KR101898556B1 - Method for manufacturing Conductive powder with enhanced Heat-resistant - Google Patents

Abstract

The present invention relates to a method for producing a conductive powder with improved heat resistant properties, a conductive powder produced by the method, and a conductor including the conductive powder. The method comprises: an electroless silver plating step of coating silver on a copper powder inside a treating tank; a primary surface treating step of inserting a primary surface treating agent for water repellent coating into a plating solution of the treating tank, and stacking a water repellent coating layer on the surface of a silver coating copper powder; a secondary surface treating step of washing the treated product after the primary surface treating step, mixing the treated material with an organic solvent, and then inserting and stirring a secondary surface treating agent for forming an oxidation resistant layer, thereby stacking an oxidation resistant layer on the surface of the water repellent coating layer; and a washing step of removing a residual liquid on the surface of the treated material after the secondary surface treating step is completed. The conductive powder having improved heat resistant properties and the conductor including the conductive powder according to the present invention include an organic film coating layer having a multi-layered structure. Thus, heat resistant properties are good, and an oxidation reaction due to heat does not occur. Thus, electrical conductivity is not deteriorated when an electronic component is mounted using a reflow or a thermosetting system. Accordingly, excellent reliability is secured. In addition, by means of an organic film coating layer having a water repellent capability, acid resistance and corrosion resistance are secured. Thus, moisture is prevented, and oxidization due to salty water or the like is also prevented. Accordingly, excellent durability and long lifespan are secured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a conductive powder,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive powder having heat resistance, and more particularly, to a conductive powder having a core-shell structure by providing a heat-resistant property to a conductive powder having a core- And a method for producing the powder.

A method of imparting electrical conductivity to an insulating polymeric resin to modify it with a conductive material has been known for a long time. Such methods range from using graphite or applying the effect of acetylene black to dispersing a conductivity imparting agent such as carbon black or graphite powder fiber or metal powder fiber in a synthetic resin.

As the conductivity-imparting agent, gold, silver, copper, aluminum, nickel, zinc, tin, magnesium, a conductive polymer and the like in a powder state are known. However, although gold or silver is excellent in electric conductivity, it has a disadvantage in that it is expensive in itself. In most cases, silver is coated on copper powder which is cheaper than gold or silver.

Recently, electronic parts mounting methods using a reflow and a thermosetting system have been expanded in order to meet the trend of shortening the length and width of electronic products and simplifying the manufacturing process. At this time, conductive powder having a core-shell structure which is cheaper than pure silver powder (99.99% Ag) is often used as a conductive material.

The core-shell conductive powder includes silver coated copper powder, silver coated aluminum powder, silver coated nickel powder, and silver coated graphite powder. Among them, silver-coated copper powder having a variety of shapes compared with the product price and having the best electric conduction characteristic is mainly used.

However, the silver-coated copper powder is vulnerable to heat and has a disadvantage in that the electric conduction characteristic is reduced in the heating temperature in the reflow process or in the heating temperature range of the heat curing system. That is, the heat resistance is not good, and when the heat is applied, the surface is rapidly oxidized and the electrical conductivity is poor.

As a method for compensating for the disadvantages of the silver coated copper powder, it is conceivable to form the silver coating thickness thicker, but thickening the silver coating layer increases the product price. It is urgent to develop a silver-coated copper powder having a thin coating layer and good heat resistance.

No. 10-0628031 (high thermal conductivity carbon sheet using mixed carbon of expanded graphite and carbon nanotubes) Patent Publication No. 93-005895 (Dispersion Enhanced Unsintered Powder Metal Complex and Method for Manufacturing the Same)

The present invention provides a conductive powder having excellent heat resistance and excellent reliability without deterioration of electrical conductivity when electronic components are mounted using a reflow or a thermosetting system since the heat resistance is good and oxidation reaction by heat does not occur. It is an object to provide a method.

