An encapsulation method and an encapsulation structure made by using the same

Abstract

The present invention discloses a packaging method and a packaging structure made by using the same. The packaging method includes: disposing an organic carbonizable substrate on the upper surface of a chip, irradiating the organic carbonizable substrate with laser to cause carbonization, generating and escaping gas during the carbonization process to form a porous carbon layer having pores and adhering to the upper surface of the chip, opening at least one through-hole area penetrating up and down in a position area of the porous carbon layer far from its own edge, disposing a thermal interface material on the porous carbon layer, performing a preheating treatment to enable the thermal interface material to flow and partially penetrate into the pores and / or the through-hole area to form a combination of the thermal interface material and the porous carbon layer, and partially mounting a heat dissipation cover on the combination; and the packaging structure made by the above method, which can avoid problems such as low strength and easy interface delamination, poor thermal conductivity, and easy splashing during melting, which may cause short circuits of passive components, when the existing thermal interface material is mounted on the chip.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly relates to a packaging method and a packaging structure manufactured by using the same. Background Art

[0002] Since the flip chip ball grid array (FCBGA) packaging technology can achieve high-density interconnection, it is widely used for packaging semiconductor devices. As the packaging size gradually increases and the solder joint density continuously improves, warpage and heat dissipation performance have become key issues in flip chip packaging. The traditional flip chip structure usually includes a chip, chip bumps, underfill, a substrate, its backside solder balls, and other passive components. To control warpage, adhesives are required to fix stiffeners on the substrate. Currently, in order to improve heat dissipation performance while controlling warpage, a thermal interface material (TIM) and a heat sink cover are usually attached to the backside of the silicon chip.

[0003] Currently, the commercially available TIM materials can be classified into organic TIM materials and metal TIM materials. However, it has been found in practice that the problems faced by the current organic TIM materials are low strength and easy interface delamination, and poor thermal conductivity (generally only about 2 - 10 W / (m·K)); during the practice of metal TIM materials, splashing is likely to occur during adhesive melting, which may cause short circuits in passive components. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and provide an improved packaging method, which can avoid problems such as low strength, easy interface delamination, low thermal conductivity, and splashing during adhesive melting that may cause short circuits in passive components when the existing thermal interface materials are mounted on the chip.

[0005] The present invention also provides a packaging structure manufactured by using the above packaging method.

[0006] To achieve the above object, a technical solution adopted by the present invention is:

[0007] A packaging method, which includes:

[0008] Providing an organically carbonizable substrate on the upper surface of the chip, irradiating the organically carbonizable substrate with a laser to cause carbonization, generating and escaping gases during the carbonization process, forming a porous carbon layer with pores and attached to the upper surface of the chip, and opening at least one vertically penetrating hollowed-out area in a position area of the porous carbon layer far from its own edge;

[0009] Providing a thermal interface material on the porous carbon layer, performing a preheating treatment to enable the thermal interface material to flow and partially penetrate into the pores and / or the hollowed-out area, forming a combination of the thermal interface material and the porous carbon layer;

[0010] Mount the heat dissipation cover part on the said assembly.

[0011] According to some preferred aspects of the present invention, the organic carbonizable substrate is an organic polymer film.

[0012] Furthermore, the organic polymer film contains a rigid molecular chain structure, and the rigid molecular chain structure includes benzene rings and / or condensed rings, which is beneficial to obtaining a porous carbon layer with a high carbon content, good thermal conductivity, and high strength.

[0013] According to some preferred and specific aspects of the present invention, the organic carbonizable substrate is a combination of one or more selected from aromatic polyimide, polyether ether ketone, and bisphenol A epoxy resin.

[0014] According to some preferred aspects of the present invention, the carbonization is carried out in the laser scanning mode of laser irradiation, and the hollowed-out area is produced by using the laser drilling mode of laser irradiation;

[0015] The conditions of the laser scanning mode are: the laser wavelength is 300 nm - 12 μm, the laser power is 0.1 - 4 W, the scanning speed is 1 - 300 mm / s, and the scanning interval is 10 - 200 μm; the conditions of the laser drilling mode are: the laser wavelength is 300 nm - 12 μm, the laser power is 0.1 - 4 W, the drilling time is 0.1 - 30 s, and the drilling interval is 10 - 200 μm.

