High-efficiency high-voltage large-current MOS (Metal Oxide Semiconductor) tube packaging process

Abstract

The invention belongs to the technical field of electronic packaging. The invention relates to a packaging technology, in particular to a high-efficiency high-voltage large-current MOS tube packaging technology. The packaging method comprises the following specific packaging steps: scribing: cutting and separating chips which are distributed on a wafer in a matrix form into independent single chips; coating nano-silver paste: coating the nano-silver paste between the chip and the pretreated DFN frame substrate; curing: curing the nano-silver paste in a heat treatment mode to form electrical connection; wherein the pretreatment step of pretreating the DFN frame substrate comprises the following steps: coating the surface, facing nano-silver paste, of the DFN frame substrate with a 1 # heat-conducting epoxy resin coating, and then heating and curing to form a thin film heat-conducting coating; and after intaglio printing 2 # heat-conducting epoxy resin paint on the surface of the film heat-conducting coating, heating and curing to form an island-shaped heat-conducting coating on the surface of the film heat-conducting coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic packaging. More specifically, it relates to a packaging process for high-performance high-voltage high-current MOS transistors. Background Art

[0002] For the packaging of high-performance high-voltage high-current MOS transistors, using a DFN frame for basic packaging can accelerate the heat dissipation process.

[0003] However, during long-term storage or transportation of the packaging frame, there may be impurities such as dust, oil, and oxides on its surface. If not removed, it will affect the heat dissipation effect of the product. Specifically, impurities such as dust and oil will hinder heat transfer and act as thermal insulators, resulting in a temperature increase in local areas. This will affect the heat dissipation effect of the MOS transistor, reducing its performance and reliability. For example, poor heat dissipation may cause the MOS transistor to overheat during high-power operation, thereby reducing its switching speed and conduction performance. In addition, oxide impurities may react chemically with the substrate material, causing changes in material properties or corrosion. For example, the oxide layer may react with the components in the silver paste, affecting its adhesion. The organic matter in the oil may decompose at high temperatures, generating pores or defects, affecting the reliability of the packaging. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: for the packaging of MOS transistors using a DFN frame substrate, the above problems easily caused by the dust, oil, and oxides remaining on the surface of the DFN frame substrate. The present invention provides a packaging process for high-performance high-voltage high-current MOS transistors.

[0005] The object of the present invention is to provide a packaging process for high-performance high-voltage high-current MOS transistors.

[0006] The above object of the present invention is achieved by the following technical solutions:

[0007] A packaging process for high-performance high-voltage high-current MOS transistors, the specific packaging steps include:

[0008] Dicing: Cutting and separating the chips distributed in a matrix on the wafer into independent single chips;

[0009] Coating with nano silver paste: Coating the nano silver paste between the chip and the pretreated DFN frame substrate;

[0010] Curing: Curing the nano silver paste by heat treatment to form an electrical connection;

[0011] Among them, the pretreatment steps of the pretreated DFN frame substrate include:

[0012] After coating the surface of the DFN framework substrate facing the nano silver paste with a No. 1 thermal conductive epoxy resin coating, it is heated and cured to form a thin film thermal conductive coating;

[0013] Then, after gravure printing a No. 2 thermal conductive epoxy resin coating on the surface of the thin film thermal conductive coating, it is heated and cured to form an island-shaped thermal conductive coating on the surface of the thin film thermal conductive coating.

[0014] Beneficial effects of the above technical solution:

[0015] The above technical solution uses a DNF framework substrate for encapsulation. This encapsulation method reduces the heat conduction path through a leadless design, enabling heat to be directly transferred from the chip to the substrate and then to the outside through the substrate, thus effectively improving the heat dissipation efficiency. Compared with conventional encapsulation forms, the temperature inside the chip can be reduced; however, the inventor found during actual research that during the storage of the DNF substrate, the surface facing the chip is prone to oxidation, forming an oxide layer. The presence of the oxide layer easily leads to a decrease in thermal conductivity, and the presence of the oxide layer can also weaken the bonding force between it and the nano silver paste, resulting in local desorption during the long-term use of the product, thus affecting the heat dissipation ability; in order to avoid the appearance of the oxide layer, methods such as surface coating with an anti-rust solution can be used, as well as a pickling pretreatment process before use. However, after the residual anti-rust solution is coated, it is easy to cause bubbles during the heating and curing process of the nano silver paste, or affect the interfacial bonding strength between the two, while pickling is prone to damage the product surface and the process is difficult to control;

