KR102526076B1 - Hole filling method of circuit board using different species metal - Google Patents

Abstract

The present invention comprises the steps of forming a through hole in a substrate; forming an electroless plating part in the through hole; forming a bridge electrolytic plating portion containing a first metal in the electroless plating portion; and forming a filling part containing a second metal on the substrate on which the bridge electroplating part is formed, wherein the melting point of the first metal is higher than the melting point of the second metal. will be.

Description

Hole filling method of circuit board using different species metal}

The present invention relates to a method of filling a through hole in a circuit board by filling a conductive material into the through hole to electrically connect circuits provided on different surfaces of the board.

BACKGROUND OF THE INVENTION [0002] In electronic devices such as mobile terminals and display devices, circuit boards in which predetermined circuits are integrated are widely used. The circuit board is a board on which a circuit pattern is formed on an insulating substrate using a printing technique, a plating technique, an etching technique, or the like. Such a circuit board is divided into a single-sided printed circuit board, a double-sided printed circuit board, a multi-layer printed circuit board, etc. according to the formation structure of the circuit pattern. The double-sided printed circuit board and the multilayer printed circuit board are through-holes (though-holes or via holes) formed using a CNC drill or laser drill to connect circuit patterns formed on different sides of the board ) is filled with a conductive material.

One method of filling the through hole with a conductive material may be a method of filling the through hole by applying a stack via structure. However, the method has a problem in that the upper and lower portions of the through-hole are not completely filled in the process of filling the through-hole and proceeding with the build-up process. In addition, there was a problem in that the process process was difficult because the build-up had to be performed by controlling the position between the through-holes.

Another method of filling the through hole with a conductive material is a method of forming an electroless plating layer on the inner surface of the through hole with an electroless plating solution and then performing electrolytic filling plating on the electroless plating layer with an electroless plating solution. . However, this method has a problem in that process efficiency is reduced and high cost is consumed as the electroless plating solution and the electrolytic plating solution must be prepared respectively, and the electroless plating and electrolytic plating must be performed respectively. In addition, there was a problem in that a considerable amount of time was consumed during electrolytic fill plating.

Republic of Korea Patent No. 10-1418034

An object of the present invention is to provide a through-hole filling method capable of increasing the efficiency of a through-hole filling process of a circuit board.

The present invention in order to solve the above problems, forming a through hole in the substrate; forming an electroless plating part in the through hole; forming a bridge electrolytic plating portion containing a first metal in the electroless plating portion; and forming a filling part containing a second metal on the substrate on which the bridge electroplating part is formed, wherein the melting point of the first metal is higher than the melting point of the second metal. do.

The forming of the filling part may include electrolytically plating the substrate on which the bridge electroplating part is formed in a plating solution containing the second metal; and putting the electroplated substrate into a vacuum chamber to reflow it.

The forming of the filling part may include applying the metal powder by spraying the metal powder containing the second metal onto the substrate on which the bridge electrolytic plating part is formed; and heat-treating the substrate coated with the metal powder.

The forming of the filling part may include applying a conductive paste containing the second metal to the substrate on which the bridge electroplating part is formed; and heat-treating the substrate coated with the conductive paste.

The second metal may be a low melting point metal having a melting point of 1000 °C or less.

The second metal may be at least one selected from the group consisting of tin, bismuth, aluminum, zinc, silver, and copper.

Since the present invention fills the through-holes of the circuit board through a simple process of performing electroless plating and electrolytic plating so that some areas inside the through-holes are bridged (connected), and then filled with a low melting point metal and/or alloy thereof. The efficiency of the filling process can be improved.

1 illustrates a through-hole filling process of a circuit board according to an embodiment of the present invention.
2 and 3 are optical microscope images for explaining Experimental Example 2 of the present invention.

The terms or words used in the description and claims of the present invention should not be construed as being limited to ordinary or dictionary meanings, and the inventors use the concept of terms appropriately to describe their invention in the best way. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical spirit of the present invention.

