling and vacuum or protective atmosphere effectively eliminate interfacial air, reduce the thermal interface void ratio, and ensure the reliability of the bonding interface.

[0068] In some embodiments, the thermally conductive layer 40 is attached to the side of the protective layer 30 facing away from the barrier layer 20, followed by a low-temperature, small-amplitude reflow process to melt the thermally conductive layer 40 on one side and pre-bond it with the barrier layer 20. During this process, as the temperature rises, the protective layer 30 decomposes or volatilizes before or during the melting of the thermally conductive layer 40, eliminating the barrier effect of the protective layer 30. This allows the molten thermally conductive layer 40 to directly contact the surface of the barrier layer 20 and undergo atomic diffusion, forming a metallurgical bond. This results in a low-voidity, high-continuity metal interface, effectively improving the long-term reliability of the bonded interface and further reducing thermal expansion, while simplifying the structure of the heat sink. After the heat sink pre-processing is completed, the heat sink is aligned and snapped onto the bare chip, and a reflow process is performed again to finally achieve metallurgical bonding between the heat sink and the back of the bare chip.

[0069] In some embodiments, the protective layer 30 is selectively applied to a predetermined area (bonding area) where the barrier layer 20 and the substrate 10 are in contact with the protective layer 30, and the protective layer 30 is not applied to other areas.

[0070] As one possible implementation, after removing the passivation layer 21 and before forming the protective layer 30, the method further includes: forming a microporous structure or a microprotrusion structure on the side of the barrier layer 20 away from the substrate 10 by means of nanoimprinting or laser etching.

[0071] After the thermal conductive layer 40 is formed, the thermal conductive layer 40 and the barrier layer 20 are metallurgically bonded through a microporous structure or a microprotrusion structure.

[0072] Nanoimprinting is a micro-nano pattern transfer process. A hard imprinting template with reversed micropore and micro-protrusion morphology is pre-prepared. The template is aligned with the surface of the barrier layer 20, and pressure and moderate heating are applied to cause micro-deformation of the surface of the barrier layer 20. The concave and convex patterns on the template are copied to the surface of the barrier layer 20 opposite to the substrate 10. After demolding, a regularly arranged microporous structure or micro-protrusion structure is directly obtained on the barrier layer 20. This process relies on molds to batch replicate patterns, resulting in high processing efficiency and good microstructure dimensional consistency.

[0073] Laser etching employs a high-precision focused high-energy laser beam to scan the surface of the barrier layer 20 along a preset trajectory. The laser energy locally and instantaneously melts and vaporizes the barrier layer 20, removing material from specific areas of the barrier layer 20 and directly creating microporous structures on its surface. Alternatively, by controlling the laser energy and scanning interval, localized areas of the barrier layer 20 can be retained to form an array of micro-protrusions. This process requires no molds, offers controllable pattern precision, and allows for rapid adjustment of the arrangement.

[0074] By using nanoimprinting or laser etching, regularly distributed micropores or microprotrusions are formed on the surface of the barrier layer 20 to provide more effective contact sites, which helps to increase the effective contact area and thus improve the bonding strength. Simultaneously, during the bonding process of the thermally conductive layer 40, the layer melts upon heating, forming a liquid metal. Under capillary force and pressure, this liquid metal enters the micropores or coats the surface of the microprotrusions, expelling interfacial air and achieving void-free filling, thereby reducing interfacial voids. Furthermore, the microporous or microprotrusion structure can also form localized stress concentration and molten filling channels to enhance mechanical interlocking. After the thermally conductive layer 40 solidifies, it forms an intermetallic bonding interface, thereby achieving metallurgical bonding between the thermally conductive layer 40 and the barrier layer 20 and improving the reliability of the bonding interface.

[0075] Furthermore, by directly forming microporous or microprotrusion structures through nanoimprinting or laser etching, the structural size, spacing, and depth can be stably controlled, which helps to ensure the consistency of interface morphology and reduce uneven wetting and void residue caused by insufficient surface flatness, thereby further reducing interface thermal resistance and improving bonding strength and long-term reliability.

[0076] For example, the microporous structure can be an array of pits, blind holes or through holes, and the microprotrusion structure can be micron- or submicron-sized protrusions, ridges or island-shaped protrusions.

