WO2008130080A1

WO2008130080A1 - Manufacturing method of conductive electroless plating powder

Info

Publication number: WO2008130080A1
Application number: PCT/KR2007/004101
Authority: WO
Inventors: Won Il Son; Jeong Hee Jin; Seok Heon Oh
Original assignee: Hanwha Chemical Corporation
Priority date: 2007-04-23
Filing date: 2007-08-27
Publication date: 2008-10-30
Also published as: TW200916235A; KR20080095033A; KR100879578B1; TWI422444B

Abstract

The present invention relates to a manufacturing method of conductive electroless plating powder having excellent conductivity and adhesion, more precisely a manufacturing method of conductive plating powder based on electroless plating method which includes the step of forming a metal plating layer on the surface of substrate of resin powder in electroless plating solution. Herein, the plating layer has micro protrusions of 0.3-1.0 μm on the surface and the area where protrusions are not formed is also plated smoothly and evenly, so that the obtained conductive plating powder has excellent electric resistance, adhesion between the elaborate plating layer and the resin powder and regularity.

Description

[DESCRIPTION]

[invention Title]

MANUFACTURING METHOD OF CONDUCTIVE ELECTROLESS PLATING POWDER

[Technical Field]

The present invention relates to a manufacturing method of conductive electroless plating powder having excellent conductivity and adhesion, more precisely a manufacturing method of protrusion type conductive plating powder based on electroless plating method, in which 0.3-1.0 [M sized micro protrusions are on the plating layer and the area without protrusions is plated smoothly, resulting in the excellent electric resistance, adhesion between the plating layer and resin plating powder and regularity.

[Background Art]

Conductive resin powders have been widely used for preventing static electricity of an electronic machine or its parts, for absorbing electric waves or for forming an electromagnetic shied. Recently, plating powder has been used as a conductive material for electric connection of micro- parts of electronic equipment, for example connection between electrode of LCD panel and circuit board of LSI chip, and connection between electrode terminals of micro pitch, etc. The conventional manufacturing method of plating powder is generally exemplified by physical coating of resin powder surface with metal particles (Japanese Patent Application No. 1993-55263) and a method of laying protrusions of metal particles on the surface of the substrate powder (Japanese Patent Application No. 2002-55952) . However, a manufacturing method of plating powder using electroless plating has been a major alternative these days (Japanese Patent Application No. 2003-103494, No. 2003-57391, No. 2001-394798, etc). The conductive plating powder obtained from the conventional methods such as gold, silver and nickel, has a problem of high electric resistance under low connection pressure during the connection of electrode terminals of micro pitch. With the rapid advance and development of electronic machines, low connection resistance is required. To reduce connection resistance, conductive particles having protrusions on their surfaces were proposed (Japanese Patent Publication No. 2003-234020) . For example, in electroless nickel plating with non-conductive particles, autolysis of nickel plating solution was used to produce conductive electroless plating powder by forming micro protrusions and nickel membrane simultaneously. However, according to this method, protrusions turn into a clod of nickel and the control of the size, shape and numbers of the clod is very difficult, in addition to the difficulty in reducing connection resistance owing to insufficient resin exclusion by protrusions. Therefore, alternative conductive minute particles have been reported that contain 0.02-0.3 /M sized micro protrusions in parallel with the outmost layer of the conductive metal layer and the ratio of the micro protrusions of up to 0.1 μm takes at least 80%, to facilitate the exclusion of resin and have high connection reliability (Japanese Patent Publication No. 2004-296322) . And the conductive minute particles covered with protrusions by 70-90% of the surface have also been reported (Japanese Patent Publication No. 2006-228474) . In the meantime, a method for manufacturing conductive particles characterized by having protrusions as a coagulation of bulk particles on the conductive layer and the protrusion density is 25-50/conductive particle has been reported (Japanese Patent Publication No. 2006-302716) . According to the above description on the method above, at least 80% of the micro protrusions has 0.02-0.3 βm. size. Most of the micro protrusions are up to 0.3 //m in height. When it is tried to conduct electricity between electrodes of LCD board with weak weight, point contact in which only micro protrusions are connected is no made. Besides, in spite of excellent connection stability, insufficient resin exclusivity interrupts reliable electric resistance.

