KR102279855B1 - Through-hole filling method for circuit board and circuit board using the same - Google Patents

Abstract

The present invention relates to a method for filling a through hole of a circuit board with a conductive material, a method for filling a conductive material inside a through hole of a circuit board, the method comprising: forming a through hole in a substrate; Forming an electrolytic plating base layer with a predetermined thickness on the surface, performing bridge plating so that a bridge is created in a partial region inside the through hole by electroplating applying a pulse waveform to the electrolytic plating base layer; and performing through-hole filling plating on the through-hole on which the bridge plating has been made, wherein the bridge plating and the through-hole filling plating are performed using the same plating solution.

Description

A method for filling a through-hole of a circuit board and a circuit board manufactured using the same {Through-hole filling method for circuit board and circuit board using the same}

The present invention relates to a method for filling a through-hole of a circuit board and a circuit board manufactured thereby, and more particularly, to a method for filling a conductive material in a through-hole in order to electrically connect circuits formed on different surfaces of the substrate; Thereby, it relates to a circuit board manufactured.

A circuit board in which a predetermined circuit is integrated is widely used in electronic devices such as mobile terminals and display devices. A circuit board is a board in which a wiring pattern is formed on an insulating board by using a printing technique, a plating technique, an etching technique, or the like. Circuit boards are divided into single-sided printed circuit boards, double-sided printed circuit boards, multilayer printed circuit boards, and the like according to the formation structure of the wiring pattern. In a double-sided printed circuit board and a multi-layer printed circuit board, a through-hole or a via hole processed by a CNC drill or a laser drill is formed in order to connect the wiring patterns of different layers. Various methods have been used to form a conductive material on a resin of an inner wall of a through hole or a via hole.

Recently, due to the miniaturization of electronic devices, the diameter of a through hole or a via hole applied to a circuit board is also decreasing, and accordingly, an aspect ratio, which means a ratio of a diameter to a depth of the hole, is also increasing. In the process of filling the conductive material inside the through hole having a high aspect ratio, it is important that pores are not formed therein. When pores are formed inside the through-hole, a defect in which electrical connection is not made occurs or electrical resistance is partially increased, which causes the circuit not to operate normally or to generate a lot of heat.

One of the methods for filling the through-holes of the circuit board with the conductive material is to form a conductive layer on the inner surface of the through-holes by electroless plating, and then apply an electric current to the electroless plating layer to perform electroplating. Korean Patent Registration No. 1418034 is a prior document on a technique for filling a conductive material in a through hole of a circuit board. The preceding document describes the steps of A) preparing a multilayer printed circuit board in which a plurality of conductors and insulators are cross-stacked and having through-holes formed thereon, and B) an anionic oxide film by oxidizing the surface of the conductor exposed through the through-holes in the substrate. Forming a layer, C) coating the entire substrate including the through hole with conductive anion carbon, and D) using a micro-etching solution to coat the conductive surface of the entire substrate including the through hole with conductive anion carbon Disclosed is a technique related to a method for manufacturing a multilayer printed circuit board, comprising the steps of removing and E) electroplating the substrate to electrically connect the plurality of conductors. However, the technique disclosed in the prior art has a disadvantage in that the process cost is high because the pretreatment step before the electroplating step is complicated, and does not include a technical feature for suppressing the generation of pores in the through-hole in the electroplating step.

Therefore, there is a great need to develop a new technology capable of reducing the process cost by simplifying the configuration of the pre-filling step of the through-hole and suppressing the generation of pores inside the through-hole by controlling the process conditions during the electroplating process.

Therefore, the first problem to be solved by the present invention is to reduce the process cost in the plating process of filling the conductive material inside the through hole of the circuit board, and to realize complete filling so that pores are not formed inside the through hole. To provide a through-hole filling method of

A second problem to be solved by the present invention is to provide a circuit board manufactured by using the method for filling the through-holes of the circuit board.

In order to achieve the first object, the present invention is a method of filling a through-hole of a circuit board with a conductive material, the method comprising: forming a through-hole in a substrate; and electroless plating to a predetermined thickness on the inner surface of the through-hole Forming an electroless plating layer, performing bridge plating such that a bridge is generated in a partial region of the through hole by electroplating applying a pulse waveform to the electroless plating layer; and performing through-hole filling plating on the hole, wherein the bridge plating and the through-hole filling plating are performed using the same plating solution.