[0016] Based on the existence of the above problems, the present invention first forms a thin film thermal conductive coating on the surface of the framework substrate. On the one hand, it protects the surface of the DFN framework substrate to prevent the formation of an oxide layer on its surface during long-term storage. Additionally, it forms a continuous thermal conductive interface on the surface, which is beneficial for the uniform distribution of heat in the plane direction; on this basis, an island-shaped thermal conductive coating is further formed on the surface of the thin film thermal conductive coating. Its island-shaped structure can penetrate into the nano silver paste during the curing process of the nano silver paste and serve as an anchoring point to enhance the bonding force between the cured nano silver paste and the thermal conductive coating. Additionally, during the curing process of the nano silver paste, the generated shrinkage stress can be transferred to the thin film thermal conductive coating through the island-shaped thermal conductive coating to achieve stress release. At the same time, since both the island-shaped thermal conductive coating and the thin film thermal conductive coating use epoxy resin as the coating, the bonding force between them is strong, and the island-shaped area and the substrate will not fall off due to the transfer of shrinkage stress; more importantly, the presence of the island-shaped coating can avoid the problem of forming bubbles at the interface due to the generation of shrinkage stress during the curing process of the nano silver paste. Due to the reduction of bubbles, the integrity of the thermal conductive interface is improved.

[0017] Furthermore, the thickness of the thin film thermal conductive coating is 8 - 12 μm.

[0018] Furthermore, the No. 1 thermal conductive epoxy resin coating comprises raw materials in the following parts by weight: 100-110 parts of epoxy resin E44, 10-12 parts of amine curing agent, 15-20 parts of monodisperse graphene oxide, 2-4 parts of microcrystalline wax, and 0.3-0.5 part of polysiloxane defoaming agent.

[0019] Furthermore, the amine curing agent is selected from any one of ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, m-phenylenediamine, p-phenylenediamine, and isophorone diamine.

[0020] Furthermore, the particle size distribution range of the monodisperse graphene oxide is 90-110 nm.

[0021] By using monodisperse graphene oxide as the main thermal conductive filler and supplementing a certain amount of microcrystalline wax in the system, among which, graphene oxide as a layered thermal conductive filler will facilitate the uniform transfer of heat in the planar direction of the thin film thermal conductive coating. The presence of microcrystalline wax can facilitate the diffusion and penetration of graphene oxide to the surface of the thin film thermal conductive layer during the curing process of epoxy resin, thereby forming a more complete thermal conductive interface on the surface. Moreover, due to the rich functional groups of graphene oxide, the bonding force between the island-shaped thermal conductive coatings in the thin film thermal conductive layer will be improved, avoiding its shedding; and these rich functional groups will also be beneficial to the wetting and spreading of the nano silver paste on the surface during the heating and curing process, reducing the presence of bubbles.

[0022] Furthermore, the island-shaped thermal conductive coating comprises island-shaped protrusions distributed at intervals, and the distribution density of the island-shaped protrusions is 18-20 pieces / cm 2 ; and the particle height of a single island-shaped protrusion is 20-30 μm.

[0023] Furthermore, the No. 2 thermal conductive epoxy resin coating comprises raw materials in the following parts by weight: 100-110 parts of epoxy resin E44, 10-12 parts of amine curing agent, 20-25 parts of monodisperse spherical nano-aluminum oxide, 4-6 parts of microcrystalline wax, and 0.3-0.5 part of polysiloxane defoaming agent.

[0024] Furthermore, the particle size distribution range of the monodisperse spherical nano-aluminum oxide is 80-120 nm;

[0025] The sphericity of the monodisperse spherical nano-aluminum oxide is 0.88-0.92.

[0026] By using monodisperse spherical nano-aluminum oxide as the thermal conductive filler in the island-shaped thermal conductive coating, the higher sphericity can facilitate the more uniform transfer of heat in all directions inside the system, and the monodisperse particles will make the thermal conductivity between different parts tend to be consistent.

[0027] Furthermore, the surface of the monodisperse spherical nano-aluminum oxide is coated with a silane coupling agent;

[0028] The silane coupling agent is selected from any one of: silane coupling agent KH-540, silane coupling agent KH-550, silane coupling agent KH-560, silane coupling agent KH-570, and silane coupling agent KH-580. Detailed implementation manners

[0029] The following specific examples are used to further illustrate the present invention, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0030] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0031] Example 1

[0032] A DFN substrate made of copper material with a size specification of 2×3 mm is used;

[0033] Pretreatment of the DFN substrate:

[0034] After coating the surface of the DFN frame substrate facing the nano-silver paste with No. 1 thermal conductive epoxy resin coating, it is heated and cured to form a thin film thermal conductive coating with a thickness of 8 μm;

