IME stretchable printing paste and preparation method thereof

Abstract

The invention provides IME stretchable printing paste which is prepared from the following components in percentage by mass: 50-72% of conductive silver powder; 0.5 to 1.5 percent of silver iodide powder; 15-25% of a polymer carrier; 10-25% of a solvent; and 1-3% of an additive. The flake silver powder, the dendritic silver powder and the silver nanowires are adopted and matched with the silver iodide powder to achieve lap joint after stretching forming and achieve lap joint at the low temperature (lt; and the nano-silver is decomposed during forming, so that the contact spot fusion welding effect is realized, and the resistance is reduced after forming and curing. A thermoplastic elastomer and long-chain thermosetting epoxy interpenetrating system is adopted, so that after curing, the tensile toughness and mechanical strength are both achieved, and the weather resistance is good.

Description

Technical Field

[0001] The invention relates to the field of electronic materials, in particular to an IME stretchable printing paste. Background Art

[0002] In the fields of new energy vehicles, aircraft, home appliances and consumer electronics, the demand for integration and lightweight of various electronic functional devices is constantly increasing. The In-Mold Electronic (IME) process developed on the basis of printed electronic technology is to directly print circuits on flexible film materials, SMT bond electronic components, put them into the mold for 3D high-pressure molding, and injection molding to achieve integrated plastic electronic touch panels. Compared with traditional PCB copper etching circuits, the IME process is suitable for various special-shaped components, has a simple process, and has the advantages of reliability, robustness, lightness, decorativeness, and adaptability to 3D human-machine interfaces.

[0003] Printing silver paste is the core key material of the IME process. It needs to have good printability, tensile ductility, conductivity and low-temperature thermal curing properties. It also needs to meet environmental durability testing requirements such as double 85, boiling water, high and low temperature cycles, and light testing.

[0004] Traditional thermosetting printed silver paste has poor tensile toughness, and often shows an increase in the resistance index after molding, which makes it difficult to meet the requirements of the IME process. The use of elastomer resin can obtain excellent tensile flexibility, but the stability after molding is poor. In terms of conductive particles, stretchable silver paste uses non-spherical particles such as flaky silver powder, dendrite silver powder, and silver nanowires to ensure the overlap of the conductive network after stretching molding. Nanosilver filling is also used, hoping to play a certain welding role in the hot forming process. However, nanosilver welding usually requires a high temperature of nearly 200°C and long curing time, which is difficult to work for most stretchable molding. Therefore, it is necessary to make targeted improvements to these problems. Summary of the invention

[0005] In order to solve the shortcomings of the prior art, the present invention provides an IME stretchable printing paste, which has excellent tensile bending toughness, excellent stability after molding, lower resistance after stretching molding, and good aging resistance after low-temperature curing.

[0006] In order to achieve the above technical purpose, the technical solution of the present invention is that an IME stretchable printing paste is prepared from the following components in terms of mass percentage:

[0007]

[0008] The sum of the mass percentages of the components is 100%.

[0009] Preferably, the IME stretchable printing paste is prepared from the following components in terms of mass percentage:

[0010]

[0011] The sum of the mass percentages of the components is 100%.

[0012] The conductive silver powder includes dendritic silver powder, silver nanowires and flaky silver powder; in the IME stretchable printing paste, the flaky silver powder accounts for 45-65%, the dendritic silver powder accounts for 3-5%, and the silver nanowires account for 2-5%.

[0013] The D50 particle size of the flaky silver powder is 6 to 10 μm; the D50 particle size of the dendritic silver powder is 1 to 2 μm; the diameter of the silver nanowire is 10 to 80 nm, and the length is 8 to 60 μm.

[0014] Wherein, the particle size of the silver iodide powder is less than 1.5 μm.

[0015] Among them, the polymer carrier includes a thermoplastic resin carrier and a thermosetting resin carrier; the thermoplastic resin carrier includes one or more of TPU resin, phenoxy resin, and chloroacetic acid resin; the thermosetting resin carrier includes one of epoxy-terminated siloxane and epoxy nitrile rubber ETBN.

[0016] Wherein, the solvent is one or more of alcohol ester dodecanedioic acid, ethylene glycol butyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol dibutyl ether, dimethyl adipate, triacetin, and dimethyl phthalate.

[0017] Among them, the additives include a curing agent, a thixotropic agent and a wetting agent; the curing agent is a thermal cationic curing agent, including one of a boron trifluoride complex, a boron trichloride complex, and an antimonium hexafluoride salt; the thixotropic agent includes one or more of fumed silica, polyamide wax, and polyamide-modified hydrogenated castor oil; and the wetting agent is dimethyl silicone oil.

[0018] Wherein, in the IME stretchable printing paste, the curing agent accounts for 0.5-1.5%, the thixotropic agent accounts for 0-0.3%, and the wetting agent accounts for 0.5-1.5%.

