High-frequency low-dielectric-loss reversible adhesive film material, preparation method and application thereof

Abstract

The application relates to the field of high polymer materials and provides a preparation method of a high-frequency low-dielectric-loss reversible adhesive film material, which comprises the following steps: S1. Dissolving polybutadiene-based resin and a curing agent in a good solvent, adding a silicon-based filler after dissolving, obtaining solution A, then coating the solution A on the upper and lower surfaces of a polytetrafluoroethylene film, and drying to obtain a base film; S2. Dissolving end isocyanate group polybutadiene molecules in a good solvent to obtain solution B; dissolving active small molecules containing a pyrocatechol group in an organic solvent to obtain solution C; then mixing the solution B and the solution C, reacting for a period of time, and drying to obtain end pyrocatechol group polybutadiene molecules, dissolving the end pyrocatechol group polybutadiene molecules in a good solvent to obtain a modified layer resin solution; and S3. Coating the modified layer resin solution obtained in the step S2 on the upper and lower surfaces of the base film obtained in the step S1, and drying to obtain the reversible adhesive film material; the reversible adhesive film material can realize low dielectric loss of the whole material and reversible adhesion of the surface.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a high-frequency, low-dielectric-loss reversible adhesive film material, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of high-frequency communication information technology, high-frequency communication equipment is increasingly being used in various fields. During the long-term use of high-frequency communication equipment, the various external forces exerting pressure on the substrate bonding materials put them at risk of debonding, which can seriously interfere with the device's signal transmission and even cause short circuits. Currently, most dielectric adhesive materials used in high-frequency communication substrates are disposable, so repairing debonding failures often requires replacing the original substrate and related components. This results in significant waste of raw materials and the generation of electronic waste, which goes against the concept of sustainable development. The development of reversible adhesive materials is an ideal solution, allowing debonded components to be easily repaired and put back into use.

[0003] Unlike general electronic adhesives, high-frequency communication devices require substrate adhesives with sufficiently low high-frequency dielectric loss to ensure high-frequency signal transmission rates and fidelity. Therefore, current adhesive materials for high-frequency communication substrates are limited to low-polarity polymers such as polytetrafluoroethylene, polyolefins, and polyphenylene ether, but none of these materials possess reversible bonding properties.

[0004] Such as, in the prior art, publication number is CN109266262A Chinese patent discloses a kind of low dielectric loss composite adhesive and preparation method thereof, although the adhesive material of polybutadiene group shows excellent low dielectric loss in this technical scheme, but it can only be used as disposable adhesive material, and reversible adhesion cannot be realized, that is, adhesive material can not be bonded again after debonding and causes substrate to be scrapped. And so far, reversible adhesive material is mostly polar material again, and because material high frequency dielectric loss is positively correlated with material polarity, therefore its high dielectric loss is foreseeable, and cannot be used for the substrate bonding of high frequency electronic equipment. In a word, the contradiction between low dielectric loss and reversible adhesion makes the development of low dielectric material reversible adhesion very difficult, and urgently needs to explore a kind of new material design to take into account two kinds of performance. Summary of the Invention

[0005] The purpose of the present invention is to resolve the contradiction between low dielectric loss and reversible adhesion in existing material design, and to provide a method for preparing a reversible adhesive film material with high frequency and low dielectric loss. The method connects catechol groups with reversible adhesion function to both ends of low-polarity polybutadiene molecules as a modifying component, and applies it to the surface of a low-dielectric-loss polybutadiene-based adhesive film for modification, thereby achieving reversible adhesion while minimizing the dielectric loss of the entire film.

[0006] The design concept of the present invention is to use low dielectric adhesive material as the main part of the adhesive film, and to achieve low dielectric loss of the entire material and reversible adhesion of the surface by introducing only a small amount of reversible adhesive components on the surface of the film.

[0007] Specifically, the embodiments of the present invention are implemented through the following technical solutions:

[0008] A method for preparing a reversible adhesive film material with high frequency and low dielectric loss comprises the following steps:

[0009] S1. Base film: A polybutadiene-based resin and a curing agent are dissolved in a good solvent. After dissolution, a silicon-based filler (such as silica filler) accounting for 20%-80% by mass of the polybutadiene-based resin is added to obtain a solution A. Finally, the solution A is evenly applied to the upper and lower surfaces of the polytetrafluoroethylene film and dried to obtain a base film;