According to one embodiment of the present invention, a reverse pulse waveform may be applied to the bridge plating.

According to another embodiment of the present invention, the reverse pulse waveform may be applied to the upper and lower portions of the circuit board under different conditions.

According to another embodiment of the present invention, a reverse pulse waveform may be applied to the through-hole filling plating.

In order to achieve the second object of the present invention, there is provided a circuit board manufactured by the method for filling the through-holes of the circuit board.

The through-hole filling method of the circuit board of the present invention has the following effects.

1. Since bridge plating and through-hole filling plating are performed using one type of plating solution, the process can be simplified and the increase in process cost due to replacement of the plating solution can be suppressed.

2. During the bridge plating process, reverse pulse waveforms with different timings are applied to the upper and lower surfaces of the substrate so that a bridge can occur in the inner center of the through hole.

3. Through-hole filling By applying a predetermined reverse pulse waveform during the plating process, it is possible to suppress the formation of pores inside the through-hole during the through-hole filling process.

4. A plating film having a predetermined thickness can be formed in the through-hole and the surrounding area after filling the through-hole by applying a predetermined reverse pulse waveform in the overcoat plating.

1 is a sequential view of a through-hole filling process of a circuit board.
FIG. 2 illustrates a process in which the inside of the through-hole is filled with a conductive material by the through-hole filling process shown in FIG. 1 .
3 is a sequential view of the circuit board through-hole filling process of the present invention.
FIG. 4 illustrates a process in which the inside of the through-hole is filled with a conductive material by the through-hole filling process shown in FIG. 3 .
5A and 5B show current waveforms applied in the bridge plating step of the method for filling the circuit board through-holes of the present invention.
6 shows the current waveform applied in the through-hole filling plating step of the circuit board through-hole filling method of the present invention.
7 is a view showing the current waveform applied in the overcoat plating step of the circuit board through-hole filling method of the present invention.
8 is a cross-sectional photograph after the circuit board through-holes are filled with plating.

The present invention relates to a method for filling a through hole of a circuit board with a conductive material, a method for filling a conductive material inside a through hole of a circuit board, the method comprising: forming a through hole in a substrate; Forming an electrolytic plating base layer with a predetermined thickness on the surface, performing bridge plating so that a bridge is created in a partial region inside the through hole by electroplating applying a pulse waveform to the electrolytic plating base layer; and performing through-hole filling plating on the through-hole on which the bridge plating has been made, wherein the bridge plating and the through-hole filling plating are performed using the same plating solution.

A circuit board is an electronic device in which a predetermined circuit pattern is implemented on a board. Although the circuit pattern of the circuit board is composed of a single layer, it is also composed of multiple layers to improve the degree of integration, and in this case, a means for electrically connecting the circuit patterns formed on different layers is required. A method of connecting the circuit patterns of different layers is to form a through hole in a substrate by a method such as laser drilling, and to fill the inside of the through hole with a conductor. At this time, since the surface of the through-hole formed in the substrate is made of a non-conductor, a thin metal layer is formed on the surface using electroless plating, and an electric current is applied to the electroless plating layer to perform electroplating. In the process of filling the conductive material inside the through hole using the plating method, if the growth rate of the plating film on the top or bottom of the through hole is fast, it becomes difficult to fill the conductive material in the middle area of the through hole. Therefore, a special technique is required for the plating method of through hole filling. need.

FIG. 1 sequentially shows a through-hole filling process of a circuit board, and FIG. 2 shows a process in which the inside of the through-hole is filled with a conductive material by the through-hole filling process shown in FIG. 1 . 1 and 2 , first, a through hole 102 having a predetermined diameter is formed by drilling a substrate 101 . Then, electroless plating is performed to form the electroless plating layer 103 on the inner surface of the through hole 102 . At this time, the electroless plating layer 103 is formed not only on the inside of the through hole, but also on the upper and lower surfaces of the substrate. Next, bridge plating is performed using the first plating solution. In the bridge plating process, a current is applied to the electroless plating layer, and a plating film is grown in an intermediate depth region inside the through hole 102 to form the bridge plating portion 104a. Next, the through-hole filling part 104 is formed by filling the inside of the through-hole by electroplating using the second plating solution. In this case, the second plating solution is generally different from the first plating solution in composition and composition. As described above, the existing through-hole filling method is a two-component solution and is divided into a plating solution for the bridge forming step and a plating solution for filling, which causes inconvenience in solution management and process. However, the present invention uses a one-component solution unlike the case of using a two-component solution, and there is no need to manage the solution separately or divide the process, and has the advantage of being simplified.

