Chip packaging method based on metal thermal interface material

Abstract

The invention provides a chip packaging method based on a metal thermal interface material. The chip packaging method comprises the steps that FCBGA packaging is carried out; a layer of hydrosol is attached to the upper surface of the chip; performing plastic packaging on the device to enable the plastic packaging material to form a box dam; removing hydrosol above the chip by using a special solvent, and drying; soldering flux is sprayed; mounting a metal thermal interface material on the upper surface of the chip; mounting a heat dissipation cover; and high-temperature backflow of the metal thermal interface material. According to the method, the metal thermal interface material is effectively prevented from overflowing in the high-temperature backflow process, the coverage rate of the metal thermal interface material is increased, the low void ratio is achieved, and the reliability of a chip and packaging is improved; the hydrosol is used for replacing the metal thermal interface material and the soldering flux in the plastic packaging process, soldering flux volatilization and metal thermal interface material oxidation caused by high temperature in the plastic packaging process can be effectively reduced, damage and pollution of a plastic packaging mold to the metal thermal interface material are avoided, and increase of the void ratio and reduction of the coverage rate in the subsequent high-temperature backflow process are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing and microelectronic packaging, and in particular to a chip packaging method based on metal thermal interface materials. Background Art

[0002] At present, the thermal interface materials (TIM) widely used in chip packaging mainly include silicone grease, silicone, thermal conductive adhesive, etc., but there are defects such as low thermal conductivity (≤6W / m·k) and high interface thermal resistance, resulting in low thermal conductivity and high interface void ratio between the heat dissipation material, the heat sink and the chip. When used in high-computing power and high-power chips, the heat of the chip cannot be effectively dissipated, the computing power is limited and the packaging reliability problem is prominent. Metal-based thermal interface materials (Metal-TIM) have high thermal conductivity characteristics (the thermal conductivity of indium is 86W / m·K) and low interface thermal resistance, which can significantly reduce the temperature difference and thermal resistance of the package junction and shell, and have important application value in high-performance packages such as CPUs and GPUs.

[0003] In the process of using high-temperature reflow process to complete the metal thermal interface material packaging, there is a serious metal overflow problem, which leads to an increase in the TIM interface porosity, a decrease in coverage, and worsening thermal resistance. In addition, the overflowed metal will cause the device to short-circuit and cause the electrical function of the package to fail. Therefore, controlling overflow has become an important technical problem that restricts the application of metal thermal interface materials.

[0004] To address this problem, the current process solution is to apply dam glue around the device to prevent the metal material from overflowing, but the dam glue has poor high temperature resistance and cannot completely prevent the metal material from overflowing. The prior art has a solution of setting an organic carbonizable substrate on the upper surface of the chip, carbonizing the substrate by laser radiation to form a porous carbon layer, and infiltrating the metal thermal interface material into it to form a combination of the thermal interface material and the porous carbon layer, thereby hoping to reduce the overflow and splashing of the metal material. However, this solution has the disadvantage that the metal material cannot effectively fill the porous carbon layer, resulting in holes in the carbon layer that reduce the thermal conductivity. Therefore, it is urgent to explore new solutions to solve the overflow problem. Summary of the invention

[0005] The purpose of the present invention is to provide a metal thermal interface material anti-overflow packaging solution to address the deficiencies in the above-mentioned background technology, so as to significantly improve its thermal conductivity, avoid overflow and sputtering, and reduce the probability of chip electrical performance degradation caused by this.

[0006] In order to achieve the above object, the present invention provides a chip packaging method based on a metal thermal interface material, comprising the following steps:

[0007] S1, the chip is connected to the substrate through FCBGA packaging;

[0008] S2, attaching a layer of hydrosol on the surface of the chip;

[0009] S3, device plastic encapsulation, so that the plastic encapsulation material forms a dam around the chip and the hydrosol;

[0010] S4, using a special solvent to remove the hydrosol on the chip, and drying the device to keep it dry;

[0011] S5, spraying a layer of flux evenly on the upper surface of the chip;

[0012] S6, mounting the metal thermal interface material on the upper surface of the chip by a chip mounter;

[0013] S7, mounting the heat dissipation cover so that the heat dissipation cover is connected to the plastic packaging material;

[0014] S8, passing the device through a high-temperature reflow device to complete the high-temperature reflow of the metal thermal interface material, thereby achieving the connection between the metal thermal interface material, the chip, and the heat dissipation cover.

[0015] Furthermore, S1 includes the following sub-steps:

[0016] S11, placing the flip chip on the substrate and docking it through solder balls;

[0017] S12, placing the device in a reflow oven for heating to melt the solder balls and form electrical connections;

[0018] S13, removing impurities on the surface of the substrate and the chip;

[0019] S14, drying the cleaned device;

[0020] S15, filling the bottom of the chip with underfill glue;

[0021] S16, curing the underfill to ensure that the underfill is firmly bonded between the substrate and the chip.