Korean Patent No. 0602726 describes a method of electroless conductive plating, in which nickel or nickel alloy membrane is formed on the surface of spherical core particle of 1-20 μm in mean diameter by electroless plating and micro protrusions of 0.05-4 μm are formed on the outmost layer of the membrane and the micro protrusions form a continuous membrane which comprising micro protrusions and nickel membrane at the same time. Particularly, this method is the electroless nickel plating on non-conductive particles which is to produce conductive electroless plating powder by forming nickel micro protrusions and nickel membrane simultaneously based on autolysis of nickel plating solution. However, according to this method, it is very difficult to control the shape and numbers of protrusions and to reduce connection resistance because resin exclusion by protrusions is not sufficient and the plating layer without protrusions is rather rough and irregular with forming porous. When the plating layer which is irregular and porous is plated with gold by displacement gold plating, the plating layer is apt to be peeled off, resulting in irregular gold plating layer. Thus, it is difficult to reduce connection resistance.

According to the rapid advance of electronic machines and miniaturization of electronic parts, for example wiring on a board, etc, becomes minuter. So, conducting powder having high conductivity and excellent adhesion between metal coating layer and resin powder is required.

Therefore, the present inventors studied to develop conductive electroless plating powder having excellent conductivity and adhesion. As a result, the present inventors completed this invention by developing a manufacturing method of conductive plating powder based on electroless plating method forming metal plating layer on the surface of the substrate of resin powder in electroless plating solution, which favors the production of conductive plating powder having excellent adhesion between the plating layer and the resin powder and regularity as well as excellent electric resistance resulted from that the plating layer has 0.3~1. Ojtan sized micro protrusions on its surface and the area without protrusions is plated smoothly.

[Disclosure]

[Technical Problem]

It is an object of the present invention to provide a manufacturing method of conductive electroless plating powder having so excellent conductivity and adhesion that it can cope with the request of micro wiring, provide satisfactory resin exclusion by protrusions during connection and give high conductivity. The conductive electroless plating powder prepared by the method of the present invention has excellent conductivity and adhesion in which the first metal plating layer contains 0.3-1.0 βm sized micro protrusions and the rest area of the layer without protrusions is plated smoothly. It is another object of the present invention to plate the first metal plating layer and micro protrusions with different metals.

[Technical Solution]

To achieve the above objects, the present invention provides a manufacturing method of conductive electroless plating powder comprising the steps of forming the first metal plating layer by plating the surface of resin powder used as a core material; forming metal protrusions by using the same or a different metal; and forming the second metal plating layer by plating the protrusions and the upper part of the first metal plating layer without protrusions with the same or a different metal.

It is preferred that the first metal plating layer and the protrusions are plated with different metals. As shown in Figure 1, the protrusion type conductive plating powder of the present invention comprises: core material (1) using resin powder; first electroless metal plating layer (2) plated on the surface of the core material (1); transition metal protrusions (3) formed on top of the first electroless metal plating layer (2); and second electroless metal plating layer (4) plated on the protrusions (3) and on the top of the first electroless metal plating layer (2) . If necessary, the protrusion type conductive plating powder can additionally include the gold plating layer (5) formed on the top of the second electroless metal plating layer (4) .

The plating powder of the present invention is characterized by forming 0.3-1.0 μm sized spherical protrusions (3) on Η of the surface at least 5 and forming smooth plating layer where protrusions are not formed.

Hereinafter, the manufacturing method of plating powder of the present invention is described in detail.

The present invention provides a manufacturing method of protrusion type conductive plating powder, in which the first electroless metal plating layer is formed on the surface of a core material using resin powder based on electroless plating; and transition metal protrusions are formed on the surface of the resin powder by simultaneous addition of transition metal and a reducing agent.

It is preferred in this invention that different metals are used for the transition metal protrusions and for the first electroless metal plating layer.

