Low-temperature curing carbon paste for flexible printed circuit and preparation method of low-temperature curing carbon paste

Abstract

The invention discloses a low-temperature curing carbon paste for a flexible printed circuit, which comprises the following raw materials: a conductive functional phase, an organic carrier and an auxiliary agent, the conductive functional phase accounts for 15-50% of the total mass of the raw materials, the organic carrier accounts for 44-84.5% of the total mass of the raw materials, and the auxiliary agent accounts for 0.5-6% of the total mass of the raw materials. The carbon paste can be cured at the temperature of 80-120 DEG C, and meanwhile it can be guaranteed that the carbon paste can reach low sheet resistance and good adhesive force.

Description

Technical Field

[0001] The present invention relates to the field of cured carbon paste, in particular to a low-temperature cured carbon paste for flexible printed circuits and a preparation method thereof. Background Art

[0002] Flexible printed circuits (FPCs) are typically manufactured on substrates that are not heat-resistant, such as plastics, fabrics, leather, and paper. Current manufacturing processes require printing conductive circuits on these heat-sensitive substrates to connect various functional components and achieve a complete conductive path. Low-temperature curing carbon pastes currently on the market typically cure at temperatures between 180 and 200°C, a relatively high temperature and a long-standing monopoly in foreign markets. However, there are currently limited carbon paste options available for use on heat-sensitive polymer films such as PET and PC.

[0003] Currently, curing agents and photoinitiators are generally added to the low-temperature curing carbon paste in the workplace. The curing agent will cause the carbon paste to cure slowly during storage, and the shelf life is generally no more than 6 months, or even shorter. Summary of the Invention

[0004] The object of the present invention is to provide a low-temperature curing carbon paste for flexible printed circuits.

[0005] The present invention also provides a method for preparing low-temperature curing carbon paste for flexible printed circuits.

[0006] The innovation of the present invention lies in that the carbon paste can be cured at 80-120° C. and at the same time can ensure that the carbon paste can achieve lower sheet resistance and better adhesion.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0008] A low-temperature curing carbon paste for flexible printed circuits comprises the following raw materials: a conductive functional phase, an organic carrier and an additive, wherein the conductive functional phase accounts for 15-50% of the total mass of the raw materials, the organic carrier accounts for 44-84.5% of the total mass of the raw materials, and the additive accounts for 0.5-6% of the total mass of the raw materials.

[0009] Furthermore, the conductive functional phase includes at least two of carbon black, graphite, and carbon nanotubes.

[0010] Furthermore, the organic carrier raw material includes a solvent and two or more resins, the mass of the resin in the organic carrier is 10-60% of the mass of the organic carrier, and the solvent is an ester solvent, an alcohol solvent or a ketone solvent.

[0011] Furthermore, the resin includes two or more of epoxy resin, phenoxy resin, polyester resin, phenolic resin, and acrylic resin, and the solvent is one or more of diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, dibasic acid ester, terpineol, butyl carbitol, and isophorone.

[0012] Furthermore, the auxiliary agent includes a dispersant, a rheological additive and a defoaming agent.

[0013] Furthermore, the dispersant is BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313 or BYK-314.

[0014] Furthermore, the rheological additive is bentonite, modified bentonite or wax dispersion.

[0015] Furthermore, the defoaming agent is an organosilicon defoaming agent, a polymer defoaming agent or an organosilicon and polymer mixed defoaming agent.

[0016] A method for preparing a low-temperature curing carbon paste for a flexible printed circuit comprises the following steps:

[0017] (1) Weigh the organic carrier raw materials according to the formula, heat and stir in a water bath at 80°C, fully disperse the resin in the solvent, stir evenly, and cool to obtain the organic carrier;

[0018] (2) Weigh the raw materials according to the formula, mix the slurry thoroughly with a homogenizer or planetary mixer, and then repeatedly roll the slurry several times with a three-roll mill until the slurry fineness reaches less than 10 microns to obtain the finished product.

[0019] The beneficial effects of the present invention are:

[0020] 1. The carbon paste of the present invention has a low curing temperature of 80-120°C and a curing time of

[0021] 30 to 60 minutes, low curing temperature, short curing time, good adhesion to the substrate, high hardness and strong wear resistance.