[0022] Furthermore, the thickness of the hydrosol in S2 is consistent with the thickness of the metal thermal interface material.

[0023] Furthermore, S3 includes the following sub-steps:

[0024] S31, installing the plastic packaging mold;

[0025] S32, using plasma cleaning to reduce surface tension;

[0026] S33, uses a high-precision vacuum laminator to evenly coat the plastic sealant around the chip, controlling the temperature, pressure and time;

[0027] S34, removing moisture from the plastic compound by using an oven.

[0028] Furthermore, S7 includes the following sub-steps:

[0029] S71, coating a layer of adhesive on the upper surface of the plastic packaging material according to the shape of the heat dissipation cover, so as to fix the heat dissipation cover in place;

[0030] S72, precisely mounts the heat sink cover on the chip and controls the pressure and temperature during the mounting process;

[0031] S73, placing the device in an oven to complete the curing of the adhesive.

[0032] Furthermore, in S3, the height of the plastic encapsulation material is flush with the upper surface of the metal thermal interface material.

[0033] Furthermore, a first protrusion and a second protrusion are provided on the lower surface of the heat dissipation cover, the first protrusion contacts the upper surface of the metal thermal interface material, and the second protrusion contacts the upper surface of the molding compound.

[0034] Furthermore, the metal thermal interface material is an indium sheet.

[0035] The above scheme of the present invention has the following beneficial effects:

[0036] The chip packaging method based on metal thermal interface material provided by the present invention forms protection around the metal thermal interface material by plastic packaging material, effectively preventing the overflow of the metal thermal interface material during high-temperature reflow, and reducing the risk of device short circuit; at the same time, by controlling the metal thermal interface material not to overflow, the coverage rate of the metal thermal interface material is increased and a low porosity rate is achieved, effectively reducing the thermal resistance of the packaging interface, enhancing the thermal conductivity of the packaging, and being conducive to improving the reliability of the chip and the packaging;

[0037] The present invention uses hydrosol to replace the metal thermal interface material and soldering flux during the plastic sealing process, which can effectively reduce the volatilization of soldering flux and oxidation of the metal thermal interface material caused by high temperature during the plastic sealing process, and no plastic sealing mold causes damage and pollution to the metal thermal interface material, thereby avoiding an increase in the porosity and a decrease in the coverage rate during the subsequent high-temperature reflow process;

[0038] The present invention can help solve the power consumption wall of high computing power, high power consumption processors, Al and HPC products;

[0039] Other beneficial effects of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of the steps of the present invention;

[0041] Figure 2 It is a schematic diagram of the chip packaging structure of the present invention;

[0042] Figure 3It is a schematic diagram of steps S2 to S4 of the present invention.

[0043] [Description of Reference Numerals]

[0044] 1-substrate; 2-chip; 3-solder ball; 4-underfill; 5-hydrosol; 6-plastic encapsulation material; 7-metal thermal interface material; 8-heat dissipation cover; 9-adhesive. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0047] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a locking connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] like Figure 1 , Figure 2 As shown, an embodiment of the present invention provides a chip packaging method based on a metal thermal interface material, which specifically includes the following steps:

[0049] S1, completing reliable connection between chip 2 and substrate 1 through FCBGA packaging. This step may specifically include the following sub-steps:

[0050] S11, accurately placing the flip chip 2 on the substrate 1, and docking it through the solder balls 3 or other connection points;

[0051] S12, placing the device in a reflow oven for heating, so that the solder ball 3 melts and forms a reliable electrical connection;

[0052] S13, removing residual flux or other impurities on the surface of the substrate 1 and the chip 2 to ensure the cleanliness of the welding points;

[0053] S14, drying the cleaned device to remove any residual moisture;

[0054] S15, filling the bottom of the chip 2 with a dedicated underfill 4 to provide mechanical support and protection;

[0055] S16 , curing the underfill 4 to ensure that the underfill 4 forms a firm bond between the substrate 1 and the chip 2 .

[0056] S2, attaching a layer of hydrosol 5 with the same thickness as the metal thermal interface material to the upper surface of the chip 2, so as to form a good interface in the subsequent steps.

