Polyamic acid for low-temperature curing power semiconductor packaging and preparation method thereof

Abstract

The present invention discloses a kind of low temperature curing power semiconductor package polyamic acid and preparation method thereof, by the diether dianhydride of polyethylene glycol chain in the middle, the aromatic diamine containing flexible spacer group and bis(3-aminopropyl) end-blocked polydimethylsiloxane (average molecular weight≤3000g / mol) copolymerized in polar aprotic solvent.Preparation process is under high purity inert gas atmosphere, and aromatic diamine and end-blocking agent are dissolved in polar aprotic solvent, and diether dianhydride is added in batches under the conditions of 0-5 DEG C to carry out copolymerization and obtain.The polyamic acid prepared by the present invention greatly reduces its glass transition temperature, makes its highest curing temperature≤220 DEG C, curing time≤4h, imidization degree reaches 100%, and the bonding strength with aluminum nitride substrate is≥15.0MPa, is more than 10 times of common polyimide products, and cross-cut test result reaches 0 level.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid polyimide coating adhesives, and in particular relates to a low-temperature curing polyamic acid for power semiconductor packaging and a preparation method thereof. Background Art

[0002] After thermal imidization, polyamic acid for power semiconductor packaging not only retains the excellent physical and chemical properties inherent in polyimide, but also exhibits high bonding strength to materials such as silicon, aluminum, copper, nickel, ceramics, or aluminum nitride. It can be applied to the surface of power semiconductors as a protective layer, enhancing the device's insulation level. However, currently produced domestically, polyamic acid for power semiconductor packaging has certain shortcomings in terms of adhesion to substrates, compatibility with device manufacturing processes, long-term reliability of device operation, and curing time and energy consumption.

[0003] Chinese patent document CN103865471A provides a method for preparing a polyimide adhesive. The method involves reacting 2,2-bis[4-(4-aminophenoxy)phenyl]propane, diaminodiphenyl ether, and 2,3,3',4'-diphenylether tetracarboxylic dianhydride to form polyamic acid. Polyimide powder is obtained through chemical imidization and pulverization. The curing temperature of this polyimide powder is only 170-200°C, and it is not prone to bubbles or voids in the adhesive layer. However, its bonding strength to substrates such as copper, aluminum, platinum, and stainless steel is relatively average. While it can be initially used and promoted in power semiconductor packaging applications where bonding performance is not critical, it is difficult to achieve application where bonding strength requirements are more stringent.

[0004] Chinese patent document CN102093559A discloses a polyimide electronic packaging material and a synthesis method thereof. The method first comprises dissolving 2,3,3',4'-biphenyltetracarboxylic dianhydride and 2,2'-bis(trifluoromethyl)-4,4-diaminodiphenyl sulfide in an aprotic polar solvent in equal molar ratios to react and synthesize polyamic acid; then, the prepared polyamic acid is placed in a high-temperature oven and imidized according to the following procedure: 80°C / 3h, 150°C / 1h, 180°C / 1h, 250°C / 1h, 300°C / 1h, and 350°C / 15min; and then naturally cooling to obtain a power semiconductor packaging polyimide material. This material has high light transmittance, low water absorption, excellent mechanical properties and high temperature resistance, but its glass transition temperature is generally higher than 300°C. During the power semiconductor packaging process, there may be problems with incomplete thermal imidization, which is poorly compatible with the device manufacturing process, thus affecting the yield and long-term operational reliability of power semiconductor devices. In addition, the entire imidization heating time is ≥7h, which is time-consuming and energy-intensive. Summary of the Invention

[0005] In order to overcome the problems in the prior art, the present invention provides a low-temperature curing polyamic acid for power semiconductor packaging and a preparation method thereof. The prepared polyamic acid has a maximum curing temperature of ≤220°C, a curing time of ≤4h, and a degree of imidization of 100%. It is highly compatible with the manufacturing process of power semiconductor devices. After curing, it has outstanding heat resistance, electrical insulation and substrate adhesion, can achieve good packaging of power semiconductor devices, protect the internal interconnection of the device, and prevent the device from mechanical and chemical damage, thereby improving the long-term operation reliability and stability of the power semiconductor device.