The present invention relates to a method for filling through-holes in a circuit board, which was derived to solve the problems of the prior art in which a long time was consumed in filling the through-holes as the through-holes of the circuit board were filled through electroless plating and electrolytic plating. It is characterized in that the time consumed for filling the through-hole is reduced by applying a different metal when filling the through-hole. Specifically, a method of filling a through hole in a circuit board according to the present invention includes forming a through hole in a board; forming an electroless plating part in the through hole; forming a bridge electrolytic plating portion containing a first metal in the electroless plating portion; and forming a filling part containing a second metal on the substrate on which the bridge electroplating part is formed, which will be described in detail with reference to FIG. 1 .

Forming the through hole H in the substrate (FIG. 1(a)) may be performed using a CNC drill or a laser drill. The substrate is not particularly limited as long as it is commonly known, and specifically may be a plastic substrate, a glass substrate, or a ceramic substrate.

Forming the electroless plating portion 10 in the through hole H (FIG. 1(b)) may be performed by electroless plating using an electroless plating solution. The electroless plating is performed to secure throwing power on the inner surface (front surface) of the through hole H and the surface of the substrate. The electroless plating solution is not particularly limited, but may include a copper ion source, a complexing agent, a reducing agent, a pH adjusting agent, and an additive.

The copper ion source may be copper sulfate. The complexing agent is for stabilizing the alkali plating solution and may be EDTA. The reducing agent may be formalin or sodium borohydride. The pH adjusting agent is for supplying OH required for the oxidation reaction, and may be sodium hydroxide, potassium hydroxide, and the like. The additive may be ethylenediaminetetraacetic acid, hydroxyethylethylenetriacetic acid, cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, tetrakis(2-hydroxypropyl)ethyldiamine, and the like.

The electroless plating may be performed at a plating rate of 10 μm/hr at a pH of 11-14 and a temperature of 20 to 60 °C.

Forming the bridge electrolytic plating part 20 containing the first metal in the electroless plating part 10 (FIG. 1(c)) may be performed by electrolytic plating using an electrolytic plating solution containing the first metal. there is. The electrolytic plating is to form a bridge connecting some areas inside the through hole H in which the electroless plating portion 10 is formed. The electrolytic plating solution is not particularly limited, but may include sulfuric acid, copper sulfate, chlorine, a brightener, a carrier and a leveler. As such an electroplating solution is used, the first metal contained in the bridge electroplating part 20 may be copper.

The brightener is (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, 3-[(amino-iminomethyl)-thiol]-1-propanesulfonic acid, 3-(benzothiazole- 2-Mercapto)-propylsulfonic acid, sodium bis-(sulfopropyl)-disulfide, N,N-dimethyl dithiocarbamile propylsulfonic acid, 3,3-thiobis(1-propanesulfonic acid), 2-hydroxy-3 -[tris(hydroxymethyl)methylamino]-1-propanesulfonic acid, sodium 2,3-dimercaptopropanesulfonic acid, 3-mercapto-1-propanesulfonic acid, 5,5'-dithiobis(2-nitrobenzoic acid) , DL-cysteine, 4-mercapto-benzene sulfonic acid, and 5-mercapto-1H-tetrazol-1-methane sulfonic acid may be at least one selected from the group consisting of.

The carrier is polyoxyalkylene glycol, carboxymethylcellulose, octanediol bisglycol ether, oleic acid polyglycol ester, polyethylene glycol, polyethylene glycol dimethyl ether, polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol, polypropylene glycol, Polyvinyl alcohol, stearyl alcohol polyglycol ether, stearic acid polyglycol ester, 3-methyl-1-butyn-3-ol, 3-methyl-penten-3-ol, L-ethynylcyclohexanol, phenylpropynol , 3-phenyl-1-butyn-3-ol, propargyl alcohol, methylbutinol-ethylene oxide, 2-methyl-4-chloro-3-butyn-2-ol, dimethylhexanediol, dimethylocta It may be at least one selected from the group consisting of indiol, phenylbutinol, and 1,4-butanediol diglycidyl ether.

The leveler may be a saturated heterocyclic compound containing at least one of nitrogen, oxygen, sulfur, and phosphorus. Specifically, aziridine, oxirane, thiran, diaziridine, oxaziridine, dioxirane, azetidine, oxetane, thietane, diazetidine, dioxetane, dithietane, pyrrolidine, thiolane, phosphorane , imidazolidine, pyrazolidine, oxazolidine, isoxazolidine, thiazolidine, isothiazolidine, dioxolane, dithiolane, piperidine, oxane, thian, phosphinan, piperazine, morpholine , Thiomorpholine, dioxane, dithiane, azepane, homopyrerazine, azocan, oxocane, thiocane, azonan, may be one or more selected from the group consisting of oxonane and thionane.

