TWI780965B - Surface treatment method for use in enhancing oxidation resistance of copper powder - Google Patents

Abstract

The present invention discloses a surface treatment method for use in enhancing oxidation resistance of copper powder. According to the surface treatment method, a copper powder and a first modifier are sequentially added into a liquid medium. Next, after evenly stirring the liquid medium, a second modifier is added into the liquid medium so as to ontain a first liquid mixture. Subsequently, after evenly stirring the first liquid mixture, it is utilized suction filtration apparatus to filter a surface-modificated copper powder out of the first liquid mixture. After completing the surface treatment method, the surface-modificated copper powder shows outstanding oxidation resistance.

Description

Surface treatment method to improve the oxidation resistance of copper powder

The invention relates to the technical field of surface treatment/modification, in particular to a surface treatment method for improving the oxidation resistance of copper powder.

As screen printing is widely used in the production of flexible circuit boards and touch panels, the demand for conductive adhesives composed of metal powders, solvents, organic adhesives and dispersants is increasing year by year. Engineers who are familiar with the design and production of conductive adhesives should know that metal powders are usually gold powder, silver powder, and/or copper powder, among which silver has the best conductivity (that is, the lowest resistivity), followed by copper, gold .

Although the conductivity of copper powder is inferior to that of silver powder, as the metal powder in the conductive adhesive, the cost performance of copper powder is higher than that of silver powder. Unfortunately, copper is prone to oxidation, which reduces its conductivity. It is worth noting that, due to the high specific surface area, the electrical conductivity of copper powder is more serious due to oxidation.

In view of this, Taiwan Patent No. I703224 discloses a surface treatment method of copper powder. According to the content disclosed in Taiwan Patent No. I703224, the surface treatment method includes the following steps: (1) Precipitate silver or silver compound by reduction method and cover the surface of copper powder; and (2) Add the silver-coated copper powder to the cyanide solution to obtain the silver-coated copper powder with CN adsorbed on the surface.

Practical experience points out that forming a silver layer with CN adsorbed on the surface of copper powder can indeed effectively improve the oxidation resistance of copper powder. However, it is necessary to purchase specific waste liquid treatment equipment to be able to process the process of manufacturing silver-coated copper powder with CN adsorbed on the surface. The metal-containing cyanide waste liquid produced in the On the other hand, although the price of silver-coated copper powder is lower than that of pure silver powder, it is still higher than that of pure copper powder.

On the other hand, Japanese Patent No. 11-264001 discloses a surface treatment method, which finally coats a fatty acid on the surface of copper powder, thereby improving the oxidation resistance of copper powder. However, practical experience shows that the contact resistance value of copper powder coated with fatty acid is significantly higher than that of pure copper powder, so the conductivity of the conductive adhesive will be reduced.

As can be seen from the above description, the surface treatment method of copper powder in the prior art still has something worthy of improvement. In view of this, the inventor of the present invention made great efforts to research and create, and finally developed a surface treatment method of the present invention to improve the oxidation resistance of copper powder.

The main purpose of the present invention is to provide a surface treatment method for improving the oxidation resistance of copper powder, which is used to modify the surface of a copper powder, thereby improving the oxidation resistance of the copper powder. It is worth noting that the surface-modified copper powder does not contain silver and/or organic acid coating, so it still maintains the advantages of high conductivity and low price.

In order to achieve the above object, the present invention proposes an embodiment of the surface treatment method for improving the oxidation resistance of copper powder, comprising the following steps: (1) Dispersing a copper powder in a liquid medium to form a first mixed solution; (2) adding a first modifying agent into the first mixed solution to form a second mixed solution; (3) uniformly stirring the second mixed solution at a treatment temperature; (4) adding a second modifying agent into the second mixed solution to form a third mixed solution; (5) uniformly stirring the third mixed solution at the treatment temperature; and (6) filtering out the surface-modified copper powder from the third mixed solution by air suction filtration, and then drying the surface-modified copper powder; Wherein, the first modifying agent includes at least one selected from the group consisting of sorbitol solution, xylitol solution and maltitol solution; Wherein, the second modifier includes tetrahydrofuran, toluene, p-xylene, o-xylene, m-xylene, ethyl salicylate, cresol, m-cresol, mercaptan, 2-bromothiophene, At least one of the group consisting of 3-bromothiophene, 2,3,5-tribromothiophene, tetrabromothiophene and chloroform.

In order to more clearly describe a surface treatment method for improving the oxidation resistance of copper powder proposed by the present invention, the preferred embodiments of the present invention will be described in detail below with reference to the drawings.