[0057] S3, plastic-encapsulating the device. This step may specifically include the following sub-steps:

[0058] S31, ensuring that the plastic encapsulation material 6 can perfectly fit the shapes of the chip 2 and the substrate 1 by customizing an optimized plastic encapsulation mold;

[0059] S32, using plasma cleaning to reduce surface tension, improve fluidity of the plastic packaging material 6, and reduce the occurrence of plastic packaging voids;

[0060] S33, using a high-precision vacuum plastic packaging machine to evenly coat the plastic packaging material 6 around the chip 2, strictly controlling the temperature, pressure and time to ensure that the plastic packaging material 6 completely fills the guide holes of the substrate 1;

[0061] S34, after the plastic packaging is completed, the moisture in the plastic packaging material 6 is removed by an oven to prevent the moisture from affecting the subsequent processes.

[0062] S4, using a special solvent to remove the hydrosol 5 on the chip 2, and then drying the device to ensure a dry state.

[0063] S5, spray a layer of soldering flux evenly on the upper surface of the chip 2. The soldering flux is used to initially connect the metal thermal interface material 7 and promote better adhesion and flow of the metal thermal interface material 7 during the reflow process.

[0064] S6, the metal thermal interface material 7 is mounted on the upper surface of the chip 2 by a high-precision automatic placement machine. The dimensional accuracy of the automatic placement machine and the chip 2 determines the position of the metal thermal interface material 7, ensuring good thermal interface performance.

[0065] S7, mounting the heat dissipation cover 8. This step may specifically include the following sub-steps:

[0066] S51, coating a layer of adhesive 9 on the upper surface of the plastic packaging material 6 according to the shape of the heat dissipation cover 8, so as to fix the heat dissipation cover 8 in place;

[0067] S52, accurately mounting the heat dissipation cover 8 on the chip 2, and controlling the pressure and temperature during the mounting process;

[0068] S53, placing the device in an oven to complete the curing of the adhesive 9.

[0069] S8 , passing the device through a high-temperature reflow device to complete the high-temperature reflow of the metal thermal interface material 7 , thereby achieving connection between the metal thermal interface material 7 , the chip 2 , and the heat dissipation cover 8 .

[0070] Through the above steps, the packaging of the metal thermal interface material 7 can be completed. The metal thermal interface material 7 is located between the chip 2 and the heat dissipation cover 8, and the heat of the chip 2 is timely and efficiently discharged through the heat dissipation cover 8, so as to avoid the chip 2 from being overheated and causing performance degradation or even burning. Among them, the plastic encapsulation material 6 is located around the chip 2 and wraps the bottom filler 4, the chip 2, and the metal thermal interface material 7. Since the height of the plastic encapsulation material 6 is level with the upper surface of the metal thermal interface material 7, the plastic encapsulation material 6 forms a barrier and protection effect on the molten metal thermal interface material 7 through the surrounding dam formed during the high-temperature reflow process of the metal thermal interface material 7, effectively avoiding various process and reliability problems caused by its overflow. That is, the height of the plastic encapsulation material 6 needs to be significantly higher than the height of the chip 2, so as to enclose a space above the chip 2 to accommodate the metal thermal interface material 7, which is also significantly different from the prior art.

[0071] At the same time Figure 3 As shown, the method utilizes the water-soluble property of the hydrosol 5 to form a high-precision dam of plastic packaging material 6 with controllable morphology around the chip 2 in advance, removes the glue and sprays the flux after the plastic packaging process, and then mounts the metal thermal interface material 7 and the heat dissipation cover 8, which completely avoids the volatilization of the flux and the oxidation of the metal thermal interface material 7 caused by the high temperature generated during the plastic packaging process, and the metal thermal interface material 7 will not be damaged or contaminated by the plastic packaging mold, thus avoiding the problems of increased porosity and reduced coverage during the subsequent high-temperature reflow process.

[0072] It should be noted that the high temperature reflow of the metal thermal interface material 7 refers to melting the metal thermal interface material 7 by heating, and then cooling and solidifying, so as to form a strong connection. Through high temperature reflow, the metal thermal interface material 7 is heated to the melting temperature, so that it flows and fills the small gap between the chip 2 and the heat dissipation cover 8, and then cools and solidifies to form a good connection. This method can improve the connection reliability and heat conduction efficiency.

[0073] It is worth mentioning that the heat dissipation cover 8 in the prior art is usually directly connected to the substrate 1 through the adhesive 9. In this case, the heat dissipation cover 8 needs to be made relatively large, and on the basis of covering the entire chip 2 area, it also needs to extend to the substrate 1 position around the chip 2 for connection. In this embodiment, since the height of the plastic encapsulation material 6 is level with the metal thermal interface material 7, the adhesive 9 can be directly coated on the upper surface of the plastic encapsulation material 6, and then the heat dissipation cover 8 is pasted. Therefore, the heat dissipation cover 8 does not need to be connected to the substrate 1, and its size can be made smaller, which further improves the compactness of the structure, thereby being able to increase the density of the chip 2 arrangement on the substrate 1.