[0016] In the present invention, using the laser scanning mode and the laser drilling mode can quickly obtain the corresponding effects in-situ, which can reduce or even avoid affecting other components other than the organic carbonizable substrate. At the same time, the organic carbonizable substrate is cheap and easily available, and is printed by the laser method, at normal temperature and pressure, without the need to control the atmosphere, and can be quickly prepared under laser irradiation for a short time (for example, dozens of seconds), which is suitable for large-scale production. In addition, the shape of the hollowed-out area can be adjusted or designed, and the hollowed-out area of the porous carbon layer can be customized according to the chip size.

[0017] In some embodiments of the present invention, the thickness of the organic carbonizable substrate is 50 - 500 μm.

[0018] According to some preferred aspects of the present invention, the area of the upper opening of the hollowed-out area accounts for 20% - 80% of the upper surface area of the porous carbon layer.

[0019] In some embodiments of the present invention, the hollowed-out area can be in the shape of a through hole, and its cross-sectional shape can be circular, elliptical, square, etc.

[0020] According to some preferred aspects of the present invention, the thermal interface material is an organic thermal interface material or a metal thermal interface material;

[0021] Among them, when the thermal interface material is an organic thermal interface material, the temperature of the preheating treatment is below the curing temperature of the organic thermal interface material;

[0022] When the thermal interface material is a metal thermal interface material, the temperature of the preheating treatment is below the melting point of the metal thermal interface material.

[0023] According to some specific aspects of the present invention, the organic thermal interface material is a silicone-based thermal interface material, a silicone grease-based thermal interface material, or a combination of both, and the thickness of the organic thermal interface material is 50 - 100 μm.

[0024] According to some specific aspects of the present invention, the metal thermal interface material is a solid metal with good thermal conductivity, such as indium flakes and / or copper flakes, and the thickness of the metal thermal interface material is 200 - 500 μm.

[0025] According to some preferred and specific aspects of the present invention, the implementation manner of the encapsulation method includes:

[0026] After the chip and the substrate complete the reflow soldering and underfill processes, an organic carbonizable substrate is disposed on the upper surface of the chip, and the organic carbonizable substrate is irradiated in situ in a laser scanning mode of laser irradiation. After the organic carbonizable substrate absorbs light energy, it heats up and carbonizes, generating and escaping gases during the carbonization process, forming a porous carbon layer with pores and attached to the upper surface of the chip. Then, at least one vertically penetrating hollowed-out area is opened in a position area of the porous carbon layer far from its own edge by using the laser drilling mode of laser irradiation;

[0027] Then, the thermal interface material is disposed on the porous carbon layer, and preheated, so that the thermal interface material can flow to partially penetrate into the pores and / or the hollowed-out area, and cooled to form a combination of the thermal interface material and the porous carbon layer;

[0028] The heat dissipation cover is respectively mounted on the combination and the substrate, and the mounting includes one or more of heat curing, reflow soldering, and bonding (such as adhesive bonding).

[0029] In some implementation manners of the present invention, the implementation manner of the encapsulation method further includes: after the chip and the substrate complete the reflow soldering and underfill processes, metallization treatment is performed on the side of the chip away from the substrate (usually called the back side) (the metallization treatment can set a barrier layer, a bonding layer, and an anti-oxidation protection layer, and the specific material for the metallization treatment can be titanium, nickel, silver, gold, etc.), and then the organic carbonizable substrate is disposed.

[0030] In some embodiments of the present invention, when the thermal interface material is an organic thermal interface material, the mounting includes: heating and curing (to cause the organic thermal interface material to achieve curing and crosslinking at a corresponding temperature, improving the adhesiveness), and a load not exceeding the pressure that the assembly can withstand may also be applied to complete the bonding between the heat dissipation cover, the chip, and the substrate (adhesive can be provided on the substrate to achieve bonding with a partial area of the heat dissipation cover, and the setting position can be set with reference to existing conventional methods).