[0010] S2. Modified layer resin solution: Dissolve isocyanate-terminated polybutadiene molecules having an isocyanate group content of 2%-7% in a good solvent to obtain solution B; dissolve a reactive small molecule containing a catechol group in an organic solvent to obtain solution C; then mix solution B and solution C, stir and react at 0-80°C for 0.5-8h, terminate the reaction and dry to obtain modified layer catechol-terminated polybutadiene molecules, and dissolve the catechol-terminated polybutadiene molecules in a good solvent to obtain a modified layer resin solution;

[0011] S3. The modified layer resin solution obtained in step S2 is applied to the upper and lower surfaces of the base film obtained in S1. The thickness of the modified layer is 3-30 μm. After drying, an adhesive film sample is obtained. The copper foil is bonded under hot pressing conditions of 0.5-2 MPa and 140-200°C to obtain a reversible adhesive material with high frequency and low dielectric loss.

[0012] Furthermore, in S1, the polybutadiene-based resin includes one or more of 1,2-polybutadiene, 1,4-polybutadiene, poly(1,2-butadiene-co-1,4-butadiene), and derivatives retaining the polybutadiene chain structure.

[0013] Furthermore, in S1, the curing agent is one or more of cumene hydroperoxide, dibenzoyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; and the amount of the curing agent used accounts for 1%-8% of the mass of the polybutadiene.

[0014] Furthermore, in S1, the polytetrafluoroethylene membrane is a polytetrafluoroethylene resin membrane, a filler-modified polytetrafluoroethylene composite membrane (such as polytetrafluoroethylene blended with a low dielectric filler), or a surface-modified membrane based on the above membrane, and the material thickness is 10-80 μm.

[0015] Furthermore, in S2, the active small molecule containing a catechol group includes dopamine and / or 3,4-dihydroxyphenylethanol.

[0016] The present invention is based on the contradiction between low dielectric loss and reversible adhesion in the prior art, as well as the design of low-polarity reversible adhesive molecules and the surface modification process of the base film. Considering that polybutadiene macromolecules have low dielectric loss and also contain reactive carbon-carbon double bonds, the present invention selects polybutadiene molecules as the main chain of the reversible adhesive molecule; and combines with a catechol derivative containing only one active end group as a modification unit introduced into both ends of the polybutadiene main chain, so that the modified layer and the base film are firmly connected, the peel strength of the adhesive film is greatly improved, and the adhesive film is given reversible adhesion, thereby synthesizing a reversible adhesive molecule with low polarity.

[0017] As for the base film modification process, the present invention forms a modified layer by coating reversible adhesive molecules on the surface of the base film before curing. In the subsequent hot pressing bonding process, the polybutadiene chains in the base film will undergo a cross-linking reaction with the polybutadiene chains in the modified layer, thereby achieving a stable connection between the modified layer and the base film. In addition, by reducing the coating thickness, the impact of the modification on the overall low dielectric loss performance of the film can be further reduced.

[0018] On the other hand, the present invention provides a reversible adhesive material with high frequency and low dielectric loss, which is prepared by the above preparation method.

[0019] In another aspect, the present invention provides a use of the above-mentioned reversible adhesive material in high-frequency communication equipment or semiconductor electronic packaging.

[0020] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0021] 1. The present invention selects polybutadiene molecules as the main chain of the reversible adhesive molecule; and uses a catechol derivative containing only one active end group as a reversible adhesive modification functional unit introduced into both ends of the polybutadiene main chain. The large number of unsaturated double bonds in the molecular chain enables it to cross-link with the base film, ensuring that the catechol group is fixed to the surface of the base film. The stable connection between the modified layer and the base film greatly improves the peel strength of the adhesive film and imparts reversible adhesion to it. The reversible adhesive molecule with low polarity is synthesized, so that the adhesive film exhibits excellent adhesion to copper foil (peel strength>1.1N / mm) and reversible adhesion, allowing the copper foil to be stably re-bonded after debonding.

[0022] 2. The present invention uses a polybutadiene-based adhesive film as the base film, ensuring low dielectric loss across the entire material. Low-polarity polybutadiene molecular chains are selected as the carrier for the catechol structure, while these modified molecules are modified only on the surface of the low-dielectric base film, minimizing the impact of surface modification on the base film's low dielectric properties. Consequently, the reversible adhesive film material exhibits an ultra-low high-frequency dielectric loss of 0.0025-0.0029, meeting commercial standards for high-frequency communications. Furthermore, its reversible adhesion reduces equipment maintenance costs, extends equipment life, and reduces the generation of electronic waste. It can be applied to a variety of high-frequency electronic devices, promising broad industrial and market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 1 is the infrared reflection spectrum of the modified layer prepared in Example 1 and Example 2 of the present invention;

