A polyimide adhesive, its preparation method, a heat-resistant tape, its preparation method and applications

Abstract

The present invention discloses a polyimide adhesive, a preparation method thereof, a heat-resistant tape, a preparation method thereof and an application, belonging to the technical field of polyimide adhesives. The polyimide adhesive is prepared from a diamine monomer and a dianhydride monomer with polyethylene glycol side chains through esterification, hydrogenation and polymerization reactions; it is dissolved in an organic solvent and then coated on a film substrate, and a heat-resistant tape is obtained after drying; by utilizing the adhesiveness of the PEG side chains and the high-temperature stability of the polyimide main chain, the tape exhibits excellent bonding performance at high temperatures and has peelability, and is suitable for QFN packaging of materials such as nickel-palladium-gold, and is also suitable for bonding of dielectric layers, multi-chip modules and integrated circuit chips in the microelectronics industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer adhesive materials, and particularly relates to a polyimide adhesive, a preparation method thereof, a heat-resistant tape, a preparation method thereof, and an application thereof. Background Art

[0002] As the cornerstone of the development of the information society, the semiconductor chip packaging industry is not only an important driving force for promoting high-quality and sustainable economic growth, but also a key barrier to ensuring national security. QFN packaging, full name Quad Flat No-leads Package, that is, quad flat no-lead package, is a commonly used package type in surface mount technology. Due to its small size, light weight, excellent thermal and electrical properties and other characteristics, QFN packaging is widely used in various fields.

[0003] The process steps of QFN packaging are as follows: attaching a high-temperature tape to the back of the lead frame, bonding the chip to the lead frame, curing the silver paste, plasma cleaning, wire bonding, plastic encapsulation, removing the high-temperature tape, post-curing, printing marks, cutting and forming, etc. Among them, the high-temperature tape is used to fix the lead frame and prevent the plastic encapsulation material from leaking, and it is required to have high temperature resistance, high flatness, no residual glue, etc.

[0004] Polyimide adhesives are commonly used binder raw materials for heat-resistant tapes. However, conventional polyimide resins have poor solubility, which increases the difficulty of their processing and limits the possibility of their wide industrial application. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a polyimide adhesive and a preparation method thereof. By introducing polyethylene glycol into diamine monomers, a polyamic acid solution is obtained by polymerization with dianhydride monomers, and a soluble and fusible polyimide adhesive is prepared by chemical imidization. It has good solubility in organic solvents and is convenient for dilution and use. At the same time, the adhesive has good flexibility and is suitable for applications such as dielectric layers, multi-chip modules, and QFN packaging of integrated circuit chips in the microelectronics industry.

[0006] The present invention also provides a heat-resistant tape, which uses the polyimide adhesive described in the present invention as the raw material for the adhesive layer. The main chain of the polyimide adhesive is a rigid structure. Such a rigid structure improves the thermal stability of the polyethylene glycol side chain, and utilizes the high-temperature adhesion of polyethylene glycol to achieve the bonding performance of the tape at high temperatures. It has excellent stability and durability in high-temperature environments and has the property of being re-peelable after bonding.

[0007] The technical solutions adopted by the present invention are as follows:

[0008] The present invention provides a polyimide adhesive, and the structural formula of the polyimide is:

[0009] Among them, B in the structural formula represents n≥5, 5≤x≤20.

[0010] The present invention also provides a preparation method of the polyimide adhesive, and the preparation method includes the following steps:

[0011] (1) Carry out an esterification reaction on polyethylene glycol monomethyl ether and 3,5-bis(4-nitrophenoxy)benzoic acid to obtain an esterification product;

[0012] (2) Carry out a hydrogenation reaction on the esterification product obtained in step (1) to obtain a hydrogenation product;

[0013] (3) Polymerize the hydrogenation product and a dianhydride monomer under the catalysis of isoquinoline and acetic anhydride to obtain a polyamide-imide solution, add the polyamide-imide solution to methanol, and after filtration, washing, and drying, obtain polyimide powder;

[0014] (4) Dissolve the polyimide powder in an organic solvent to make its solid content 10%-20%, and thus obtain the polyimide adhesive;

[0015] In step (3), the dianhydride monomer is one of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and pyromellitic dianhydride.

