KR20110083586A - Electroless nickel solution composition - Google Patents

Abstract

PURPOSE: An electroless nickel-plating solution composition is provided to form a nickel plating layer having solderability, flexibility, and crack resistance by inputting vertical growth inducer. CONSTITUTION: An electroless nickel-plating solution composition comprises aqueous nickel compound, a reducing agent, a complex agent, and a vertical growth inducer. The vertical growth inducer comprises the compound having bismuth ion. The composition range of the vertical growth inducer based on the entire content of the electroless nickel plating solution composition is 0.001~1wt.%.

Description

Electroless nickel solution composition

The present invention relates to an electroless nickel plating liquid composition, by forming a nickel plating layer having a vertical growth structure using a vertical growth inducing agent, thereby simultaneously satisfying the plating characteristics required for the pad portion and the external connection portion of the flexible printed circuit board. The present invention relates to an electroless nickel plating solution composition.

The flexible printed circuit board includes a circuit pattern on the substrate, a pad portion for mounting an electronic component, and an external connection portion for electrically connecting with an external device. Here, the external connection unit may include a terminal unit and a connector. The terminal unit may be electrically connected to an external device such as a liquid crystal panel by ACF bonding. In addition, the connector may be electrically connected to the device by a detachable method.

 The circuit pattern, the pad part and the external connection part may generally be made of copper. The copper material may be easily oxidized when exposed to the outside. For this reason, when the electronic component is mounted on the oxidized pad portion, the reliability of the electronic product may be lowered, and the contact resistance between the pad portion and the electronic component may be increased to cause contact failure. As a surface treatment to prevent this, general electroless nickel-substituted plating is applied to the pad part, and additional direct gold plating is performed only on the external connection part.

Generally, the electroless nickel-substituted plating process is well known in the art. For example, Korean Patent Publication No. 2000-53621 discloses electroless nickel on a copper exposed portion to be gold plated using photosolder resist (PSR). After forming a phase, a method of manufacturing a printed circuit board using a plating solution including at least one water-soluble gold compound, at least one conductive salt, at least one reducing agent, and water is provided. In addition, Korean Patent Publication No. 2003-0080547 discloses a method of providing an alloy plating layer made of gold (Au) and silver (Ag) using a gold-silver alloy plating solution after electroless nickel plating. In addition, Japanese Patent Application Laid-open No. Hei 7-7243 forms an amorphous first electroless nickel film on a copper portion to be gold plated, and forms a crystalline second electroless nickel film, followed by an electroless having a substitution reaction as a main reaction. Gold plating method is presented. In addition, improved techniques for forming a nickel-gold plated layer on a copper layer are disclosed in US Pat. Nos. 5,235,139 and 6,733,823.

As described above, in the flexible printed circuit board, a general electroless nickel-substituted plating is performed on the pad part, and a direct gold plating process is performed on the external connection part as follows.

The pad part where general device, chip, etc. are mounted has good electroless nickel-substituted plating to improve weldability. However, when general electroless nickel plating is applied to the external connection part, it is cracked due to embrittlement of electroless nickel. Will occur. In particular, when the external connection portion is a terminal portion, while the liquid crystal panel is mounted by ACF bonding, the terminal portion may be bent at 360 °, causing a problem with cracking. In addition, even when the external connection part is a connector, bending may occur when the connector is inserted or after the connector is fastened, or a crack may occur due to the indentation of the fastening part. As a result, a plating process of nickel-free gold plating (direct gold plating) is performed to prevent cracking only at the external connection portion. In addition, the reason why direct gold plating is not applied to the pad part is that when gold plating is used, the formation of microvoids due to the occurrence of tombstone phenomenon and the diffusion of the surface of copper when mounting electronic components, and chip shear It is not possible to give reliable weldability due to the decrease in the value of. Here, the tombstone phenomenon refers to a soldering defect in which one end of the chip component is coupled without being soldered.

As described above, in the manufacture of a printed circuit board, a pad part on which a component is mounted is applied to the above-described general electroless nickel-substituted plating to give solderability, and a terminal part requiring flexibility in ACF bonding and a connector part which is detachable are additionally direct. By forming a gold plated layer can be given flexural resistance and crack resistance, it is possible to reduce the reliability and failure rate of electronic products.