[0022] 2. The low-temperature curing carbon paste of the present invention can be used not only for printing on heat-resistant substrates, such as silicon wafers, glass and other substrates, but also for printing on heat-sensitive substrates, such as PET, PC, PI, fabrics, paper and other substrates, which greatly expands the scope of application of the carbon paste. In addition, the carbon paste is safe, environmentally friendly, non-toxic and harmless, and can be stably stored at low temperatures for 6-12 months. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0024] Example 1: A low-temperature curing carbon paste for flexible printed circuits, comprising the following raw materials: a conductive functional phase, an organic vehicle and an additive, wherein the conductive functional phase accounts for 15% of the total mass of the raw materials, the organic vehicle accounts for 84.5% of the total mass of the raw materials, and the additive accounts for 0.5% of the total mass of the raw materials.

[0025] The conductive functional phase includes carbon black and graphite.

[0026] The organic carrier raw materials include solvent and two or more resins, the mass of the resin in the organic carrier accounts for 30% of the mass of the organic carrier, the resin includes epoxy resin and phenoxy resin, and the solvent is diethylene glycol butyl ether acetate.

[0027] Additives include dispersants, rheological additives and defoamers. The dispersant is BYK-300.

[0028] The rheological additive is bentonite and the defoaming agent is a silicone defoaming agent.

[0029] Example 2: A low-temperature curing carbon paste for flexible printed circuits, comprising the following raw materials: a conductive functional phase, an organic carrier and an additive, wherein the conductive functional phase accounts for 50% of the total mass of the raw materials, the organic carrier accounts for 44% of the total mass of the raw materials, and the additive accounts for 6% of the total mass of the raw materials.

[0030] The conductive functional phase includes graphite and carbon nanotubes.

[0031] The organic carrier raw materials include solvent and two or more resins, the mass of the resin in the organic carrier accounts for 10% of the mass of the organic carrier, the resin includes polyester resin and phenolic resin, and the solvent is ethylene glycol butyl ether acetate.

[0032] The additives include dispersants, rheological additives and defoamers. The dispersant is BYK-301.

[0033] The rheological additive is modified bentonite and the defoamer is a polymer defoamer.

[0034] Example 3: A low-temperature curing carbon paste for flexible printed circuits, comprising the following raw materials: a conductive functional phase, an organic carrier and an additive, wherein the conductive functional phase accounts for 35% of the total mass of the raw materials, the organic carrier accounts for 62% of the total mass of the raw materials, and the additive accounts for 3% of the total mass of the raw materials.

[0035] The conductive functional phase includes carbon black and carbon nanotubes.

[0036] The organic carrier raw materials include solvent and two or more resins, the mass of the resin in the organic carrier accounts for 60% of the mass of the organic carrier, the resin includes phenolic resin and acrylic resin, and the solvent is terpineol.

[0037] Additives include a dispersant, a rheological modifier, and a defoamer. The dispersant is BYK-302. The rheological modifier is a polyamide wax dispersion. The defoamer is a blend of silicone and polymer.

[0038] Example 4: Referring to Example 1, the conductive functional phase includes at least two of carbon black, graphite, and carbon nanotubes.

[0039] The organic carrier raw material includes a solvent and two or more resins. The mass of the resin in the organic carrier accounts for 10-60% of the mass of the organic carrier. The solvent is an ester solvent, an alcohol solvent or a ketone solvent.

[0040] The resin includes two or more of epoxy resin, phenoxy resin, polyester resin, phenolic resin and acrylic resin, and the solvent is one or more of diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, dibasic acid ester, terpineol, butyl carbitol and isophorone.

[0041] Additives include dispersants, rheological modifiers, and defoamers. Dispersants are BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, or BYK-314. Rheological modifiers are bentonite, modified bentonite, or wax dispersions. Defoamers are silicone defoamers, polymer defoamers, or silicone / polymer hybrids.