[0077] As one feasible implementation, after the protective layer 30 is formed and before the thermally conductive layer 40 is bonded to the barrier layer 20, the protective layer 30 is further treated with an infrared pulse or laser to pre-decompose the protective layer 30.

[0078] Infrared pulse or laser treatment involves targeted energy input to the protective layer 30, causing localized thermal decomposition or structural relaxation before the thermally conductive layer 40 bonds, thereby weakening its barrier effect on interfacial bonding. For example, the protective layer 30 can be an organic or composite protective layer with a certain degree of thermal decomposition sensitivity, and its surface can be pre-irradiated by pulsed infrared irradiation or short-pulse laser scanning. The input energy density is controlled within a range sufficient to induce molecular chain breakage or volatile component escape from the protective layer 30 without damaging the underlying barrier layer 20. By controlling the pulse width, repetition frequency, and scanning speed, the protective layer 30 undergoes only pre-decomposition rather than complete removal, forming more thermal interaction channels and low binding energy regions within it.

[0079] By pre-decomposing the protective layer 30, the thermal decomposition resistance of the protective layer 30 during the subsequent bonding of the thermally conductive layer 40 can be reduced. This makes it easier for heat to be transferred to the interface during bonding and promotes the rapid release of gases or residual organic components from the protective layer 30, reducing the formation of interfacial residues and local voids, thereby improving bonding consistency. Simultaneously, the pre-decomposition process completes some energy release before the thermally conductive layer 40 is bonded, making the interfacial reaction more controllable during subsequent hot-pressing reflow, thus improving the connection reliability and heat dissipation stability of the heat sink.

[0080] As one feasible implementation, the protective layer 30 includes at least two organic compound layers, and the molecular weight of the at least two organic compound layers gradually increases along the direction from the barrier layer 20 to the thermally conductive layer 40.

[0081] Along the direction from the barrier layer 20 to the thermally conductive layer 40, as the molecular weight of the organic compound layer gradually increases, the layer near the passivation layer 21 can use a lower molecular weight material to reduce the coating viscosity and enhance the spreading and covering ability of the barrier layer 20 surface, so that it can more fully fill the micro-undulations of the interface; the layer near the thermally conductive layer 40 can use a higher molecular weight material to improve the heat resistance stability and film integrity, so that it can still maintain a continuous barrier in the early stage of bonding of the thermally conductive layer 40.

[0082] By setting a molecular weight gradient, the protective layer 30 can be softened, decomposed, or volatilized first when heated, releasing the interface layer by layer, thereby allowing the thermally conductive layer 40 to contact the barrier layer 20 more smoothly, achieving a synergistic effect of controlled decomposition and stable bonding.

[0083] As one feasible implementation, the protective layer 30 includes at least two organic compound layers, and the thickness of the at least two organic compound layers gradually increases along the direction from the barrier layer 20 to the heat-conducting layer 40.

[0084] Along the direction from the barrier layer 20 to the thermally conductive layer 40, as the thickness of the organic compound layer gradually increases, a thinner film layer can be formed in the layer near the passivation layer 21 to reduce the impact of residues on interfacial activity; a thicker film layer can be formed in the layer near the thermally conductive layer 40 to provide stronger thermal buffering and temporary protection.

[0085] By varying the thickness gradient, heat can be preferentially responded to by the thinner layer during the reflow process, and then the thicker layer can provide delayed protection. This allows the protective layer 30 to ensure coverage integrity while achieving delamination and deactivation during the bonding of the thermally conductive layer 40, preventing voids, localized dewetting, and interface contamination, thereby improving bonding uniformity and thermal conductivity stability. It should be noted that in this embodiment, at least two organic compound layers are made of different compounds.

[0086] As one feasible implementation, the passivation layer 21 is removed in an inert gas. By removing the passivation layer 21 in an inert gas, secondary oxidation of the passivation layer 21 after removal can be avoided, thereby further improving the film continuity and interfacial bonding reliability of the protective layer 30.

[0087] For example, the inert gas can be nitrogen, argon, or a mixture thereof, to provide a low-oxygen, low-moisture formation environment.

[0088] As one feasible implementation, during the formation of the thermally conductive layer 40, infrared thermal imaging or mass spectrometry is used to detect the decomposition state of the protective layer 30.