[0006] In order to solve the above technical problems, the technical solutions proposed by the present invention are as follows:

[0007] A low-temperature curing polyamic acid for power semiconductor packaging is prepared by copolymerizing a diether dianhydride with a polyethylene glycol chain in the middle, an aromatic diamine containing a flexible spacer group, and a bis(3-aminopropyl)-terminated polydimethylsiloxane in a polar aprotic solvent. The average molecular weight of the (3-aminopropyl)-terminated polydimethylsiloxane is ≤3000 g / mol. The molar ratio of the total molar amount of the bis(3-aminopropyl)-terminated polydimethylsiloxane and the aromatic diamine containing a flexible spacer group to the diether dianhydride with a polyethylene glycol chain in the middle is 1.00:(0.95-1.1).

[0008] In the present invention, flexible groups are introduced on the polyimide molecular chain to make the compliance of the polyimide molecular chain lower, and the polyimide molecular chain main chain and the end-blocking flexible side chain act together simultaneously, further reducing the glass transition temperature of polyimide while maintaining high insulation. In addition, phenoxy group, siloxanes etc. make material have very strong hydrogen bond interaction, and polyimide has shown higher cohesive energy and interface adhesion energy and increases the free volume of polyimide condensed state structure. Simultaneously control the molecular weight average of (3-aminopropyl) end-blocking polydimethylsiloxane≤3000g / mol, be conducive to the carrying out of reaction, molecular weight is too large, molecular chain is too long, reactive inadequately, polyamic acid resin performance is bad, and molecular chain is easily wound around, and adhesion declines.

[0009] Furthermore, the molar ratio of the total molar amount of the bis(3-aminopropyl)-terminated polydimethylsiloxane and the aromatic diamine containing a flexible spacer group to the molar amount of the diether dianhydride with a polyethylene glycol chain in the middle is preferably 1.00:(0.99-1.0).

[0010] As an optional embodiment, in the polyamic acid provided by the present invention, the molar ratio of the bis(3-aminopropyl)-terminated polydimethylsiloxane to the aromatic diamine containing a flexible spacer group is 1.00:(15.00-20.00).

[0011] In the present invention, controlling the molar ratio of bis(3-aminopropyl)-terminated polydimethylsiloxane to the aromatic diamine containing a flexible spacer group can further improve the product's low-temperature curing and adhesion. Too low a ratio of bis(3-aminopropyl)-terminated polydimethylsiloxane results in a weak effect, while too high a ratio results in excessive reactivity.

[0012] As an optional embodiment, in the polyamic acid provided by the present invention, the flexible spacer group in the aromatic diamine is selected from one of the alkyl groups having 1 to 12 carbon atoms.

[0013] In the present invention, the use of alkyl groups as flexible groups can hinder the orderly stacking and arrangement of conjugated units, improve the flexibility of the molecular chain, and reduce the curing temperature.

[0014] As an optional embodiment, in the polyamic acid provided by the present invention, the diether dianhydride with a polyethylene glycol chain in the middle is selected from one or more of bis(phthalic anhydride) linked by -OCH2CH2O-, bis(phthalic anhydride) linked by -(OCH2CH2O)2-, bis(phthalic anhydride) linked by -(OCH2CH2O)3-, bis(phthalic anhydride) linked by -(OCH2CH2O)4-, bis(phthalic anhydride) linked by -(OCH2CH2O)5-, and bis(phthalic anhydride) linked by -(OCH2CH2O)6-.

[0015] In the present invention, the introduction of polyethylene glycol into the dianhydride can promote the formation of hydrogen bonds with the substrate during the application process, thereby improving the adhesion of the material and lowering the glass transition temperature.

