TW201315314A - Electroless nickel plating solution and method of manufacturing printed circuit board using the same - Google Patents

Abstract

There are provided an electroless nickel plating solution capable of preventing non-plating of nickel, and a method of manufacturing a printed circuit board using the same. The electroless nickel plating solution including 0.05 to 3.0 grams of surfactant per 1 liter thereof. Nickel plating is performed by using the electroless nickel plating solution, and thus, the generation of unplated regions can be prevented.

Description

Electroless nickel plating solution and method for manufacturing printed circuit board using the same Related application

The present application claims priority to Korean Patent Application No. 10-2011-0100, 126, filed on Sep. 30, 2011, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an electroless nickel plating solution and a method of manufacturing a printed circuit board using the same, and more particularly to an electroless nickel plating capable of suppressing generation of an unplated area and reducing variation in plating thickness. A coating solution and a method of manufacturing a printed circuit board using the same.

The plating method can be classified into an electroplating and an electroless plating method. As far as the manufacturing process is concerned, these plating methods are simple, stable in process, low in cost, short in processing time, low in deposition temperature, and high-purity film having low resistance, and thus can be widely used in a very large-sized integrated circuit.

According to the principle of the electroless plating method, the metal is precipitated by the spontaneous oxidation and reduction reaction of the material in the solution, and even without the need for external power, the electroless plating method has been widely used for manufacturing printed circuit boards.

Since the electroless plating method is carried out in an aqueous solution, the subsequent plating process is excellent in continuity, and the aqueous solution is easily infiltrated into a pattern formed on the plated object. As a result, a metal layer having excellent uniform characteristics and no problem associated with step coverage can be formed.

In recent years, due to the increasing demand for tightness and high performance of electronic products, printed circuit boards must be highly integrated, so the solder resist opening (SRO) on the printed circuit board needs to be miniaturized.

Since the size of the solder mask opening (SRO) must be reduced to 80 micrometers (μm) or less, no plating can occur in electroless nickel immersion gold (ENIG) or electroless nickel electroless palladium immersion gold (ENEPIG) ) in the plating process.

To solve this problem, plasma treatment can be performed before plating, but this will result in an increase in processing cost. In addition, non-plating problems such as nickel Ni-skip defects occur continuously depending on the processing conditions.

The aspect of the present invention provides an electroless nickel plating solution capable of suppressing generation of an unplated region while reducing plating thickness deviation during electroless nickel plating, and a method of manufacturing a printed circuit board using the solution.

According to an aspect of the present invention, there is provided an electroless nickel plating solution comprising 0.05 to 3.0 g of a surfactant per 1 liter of the solution.

The surfactant may be at least one selected from the group consisting of anionic surfactants, including sodium lauryl sulfate, ammonium lauryl sulfate, sodium lauryl ether sulfate, alkyl isethionate. Sodium, sodium lauryl tetraethoxyphosphate, and lauryl sarcosinate; and nonionic surfactants, including polyoxyethylene alkyl ethers and polyethylene glycols.

The electroless nickel plating solution may further comprise 20 to 36 grams of nickel sulfate, 5 to 10 grams of sodium citrate, 40 to 50 grams of ammonium sulfate, 10 to 20 grams of sodium hypophosphite, and 0.5 to 1 per 1 liter of the solution. Thiourea.

According to another aspect of the present invention, a method of manufacturing a printed circuit board is provided, the method comprising: preparing a printed circuit board having a solder resist layer containing a solder resist opening (SRO); and the printed circuit The plate is electroless nickel plated using an electroless nickel plating solution comprising 0.05 to 3.0 grams of surfactant per 1 liter of the solution.

The electroless nickel plating solution may further comprise 20 to 36 grams of nickel sulfate, 5 to 10 grams of sodium citrate, 40 to 50 grams of ammonium sulfate, 10 to 20 grams of sodium hypophosphite, and 0.5 to 1 per 1 liter of the solution. Thiourea.

The method may include gold plating after electroless nickel plating.

The solder resist opening (SRO) may have a diameter of 80 μm or less.

Specific embodiments of the invention are described in detail below and are illustrated in the drawings.

However, the invention may be embodied in different forms and should not be limited to the specific embodiments described herein.

Rather, these specific embodiments are provided so that this disclosure will be thorough and complete.