[0035] The No. 1 thermal conductive epoxy resin coating includes the following raw materials in parts by weight: 100 parts of epoxy resin E44, 10 parts of amine curing agent, 15 parts of monodisperse graphene oxide, 2 parts of microcrystalline wax, and 0.3 parts of polysiloxane defoaming agent;

[0036] The amine curing agent is selected from ethylenediamine;

[0037] The particle size distribution range of the monodisperse graphene oxide is 90-110 nm;

[0038] Then, after gravure printing No. 2 thermal conductive epoxy resin coating on the surface of the thin film thermal conductive coating, it is heated and cured to form an island-shaped thermal conductive coating on the surface of the thin film thermal conductive coating. The island-shaped thermal conductive coating is island-shaped protrusions distributed at intervals, and the distribution density of the island-shaped protrusions is 18 pieces / cm 2 ; and the particle height of a single island-shaped protrusion is 20 μm;

[0039] The No. 2 thermal conductive epoxy resin coating includes the following raw materials in parts by weight: 100 parts of epoxy resin E44, 10 parts of amine curing agent, 20 parts of monodisperse spherical nano-aluminum oxide, 4 parts of microcrystalline wax, and 0.3 parts of polysiloxane defoaming agent;

[0040] The particle size distribution range of the monodisperse spherical nano-aluminum oxide is 80-120 nm;

[0041] The sphericity of the monodisperse spherical nano-aluminum oxide is 0.88;

[0042] The surface of the monodisperse spherical nano-aluminum oxide is coated with a silane coupling agent;

[0043] The silane coupling agent is selected from: silane coupling agent KH-540;

[0044] Dicing:

[0045] By means of laser cutting, the chips distributed in a matrix on the wafer are cut and separated into independent single chips;

[0046] Coating nano-silver paste:

[0047] The nano-silver paste is coated between the chip and the pretreated DFN frame substrate, and the coating thickness of the nano-silver paste is controlled to be 40 μm;

[0048] Curing: The nano-silver paste is cured by heat treatment to form an electrical connection;

[0049] Bonding: The bonding area on the chip is connected to the lead frame through bonding aluminum wire / gold wire, so as to realize the connection between the internal function of the chip and the external circuit;

[0050] Encapsulation: The bonded lead frame is encapsulated with an encapsulation material to protect the high-density integrated circuit components;

[0051] Tinning: Make the solder form a continuous metal path to enable the current to pass through smoothly;

[0052] Cutting: The packaged whole (whole board) product is cut and separated into single products to facilitate the transfer of single products in subsequent processes.

[0053] Example 2

[0054] Use a DFN substrate made of copper material, with a size specification of 2×3 mm;

[0055] Pretreatment of the DFN substrate:

[0056] After coating the surface of the DFN frame substrate facing the nano-silver paste with 1# thermally conductive epoxy resin coating, heat it for curing to form a thin film thermally conductive coating with a thickness of 10 μm;

[0057] The 1# thermally conductive epoxy resin coating includes the following raw materials in parts by weight: 105 parts of epoxy resin E44, 11 parts of amine curing agent, 18 parts of monodisperse graphene oxide, 3 parts of microcrystalline wax, and 0.4 part of polysiloxane defoaming agent;

[0058] The amine curing agent is selected from diethylenetriamine;

[0059] The particle size distribution range of the monodisperse graphene oxide is 90 - 110 nm;

[0060] After gravure printing the No. 2 thermal conductive epoxy resin coating on the surface of the thin film thermal conductive coating, heat curing is carried out to form an island-shaped thermal conductive coating on the surface of the thin film thermal conductive coating. The island-shaped thermal conductive coating is island-shaped protrusions distributed at intervals, and the distribution density of the island-shaped protrusions is 19 pieces / cm 2 ; and, the particle height of a single island-shaped protrusion is 25 μm;

[0061] The No. 2 thermal conductive epoxy resin coating comprises raw materials in the following weight parts: 105 parts of epoxy resin E44, 11 parts of amine curing agent, 22 parts of monodisperse spherical nano-alumina, 5 parts of microcrystalline wax, 0.4 part of polysiloxane defoaming agent;

[0062] The particle size distribution range of the monodisperse spherical nano-alumina is 80 - 120 nm;

[0063] The sphericity of the monodisperse spherical nano-alumina is 0.9;

[0064] The surface of the monodisperse spherical nano-alumina is coated with a silane coupling agent;

[0065] The silane coupling agent is selected from: silane coupling agent KH-550;

[0066] Dicing:

[0067] Adopt laser cutting to cut and separate the chips distributed in a matrix on the wafer into independent single chips;