[0016] As an optional embodiment, in the polyamic acid provided by the present invention, the aromatic diamine containing a flexible spacer group is selected from bis(4-aminophenoxy)methane, 1,2-bis(4-aminophenoxy)ethane, 1,2-bis(3-aminophenoxy)ethane, 1,2-bis(4-aminophenoxy)propane, 1,2-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)octane, 1,3-bis(4-aminophenoxy)propane, 1,3-bis(3-aminophenoxy)propane, 2,2-bis(4-aminophenoxymethylene)propane, 2,2-bis(4-aminophenoxymethylene)pentapropane, 2,2-diethyl-1,3-bis(4-aminophenoxy)propane, 1,4-bis( One or more of 1,4-bis(m-aminophenoxy)butane, 1,5-bis(p-aminophenoxy)pentane, 1,5-bis(m-aminophenoxy)pentane, 1,6-bis(p-aminophenoxy)hexane, 1,6-bis(m-aminophenoxy)hexane, 1,8-bis(p-aminophenoxy)octane, 1,8-bis(m-aminophenoxy)octane, 1,9-bis(p-aminophenoxy)nonane, 1,9-bis(m-aminophenoxy)nonane, 1,10-bis(p-aminophenoxy)decane, 1,10-bis(m-aminophenoxy)decane, 1,12-bis(p-aminophenoxy)dodecane and 1,12-bis(m-aminophenoxy)dodecane.

[0017] As an optional embodiment, in the polyamic acid provided by the present invention, the bis(3-aminopropyl)-terminated polydimethylsiloxane is selected from one or more of an average molecular weight of 248 g / mol, an average molecular weight of 1000 g / mol, an average molecular weight of 2500 g / mol, and an average molecular weight of 3000 g / mol.

[0018] The siloxane groups in the bis(3-aminopropyl)-terminated polydimethylsiloxane of the present invention can enhance the adhesion between the material and the substrate, while the bisamino groups can act reactively, thereby enabling the introduction of polyimide main chains and improving the stability of the material.

[0019] As an optional embodiment, in the polyamic acid provided by the present invention, the maximum curing temperature of the polyamic acid is ≤220° C., the curing time is ≤4 h, and the imidization degree reaches 100%.

[0020] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned low-temperature curing polyamic acid for power semiconductor packaging, comprising the following steps:

[0021] S1. In a high-purity inert gas atmosphere, an aromatic diamine containing a flexible spacer group and a bis(3-aminopropyl)-terminated polydimethylsiloxane are dissolved in a polar aprotic solvent.

[0022] S2. The reaction temperature is 0-5° C., and diether dianhydride with a polyethylene glycol chain in the middle is added to the system of step S1 in batches for copolymerization reaction. The reaction time is 6-8 hours to obtain low-temperature curing polyamic acid for power semiconductor packaging.

[0023] As an optional embodiment, in the preparation method provided by the present invention, the polar aprotic solvent is selected from one or more of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0024] As an optional embodiment, in the preparation method provided by the present invention, the added amount of the polar aprotic solvent accounts for 70.0-90.0% of the mass of the polyamic acid for low-temperature curing power semiconductor packaging.

[0025] Furthermore, it is preferably 80.0 to 85.0%.

[0026] As an optional embodiment, in the preparation method provided by the present invention, the total addition amount of the aromatic diamine monomer containing a flexible spacer group and the diether dianhydride monomer with a polyethylene glycol chain in the middle accounts for 10.0 to 30.0% of the mass of the polyamic acid for low-temperature curing power semiconductor packaging.

[0027] Furthermore, it is preferably 15.0 to 20.0%.

