Polyimide adhesive, preparation method of polyimide adhesive, temperature-resistant adhesive tape, and preparation method and application of temperature-resistant adhesive tape

Abstract

The invention discloses a polyimide adhesive and a preparation method thereof, and a temperature-resistant adhesive tape and a preparation method and application thereof, and belongs to the technical field of polyimide adhesives, the polyimide adhesive is prepared by taking a diamine monomer and a dianhydride monomer of a polyethylene glycol side chain as raw materials through esterification, hydrogenation and polymerization reaction; dissolving in an organic solvent, then coating on a film substrate, and drying to obtain the temperature-resistant adhesive tape. The adhesive tape shows excellent adhesive property at high temperature by utilizing the adhesion of the PEG side chain and the high-temperature stability of the polyimide main chain, has peelability, is suitable for QFN (Quad Flat No-lead) packaging of nickel, palladium, gold and other materials, and is also suitable for bonding of dielectric layers, multi-chip modules and integrated circuit chips in the microelectronic industry.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer adhesive materials, and specifically relates to a polyimide adhesive and a preparation method thereof, a heat-resistant adhesive tape and a preparation method and 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 national security. QFN packaging, full name Quad Flat No-leads Package, is a commonly used packaging type in surface mount technology. QFN packaging is widely used in various fields due to its small size, light weight, excellent thermal and electrical properties, etc.

[0003] The QFN packaging process steps are as follows: sticking high-temperature tape on the back of the lead frame, sticking the chip to the lead frame, silver paste curing, plasma cleaning, wire bonding, plastic sealing, removing high-temperature tape, post-curing, printing marks, cutting and forming, etc. Among them, the high-temperature tape is used to fix the lead frame to prevent leakage of plastic sealing materials, and must have high temperature resistance, high flatness, and no residual glue.

[0004] Polyimide adhesives are commonly used adhesive raw materials for high-temperature resistant tapes, but conventional polyimide resins have poor solubility, which increases the difficulty of their processing and limits the possibility of their widespread industrial application. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a polyimide adhesive and a preparation method thereof, wherein polyethylene glycol is introduced into a diamine monomer, and a polyamic acid solution is obtained by polymerization with a dianhydride monomer, and a soluble and fusible polyimide adhesive is prepared by chemical imidization, and the polyimide adhesive has good solubility in organic solvents and is easy to dilute and use. At the same time, the adhesive has good flexibility and is suitable for applications such as dielectric layers, multi-chip modules, and integrated circuit chip QFN packaging 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 of the bonding layer. The main chain of the polyimide adhesive has a rigid structure. Such a rigid structure improves the thermal stability of the polyethylene glycol side chain and utilizes the high-temperature adhesion of the polyethylene glycol to achieve the bonding performance of the tape at high temperatures. The tape has excellent stability and durability in a high-temperature environment and has removable properties after bonding is completed.

[0007] The technical solution adopted by the present invention is as follows:

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

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

[0010] The present invention also provides a method for preparing the polyimide adhesive, which comprises the following steps:

[0011] (1) subjecting polyethylene glycol monomethyl ether to an esterification reaction with 3-5-bis(4-nitrophenoxy)benzoic acid to obtain an esterification product;

[0012] (2) subjecting the esterification product obtained in step (1) to a hydrogenation reaction to obtain a hydrogenated product;

[0013] (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;

[0014] (4) dissolving the polyimide powder in an organic solvent so that the solid content is 10%-20%, thereby obtaining a polyimide adhesive;

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

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

[0017] (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;

[0018] (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;

[0019] (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;

[0020] (4) Dissolving the polyimide powder in an organic solvent so that its solid content is 10%-20%, thereby obtaining a 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 0.05-0.1M.

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

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

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

[0026] In step (3), the molar ratio of acetic anhydride, isoquinoline and 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 adhesive tape, wherein the heat-resistant adhesive tape uses the polyimide adhesive of the present invention as a raw material for an adhesive layer.

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

[0031] Furthermore, the film substrate is a thermosetting polyimide film substrate, and other temperature-resistant film substrates may also be selected.

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

[0033] The polyimide adhesive provided by the present invention is prepared by introducing polyethylene glycol (PEG) side chains into polyimide polymers, combining the high heat resistance of the polyimide main chain with the thermal adhesion of PEG, and preparing a high temperature resistant polyimide adhesive. In the structure, the thermal stability of PEG is improved by the imide ring of the main chain, making it suitable for QFN packaging. The polyimide tape can be used for the bonding and peeling of nickel-palladium-gold lead frames, laying a solid foundation for the breakthrough of localization.

