Low-modulus low-temperature curing epoxy glue for protecting flexible circuit board and preparation method of low-modulus low-temperature curing epoxy glue

Abstract

The invention discloses a low-modulus low-temperature curing epoxy adhesive for protecting a flexible circuit board and a preparation method of the low-modulus low-temperature curing epoxy adhesive. The low-modulus low-temperature curing epoxy adhesive comprises epoxy 128, flexible epoxy resin, toughening resin, mercaptan, a latent amine curing agent, organic acid, fumed silica and filler CaCO3. Wherein the components comprise, by weight, 10 to 30 parts of epoxy 128, 10 to 30 parts of flexible epoxy resin, 0 to 13.6 parts of toughening resin, 29 parts of mercaptan, 5 parts of a curing agent, 0.4 part of an organic acid, 2 parts of fumed silica, and 20 parts of a filler CaCO3. The prepared low-modulus low-temperature curing epoxy adhesive for protecting the flexible circuit board is cured at low temperature and can be cured within half an hour at the temperature of 60 DEG C, the modulus of the adhesive is smaller than 1.5 GPa, and the elongation of the adhesive is gt; and the form of the adhesive is not changed before and after curing.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy structural adhesives, and specifically relates to a low-modulus, low-temperature curing epoxy adhesive for protecting flexible circuit boards and a preparation method thereof. Background Art

[0002] In modern circuit board design, the connection between FPC and PCB and screen module often appears, and there are many phenomena of direct bonding after bending in the connection structure. For example, after the FPC is bent and connected to the PCB circuit board, the bent structure is suspended in the cavity of the actual structure without any support. In order to prevent the flexible circuit board from being squeezed, impacted and other external forces from causing failure, its bent structure must have a certain buffer space. This result determines that the edge of the display FPC is relatively large because the structure provides a buffer area for the flexible circuit board.

[0003] In the new design, if there is a suitable adhesive, the bent flexible circuit board can be protected and fixed around the module with the cured adhesive. In this design, the bent FPC structure is fixed and protected by the surrounding materials, which can effectively prevent corrosion from external environments such as water and heat, and can effectively prevent damage to the structure from external forces such as impact. In another design, the FPC structure is bent and fixed first, and then the adhesive is applied around the bent FPC circuit board. The adhesive is then cured to ensure the reliability of the FPC.

[0004] The protective structure of the flexible circuit board needs to be fixed with a specific glue to fix its complete structure, and the adhesive needs to be able to bend with the FPC, which requires the material to have a relatively low modulus and high elongation. In addition, since FPC is used for electronic component structures, this type of structure is sensitive to light or heat. Therefore, when the adhesive is curing, it is necessary to ensure that the performance of the electronic components is not affected by the curing method. In the process of protecting the FPC with adhesive, bubbles as defects will cause serious poor dielectric properties, so it is necessary to control the bubble content and size of the system. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a low modulus, low temperature curing epoxy adhesive for protecting flexible circuit boards.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a low modulus low temperature curing epoxy adhesive for protecting flexible circuit boards, characterized in that it comprises epoxy 128, flexible epoxy resin, toughening resin, thiol, latent amine curing agent, organic acid, fumed silica and filler CaCO3;

[0009] Among them, calculated by mass, epoxy 128 is 10 to 30 parts, flexible epoxy resin is 10 to 30 parts, toughening resin is 0 to 13.6 parts, thiol is 19 to 45 parts, latent amine curing agent is 3 to 5 parts, organic acid is 0 to 0.4 parts, fumed silica is 2 parts, and filler CaCO3 is 20 parts.

[0010] As a preferred embodiment of the low modulus low temperature curing epoxy adhesive of the present invention, the flexible epoxy comprises one or more of butanediol glycidyl ether, polypropylene glycol glycidyl ether and propoxylated bisphenol A glycidyl ether.

[0011] As a preferred embodiment of the low modulus, low temperature curing epoxy adhesive of the present invention, the thiol component includes one or more of pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate) and pentaerythritol tetrakis(3-mercaptobutyrate).

[0012] As a preferred embodiment of the low modulus and low temperature curing epoxy adhesive of the present invention, the latent amine curing agent includes one or more of hydrazide, imidazole adduct, amine derivative and microcapsule curing agent.

[0013] As a preferred embodiment of the low modulus low temperature curing epoxy adhesive of the present invention, the organic acid comprises one or more of malic acid, barbituric acid, citric acid, salicylic acid, methyl gallate and tartaric acid.