In order to achieve the above object, the present invention provides a method for producing a conductive powder having enhanced heat resistance, comprising the steps of: (1) introducing a plating solution and copper powder into a treatment tank in an acid plating step proceeding in a treatment bath having an environment of pH 1 to pH 2 An electroless silver plating step of coating silver on the surface of the copper powder by an electroless plating method, wherein 10 to 20 parts by weight of silver (Ag) is coated per 100 parts by weight of the copper powder to obtain silver coated copper powder; Wherein the step of continuously conducting the electroless silver plating step in the treatment tank in which the electroless silver plating step is carried out is characterized in that in the residual plating liquid after the plating containing the silver-coated copper powder, the first surface treatment agent for water- The method according to claim 1, wherein the silver coating is formed by adding any one of calcium-stearate, potassium-stearate, magnesium-stearate, sodium-stearate or maleic acid, 0.5 to 3 parts by weight per 100 parts by weight of copper powder and stirring for 5 to 15 minutes to form a water-repellent coating layer on the surface of the silver-coated copper powder; Filtering the treated material after the primary surface treatment step to remove the residual liquid on the surface of the treated material, filtering the treated material through a filtration apparatus, washing the treated material with ultrapure water, adjusting the acidity to pH 6.7 to 7.0 A primary filtration and washing step to neutralize; The treated product after the primary filtration and washing step is placed in a secondary treatment tank containing an organic solvent containing methyl alcohol or ethyl alcohol or isopropyl alcohol, and 300 parts by weight of an organic solvent per 100 parts by weight of the treated product Mixing the organic solvent and the organic solvent; A secondary surface treatment step in which an oxidation resistant layer is deposited on the surface of the water repellent coating layer by stirring and stirring a secondary surface treatment agent for forming an oxidation resistant film into the organic solvent mixture in the secondary treatment tank; A secondary filtration and washing step of removing the residual liquid on the surface of the treated water after the completion of the secondary surface treatment step; And a drying step of drying the heat-resistant conductive powder having completed the secondary filtration and washing steps.
Further, the secondary surface treatment agent applied in the secondary surface treatment step may include: Wherein the amount of the second surface treatment agent is one of alkoxysilane, vinylsilane, epoxysilane, methacrylosilane, acrylosilane, aminosilane, chloropropylsilane, mercaptansilane, sulfidosilane and isocyanate silane, Is 0.1 to 5 parts by weight per 100 parts by weight of the silver-coated copper powder.

delete

delete

delete

delete

delete

delete

delete

delete

delete

The conductive powder with enhanced heat resistance characteristics of the present invention as described above has an organic coating layer having a multilayer structure and has good heat resistance properties and does not cause an oxidation reaction due to heat so that a reflow or thermal curing system There is no deterioration of the electric conductivity when the electronic component is used and the reliability is excellent.

Further, since the organic film coating layer having water-repellent ability secures acid resistance and corrosion resistance, it is prevented from being oxidized by salt water or the like as well as being excellent in durability and life span.

1 is a flowchart illustrating a method of manufacturing a conductive powder having enhanced heat resistance characteristics according to an embodiment of the present invention.
Fig. 2 is a diagram schematically showing the manufacturing method shown in Fig. 1. Fig.
FIG. 3 is a cross-sectional view showing the internal structure of the heat-resistant conductive powder produced by the manufacturing method described with reference to FIG.
4A and 4B are views showing an example of a conductor containing the heat-resistant conductive powder of FIG.

Hereinafter, one embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flow chart for explaining a method of manufacturing a conductive powder having enhanced heat resistance characteristics according to an embodiment of the present invention, and FIG. 2 is a diagram schematically illustrating the manufacturing method shown in FIG.

As shown in the drawing, the method for manufacturing a conductive powder having enhanced heat resistance characteristics according to this embodiment includes an electroless silver plating step 101, a primary surface treatment step 102, a primary filtration and washing step 105, A mixing step 107, a secondary surface treatment step 109, a secondary filtration and washing step 111, and a drying step 113.

The above-described manufacturing method is a process for manufacturing the heat-resistant conductive powder of the type shown in Fig. 3 (53 in Fig. 3). As will be described later, the heat-resistant conductive powder 53 may be mixed with a synthetic resin such as resin and then used in a required form, for example, as a conductor 41 as shown in FIG. 4A or as a conductor 47 shown in FIG. . The heat-resistant conductive powder 53 is distributed inside the conductors 41 and 47 to impart conductivity.

First, the electroless silver plating step 101 is an acid plating step performed in an environment of pH 1 to pH 2, in which the plating solution 15 and the core powder 13, that is, the copper powder . The amount of silver used is preferably 10 to 20 parts by weight per 100 parts by weight of the core powder (13). If the content of silver is high, the price of the product rises, which is undesirable.

In addition, the electroless plating step 101 may be performed by a plating method of silver nitrate (AgNO ₃ ), silver chelating silver (AgCN), silver blue germanium (KAgCN ₂ ), and acidic non-cyan plating method. However, there is no limitation on the plating method applied for the electroless plating step (101).

For reference, a silver nitrate plating method or a silver chelating silver plating method can be applied, considering a simpler manufacturing process and a manufacturing cost that can be lowered.