[0031] In some embodiments of the present invention, when the thermal interface material is a metal thermal interface material, the mounting includes: reflow soldering, which further softens or melts the metal thermal interface material and makes it fluid, so that it can penetrate more into the pores and / or the hollowed-out areas of the porous carbon layer to achieve excellent combination of the two. At the same time, further softening or melting and being fluid can also achieve bonding with the heat dissipation cover and firmly connect after cooling. In addition, the volatilization of the flux can be carried out under a vacuum condition (generally, when using a metal thermal interface material, flux spraying will be performed, for example, it can be sprayed on the back gold layer after back metallization treatment). A load not exceeding the pressure that the assembly can withstand may also be applied to complete the bonding between the heat dissipation cover, the chip, and the substrate (adhesive can be provided on the substrate to achieve bonding with a partial area of the heat dissipation cover, and the setting position can be set with reference to existing conventional methods).

[0032] Another technical solution provided by the present invention: a packaging structure made by the above packaging method, the packaging structure includes a substrate, a flip chip fixed on the substrate, and a heat dissipation cover, and a combination of a thermal interface material and a porous carbon layer is provided between the flip chip and the heat dissipation cover.

[0033] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0034] Based on the problems existing in the existing mounted organic thermal interface materials, such as low strength and easy interface delamination, low thermal conductivity, and the problems existing in the mounted metal thermal interface materials, such as easy splashing during melting, which may lead to short circuits of passive components, the present invention innovatively provides a packaging method that can simultaneously solve the corresponding problems existing in the mounted organic thermal interface materials and the mounted metal thermal interface materials. This packaging method adopts a unique step of setting an organic carbonizable substrate. Utilizing the characteristics that the organic carbonizable substrate can be laser carbonized and gas escapes, when the organic carbonizable substrate is set on the upper surface of the chip, after laser carbonization treatment, a porous carbon layer attached to the chip and having pores can be obtained. Combining with the hollowed-out area opened in the position area far from the edge of the porous carbon layer, after mounting the thermal interface material, preheating the mounted thermal interface material can fix or limit the thermal interface material on the porous carbon layer in advance. In fact, the specific porous carbon layer formed by the method of the present invention simultaneously serves as a thermal conductivity enhancing component, a support structure, and an anti-spill fence of the thermal interface material. And due to the combination of the pores and the hollowed-out area on the porous carbon layer, the thermal interface material not only realizes mutual nesting with the porous carbon layer but also realizes bonding with the chip. In this way, the chip, the porous carbon layer, and the thermal interface material are firmly combined together, forming an integral body with high thermal conductivity, good strength, not easy to peel off, and having the function of preventing fluid from flowing arbitrarily. When the heat dissipation cover is mounted later, for the organic thermal interface material or the metal thermal interface material, whether it is the heating and curing operation or the reflow soldering operation, etc., it can basically only make the thermal interface material change within the stable porous carbon layer range and realize connection with the heat dissipation cover, so that the overall structure of the packaging structure made by the packaging method of the present invention is stable, and the thermal interface material is not easy to have interface delamination. Especially for the organic thermal interface material, the existence of the porous carbon layer greatly improves the thermal conductivity and structural strength of the overall packaging structure. For the metal thermal interface material, the existence of the porous carbon layer increases the surface tension of the molten metal and can thus control the fluidity, preferably avoiding problems such as short circuits of passive components that may be caused by metal melting and splashing.

[0035] The packaging method of the present invention is applicable to various thermal interface materials, has strong universality, and has the prospect of industrial application. Brief Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic diagram of setting an organic carbonizable substrate on the upper surface of the chip in the packaging method of the embodiment of the present invention;

[0038] Figure 2 Schematic diagram after carbonization and opening of the hollow area in the encapsulation method of the embodiment of the present invention;

[0039] Figure 3 is Figure 2 The enlarged schematic diagram of part A in

[0040] Figure 4 Schematic diagram after the thermal interface material is disposed on the porous carbon layer and preheated in the encapsulation method of the embodiment of the present invention;

[0041] Figure 5 is Figure 4 The enlarged schematic diagram of part B in

[0042] Figure 6 Schematic diagram after the heat dissipation cover is mounted in the encapsulation method of the embodiment of the present invention;

[0043] Figure 7 One of the schematic diagrams of the porous carbon layer with a hollow area in the embodiment of the present invention;

[0044] Figure 8 Another schematic diagram of the porous carbon layer with a hollow area in the embodiment of the present invention;