[0014] As a preferred embodiment of the low modulus, low temperature curing epoxy adhesive of the present invention, the epoxy 128 is 30 parts, the flexible epoxy resin is 10 parts, the toughening resin is 3.6 parts, the thiol is 29 parts, the latent amine curing agent is 5 parts, the organic acid is 0.4 parts, the fumed silica is 2 parts, and the filler CaCO3 is 20 parts.

[0015] As a preferred embodiment of the low modulus, low temperature curing epoxy adhesive of the present invention, the curing temperature of the low modulus, low temperature curing epoxy adhesive is 60°C.

[0016] As a preferred embodiment of the low modulus low temperature curing epoxy adhesive of the present invention, the modulus of the low modulus low temperature curing epoxy adhesive is less than 1.5 GPa, and the elongation of the adhesive is greater than 50%.

[0017] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a low modulus, low temperature curing epoxy adhesive for protecting flexible circuit boards.

[0018] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for preparing a low modulus, low temperature curing epoxy adhesive for protecting flexible circuit boards, characterized in that: it includes: stirring epoxy 128G, flexible epoxy resin, toughening resin, fumed silica, calcium carbonate, and organic acid, adding thiol and continuing to stir, cooling to room temperature, and adding a latent amine curing agent to obtain a mixture; stirring the mixture, evacuating the mixture for degassing, and then repeatedly stirring and mixing to obtain the low modulus, low temperature curing epoxy adhesive.

[0019] As a preferred embodiment of the preparation method of the present invention, the stirring time is 30 minutes and the stirring rate is 1000 rpm.

[0020] As a preferred embodiment of the preparation method of the present invention, the stirring is repeated 3 times.

[0021] Beneficial effects of the present invention:

[0022] The low modulus low temperature curing epoxy adhesive for protecting flexible circuit boards prepared by the present invention can be cured at 60 degrees within half an hour, the adhesive modulus is less than 1.5 GPa, the adhesive elongation is greater than 50%, and the morphology of the adhesive does not change before and after curing. 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 describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0024] Figure 1 It is a graph showing the elongation results of Examples 1 to 5 of the present invention and Comparative Examples 1 to 4.

[0025] Figure 2 It is a graph showing the elongation results of Examples 6 to 12 of the present invention and Comparative Examples 5 to 6.

[0026] Figure 3 This is a physical picture of the low modulus, low temperature curing epoxy adhesive prepared in Example 1 of the present invention.

[0027] Figure 4 The bending test results of the low modulus, low temperature curing epoxy adhesive prepared in Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0031] Unless otherwise specified, all raw materials used in the examples of the present invention are commercially available, as shown in Table 1 for details.

[0032] Table 1

[0033]

[0034]

[0035] The performance test method of the low modulus low temperature curing epoxy adhesive prepared in each embodiment and comparative example of the present invention is as follows:

[0036] Curing process conditions: Test at 60℃: Place 1g of test glue sample in a sealed transparent container, and observe the changes in the glue sample after 0.5℃. "Cured" means it is fully cured.

[0037] Adhesion test: refer to GB / T 7124-86, the aluminum substrate used for the test was scrubbed and degreased with ethanol, the glue sample was applied to the surface to be bonded, and then the thickness of the glue layer was controlled with a 125μm iron wire; after the treatment, it was placed in an oven preheated to 60℃, and the timer started for 0.5h when the oven returned to 60℃, the sample was taken out, and finally tested on a tensile testing machine.

[0038] Modulus and elongation test: refer to GB1040-79. Under the condition of controlling the sample thickness to 300um, the adhesive was cured at 60℃ for 0.5h, and then prepared into dumbbell-shaped specimens, which were tested on a tensile machine at a speed of 10mm / min.

[0039] Bending test: The sample is coated into a 100um thick film, and then completely cured in an oven at 60 degrees Celsius for 30 minutes. The sample is naturally bent and placed on the table to observe the bending shape of the sample.

[0040] Example 1

[0041] This embodiment provides a method for preparing a low modulus, low temperature curing epoxy adhesive for protecting a flexible circuit board:

[0042] The low modulus, low temperature curing epoxy adhesive is calculated by weight and consists of 30 parts of Nan Ya Epoxy 128G, 10 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 29 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0043] (1) Nan Ya epoxy 128G, flexible epoxy, MX154 toughening resin, fumed silica, filler calcium carbonate, and stabilizer (methyl gallate) were stirred at 1000 rpm for 30 min and mixed uniformly.

[0044] (2) After adding 29 parts of mercaptan TMPMP, stirring was continued for 30 minutes. After cooling to room temperature, 5 parts of curing agent FXR1081 were added and stirring was continued for 5 minutes to obtain a mixture.