If the process of the electroless silver plating step 101 is completed to some extent and a meaningful reaction no longer occurs, a first surface treatment step (step (1)) of injecting and stirring the first surface treatment agent 21 into the treatment tank 11 103).

The primary surface treatment agent 21 is mixed with the post-plating residual solution 17 and the core shell powder 19 in the treatment tank 11. The residual plating liquid 17 after plating is a liquid in which almost all the silver in the plating liquid 15 is reduced and only the plating catalyst and additives remain. The core shell powder (19) is a powder in the state that the surface of the core powder (13) is plated with silver.

In any case, if the electroless silver plating step 101 has been completed, then the primary surface treatment step 103 is performed. The primary surface treatment step 103 is a step of putting the primary surface treatment agent 21 in the treatment tank 11 (FIG. 2B) and stirring using the stirring device 23. The primary surface treatment agent 21 is a stearate fatty acid, and is laminated on the surface of the core shell powder 19 to impart water repellency.

The amount of the first surface treatment agent 21 may be 0.1 to 10 parts by weight, more preferably 0.5 to 3 parts by weight per 100 parts by weight of the silver-coated copper powder, that is, the core shell powder 19. When the coating amount is less than 0.1 part by weight, the water repellency effect is lowered, and when it is more than 10 parts by weight, the material cost is increased.

The agitation time may vary depending on the volume of the core shell powder, but it may be about 1 minute to 30 minutes, more preferably 5 minutes to 15 minutes.

The first surface treatment agent 21 may be at least one selected from the group consisting of calcium-stearate, potassium-stearate, magnesium-stearate, and sodium-stearate. One or maleic acid can be used.

However, the present invention is not limited to this, and other types of water repellent coating agents may be used as long as the water repellent effect can be realized in a state of being laminated on the surface of the core shell powder 19. [

2C) obtained by laminating the water repellent primary coating layer (53c in FIG. 3) on the surface of the core shell powder 19 through the primary surface treatment step 103, that is, the primary coating powder , Followed by primary filtration and washing (105).

The primary filtration and washing step 105 is a process of suspending the primary coating powder 27 through the filtration device 29 and washing the primary coating powder 27 with ultrapure water to neutralize the primary coating powder 27. That is, the acidic residual liquid remaining on the surface of the primary coating powder 27, such as the plating liquid, is washed away. The pH of the primary coating powder 27 is adjusted to about 6.7 to 7.0 through the filtration and washing step 105.

Then, an organic solvent mixing step 107 is carried out. The organic solvent mixing step 107 is a step of mixing and mixing the primary coating powder 27 in the secondary treatment tank 30 (FIG. 2 (d)) in which the organic solvent 33 is contained. The mixing ratio at this time is 300 parts by weight of the organic solvent per 100 parts by weight of the primary coating powder.

The organic solvent may include methyl alcohol, ethyl alcohol, and isopropyl alcohol. The type of the organic solvent may be appropriately selected according to the work process and the environment.

After the organic solvent mixing step 107 is completed, a second surface treatment step 109 is carried out. The secondary surface treatment step 109 is a step of injecting and stirring the secondary surface treatment agent 31 into the mixed solution 35 of the organic solvent 33 and the primary coating powder 27. The final target heat-resistant conductive powder 53 is obtained through the secondary surface treatment step 109. [

The amount of the secondary surface treatment agent (31) used is 0.1 to 5 parts by weight per 100 parts by weight of the primary coating powder (27). If the amount is less than 0.1 parts by weight, corrosion resistance and oxidation resistance are not improved, and the electrical conductivity of the heat-resistant conductive powder 53 as a final product is poor. If the amount is more than 5 parts by weight, the product price is increased. Further, it is preferable that the progressing time of the secondary surface treatment step 109 is from 5 minutes to 30 minutes.

Anyway, when the secondary surface treatment agent 31 is injected into and agitated in the secondary treatment tank 30, a secondary coating layer 53d is laminated on the outer surface of the primary coating layer 53c (FIG. 3). The secondary coating layer 53d is an oxidation resistant layer for enhancing the heat resistance characteristic.

As the second surface treatment agent 31, there may be used a surface treatment agent such as an alkoxysilane, vinylsilane, epoxysilane, methacrylosilane, acrylosilane, aminosilane, chloropropylsilane, mercaptansilane, sulfide silane, isocyanate silane and the like A silane having a functional group can be used. The above-mentioned silane improves the water resistance, corrosion resistance and oxidation resistance to improve the electrical properties.