[0045] Figure 9 Still another schematic diagram of the porous carbon layer with a hollow area in the embodiment of the present invention;

[0046] Wherein, 1, chip; 2, organic carbonizable substrate; 3, substrate; 4, laser device; 5, porous carbon layer; 51, pore; 52, hollow area; 6, thermal interface material; 7, heat dissipation cover; 8, adhesive. Detailed implementation manners

[0047] The following further describes the above solution with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited by the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements. In the description of the present invention, it should also be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the machine or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0048] See Figures 1-9 , Figures 1-6 is the flow schematic diagram of the encapsulation method provided by the embodiment of the present invention, and can be made into an encapsulation structure.Figures 7-9 FIG. 1 is a schematic structural view of a porous carbon layer with a hollowed-out area provided in an embodiment of the present invention.

[0049] Specifically, the encapsulation method includes the following steps:

[0050] (1) Dispose an organically carbonizable substrate 2 on the upper surface of the chip 1;

[0051] (2) Laser irradiate the organically carbonizable substrate 2 to cause carbonization. During the carbonization process, gas is generated and escapes, forming a porous carbon layer 5 having pores 51 and adhering to the upper surface of the chip 1. At least one vertically penetrating hollowed-out area 52 is opened in a position area of the porous carbon layer 5 away from its own edge;

[0052] (3) Dispose a thermal interface material 6 on the porous carbon layer 5 and perform a preheating treatment so that the thermal interface material 6 can flow to partially penetrate into the pores 51 and / or the hollowed-out area 52, forming a combination of the thermal interface material 6 and the porous carbon layer 5;

[0053] (4) Partially mount the heat dissipation cover 7 on the combination, and at the same time mount the heat dissipation cover 7 on the substrate 3.

[0054] Referring to Figure 1 As shown, the chip 1 has been mounted on the substrate 3. The organically carbonizable substrate 2 can be a substrate with a sheet structure and is directly placed on the upper surface of the chip 1. Preferably, the size of the organically carbonizable substrate 2 in the horizontal direction does not exceed the outer contour size of the chip 1 in the horizontal direction and can be set to exactly match, with their edges aligned, which is beneficial to forming a porous carbonized layer at all positions on the upper surface of the chip 1.

[0055] Optionally, the operation of mounting the chip 1 on the substrate 3 generally includes: soldering the bumps at the bottom of the chip 1 to the surface of the substrate 3 by means of reflow soldering, and then performing underfill on the bottom of the chip 1. For example, an epoxy resin glue can be filled into the soldering positions of the bumps at the bottom of the chip 1 by capillary action to protect the strength of the bumps; among them, the bumps can be solder ball solder joints or copper pillar plus tin cap structures, and the shape can be circular or oval, etc.

[0056] Furthermore, the organic carbonizable substrate 2 may be an organic polymer film. The polymer film generates some gases during the carbonization process. The gases escape from the carbon layer formed by carbonization and give the carbonized layer a certain pore 51 structure. Preferably, the organic polymer film contains a rigid molecular chain structure, which includes benzene rings and / or condensed rings, which is conducive to obtaining a porous carbon layer 5 with high carbon content, good thermal conductivity, high strength and stable structure. Specifically, the organic carbonizable substrate 2 may be aromatic polyimide, polyetheretherketone, bisphenol A epoxy resin, etc. This embodiment does not specifically limit this, as long as the function of this embodiment can be achieved. Therefore, the organic carbonizable substrate 2 may also be other polymer materials with corresponding effects, such as polyphenylene sulfide, etc.

[0057] Optionally, the thickness of the organic carbonizable substrate 2 may be determined with reference to the size of the chip 1 , and further, may be 50-500 μm, 60-400 μm, or 100-300 μm, etc.

[0058] See also Figure 2 As shown, it will be Figure 1 The processed overall structure is moved into the laser processing area, and the laser device 4 is used to in-situ irradiate the organic carbonizable substrate 2 in a laser scanning mode of laser irradiation. After absorbing light energy, the organic carbonizable substrate 2 heats up to undergo rapid carbonization. During the carbonization process, gas is generated and escapes from the carbonized layer, thereby forming a porous carbon layer 5 having pores 51 and attached to the upper surface of the chip 1. In order to further improve the efficacy of the porous carbon layer 5, a laser drilling mode of laser irradiation is used to open at least one hollow area 52 that passes through the porous carbon layer 5 from top to bottom in a position area away from its own edge. The reason for doing this in a position area away from its own edge is mainly to prevent the hollow area 52 from being connected to the outside in the left-right or front-back direction. There is at least one hollow area 52, and it can be 2, 3, 4 or even more. The number is set according to actual needs. The shape of the hollow area 52 is not specifically limited, and it can be circular, square, elliptical, etc.

