CN115584185A

CN115584185A - Weldable tin-copper slurry and preparation method and application thereof

Info

Publication number: CN115584185A
Application number: CN202211313149.6A
Authority: CN
Inventors: 赖顺兴; 赖华恩
Original assignee: Shenzhen Lihongjin Technology Co ltd
Current assignee: Shenzhen Lihongjin Technology Co ltd
Priority date: 2022-10-25
Filing date: 2022-10-25
Publication date: 2023-01-10

Abstract

The application relates to a weldable tin-copper slurry and a preparation method and application thereof, wherein the weldable tin-copper slurry comprises the following components in parts by mass: 4-8 parts of polyurethane modified epoxy resin, 1-3 parts of polyester resin, 0.05-0.15 part of defoaming agent, 0.05-0.15 part of leveling agent, 0.05-0.15 part of thickening agent, 0.2-0.4 part of curing agent, 8-14 parts of solvent and 75-90 parts of copper powder. Through the cooperation of adopting polyurethane modified epoxy and polyester resin in this application, can make copper thick liquid have better adhesion with the base plate, through the solidification back, can form fine copper film circuit on the base plate, polyester resin can improve the solderable tin performance of copper thick liquid moreover, therefore the copper film circuit of preparation can directly go up tin. In the application, the tin-soldering copper paste is used as the circuit silk-screen paste, so that the problems of high cost of the silver paste and silver migration in the silver paste can be solved; the problem of waste water and waste gas caused by preparing the circuit by an etching method can be avoided.

Description

Weldable tin-copper slurry and preparation method and application thereof

Technical Field

The application relates to the technical field of conductive copper paste, in particular to weldable tin-copper paste and a preparation method and application thereof.

Background

The preparation process of the circuit of the present circuit board mainly adopts an etching process, for example, as disclosed in the patent publication No. CN112954899A, "the LED flexible lamp strip circuit board and the preparation method thereof" are that a copper layer is prepared on a substrate to obtain a copper-clad plate, and then circuit manufacturing, development etching, testing, mounting, pressing, welding prevention and surface treatment are carried out on the copper-clad plate; wherein: (1) In the developing and etching process, developing liquid medicine is required to be used for developing, and a large amount of acid etching liquid medicine is also required for etching, so that a large amount of corrosive wastewater can be generated in the operation mode, and the influence on the environment is large; (2) After etching, the covering film is required to be pasted and pressed, and oxidation resistance treatment is required; the whole process is complex and the cost is high. In recent years, with the improvement of the process, the production process of the circuit board tends to develop to replace an etching circuit with a silk-screen circuit; but circuit board circuit and wire are connected and need be realized through the soldering, and the thick liquids that are used commonly at present are mainly soldering tin silver thick liquid, but soldering tin silver thick liquid has following defect: (1) conductive silver paste is costly; (2) problems with silver migration; (3) poor solderability, requiring the incorporation of a large amount of flux; (4) The strong acidity of the soldering flux corrodes the conductive silver paste, so that the silver powder is oxidized, and the powder falls off. The performances of the copper paste and the silver paste are very similar, the cost is lower, and the problem of silver migration does not exist, but the existing copper paste can not realize soldering tin mostly because the copper paste has the defects of high soldering difficulty, low soldering tin fastness and unstable performance.

Disclosure of Invention

In order to improve the solderability and the soldering fastness of the copper paste, the application provides the solderable tin copper paste and a preparation method and application thereof.

In a first aspect, the present application provides a solderable tin-copper paste, which adopts the following technical scheme:

the weldable tin-copper slurry comprises the following raw materials in parts by mass: 4 to 8 portions of polyurethane modified epoxy resin, 1 to 3 portions of polyester resin, 0.05 to 0.15 portion of defoaming agent, 0.05 to 0.15 portion of flatting agent, 0.05 to 0.15 portion of thickening agent, 0.2 to 0.4 portion of curing agent, 8 to 14 portions of solvent and 75 to 90 portions of copper powder.

By adopting the technical scheme, the solder resist ink is generally used before the screen printing of the PCB and the aluminum plate, and the solder resist ink generally adopts an epoxy resin system; the polyurethane modified epoxy resin is adopted, and the epoxy resin can be better combined with an ink base plate, so that the adhesive force between a copper paste layer and a base material can be enhanced; the polyurethane is modified and is mixed with partial polyester resin mainly to play a role in assisting welding, so that the copper paste can be directly soldered after being prepared into a circuit by silk-screen curing.