For reference, the primary coating powder 27, the organic solvent 33 and the secondary surface treatment agent 31 may be mixed and stirred together in the above-mentioned ratio in the prepared secondary treatment tank 30 as occasion demands.

In any case, if the secondary surface treatment step 109 is completed, secondary filtration and washing step 111 for separating and washing the heat-resistant conductive powder 53 through the filtrate separation process are performed. The mode of the secondary filtration and the water washing step 111 can proceed in the same manner as the primary filtration and the water washing step 105.

Followed by a drying step (113). The drying step 113 is a step of drying the water-repellent heat-resistant conductive powder 53 to remove moisture.

FIG. 3 is a cross-sectional view showing the internal construction of the heat-resistant conductive powder 53 manufactured by the manufacturing method described with reference to FIG.

As shown in the figure, a primary coating layer 53c and a secondary coating layer 53d are laminated in order on the surface of the core shell powder 19. The core shell powder 19 is a core 53a made of copper and a shell 53b made of a silver coating layer.

In addition, the primary coating layer 53c may be a stearate fatty acid or a maleic acid, which is laminated through the primary surface treatment step 103. The fatty acid of the stearate series includes any one of Calcium-Stearate, Potassium-Stearate, Magnesium-Stearate, and Sodium-Stearate .

The secondary coating layer 53d is a layer formed through the secondary surface treatment step 109 as described above and may be formed of a material such as alkoxysilane, vinylsilane, epoxysilane, methacrylosilane, acrylosilane, aminosilane, And a silane having functional groups such as silane, mercaptansilane, sulfide silane and isocyanate silane.

The heat-resistant conductive powder 53 having the above structure has good heat resistance due to the action of the first and second coating layers 53c and 53d, and even if heat is applied to the conductive powder 53, the conductivity does not decrease. For example, even when the heat-resistant conductive powder 53 is used as a connection member of an electric circuit with a high heat generation, good electrical conductivity is maintained.

4A and 4B are diagrams showing examples of conductors 41 and 47 containing the conductive powder of FIG.

The conductors 41 and 47 are conductive members that are thermally fused to an electric circuit in a state in which they are cut or molded in a required circuit pattern and the heat conductive conductive powder 53 is spread evenly therein.

In other words, the conductors 41 and 47 are materials in which the heat-resistant conductive powder 53 is put into the paste-like synthetic resin body and then mixed evenly to uniformly distribute the heat-resistant conductive powder 53. Since the heat-resistant conductive powder 53 is distributed with a uniform density as a whole, the conductors 41 and 47 themselves constitute one conductor.

The kind of the synthetic resin main body can be variously applied as long as it can uniformly disperse the heat-resistant conductive powder 53 therein. For example, polyurethane foams or thermosetting silicone resins as well as the above-mentioned resins can be used.

In the case of Fig. 4A, the conductor 41 takes the form of a sheet having a certain thickness. The sheet-like conductor 41 is connected to a circuit formed on the circuit board 51 to allow the circuit to operate.

Particularly, even if a lot of heat is generated due to the characteristics of the circuit, the characteristic change of the conductor 41 does not occur. This is because the first and second coating layers 53c and 53d of the core shell powder 19 have heat resistance. Further, the conductor 41 can be directly fixed on the circuit board 51 by a heat fusion method. It is not necessary to use an adhesive or the like.

Further, when the polyurethane foam is used as the synthetic resin main body, since the conductor 41 has impact absorbability in addition to electrical conductivity, it also provides a function of absorbing impact applied to the circuit and shielding electromagnetic waves.

Referring to FIG. 4B, a conductor 47 is applied between the circuit boards 51 which are spaced apart from each other. The conductor 47 is applied to the upper surface of the silicon body 48 having an elastic force and energizes the upper and lower circuit boards 51.

Particularly, although the conductor 47 is mounted on the circuit board 51 in a reflow manner, there is no change in electrical characteristics. That is to say, the resistance of the conductor 47 does not increase. It is needless to say that the thermal resistance of the heat-resistant conductive powder contained in the conductor 47 does not increase.

(Example) Preparation of Silver Coated Copper Powder with Enhanced Heat Resistance

The surface of the copper core was coated with silver (Ag) by an electroless plating method using silver nitrate (AgNO ₃ ). At this time, 15 parts by weight of silver was used per 100 parts by weight of the copper core.

For the first surface treatment of the silver-coated copper powder prepared by the above procedure, the silver-coated powder was added to sodium-stearate and further stirred for 10 minutes, followed by surface treatment and filtration. The sodium stearate was used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the silver-coated copper powder.