However, since the two-plating process of electroless nickel plating and direct gold plating must be performed on the pad portion and the external connection portion, the manufacturing process of the flexible printed circuit board may be more complicated. Thereby, there was a problem that the economical and productivity is lowered thereby.

An object of the present invention is to form a nickel plating layer having a vertical growth structure using a vertical growth inducing agent, thereby providing an electroless nickel plating solution composition that can simultaneously satisfy the physical properties required for each of the pad portion and the external connection portion of the flexible printed circuit board. Is in.

One aspect of the present invention to achieve the above technical problem provides an electroless nickel plating composition. The electroless nickel plating composition includes a water soluble nickel compound, a reducing agent, a complexing agent and a vertical growth inducing agent.

Here, the vertical growth inducing agent may include a compound having bismuth ions.

In addition, the composition range of the vertical growth inducing agent may have a 0.001 to 1% by weight based on the total content of the electroless nickel plating solution composition.

In addition, the electroless nickel plating solution composition may further include a vertical growth aid. Here, the vertical growth assistant may include at least one or two or more selected from the group consisting of thallium ions, iron ions, and copper ions.

In addition, the water-soluble nickel compound may include at least one of nickel sulfate and nickel chloride.

In addition, the composition range of the water-soluble nickel compound may have 1 to 10% by weight based on the total composition of the electroless nickel plating solution.

In addition, the reducing agent may include at least one selected from the group consisting of hypophosphite, potassium hypophosphite, hydrazine and sodium hypophosphite.

In addition, the composition range of the reducing agent may have 1 to 10% by weight based on the total composition of the electroless nickel plating solution.

In addition, the complexing agent may include at least one or two or more selected from the group consisting of lactic acid, glycolic acid, and malic acid.

In addition, the composition range of the complexing agent may have 1 to 10% by weight based on the total composition of the electroless nickel plating solution.

In addition, the electroless nickel composition may further include at least one of a metal ion blocking agent, an organic acid and an alkali metal salt thereof, a monosaccharide, a surfactant, and a stabilizer.

Here, the metal ion sequestrant is at least one or two selected from the group consisting of derivatives of polycarboxylic acid, derivatives of amino acetic acid and derivatives of nitrilo-triacetic acid. It may contain the above.

In addition, the composition range of the metal ion blocking agent may have 0.01 to 1% by weight based on the total composition of the electroless nickel plating solution.

In addition, the organic acid and the alkali metal salt of the organic acid is acetic acid, sodium acetate, propionic acid, propionic acid, sodium propionate, formic acid, sodium formate, At least one or two or more selected from the group consisting of potassium formate, adipic acid, sodium adipate, succinic acid, sodium succinate, and the like. Can be.

In addition, the composition range of the organic acid and the alkali metal salt of the organic acid may have 0.1 to 10% by weight based on the total composition of the electroless nickel plating solution.

In addition, the monosaccharide includes at least one or two or more selected from the group consisting of glucose, fructose and galactose.

In addition, the composition range of the monosaccharide may have 0.1 to 10% by weight based on the total composition of the electroless nickel plating solution.

In addition, the surfactant may be a polyoxyethylene alkyl ether derivative.

In addition, the surfactant may be polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene octyl ether ), Polyoxyethylene tridecyl ether, at least one selected from the group consisting of polyoxyethylene laurylamine ether and polyoxyethylene stearylamine ether It may include.

In addition, the composition range of the surfactant may have from 0.01 to 10% by weight based on the total composition of the electroless nickel plating solution.

In addition, the stabilizer may be a thio compound.

In addition, the stabilizer is thiourea, alkyl thiourea, mercapto compound, thiazole compound, sodium thiosulfate, sodium thiocyanate, Potassium thiocyanate, thioglycolic acid, and thio diglycolic acid may include at least one or two or more selected from the group consisting of.

In addition, the composition range of the stabilizer may have a 0.0001 to 0.1% by weight based on the total composition of the electroless nickel plating solution.

In addition, the pH range of the electroless nickel plating solution composition may have 4 to 6.