Preferably, the copper powder is modified copper powder, and the modification method of the copper powder comprises the following steps: placing the nano copper powder in formic acid solution for ultrasonic cleaning treatment to remove an oxide film on the surface, and filtering after the treatment is finished to obtain primary treated copper powder; and then placing the primarily treated copper powder in a DMSO (dimethylsulfoxide) solvent, adding a titanate coupling agent TAC-44 and a catalyst, heating, stirring and reacting, and after the reaction is finished, filtering, washing and drying to obtain the modified copper powder.

By adopting the technical scheme, the copper powder is firstly placed in formic acid for ultrasonic cleaning, so that the copper oxide film on the surface can be removed, and the influence of the copper oxide on the conductivity of the copper oxide film is avoided. The copper powder cleaned by formic acid generates a layer of Cu (COOH) on the surface ₂ And a titanate coupling agent TAC-44 is inoculated into the copper powder, contains a large amount of amino groups, and the amino groups can react with carboxyl on the surface of the copper powder under the action of a catalyst, so that titanate coupling agent groups are grafted on the surface of the copper powder. The titanate coupling agent group can increase the affinity between the copper powder and the polyurethane modified epoxy resin and the polyester resin and improve the wet bonding effect of the contact surface between the copper powder and the resin. After the titanate coupling agent group is grafted, the contact surface of the copper powder and air can be improved and reduced, so that the oxidation resistance of the copper powder is improved. And the titanate coupling agent contains a large amount of amino groups, and can react with groups in polyurethane or polyester resin and a thickening agent in the curing process, so that the bonding property of the copper powder and a substrate is improved.

Preferably, the concentration of the formic acid solution is 3-5%, and the ultrasonic treatment time is 20-30 min; the concentration of the primary modified copper powder in the DMSO solvent is 0.2-0.3 g/mL; the catalyst is DCC (N, N' -dicyclohexylcarbodiimide) or DMAP (4-dimethylaminopyridine); the mass ratio of the primary modified copper powder to the titanate coupling agent TAC-44 to the catalyst is 1 (0.4-0.6) to 0.006-0.008); the heating temperature is 60-80 ℃, and the reaction time is 2-3 h.

By adopting the technical scheme, the oxidation film can be well removed by controlling the concentration of the formic acid solution and the ultrasonic treatment time, and the COOH groups can be formed on the surface of the copper powder through micro-acidification. By controlling the proportion of the components for subsequent reaction and the reaction conditions, more titanate coupling agent groups can be attached to the surface of the copper powder, so that the bonding force between the copper powder and the resin is better improved.

Preferably, the raw materials of the weldable tin-copper slurry also comprise 1-2 parts of antioxidant, and the antioxidant is zinc dialkyl dithiophosphate.

By adopting the technical scheme, the zinc dialkyl dithiophosphate is adopted as the antioxidant, and the zinc dialkyl dithiophosphate has better temperature resistance and can better prevent the copper powder from being oxidized; and the copper powder is an ionic antioxidant, has certain conductivity, and does not reduce the conductive effect of the copper powder. Structurally, it contains S inside ^- With small amount of Cu on the surface of the copper powder ²⁺ Has electrostatic adsorption effect, can improve the binding capacity of the antioxidant and the copper powder, and has better antioxidant effect.

Preferably, the defoaming agent is ten thousand W-195; the leveling agent is TEGO-370 with digao, the curing agent is 1-cyanoethyl-2-ethyl-4-methylimidazole, the thickening agent is acrylic acid, and the solvent is DBE solvent.

By adopting the technical scheme, the 1-cyanoethyl-2-ethyl-4-methylimidazole is adopted as the curing agent in the copper paste curing process, so that the curing effect of the prepared copper paste can be effectively guaranteed, and the stability and the conductivity of the material are improved. Acrylic acid is used as a thickening agent, contains double bonds and carboxylic acid bonds, and can act with active functional groups in polyurethane modified epoxy resin and polyester resin through a curing agent in the curing process, so that the curing effect is enhanced. The solvent is a DBE solvent, has a good solvent effect on polyurethane modified epoxy resin, polyester resin, a thickening agent, a flatting agent and a defoaming agent, has good leveling property, and can increase the softness and adhesive force of the resin.

Preferably, the raw materials of the weldable tin-copper slurry also comprise 0.1-0.2 part of film forming additive, and the film forming additive comprises dimethyl phthalate and ethyl orthosilicate with the mass ratio of 1 (0.2-0.5).