[0025] Figure 2 Scanning electron microscopy and elemental analysis characterization of the adhesive films prepared in Example 1 and Example 2;

[0026] Figure 3 The peel strength of the adhesive films prepared in Example 1, Example 2 and Comparative Example 1 and the peel strength after debonding and rebonding were tested;

[0027] Figure 4 Elemental analysis of the peeled surface of the copper foil bonding samples prepared in Example 1 and Example 2;

[0028] Figure 5 Characterization of the dielectric properties of the adhesive films prepared in Example 1 and Example 2 at 1 Hz-5 MHz;

[0029] Figure 6 The dielectric properties of the adhesive films prepared in Example 1 and Example 2 at 10 GHz are characterized. DETAILED DESCRIPTION

[0030] To further clarify the objectives, technical solutions, and advantages of the present invention, the following describes a method for preparing a reversible adhesive film material with high-frequency, low dielectric loss characteristics, as provided in the present invention. Where specific conditions are not specified in the examples, conventional conditions were used. Reagents used without manufacturer identification are commercially available or produced using publicly available techniques.

[0031] Example 1

[0032] This embodiment provides a method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material, comprising the following steps:

[0033] (1) 0.1 g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 5 g of polybutadiene-grafted polystyrene resin (PB-g-PS) and silica filler were added to 20 ml of cyclohexane solvent and stirred at room temperature until uniform, thereby preparing solution A; then, a portion of solution A was evenly coated on the upper and lower surfaces of a tetrafluoroethylene film (30 μm thick, provided by Maike Polymer Materials) using a coater, and dried to obtain a coating with a thickness of approximately 10 μm, thereby preparing a base film (PB-F);

[0034] (2) 5 g of toluene diisocyanate-terminated polybutadiene molecule (PB-NCO) was dissolved in N-methylpyrrolidone to obtain solution B; 15 g of 3,4-dihydroxyphenylethanol (DPO) was dissolved in N-methylpyrrolidone solution to obtain solution C; then, solution C was gradually added dropwise to solution B system, stirred and reacted at 30°C for about 5 h, and finally water was added to precipitate the product, and dried to obtain dihydroxyphenylethanol-terminated polybutadiene (PB-DPO);

[0035] (3) 4 g of PB-DPO molecules were dissolved in 10 ml of chloroform to obtain a uniform solution. Part of the solution was applied to the upper and lower surfaces of the PB-F base film and dried to obtain a modified layer with a thickness of about 10 μm, thereby preparing a sample film (PB-DPO-F). Finally, the copper foil was bonded under hot pressing conditions of 2 MPa and 180°C.

[0036] Example 2

[0037] This embodiment provides a method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material, comprising the following steps:

[0038] (1) 0.1 g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 5 g of PB-g-PS, and silica filler were added to 20 ml of cyclohexane solvent and stirred at room temperature until uniform, thereby preparing solution A; then, a portion of solution A was evenly coated on the upper and lower surfaces of a tetrafluoroethylene film using a coater, and dried to obtain a coating with a thickness of approximately 10 μm, thereby preparing a base film PB-F;

[0039] (2) 5 g of PB-NCO was dissolved in N-methylpyrrolidone to obtain solution B; 15 g of dopamine (DA) was dissolved in N-methylpyrrolidone to obtain solution C; then, solution C was gradually added dropwise to solution B, and the mixture was stirred at 30°C for about 5 h. Finally, water was added to precipitate the product, and the product was dried to obtain dihydroxyphenylethanol-terminated polybutadiene (PB-DA);

[0040] (3) 4 g of PB-DA molecules were dissolved in 10 ml of chloroform to obtain a uniform solution. Part of the solution was applied to the upper and lower surfaces of the PB-F base film and dried to obtain a modified layer with a thickness of about 10 μm, thereby preparing a sample film (PB-DA-F). Finally, the copper foil was bonded under hot pressing conditions of 2 MPa and 180°C.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that the polybutadiene-based resin is 1,2-polybutadiene; and the curing agent is cumene hydroperoxide.

[0043] Example 4

[0044] The difference between this embodiment and embodiment 1 is that the reaction conditions of solution B and solution C are 50° C. and the reaction time is 3 h.

[0045] Comparative Example 1

[0046] This comparative example provides a method for preparing a high-frequency, low-dielectric-loss adhesive film material, comprising the following steps:

[0047] 0.1 g of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 5 g of PB-g-PS and silica filler were added to 20 ml of cyclohexane solvent and stirred at room temperature until uniform to prepare solution A; then, part of solution A was applied to the upper and lower surfaces of a tetrafluoroethylene film of about 500 nm by a coater and dried to obtain a coating with a thickness of about 10 μm, thereby preparing a base film PB-F. Finally, the copper foil was bonded under hot pressing conditions of 2 MPa and 180°C as a control for the embodiment.