The electroless nickel plating solution composition according to the present invention can form a nickel plating layer having all of weldability, bendability and crack resistance by providing a vertical growth inducing agent.

In addition, by using the electroless nickel plating solution composition according to the present invention, it is possible to satisfy all the plating characteristics required for each of the pad portion and the external connection portion of the flexible printed circuit board.

In addition, it is possible to replace the conventional electroless nickel and direct gold plating double plating process performed in the conventional flexible printed circuit board manufacturing with a single plating process, thereby contributing to the simplification of the process, productivity improvement and significant cost reduction. have.

1 is a plan view of a flexible printed circuit board according to a second exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view of the flexible printed circuit board of FIG. 1.
3 to 6 are cross-sectional views illustrating a method of manufacturing a flexible printed circuit board according to a third embodiment of the present invention.
7 is a photograph showing the fracture surface of the electroless nickel plating layer having the vertical growth structure according to the embodiment of the present invention.
8 is a photograph showing the fracture surface of the electroless nickel plating layer having the vertical growth structure according to the comparative example of the present invention.

Hereinafter, the electroless nickel plating solution composition according to the first embodiment of the present invention will be described in more detail, but the present invention is not limited thereto.

The electroless nickel plating solution composition according to the first embodiment of the present invention may include a water-soluble nickel compound, a reducing agent, a complexing agent, and a vertical growth inducing agent.

Here, the water-soluble nickel compound is the main material that is deposited and plated on the substrate. The water-soluble nickel compound may include at least one of nickel sulfate and nickel chloride. Specifically, examples of the material used as the water-soluble nickel compound may be nickel sulfate (NiSO _{4 ·} 6H ₂ O). The composition range of the water-soluble nickel compound may have 1.0 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably the composition range of the water-soluble nickel compound may have a 2.0 to 5.0% by weight based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the water-soluble nickel compound is less than 1.0% by weight, the plating rate is significantly lowered and productivity cannot be expected. On the other hand, when the composition of the water-soluble nickel compound is more than 10.0% by weight, the compounding ratio of the complexing agent, reducing agent, etc. to be described later must be raised together, so there is a problem that the drag-out loss increases. Here, the drag-out loss means the amount of the plating solution buried in the plated material when the plating bath is finished after the plating is finished.

The reducing agent serves to reduce nickel ions to nickel metal. The reducing agent may include at least one selected from the group consisting of hypophosphite, potassium hypophosphite, hydrazine, and sodium hypophosphite. Examples of the material used as the reducing agent may be sodium hypophosphite (NaH ₂ PO _{2 ·} 6H ₂ O). The composition range of the reducing agent may have 1.0 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably the composition range of the reducing agent may have a 1.5 to 3.0% by weight based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the reducing agent is less than 1.0% by weight, the reducing power may be lowered to reduce the plating rate. On the other hand, when the composition of the reducing agent exceeds 10.0% by weight, the consumption ratio of sodium hypophosphite according to nickel consumption may be exceeded and the drag-out loss may increase.

The complexing agent serves to supply stable nickel ions by complexing the nickel salt. The complexing agent may include at least one or two or more selected from the group consisting of lactic acid, glycolic acid, and malic acid. The composition range of the complexing agent may have 1.0 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably the composition range of the complexing agent may have a 2.0 to 5.0% by weight based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the complexing agent is less than 1.0% by weight, it is difficult to supply uniform nickel ions due to insufficient ignition power. On the other hand, when the composition of the complexing agent exceeds 10.0% by weight, the amount of nickel ions is exceeded, the drag-out loss is increased, and the plating speed may be significantly reduced.

Examples of the vertical growth inducing agent may be a compound containing bismuth (Bi) ions. Examples of the material used as the vertical growth inducing agent may be bismuth sulfate and bismuth nitrate. Practically, the bismuth ions serve to change the orientation of crystal growth of the nickel. That is, by the bismuth ions, the nickel may be grown to have a vertical structure with respect to the surface to be plated.

 The composition range of the vertical growth inducing agent may have a 0.0001 to 1.0% by weight based on the total weight of the electroless nickel plating solution composition. Preferably, the composition range of the vertical growth inducing agent may have a range of 0.001 to 0.1% by weight based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the vertical growth inducing agent is less than 0.0001% by weight, it does not contribute to the vertical growth during nickel plating. On the other hand, when the composition of the vertical growth inducing agent exceeds 1.0% by weight, unplating (skip) may occur during plating.