In the drawings, the shapes and dimensions of the various elements may be exaggerated for clarity of the description, and the same reference numerals are used to denote the same or similar elements.

According to a specific embodiment of the present invention, an electroless nickel plating solution containing a surfactant added may be used.

In general, the electroless plating solution may have substantially a metal salt containing a metal ion to be used for plating, and a reducing agent capable of reducing and precipitating the metal ion.

The wrong agent can stably dissolve the metal ion, and the pH adjuster can provide the hydrogen ion required for the oxidation reaction of the reducing agent, the catalyst can catalyze the redox reaction, the accelerator can increase the rate of the redox reaction, and the stabilizer can be To prevent abnormal precipitation of metals, these can be added to the solution.

The electroless nickel plating solution in the specific embodiment of the present invention may further comprise 20 to 36 grams of nickel sulfate, 5 to 10 grams of sodium citrate, 40 to 50 grams of ammonium sulfate, and 10 to 20 grams per 1 liter of the solution. Sodium phosphate, and 0.5 to 1 gram of thiourea.

Nickel sulfate is a metal salt containing nickel which can be used as a source of nickel ions to provide nickel ions to an electroless nickel plating solution.

Sodium hypophosphite can be used as a reducing agent to reduce nickel ions to nickel metal to form a nickel plating layer on the surface of the substrate.

The pH of the electroless nickel plating solution can be adjusted by sodium citrate and ammonium sulfate. The redox reaction of electroless plating is greatly affected by the pH of the electroless nickel plating solution.

Thiourea increases the rate of the redox reaction, thereby reducing the size of the precipitated nickel particles and increasing the gloss of the nickel plating layer.

In a specific embodiment of the invention, 0.05 to 3.0 grams of surfactant may be included per 1 liter of the electroless nickel plating solution.

When the content of the surfactant is less than 0.05 g, the wettability between the interface of the electroless nickel plating solution and the object to be plated is only slightly improved. When the content of the surfactant is more than 3.0 g, the plateability is destroyed because carbon forms an euectoid or bubbles on the plated film.

The surfactant is a material which is dissolved in a liquid and adsorbed to the interface, and can significantly reduce the energy of the interface, thereby performing functions such as wetting, emulsifying, dispersing, foaming, dissolving, washing, and the like.

Currently classified as an ionic surfactant, it is soluble in water to exhibit interfacial activity, and a nonionic surfactant that is insoluble in water and is in an ionic neutral state. The ionic surfactants include anionic, cationic and zwitterionic surfactants.

As the anionic surfactant, a carboxylic acid (-COOH), a sulfonate (-SO ₃ H), a sulfonate (-OSO ₃ H), a phosphate, a phosphate, an alkylbenzenesulfonate can be used. , α-olefin sulfonate, alkyl sulfonate, alkyl ether sulfate, alkyl sulfonate, and the like. As the cationic surfactant, an amine salt, a quaternary ammonium salt, a phosphonium salt, a phosphonium salt or the like can be used. As the zwitterionic surfactant, an amino acid type cationic surfactant or a betaine type surfactant can be used.

As the nonionic surfactant, polyol derivatives such as monoglycerides, polyglycerides; sorbitan esters; sucrose fatty acid esters; alkanolamines; polyethylene glycol and sorbitol; saccharin; -OH group, -COO- group, -CO‧NH- group, -O- group polyhydroxy compound, and the like.

In a specific embodiment of the present invention, the surfactant is added to the electroless nickel plating solution, thereby reducing the surface tension of the electroless nickel plating solution to improve the filling quality of the electroless nickel plating solution ( Filling qualities).

In other words, the electroless nickel plating solution cannot smoothly contact narrow portions such as curved regions, through holes, through holes, and the like. However, when a surfactant is added to the electroless nickel plating solution, the electroless nickel plating solution can be smoothly wetted on these portions, thereby increasing the plating reaction force and suppressing the defoaming due to hydrogen bubbles. An unplated area appears.

In a specific embodiment of the present invention, an example of a surfactant may be at least one selected from the group consisting of an anionic surfactant, including sodium lauryl sulfate, ammonium lauryl sulfate, and lauryl ether sulfate. Sodium, lauryl sarcosinate, sodium alkyl isethionate, sodium lauryl tetraethoxyphosphate, and lauryl sarcosinate; and nonionic surfactants, including polyoxyethylene Alkyl ether and polyethylene glycol.