[0045] (3) The mixture was stirred at a rotation speed of 2000 rpm for 30 seconds, vacuumed and degassed, and the stirring was repeated 3 times to mix the mixture evenly and discharge the mixture to obtain the low modulus, low temperature curing epoxy adhesive of this embodiment.

[0046] Example 2

[0047] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 10 parts of Nan Ya Epoxy 128G, 30 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 29 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0048] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0049] Example 3

[0050] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 30 parts of Nan Ya Epoxy 128G, 10 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 29 parts of mercaptan TMPMP, 3 parts of curing agent FXR1081, 2 parts of MY24, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0051] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0052] Example 4

[0053] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 20 parts of Nan Ya Epoxy 128G, 10 parts of 1,4-butanediol diglycidyl ether, 13.6 parts of MX154 toughening resin, 29 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0054] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0055] Example 5

[0056] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 30 parts of Nan Ya Epoxy 128G, 10 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 19 parts of mercaptan TMPMP, 10 parts of PETMP, 3 parts of curing agent FXR1081, 2 parts of MY24, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0057] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 40 parts of Nan Ya Epoxy 128G, 3.6 parts of MX154 toughening resin, 29 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0060] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this comparative example.

[0061] Comparative Example 2

[0062] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 40 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 29 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0063] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this comparative example.

[0064] Comparative Example 3

[0065] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 30 parts of epoxy 128, 20 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 19 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0066] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this comparative example.

[0067] Comparative Example 4

[0068] The difference from Example 1 is that the low modulus, low temperature curing epoxy adhesive is calculated by mass and consists of 30 parts of epoxy 128, 10 parts of 1,4-butanediol diglycidyl ether, 3.6 parts of MX154 toughening resin, 45 parts of thiol TMPMP, 5 parts of curing agent FXR1081, 0.4 parts of methyl gallate, 2 parts of gas silicone TS720, and 20 parts of filler CaCO3.

[0069] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this comparative example.

[0070] Comparative Examples 1 to 5 and Comparative Examples 1 to 4 obtained the relevant properties of low modulus low temperature curing epoxy adhesives. The results are as follows Figure 1 And as shown in Table 2.

[0071] Table 2

[0072]

[0073] As can be seen from Table 2, the low modulus low temperature curing epoxy adhesive for flexible circuit board protection prepared by the present invention can be cured at low temperature within half an hour at 60 degrees, and the adhesive modulus is less than 1.5 GPa. Figure 1 It can be seen that the elongation of the adhesive is >50%, and the morphology of the adhesive does not change before and after curing.

[0074] Example 6

[0075] The difference from Example 1 is that the flexible epoxy butylene glycol glycidyl ether is replaced by DER732 (polypropylene glycol glycidyl ether) in the low modulus low temperature curing epoxy adhesive.

[0076] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0077] Example 7

[0078] The difference from Example 1 is that the flexible epoxy butylene glycol glycidyl ether is replaced by SE-4125P (propoxylated bisphenol A glycidyl ether) in the low modulus low temperature curing epoxy adhesive.

[0079] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0080] Example 8

[0081] The difference from Example 1 is that the curing agent FXR1081 in the low modulus, low temperature curing epoxy adhesive is replaced by HXA3932HP (capsule-type imidazole curing agent).

[0082] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0083] Example 9

[0084] The difference from Example 1 is that in the low modulus, low temperature curing epoxy adhesive, the mercaptan TMPMP is replaced by PE-1 (pentaerythritol tetrakis(3-mercaptobutyrate)).

[0085] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0086] Example 10

[0087] The difference from Example 1 is that methyl gallate is replaced by barbituric acid in the low modulus, low temperature curing epoxy adhesive.

[0088] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0089] Embodiment 11

[0090] The difference from Example 1 is that MX154 is not added to the low modulus, low temperature curing epoxy adhesive.

[0091] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0092] Example 12

[0093] The difference from Example 1 is that MX154 is replaced by toughening resin XT-100 in the low modulus low temperature curing epoxy adhesive.

[0094] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this embodiment.

[0095] Comparative Example 5

[0096] The difference from Example 1 is that the flexible epoxy resin in the low modulus low temperature curing epoxy adhesive is replaced by bisphenol F type epoxy resin 170.

[0097] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this comparative example.

[0098] Comparative Example 6

[0099] The difference from Example 1 is that in the low modulus, low temperature curing epoxy adhesive, the flexible epoxy butanediol diglycidyl ether is replaced by HP-4032D naphthalene diglycidyl ether.