In addition, the electroless nickel plating solution composition may further include a vertical growth aid that may help the vertical growth of nickel. The vertical growth assistant may include at least one or two or more selected from the group consisting of thallium ions, iron ions, and copper ions.

Hereinafter, the plating principle of the electroless nickel plating solution composition will be briefly described through a reaction scheme.

Scheme 1

As in Scheme 1, the water-soluble nickel compound complexes with a complexing agent. On the other hand, dissociated hypophosphoric acid reduces nickel.

Scheme 2

As in Scheme 2, eutectic phosphorus (P) such as nickel may be precipitated. As such, the reactions shown in Scheme 1 and Scheme 2 may occur continuously.

Scheme 3

As in Scheme 3, it is possible to obtain an alloy structure in which nickel and phosphorus are vacant.

Here, the electroless nickel plating solution composition further includes a metal ion encapsulant to chelate palladium (Pd) ions or copper (Cu) ions mixed from the outside. That is, the metal ion blocking agent serves to suppress decomposition of the electroless nickel plating solution composition.

The metal ion blocking agent may be at least one selected from the group consisting of a derivative of polycarboxylic acid, a derivative of amino acetic acid, and a derivative of nitrilo-triacetic acid. It may include. Specifically, examples of the material used as the metal ion blocking agent include ethylene diamine tetra acetic acid, diethylene triamine penta-acetic acid, and N-hydroxyethyl ethylene diamine triacetic acid ( N-hydroxyethylethylene diamine triacetic acid), 1,3-diamino-2-propanol-N, N, N, N'-tetraacetic acid (1,3-diamino-2-propanol-N, N, N, N'- tetra acetic acid), bishydroxyphenyl-ethylene, diamine diacetic acid, and N, N-di (hydroxyethyl) glycine (N, N-di (hydroxyethyl) glycine) Can be. Here, the metal ion sequestrant may be included in the electroless nickel plating solution composition by mixing one or more than two.

The composition range of the metal ion blocking agent may have 0.1 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably, the composition range of the metal ion blocking agent may have a weight of 0.5 to 5.0 based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the metal ion blocking agent is less than 0.1% by weight, it is difficult to prevent decomposition of the electroless nickel plating solution composition. On the other hand, when the composition of the metal ion blocking agent exceeds 10.0% by weight, since the life of the predetermined electroless nickel plating solution is limited, the amount thereof may be excessively large and drag-out loss may increase.

In addition, the electroless nickel plating solution composition may further include at least one of an organic acid and an alkali metal salt of the organic acid. The organic acid and the alkali metal salt of the organic acid serve to prevent a decrease in the plating rate by the phosphorous acid (HPO ₃ ^2- ) generated in Scheme 2 and a decrease in pH of the electroless nickel plating solution composition. That is, the organic acid and the metal salt of the organic acid may serve as a plating rate promoter and a pH buffer.

The organic acid and its alkali metal salt may be a compound having at least one carboxyl group. Examples of the material used as the organic acid and its alkali metal salts include acetic acid, sodium acetate, propionic acid, sodium propionate, formic acid, and sodium formate. , Potassium formate, adipic acid, sodium adipate, succinic acid, sodium succinate, and the like. Here, the organic acid and its alkali metal salt may be mixed in one or more than two and included in the electroless nickel plating solution composition.

The composition range of the organic acid and the alkali metal salt thereof may have 0.1 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably, the composition range of the organic acid and its alkali metal salt may have 0.5 to 5.0 wt% based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the organic acid and its alkali metal salt is less than 0.1% by weight, the plating rate increase and buffering effect may be weak. On the other hand, when the composition of the organic acid and the alkali metal salt thereof exceeds 10% by weight, the embrittlement of the plating layer may be increased to significantly reduce the flex resistance.