A method of manufacturing a printed circuit board according to another embodiment of the present invention will be described below.

Referring to FIGS. 1 and 2, the method of manufacturing a printed circuit board of the present invention may include: preparing a printed circuit board having a solder resist layer 30 containing a solder resist opening (SRO) 31; and using the printed circuit board The electroless nickel plating solution is subjected to electroless nickel plating, and the solution includes 0.05 to 3.0 g of the surfactant per 1 liter of the solution.

The insulating layer 10 can structurally support the printed circuit board and the insulated conductor (which is formed in the printed circuit board).

The inner line 22, the via conductor 21, and the conductive pad 20 may be formed inside the printed circuit board.

The inner line 22 may be located inside the insulating layer between the line patterns and may form a plurality of layers. When the internal wiring 22 forms a plurality of layers, the internal wiring 22 formed in the different layers may be connected to the via conductor 21.

Conductive pads 20 can be located on the outer surface of insulating layer 10 and can be used to form electrodes on a printed circuit board.

The solder resist opening (SRO) 31 penetrating the solder resist layer 30 may be formed by partially removing the solder resist layer by etching or the like for exposing the conductive pad 20 formed on the surface of the printed circuit board to the outside. This is called a solder mask opening or a solder resist opening (SRO) 31.

First, the printed circuit board can be cleaned to remove organic contaminants such as oils.

Thereafter, soft etching is performed to form fine roughness on the surface of the resulting printed circuit board, and therefore, the adhesion of the nickel plating layer to be formed later can be increased.

Thereafter, a pre-dip process is performed to activate the surface of the resulting printed circuit board.

Thereafter, a substituted palladium catalyst of the Cl type or the SO ₄ type can be formed. Through this catalysis, a seed for generating a spontaneous redox reaction to produce plating and starting a reduction reaction in an electroless nickel plating solution can be produced in a non-conductive device.

Thereafter, electroless nickel plating is performed.

Here, 0.05 to 3.0 g of the surfactant may be contained per 1 liter in the electroless nickel plating solution.

Further, the electroless nickel plating solution may further comprise 20 to 36 grams of nickel sulfate, 5 to 10 grams of sodium citrate, 40 to 50 grams of ammonium sulfate, 10 to 20 grams of sodium hypophosphite, and 0.5 per 1 liter of the solution. To 1 gram of thiourea.

Thereafter, palladium (Pd) plating and electroless gold plating (Au) plating may be performed to form a thin gold plating layer.

Thereafter, electroless gold (Au) plating may be performed to form a thick gold (Au) plating layer.

The above method can be used to fabricate printed circuit boards having nickel and gold plating thereon.

The solder resist opening (SRO) of the printed circuit board may have a diameter (A) of 80 μm or less.

In the case where the solder resist opening (SRO) of the printed circuit board has a diameter (A) of 85 to 120 μm, it is necessary to perform plasma pretreatment before electroless nickel plating, however, continuity is generated to produce an unplated area.

In addition, the plasma treatment increases manufacturing costs.

When the solder resist opening (SRO) has a diameter of 80 μm or less, the solder resist opening (SRO) is narrow, so that the electroless nickel plating solution cannot easily penetrate into the solder resist opening (SRO). As a result, the contact between the electroless nickel plating solution and the object to be plated cannot be properly produced, and thus the plating layer cannot be formed.

In order to solve these problems, the electroless nickel plating solution of the specific embodiment of the present invention includes 0.05 to 3.0 g of the surfactant per 1 liter.

By adding a surfactant, the interfacial tension of the electroless nickel plating solution can be reduced, and the wettability of the electroless nickel plating solution on the surface of the object to be plated can be improved, and therefore, the electroless nickel plating solution can be It is easier to penetrate into small spaces.

Therefore, the electroless nickel plating solution can be in good contact with the surface of the object to be plated without generating an unplated region where the plating layer is not formed.

Therefore, the wettability of the electroless nickel plating solution is increased, and the contact between the electroless nickel plating solution and the object to be plated can be improved.