[0059] Optionally, the conditions for the laser scanning mode are as follows: the laser wavelength is 300 nm - 12 μm, the laser power is 0.1 - 4 W, the scanning speed is 1 - 300 mm / s, and the scanning interval is 10 - 200 μm; further, for example, it can be: the laser wavelength is 300 nm - 500 nm, the laser power is 1 - 4 W, the scanning speed is 10 - 30 mm / s, and the scanning interval is 50 - 100 μm; it can also be: the laser wavelength is 500 nm - 1 μm, the laser power is 1 - 4 W, the scanning speed is 30 - 50 mm / s, and the scanning interval is 100 - 150 μm; it can further be: the laser wavelength is 1 μm - 12 μm, the laser power is 1 - 4 W, the scanning speed is 20 - 100 mm / s, and the scanning interval is 100 - 200 μm.

[0060] Optionally, the conditions for the laser drilling mode are as follows: the laser wavelength is 300 nm - 12 μm, the laser power is 0.1 - 4 W, the drilling time is 0.1 - 30 s, and the drilling interval is 10 - 200 μm; further, for example, it can be: the laser wavelength is 2 μm - 12 μm, the laser power is 1 - 4 W, the drilling time is 10 - 30 s, and the drilling interval is 0.02 - 0.08 mm; it can also be: the laser wavelength is 5 μm - 12 μm, the laser power is 1 - 4 W, the drilling time is 20 - 30 s, and the drilling interval is 0.03 - 0.7 mm.

[0061] See Figure 3 as shown, which magnifies a partial area in Figure 2 It can be known that after the setting of the carbonized and hollowed - out area 52, there are many pores 51 and the vertically - penetrating hollowed - out area 52 distributed on the porous carbon layer 5.

[0062] In fact, in this example, the use of the laser scanning mode and the laser drilling mode can quickly obtain the corresponding effects in - situ, which can reduce or even avoid affecting other components other than the organic carbonizable substrate 2. At the same time, the organic carbonizable substrate 2 is cheap and easily available. By laser printing at normal temperature and pressure without the need to control the atmosphere, it can be quickly prepared under laser irradiation for a short time (such as dozens of seconds), which is suitable for large - scale production. In addition, the shape of the hollowed - out area 52 can be adjusted or designed. The hollowed - out area 52 of the porous carbon layer 5 can be customized according to the size of the chip 1. At the same time, the area of the hollowed - out area 52 can also be set. For example, taking the area of the upper opening of the hollowed - out area 52 (the opening is on the upper surface of the porous carbon layer 5) as a reference, it is preferably made to occupy 20% - 80% of the upper surface area of the porous carbon layer 5, for example, it can account for 30 - 60% or 40 - 70%, etc.

[0063] After the hollowed - out area 52 is opened in the porous carbon layer 5, see Figures 4-5As shown, the thermal interface material 6 is disposed on the porous carbon layer, and is subjected to a heating treatment so that the thermal interface material 6 can flow to partially penetrate into the pores 51 and / or the hollowed-out area 52 to form a composite of the thermal interface material 6 and the porous carbon layer 5; for further reference, see Figure 4 The enlarged view at B in Figure 5 , which exemplarily shows the bonding state of the thermal interface material 6 and the porous carbon layer 5 after the heating and preheating treatment. Of course, this figure is only an exemplary illustration. In practice, the pore 51 structure of the porous carbon layer 5 is relatively small and generally difficult to be seen with the naked eye. After the heating and preheating treatment, the flowable thermal interface material 6 generally flows into the hollowed-out area 52 and the pores 51. Of course, part of it also exists on the surface of the porous carbon layer 5. At the same time, since the thermal interface material 6 can flow into the hollowed-out area 52 and the hollowed-out area 52 is vertically penetrated, the thermal interface material 6 can also achieve pre-bonding with the chip 1. Furthermore, when the composite formed by the thermal interface material 6 and the porous carbon layer 5 is bonded to the chip 1 respectively by the thermal interface material 6 and the porous carbon layer 5, a firm bond of the chip 1, the porous carbon layer 5 and the thermal interface material 6 is achieved. For example, from the comparison between Figures 2-3 and Figures 4-5 , it can be seen that the specific porous carbon layer 5 formed in this example actually acts as a thermal conductivity enhancing component, a support structure and an anti-overflow fence of the thermal interface material 6. And due to the combination of the pores 51 and the hollowed-out area 52 on the porous carbon layer 5, the thermal interface material 6 not only realizes mutual nesting with the porous carbon layer 5 but also realizes bonding with the chip 1, forming an integral body with high thermal conductivity, good strength, not easy to peel off and having the function of preventing fluid from flowing arbitrarily.