In addition, the electroless nickel plating solution composition may further include a monosaccharide. Here, the monosaccharide serves to adjust the content of phosphorus (P) precipitated in the reaction scheme 2. Thereby, due to the increase or decrease of the phosphorus (P), it is prevented that the mechanical properties of the plating layer is changed rapidly. The monosaccharide may be at least one (CH ₂ O) _n H, n = 3-6. Here, examples of the material used as the monosaccharide may be glucose, fructose, galactose, or the like. Here, the monosaccharides may be mixed in one or more than two and included in the electroless nickel plating solution composition.

The composition range of the monosaccharide may have 0.1 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably, the composition range of the monosaccharide may have 0.5 to 5.0% by weight based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the monosaccharide is less than 0.1% by weight, an increase in phosphorus (P) is rapidly increased to reduce the flex resistance. On the other hand, when the composition of the monosaccharide exceeds 10.0% by weight, the plating rate can be significantly reduced.

In addition, the electroless nickel plating solution composition may further include a surfactant. The surfactant plays a role of maintaining thickness uniformity and uniformity of crystal grains according to the area to be plated. In addition, the surfactant serves to facilitate the separation of the hydrogen (H ₂ ) gas generated in Scheme 3 to improve the flex resistance. That is, the surfactant may serve as an enhancer of ductility of the plating layer.

The surfactant may be a polyoxyethylene alkyl ether derivative. Examples of the material used as the surfactant include polyoxyethylene lauryl ether derived from RO- (CH ₂ CH ₂ O) _n H, polyoxyethylene oleyl ether, polyoxyethylene Cetyl ether, polyoxyethylene octyl ether, polyoxyethylene tridecyl ether, and the like. Alternatively, examples of the material used as the surfactant include polyoxyethylene laurylamine ether derived from RN-[(CH ₂ CH ₂ O) _n H] ₂ , polyoxyethylene stearyl amine ether (polyoxyethylene stearylamine ether). Here, the surfactant may be mixed in one or more than two and included in the electroless nickel plating solution composition.

The composition range of the surfactant may have 0.01 to 10.0 wt% based on the total weight of the electroless nickel plating solution composition. Preferably, the composition range of the surfactant may have 0.1 to 1.0 wt% based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the surfactant is less than 0.01% by weight, it is difficult to expect the ductility effect of the plating layer. On the other hand, if the composition of the surfactant exceeds 10.0% by weight, the plating rate is significantly reduced, it is difficult to obtain a uniform plating layer.

In addition, the electroless nickel plating solution composition may further include a stabilizer. Here, the stabilizer serves to prevent decomposition of the plating liquid. In addition, the stabilizer may serve as a grain refiner to reduce the nickel particles precipitated. Here, when the crystal grains are miniaturized, solderability and flex resistance may be improved. The stabilizer may be a thio compound having at least one -S-. Examples of the material used as the stabilizer include thiourea, alkyl thiourea, mercapto compound, thiazole compound, sodium thiosulfate, sodium thiocyanate thiocyanate), potassium thiocyanate, thioglycolic acid, thio glycolic acid, and thio diglycolic acid. Here, the stabilizer may be included in the electroless nickel plating solution composition by mixing one or more than two.

The composition range of the stabilizer may have a 0.0001 to 0.1% by weight based on the total weight of the electroless nickel plating solution composition. Preferably, the composition range of the stabilizer may have 0.001 to 0.01 wt% based on the total weight of the electroless nickel plating solution composition. At this time, when the composition of the stabilizer is less than 0.0001% by weight, it is difficult to achieve the stability of the plating liquid and the refinement of crystal grains. In addition, when the composition of the stabilizer exceeds 0.1% by weight, activation of the plating liquid is delayed, which may cause unplating.

The pH range of the electroless nickel plating solution composition may have 4 to 6 in consideration of the speed, reduction efficiency and stability of the plating.

Here, when the electroless nickel plating solution composition further includes an additive such as an organic acid and an alkali salt thereof, a surfactant, a stabilizer, and a monosaccharide in addition to the vertical growth inducing agent, the most distinct vertically grown nickel plated layer may be obtained.

Hereinafter, a flexible printed circuit board using the electroless nickel plating solution composition described above with reference to the drawings and a manufacturing method thereof will be described in more detail. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of the device may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a plan view of a flexible printed circuit board according to a second exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of the flexible printed circuit board of FIG. 1.