The circuit board through-hole filling method of the present invention is characterized in that the electrolytic plating process after electroless plating consists of bridge plating and through-hole filling plating, and a plating solution having the same component and composition is used in the bridge plating and through-hole filling plating process. do. The plating solution includes copper sulfate, sulfuric acid, chlorine, a brightener, a carrier and a leveler. In the conventional plating technique for filling through-holes, the bridge plating solution does not include a leveler, but in the through-hole filling plating of the present invention, a leveler is included in both the bridge plating solution and the through-hole filling plating solution, and the composition ratio of the leveler is low. As described above, since the leveler is included in both the bridge plating solution and the through-hole filling plating solution, two-step plating can be performed in one plating bath, thereby reducing process costs. Preferred compositions of the bridge plating solution and the through-hole filling plating solution include 200 to 300 parts by weight of copper sulfate, 0.5 to 4 parts by weight of a brightener, 70 to 130 parts by weight of a carrier, and 2 to 8 parts by weight of a leveler based on 100 parts by weight of sulfuric acid, compared to the total plating solution 50 to 100 ppm chlorine. In addition, in the through-hole filling method of the present invention, reverse pulses of different timings are applied to the front and back surfaces of the substrate during the bridge plating process, and a predetermined reverse pulse waveform is applied during the through-hole filling plating process and the overcoat plating process.

FIG. 3 sequentially shows the circuit board through-hole filling process of the present invention, and FIG. 4 shows a process in which the inside of the through-hole is filled with a conductive material by the through-hole filling process shown in FIG. 3 .

3 and 4 , first, a through hole 202 is formed in the substrate 201 .

Next, an electroless plating layer is formed on the through-hole 202 and the surface of the substrate 201 . The electroless plating layer may be made of copper. As the electroless plating solution, a plating solution having a known component and composition may be used. The copper plating solution contains copper ions, a copper ion complexing agent, a copper ion reducing agent and a pH adjusting agent, and further contains an additive for the purpose of improving the mechanical properties of the plating film(s) or the stability of the plating solution. The main required technology of such electroless plating is to ensure uniformity of the entire surface of the inner wall of the through hole. In portions such as inside a through hole where convection of the used plating solution is not sufficiently conducted, the concentrations of copper ions (complexes), reducing agents and hydroxides, which are the main components of the plating reaction, decrease, and the uniform precipitation property is greatly reduced. In order to solve this problem, in the present invention, since one or more additives are used in addition to the copper salt, copper ion complex salt, copper ion reducing agent and pH adjuster of the electroless copper plating solution, uniform precipitation is improved, and the plating thickness of the inner wall of the through hole is improved. can be obtained consistently. Copper sulfate is used as a source of metal copper ions in the composition of the plating solution, and the complexing agent is used for stabilization in an alkali plating solution. Specifically, EDTA can be used, and the reducing agent has a redox potential lower than the copper redox potential and reacts Although this occurs, there is a condition that the reaction rate as a catalyst must be fast, without actually creating a decomposition reaction in the liquid, not forming an insoluble precipitate by combining with other compositions. As the reducing agent, formalin or sodium borohydride may be used. The pH adjuster is used for the purpose of supplying OH required for the oxidation reaction of formalin, and sodium hydroxide, potassium hydroxide, etc. may be used. The additive may include ethylenediaminetetraacetic acid, hydroxyethylethylenetriacetic acid, cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, tetrakis(2-hydroxypropyl)ethyldiamine, and the like. The plating operation conditions are generally a temperature of 20 to 60° C., a pH of 11 to 14, and it is preferable to work at a pH as high as possible in terms of plating speed. The general plating rate is 10 µm/Hr, and copper ions can easily precipitate under conditions where the plating rate is too fast, so solution stability tends to be poor.