It is possible to include the additional step of forming the second electroless metal plating layer on the top of the transition metal protrusions and on the top of the first electroless metal plating layer without protrusions with the same or a different metal from the metal used for the first electroless metal plating layer based on the electroless plating method. And it is also possible to include the additional step of forming gold plating layer on the top of the second electroless metal plating layer.

To form the gold plating layer, the conductive plating powder coated with the second electroless metal plating layer is dispersed in displacement gold plating solution to induce displacement gold plating; and the displacement gold plating solution is regulated as alkali, to which a reducing agent is added in order to form the reduced gold plating layer on the displacement gold plating layer. As a result, the gold plating layer is formed precisely and regularly, and the metal of the first electroless metal plating layer is prevented from being eluted. The preferable alkali condition herein indicates pH 10 - 14.

The components used for the present invention are described in more detail hereinafter. As explained hereinbefore, the present inventors found out that the method of forming metal plating layer on the surface of resin powder by electroless plating can produce conductive plating powder having excellent regularity and adhesion between the plating layer and the resin powder because the plating powder has 0.3-1.0 μm sized micro protrusions and the area where protrusions are not generated is plated very smoothly. And the inventors further completed this invention by confirming that the method of the invention has advantages of sufficient resin exclusion by protrusions during micro-connection of electrode and high conductivity.

In this invention, the resin used for the electroless plating core material is not limited. For example, it is preferred to select a resin or a mixture of at least two selected from the group consisting of polyolefin such as polyethylene, polyvinylchloride, polypropylene, polystyrene and polyisobutylene; olefin copolymer such as styrene- acrylonitrile copolymer and acrylonitrile-butadiene-styrene terpolymer; acrylic acid derivative such as polyacrylate, polymethylmethacrylate and polyacrylamide; polyvinyl compound such as polyvinylacetate and polyvinylalcohol; ether polymer such as polyacetal, polyethyleneglycol, polypropyleneglycol and epoxy resin; amino compound such as benzoguanamine, urea, thiourea, melamine, acetoguanamine, dicyan amide and aniline; aldehydes such as formaldehyde, palladiumformaldehyde and acetaldehyde; polyurethane; and polyester. According to the present invention, the mean diameter of resin powder is 0.5 ~ 1000 μm. It the mean diameter is less than 0.5 μm, it will be hard for the conductive powder to contact the electrode. If there is a gap between electrodes, contact fail will be observed. If the mean diameter is more than 1000 μm, micro conductive connection will be difficult.

Therefore, the mean diameter has to be in that range and 1 ~

100 μm is preferred, 2 ~ 20 μm is more preferred and 3 ~ 10 μm is most preferred.

The aspect ratio of the resin powder, in this invention, is less than 2, and more preferably less than 1.2 and most preferably less than 1.06. If the aspect ratio is larger than 2, particle diameter will not be regular, suggesting that when the conductive powders are forced to contact electrode, the numbers of non-contacting particles are increased. Therefore, the ratio is preferably limited to the above and more preferably limited to the range of 1-2.

The preferable coefficient of variation (Cv) of the rein particle diameter is up to 30%, preferably up to 20%, more preferably up to 10% and most preferably 1-30%. If the Cv is more than 30%, particle diameter is not regular, so that the contact of the conductive powder to the electrode is difficult, suggesting that the numbers of non-contacting particles increase. So, Cv has to be adjusted in the above range. Herein, Cv is the value defined as the following mathematical formula 1. [Mathematical Formula 1] Cv(%) = (σ/Dn)^χ 100

(Wherein, σ is standard deviation of particle diameter and Dn is number average mean diameter.)

The standard deviation and number average mean diameter can be calculated by particle size analyzer (Accusizer model 780-particle sizing systems, Inc) .

According to the present invention, the first metal layer is formed on the surface of the resin powder substrate by electroless plating method, and the transition metal solution reduced by a reducing agent is added thereto in order to generate protrusions on the first metal plating layer. As a result, the transition metal is reduced on the first metal plating layer. Then, the second electroless plating layer is formed on the reduced transition metal protrusions and on the first electroless nickel plating layer to produce the protrusion type conductive ball.