Thereafter, the filtrate-separated product was mixed with 300 g of an organic solvent (methyl alcohol), 1 mol% of melacaptosilane (Momentive, A-189) was added and reacted for 15 minutes to obtain silver coated copper The powder was separated by filtration and dried.

(Comparative Example) Production of silver-coated copper powder without surface treatment for heat resistance

The electroless plating method using silver nitrate (AgNO ₃ ) was used to coat the surface of the copper core with silver (Ag) and then dried. At this time, 15 parts by weight of silver was used per 100 parts by weight of the copper core, and no additional coating operation was performed.

Table 1 shows changes in the electrical conductivity characteristics of the silver-coated copper powder prepared by the above Examples and Comparative Examples and the silver-coated copper powder produced by competitors A and B at home and abroad.

manufacturer Heat-cured silicone resin formulation After drying, sheet resistance After 250 ° C x 10 minutes, the sheet resistance (Example) 5mΩ / □ 8mΩ / □ (Comparative Example) 7mΩ / □ 20Ω / □ Domestic competitors (A) 6mΩ / □ 1Ω / □ Overseas competitors (B) 5mΩ / □ 20mΩ / □

As shown in Table 1 above, in the case of (Example), the resistance value at the time of heating for 10 minutes at a temperature of 250 占 폚 did not significantly increase as compared with the sheet resistance value at the time of not heating.

This is because, in the case of domestic competitors (A) and domestic competitors (B), a large increase from 20 mΩ / □ to 20 mΩ / □, from 6 mΩ / □ to 1 Ω / □ from 7 mΩ / This is a very meaningful result.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

11: Treatment tank 13: Core powder 15: Plating solution
17: residue after plating 19: core shell powder 21: primary surface treatment agent
23: stirring device 27: primary coating powder 29: filtration device
30: Second treatment tank 31: Second surface treatment agent 33: Organic solvent
35: mixture liquid 41: conductor
47: conductor 48: silicon body
51: circuit board 53: heat-resistant conductive powder 53a: core
53b: shell 53c: primary coating layer 53d: secondary coating layer

Claims (11)

A plating solution and a copper powder are put in a treating tank and coated with silver on the surface of the copper powder through an electroless plating method, wherein 100 parts by weight of copper powder An electroless silver plating step of coating 10 to 20 parts by weight of silver (Ag) with silver to obtain a silver-coated copper powder;
Wherein the step of continuously conducting the electroless silver plating step in the treatment tank in which the electroless silver plating step is carried out is characterized in that in the residual plating liquid after the plating containing the silver-coated copper powder, the first surface treatment agent for water- The method according to claim 1, wherein the silver coating is formed by adding any one of calcium-stearate, potassium-stearate, magnesium-stearate, sodium-stearate or maleic acid, 0.5 to 3 parts by weight per 100 parts by weight of copper powder and stirring for 5 to 15 minutes to form a water-repellent coating layer on the surface of the silver-coated copper powder;
Filtering the treated material after the primary surface treatment step to remove the residual liquid on the surface of the treated material, filtering the treated material through a filtration apparatus, washing the treated material with ultrapure water, adjusting the acidity to pH 6.7 to 7.0 A primary filtration and washing step to neutralize;
The treated product after the primary filtration and washing step is placed in a secondary treatment tank containing an organic solvent containing methyl alcohol or ethyl alcohol or isopropyl alcohol, and 300 parts by weight of an organic solvent per 100 parts by weight of the treated product Mixing the organic solvent and the organic solvent;
A secondary surface treatment step in which an oxidation resistant layer is deposited on the surface of the water repellent coating layer by stirring and stirring a secondary surface treatment agent for forming an oxidation resistant film into the organic solvent mixture in the secondary treatment tank;
A secondary filtration and washing step of removing the residual liquid on the surface of the treated water after the completion of the secondary surface treatment step;
And a drying step of drying the heat-resistant conductive powder after completion of the secondary filtration and washing steps. delete delete The method according to claim 1,
Wherein the secondary surface treatment agent applied in the secondary surface treatment step comprises:
Wherein the silane coupling agent is any one of alkoxysilane, vinylsilane, epoxysilane, methacrylosilane, acrylosilane, aminosilane, chloropropylsilane, mercaptansilane, sulfide silane and isocyanate silane,
Wherein the amount of the secondary surface treatment agent is 0.1 to 5 parts by weight per 100 parts by weight of the silver-coated copper powder. delete delete delete delete delete delete delete

Images