Next, bridge plating is performed to bridge the copper plating film in the through hole 202 . In this case, the bridge plating may be performed by an electrolytic copper plating method, and a reverse pulse may be applied during the electrolytic copper plating process. The application of the reverse pulse is to keep the thickness of the plating film constant, and in particular, it reduces the dog bone effect that may occur at the corners of the upper and lower regions of the through hole, so that the bridge occurs first at the corner of the through hole. can be prevented The plating solution used for the bridge plating may include sulfuric acid, copper sulfate, chlorine, a brightener, a carrier, and a leveler. The composition ratio of the plating solution may be 200 to 300 parts by weight of copper sulfate relative to 100 parts by weight of sulfuric acid, 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, and chlorine is 30 to 120 ppm based on the total weight of the plating solution. desirable. In this case, the chlorine refers to chlorine ions generated by adding diluted hydrochloric acid to the plating solution.

In this case, the brightener is (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, 3-[(amino-iminomethyl)-thiol]-1-propane sulfonic acid, 3-(benzothiazole -2-Mercapto)-propyl sulfonic acid, sodium bis-(sulfopropyl)-disulfide, N, N-dimethyl dithiocarbamyl propyl sulfonic acid, 3,3-thiobis (1-propane sulfonic acid), 2-hydroxy- 3-[tris(hydroxymethyl)methylamino]-1-propane sulfonic acid, sodium 2,3-dimercaptopropane sulfonic acid, 3-mercapto-1-propane sulfonic acid, 5,5'-dithiobis(2-nitro benzoic acid), DL-cysteine, 4-mercapto-benzene sulfonic acid, and 5-mercapto-1H-tetrazole-1-methane sulfonic acid. An organic additive for electrolytic copper plating, comprising at least one of the group consisting of sulfonic acid can be used.

The carrier is polyoxyalkylene glycol, carboxymethylcellulose, octanediol bis glycol ether, oleic acid poly glycol ester, polyethylene glycol, polyethylene glycol dimethyl ether, polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol, polypropylene glycol, poly Vinyl alcohol, stearyl alcohol polyglycol ether, stearic acid poly glycol ester, 3-methyl-1-butyn-3-ol, 3-methyl-penten-3-ol, L-ethynylcyclohexanol, phenyl propynol, 3-Phenyl-1-butyn-3-ol, propargyl alcohol, methyl butynol-ethylene oxide, 2-methyl-4-chloro-3-butain-2-ol, dimethyl hexaindiol, dimethyloctane and at least one of the group consisting of diol, phenylbutinol and 1,4-butanediol diglycidyl ether.

Leveler is a saturated heterocyclic compound containing one or two elements of nitrogen, oxygen, sulfur, phosphorus, aziridine, oxirane, thiirane, diaziridine, oxaziridine, dioxirane, azetidine, oxetane, Thietane, diazetidine, dioxetane, dithiethane, pyrrolidine, thiolane, phosphorane, imidazolidine, pyrazolidine, oxazolidine, isoxazolidine, thiazolidine, isothiazolidine, diox Solan, dithiolane, piperidine, oxane, thiane, phosphinan, piperazine, morpholine, thiomorpholine, dioxane, dithiane, azepane, homopyrerazine, azocan, oxokan, thiocane, azonan , oxonane, and thionane may be an organic compound comprising at least one of the group consisting of.