[0048] Experimental Example 1: Fourier Transform Infrared Characterization

[0049] 1. Test method

[0050] The PB-DPO prepared in Example 1 and the PB-DA prepared in Example 2 were subjected to Fourier transform infrared spectroscopy. The measurements were performed using a Nicolet IS50 infrared spectrometer produced by Thermo Fisher Scientific, USA, at a wavelength of 4 cm -1 Scan 16 times at a resolution of 100 nm.

[0051] 2. Test results

[0052] The peak positions of each group in the infrared spectrum are shown in Table 1. The infrared spectra comparison results of the catechol-terminated polybutadiene molecules BP-DPO and PB-DA prepared in the two examples and their raw materials are shown in Table 1. Figure 1 shown.

[0053] Table 1-Peak positions of various groups in infrared spectra

[0054] <![CDATA[Wavenumber(cm -1 )]]> Group 3200-3500 Phenol hydrogen bonding 2254 N=C=O 1750-1660 C=O 1530 NH 910 <![CDATA[-CH=CH2]]> 810 Ar-H

[0055] Figure 1 Contains infrared spectra of PB-DPO prepared in Example 1 and PB-DA prepared in Example 2. Figure 1 The comparison of infrared spectra shows that the two synthetic products have the -1 The -CH=CH2 bending vibration peak signal is strong, which proves the existence of PB main chain; PB-DA and PB-DPO do not have the peak signal of 2260~2270cm -1 The -NCO stretching vibration absorption peak at 1730-1750cm -1 There is an obvious C=O stretching vibration peak at 810 cm, which proves that amino ester or urea groups are formed in the two molecules; -1 The CH stretching vibration peak of the 1,3,4-trisubstituted benzene ring increased significantly, indicating that the o-substituted benzene ring was introduced into the synthetic product; the hydrogen bond absorption peak appeared at 3300 cm -1 The above analysis results confirmed the successful synthesis of PB-DPO and PB-DA macromolecules in the two examples.

[0056] Experimental Example 2: Scanning Electron Microscope-Energy Spectrometer Characterization

[0057] 1. Test method

[0058] The surface element types and morphological characteristics of the samples were observed using a scanning electron microscope (SEM, Apreo S HiVoc, Thermo Fisher Scientific) combined with energy dispersive X-ray spectrometry (EDS).

[0059] 2. Test results

[0060] The copper foil bonding cross-section characteristics of the PB-DPO-F adhesive films prepared in Example 1 and the PB-DA-F adhesive films prepared in Example 2 are as follows: Figure 2 As shown in the figure, the element distribution of the two groups of samples shows that the surface modification component containing nitrogen (N) elements is evenly distributed on the membrane surface with a thickness of about 10 μm.

[0061] The copper foil samples of the PB-DPO-F adhesive films prepared in Example 1 and the PB-DA-F adhesive films prepared in Example 2 were characterized by the following two peeling surfaces after peeling: Figure 4As shown. The elemental distribution of the two groups of peeled samples reveals significant nitrogen (N) and oxygen (O) on both the peeled surfaces of the adhesive film and copper foil, indicating the presence of PB-DPO or PB-DA on both surfaces. The peeled copper foil surface demonstrates that the modified molecules in the modified layer have strong adhesion to the copper foil; the peeled adhesive film surface demonstrates that sufficient cross-linking occurs between the polybutadiene molecular chains in the modified layer and the polybutadiene molecules in the base film, ensuring a stable layer structure.

[0062] Experimental Example 3: Characterization of Adhesive Properties

[0063] 1. Test method

[0064] The interfacial bond strength between the adhesive films of the Examples and Comparative Examples and the copper foil was measured using the T-peel test (GBT2791-1995) using a microcomputer-controlled electronic universal testing machine (CMT-4104, SANS) with a 500N load cell. The samples were cut into 25mm wide and 100mm-120mm long sections at an average peel speed of 100mm / min. The peeled copper foils were then re-bonded at 50°C and 8kPa, and the bond strength was then tested using the same method described above.