[0016] The preparation method specifically includes the following steps:

[0017] (1) Dissolve polyethylene glycol monomethyl ether, 3,5-bis(4-nitrophenoxy)benzoic acid, EDCI, and DMAP in an organic solvent, react at room temperature for 20-24 h under the protection of an inert gas, and after post-treatment, obtain an esterification product;

[0018] (2) Dissolve the esterification product obtained in step (1) in an alcohol solvent, add palladium-carbon, stir and react in a hydrogen atmosphere for 1.5-2.5 h, and after post-treatment, obtain a hydrogenation product;

[0019] (3) Dissolve the hydrogenation product in an organic solvent, under the protection of an inert gas and in an ice bath, add a dianhydride monomer, when the reaction solution is a yellow transparent viscous liquid, add isoquinoline and acetic anhydride, stir and react for 10-12 h to obtain a polyamide-imide solution; add the polyamide-imide solution to methanol, and after filtration, washing, and drying, obtain polyimide powder;

[0020] (4) Dissolve the polyimide powder in an organic solvent to make its solid content 10%-20%, and thus obtain the polyimide adhesive.

[0021] In step (1), the molar ratio of polyethylene glycol monomethyl ether, 3,5-bis(4-nitrophenoxy)benzoic acid, EDCI, and DMAP is 1:1.3 - 1.5:1.8 - 2.2:0.3 - 0.7.

[0022] In step (1), the organic solvent is dichloromethane or tetrahydrofuran; the concentration of 3,5-bis(4-nitrophenoxy)benzoic acid in the organic solvent is 0.05 - 0.1 M.

[0023] In step (2), the mass ratio of the esterification product to palladium-carbon is 8 - 12:1.

[0024] In step (2), the alcohol solvent is absolute ethanol or absolute methanol.

[0025] In step (3), the molar ratio of the hydrogenation product to the dianhydride monomer is 1:0.90 - 1.05.

[0026] In step (3), the molar ratio of acetic anhydride, isoquinoline, and the dianhydride monomer is 1 - 2.5:0.5 - 1.25:1.

[0027] In step (3), the organic solvent is one of N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF).

[0028] In step (4), the organic solvent is any one or more of DMF, DMAC, and NMP.

[0029] The present invention also provides a heat-resistant tape, and the heat-resistant tape uses the polyimide adhesive of the present invention as the raw material for the adhesive layer.

[0030] The present invention also provides a preparation method of the heat-resistant tape, and the preparation method includes the following steps: coating the polyimide adhesive of the present invention on a thin film substrate, and then drying.

[0031] Further, the thin film substrate is a thermosetting polyimide thin film substrate, and other heat-resistant thin film substrates can also be selected.

[0032] The present invention also provides an application of the heat-resistant tape in QFN packaging.

[0033] The polyimide adhesive provided by the present invention prepares a high-temperature-resistant polyimide adhesive by introducing a polyethylene glycol (PEG) side chain into the polyimide polymer and combining the high heat resistance of the polyimide main chain with the thermal adhesiveness of PEG. In its structure, the thermal stability of PEG is improved through the imide ring of the main chain, making it suitable for QFN packaging. The polyimide tape can be applied to the bonding and peeling of nickel-palladium-gold lead frames, laying a solid foundation for domestic breakthroughs.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. Uniform PEG distribution: By introducing PEG onto the diamine monomer and then polymerizing with commercial dianhydride to prepare the polyimide adhesive, each repeating unit on each polyimide molecular chain contains a PEG molecular chain, resulting in good high-temperature adhesion.

[0036] 2. Optimized chemical composition without external doping: Different from the traditional method of adding external materials to the polyimide matrix to assist in improving adhesion, the present invention synthesizes a polyimide adhesive with PEG-containing intrinsic side chains, avoiding the problems of dispersion and compatibility of external materials.

[0037] 3. Adjustable main chain structure of polyimide and molecular weight of side chain PEG, enabling convenient adjustment of the bonding strength of the adhesive. Description of the Drawings

[0038] Figure 1 1H NMR spectrum of the hydrogenated product prepared in step (2) of Example 1;

[0039] Figure 2 1H NMR spectrum of the polyimide adhesive in Example 1;

[0040] Figure 3 GPC chart of the polyimide adhesive in Example 1;

[0041] Figure 4 SEM morphology of the tape adhesive layer in Example 1;

[0042] Figure 5 Bonding (left) and peeling (right) test results of the polyamideimide in Example 1;

[0043] Figure 6 1H NMR spectrum of the polyimide adhesive in Example 2;

[0044] Figure 7 GPC chart of the polyimide adhesive in Example 2;

[0045] Figure 8 1H NMR spectrum of the polyimide adhesive in Example 3;

[0046] Figure 9 GPC chart of the polyimide adhesive in Example 3. Detailed Embodiments

[0047] The present invention will be described in detail below with reference to the embodiments.