[0089] When the protective layer 30 decomposes under heat, the film absorbs heat locally, causing uneven interface temperature. Once the film is completely decomposed, the endothermic effect disappears, the interface temperature stabilizes, and the temperature field becomes more uniform. Therefore, infrared thermal imaging is used to collect the infrared radiation signal of the protective layer 30, converting it into a visualized temperature distribution map and real-time temperature data to determine the overall decomposition state of the protective layer. Mass spectrometry, on the other hand, determines the decomposition state of the protective layer by observing changes in the concentration of small organic molecules within it.

[0090] By detecting the decomposition state of the protective layer 30 and dynamically adjusting the heating temperature and time during the bonding of the heat-conducting layer 40, it is ensured that the protective layer 30 is completely decomposed before the heat-conducting layer 40 melts, avoiding residues from interfacial bonding, thereby significantly improving the stability of the bonding process and reducing interface defects caused by incomplete decomposition.

[0091] As one possible implementation, forming the protective layer 30 includes forming the protective layer 30 in an inert gas.

[0092] By forming a protective layer 30 in an inert gas, the protective layer 30 is prevented from direct contact with oxygen and water vapor in the air during deposition, coating or assembly. This prevents secondary oxidation of the barrier layer 20 after the passivation layer 21 is removed, which would lead to wetting deterioration, poor bonding and increased interfacial thermal resistance, thereby improving the consistency of the heat sink fabrication process and the final thermal conductivity.

[0093] Meanwhile, in a low-oxygen environment, the organic or decomposable components in the protective layer 30 are less prone to uncontrolled oxidation during the formation stage, thus maintaining structural integrity, chemical stability, interface protection capabilities, and subsequent thermal response characteristics.

[0094] It should be noted that the inert gas used to form the protective layer 30 can be the same as the inert gas used to remove the passivation layer 21.

[0095] As one feasible implementation, when the bonding temperature of the thermally conductive layer 40 is greater than or equal to the melting point of the protective layer 30, and less than or equal to the melting point of the thermally conductive layer 40, the protective layer 30 undergoes thermal decomposition.

[0096] The bonding temperature of the thermally conductive layer 40 refers to the temperature range actually reached and maintained at the interface during thermoforming reflow bonding. This temperature is used to ensure that the thermally conductive layer 40 has sufficient fluidity and wettability to form a stable bond with the upper structure and the lower bare die. The melting point of the protective layer 30 refers to the characteristic temperature at which the protective layer 30 transitions from a solid state to a molten state.

[0097] During the bonding of the thermally conductive layer 40, the bonding temperature is controlled within a range greater than or equal to the melting point of the protective layer 30 but not higher than the melting point of the thermally conductive layer 40. This ensures that the protective layer 30 melts or decomposes completely before the thermally conductive layer 40, and loses its coverage of the barrier layer 20 surface within a short time. In this way, the thermally conductive layer 40 can directly contact the surface of the barrier layer 20 in the reflow state, and form a metallurgical bonding interface under the combined effects of heating, pressing, and wetting, thereby reducing interfacial thermal resistance and improving the reliability of the bonding interface. Since the bonding temperature does not exceed the melting point of the thermally conductive layer 40, it can still maintain the necessary morphological stability, avoiding excessive collapse, loss, or bridging defects, thus balancing interfacial activity and structural integrity.

[0098] As one feasible implementation, removing the passivation layer 21 includes: using chemical reduction treatment, acid activation treatment, plasma treatment or temperature-controlled heat treatment to remove the passivation layer 21.

[0099] Among them, chemical reduction treatment uses a reducing medium to convert the oxidized components in the passivation layer 21 into a low-valence state or a metallic state, thereby restoring the surface activity of the barrier layer 20; acid activation treatment can be used to dissolve, complex, or peel the passivation layer 21 with acid to remove the unstable surface layer and expose the clean barrier layer 20; plasma treatment refers to removing the passivation layer 21 and its attached contaminants through active particle bombardment, bond breaking, and surface cleaning; temperature-controlled heat treatment can be understood as heat treatment carried out in a reducing or inert atmosphere, specifically to promote the decomposition, volatilization, or transformation of the passivation layer 21 under controlled temperature conditions to reduce high-temperature deactivation and damage to the substrate 10.