[0068] Coating nano-silver paste:

[0069] Coat the nano-silver paste between the chip and the pretreated DFN frame substrate, and control the coating thickness of the nano-silver paste to be 50 μm;

[0070] Curing: Cure the nano-silver paste by heat treatment to form an electrical connection;

[0071] Bonding: Bond the bonding area on the chip to the lead frame through bonding aluminum wire / gold wire, so as to realize the connection between the internal function of the chip and the external circuit;

[0072] Encapsulation: Encapsulate the bonded lead frame with an encapsulation material to protect the high-density integrated circuit components;

[0073] Tinning: Make the solder form a continuous metal path to enable current to pass through smoothly;

[0074] Cutting: Cut and separate the packaged whole (whole board) product into single products to facilitate the transfer of single products in subsequent processes.

[0075] Example 3

[0076] Use a DFN substrate made of copper material with a size specification of 2×3 mm;

[0077] Pretreatment of the DFN substrate:

[0078] Coat the surface of the DFN frame substrate facing the nano-silver paste with No. 1 thermal conductive epoxy resin coating, and then heat and cure it to form a thin film thermal conductive coating with a thickness of 12 μm;

[0079] The No. 1 thermal conductive epoxy resin coating includes the following raw materials in parts by weight: 110 parts of epoxy resin E44, 12 parts of amine curing agent, 20 parts of monodisperse graphene oxide, 4 parts of microcrystalline wax, and 0.5 part of polysiloxane defoaming agent;

[0080] The amine curing agent is selected from triethylenetetramine;

[0081] The particle size distribution range of the monodisperse graphene oxide is 90 - 110 nm;

[0082] Then, after gravure printing the No. 2 thermal conductive epoxy resin coating on the surface of the thin film thermal conductive coating, heat and cure it to form an island-shaped thermal conductive coating on the surface of the thin film thermal conductive coating. The island-shaped thermal conductive coating is island-shaped protrusions distributed at intervals, and the distribution density of the island-shaped protrusions is 20 pieces / cm 2 ; and the particle height of a single island-shaped protrusion is 30 μm;

[0083] The No. 2 thermal conductive epoxy resin coating includes the following raw materials in parts by weight: 110 parts of epoxy resin E44, 12 parts of amine curing agent, 25 parts of monodisperse spherical nano-aluminum oxide, 6 parts of microcrystalline wax, and 0.5 part of polysiloxane defoaming agent;

[0084] The particle size distribution range of the monodisperse spherical nano-aluminum oxide is 80 - 120 nm;

[0085] The sphericity of the monodisperse spherical nano-aluminum oxide is 0.92;

[0086] The surface of the monodisperse spherical nano-aluminum oxide is coated with a silane coupling agent;

[0087] The silane coupling agent is selected from: silane coupling agent KH-560;

[0088] Dicing:

[0089] Adopt laser cutting to cut and separate the chips distributed in a matrix on the wafer into independent single chips;

[0090] Coat nano-silver paste:

[0091] Apply the nano silver paste between the chip and the pre-treated DFN frame substrate, and control the coating thickness of the nano silver paste to be 60 μm;

[0092] Curing: Cure the nano silver paste by heat treatment to form an electrical connection;

[0093] Bonding: Connect the bonding area on the chip to the lead frame through bonding aluminum wires / gold wires, so as to realize the connection between the internal functions of the chip and the external circuit;

[0094] Encapsulation: Encapsulate the bonded lead frame with an encapsulation material to protect the high-density integrated circuit components;

[0095] Tinification: Make the solder form a continuous metal path to allow current to pass through smoothly;

[0096] Cutting: Cut and separate the packaged whole (whole board) product into single products, which is convenient for the subsequent processes to transfer the single products.

[0097] Example 4

[0098] The difference between this example and Example 1 is that:

[0099] The particle size distribution range of graphene oxide is 60 - 120 nm, and the other conditions remain unchanged.

[0100] Example 5

[0101] The difference between this example and Example 1 is that:

[0102] The sphericity of monodisperse spherical nano-aluminum oxide is 0.8, and the other conditions remain unchanged.

[0103] Example 6

[0104] The difference between this example and Example 1 is that:

[0105] The particle height of a single island-like protrusion is 16 μm, and the other conditions remain unchanged.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 1 is that the DFN substrate is not pre-treated and is directly used, and the other conditions remain unchanged.