[0048] Example 1

[0049] A method for preparing a polyimide adhesive, the preparation process is as follows:

[0050]

[0051] The preparation steps are as follows:

[0052] (1) 5.74 g (16.41 mmol) of polyethylene glycol monomethyl ether with a number average molecular weight of 350, 5 g (12.62 mmol) of 3-5-bis(4-nitrophenoxy)benzoic acid, 4.84 g (25.24 mmol) of EDCI, and 0.77 g (6.31 mmol) of DMAP were dissolved in 150 mL of anhydrous dichloromethane and reacted for 24 h under a nitrogen atmosphere. Subsequently, the solution was concentrated and separated by column chromatography. The eluent was a DCM:MeOH mixed solution with a volume ratio of 20:1. The product solution was collected and concentrated to dryness to obtain a slightly yellow oily esterification product.

[0053] (2) 7.0 g of the esterification product obtained in step (1) was weighed and dissolved in 70 mL of anhydrous ethanol, and 700 mg of 10% palladium carbon was added. The mixture was stirred and reacted in a hydrogen atmosphere at 25° C. for 2 h. After the reaction was completed, the mixture was filtered, concentrated, and dried to obtain a hydrogenated product, i.e., a diamine monomer. Its magnetic hydrogen spectrum is as follows: Figure 1 shown.

[0054] (3) 6.5 g (9.72 mmol) of the hydrogenated product was dissolved in 43 mL of N,N-dimethylacetamide, and 2.86 g (9.72 mmol) of biphenyltetracarboxylic dianhydride was added thereto under the protection of nitrogen and in an ice bath to obtain a polyamide imide precursor polyamic acid solution; 1.98 g (19.44 mmol) of acetic anhydride and 1.25 g (9.72 mmol) of isoquinoline were added, and the reaction was carried out at room temperature for 12 h to obtain a polyimide solution, which was then precipitated in 400 mL of cold methanol, filtered and dried to obtain a polyimide adhesive. The H NMR spectrum showed that Figure 2 shown.

[0055] (4) Weigh 2.0 g of polyimide adhesive, add 10 mL of DMF to fully dissolve it, and apply it on a Kapton yellow film with a coating thickness of 1. After drying the solvent at 130° C. for 5 min, a polyimide tape is obtained.

[0056] The prepared polyimide tape was hot pressed on the nickel-palladium-gold substrate at 240°C and a pressure of 5 MPa. The tape can be well attached to the nickel-palladium-gold surface, such as Figure 5 In the left picture, the tape can be easily peeled off from the NiPdAu substrate after cooling. Figure 5 As shown in the right picture, there is no residual glue after peeling.

[0057] Figure 4SEM image of the surface morphology of the tape adhesive layer. As can be seen from the figure, the polyimide adhesive prepared in this example has good film-forming properties.

[0058] The gel permeation chromatography (GPC) diagram of the polyamide-imide solution obtained in step (3) of this example is as Figure 3 shown, with a molecular weight Mn = 23000 and a polymer dispersity index PDI = 1.86.

[0059] Example 2

[0060] A preparation method of a polyimide adhesive, and the preparation process is as follows:

[0061]

[0062] The preparation steps are as follows:

[0063] (1) Dissolve 7.8 g (11.66 mmol) of the hydrogenated product in Example 1 in 65 mL of N,N-dimethylacetamide. Under the protection of nitrogen and in an ice bath, add 5.18 g (11.66 mmol) of 6FDA to obtain a polyamide-acid solution of the polyamide-imide precursor; add 2.37 g (23.32 mmol) of acetic anhydride and 1.5 g (11.66 mmol) of isoquinoline, and react at room temperature for 12 h to obtain a polyimide solution. Subsequently, precipitate it in 600 mL of cold methanol, filter by suction and dry to obtain a polyimide adhesive, and the proton nuclear magnetic resonance spectrum is as Figure 6 shown.

[0064] (2) Weigh 2.0 g of the polyimide adhesive, add 10 mL of DMF and dissolve it fully, then coat it on a Kapton yellow film, with a coating thickness of 1. After drying the solvent at 130 °C for 5 min, a polyimide tape is obtained.