[0028] As an optional embodiment, in the preparation method provided by the present invention, the inert gas is selected from one or more of helium, neon, argon, krypton, xenon, radon, nitrogen and carbon dioxide.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The low-temperature curing polyamic acid for power semiconductor packaging of the present invention is copolymerized in a polar aprotic solvent by a diether dianhydride with a polyethylene glycol chain in the middle, an aromatic diamine containing a flexible spacer group, and a bis(3-aminopropyl)-terminated polydimethylsiloxane (average molecular weight ≤ 3000 g / mol). Multiple ether bonds and flexible fatty chain structures are introduced into the main chain structure of the molecule, which gives the polyimide molecular chain higher flexibility, increases the free volume of the polyimide condensed structure, greatly reduces its glass transition temperature, makes its maximum curing temperature ≤ 220°C, and the curing time ≤ 4h. The imidization degree reaches 100%, which is highly compatible with the manufacturing process of power semiconductor devices.

[0031] (2) The molecular backbone of the polyamic acid for low-temperature curing power semiconductor packaging of the present invention contains a large number of phenoxy and siloxane structures, which enables it to have high bonding strength with substrate materials such as silicon, aluminum, copper, nickel, ceramics or aluminum nitride at the molecular level. The bonding strength with the aluminum nitride substrate is ≥15.0 MPa, which is more than 10 times that of ordinary polyimide products. The cross-grid test result reaches level 0, indicating ultra-high bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 Thermal imidization process of the low-temperature curing polyamic acid for power semiconductor packaging prepared in Examples 1-8;

[0034] Figure 2 Thermal imidization procedure of PMDA / ODA polyamic acid prepared in Comparative Example 1;

[0035] Figure 3 These are infrared curves of the low-temperature curing polyamic acid for power semiconductor packaging prepared in Example 1 and the polyamic acid prepared in Comparative Example 1 after thermal imidization. DETAILED DESCRIPTION

[0036] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0038] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0039] Example 1

[0040] A method for preparing a low-temperature curing polyamic acid for power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (34.54 g, 0.15 mol) of bis(4-aminophenoxy)methane and (2.48 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (molecular weight of 248 g / mol) into a 1000 ml three-necked flask, and using (443.87 g) of N-methylpyrrolidone (solid (2) adding (41.31 g, 0.16 mol) of bis(phthalic anhydride) linked by -OCH2CH2O- to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) at a reaction temperature of 0-5°C to carry out copolymerization reaction, with an addition interval of 0.8 h and a total reaction time of 8 h to obtain a low-temperature curing polyamic acid for power semiconductor packaging.

[0041] Example 2

[0042] A method for preparing a low-temperature curing polyamic acid for power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (36.64 g, 0.15 mol) of 1,2-bis(4-aminophenoxy)ethane and (2.48 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (molecular weight of 248 g / mol) into a 1000 ml three-necked flask, and using (455.77 g) of N-methylpyrrolidone to prepare a low-temperature curing polyamic acid for power semiconductor packaging. (solid content is 15%) to completely dissolve it; (2) the reaction temperature is 0-5°C, and 41.31g, 0.16mol) of bis(phthalic anhydride) linked by -OCH2CH2O- is added to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) for copolymerization reaction. The addition interval time is 0.8h and the overall reaction time is 8h to obtain low-temperature curing polyamic acid for power semiconductor packaging.

[0043] Example 3

[0044] A method for preparing a low-temperature curing polyamic acid for power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (49.27 g, 0.15 mol) of 1,8-bis(p-aminophenoxy)octane and (2.48 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (molecular weight of 248 g / mol) into a 1000 ml three-necked flask, and using (527.34 g) of N-methylpyrrolidone to prepare a low-temperature curing polyamic acid for power semiconductor packaging. (solid content is 15%) to completely dissolve it; (2) the reaction temperature is 0-5°C, and 41.31g, 0.16mol) of bis(phthalic anhydride) linked by -OCH2CH2O- is added to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) for copolymerization reaction. The addition interval time is 0.8h and the overall reaction time is 8h to obtain low-temperature curing polyamic acid for power semiconductor packaging.