[0100] The remaining steps and processes are all referred to the embodiment to obtain the low modulus and low temperature curing epoxy adhesive of this comparative example.

[0101] The test results are shown in Table 3.

[0102] Table 3

[0103]

[0104] like Figure 2 As shown, this is the elongation result diagram of the present invention, Figures 3-4 The bending test result of the present invention is shown in Table 3. The elongation is greater than 50% and the sample will not return to the initial flat state.

[0105] In summary, the present invention uses Nan Ya Epoxy 128G as rigid epoxy, 1,4-butanediol diglycidyl ether as flexible epoxy, thiol TMPMP or PETMP as main curing resin, curing agent FXR1081 or MY24 as curing accelerator, and achieves a curing temperature of less than 65°C. Methyl gallate is a stabilizer, and filler CaCO3 and gas silicon TS720 are added to improve the thixotropic performance of the system, requiring a thixotropic of 2 to 6 to meet different applications.

[0106] The present invention improves the toughness of the system by increasing the toughening agent content, and has better elongation and adhesion performance; the addition of functional mercaptan can increase the modulus of the system, and through combination with curing, the modulus, adhesion and elongation of the system can be adjusted within a suitable range; after removing the flexible epoxy, the modulus of the system is increased and the elongation becomes lower; without the rigid epoxy structure, the elongation of the system is relatively long, the modulus is relatively low, and the adhesion is relatively low; when the mercaptan content is reduced, the cross-linking density of the system is insufficient, and the adhesion is seriously reduced; when the mercaptan content is too high, the cross-linking density is relatively low, and the adhesion is reduced.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A low modulus, low temperature curing epoxy adhesive for protecting flexible circuit boards, characterized in that: Including epoxy 128, flexible epoxy resin, toughening resin, mercaptan, latent amine curing agent, organic acid, fumed silica and filler CaCO3; Among them, calculated by mass, epoxy 128 is 10 to 33.6 parts, flexible epoxy resin is 10 to 30 parts, toughening resin is 0 to 13.6 parts, thiol is 19 to 45 parts, curing agent is 3 to 5 parts, organic acid is 0 to 0.4 parts, fumed silica is 2 parts, and filler CaCO3 is 20 parts.

2. The low modulus, low temperature curing epoxy adhesive according to claim 1, characterized in that: The flexible epoxy comprises one or more of butanediol glycidyl ether, polypropylene glycol glycidyl ether and propoxylated bisphenol A glycidyl ether.

3. The low modulus low temperature curing epoxy adhesive according to claim 1, characterized in that: The thiol component includes one or more of pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate) and pentaerythritol tetrakis(3-mercaptobutyrate).

4. The low modulus low temperature curing epoxy adhesive according to claim 1, characterized in that: The latent amine curing agent includes one or more of hydrazide, imidazole adduct, amine derivative and microcapsule curing agent.

5. The low modulus, low temperature curing epoxy adhesive according to claim 1, characterized in that: The organic acid includes one or more of malic acid, barbituric acid, citric acid, salicylic acid, methyl gallate and tartaric acid.

6. The low modulus, low temperature curing epoxy adhesive according to claim 1, characterized in that: Calculated by mass, epoxy 128 is 30 parts, flexible epoxy resin is 10 parts, toughening resin is 3.6 parts, thiol is 29 parts, curing agent is 5 parts, organic acid is 0.4 parts, fumed silica is 2 parts, and filler CaCO3 is 20 parts.

7. The low modulus, low temperature curing epoxy adhesive according to claim 1, characterized in that: The curing temperature of the low modulus low temperature curing epoxy adhesive is 60°C.

8. The low modulus, low temperature curing epoxy adhesive according to claims 1 to 7, characterized in that: The modulus of the low modulus low temperature curing epoxy adhesive is less than 1.5 GPa, and the elongation of the adhesive is greater than 50%.

9. A method for preparing a low modulus, low temperature curing epoxy adhesive for protecting flexible circuit boards, characterized in that: The method comprises the steps of adding mercaptan to epoxy 128G, flexible epoxy resin, toughening resin, fumed silica, calcium carbonate and organic acid, and continuing to stir, cooling to room temperature, and then adding a curing agent to obtain a mixture; stirring the mixture, evacuating the mixture for degassing, and then repeatedly stirring and mixing the mixture to obtain the low modulus low temperature curing epoxy adhesive.

10. The preparation method according to claim 7, characterized in that: The stirring time is 30 minutes, the stirring rate is 1000 rpm, and after the stirring is completed, the adhesive is vacuumed and degassed for 20 minutes to remove bubbles in the adhesive.

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