Particularly, to form the first plating layer, the resin substrate particle is added into SnCl₂ solution, by which Sn²⁺ ion is adhered on the surface of the resin substrate. Then, Pd is reduced on the surface of the resin substrate by using PdCl₂ solution to form catalytic nuclei, resulting in the formation of the first plating membrane layer.

The metal used for forming the first plating membrane layer is any of conductive metals that are appropriate for electroless plating, for example Au, Ag, Co, Cu, Ni, Pd, Pt and Sn or an alloy thereof. The double or multiple plating layers with two or more different metals can also be formed. The preferable metal membrane layer is Ni membrane layer. Ni membrane layer has excellent adhesion with resin substrate particle and is able to form the electroless plating membrane layer having excellent peel resistance. The allowed thickness of the membrane layer is 10 ~ 100 ran, but not always limited thereto .

To generate protrusions after forming the first membrane layer, different metals from those used for forming the first membrane layer are preferably used as a transition metal. For example, the transition metal is selected from the group consisting of Pd, Cu, Ru, Pt, Ag, Co and an alloy thereof, which are usable as catalytic nuclei of the second electroless plating. The double or multiple plating layers with two or more different metals can also be formed. The concentration and the amount of addition of the metal solution for plating are associated with the size and the number of protrusions. It is preferred for the metal solution to contain transition metal by 0.01~100 g/L. If the content of transition metal is too low, eduction of the transition metal will be difficult and the size of the protrusions will be too small. If the content is more than 50 g/L, the size of the protrusions will be larger but costs will also be increased. So, the preferable content is determined as 0.01~50 g/L and more preferably determined as 0.1g~20 g/L. The reducing agent for the transition metal is not limited and any reducing agent that is able to reduce the transition metal solution can be accepted. For example, one or more compounds selected from the group consisting of erythorbic acid compound, hydrazine compound, hydroquinone compound, boron compound and phosphoric acid compound or their salts can be used as the reducing agent.

The addition of such reducing agent favors the generation of transition metal protrusions having excellent stability with favored eduction speed. The erythorbic acid compound is exemplified by L-ascobic acid salts, the hydrazine compound is exemplified by P- hydrazine benzenesulfonic acid and hydrazine sulfate derivatives, the hydroquinone compound is exemplified by methyl hydroquinone, chlorohydroquinone and methoxy hydroquinone, the boron compound is exemplified by sodium borohydride and dimetyl amino bromide, and the phosphoric acid compound is exemplified by sodium hyperphosphite and pyrophosphite .

The reducing agent and the reducing agent derivatives of the invention can be used independently or as a mixture of at least two compounds. The content of the reducing agent in the plating solution of the invention is not limited. But if the content of the reducing agent is too low, eduction of the transition metal will be difficult and costs will be increased too much. Therefore, the preferable content of the reducing agent in the total plating solution is 0.01-50 g/L and 0.1g~20 g/L is more preferred.

The preferable temperature for the formation of protrusions by transition metal is at least 40^°C. However, if the temperature is too high, the plating solution might be degraded and water will be evaporated badly, suggesting that the contents of components of the plating solution will be changed. So, the temperature of the plating solution is preferably adjusted to 20~80^°C. pH of the plating solution is regulated as pH 3~14 with the addition of a reducing agent. If the pH is lower than 3, the metals will be eluted from the first membrane layer, indicating that the metal layer will be destroyed, plating will be irregular, protrusions will not be generated on the surface of the resin powder or the protrusion generation will be irregular by the alloy generated by the combination of the eluted metal and the transition metal, and thus connection resistance will be increased. On the contrary, if the pH is higher than 14, the amount of a pH regulator has to be increased with reducing the effect. Therefore, the pH is preferably regulated as 3-14 and more preferably as 5-12. The pH regulator can ^'be inorganic salt, for example sodium hydroxide, ammonium chloride, etc. The content of the pH regulator in the plating solution is preferably 10-200 g/L.