[0045] Example 4

[0046] A method for preparing a low-temperature curing polyamic acid for power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (57.68 g, 0.15 mol) of 1,12-bis(m-aminophenoxy)dodecane and (2.48 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (molecular weight 248 g / mol) into a 1000 ml three-necked flask, and then using (575.00 g) of N-methylpyrrolidone to prepare a low-temperature curing polyamic acid for power semiconductor packaging. (2) adding (41.31 g, 0.16 mol) of bis(phthalic anhydride) linked by -OCH2CH2O- to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) at a reaction temperature of 0-5°C to carry out copolymerization reaction, with an addition interval of 0.8 h and a total reaction time of 8 h to obtain polyamic acid for low-temperature curing power semiconductor packaging.

[0047] Example 5

[0048] A method for preparing a polyamic acid for low-temperature curing power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (57.68 g, 0.15 mol) of 1,12-bis(m-aminophenoxy)dodecane and (2.48 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (molecular weight 248 g / mol) into a 1000 ml three-necked flask, and using (526.49 g) of N-methylpyrrolidone ( (2) adding (55.41 g, 0.16 mol) of bis(phthalic anhydride) linked by -(OCH2CH2O)3- to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) at a reaction temperature of 0-5°C to carry out copolymerization reaction, with an addition interval of 0.8 h and a total reaction time of 8 h to obtain a low-temperature curing polyamic acid for power semiconductor packaging.

[0049] Example 6

[0050] A method for preparing a polyamic acid for low-temperature curing power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (69.22 g, 0.18 mol) of 1,12-bis(m-aminophenoxy)dodecane and (2.48 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (molecular weight 248 g / mol) into a 2000 ml three-necked flask, and using (650.40 g) of N-methylpyrrolidone ( (2) adding (90.90 g, 0.19 mol) of bis(phthalic anhydride) linked by -(OCH2CH2O)6- to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) at a reaction temperature of 0-5°C to carry out copolymerization reaction, with an addition interval of 0.8 h and a total reaction time of 8 h to obtain a low-temperature curing polyamic acid for power semiconductor packaging.

[0051] Example 7

[0052] A method for preparing a low-temperature curing polyamic acid for power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (73.07 g, 0.19 mol) of 1,12-bis(m-aminophenoxy)dodecane and (10 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (average molecular weight of 1000 g / mol) into a 2000 ml three-necked flask, and using (715.04 g) of N-methylpyrrolidone to prepare a low-temperature curing polyamic acid for power semiconductor packaging. (solid content is 20%) to completely dissolve it; (2) the reaction temperature is 0-5°C, and 95.69g, 0.20mol) of bis(phthalic anhydride) linked by -(OCH2CH2O)6- is added to the system after step (1) in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) for copolymerization reaction. The addition interval time is 0.8h and the overall reaction time is 8h to obtain low-temperature curing polyamic acid for power semiconductor packaging.

[0053] Example 8

[0054] A method for preparing a polyamic acid for low-temperature curing power semiconductor packaging comprises the following steps: (1) in a high-purity argon gas atmosphere, adding (76.91 g, 0.20 mol) of 1,12-bis(m-aminophenoxy)dodecane and (30 g, 0.01 mol) of bis(3-aminopropyl)-terminated polydimethylsiloxane (average molecular weight of 3000 g / mol) into a 2000 ml three-necked flask, and using (829.52 g) of N-methylpyrrolidone ( (2) adding (100.47 g, 0.21 mol) of bis(phthalic anhydride) linked by -(OCH2CH2O)6- in 7 batches (60%, 30%, 8%, 1%, 0.5%, 0.3%, 0.1%) to the system after step (1) at a reaction temperature of 0-5°C for copolymerization, with a feeding interval of 0.8 h and a total reaction time of 8 h to obtain a low-temperature curing polyamic acid for power semiconductor packaging.