[0065] 2. Test results

[0066] The peeling test data of the copper foil bonding samples prepared in Example 1, Example 2 and Comparative Example 1 and the peeling test data of the copper foil bonding samples after being peeled and then bonded again are shown in FIG. Figure 3 As shown, the peel curves for Example 1, Example 2, and Comparative Example 1 are labeled PB-DPO-Re, PB-DPO-Re, and PB-Re. The comparative results demonstrate that surface modification with catechol significantly improves the bonding strength of the adhesive base film. More importantly, the adhesive samples prepared in Examples 1 and 2 can still be stably re-bonded after peeling, demonstrating excellent reversible adhesion. The PB-DPO-F prepared in Example 1 exhibits a peel strength of 1.1 N / mm, far exceeding the commercial standard of 0.8 N / mm for high-frequency communication equipment.

[0067] Experimental Example 4: Dielectric Properties Characterization

[0068] 1. Test method

[0069] The dielectric properties of the samples were measured at room temperature in the frequency range of 1 Hz to 5 MHz using a broadband dielectric impedance relaxation spectrometer (Concept 50, Novocontrol GmbH, Germany). The dielectric properties of the samples were measured at room temperature in the frequency range of 1 Hz to 1 MHz using a vector analyzer (N5224B, Keysight, USA) at 10 GHz using the split-cylinder resonator method (IPC-TM-650-2.5.5.13).

[0070] 2. Test results

[0071] The dielectric properties of the PB-DPO-F sample prepared in Example 1 and the PB-DPO-F sample prepared in Example 2 in the frequency range of 1 Hz to 5 MHz after irradiation are as follows: Figure 5 The results show that under MHz-level high-frequency alternating current, both groups of materials exhibit ultra-low dielectric loss (dielectric loss D f <0.003).

[0072] The dielectric properties of the PB-DPO-F sample prepared in Example 1 and the PB-DPO-F sample prepared in Example 2 at a frequency of 10 GHz after irradiation are as follows: Figure 5 The results show that the two groups of materials exhibit ultra-low dielectric loss of 0.0025-0.0029 at a high frequency of 10 GHz, reaching the commercial standard for high-frequency communication equipment.

[0073] In summary, the present invention successfully prepares a reversible adhesive film material with high frequency and low dielectric loss, so that the adhesive film exhibits excellent adhesion and reversible adhesion to copper foil, so that the copper foil can be stably re-bonded after debonding.

[0074] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material, characterized in that: The following steps are involved: S1. The polybutadiene-based resin and curing agent are dissolved in a good solvent, and after dissolution, a silicon-based filler is added to obtain a solution A, and then the solution A is evenly applied to the upper and lower surfaces of the polytetrafluoroethylene film and dried to obtain a base film; S2. Dissolving isocyanate-terminated polybutadiene molecules in a good solvent to obtain solution B; dissolving a reactive small molecule containing a catechol group in an organic solvent to obtain solution C; then mixing solutions B and C, stirring and reacting at a certain temperature for a period of time, terminating the reaction and drying to obtain catechol-terminated polybutadiene molecules, and dissolving the catechol-terminated polybutadiene molecules in a good solvent to obtain a modified layer resin solution; S3. Applying the modified layer resin solution obtained in step S2 to the upper and lower surfaces of the base film obtained in S1, and drying to obtain the high-frequency, low-dielectric-loss reversible adhesive film material.

2. The method for preparing a reversible adhesive film material with high frequency and low dielectric loss according to claim 1, characterized in that: In S1, the polybutadiene-based resin includes one or more of 1,2-polybutadiene, 1,4-polybutadiene, poly(1,2-butadiene-co-1,4-butadiene), and derivatives retaining the polybutadiene chain structure.

3. The method for preparing a reversible adhesive film material with high frequency and low dielectric loss according to claim 1, characterized in that: In S1, the curing agent is one or more of cumene hydroperoxide, dibenzoyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; and the amount of the curing agent used accounts for 1%-8% of the mass of the polybutadiene.

4. The method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material according to claim 1, characterized in that: In S2, the active small molecule containing a catechol group includes dopamine and / or 3,4-dihydroxyphenylethanol.

5. The method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material according to claim 1, characterized in that: In S2, the mixing ratio of solution B and solution C is any ratio greater than 0.5:1 based on the molar ratio of the active small molecule containing catechol group to the isocyanate-terminated polybutadiene molecule.

6. The method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material according to claim 1, wherein: In S2, the reaction conditions of solution B and solution C are 0-80 o C, reaction time 0.5-8 h.

7. The method for preparing a high-frequency, low-dielectric-loss reversible adhesive film material according to claim 1, wherein: In S3, the modified coating obtained after the modified layer resin solution is applied has a thickness of 3-30 um.

8. A high-frequency, low-dielectric-loss reversible adhesive film material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the high-frequency, low-dielectric-loss reversible adhesive film material according to claim 8 in high-frequency communication equipment.

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