By adopting the technical scheme, the film-forming aid is added, so that the addition of the film-forming aid does not influence the conductivity of the copper powder circuit, but enhances the smoothness of the surface of the copper powder circuit.

In a second aspect, the present application provides a method for preparing a solderable copper paste, including the following steps: adding polyurethane modified epoxy resin and polyester resin into a solvent, and dissolving to obtain a solution A; then adding the other components except the curing agent and the copper powder into the solution A, and fully and uniformly stirring to obtain a solution B; and then adding the curing agent and the copper powder into the solution B, and stirring for 30-60 s at the rotating speed of 1200-1600 rpm to obtain the solderable copper paste.

By adopting the technical scheme and the preparation method, the components can be fully and uniformly mixed, and the components can also be fully mixed.

In a third aspect, the use of a solder copper paste as described herein for the preparation of a copper film circuit for a circuit board.

Preferably, the method for preparing the copper film circuit of the circuit board by using the soldering tin copper paste comprises the following steps:

the method comprises the following steps of firstly priming a substrate with solder resist ink, then placing solder tin copper paste in a screen printing device, carrying out screen printing according to a designed circuit, carrying out curing after the screen printing is finished, and carrying out solder tin after the curing is finished to obtain a copper film circuit on a circuit board.

Preferably, the silk-screen thickness is 40-100 um, the curing temperature is 130-150 ℃, and the soldering tin adopts tin paste or tin wires; the tin paste is printed by adopting tin paste silk screen or is dispensed with tin, and the tin coating temperature is 180-220 ℃; the tin wire is coated with tin at 300-350 ℃ by using complex iron.

By adopting the technical scheme, when the soldering tin paste is used for manufacturing a copper film circuit of a circuit board substrate, compared with the traditional copper foil etching preparation process, the soldering tin paste does not need to use soldering flux, wave soldering, reflow soldering, a tin furnace and the like, can be directly applied with tin, and is simpler and controllable in application process.

In summary, the present application includes at least one of the following beneficial technical effects:

1. through the cooperation that adopts polyurethane modified epoxy and polyester resin in this application, can make copper thick liquid have better adhesion with the base plate, through the solidification back, can form fine copper film circuit on the base plate, polyester resin can improve the solderable tin performance of copper thick liquid moreover, therefore the copper film circuit of preparation can directly go up tin. In the application, the tin-soldering copper paste is used as the circuit silk-screen paste, so that the problems of high cost of the silver paste and silver migration in the silver paste can be solved; the problem of waste water and waste gas caused by preparing the circuit by an etching method can be avoided.

2. In order to further increase affinity and oxidation resistance between copper powder and the resin in this application, carry out modification to the copper powder, through at its surface grafting titanate coupling agent group, thereby can reduce the area of contact of copper powder and air and improve anti-oxidant effect, can promote the cross-section wetting combination effect between its and the resin through the group on the coupling agent, be that the copper powder is better to be embedded into in the resin, promote the cohesion of copper paste and base plate.

3. The zinc dialkyl dithiophosphate is also used as an antioxidant, is an ionic antioxidant and has better high-temperature resistance, and also contains S ^- The ionic group can be connected with Cu on the surface of the copper powder ²⁺ The combination can promote the binding force of the antioxidant and the copper powder, thereby better realizing the antioxidant effect, and compared with other antioxidants, the copper paste has certain conductivity and is beneficial to reducing the conductivity of the copper paste.

Detailed Description

In the embodiment of the invention, a polyurethane modified resin manufacturer is Olin with the model number DER852; the polyester resin manufacturer was Wacker, germany, and was the VINNAPAS C341.

Preparation example 1

Soaking the nano copper powder in a 4% formic acid solution for ultrasonic cleaning for 25min, removing an oxide film on the surface, filtering after the treatment is finished, and washing for 2 times by using DMSO (dimethyl sulfoxide) to obtain primary treated copper powder; then placing the primarily treated copper powder in a DMSO solvent to prepare a dispersion liquid of 0.3g/mL, and adding titanate coupling agents TAC-44 and DCC into the dispersion liquid, wherein the mass ratio of the primarily treated copper powder to the titanate coupling agents and the DCC is 1.005; and heating to 70 ℃, stirring and reacting for 3 hours, and after the reaction is finished, filtering, washing and vacuum drying to obtain the modified copper powder.