[0074] Please refer again Figure 2 Based on the same inventive concept, this embodiment also provides a chip structure based on metal thermal interface material, including substrate 1, chip 2, plastic encapsulation material 6, metal thermal interface material 7 and heat dissipation cover 8. Among them, chip 2 is electrically connected to substrate 1 through solder balls 3 or other solder joints, and bottom filler 4 is filled between chip 2 and substrate 1. Metal thermal interface material 7 is arranged on the upper surface of chip 2, and heat dissipation cover 8 is arranged above chip 2. Metal thermal interface material 7 is used to connect the upper surface of chip 2 and the lower surface of heat dissipation cover 8 to form a heat conduction path. Plastic encapsulation material 6 is arranged around chip 2 and metal thermal interface material 7, and acts as a dam to protect chip 2 and metal thermal interface material 7. Among them, the upper surface of the dam formed by plastic encapsulation material 6 is coated with adhesive 9, and the bottom of heat dissipation cover 8 is connected to the upper surface of plastic encapsulation material 6 through adhesive 9.

[0075] Among them, the height of the plastic packaging material 6 can be flush with the metal thermal interface material 7, or can be higher than the metal thermal interface material 7. At this time, a first protrusion and a second protrusion can be set on the lower surface of the heat dissipation cover 8. The first protrusion contacts the upper surface of the metal thermal interface material 7, and the second protrusion contacts the upper surface of the plastic packaging material 6. While ensuring the heat dissipation effect and firm connection, the weight of the heat dissipation cover 8 can also be reduced.

[0076] The metal thermal interface material 7 may be an indium sheet or other commonly used metal materials. This is only an example and is not specifically limited. Those skilled in the art may make the actual selection according to the process requirements.

[0077] The chip structure based on the metal thermal interface material provided in this embodiment has the same inventive concept and the same beneficial effects as the aforementioned packaging method, which will not be described in detail here.

[0078] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A chip packaging method based on metal thermal interface material, characterized in that: The steps include: S1, the chip is connected to the substrate through FCBGA packaging; S2, attaching a layer of hydrosol on the surface of the chip; S3, device plastic encapsulation, so that the plastic encapsulation material forms a dam around the chip and the hydrosol; S4, using a special solvent to remove the hydrosol on the chip, and drying the device to keep it dry; S5, spraying a layer of flux evenly on the upper surface of the chip; S6, mounting the metal thermal interface material on the upper surface of the chip by a chip mounter; S7, mounting the heat dissipation cover so that the heat dissipation cover is connected to the plastic packaging material; S8, passing the device through a high-temperature reflow device to complete the high-temperature reflow of the metal thermal interface material, thereby achieving the connection between the metal thermal interface material, the chip, and the heat dissipation cover.

2. A chip packaging method based on metal thermal interface material according to claim 1, characterized in that: S1 includes the following sub-steps: S11, placing the flip chip on the substrate and docking it through solder balls; S12, placing the device in a reflow oven for heating to melt the solder balls and form electrical connections; S13, removing impurities on the surface of the substrate and the chip; S14, drying the cleaned device; S15, filling the bottom of the chip with underfill glue; S16, curing the underfill to ensure that the underfill is firmly bonded between the substrate and the chip.

3. The chip packaging method based on metal thermal interface material according to claim 1, characterized in that: The thickness of the hydrosol in S2 is consistent with the thickness of the metal thermal interface material.

4. The chip packaging method based on metal thermal interface material according to claim 1, characterized in that: S3 includes the following sub-steps: S31, installing the plastic packaging mold; S32, using plasma cleaning to reduce surface tension; S33, uses a high-precision vacuum laminator to evenly coat the plastic sealant around the chip, controlling the temperature, pressure and time; S34, removing moisture from the plastic compound by using an oven.

5. The chip packaging method based on metal thermal interface material according to claim 1, characterized in that: S7 includes the following sub-steps: S71, coating a layer of adhesive on the upper surface of the plastic packaging material according to the shape of the heat dissipation cover, so as to fix the heat dissipation cover in place; S72, precisely mounts the heat sink cover on the chip and controls the pressure and temperature during the mounting process; S73, placing the device in an oven to complete the curing of the adhesive.

6. The chip packaging method based on metal thermal interface material according to claim 1, characterized in that: In S3, the height of the molding compound is flush with the upper surface of the metal thermal interface material.

7. The chip packaging method based on metal thermal interface material according to claim 1, characterized in that: The lower surface of the heat dissipation cover is provided with a first protrusion and a second protrusion, the first protrusion contacts the upper surface of the metal thermal interface material, and the second protrusion contacts the upper surface of the molding compound.

8. The chip packaging method based on metal thermal interface material according to claim 1, characterized in that: The metal thermal interface material is an indium sheet.

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