[0065] Press the prepared polyimide tape onto a nickel-palladium-gold substrate at 240 °C and a pressure of 5 MPa. The tape can adhere well to the nickel-palladium-gold surface, and after cooling, the tape can be peeled off from the nickel-palladium-gold substrate well, and there is no residual glue after peeling.

[0066] The gel permeation chromatography (GPC) diagram of the polyamide-imide solution obtained in step (1) of this example is as Figure 7 shown, with a molecular weight Mn = 24000 and a polymer dispersity index PDI = 1.78.

[0067] Example 3

[0068] A preparation method of a polyimide adhesive, and the preparation process is as follows:

[0069]

[0070] The preparation steps are as follows:

[0071] (1) 9.02 g (16.41 mmol) of polyethylene glycol monomethyl ether with a number average molecular weight of 550, 5 g (12.62 mmol) of 3-5-bis(4-nitrophenoxy)benzoic acid, 4.84 g (25.24 mmol) of EDCI, and 0.77 g (6.31 mmol) of DMAP were dissolved in 180 mL of anhydrous dichloromethane and reacted for 24 h under nitrogen atmosphere. Subsequently, the solution was concentrated and separated by column chromatography. The eluent was a DCM:MeOH mixed solution with a volume ratio of 15:1. The product solution was collected and concentrated to dryness to obtain a slightly yellow oily esterification product.

[0072] (2) Weigh 9.0 g of the esterification product obtained in step (1) and dissolve it in 80 mL of anhydrous ethanol, add 900 mg of 10% palladium carbon, and stir the mixture in a hydrogen atmosphere at 25° C. for 2 h. After the reaction is completed, filter, concentrate, and dry to obtain a hydrogenated product, i.e., a diamine monomer.

[0073] (3) 8.43 g (9.72 mmol) of diamine monomer was dissolved in 56 mL of N,N-dimethylacetamide, and 4.32 g (9.72 mmol) of 6FDA was added thereto in an ice bath under the protection of nitrogen to obtain a polyamide imide precursor polyamic acid solution; 1.98 g (19.44 mmol) of acetic anhydride and 1.25 g (9.72 mmol) of isoquinoline were added, and the mixture was reacted at room temperature for 12 h to obtain a polyimide solution, which was then precipitated in 560 mL of cold methanol, filtered and dried to obtain a polyimide adhesive. The H NMR spectrum showed that Figure 8 shown.

[0074] (4) Weigh 2.0 g of polyimide adhesive, add 10 mL of DMF to fully dissolve it, and apply it on a Kapton yellow film with a coating thickness of 1 um. After drying the solvent at 130° C. for 5 min, a polyimide tape is obtained.

[0075] The gel permeation chromatography (GPC) analysis of the polyamide imide solution obtained in step (3) of this embodiment is as follows: Figure 9 As shown, its molecular weight Mn = 29000, and polymer dispersibility index PDI = 2.19.

[0076] The prepared polyimide tape was hot pressed on a nickel-palladium-gold substrate at 240°C and a pressure of 5MPa. The tape could be well adhered to the nickel-palladium-gold surface. After cooling, the tape could be well peeled off from the nickel-palladium-gold substrate without any residual adhesive.

[0077] Comparative Example 1

[0078] Other conditions are the same as in Example 1, except that the polyethylene glycol monomethyl ether with a number-average molecular weight of 350 is replaced with an equimolar amount of polyethylene glycol monomethyl ether with a number-average molecular weight of 1800.

[0079] Weigh 2.0 g of the polyimide adhesive prepared in this comparative example, add 10 mL of DMF and dissolve it thoroughly. Then coat it on the Kapton yellow film with a coating thickness of 1 μm. After drying the solvent at 130 °C for 5 min, a polyimide tape is obtained.

[0080] The polyimide tape is hot-pressed onto the nickel-palladium-gold substrate at 240 °C and a pressure of 5 MPa. The tape can adhere well to the surface of the nickel-palladium-gold. After cooling, although the tape can also be peeled off from the nickel-palladium-gold substrate, there will be residual glue after peeling. The residual glue rate is shown in Table 1.

[0081] Refer to Method 1 in GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tape" to test the peel force of the polyimide tapes prepared in the above examples. Different from Method 1 in GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tape", stainless steel is replaced with a nickel-palladium-gold substrate. The test results are shown in the peel force data in Table 1.