In the step of forming the second electroless nickel plating layer on the surface of the transition protrusions and the first electroless plating layer, the plating powder can be used as a substrate to form at least two metal layers on top of the plating membrane layer. For example, Au layer can be formed easily on the top of Ni membrane layer, which favors connectivity with the plating membrane layer. The Ni-Au double membrane layers provide higher conductivity than the single membrane layer. The thickness of the single membrane layer is 10 - 200 ran, and the thickness of the double membrane layers is 10 - 300 ran, but not always limited thereto.

The conductive plating powder prepared by the method of the present invention has excellent conductivity and adhesion between the plating layers, which satisfy the request of micro wiring, and is high quality and high value plating powder which is not limited by capacitance during connection.

[Advantageous Effects]

As explained hereinbefore, the protrusion type conductive plating powder of the present invention is characterized by regular shaped and sized protrusions and excellent resin exclusion during thermo-compression to electrode by anisotropic conductive film because the protrusions are regular and the area where protrusions are not formed is smoothly plated; excellent connection reliability with electrode; and excellent adhesion between the elaborated plating layer and the resin powder and excellent regularity.

Therefore, the present invention provides high quality conductive electroless plating powder that can satisfy the need of micro wiring without limitation by capacitance during connection.

[Description of Drawings]

The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

Figure 1 is a cross-section showing the example of the conductive electroless plating powder of the present invention. Figure 2 is a photograph of SEM (x 6,000) showing the surface of the plating powder prepared in example 1 of the invention.

Figure 3 is a photograph of SEM (x 20,000) showing the surface of the plating powder prepared in example 1 of the invention. Figure 4 is a photograph of SEM (x 6,000) showing the surface of the plating powder prepared in example 2 of the invention.

Figure 5 is a photograph of SEM (x 10,000) showing the surface of the plating powder prepared in example 2 of the invention.

Figure 6 is a photograph of SEM (x 6,000) showing the surface of the plating powder prepared in example 3 of the invention.

Figure 7 is a photograph of SEM (x 18,000) showing the surface of the plating powder prepared in example 3 of the invention.

Figure 8 is a photograph of SEM (x 6,000) showing the surface of the plating powder prepared in example 4 of the invention . Figure 9 is a photograph of SEM (x 20,000) showing the surface of the plating powder prepared in example 4 of the invention.

Figure 10 is a photograph of SEM (x 10,000) showing the surface of the plating powder prepared in comparative example 1 of the invention.

Figure 11 is a photograph of SEM (x 20,000) showing the surface of the plating powder prepared in comparative example

2 of the invention.

Figure 12 is a photograph of SEM (x 8,000) showing the surface of the plating powder prepared in comparative example 2 of the invention.

Figure 13 is a photograph of SEM (x 6,000) showing the surface of the plating powder prepared in comparative example

3 of the invention.

Figure 14 is a photograph of SEM (x 20,000) showing the surface of the plating powder prepared in comparative example 3 of the invention.

1 : core material 2 : first electroless metal plating layer 3 : transition metal protrusions 4 : second electroless metal plating layer

5 : gold plating layer

[Best Mode]

Hereinafter, the manufacturing method of the conductive plating powder having excellent conductivity and adhesion is described in detail, but the following examples cannot limit the spirit and scope of the present invention.

[Manufacturing Example] <Pretreatment of resin powder>

Acrylic powder (mean diameter: 3.6 μm, Cv: 5%, aspect ratio: 1.06, methacrylic acid: triethylene glycol dimethacrylate = 20:80 (weight ratio), weight average molecular weight: 30,000) was used. 30 g of the powder was dispersed in a mixed solution comprising CrO₃ 10 g, sulfuric acid 200 g and ultra fine water 1000 g, followed by treatment with ultrasonic cleaner for 30 minutes.