Preparation example 2

Soaking the nano copper powder in 3% formic acid solution for ultrasonic cleaning treatment for 30min, removing an oxide film on the surface, filtering after the treatment is finished, and washing for 2 times by using DMSO (dimethyl sulfoxide) to obtain primary treated copper powder; then placing the primarily treated copper powder in a DMSO solvent to prepare a dispersion liquid of 0.2g/mL, and adding titanate coupling agents TAC-44 and DMAP into the dispersion liquid, wherein the mass ratio of the primarily treated copper powder to the titanate coupling agents and the DMAP is 1; and then heating to 80 ℃, stirring and reacting for 2 hours, and after the reaction is finished, filtering, washing and drying in vacuum to obtain the modified copper powder.

Preparation example 3

Soaking the nano copper powder in 5% formic acid solution for ultrasonic cleaning treatment for 20min, removing an oxide film on the surface, filtering after the treatment is finished, and washing for 2 times by using DMSO (dimethyl sulfoxide) to obtain primary treated copper powder; then placing the primarily treated copper powder in a DMSO solvent to prepare a dispersion liquid of 0.2g/mL, and adding titanate coupling agents TAC-44 and DCC into the dispersion liquid, wherein the mass ratio of the primarily treated copper powder to the titanate coupling agents and the DCC is 1.006; and then heating to 60 ℃, stirring and reacting for 3 hours, and after the reaction is finished, filtering, washing and drying in vacuum to obtain the modified copper powder.

Examples 1 to 3

The raw material proportions in examples 1 to 3 can be seen in table 1 (in the table, in parts by mass), and the specific preparation method is as follows:

adding polyurethane modified epoxy resin and polyester resin into a solvent, and dissolving to obtain a solution A; then adding the other components except the curing agent and the copper powder into the solution A, and fully and uniformly stirring to obtain a solution B; and then adding the curing agent and the copper powder into the solution B, and stirring for 45s at the rotating speed of 1500rpm to obtain the solderable copper paste.

TABLE 1

Comparative example 1

Substantially in accordance with example 1, except that in comparative example 1, an epoxy resin was used instead of the urethane-modified epoxy resin.

Comparative example 2

Substantially in accordance with example 1, except that in comparative example 1, no polyester resin was added, and the mass fraction of polyester resin was added to the urethane-modified epoxy resin, that is, 7.4 parts of the urethane-modified epoxy resin was added.

Comparative example 3

Essentially identical to example 1, with the difference that no thickener acrylic acid was added.

The method comprises the steps of priming a substrate with solder resist ink, placing solder copper paste (prepared in the embodiment or the comparative examples 1-3) in screen printing equipment, carrying out screen printing (the screen printing thickness is 50 microns) according to a designed circuit, and curing at 140 ℃ after the screen printing is finished to obtain a copper film circuit.

The conductivity was measured using a four-probe tester.

The adhesion was tested using the cross-hatch tape test method (5A-no peel or coating removal; 4A-traces of peel or coating removal along the direction of the cut; 3A-1.6 mm serration removal along the very beginning cut on each side; 2A-3.2 mm serration removal along the very beginning cut on each side; 1A-removal of coating from most of the X-shaped area under the tape; and complete removal of coating under the 0A-X type area).

Tin is coated on a 320 ℃ tin wire on a copper film circuit, and the tin soldering fastness and the hardness of the copper film circuit are tested.

TABLE 2

As can be seen from the data in Table 2, in examples 1-3, the conductivity, adhesion and soldering properties of the solder paste have certain floating values with the change of the component ratio; the proportion of the components of example 1 and example 2 shows that the copper powder content is reduced, so that the conductivity is increased compared with that of example 1, the proportion of the polyester resin is increased, so that the soldering fastness is improved, and the adhesion is slightly reduced due to the change of other components. The change of the component ratio of the example 1 and the example 3 shows that the copper powder content is increased, so that the electric conductivity is reduced compared with the example 1, the polyester resin content is reduced, and the other components are changed, so that the adhesion and the soldering fastness are reduced to a certain extent. In summary, the overall performance of example 1 is better.

Example 1 compared with comparative example 1, in comparative example 1, the unmodified epoxy resin is used, the conductivity of the epoxy resin is not changed basically, but the adhesion and the solder fastness of the epoxy resin are reduced to a certain extent, which is probably because the polyurethane can increase the binding force between the epoxy resin and the polyester resin and between the epoxy resin and the thickening agent after being modified, so that the adhesion and the solder fastness of the epoxy resin can be improved better.