[0082] Table 1

[0083]

[0084] As can be seen from Table 1, after the glue solutions in Examples 1-3 are coated into films, the film-forming properties are all very good, and the adhesiveness after hot pressing is also very good. In Comparative Example 1, due to the longer PEG chain segment, although its adhesiveness is better, there is a certain amount of residual glue after peeling.

[0085] The above detailed description of a polyimide adhesive and its preparation method, heat-resistant tape and its preparation method and application with reference to the examples is illustrative rather than restrictive. Several examples can be listed within the defined scope. Therefore, changes and modifications without departing from the general concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A polyimide adhesive, characterized in that: The structural formula of polyimide is: Among them, B in the structural formula represents n≥5, 5≤x≤20.

2. The method for preparing a polyimide adhesive according to claim 1, wherein: The preparation method comprises the following steps: (1) subjecting polyethylene glycol monomethyl ether to an esterification reaction with 3-5-bis(4-nitrophenoxy)benzoic acid to obtain an esterification product; (2) subjecting the esterification product obtained in step (1) to a hydrogenation reaction to obtain a hydrogenated product; (3) polymerizing the hydrogenated product and the dianhydride monomer under the catalytic action of isoquinoline and acetic anhydride to obtain a polyamide imide solution, adding the polyamide imide solution to methanol, filtering, washing, and drying to obtain a polyimide powder; (4) dissolving the polyimide powder in an organic solvent so that the solid content is 10%-20%, thereby obtaining a polyimide adhesive; In step (3), the dianhydride monomer is one of 4,4′-(hexafluoroisopropylene) diphthalic anhydride, 3,3′,4,4′-biphenyltetracarboxylic anhydride and pyromellitic anhydride.

3. The preparation method according to claim 2, characterized in that: The preparation method comprises the following steps: (1) dissolving polyethylene glycol monomethyl ether, 3-5-bis(4-nitrophenoxy)benzoic acid, EDCI and DMAP in an organic solvent, reacting at room temperature for 20 to 24 hours under the protection of an inert gas, and post-treating to obtain an esterification product; (2) dissolving the esterification product obtained in step (1) in an alcohol solvent, adding palladium carbon, stirring and reacting in a hydrogen atmosphere for 1.5 to 2.5 hours, and post-treating to obtain a hydrogenation product; (3) dissolving the hydrogenation product in an organic solvent, adding a dianhydride monomer under the protection of an inert gas and in an ice bath, and when the reaction solution is a yellow, transparent, viscous liquid, adding isoquinoline and acetic anhydride, stirring and reacting for 10 to 12 hours to obtain a polyamide imide solution; adding the polyamide imide solution to methanol, filtering, washing, and drying to obtain a polyimide powder; (4) Dissolving the polyimide powder in an organic solvent so that its solid content is 10%-20%, thereby obtaining a polyimide adhesive.

4. The preparation method according to claim 3, characterized in that: In step (1), the molar ratio of polyethylene glycol monomethyl ether, 3-5-bis(4-nitrophenoxy)benzoic acid, EDCI and DMAP is 1:1.3-1.5:1.8-2.2:0.3-0.

7.

5. The preparation method according to claim 3, characterized in that: In step (2), the mass ratio of the esterification product to palladium carbon is 8 to 12:

1.

6. The preparation method according to claim 3, characterized in that: In step (1), the organic solvent is dichloromethane or tetrahydrofuran; the concentration of 3-5-bis(4-nitrophenoxy)benzoic acid in the organic solvent is 0.05 to 0.1 M; in step (2), the alcohol solvent is anhydrous ethanol; in step (3), the organic solvent is N,N-dimethylacetamide.

7. The preparation method according to claim 3, characterized in that: In step (3), the molar ratio of the hydrogenation product to the dianhydride monomer is 1:0.90-1.05; the molar ratio of acetic anhydride, isoquinoline and dianhydride is 1-2.5:0.5-1.25:

1.

8. A heat-resistant tape, characterized in that: The heat-resistant tape uses the polyimide adhesive described in claim 1 as the raw material for the bonding layer.

9. The method for preparing a heat-resistant tape according to claim 8, characterized in that: The preparation method comprises the following steps: coating the polyimide adhesive according to claim 1 on a film substrate, and then drying.

10. Use of the temperature-resistant tape according to claim 8 in QFN packaging.

Images