Therefore, the contact between the electroless nickel plating solution and the object to be plated or the plated layer can be more often occurred, and therefore, compared with the case where no surfactant is added to the electroless nickel plating solution, the plating is performed. The entire layer can be thicker. Furthermore, the plating layer can be formed more uniformly.

Other contents relating to the composition of the electroless nickel plating solution are as described above.

<Example>

Hereinafter, the invention will be described in detail by way of specific examples.

First, a printed circuit board including a solder resist opening (SRO) having a size of 80 μm was prepared, after which cleaning and soft etching were performed thereon, thereby removing foreign substances remaining on the surface thereof.

Thereafter, a pre-dip process is performed to activate the surface of the printed circuit board.

Thereafter, a nickel plating layer is formed on the surface of the printed circuit board by an electroless plating method.

The electroless nickel plating solution was prepared as follows. That is, an electroless nickel plating solution is prepared, wherein the content of the surfactant is varied in the alkaline plating solution, and the solution includes 25 g of nickel sulfate and 8 g of citric acid per 1 liter of the electroless nickel plating solution. Sodium, 45 grams of ammonium sulfate, 15 grams of sodium hypophosphite, and 1 gram of thiourea.

In Example 1 of the present invention, 0.05 g of sodium lauryl sulfate was added as a surfactant.

In Example 2 of the present invention, 0.05 g of sodium lauryl ether sulfate was added as a surfactant.

In Example 3 of the present invention, 0.05 g of ammonium lauryl sulfate was added as a surfactant.

In Example 4 of the present invention, 0.96 g of polyoxyalkylene alkyl ether was added as a surfactant.

The electroless plating is performed while the electroless nickel plating solution is maintained at 80 ° C, so that a nickel plating layer is formed on the SRO of the printed circuit board.

Thereafter, a palladium (Pd) plating layer is formed by electroless plating on the nickel plating layer, and then a gold (Au) plating layer is formed by electroless plating on the palladium plating layer.

The electroless nickel plating solution of the comparative example was prepared in the same manner as in the examples of the present invention except that no surfactant was added to the electroless nickel plating solution.

For the examples and comparative examples of the present invention, the plating rate, the presence or absence of contamination by the palladium solution, the presence or absence of unplated areas, and the wire bonding test and the ball tensile test were performed. The results are shown in Table 1.

The plating rate is expressed by the value of the processing time formed by electroless plating on a 30 mm × 30 mm copper foil (CCL) to be plated for 25 minutes.

The presence or absence of the non-plated area was confirmed by optical microscopy, and the results are shown in Fig. 4.

When a non-plated area is partially generated, it is determined as a defect (NG), and if no unplated area is generated, it is judged to be good (OK).

Conduct wire welding test and ball tensile test.

According to the wire soldering test, the wire is soldered to the plated area of the printed circuit board, and then the wire is resisted from the tensile force when the wire is drawn. According to the ball tensile test, the ball is welded to the plating layer, and then when the ball is pulled out, it is checked whether the plating layer is peeled off or broken.

For the ENEPIG process, electroless plating can be performed with the surfactant being contaminated with a palladium solution. Therefore, when using a surfactant contaminated with a palladium solution, an evaluation is required.

That is, nickel plating and gold plating are performed after the surfactant is contaminated with the palladium solution, and then subjected to a wire bonding test and a ball tensile test to evaluate the reliability.

Further, electroless nickel plating was performed on a copper foil sheet, and the thickness and shape of the plating layer were observed, and the thickness and uniformity of the nickel plating layer were compared. The cross-sectional images of the respective examples are shown in Fig. 5.

Referring to Figs. 3 and 4, it was confirmed that the unplated region (B) was produced in the comparative example, but it was not observed in the inventive examples 1 to 4.

It should be understood that the surfactant can effectively reduce the surface energy of the electroless nickel plating solution, so the electroless nickel plating solution can effectively penetrate into the narrow space of the object to be plated, and as a result, the electroless nickel plating solution can be Smoothly contact the surface of the object to be coated.

Referring to Table 1, the comparative example and the embodiment of the present invention show a plating rate of 0.18 micrometers (μm) per minute (min), all of which have the same plating rate.

As far as the plating rate is concerned, since the comparative example is not significantly different from the embodiment of the present invention, it is presumed that the comparative example is not significantly different from the embodiment of the present invention in terms of productivity.