[0019] The present invention also provides a method for preparing the IME stretchable printing paste: firstly, a polymer carrier, a solvent and an additive are premixed, and then conductive silver powder and silver iodide powder are added, and mixed by a homogenizer, and then dispersed and homogenized on a three-roller machine to obtain the IME stretchable printing paste.

[0020] The IME stretchable printing paste of the present invention adopts a combination of flaky silver powder, dendrite silver powder, and silver nanowires, and cooperates with silver iodide powder to achieve overlap after stretching and molding, and decomposes nanosilver during molding at a relatively low temperature (<150°C) to achieve a contact point welding effect, and does not require a high temperature of 200°C and long-term curing, which is conducive to reducing resistance after molding and curing. The thermoplastic elastomer and long-chain thermosetting epoxy interpenetrating system are adopted, and after curing, both tensile toughness and mechanical strength are achieved, and weather resistance is good.

[0021] The IME stretchable printing paste of the present invention has excellent tensile bending toughness, excellent stability after molding, lower resistance after stretch molding, and good aging resistance after low-temperature curing, which solves the problem in the prior art that the resistance of the IME paste increases after stretch molding and the aging resistance is poor after low-temperature curing. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0023] The IME stretchable printing paste of the present invention is prepared from the following components according to mass percentage: 50-72% of conductive silver powder; 0.5-1.5% of silver iodide powder; 15-25% of polymer carrier; 10-25% of solvent; 1-3% of additives; the total mass fraction is 100%. The proportion of each component is reasonably distributed within its range, taking into account the conductive properties, printing properties and curing properties.

[0024] The IME stretchable printing paste of the present invention is prepared by the following method: first, premixing a polymer carrier, a solvent, and an additive. The polymer carrier includes a thermoplastic resin carrier and a thermosetting resin carrier. The thermoplastic resin carrier can be one or more of TPU resin, phenoxy resin, and chlorovinyl resin; the thermosetting resin carrier can be epoxy-terminated siloxane or epoxy-based nitrile rubber ETBN. The solvent can be one or more of alcohol ester dodecanol, ethylene glycol butyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol dibutyl ether, dimethyl adipate, triacetin, and dimethyl phthalate. The additives include a curing agent, a thixotropic agent, and a wetting agent; the curing agent is a thermal cationic curing agent, which can be one of a boron trifluoride complex, a boron trichloride complex, and an antimonium hexafluoride salt; the thixotropic agent can be one or more of fumed silica, polyamide wax, and polyamide-modified hydrogenated castor oil; the wetting agent is dimethyl silicone oil.

[0025] Then add conductive silver powder and silver iodide powder, and mix them with a homogenizer. The conductive silver powder includes dendritic silver powder, silver nanowires and flaky silver powder, of which flaky silver powder accounts for 45-65%, dendritic silver powder accounts for 3-5%, and silver nanowires account for 2-5%. The D50 particle size of the flaky silver powder is 6-10μm; the D50 particle size of the dendritic silver powder is 1-2μm; the diameter of the silver nanowire is 10-80nm and the length is 8-60μm. The particle size of the silver iodide powder is less than 1.5μm.

[0026] Finally, the mixture is dispersed and homogenized on a three-roll mill to obtain the IME stretchable printing paste.

[0027] Example 1: The above preparation method is used to prepare IME stretchable printing paste, and the proportions of each component are: 60% flaky silver powder, 3% dendritic silver powder, 2% silver nanowires, 1% silver iodide; 12% TPU resin, 9% epoxy nitrile rubber; 10.5% ethylene glycol ethyl ether acetate; 1.5% p-phenylthiophenyl diphenylsulfonium hexafluoroantimonate, 0.2% polyamide wax, and 0.8% dimethyl silicone oil.

[0028] Example 2: The above preparation method is used to prepare IME stretchable printing paste, and the proportions of each component are: 51% flaky silver powder, 4% dendritic silver powder, 3% silver nanowires, 1% silver iodide; 13% phenoxy resin, 10% epoxy nitrile rubber; 15% ethylene glycol dibutyl ether; 1.5% boron trifluoride complex, 0.3% polyamide wax, and 1.2% dimethyl silicone oil.

[0029] Example 3: The above preparation method is used to prepare IME stretchable printing paste, and the proportions of each component are: 65% flaky silver powder, 5% dendritic silver powder, 2% silver nanowires, 1.5% silver iodide; 9% chloroacetic acid resin, 6% epoxy nitrile rubber; 10% triacetin; 0.5% boron trifluoride complex, 0.3% polyamide wax, and 0.7% dimethyl silicone oil.

[0030] Example 4: The above preparation method is used to prepare IME stretchable printing paste, and the proportions of each component are: 45% flaky silver powder, 5% dendritic silver powder, 5% silver nanowires, 1.5% silver iodide; 10.5% chloroacetic acid resin, 10% epoxy-terminated siloxane; 20% dimethyl phthalate; 1.5% boron trichloride complex, 0.3% fumed silica, and 1.2% dimethyl silicone oil.