Example 1 compared with comparative example 2, in comparative example 2, without adding the polyester resin, a significant change in the solder property was observed, which may result in the polyester resin having a soldering aid effect, and thus the solderable tin property of the copper film wiring can be improved.

Example 1 compared with comparative example 3, in comparative example 3, no thickener acrylic acid is added, the conductivity of the acrylic acid is not changed basically, but the adhesion and the solder fastness of the acrylic acid are reduced to a certain extent, which is probably because the acrylic acid can act with the modified epoxy resin and the modified polyester resin, so that the bonding force of the acrylic acid and the modified epoxy resin is improved, and the adhesion and the solder ability of the acrylic acid and the modified polyester resin are improved.

Examples 4 to 6

The component ratios in examples 4 to 6 are shown in table 3, and the specific production method is the same as in example 1.

TABLE 3

The solderable copper pastes of examples 4-6 were tested for resistivity, adhesion and solder fastness with reference to the test methods described above in example 1, and the results are shown in table 4.

TABLE 4

As can be seen from the data in table 4, in example 4, the modified copper powder is used on the basis of example 1, and from the performance, the resistivity, the adhesion and the solder fastness in example 4 are all greatly improved; the reduction of the resistivity may be that the copper powder is treated with formic acid, the surface copper oxide is obviously reduced, and the surface is grafted with titanate coupling agent which contains O-and Ti in terms of the structural formula ⁴⁺ The conductivity of the copper powder is not greatly influenced, so that the conductivity of the copper powder is obviously improved; the adhesion and the soldering fastness of the copper powder are improved probably because the wettability of the interface between the modified copper powder and the polyurethane modified epoxy resin and the polyester resin is improved, so the bonding force is enhanced, and the adhesion and the soldering fastness are obviously improved.

Examples 5 and 6, which use only different proportions and modified copper powders, show small variations in their properties, but maintain the overall good properties.

Examples 7 to 9

The component ratios in examples 7 to 9 are shown in Table 5, and the specific production methods are the same as in example 1.

TABLE 5

The conductivity, adhesion and solder fastness of the solder copper pastes of examples 7 to 9 were measured, and the results are shown in table 6.

TABLE 6

As can be seen from the data in Table 6, the addition of zinc dialkyldithiophosphate causes a slight decrease in the resistivity of the conductive copper paste, has substantially no effect on the adhesion thereof, and causes a slight decrease in the solder fastness; this is probably because the zinc dialkyldithiophosphate itself has a certain conductive property, and after it is adsorbed on the surface of copper powder, the conductivity of the copper powder is increased, and thus its resistivity is reduced to a small extent; while zinc dialkyldithiophosphate addition has a slight effect on solder and thus its solder fastness is slightly lowered.

And (3) stability testing:

priming a substrate with solder resist ink, placing solder copper paste (prepared in examples 4-9) in a screen printing device, performing screen printing (the screen printing thickness is 50 um) according to a designed circuit, and curing at 140 ℃ after the screen printing is finished to obtain a copper film circuit; the prepared copper film circuit was placed at 140 ℃ and 95RH% for 180 hours, and then taken out to test the conductivity, adhesion and solder fastness, and the results are shown in Table 7.

TABLE 7

As can be seen from the data in Table 7, the combination properties of examples 4-6, in which no antioxidant was added, were significantly and substantially reduced after the stability test; however, the performance of examples 7 to 9 was not so much deteriorated, indicating that zinc dialkyldithiophosphate had a good antioxidant effect and contributed to improvement of the stability of the solder copper paste.

Examples 10 to 11

The results of the tests on the conductivity, adhesion and solder fastness of the solder copper pastes in examples 10 to 11 are shown in table 6.

TABLE 8

The conductivity, adhesion and solder fastness of the solder copper pastes of examples 10 and 11 were measured by the above-mentioned methods, and the results are shown in table 9.

TABLE 9

As can be seen from the data in Table 9, the addition of the film-forming aid did not have a significant effect on the performance of the solder paste, but only a slight increase in conductivity.

And (3) testing the smoothness of the copper film circuit surface:

the method comprises the following steps of firstly priming a substrate with solder resist ink, then placing solder copper paste (prepared in examples 7, 8, 10 and 11) in a screen printing device, carrying out screen printing (the screen printing thickness is 50 um) according to a designed circuit, and carrying out curing at 140 ℃ after the screen printing is finished to obtain a copper film circuit.