After the ultrasonic treatment, the mixture was deposited at 60^°C for 10 minutes, followed by washing with de-ionized water. After washing, the mixture was deposited in SnCl2 solution (1.0 g/i) for 3 minutes, followed by washing with cold de-ionized water. After depositing in PdCl2 solution (0.1 q/t) for three minutes again, the mixture was washed with cold de-ionized water several times to give slurry. <First electroless nickel plating> 0.5 M NaH₂PC^ solution was prepared in 1 L of dispersion. Temperature was raised to 60^°C, to which 30 g of the slurry was added with stirring. 50 ml. of 1 M nickel sulfate solution and 2 M NaH₂PO₄ (reducing agent) were slowly added thereto by using a micro quantifying pump for 10 minutes at the speed of 3

Upon completion of the addition of nickel sulfate and the reducing agent, the reaction solution was stirred at high speed until hydrogen foaming stopped. Temperature was maintained at 60 ^°C and pH was maintained at 6.0 to carry out electroless nickel plating. The thickness of the nickel plating layer was approximately 15 nm. Then transition metal protrusions were generated. [Example 1]

<Generation of transition metal protrusions> 0.5 g of Pd CI₂, the transition metal, was dissolved in 500 g of ultra pure water in the first nickel plating dispersed solution. 10 g of hydrazine, the reducing agent, was diluted in 500 g of ultra pure water. pH was regulated as 6.0. 200 g of each solution was added simultaneously to generate Pd protrusions on the first electroless nickel plating powder. The size of the Pd protrusion was 10 run at average. <Second electroless nickel plating>

The first electroless nickel plating powder having Pd protrusions on its surface was plated with electroless plating solution (Union 440, Union Specialty) . The electroless plating solution was divided into solution A (IM, nickel sulfate) and solution B (reducing agent, 2M, NaH₂PO₄) , which were slowly added by using a micro quantifying pump at the speed of 3 m^/min for 80 minutes. Upon completion of the addition of nickel sulfate and the reducing agent, the second electroless nickel plating layer was formed with stirring at the same temperature until hydrogen foaming stopped. The obtained nickel plating powder was washed several times, substituted with alcohol, and vacuum dried at 80^°C to give nickel plating powder. The thickness of the nickel plating layer was approximately 120 ran.

The results are shown in Table 1. Figure 2 is a photograph of SEM showing the surface of the plating powder prepared in example 1 (x 6000) to confirm regularity of protrusion distribution. Figure 3 illustrates the sizes and numbers of protrusions on the ^ of the surface of the metal particle (x 20,000) . In the photograph showing the surface of the nickel ball having Pd adhered irregularly, the protrusion size was 280~400 nm and the size of the largest protrusion was approximately 600 nm. The area of the surface where protrusions were not generated was plated evenly. The size and number of protrusion and electric resistance and adhesion were investigated and the results are shown in Table 1. [Example 2]

The pretreatment process was performed by the same manner as described in example 1 and the first and the second electroless nickel plating were also performed by the same manner as described above. The difference was that 1 g of H₂PtCl₆ was used as a transition metal, which was dissolved in 500 g of ultra pure water and the reducing solution of example 1 was used as a reducing agent to generate protrusion type conductive balls by forming Pt protrusions on the first electroless nickel plating layer. The results are shown in Figure 4 and Figure 5. The sizes and numbers of the protrusions on the ^ of the surface of the metal particle were measured using SEM photograph (x 20K) and electric resistance and adhesion were investigated. The results are shown in Table 1. [Example 3]

Displacement gold plating solution was prepared by dissolving 10.0 g of potassium gold cyanide, 150 g of ethylenediaminetetraacetic acid and 70 g of ammonium citrate completely in 3 L of de-ionized water. At that time, pH was

5.2. Temperature of the plating solution was raised to 60 ^°C , to which 20 g of the nickel plating powder prepared from the above nickel plating process was added, followed by dispersing with stirring for 10 minutes. The thickness of the gold layer was regulated as 0.08 μm. pH was regulated to be 13.0 by adding 10 M NaOH solution using a quantifying pump. 10 g of hydrazine 2 hydrate (98%) used as a reducing agent was added by using a micro quantifying pump at the speed of lg/min for 10 minutes. The reaction continued for 35 minutes. The concentration changes of nickel and gold over the time of gold plating are shown in Figure 1.