[0055] Comparative Example 1

[0056] A preparation method of PMDA / ODA polyamic acid resin comprises the following steps:

[0057] (1) Under nitrogen atmosphere, 0.10 mol (20.02 g) of ODA (4,4'-diaminodiphenyl ether) was dissolved in 237.04 g of N-methylpyrrolidone.

[0058] (2) The reaction temperature was 5° C., and 0.10 mol (21.81 g) of PMDA (pyromellitic dianhydride) was added to the system after step (1) for 8 h to obtain PMDA / ODA polyamic acid.

[0059] Comparative Example 2

[0060] Compared with Example 1, only 0.15 mol of bis(4-aminophenoxy)methane containing a spacer group was replaced by 0.15 mol of p-phenylenediamine.

[0061] Comparative Example 3

[0062] Compared with Example 1, only 0.16 mol of bis(phthalic anhydride) linked by -(OCH2CH2O)3- was replaced by 0.16 mol of pyromellitic dianhydride.

[0063] The viscosity of the polyamic acid for low-temperature curing power semiconductor encapsulation prepared in Examples 1-8 and the polyamic acid prepared in Comparative Examples 1-3 was tested in accordance with GB / T 2794-1995. The results are shown in Table 1. As shown in Table 1, the polyamic acid for low-temperature curing power semiconductor encapsulation prepared in the present invention has a suitable viscosity and good fluidity. When dispensing or coating on substrate materials such as silicon, aluminum, copper, nickel, ceramic, or aluminum nitride, it is not prone to bubble formation and has good leveling properties.

[0064] Table 1: Polyamic acid viscosity test results

[0065]

[0066] The thermal imidization process of the polyamic acid for low temperature curing power semiconductor packaging prepared in the above examples 1-8 is as follows: Figure 1 As shown, the thermal imidization procedure of PMDA / ODA polyamic acid prepared in Comparative Example 1 is as follows Figure 2 As shown, Figure 3 The infrared curves of the polyamic acid prepared in Comparative Example 1 after thermal imidization are shown in FIG. Figure 3 It can be seen that under the conditions of a maximum curing temperature of 220°C and a curing time of 3.5h, the degree of imidization of low-temperature curing polyamic acid for power semiconductor packaging reaches 100%, while the infrared curve of ordinary polyamic acid still contains -NHCO- bonds, and complete imidization is not achieved.

[0067] The curing parameters of the low-temperature curing polyamic acid for power semiconductor packaging prepared in Examples 1-8 and the polyamic acid prepared in Comparative Examples 1-3, and the relevant performance data of the polyimide materials obtained after curing are shown in Table 2.

[0068] Glass transition temperature (T g ) Tested in accordance with HB 7655-1999 standard.

[0069] The insulation strength is tested in accordance with GB / T 1408.1-2016.

[0070] The bonding strength is tested according to GB / T 5210-2006 standard.

[0071] The cross-cut test is carried out in accordance with GB / T9286-2021 standard.

[0072] Table 2: Curing parameters of polyamic acid and relevant performance data of polyimide materials obtained after curing

[0073]

[0074] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A low-temperature curing polyamic acid for power semiconductor packaging, characterized in that: The invention is prepared by copolymerizing a diether dianhydride with a polyethylene glycol chain in the middle, an aromatic diamine containing a flexible spacer group, and a bis(3-aminopropyl)-terminated polydimethylsiloxane in a polar aprotic solvent. The average molecular weight of the (3-aminopropyl)-terminated polydimethylsiloxane is ≤3000 g / mol. The molar ratio of the total molar amount of the bis(3-aminopropyl)-terminated polydimethylsiloxane and the aromatic diamine containing a flexible spacer group to the diether dianhydride with a polyethylene glycol chain in the middle is 1.00:(0.95-1.00). The molar ratio of the bis(3-aminopropyl)-terminated polydimethylsiloxane to the aromatic diamine containing a flexible spacer group is 1.00:(15.00-20.00); The flexible spacer group in the aromatic diamine is selected from an alkyl group having 1 to 12 carbon atoms; The diether dianhydride with a polyethylene glycol chain in the middle is selected from one or more of bis(phthalic anhydride) linked by -OCH2CH2-, bis(phthalic anhydride) linked by -(OCH2CH2)2-, bis(phthalic anhydride) linked by -(OCH2CH2)3-, bis(phthalic anhydride) linked by -(OCH2CH2)4-, bis(phthalic anhydride) linked by -(OCH2CH2)5-, and bis(phthalic anhydride) linked by -(OCH2CH2)6-.