[0064] In this example, the thermal interface material 6 can be either an organic thermal interface material 6 or a metal thermal interface material 6; among them, when the thermal interface material 6 is an organic thermal interface material, the temperature of the preheating treatment is below the curing temperature of the organic thermal interface material. Since the organic thermal interface material is generally cross-linked and bonded by high-temperature thermal curing, by heating at a certain temperature to endow the organic thermal interface material with a certain fluidity, the organic thermal interface material can enter the pores 51 and / or the hollowed-out area 52 of the porous carbon layer 5 through its own flow or capillary adsorption action to achieve preliminary bonding;

[0065] When the thermal interface material 6 is a metal thermal interface material, the temperature of the preheating treatment is below the melting point of the metal thermal interface material, usually about 1-25 °C below the melting point. As long as the metal thermal interface material is endowed with a certain fluidity and can then penetrate or flow into the pores 51 and / or the hollowed-out area 52 of the porous carbon layer 5, and then preliminary bonding can be achieved after cooling.

[0066] Further, the organic thermal interface material can be a silicone-based thermal interface material, a silicone grease-based thermal interface material, or a combination of both, and the thickness of the organic thermal interface material is 50-100 μm.

[0067] Further, the metal thermal interface material can be a solid metal with good thermal conductivity, such as indium sheet and / or copper sheet, and the thickness of the metal thermal interface material is 200-500 μm.

[0068] Of course, only the organic thermal interface material and the metal thermal interface material are exemplified in this example. In other embodiments, the thermal interface material of other materials used in the art can also be used.

[0069] In this example, after the temperature-raising treatment of the thermal interface material is completed, refer to Figure 6 As shown, the heat dissipation cover 7 is partially mounted on the assembly, and at the same time, the heat dissipation cover 7 is mounted on the substrate 3. The mounting includes one or more of heat curing, reflow soldering, and bonding (for example, adhesive bonding can be used);

[0070] Further, the encapsulation method further includes: after the chip 1 and the substrate 3 complete the reflow soldering and underfill adhesive process, a metallization process is performed on the side of the chip 1 away from the substrate 3 (usually called the back side) (the metallization process can set a barrier layer, a bonding layer, and an anti-oxidation protection layer. The specific material for the metallization process can be titanium, nickel, silver, gold, etc.), and then the organic carbonizable substrate 2 is set.

[0071] Specifically, when the thermal interface material 6 is an organic thermal interface material, the mounting includes: heat curing (to make the organic thermal interface material achieve curing crosslinking at a corresponding temperature and improve the adhesiveness), and a load not exceeding the pressure that the assembly can withstand can also be applied to complete the bonding between the heat dissipation cover 7 and the chip 1 and the substrate 3 (an adhesive 8 can be set on the substrate 3 to achieve bonding with a partial area of the heat dissipation cover 7, and the setting position can be set with reference to the existing conventional method).