Please refer to FIG. 1 , which shows a flowchart of a surface treatment method for improving the oxidation resistance of copper powder according to the present invention. The invention proposes a surface treatment method for improving the oxidation resistance of copper powder, which is used to modify the surface of a copper powder so as to improve the oxidation resistance of the copper powder. In a feasible embodiment, the copper powder is made by a process method, and the process method can be a mechanical pulverization method, an electrolytic reduction method or a chemical reduction method. It should be known that in different applications, the plurality of copper particles included in the copper powder will have different shapes, for example: spherical (ball), granular (bead), flake (flake), triangular, polygonal, etc. . Moreover, according to different application requirements, the size of the copper particles may be 75 um, 45 um, 15 um, 10 um, 5 um, 1 um, 0.5 um, 0.1 um, 0.05 um, 0.02 um, 0.015 um, 0.01 um, or 0.005 um. In other words, the surface treatment method of the present invention can be used to modify the surface of copper powder containing spherical, granular, flake-shaped, triangular, or polygonal small-sized copper particles. In more detail, the surface treatment method of the present invention is not suitable for surface modification treatment of bulky copper products such as bulk copper or columnar copper.

As shown in FIG. 1 , the process of the method is to first execute step S1: disperse a copper powder in a liquid medium to form a first mixed solution. According to the design of the present invention, the liquid medium includes a first liquid and a second liquid, wherein the first liquid is ethylene glycol, and the second liquid is selected from glycerin, silicone oil, ethanol, isopropanol, At least one of the group consisting of n-butanol and pentanol. In more detail, the first liquid and the second liquid are mixed according to a volume ratio (v/v) to form the liquid medium, and the volume mixing ratio can be 1:1, 2:1, 2.5:1, 3:1, or 3.5:1. It is worth noting that when performing step S1, the single batch dosage of the copper powder is 60 grams, 80 grams, 100 grams, 125 grams, 150 grams, 200 grams, or 250 grams, and the single batch of the liquid medium The dosage is 3 liters, 3.5 liters, 4 liters, or 4.5 liters.

After step S1 is completed, the method flow is to execute step S2: adding a first modifying agent into the first mixed solution to form a second mixed solution. According to the design of the present invention, the first modifying agent includes a solute and a solvent, wherein the solute is sorbitol, xylitol, maltitol, a mixture of any two of the above, or a mixture of the three above, and the solvent It is ethanol, RO pure water, or deionized water. In other words, the first modifying agent is a sorbitol solution, a xylitol solution, a maltitol solution, a mixed solution of any two of the above, or a mixed solution of the above three. In more detail, in step S2, the first modifying agent has a concentration, and the concentration is 2.5 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, or 25 wt%. Moreover, when performing step S2, the single batch dosage of the first modifying agent is 25 milliliters, 50 milliliters, 75 milliliters, or 100 milliliters.

After step S2 is completed, the method flow is to execute step S3: stirring the second mixed solution uniformly at a processing temperature. In a feasible embodiment, the treatment temperature may be 15°C, 20°C, 25°C, 40°C, 45°C, 50°C, 55°C, or 65°C. Next, the method flow is to execute step S4: adding a second modifying agent into the second mixed solution to form a third mixed solution. According to the design of the present invention, the second modifying agent is tetrahydrofuran, toluene, p-xylene, o-xylene, m-xylene, ethyl salicylate, cresol, m-cresol, mercaptan, 2-bromothiophene, 3-bromothiophene, 2,3,5-tribromothiophene, tetrabromothiophene, or chloroform. In step S4, the second modifying agent has a purity, and the purity is at least 97%. Preferably, the purity is 97-99%. Moreover, when performing step S4, the single batch dosage of the second modifying agent is 100 ml, 125 ml, 150 ml, 200 ml, or 250 ml.

After step S4 is completed, the method flow is to execute step S5: stirring the third mixed solution uniformly at the processing temperature. It is supplemented that, in step S1, the liquid medium and the copper powder are sequentially added into a container of a homogeneous mixer, so as to form the first mixed solution. And, in step S2, the first modifying agent is added into the container, so as to be mixed together with the first mixed solution to form the second mixed solution. Further, in step S4, the second modifying agent is added into the container so as to be mixed together with the second mixed solution to form the third mixed solution. Briefly, the first mixed solution, the second mixed solution and the first mixed solution are all formed in a container of a homogeneous mixer. In a feasible embodiment, the container is made of a material, and the material can be Pyrex glass (Pyrex glass), Duran glass (Duran glass), polystyrene (PP), or polyethylene terephthalate Ethylene formate (PET).

After step S5 is completed, the method flow is to execute step S6: filter out the surface-modified copper powder from the third mixed solution by air suction filtration, and then dry the surface-modified copper powder. To illustrate in more detail, when performing the suction filtration method, ethanol is used as a rinsing solution to clean the surface-modified copper powder.

Experimental sample

Please refer to FIG. 2 , which shows an image of copper powder with high oxidation resistance prepared by the method of the present invention. Moreover, FIG. 3 shows the X-ray diffraction analysis (XRD) spectrum of the copper powder shown in FIG. 2 . Apparently, the XRD data proves that the XRD properties of the copper powder surface-modified by the method of the present invention have not changed.

In summary, after accepting the surface treatment method of the present invention, the surface of the copper powder has been modified, so it has excellent oxidation resistance. It is worth noting that the surface-modified copper powder does not contain silver and/or organic acid coating, so it still maintains the advantages of high conductivity and low price.

Thus, the above has completely and clearly described a surface treatment method of the present invention for improving the oxidation resistance of copper powder. However, it must be emphasized that what is disclosed in the aforementioned case is a preferred embodiment, and all partial changes or modifications derived from the technical ideas of this case and easily deduced by those skilled in the art will not deviate from this case. scope of patent rights.