The obtained plating powder was washed with 1 L of de- ionized water 5 times, followed by substitution with alcohol to eliminate the remaining moisture completely. Then, the powder was vacuum-dried at 80^°C to give gold plating powder.

The gold plating powder obtained above was cut by FIB (Forced Ion Beam) and the section was observed under SEM. The thickness of the gold plating layer was approximately 20 ran.

The surface of the gold plating powder prepared above was observed under SEM and the photographs of x 6000 and x 18,000 were taken and shown in Figure 6 and Figure 7. The sizes and numbers of the protrusions on the H of the surface of the metal coated plating powder were measured and the electric resistance and adhesion were also investigated. The results are shown in Table 1. [Example 4]

Gold plating was performed by the same manner as described in example 3 except that the protrusion type nickel plating powder produced in example 2 was used.

The obtained plating powder is shown in Figures 8 and 9. The sizes and numbers of the protrusions on the H of the surface of the gold coated plating powder were measured and the electric resistance and adhesion were also investigated. The results are shown in Table 1. [Comparative Example 1] An experiment was performed by the same manner as described in example 1 except that the surface of resin powder was plated with nickel without forming transition metal protrusions thereon and displacement gold plating was carried out on the resultant nickel plating powder by the same manner as described in example 3.

As shown in Figure 10, protrusions were not observed in comparative example 1. The sizes and numbers of the protrusions on the H of the surface of the metal coated plating powder were measured and the electric resistance and adhesion were also investigated. The results are shown in Table 1. [Comparative Example 2]

An experiment was performed by the same manner as described in example 1 except that the Pd protrusion formation was induced on the resin powder activated by the pretreatment process and then the first and the second nickel plating processes followed.

As shown in Figures 11 and 12, the numbers of micro protrusions and protrusions were increased in comparative example 2. The area where protrusions were not formed was plated irregularly, suggesting that it was porous and many of the particles were not plated. [Comparative Example 3]

An experiment was performed using the micro protrusion type nickel plating powder prepared in comparative example 2 by the same manner as described in example 3.

As shown in Figures 13 and 14, the number of protrusions on the surface was reduced significantly after displacement gold plating and the adhesion between plating layers was decreased. Physical properties shown in Table 1 were measured as follows .

1) Regularity of plating

The surface of the plating powder was photographed by SEM (x 6000) to observe regularity of the plating powder and the protrusions.

2) Connection resistance The conductive particles were mixed in epoxy binder at the density of 250,000 particles/mπf, which was placed between flexible print circuit boards having 200 x 100 βm bonding wire pattern. Bonding was performed at 190 ^°C with compressing pressure of 60 N for 20 seconds. Then, electric resistance was measured.

3) Sizes and numbers of protrusions

The surface of the plating powder was photographed by SEM (x 20,000) to observe the sizes and numbers of protrusions formed on the H of the surface area of the metal particle.

4) Adhesion

1.0 g of the plating powder obtained above and 10 g of zirconia beads of 5 min in diameter were added into an 100 ml glass bottle, to which 10 ml of toluene was added, followed by stirring for 10 minutes at 400 rpm. Upon completion of stirring, zirconia beads were separated and the plating layer was observed under optical microscope.

The conditions of the layer were evaluated as follows. o : Peel-off of the plating membrane layer was not observed.

Δ : Partial peel-off of the plating membrane layer film was observed. x : Peel-off of the plating membrane layer was observed.

[Table 1]

As shown in Table 1 and Figures 2 - 14, the method of the present invention provides conductive powder which has excellent electric resistance because bigger and regular protrusions are formed and the area where protrusions are not formed is plated smoothly and evenly and has elaborate plating layer, excellent regularity and adhesion between the plating layer and the resin powder, compared with the conventional art.