[0031] Comparative Example 1: The silver iodide in Example 1 was replaced with nano silver powder, and the other components and processes were the same.

[0032] Comparative Example 2: The epoxy nitrile rubber in Example 1 was replaced by DCPD type epoxy, and the other ingredients and processes were the same.

[0033] The products of the embodiment and the comparative example were printed on a TPU elastic substrate, dried at 70°C, and stretched at 130°C. The test performance results are shown in Table 1.

[0034] Table 1

[0035]

[0036] As can be seen from Table 1, the surface resistance of the IME stretchable printing paste of the embodiment of the present invention is slightly higher than that of adding nanosilver (Comparative Example 1), but the resistance after low-temperature thermoforming and stretching forming is lower, and the resistance change after bending and aging is smaller. Compared with the rigid curing epoxy (Comparative Example 2), the product of the embodiment of the present invention has an interpenetrating network system after curing, and has obvious advantages in stretching, bending and aging.

[0037] The IME stretchable printing paste of the present invention has excellent tensile bending toughness, excellent stability after molding, lower resistance after stretch molding, and good aging resistance after low-temperature curing, which solves the problem in the prior art that the resistance of the IME paste increases after stretch molding and the aging resistance is poor after low-temperature curing.

[0038] The IME stretchable printing paste of the present invention adopts flaky silver powder, dendrite silver powder, silver nanowire gradation, and silver iodide powder to achieve overlap after stretching and molding, and decomposes nanosilver during molding at a relatively low temperature (<150°C) to achieve contact point welding effect, and does not require high temperature of 200°C and long-term curing, which is conducive to reducing resistance after molding and curing. The thermoplastic elastomer and long-chain thermosetting epoxy interpenetrating system are adopted, and after curing, both tensile toughness and mechanical strength are obtained, and weather resistance is good. Therefore, the present invention effectively overcomes the shortcomings of the prior art and has a high industrial value.

[0039] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An IME stretchable printing paste, characterized in that: The IME stretchable printing paste is prepared from the following components according to mass percentage: The sum of the mass percentages of the components is 100%.

2. The IME stretchable printing paste according to claim 1, characterized in that: The IME stretchable printing paste is prepared from the following components according to mass percentage: The sum of the mass percentages of the components is 100%.

3. The IME stretchable printing paste according to claim 1 or 2, characterized in that: The conductive silver powder includes dendritic silver powder, silver nanowires and flaky silver powder; wherein, in the IME stretchable printing paste, the flaky silver powder accounts for 45-65%, the dendritic silver powder accounts for 3-5%, and the silver nanowires account for 2-5%.

4. The IME stretchable printing paste according to claim 3, characterized in that: The D50 particle size of the flaky silver powder is 6 to 10 μm; the D50 particle size of the dendritic silver powder is 1 to 2 μm; the diameter of the silver nanowire is 10 to 80 nm, and the length is 8 to 60 μm.

5. The IME stretchable printing paste according to claim 1 or 2, characterized in that: The silver iodide powder has a particle size of less than 1.5 μm.

6. The IME stretchable printing paste according to claim 1 or 2, characterized in that: The polymer carrier includes a thermoplastic resin carrier and a thermosetting resin carrier; the thermoplastic resin carrier includes one or more of TPU resin, phenoxy resin, and chloroacetic acid resin; the thermosetting resin carrier includes one of epoxy-terminated siloxane and epoxy-based nitrile rubber ETBN.

7. The IME stretchable printing paste according to claim 1 or 2, characterized in that: The solvent is one or more of alcohol ester dodecanedioic acid, ethylene glycol butyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol dibutyl ether, dimethyl adipate, triacetin, and dimethyl phthalate.

8. The IME stretchable printing paste according to claim 1 or 2, characterized in that: The additives include a curing agent, a thixotropic agent and a wetting agent; the curing agent is a thermal cationic curing agent, including one of a boron trifluoride complex, a boron trichloride complex, and an antimonium hexafluoride salt; the thixotropic agent includes one or more of fumed silica, polyamide wax, and polyamide-modified hydrogenated castor oil; and the wetting agent is dimethyl silicone oil.

9. The IME stretchable printing paste according to claim 8, characterized in that: In the IME stretchable printing paste, the curing agent accounts for 0.5-1.5%, the thixotropic agent accounts for 0-0.3%, and the wetting agent accounts for 0.5-1.5%.

10. The method for preparing an IME stretchable printing paste according to claim 1 or 2, characterized in that: First, the polymer carrier, solvent and additive are premixed, and then the conductive silver powder and silver iodide powder are added, mixed by a homogenizer, and then dispersed and homogenized on a three-roll mill to obtain the IME stretchable printing paste.

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