S1~S6: steps

Fig. 1 is a kind of flowchart of the surface treatment method of the oxidation resistance of promoting copper powder of the present invention; Fig. 2 is the image diagram showing the copper powder with high oxidation resistance made by the method of the present invention; and FIG. 3 is an X-ray diffraction analysis (XRD) spectrum of the copper powder shown in FIG. 2 .

S1~S6: steps

Claims (14)

A surface treatment method for improving the oxidation resistance of copper powder, comprising the following steps: (1) dispersing a copper powder in a liquid medium to form a first mixed solution; wherein, the liquid medium includes a first liquid and A second liquid, the first liquid is ethylene glycol, and the second liquid is at least one selected from the group consisting of glycerin, silicone oil, ethanol, isopropanol, n-butanol, and amyl alcohol or; (2) adding a first modifying agent into the first mixed solution to form a second mixed solution; (3) uniformly stirring the second mixed solution at a treatment temperature; wherein, the treatment temperature is Any one selected from the group consisting of 15°C, 20°C, 25°C, 40°C, 45°C, 50°C, 55°C, and 65°C; (4) adding a second modifying agent Among the second mixed solutions, a third mixed solution is formed; (5) uniformly stirring the third mixed solution at the treatment temperature; The third mixed solution is filtered out, and then the surface-modified copper powder is dried; wherein, the first modifying agent comprises a compound selected from the group consisting of sorbitol solution, xylitol solution and maltitol solution. At least one of them; Wherein, the second modifying agent comprises selected from tetrahydrofuran, toluene, p-xylene, o-xylene, m-xylene, ethyl salicylate, cresol, m-cresol, mercaptan , 2-bromothiophene, 3-bromothiophene, 2,3,5-tribromothiophene, tetrabromothiophene, and at least one of the group consisting of chloroform. The surface treatment method for improving the oxidation resistance of copper powder as described in claim 1, wherein the copper powder is made by a process method, and the process method is selected from mechanical pulverization, electrolytic reduction and Any one of the group formed by the chemical reduction method. The surface treatment method for improving the oxidation resistance of copper powder as described in claim 1, wherein the copper powder includes a plurality of copper particles, and the copper particles have a shape, and the shape is selected from spherical ( Any one of the group consisting of ball, bead, flake, triangle, and polygon. The surface treatment method for improving the oxidation resistance of copper powder as claimed in claim 3, wherein the copper particles have a size, and the size is selected from 75um, 45um, 15um, 10um, 5um, 1um, 0.5 Any one of the group consisting of um, 0.1um, 0.05um, 0.02um, 0.015um, 0.01um, and 0.005um. The surface treatment method for improving the oxidation resistance of copper powder as described in claim 1, wherein, in the step (1), the single batch dosage of the copper powder is selected from 60 grams, 80 grams, 100 grams Any one in the group consisting of grams, 125 grams, 150 grams, 200 grams, and 250 grams. The surface treatment method for improving the oxidation resistance of copper powder as described in claim 1, wherein, in the step (1), the single batch dosage of the liquid medium is selected from 3 liters, 3.5 liters, 4 Liter, and any one of the group consisting of 4.5 liters. The surface treatment method for improving the oxidation resistance of copper powder as claimed in item 6, wherein the first liquid and the second liquid are mixed according to a volume ratio to form the liquid medium, and the volume mixing ratio is selected from Any one of the group consisting of 1:1, 2:1, 2.5:1, 3:1, and 3.5:1. According to the surface treatment method for improving the oxidation resistance of copper powder as described in Claim 1, the first mixed solution, the second mixed solution and the first mixed solution are all formed in a container of a homogeneous mixer. As the surface treatment method for improving the oxidation resistance of copper powder as described in claim 8, the container is made of a material, and the material is selected from pyrex glass (Pyrex glass), Duran glass (Duran glass) glass), polystyrene, and polyethylene terephthalate in any one of the groups. The surface treatment method for improving the oxidation resistance of copper powder as described in Claim 1, wherein, in the step (2), the single batch dosage of the first modifying agent is selected from 25 milliliters, 50 Any one of the group consisting of milliliters, 75 milliliters, and 100 milliliters. The surface treatment method for improving the oxidation resistance of copper powder as claimed in claim 1, wherein the first modifying agent has a concentration, and the concentration is selected from 2.5wt%, 5wt%, 10wt%, 15wt %, 20wt%, and any one of the group consisting of 25wt%. The surface treatment method for improving the oxidation resistance of copper powder as described in Claim 1, wherein, in the step (4), the single batch dosage of the second modifying agent is selected from 100 milliliters, 125 Any one in the group consisting of milliliters, 150 milliliters, 200 milliliters, and 250 milliliters. The surface treatment method for improving the oxidation resistance of copper powder according to claim 1, wherein the second modifying agent has a purity, and the purity is at least 97%. The surface treatment method for improving the oxidation resistance of copper powder as described in claim 1, wherein, when performing the suction filtration method, ethanol is used as a rinsing solution to clean the surface-modified copper powder.

Images