[industrial Applicability]

As explained hereinbefore, the protrusion type conductive plating powder prepared by the method of the present invention contains protrusions which are bigger and regular, has excellent resin exclusivity during thermo-compression to electrode by anisotropic conductive film because the surface area where protrusions are not formed is also plated evenly and smoothly, has excellent connection reliability with electrode and has excellent regularity and adhesion between the elaborated plating layer and the resin powder. Therefore, the present invention provides high guality conductive electroless plating powder that can satisfy the need of micro wiring without limitation by capacitance during connection.

Claims

[CLAIMS]

[Claim l]

A manufacturing method of protrusion type plating powder, wherein the first electroless metal plating layer is formed on the surface of a core material using resin powder via electroless plating method; and generating transition metal protrusions on the resin powder by adding a transition metal and a reducing agent.

[Claim 2]

The manufacturing method of protrusion type plating powder according to claim 1, wherein the transition metal protrusions are formed by a different metal from the one used for the first electroless metal plating layer.

[Claim 3]

The manufacturing method of protrusion type plating powder according to claim 1 or claim 2, wherein the additional step of forming the second electroless metal plating layer on top of the transition metal protrusions and on top of the first electroless metal plating layer where protrusions are not formed is included.

[Claim 4] The manufacturing method of protrusion type plating powder according to claim 3, wherein the additional step of forming a gold plating layer on top of the second electroless metal plating layer is included.

[Claim 5] The manufacturing method of protrusion type plating powder according to claim 4, wherein the step of forming the gold plating layer is characterized by the following processes of displacement gold plating on the conductive powder coated with the second electroless metal plating layer by dispersing the powder in displacement gold plating solution; and forming a reduced gold plating layer on the displacement gold plating layer by adding a reducing agent after changing the displacement gold plating solution as alkali condition.

[Claim β]

The manufacturing method of protrusion type plating powder according to claim 5, wherein the alkali condition indicates pH 10-14.

[Claim 7]

The manufacturing method of protrusion type plating powder according to claim 4, wherein the core material is 0.5

~ 1000 μm in mean diameter, has the aspect ratio of up to 2, and has Cv value of up to 30% which is calculated by the following mathematical formula 1. [Mathematical Formula 1] Cv ( % ) = ( σ/Dn ) ^χ 100

[Claim 8]

The manufacturing method of protrusion type plating powder according to claim 7, wherein the core material is a compound or a mixture of at least two compounds selected from the group consisting of polyethylene, polyvinylchloride, polypropylene, polystyrene, polyisobutylene, styrene- acrylonitrile copolymer and acrylonitrile-butadiene-styrene terpolymer, polyacrylate, polymethylmethacrylate, polyacrylamide, polyvinylacetate, polyvinylalcohol, polyacetal, polyethyleneglycol, polypropyleneglycol, epoxy resin, benzoguanamine, urea, thiourea, melamine, acetoguanamine, dicyan amide, aniline, formaldehyde, palladiumformaldehyde, acetaldehyde, polyurethane and polyester.

[Claim 9] The manufacturing method of protrusion type plating powder according to claim 8, wherein one or more metals selected from the group consisting of Au, Ag, Co, Cu, Ni, Pd, Pt and Sn or an alloy thereof are used for the first electroless metal plating layer and the second electroless metal plating layer. [Claim 10 ]

The manufacturing method of protrusion type plating powder according to claim 9, wherein the first electroless metal plating layer and the second electroless metal plating layer are plated with multiple layers of at least two comprising two or more metals.

[Claim 11]

The manufacturing method of protrusion type plating powder according to claim 10, wherein the transition metal used for the generation of protrusions is one or more metals selected from the group consisting of Pd, Cu, Ru, Pt, Ag and

Co or an alloy thereof.

[Claim 12]

The manufacturing method of protrusion type plating powder according to claim 11, wherein the protrusions are 0.3

~ 1.0 p in mean diameter and round shaped, and at least 5 of them are formed on the ^ surface area of 1 particle of the plating powder.

[Claim 13]

The manufacturing method of protrusion type plating powder according to claim 1 or claim 5, wherein the reducing agent is one or more compounds selected from the group consisting of erythorbic acid compounds, hydrazine compounds, hydroquinone compounds, boron compounds and phosphoric acid compounds or their salts.