The composition ratio of the electrolytic plating solution may be 200 to 300 parts by weight of copper sulfate, 50 to 150 parts by weight of a carrier, 0.5 to 5 parts by weight of a brightener, and 1 to 10 parts by weight of a leveler based on 100 parts by weight of sulfuric acid, and chlorine is 30 to 10 parts by weight based on the total weight of the plating solution. It may be 120 ppm. In this case, the chlorine may refer to chlorine ions generated by adding diluted hydrochloric acid to the plating solution.

The step of forming the filling part 30 containing the second metal on the substrate on which the bridge electroplating part 20 is formed (FIG. 1(d)) is the through hole H excluding the bridge electroplating part 20 to fill the area. Formation of the filling part 30 may be performed by electroplating and heating and melting (reflow) using a plating solution containing the second metal; thermal spraying of a metal powder containing a second metal; or through application (printing) of a conductive paste (conductive ink) containing a second metal. As the filling part 30 is formed through this process, it is possible to greatly reduce the filling time of the through hole and prevent the formation of voids during the filling process.

In detail, the step of forming the filling part 30 includes electroplating by putting the substrate on which the bridge electroplating part 20 is formed into a plating solution containing the second metal; and putting the electroplated substrate into a vacuum chamber to reflow it. The plating solution containing the second metal is not particularly limited as long as it is an electrolytic plating solution containing the second metal. For example, the electrolytic plating solution may include an electrolyte solution, a second metal ion source, a brightener, a carrier, and a leveler. The electroplating may be performed at 20 to 30 °C for 1 to 3 hours under the application of a current density of 1 to 5 ASD. In the heating and melting step, the conditions (temperature and time) may be appropriately adjusted according to the melting point of the second metal.

In addition, the forming of the filling part 30 may include spraying a metal powder containing a second metal onto the substrate on which the bridge electroplating part 20 is formed to apply the metal powder; and heat-treating the substrate coated with the metal powder. The application of the metal powder may be performed through a commonly known spraying method, and the average particle diameter of the metal powder may be appropriately adjusted according to the diameter of the through hole (H). In addition, the heat treatment may be performed under an inert atmosphere, and the conditions (temperature and time) may be appropriately adjusted according to the melting point of the second metal.

In addition, the forming of the filling part 30 may include applying a conductive paste containing a second metal to the substrate on which the bridge electroplating part 20 is formed; and heat-treating the substrate coated with the conductive paste. The conductive paste may include commonly known components (eg, a binder resin, a solvent, a dispersing agent, an antifoaming agent, a surfactant, a thickening agent, a wetting agent, a coloring agent, etc.) in addition to the second metal. The heat treatment may be performed under conditions capable of allowing thermal diffusion of the second metal while volatilizing a solvent contained in the conductive paste.

Meanwhile, the second metal may not be particularly limited as long as the melting point is lower than that of the first metal. In this way, when the filling part 30 is formed of a second metal having a melting point lower than that of the first metal, the filling part 30 is relatively formed through the thermal diffusion principle while preventing the bridge electroplating part 20 from collapsing. It can be filled in a short time. Specifically, the second metal may be a low melting point metal having a melting point of 1000 °C or less (specifically 700 °C or less, more specifically 250 °C or less). More specifically, the second metal may be a single metal selected from the group consisting of tin, bismuth, aluminum, zinc, silver, and copper, or a mixed alloy thereof. For example, the second metal may be Sn (MP: 231.93 °C), Sn-58Bi (MP: 139 °C), Sn-Zn-Bi (MP: 198 °C), or Sn-Zn-Al.

According to the method of filling through-holes in a circuit board according to the present invention, through-holes formed in a substrate having a thickness of 200 μm or more (specifically, 800 to 1500 μm) can be filled with a conductive material in a relatively short time. Specifically, the present invention can reduce the time consumed in the conventional through-hole filling process by 10 to 50%.