[0100] When removing the passivation layer 21, the appropriate removal method can be selected according to the composition and thickness of the passivation layer 21 and the material of the barrier layer 20. For example, when the passivation layer 21 is mainly a metal oxide, chemical reduction treatment can be performed using an atmosphere or solution containing reducing components to restore the metal surface under relatively mild conditions; when the passivation layer 21 contains a lot of adsorbed contaminants or soluble oxide layers, acid activation treatment can be used to quickly expose the fresh surface; when both cleanliness and non-contact properties need to be considered, plasma treatment can be used to achieve surface cleaning and activation using active particles; when the passivation layer 21 is thin and wet residue needs to be avoided, temperature-controlled heat treatment can be used to cause the passivation layer 21 to undergo controlled decomposition within a set temperature range.

[0101] In this embodiment, the passivation layer 21 can be removed by at least one of the above methods without damaging the barrier layer 20, which can restore the surface of the barrier layer 20 to a clean state suitable for subsequent bonding, making it easier to form a stable metallurgical bonding interface when the subsequent heat-conducting layer 40 is bonded, thereby improving the thermal conductivity and long-term reliability of the heat sink.

[0102] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0103] It should be noted that the embodiments mentioned in the specification, such as "an embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," etc., may include specific features, structures, or characteristics, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0104] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing a heat dissipation cap, characterized in that, include: A substrate (10) is provided, the substrate (10) having a bonding region located on at least a portion of the surface of the substrate (10) on one side along the thickness direction of the substrate (10); A barrier layer (20) is formed in the bonding region, and the barrier layer (20) has a passivation layer (21) on the side away from the substrate (10). Remove the passivation layer (21); A protective layer (30) is formed on the side of the barrier layer (20) away from the substrate (10). A heat-conducting layer (40) is formed on the side of the protective layer (30) away from the barrier layer (20). During the formation of the heat-conducting layer (40), the protective layer (30) undergoes thermal decomposition.

2. The method for preparing the heat dissipation cap according to claim 1, characterized in that, The formation of the thermally conductive layer (40) specifically includes: The thermally conductive layer (40) is bonded to the protective layer (30) on the side away from the barrier layer (20) by hot-press reflow soldering process, and the barrier layer (20) and the thermally conductive layer (40) are metallurgically bonded.

3. The method for preparing the heat dissipation cap according to claim 1, characterized in that, After removing the passivation layer (21) and before forming the protective layer (30), the process further includes: A microporous structure or microprotrusion structure is formed on the side of the barrier layer (20) facing away from the substrate (10) by nanoimprinting or laser etching. After the thermal conductive layer (40) is formed, the thermal conductive layer (40) and the barrier layer (20) are metallurgically bonded through the microporous structure or the microprotrusion structure.

4. The method for preparing the heat dissipation cap according to claim 1, characterized in that, After the protective layer (30) is formed, and before the thermally conductive layer (40) is bonded to the barrier layer (20), the method further includes: The protective layer (30) is treated with infrared pulses or lasers to pre-decompose the protective layer (30).

5. The method for preparing the heat dissipation cap according to any one of claims 1-4, characterized in that, The protective layer (30) includes at least two organic compound layers, and the molecular weight of the at least two organic compound layers gradually increases along the direction from the barrier layer (20) to the heat-conducting layer (40). And / or, the protective layer (30) includes at least two organic compound layers, the thickness of which gradually increases along the direction from the barrier layer (20) to the thermally conductive layer (40).

6. The method for preparing the heat dissipation cap according to claim 1, characterized in that, During the formation of the thermally conductive layer (40), infrared thermal imaging or mass spectrometry is used to detect the decomposition state of the protective layer (30).

7. The method for preparing the heat dissipation cap according to claim 1, characterized in that, Forming the protective layer (30) includes: The protective layer (30) is formed in an inert gas.

8. The method for preparing the heat dissipation cap according to claim 2, characterized in that, When the bonding temperature of the thermally conductive layer (40) is greater than or equal to the melting point of the protective layer (30) and less than or equal to the melting point of the thermally conductive layer (40), the protective layer (30) undergoes thermal decomposition.

9. The method for preparing the heat dissipation cap according to claim 1, characterized in that, Removing the passivation layer (21) includes: The passivation layer (21) is removed by chemical reduction treatment, acid activation treatment, plasma treatment or temperature-controlled heat treatment; And / or, the passivation layer (21) is removed in an inert gas.

10. The method for preparing the heat dissipation cap according to any one of claims 1-4, characterized in that, The heat-conducting layer (40) is at least one of indium-based alloy and tin-based alloy; And / or, the substrate (10) is copper or a copper alloy.

Images