Testing the surface smoothness of the copper film circuit by a double-tube microscope (when in testing, the mutual position of the illuminating tube and the observation tube is 90 degrees); the criteria are shown in Table 10:

watch 10

Measuring Range average height of irregularity (um)	Surface finish grade
		0.8～1.6	9
1.6～6.3	8～7
		6.3～20	6～5
20～80	4～3

The test results are shown in table 11:

TABLE 11

	Example 7	Example 8	Example 10	Example 11
					Smooth finish	6～5	6～5	8～7	8～7

As can be seen from Table 11, the surface flatness of the copper film wiring was significantly improved after the film-forming assistant was added.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims

1. The weldable tin-copper slurry is characterized by comprising the following raw materials in parts by mass: 4-8 parts of polyurethane modified epoxy resin, 1-3 parts of polyester resin, 0.05-0.15 part of defoaming agent, 0.05-0.15 part of leveling agent, 0.05-0.15 part of thickening agent, 0.2-0.4 part of curing agent, 8-14 parts of solvent and 75-90 parts of copper powder.

2. The solderable tin copper paste of claim 1 wherein the copper powder is modified copper powder and the method of modifying copper powder comprises the steps of: placing the nano copper powder in formic acid solution for ultrasonic cleaning treatment to remove an oxide film on the surface, and filtering after the treatment is finished to obtain primary treated copper powder; and then placing the primarily treated copper powder in a DMSO solvent, adding a titanate coupling agent TAC-44 and a catalyst into the DMSO solvent, heating, stirring and reacting, and after the reaction is finished, filtering, washing and drying to obtain the modified copper powder.

3. The solderable tin copper paste according to claim 2, wherein the concentration of the formic acid solution is 3 to 5 percent, and the ultrasonic processing time is 20 to 30min; the concentration of the primary modified copper powder in the DMSO solvent is 0.2 to 0.3g/mL; the catalyst is DCC or DMAP; the mass ratio of the preliminary modified copper powder to the titanate coupling agent TAC-44 to the catalyst is 1 (0.4 to 0.6) to 0.006 to 0.008); the heating temperature is 60 to 80 ℃, and the reaction time is 2 to 3 hours.

4. The solderable copper paste according to claim 2, characterized in that the solderable copper paste further comprises 1 to 2 parts of an antioxidant, and the antioxidant is zinc dialkyl dithiophosphate.

5. The solderable tin copper paste of claim 1 wherein the defoaming agent is ten thousand W-195; the leveling agent is TEGO-370 with digao, the curing agent is 1-cyanoethyl-2-ethyl-4-methylimidazole, the thickening agent is acrylic acid, and the solvent is DBE solvent.

6. The solderable copper paste according to claim 4, characterized in that the solderable copper paste further comprises 0.1 to 0.2 parts of a film-forming assistant, wherein the film-forming assistant comprises dimethyl phthalate and ethyl orthosilicate in a mass ratio of 1 (0.2 to 0.5).

7. A method for preparing the solderable copper paste according to any one of claims 1 to 6, comprising the following steps: adding polyurethane modified epoxy resin and polyester resin into a solvent, and dissolving to obtain a solution A; then adding the other components except the curing agent and the copper powder into the solution A, and fully and uniformly stirring to obtain a solution B; and then adding the curing agent and the copper powder into the solution B, and stirring for 30-60s at the rotating speed of 1200-1600 rpm to obtain the solderable copper paste.

8. Use of the solder copper paste according to any one of claims 1 to 6 in the preparation of a circuit board copper film circuit.

9. The use of the copper solder paste according to claim 8 for the preparation of copper film circuits for circuit boards, wherein the method for preparing copper film circuits for circuit boards with the copper solder paste comprises the steps of: the method comprises the steps of firstly priming the substrate with solder resist ink, then placing solder tin copper paste in screen printing equipment, carrying out screen printing according to a designed circuit, curing after the screen printing is finished, and soldering tin after the curing is finished to obtain a copper film circuit on a circuit board.

10. The use of the solder copper paste according to claim 9 for preparing a circuit board copper film circuit, wherein the screen printing thickness is 40 to 100um, the curing temperature is 130 to 150 ℃, and the solder adopts solder paste or solder wire; the tin paste is subjected to screen printing or dispensing tin coating, and the tin coating temperature is 180 to 220 ℃; and the tin wire is coated with tin at the temperature of 300 to 350 ℃ by adopting a coated iron.