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

[0035] 1. Uniform distribution of PEG: Polyimide adhesive is prepared by introducing PEG into diamine monomers and then polymerizing with commercial dianhydride. Each repeating unit on each polyimide molecular chain contains a PEG molecular chain, which makes it have good high-temperature adhesion.

[0036] 2. Optimized chemical composition, no need for external doping: Different from the traditional method of adding additional exogenous materials to the polyimide matrix to assist in improving adhesion, the present invention synthesizes an intrinsic polyimide adhesive containing PEG in the side chain, avoiding the dispersion and compatibility problems of the added materials.

[0037] 3. The polyimide main chain structure and the side chain PEG molecular weight are adjustable, so the bonding strength of the adhesive can be easily adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0039] Figure 2 is the nuclear magnetic hydrogen spectrum of the polyimide adhesive in Example 1;

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

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

[0042] Figure 5 The polyamide imide bonding (left) and peeling (right) test results in Example 1;

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

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

[0045] Figure 8 is the nuclear magnetic hydrogen spectrum of the polyimide adhesive in Example 3;

[0046] Fig. 9 This is the GPC chart of the polyimide adhesive in Example 3. DETAILED DESCRIPTION

[0047] The present invention is 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 onto the nickel-palladium-gold substrate at 240°C and a pressure of 5 MPa. The tape could 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 4: is a SEM picture of the surface morphology of the adhesive layer of the tape. It can be seen from the picture that the polyimide adhesive prepared in this embodiment has good film-forming performance.

[0058] The gel permeation chromatography (GPC) analysis of the polyamide imide solution obtained in step (3) of this embodiment is as follows: Figure 3 As shown, its molecular weight Mn = 23000 and polymer dispersibility index PDI = 1.86.

[0059] Example 2

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

[0061]

[0062] The preparation steps are as follows:

[0063] (1) 7.8 g (11.66 mmol) of the hydrogenation product in Example 1 was dissolved in 65 mL of N,N-dimethylacetamide, and 5.18 g (11.66 mmol) of 6FDA was added thereto under the protection of nitrogen and in an ice bath to obtain a polyamide imide precursor polyamic acid solution; 2.37 g (23.32 mmol) of acetic anhydride and 1.5 g (11.66 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 600 mL of cold methanol, filtered and dried to obtain a polyimide adhesive. The H NMR spectrum showed that Figure 6 shown.

[0064] (2) 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.

[0065] 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.

[0066] The gel permeation chromatography (GPC) analysis of the polyamide imide solution obtained in step (1) of this embodiment is as follows: Figure 7 As shown, its molecular weight Mn = 24000 and polymer dispersibility index PDI = 1.78.

[0067] Example 3

[0068] A method for preparing a polyimide adhesive, 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: Fig. 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] The rest is the same as Example 1, except that the polyethylene glycol monomethyl ether with a number average molecular weight of 350 is replaced by an equal molar amount of polyethylene glycol monomethyl ether with a number average molecular weight of 1800.

[0079] 2.0 g of the polyimide adhesive prepared in the comparative example was weighed, 10 mL of DMF was added to fully dissolve it, and then the adhesive was coated on a Kapton yellow film with a coating thickness of 1 um. The solvent was dried at 130° C. for 5 min to obtain a polyimide tape.

[0080] The polyimide tape was hot pressed onto the nickel-palladium-gold substrate at 240°C and a pressure of 5MPa. The tape was well adhered to the nickel-palladium-gold surface. After cooling, the tape could be peeled off from the nickel-palladium-gold substrate, but residual adhesive would appear after peeling. The residual adhesive rate is shown in Table 1.

[0081] The peeling force of the polyimide tapes prepared in the above embodiments was tested with reference to method 1 in GB T2792-2014 "Test method for peeling strength of adhesive tapes". The difference from method 1 in GB T2792-2014 "Test method for peeling strength of adhesive tapes" is that the stainless steel is replaced with a nickel-palladium-gold substrate. The test results are shown in the peeling force data in Table 1.

[0082] Table 1

[0083]

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

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

Claims

1. A polyimide adhesive, characterized in that: The structural formula of the polyimide adhesive 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 or 3,5-dinitrobenzoic 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 or 3,5-dinitrobenzoic 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.

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