5A and 5B show current waveforms applied in the bridge plating step of the method for filling the circuit board through-holes of the present invention. 5A is a waveform applied to the front surface of the substrate, and FIG. 5B is a waveform applied to the rear surface with a predetermined timing difference from the front surface. Referring to FIG. 5 , the reverse pulse waveform applied in the bridge plating process maintains the current I1 for a time t1, then the current I2 for a time t2, then the current I1 for a time t3, and then the current I2 for a time A waveform that holds for t4, then holds the current I1 for a time t5, and then holds the current I3 for a time t6, wherein the waveform is applied periodically for a predetermined time. At this time, I1 is preferably in the range of 1.5 to 2.5 ASD, I2 is preferably in the range of 0.5 to 1.5 ASD, more preferably I1 is in the range of 1.7 to 2.3 ASD, and I2 is in the range of 0.7 to 1.3 ASD It's good to be in range. Within the above range, I1 is preferably 1.5 to 2.5 times I2, more preferably 1.7 to 2.3 times. t1, t2, t3, t4 and t5 are preferably 5 to 20 ms, more preferably 7 to 13 ms, and t1, t2, t3, t4 and t5 may be the same time. I3 is preferably in the range of 3 to 5 ASD, more preferably 3.5 to 4.5 ASD. t6 is preferably 0.5 to 1.5 ms, more preferably 0.7 to 1.3 ms. The reverse pulse waveform has a period of 't1 + t2 + t3 + t4 + t5 + t6', specifically, the duty cycle = ton / (ton + toff) of the waveform is in the range of 0.6 to 1.2. can In the bridge plating process, the reverse pulse waveform may be continuously applied for 1 to 3 hours. The voltage can be selected in the range of 5-6V. In the bridge plating process, reverse pulse waveforms with different timings can be applied to the front and back sides of the circuit board. and the same waveform can be applied. The reason for applying current waveforms to the front and back surfaces of the substrate at different timings in the bridge plating process is to further improve the bridging and filling effects of the through-holes. The back side is reversed, and as the internal through-hole is peeled off, an advantageous filling effect can be obtained without voids. Conversely, if the front and rear current waveforms are the same, a large void may be formed in the inner center due to excessive growth of the inner through-hole during bridging and filling. In the existing technology, pulse reversal plating was performed to form a plating layer inside the through-hole. When the through-hole thickness was 0.4 t or less, the same pulse-reverse plating was performed on the front and back surfaces of the substrate, but the through-hole thickness was 0.4 t or more. As a result, internal voids were formed in the method through pulse reversal plating. The reason is that if current is supplied to the front and back surfaces in the same waveform, plating and dissolution of the plating layer occur simultaneously, and voids may occur inside. The main cause of the formation of voids inside the through-hole is that metal ions are rapidly consumed in the limited space inside the through-hole, and an overvoltage is formed during plating, which increases the generation of hydrogen. This will cause a void to form inside Therefore, if a certain copper metal ion can be sufficiently supplied into the thick through-hole, hydrogen generation due to overvoltage can be suppressed, and a normal plating layer growth process can be helped. There is also a method of externally stirring as such a constant copper ion supply method, but it is difficult to stir and supply a sufficient amount to the micropores. Therefore, if the front side is being plated with copper ions in the forward direction by changing the current on the front side and the back side, the back side is dissolved in the plating film in reverse to release copper ions. Copper ions emitted from the back side are consumed for plating on the front side, and sufficient metal ions are supplied to this, so that plating filling can be formed without voids inside the through hole.

A preferred composition of the bridge plating solution includes 200 to 300 parts by weight of copper sulfate, 0.5 to 5 parts by weight of a brightener, 50 to 150 parts by weight of a carrier, and 1 to 10 parts by weight of a leveler based on 100 parts by weight of sulfuric acid, and 30 to 120 ppm of chlorine compared to the total plating solution It may contain ions. The reason that the leveler is included in the plating solution used in the bridge plating process of the through-hole filling method of the present invention as described above is that the bridge delay effect caused by the leveler can be suppressed due to the application of the waveform having the special configuration. Specifically, during the filling of the through-hole, the leveler suppresses the growth of the entrance of the through-hole, and can preferentially help the growth in the interior where the current distribution is not sufficiently supplied. That is, a certain amount of leveler serves to help the plating growth on the inner wall of the through-hole, where the current distribution is not sufficient, so that void-free filling plating can be performed.

Then, the through-hole filling part 204 is formed by performing through-hole filling plating. Since the through-hole filling plating uses the same components and composition as the plating solution used in the bridge plating process, the bridge plating and the through-hole filling plating can be performed in a continuous process without replacing the plating bath. In through-hole filling plating, the same waveform is applied to the front and back surfaces of the substrate at the same timing. Fig. 6 shows a waveform used for through-hole filling plating. Referring to FIG. 6 , the waveform applied to the through-hole filling plating is a waveform in which the current I4 is maintained for a time t7 and then the current I5 is maintained for a time t8. I4 is preferably in the range of 1.5 to 2.5 ASD, more preferably 1.7 to 2.3 ASD. t7 is preferably in the range of 30 to 60 ms, more preferably 40 to 50 ms. I5 is preferably in the range of 3 to 4 ASD, more preferably 3.2 to 3.8. t8 is preferably in the range of 1 to 3 ms, more preferably 1.7 to 2.3 ms.

Then, the overcoat plating is performed to form the overcoat in the area above and below the through hole. The waveform used for the overcoat plating is shown in FIG. 7 . Referring to FIG. 7 , the waveform applied to the overcoat plating is a waveform in which the current I6 is maintained for a time t9 and then the current I9 is maintained for a time t10. I6 is preferably in the range of 1.6 to 2.8 ASD, and t9 is preferably in the range of 70 to 130 ms. I7 is preferably in the range of 1.5 to 2.5 ASD, and t10 is preferably in the range of 1 to 3 ms.