Both the comparative example and the examples of the present invention showed good results in the wire bonding test and the ball tensile test.

It can be confirmed that there is no problem of reliability when using the electroless nickel plating solution of the present invention.

It should be understood that all the reliability test results are quite good even when using a surfactant contaminated with a palladium solution.

In this regard, the surfactant of the present invention can also be used in the ENEPIG process.

Referring to Fig. 5A showing the results of the comparative example, it was confirmed that the plating layer had a thickness of 2.81 μm, and the nickel plating layer was not uniformly formed.

Referring to Fig. 5B showing the results of Example 1 of the present invention, it was confirmed that the plating layer had a thickness of 4.21 μm, and the nickel plating layer was uniformly formed.

That is, it can be presumed that the addition of the surfactant to the electroless nickel plating solution improves the wettability between the electroless nickel plating solution and the object to be plated, and thus the embodiment of the present invention can be uniformly formed as compared with the comparative example. Thicker nickel plating.

As described above, when nickel plating is performed on the printed circuit board using the electroless nickel plating solution of the specific embodiment of the present invention, generation of an unplated region can be prevented, and variation in plating thickness can be reduced.

The terminology used in the description herein is for the purpose of illustration The singular forms are intended to include the plural unless the context clearly dictates otherwise.

Unless specifically stated otherwise, the terms "comprise" and variations such as "comprises or "comprising" shall be taken to mean the inclusion of the elements, and not to exclude other elements.

The present invention has been described in detail with reference to the preferred embodiments of the present invention, and the scope of the present invention as defined by the appended claims.

10. . . Insulation

20. . . Conductive pad

twenty one. . . Through hole conductor

twenty two. . . Internal line

30. . . Solder mask

31. . . Solder mask opening (SRO)

The above and other aspects, features and other advantages of the present invention will become more apparent from

1A is a schematic view of a printed circuit board used in a specific embodiment of the present invention;

Figure 1B is a schematic view of a printed circuit board formed by nickel plating;

1C is a schematic view of a printed circuit board formed by gold plating thereon;

2 is a flow chart of a method of manufacturing a printed circuit board according to a specific embodiment of the present invention;

Figure 3 is an optical microscope image of a printed circuit board in a comparative example;

4A to 4D are optical microscope images of printed circuit boards according to Embodiments 1 to 4 of the present invention;

Figure 5A is a cross-sectional image of a printed circuit board of a comparative example;

Fig. 5B is a cross-sectional image of a printed circuit board according to Embodiment 1 of the present invention.

The representative figure has no component symbols and the meaning of its representation.

Claims (7)

An electroless nickel plating solution comprising 0.05 to 3.0 grams (g) of surfactant per 1 liter of the solution. The electroless nickel plating solution according to claim 1, wherein the surfactant is selected from at least one of the group consisting of an anionic surfactant, including sodium lauryl sulfate and dodecane. Ammonium sulfate, sodium lauryl ether sulfate, sodium alkyl isethionate, sodium lauryl tetraethoxyphosphate, and lauryl sarcosinate; and nonionic surfactants including polyoxyethylene alkyl Ether and polyethylene glycol. The electroless nickel plating solution as described in claim 1 further comprises 20 to 36 grams of nickel sulfate, 5 to 10 grams of sodium citrate, 40 to 50 grams of ammonium sulfate, 10 to 20 per 1 liter of the solution. Sodium hypophosphite and 0.5 to 1 gram of thiourea. A method of manufacturing a printed circuit board, the method comprising: preparing a printed circuit board having a solder resist layer (SDR); and using an electroless plating on the printed circuit board The nickel plating solution is subjected to electroless nickel plating, and the solution includes 0.05 to 3.0 g of the surfactant per 1 liter of the solution. The method of claim 4, wherein the electroless nickel plating solution comprises 20 to 36 grams of nickel sulfate, 5 to 10 grams of sodium citrate, and 40 to 50 grams of ammonium sulfate per 1 liter of the solution. 10 to 20 grams of sodium hypophosphite and 0.5 to 1 gram of thiourea. The method of claim 4, further comprising performing gold plating after performing the electroless nickel plating. The method of claim 4, wherein the solder resist opening (SRO) has a diameter of 80 μm or less.