1 and 2, the flexible printed circuit board is a substrate 100 having a circuit pattern formed thereon, a pad portion 110 electrically connected to the circuit pattern, and an electronic component mounted thereon, and electrically connected to the circuit pattern. It may include an external connection portion 120, 130 electrically connected to the external device.

The external connectors 120 and 130 may be connected to an external device, for example, a terminal unit 120 electrically connected to the liquid crystal panel by ACF bonding, and a connector unit formed to be electrically connected to the external device by a detachable method. 130).

Nickel plating layers 150 having a vertical growth structure are disposed on the pad part 110 and the external connection parts 120 and 130, respectively. The nickel plating layer 150 may impart good weldability to the pad part 110 and impart crack resistance to the external connection parts 120 and 130. That is, the nickel plating layer 150 may have good weldability and crack resistance at the same time.

The nickel plating layer 150 may be formed from an electroless nickel plating solution composition including a water-soluble nickel compound, a reducing agent, a complexing agent, and a vertical growth inducing agent. Here, the vertical growth inducing agent may be a compound containing bismuth ions. In addition, the electroless nickel plating solution composition may further include a vertical growth aid consisting of at least one or two or more selected from the group consisting of thallium ions, iron ions and copper ions.

Specifically, the composition range of the water-soluble nickel compound based on the total weight of the electroless nickel plating solution composition has a 1.0 to 10.0% by weight, the composition range of the reducing agent has a 1.0 to 10.0% by weight, the composition of the complexing agent The range is 1.0 to 10.0% by weight, the composition range of the vertical growth inducing agent may have a 0.001 to 1.0% by weight. In addition, the electroless nickel plating layer composition may include a metal ion blocking agent having a composition range of 0.01 to 1.0 wt%, an organic acid having at least one carboxyl group (-COOH) having a composition range of 0.1 to 10.0 wt%, and an alkali thereof. The metal salt may further include a stabilizer having a composition range of 0.1 to 10.0 wt%, 0.0001 to 0.1 wt%, a surfactant having a composition range of 0.01 to 10.0 wt%, and a monosaccharide having a composition range of 0.1 to 10.0 wt%.

Here, the nickel plating layer 150 may include nickel having a composition range of 90 to 94% by weight and phosphorus having a composition range of 6 to 10% by weight. In this case, when the composition of the phosphorus is less than 6% by weight, a problem may occur in the corrosiveness of the nickel plating layer 150. On the other hand, when the composition of the phosphorus exceeds 10 weight, there is a problem that the weldability is lowered.

In addition, the nickel plating layer 150 may have a thickness range of 1 to 5㎛. Here, preferably, the nickel plating layer 150 may have a thickness range of 1.5 to 35 μm. However, in the embodiment of the present invention, the thickness of the nickel plating layer is not limited.

In addition, the gold plating layer 160 may be further disposed on the nickel plating layer 150. The gold plating layer 160 may prevent oxidation of the nickel plating layer 150, thereby improving reliability of the flexible printed circuit board.

In addition, the pad unit 110 may further include an insulating layer 140 disposed on the substrate 100 to expose the external connection units 120 and 130. The insulating layer 140 may serve to protect a circuit pattern formed on the substrate 100 during the plating process.

Therefore, the flexible printed circuit board according to the embodiment of the present invention has a nickel plated layer having a vertical growth structure capable of simultaneously satisfying the weldability of the pad part and the crack resistance of the external connection part, thereby ensuring reliability through a simple manufacturing process. The flexible printed circuit board can be manufactured.

3 to 6 are cross-sectional views illustrating a method of manufacturing a flexible printed circuit board according to a third embodiment of the present invention.

Referring to FIG. 3, to manufacture a flexible printed circuit board, first, a circuit pattern, a pad part 110, and external connection parts 120 and 130 are formed on a substrate 100. Here, examples of the external connection parts 120 and 130 may be the terminal part 120 and the connector 130. The circuit pattern, the pad part 110 and the external connection parts 120 and 130 may be formed using a conventional photolithography method.