The present invention will be described in more detail below using examples.

Example 1

A through-hole having a diameter of 170 microns was processed with a laser in an epoxy resin substrate having a thickness of 200 microns.

Plating was performed as a method for filling the through-holes, and the plating steps were as follows. First, electroless plating was performed, and then electroplating was performed. At this time, the electroplating step is divided into a bridge plating step, a through-hole filling plating step for filling the inside of the through-holes of the upper and lower parts of the bridge with copper, and a covering film plating step to secure the plating thickness after finally filling the through-holes. was carried out. The plating solution used in the present invention was used as the same solution in bridge plating, through-hole filling plating, and overcoat plating.

Specifically, first, an electroless copper plating film was formed on the surface of the substrate and the inside of the through hole by using the electroless plating method. The electroless copper plating solution contains 30 parts by weight of copper sulfate, 85 parts by weight of EDTA as a complexing agent, and 22 parts by weight of formalin as a reducing agent. do. The acidity of the plating operation condition was pH 12, and the bath temperature was 65°C.

Subsequently, copper electroplating, which is a bridge plating process, was performed after the degreasing process and the pickling process. Conditions of the plating solution include 100 parts by weight of sulfuric acid, 200 parts by weight of copper sulfate, 0.5 parts by weight of a brightener, 70 parts by weight of a carrier, and 2 parts by weight of a leveler, and may include chlorine ions of 50 ppm relative to the total plating solution. The temperature of the plating solution was 27° C., and the plating time was 4.5 hours. In this case, the brightener may be (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, the carrier may be polyoxyalkylene glycol, and the leveler may be aziridine. At this time, the current waveform of the bridge plating was 2ASD for I1, 1ASD for I2, and 4ASD for I3 in FIG. 5A, t1, t2, t3, t4, and t5 were 10 ms, and t6 was 1 ms. The voltage was selected in the range of 5-6V. At this time, waveforms were applied to the front and rear surfaces of the circuit board at different timings, and there was a difference in timing as shown in FIG. 5B .

Then, through-hole filling plating was performed. The through-hole filling plating conditions were a forward current density of 2ASD (I4 in FIG. 6), a reverse current density of 3.5ASD (I5 in FIG. 6), and the forward application time was 50 ms (t7 in FIG. 6), the reverse current application time was 2 ms (t8 in FIG. 6). The voltage was selected in the range of 5-6V, and the plating time was 1. At this time, the same waveform was applied to the front side and the back side of the circuit board at the same timing, and the plating solution used had the same components and composition as the plating solution used for the bridge plating.

Then, the overcoat plating was performed. The overcoat plating conditions were a forward current density of 2.2 ASD (I6 in Fig. 7), a time of 100 ms (t9 in Fig. 7), a reverse current density of 2 ASD (I7 in Fig. 7), and a time of 2 ms (t10 in Fig. 7). . The voltage was selected in the range of 5-6V, and the plating time was 1 hour. At this time, the same waveform was applied to the front side and the back side of the circuit board at the same timing, and the plating solution used had the same components and composition as the plating solution used for the bridge plating.

Example 2

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t1, t2, t3, t4, and t5 were set to 8 ms.

Example 3

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t1, t2, t3, t4, and t5 were set to 12 ms.

Example 4

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t1, t2, t3, t4, and t5 were set to 6 ms.

Example 5

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t1, t2, t3, t4, and t5 were set to 18 ms.

Example 6

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t6 was set to 0.8 ms.

Example 7

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t6 was set to 1.2 ms.

Example 8

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t6 was set to 0.6 ms.

Example 9

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t6 was set to 1.4 ms.

Example 10

In the through-hole filling plating, the through-hole filling plating was performed in the same manner as in Example 1, except that t8 was set to 1.8 ms.

Example 11

In the through-hole filling plating, the through-hole filling plating was performed in the same manner as in Example 1, except that t8 was set to 2.2 ms.

Comparative Example 1

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t1, t2, t3, t4, and t5 were set to 3 ms.

Comparative Example 2

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t1, t2, t3, t4, and t5 were set to 23 ms.

Comparative Example 3

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t6 was set to 0.4 ms.