2. The low-temperature curing polyamic acid for power semiconductor packaging according to claim 1, characterized in that: The aromatic diamine containing a flexible spacer group is selected from bis(4-aminophenoxy)methane, 1,2-bis(4-aminophenoxy)ethane, 1,2-bis(3-aminophenoxy)ethane, 1,2-bis(4-aminophenoxy)propane, 1,2-bis(4-aminophenoxy)pentane, 1,2-bis(4-aminophenoxy)octane, 1,3-bis(4-aminophenoxy)propane, 1,3-bis(3-aminophenoxy)propane, 2,2-bis(4-aminophenoxymethylene)propane, 2,2-diethyl-1,3-bis(4-aminophenoxy)propane, 1,4-bis(p-aminophenoxy)butane, 1,4-bis(m-aminophenoxy) One or more of the group consisting of 1,5-bis(p-aminophenoxy)pentane, 1,5-bis(m-aminophenoxy)pentane, 1,6-bis(p-aminophenoxy)hexane, 1,6-bis(m-aminophenoxy)hexane, 1,8-bis(p-aminophenoxy)octane, 1,8-bis(m-aminophenoxy)octane, 1,9-bis(p-aminophenoxy)nonane, 1,9-bis(m-aminophenoxy)nonane, 1,10-bis(p-aminophenoxy)decane, 1,10-bis(m-aminophenoxy)decane, 1,12-bis(p-aminophenoxy)dodecane and 1,12-bis(m-aminophenoxy)dodecane.

3. The low-temperature curing polyamic acid for power semiconductor packaging according to claim 1, characterized in that: The bis(3-aminopropyl)-terminated polydimethylsiloxane is selected from one or more of the group consisting of an average molecular weight of 248 g / mol, an average molecular weight of 1000 g / mol, an average molecular weight of 2500 g / mol, and an average molecular weight of 3000 g / mol.

4. The low-temperature curing polyamic acid for power semiconductor packaging according to claim 1, characterized in that The curing temperature of the polyamic acid is ≤220° C., the curing time is ≤4 hours, and the imidization degree reaches 100%.

5. The method for preparing the low-temperature curing polyamic acid for power semiconductor packaging according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Under a high-purity inert gas atmosphere, an aromatic diamine containing a flexible spacer group and bis(3-aminopropyl)-terminated polydimethylsiloxane are dissolved in a polar aprotic solvent; S2. The reaction temperature is 0-5° C., and diether dianhydride with a polyethylene glycol chain in the middle is added to the system of step S1 in batches for copolymerization reaction. The reaction time is 6-8 hours to obtain low-temperature curing polyamic acid for power semiconductor packaging.

6. The method for preparing the low-temperature curing polyamic acid for power semiconductor packaging according to claim 5, characterized in that: The polar aprotic solvent is selected from one or more of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide, and the added amount of the polar aprotic solvent accounts for 70.0~90.0% of the mass of the polyamic acid for low-temperature curing power semiconductor packaging; the total added amount of the aromatic diamine monomer containing a flexible spacer group and the diether dianhydride monomer with a polyethylene glycol chain in the middle accounts for 10.0~30.0% of the mass of the polyamic acid for low-temperature curing power semiconductor packaging.

7. The method for preparing the low-temperature curing polyamic acid for power semiconductor packaging according to claim 5, characterized in that: The inert gas is selected from one or more of helium, neon, argon, krypton, xenon, radon and nitrogen.

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