Hereinafter, the present invention will be described in more detail by examples. However, the following examples are intended to illustrate the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, and the scope of the present invention is not limited only to these.

[ Example One]

An epoxy resin substrate having a thickness of 1000 μm was laser processed to form a through hole having a diameter of 200 μm. Next, electroless plating is performed with an electroless copper plating solution containing copper sulfate, EDTA (complexing agent), formalin (reducing agent), and other additives (ethylenediaminetetraacetic acid, caustic soda), and electroless plating is performed on the inside of the through-hole and the surface of the substrate. A plating part was formed. At this time, electroless plating was performed at a pH of 12 and a bath temperature of 65 °C. After degreasing and pickling, sulfuric acid, copper sulfate, (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester (brightener), polyoxyalkylene glycol (carrier), aziridine (leveler) And electroplating was performed with an electrolytic copper plating solution containing chlorine ions to form a bridge electrolytic plating part inside the through hole. At this time, electroplating was performed at 27 °C for 90 minutes under the application of 2-4 ASD current densities. Next, electroplating was performed with a tin plating solution (YMT, Inc., Tinomat NFJ), and then it was put into a vacuum chamber and heated and melted at 230 ° C. to form a filling part. At this time, the electrolytic plating of the tin plating solution was performed at 23° C. for 2 hours under the application of 2 ASD current density.

[ comparative example One]

The through-holes were filled in the same manner as in Example 1, except that the filling portion was formed by electrolytic plating with the electrolytic copper plating solution used in forming the bridge electrolytic plating portion, rather than tin plating and heat-melting.

[ Experimental example One]

The time consumed for filling the through-holes in Example 1 and Comparative Example 1 was measured, respectively, and the results are shown in Table 1 below.

division electroless plating part
formation time Bridge Electrolytic Plating
formation time filling part
formation time total time Example 1 10 minutes 90 minutes 120 minutes 220 minutes Comparative Example 1 10 minutes 90 minutes 500 minutes 600 minutes

Referring to Table 1, in the case of Example 1 in which the through-holes were filled by the method according to the present invention, it was confirmed that the time required to fill the through-holes was reduced by about 1/3 compared to Comparative Example 1.

[ Experimental example 2]

After cutting the substrates filled with through-holes through Example 1 and Comparative Example 1, cross-sectional samples were prepared through mold molding using an epoxy resin. After polishing the prepared cross-section sample and processing the cross-section, the cross-section was confirmed with an optical microscope, and the results are shown in FIGS. 2 and 3.

Referring to FIGS. 2 and 3 , it was confirmed that the through-holes of Example 1, in which the through-holes were filled by the method according to the present invention, were filled in a state in which voids were minimized compared to Comparative Example 1.

H: through hole
10: electroless plating part
20: bridge electroplating part
30: filling part

Claims (6)

Forming a through hole in a substrate;
forming an electroless plating part in the through hole;
forming a bridge electrolytic plating portion containing a first metal in the electroless plating portion; and
Forming a filling part containing a second metal in the substrate on which the bridge electroplating part is formed,
The melting point of the first metal is higher than the melting point of the second metal,
The second metal is a metal different from the first metal or an alloy thereof. The method of claim 1,
Forming the filling part,
electrolytically plating the substrate on which the bridge electroplating part is formed in a plating solution containing the second metal; and
The through-hole filling method of a circuit board comprising the step of heating and melting (reflowing) the substrate on which the electrolytic plating is made by putting it into a vacuum chamber. The method of claim 1,
Forming the filling part,
applying the metal powder by spraying the metal powder containing the second metal onto the substrate on which the bridge electroplating part is formed; and
The through-hole filling method of a circuit board comprising the step of heat-treating the substrate coated with the metal powder. The method of claim 1,
Forming the filling part,
applying a conductive paste containing the second metal to the substrate on which the bridge electrolytic plating portion is formed; and
A method of filling through-holes in a circuit board comprising the step of heat-treating the substrate coated with the conductive paste. The method of claim 1,
Wherein the second metal is a low melting point metal having a melting point of 1000 ° C or less. The method of claim 1,
Wherein the second metal is at least one selected from the group consisting of tin, bismuth, aluminum, zinc, silver and copper.

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