[0108] Comparative Example 2

[0109] The difference between this comparative example and Example 1 is that the pre-treatment method of the DFN substrate is different. Specifically, the pre-treatment method of this comparative example is:

[0110] The DFN framework substrate was cleaned 3 times with a baking soda solution with a mass fraction of 8% to remove surface oil stains. Subsequently, it was cleaned 2 times with a sulfuric acid solution with a mass fraction of 10% to remove the surface oxide layer, and then rinsed 2 times with clean water;

[0111] The remaining conditions remained unchanged.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 1 is that the island-shaped thermal conductive coating was not coated, and the remaining conditions remained unchanged.

[0114] The products obtained from the examples and comparative examples were subjected to performance tests. The specific test methods and test results are as follows:

[0115] The products obtained from the above examples or comparative examples were respectively installed and fixed on the PCB board. Subsequently, they were installed in the circuit loop. Under the condition that the ambient temperature was 25°C, a current of 10 mA was applied to the device to make it work continuously for 4 h or 45 d under this condition, and then the work was stopped. The time required for them to cool down to room temperature (25°C) was respectively measured. The detailed test results are shown in Table 1;

[0116]

[0117] It can be seen from the test results in Table 1 that the products obtained by the present invention can effectively improve the thermal conductivity after MOS transistor packaging, enabling the heat generated during operation to dissipate quickly. Moreover, after a long period of continuous operation, the relevant thermal conductivity can still be effectively maintained.

[0118] The above examples are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An efficient high-voltage and high-current MOS transistor packaging process, characterized in that, The specific encapsulation steps include: Dicing: Cutting and separating the chips distributed in a matrix on the wafer into independent single chips; Coating nano silver paste: Coating the nano silver paste between the chip and the pretreated DFN frame substrate; Curing: Curing the nano silver paste by heat treatment to form an electrical connection; Among them, the pretreatment steps of the pretreated DFN frame substrate include: Coating the surface of the DFN frame substrate facing the nano silver paste with 1# thermally conductive epoxy resin coating, and then heating and curing to form a thin film thermally conductive coating; Then, intaglio printing 2# thermally conductive epoxy resin coating on the surface of the thin film thermally conductive coating, and heating and curing to form an island-shaped thermally conductive coating on the surface of the thin film thermally conductive coating.

2. The high-performance high-voltage and high-current MOS transistor packaging process according to claim 1, characterized in that The thickness of the thin film thermally conductive coating is 8 - 12 μm.

3. An efficient high-voltage high-current MOSFET packaging process according to any one of claims 1 or 2, characterized in that The 1# thermally conductive epoxy resin coating comprises the following raw materials in parts by weight: 100 - 110 parts of epoxy resin E44, 10 - 12 parts of amine curing agent, 15 - 20 parts of monodisperse graphene oxide, 2 - 4 parts of microcrystalline wax, 0.3 - 0.5 parts of polysiloxane defoamer.

4. An efficient high-voltage and high-current MOSFET packaging process according to claim 3, characterized in that, The amine curing agent is selected from any one of ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, m-phenylenediamine, p-phenylenediamine, isophorone diamine.

5. An efficient high-voltage and high-current MOSFET packaging process according to claim 3, characterized in that, The particle size distribution range of the monodisperse graphene oxide is 90 - 110 nm.

6. An efficient high-voltage and high-current MOS transistor packaging process according to any one of claims 1 or 2, characterized in that The island-shaped heat-conducting coating includes island-shaped protrusions distributed at intervals, and the distribution density of the island-shaped protrusions is 18-20 pieces / cm 2 ; moreover, the particle height of a single island-shaped protrusion is 20-30 μm.

7. An efficient high-voltage and high-current MOSFET packaging process according to claim 6, characterized in that, The 2# thermally conductive epoxy resin coating comprises the following raw materials in parts by weight: 100 - 110 parts of epoxy resin E44, 10 - 12 parts of amine curing agent, 20 - 25 parts of monodisperse spherical nano-aluminum oxide, 4 - 6 parts of microcrystalline wax, 0.3 - 0.5 parts of polysiloxane defoamer.

8. An efficient high-voltage and high-current MOSFET packaging process according to claim 7, characterized in that, The particle size distribution range of the monodisperse spherical nano-aluminum oxide is 80 - 120 nm; The sphericity of the monodisperse spherical nano-aluminum oxide is 0.88 - 0.

92.

9. An efficient high-voltage and high-current MOS transistor packaging process according to any one of claims 7 or 8, characterized in that The surface of the monodisperse spherical nano-aluminum oxide is coated with a silane coupling agent; The silane coupling agent is selected from any one of silane coupling agent KH-540, silane coupling agent KH-550, silane coupling agent KH-560, silane coupling agent KH-570, silane coupling agent KH-580.

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