Comparative Example 4

In bridge plating, through-hole filling plating was performed in the same manner as in Example 1, except that t6 was set to 1.7 ms.

Comparative Example 5

In the through-hole filling plating, the through-hole filling plating was performed in the same manner as in Example 1, except that t8 was set to 0.8 ms.

Comparative Example 6

In the through-hole filling plating, the through-hole filling plating was performed in the same manner as in Example 1, except that t8 was set to 3.5 ms.

Comparative Example 7

Through-hole filling plating was performed in the same manner as in Example 1, except that the plating solution did not include a leveler.

Evaluation Example 1

The cross-section of the circuit board on which the through-hole filling plating was performed according to Examples 1 to 11 and Comparative Examples 1 to 7 was cut and the inside of the through-hole was observed with an optical microscope. In Examples 1, 2, 3, 4, 6, 7, 10, and 11, voids were not observed in the through-holes, and in Examples 4, 5, 8, and 9, voids with a diameter of ~10 microns were observed in the through-holes. In Comparative Examples 1 to 6, voids with a diameter of 20 microns or more were observed, and in Comparative Example 7, through-hole filling was not performed. The results are summarized in Table 1 below. From these results, it can be seen that the control of the waveform during the plating process is very important. From this, the adsorption and desorption of metal ions are induced according to the current waveform, and the leveler in the plating solution is adsorbed to the outside of the through-hole to control the plating. It can be seen that it plays a role that can preferentially do internal plating. In addition, it can be seen that the existence and type of the leveler also plays an important role in filling the through hole.

(A) of FIG. 8 is a photograph of a through-hole on which the through-hole filling plating was performed according to Example 1, and it can be seen that plating was made without forming a void inside the through-hole, (B) is a picture of the through-hole according to Comparative Example 7 It is a photograph of a through-hole on which the through-hole filling plating was performed, and it can be seen that the through-hole filling was incompletely performed.

Whether voids are formed void diameter void location Example 1 does not exist - - Example 2 does not exist - - Example 3 does not exist - - Example 4 has exist less than 10 microns center Example 5 has exist less than 10 microns center Example 6 does not exist - - Example 7 does not exist - - Example 8 has exist less than 10 microns center Example 8 has exist less than 10 microns center Example 10 does not exist - - Example 11 does not exist - - Comparative Example 1 has exist 20 microns or more Comparative Example 2 has exist 20 microns or more Comparative Example 3 has exist 20 microns or more Comparative Example 4 has exist 20 microns or more Comparative Example 5 has exist over 20 microns in length from the surface to the center Comparative Example 6 has exist over 20 microns in length from the surface to the center Comparative Example 7 unfilled unfilled unfilled

101: substrate 102: through hole
103: electroless plating layer 104a: bridge plating part
104: through-hole filling part
201: substrate 202: through hole
203: electroless plating layer 204: through-hole filling part

Claims (7)

In the method of filling a conductive material inside a through hole of a circuit board,
forming a through hole in the substrate;
forming an electroless plating layer to a predetermined thickness on the inner surface of the through hole by electroless plating;
performing bridge plating such that a bridge is generated in a partial region inside the through hole by electroplating by applying a pulse waveform to the electroless plating layer; and
Including; performing a through-hole filling plating on the through-hole on which the bridge plating is made by electrolytic plating;
The bridge plating and the through-hole filling plating are performed in the same plating bath using a plating solution having the same composition,
The plating solution includes sulfuric acid, copper sulfate, a carrier, a brightener and a leveler,
The leveler is a heterocyclic compound containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur and phosphorus,
A reverse pulse waveform having a period of t1+t2+t3+t4+t5+t6 is applied to the bridge plating,
In the period, t1, t2, t3, t4, and t5 are times for which a positive (+) current is applied, respectively, and t6 is a time for which a negative (-) current is applied,
The through-hole filling method of the circuit board, characterized in that the intensity of the current applied at each of t1, t3, and t5 is greater than the intensity of the current applied at each of the t2 and t4. delete The method according to claim 1,
The through-hole filling method of a circuit board, characterized in that the reverse pulse waveform is applied under different conditions to the upper and lower portions of the circuit board. The method according to claim 1,
A through-hole filling method of a circuit board, characterized in that a reverse pulse waveform is applied to the through-hole filling plating. delete delete A circuit board manufactured by the through-hole filling method of the circuit board of claim 1.

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