[0072] Specifically, when the thermal interface material 6 is a metal thermal interface material, the mounting includes: reflow soldering to further soften or melt the metal thermal interface material and make it fluid, so that it can penetrate more into the pores 51 and / or the hollowed-out areas 52 of the porous carbon layer 5, achieving excellent bonding between the two. At the same time, further softening or melting and becoming fluid can also bond and firmly connect with the heat dissipation cover 7. In addition, the flux can be volatilized under vacuum conditions (generally, when using a metal thermal interface material, flux spraying will be carried out, for example, it can be sprayed on the back gold layer after back metallization treatment). A load not exceeding the pressure that the assembly can withstand can also be applied to complete the bonding between the heat dissipation cover 7, the chip 1, and the substrate 3 (an adhesive 8 can be set on the substrate 3 to achieve bonding with a partial area of the heat dissipation cover 7, and the setting position can be set with reference to existing conventional methods).

[0073] Application Example 1: Use a robotic arm to pick up an aromatic polyimide film with the same size as the chip 1 (die) and a thickness of 100 μm, automatically align and place it above the chip 1. Set the laser scanning area as the entire aromatic polyimide film, and irradiate the aromatic polyimide film in-situ under the laser conditions of a laser wavelength of 10.64 μm, a power of 3 W, a scanning speed of 100 mm / s, and a scanning interval of 100 μm to form a porous carbon layer 5 with pores 51 above the chip 1 (die). At the same time, use the laser drilling mode again, under the laser conditions of a laser wavelength of 10.64 μm, a power of 3 W, a drilling interval of 0.05 mm, and a drilling time of 2 s, to create through-holes (i.e., hollowed-out areas 52) with an array distribution in the pre-formed porous carbon layer 5 (as shown in the appendix Figure 7 Or Figure 8 shown, Figure 7 the cross-section of the hollowed-out area 52 in Figure 8 is circular,

[0074] and the cross-section of the hollowed-out area 52 in

[0075] is square).

[0076] Application Example 2: Aromatic polyimide film with the same size as Chip 1 (after back gold treatment and spray fluxing) and a thickness of 200 μm is sucked by a robotic arm, automatically aligned and placed above Chip 1. The laser scanning area is set as the whole aromatic polyimide film, and the aromatic polyimide film is irradiated in-situ under the laser conditions of a laser wavelength of 10.64 μm, a power of 4 W, a scanning speed of 100 mm / s, and a scanning interval of 100 μm to form a porous carbon layer 5 with pores 51 above Chip 1. Then, using the laser drilling mode, under the laser conditions of a laser wavelength of 10.64 μm, a power of 4 W, a drilling interval of 0.05 mm, and a drilling time of 10 s, a square hollowed-out area 52 slightly smaller than the area of Chip 1 is created in the pre-formed porous carbon layer 5 to form a square fence (as Figure 9 shown), which can prevent the molten indium from overflowing and splashing as described below, and does not affect the volatilization of the flux.

[0077] Then, a metal indium sheet with a thickness of 230 μm is placed above the porous carbon layer 5 with the square fence. Since the melting point of indium is 156 °C, it is preheated to 135 °C to make it have a certain fluidity, promoting its infiltration into the porous carbon layer 5. After waiting for 1 min and cooling, a combination of indium and the porous carbon layer 5 is formed.

[0078] Subsequently, the heat sink cover 7 is mounted. An adhesive 8 is set at the corresponding position on the substrate 3. After reflow soldering with a peak temperature of about 245 °C, the flux is volatilized under the condition of a vacuum pressure of 3 KPa, and the bonding between the heat sink cover 7 and the chip 1 and the substrate 3 is completed under a load not exceeding the pressure that the combination can withstand.

[0079] In other embodiments, the present invention also provides a packaging structure made by the above method. The packaging structure includes a substrate, a flip-chip fixed on the substrate, and a heat sink cover. A combination of a thermal interface material and a porous carbon layer is provided between the flip-chip and the heat sink cover.

[0080] In summary, based on the problems existing in the existing organic thermal interface materials for mounting, such as poor thermal conductivity, low strength and easy interface delamination, and the problems existing in the mounting of metal thermal interface materials, such as easy splashing during melting, which may cause short circuits in passive components, the above packaging method innovatively provided by the present invention can solve the corresponding problems existing in the mounting of organic thermal interface materials and metal thermal interface materials respectively, is applicable to various thermal interface materials 6, has strong universality, and has the prospect of industrial application. In particular, it can also improve the thermal conductivity and structural strength of conventional organic thermal interface materials, the thermal interface material 6 is not easy to delaminate at the interface, and the surface tension of the molten metal is increased, thereby controlling the fluidity, so as to reduce or even inhibit the possibility of splashing or overflowing during the melting of the metal thermal interface material.