[0042] Example 5: A method for preparing a low-temperature curing carbon paste for a flexible printed circuit, comprising the following steps:

[0043] (1) Weigh the organic carrier raw material according to the formula of Example 1, heat and stir in a water bath at 80°C, fully disperse the resin in the solvent, stir evenly, and cool to obtain the organic carrier;

[0044] (2) Weigh the raw materials according to the formula of Example 1, mix the slurry thoroughly with a homogenizer or a planetary mixer, and then repeatedly roll the slurry several times with a three-roll mill until the slurry fineness reaches less than 10 microns to obtain the finished product.

[0045] Example 6: Referring to Example 5, the formula was changed to that of Example 2.

[0046] Example 7: Referring to Example 6, the formula was changed to that of Example 3.

[0047] Comparative Example 1: Referring to Example 5, all the resins were replaced with epoxy resins.

[0048] Carbon slurry performance test: After the carbon slurry was prepared, its viscosity was tested (test conditions: Brookfield HBT utility cup and spindle (SC4-14 / 6R), 10 rpm, 25 ± 1 ° C). The square resistance of the cured carbon slurry was tested after curing in an oven at 120 ° C for 30 minutes. Its adhesion was tested using the 100 grid method. The relevant test results are shown in Table 1.

[0049] Table 1

[0050]

[0051] The data in Table 1 show that Example 6 has the highest powder content and the best conductivity, but its hardness decreases due to the relatively low resin content. The organic carrier of the single resin system in Comparative Example 1 has relatively poor adhesion and hardness.

[0052] It should be noted that, in addition to being applicable to the field of flexible printed circuits, the carbon paste of the present invention may also be used in other fields, such as 3D printing, membrane switches, solar cells, semiconductor packaging, consumer electronics, radio frequency identification tags, and electronic component packaging.

[0053] The embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A low temperature curing carbon paste for flexible printed circuits, characterized in that: The invention comprises the following raw materials: a conductive functional phase, an organic carrier and an auxiliary agent, wherein the conductive functional phase accounts for 15-50% of the total mass of the raw materials, the organic carrier accounts for 44-84.5% of the total mass of the raw materials, and the auxiliary agent accounts for 0.5-6% of the total mass of the raw materials.

2. The low-temperature curing carbon paste for flexible printed circuits according to claim 1, characterized in that: The conductive functional phase includes at least two of carbon black, graphite, and carbon nanotubes.

3. The low temperature curing carbon paste for flexible printed circuits according to claim 1, characterized in that: The organic carrier raw material includes a solvent and two or more resins, the mass of the resin in the organic carrier accounts for 10-60% of the mass of the organic carrier, and the solvent is an ester solvent, an alcohol solvent or a ketone solvent.

4. The low-temperature curing carbon paste for flexible printed circuits according to claim 3, characterized in that: The resin includes two or more of epoxy resin, phenoxy resin, polyester resin, phenolic resin and acrylic resin, and the solvent is one or more of diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, dibasic acid ester, terpineol, butyl carbitol and isophorone.

5. The low temperature curing carbon paste for flexible printed circuits according to claim 1, characterized in that: The auxiliary agents include dispersants, rheological additives and defoaming agents.

6. The low-temperature curing carbon paste for flexible printed circuits according to claim 5, characterized in that: The dispersant is BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313 or BYK-314.

7. The low temperature curing carbon paste for flexible printed circuits according to claim 5, characterized in that: The rheological additive is bentonite, modified bentonite or polyamide wax dispersion.

8. The low temperature curing carbon paste for flexible printed circuits according to claim 5, characterized in that: The defoaming agent is an organosilicon defoaming agent, a polymer defoaming agent or a mixed defoaming agent of organosilicon and polymer.

9. A method for preparing a low-temperature curing carbon paste for flexible printed circuits according to any one of 1 to 5, characterized in that: The following steps are involved: (1) Weigh the organic carrier raw materials according to the formula, heat and stir in a water bath at 80°C, fully disperse the resin in the solvent, stir evenly, and cool to obtain the organic carrier; (2) Weigh the raw materials according to the formula, mix the slurry thoroughly with a homogenizer or planetary mixer, and then repeatedly roll the slurry several times with a three-roll mill until the slurry fineness reaches less than 10 microns to obtain the finished product.

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