[0081] The above embodiments are only used to illustrate the technical concept and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A packaging method, characterized in that, The encapsulation method includes: An organically carbonizable substrate is provided on the upper surface of the chip, and the organically carbonizable substrate is irradiated with a laser to cause carbonization. During the carbonization process, gas is generated and escapes, forming a porous carbon layer with pores and attached to the upper surface of the chip. At least one vertically penetrating hollowed-out area is opened in a position area of the porous carbon layer far from its own edge; A thermal interface material is disposed on the porous carbon layer and preheated so that the thermal interface material can flow to partially penetrate into the pores and the hollowed-out area, forming a combination of the thermal interface material and the porous carbon layer; wherein, the thermal interface material is an organic thermal interface material or a metal thermal interface material; when the thermal interface material is an organic thermal interface material, the temperature of the preheating treatment is below the curing temperature of the organic thermal interface material; when the thermal interface material is a metal thermal interface material, the temperature of the preheating treatment is below the melting point of the metal thermal interface material; The heat dissipation cover is partially mounted on the combination.

2. The encapsulation method according to claim 1, characterized in that, The organically carbonizable substrate is an organic polymer film.

3. The encapsulation method according to claim 2, wherein The organic polymer film contains a rigid molecular chain structure, and the rigid molecular chain structure includes a benzene ring and / or a condensed ring.

4. The encapsulation method according to any one of claims 1 to 3, characterized in that The organically carbonizable substrate is a combination of one or more selected from aromatic polyimide, polyether ether ketone, and bisphenol A epoxy resin.

5. The encapsulation method according to claim 1, wherein The carbonization is carried out in a laser scanning mode in laser irradiation, and the hollowed-out area is produced by using a laser drilling mode in laser irradiation; The conditions of the laser scanning mode are: the laser wavelength is 300 nm - 12 μm, the laser power is 0.1 - 4 W, the scanning speed is 1 - 300 mm / s, and the scanning interval is 10 - 200 μm; The conditions of the laser drilling mode are: the laser wavelength is 300 nm - 12 μm, the laser power is 0.1 - 4 W, the drilling time is 0.1 - 30 s, and the drilling interval is 10 - 200 μm.

6. The encapsulation method according to claim 1, wherein The thickness of the organically carbonizable substrate is 50 - 500 μm; and / or, the area of the upper opening of the hollowed-out area accounts for 20% - 80% of the upper surface area of the porous carbon layer.

7. The encapsulation method according to claim 1, wherein The organic thermal interface material is a silicone-based thermal interface material, a silicon grease-based thermal interface material, or a combination of both. The thickness of the organic thermal interface material is 50 - 100 μm; and / or, the metal thermal interface material is an indium sheet and / or a copper sheet, and the thickness of the metal thermal interface material is 200 - 500 μm.

8. The encapsulation method according to claim 1, wherein The implementation manner of the encapsulation method includes: After the chip and the substrate complete the reflow soldering and underfill adhesive processes, an organically carbonizable substrate is provided on the upper surface of the chip, and the organically carbonizable substrate is irradiated in situ in a laser scanning mode of laser irradiation. After the organically carbonizable substrate absorbs light energy, it heats up and carbonizes. During the carbonization process, gas is generated and escapes, forming a porous carbon layer with pores and attached to the upper surface of the chip. Then, at least one vertically penetrating hollowed-out area is opened in a position area of the porous carbon layer far from its own edge by using a laser drilling mode of laser irradiation; Then, a thermal interface material is disposed on the porous carbon layer, and pre-heat treatment is performed to enable the thermal interface material to flow and partially penetrate into the pores and / or the hollowed-out area, and then cooled to form a combination of the thermal interface material and the porous carbon layer; The heat dissipation cover is respectively mounted on the combination and the substrate, and the mounting includes one or more of heat curing, reflow soldering, and bonding.

9. An encapsulation structure made by the encapsulation method according to any one of claims 1-8, the encapsulation structure comprising a substrate, a flip chip fixed on the substrate, and a heat dissipation cover, characterized in that, A combination formed by the thermal interface material and the porous carbon layer is provided between the flip chip and the heat dissipation cover.

Images