Referring to FIG. 4, the insulating layer 140 is formed on the substrate 100 while exposing the pad part 110 and the external connection parts 120 and 130. The insulating layer 140 serves as a resist for plating in the plating process which will be described later. The insulating layer 140 may be formed by punching and thermocompression. However, the present invention is not limited to the method of forming the insulating layer 140.

Referring to FIG. 5, the nickel plating layer 150 is formed by contacting and depositing a substrate 100 including the pad part 110 and the external connection parts 120 and 130 to an electroless nickel plating solution.

The electroless nickel plating solution composition may include a water soluble nickel compound, a reducing agent, a complexing agent, and a vertical growth inducing agent. Specifically, the electroless nickel plating solution composition is 1.0 to 10.0% by weight of water-soluble nickel compound, 1.0 to 10.0% by weight of reducing agent, 1.0 to 10.0% by weight of complexing agent, 0.01 to 1.0% by weight of metal ion blocking agent, organic acid And 0.1 to 10.0 wt% of alkali metal salt thereof, 0.0001 to 0.1 wt% of stabilizer, 0.01 to 10.0 wt% of surfactant, 0.1 to 10.0 wt% of monosaccharide, and 0.001 to 1.0 wt% of vertical growth inducing agent.

In the present invention, the pH of the plating liquid may be 4 to 6, preferably 4.5 to 5.0. In addition, the temperature required in the plating process may be 70 to 95 ℃, preferably 80 to 85 ℃.

The nickel plating layer 150 is formed of a vertical growth type nickel structure by a vertical growth inducing agent. At this time, in the nickel plating layer 150, nickel is included in the composition range of 90 to 94% by weight, phosphorus (P) may be included in the composition range of 6 to 10% by weight.

The thickness of the nickel plating layer 150 may be 1 to 5㎛, preferably 1.5 to 3.0㎛.

The plating process for forming the nickel plating layer 150 may be performed for about 10 to 20 minutes.

Referring to FIG. 6, the gold plating layer 160 may be further formed on the substrate 100 including the nickel plating layer 150 by immersion plating.

The reaction principle for forming the gold plated layer 160 is shown in the following scheme 4.

Scheme 4

As in Scheme 4, when a nickel-plated surface is contacted with an aqueous solution containing citric acid and potassium gold cyanide, the dissolution reaction of nickel and the precipitation reaction of gold (Au) proceed simultaneously to the gold plating. Layer 160 may be formed.

In addition, before forming the nickel plating layer 150, in order to form the optimal vertical growth type nickel plating layer 150, a pretreatment process may be selectively performed during the plating process. That is, first, the pad part 110 and the external connection parts 120 and 130 are physically polished to remove foreign substances on the surface and chemically remove organic substances. In addition, the surface of the copper layer constituting the pad portion 110 and the external connection portion 120 and 130 is etched by about 1 μm using sulfuric acid and an oxidizing agent and then treated with a palladium (Pd) solution that selectively serves as a catalyst. Activation process is possible.

Therefore, in the embodiment of the present invention, by forming an electroless nickel plating layer having a vertical growth structure capable of satisfying all the plating characteristics required for each of the pad part and the external connection part, the flexible printed circuit board may be manufactured through a simple process. have.

Hereinafter, the flexible printed circuit board according to the exemplary embodiment of the present invention will be described in more detail through experimental examples. However, the scope of the present invention is not limited thereto.

In the following experimental example, a flexible printed circuit board (size 400 × 505 mm, thickness 0.2 ± 0.02 mm, copper layer thickness 10-30 μm) and a ball shear having an insulating layer formed on a portion except for a pad portion, a terminal portion, and a connector portion made of copper material Flexible printed circuit board for measuring strength (size 50mm wide x 80mm long, board thickness 0.2 ± 0.02mm, copper layer thickness 10-30㎛) and MIT coupon for bending test (circuit width 100㎛ x spacing 100㎛, size 10mm x 100 mm, copper layer thickness 12 μm, substrate 100 thickness 25 μm, material polyimide), degreased with acid at 50 ° C. for 3 minutes (sulfuric acid concentration of 50-100 g / L, YMT Co., Ltd. SAC 161H) It was. Then, pickling and etching (30 g / L sulfuric acid, 100 g / L sodium persulfate) to remove the oxide film and to form the roughness of the copper surface, and then catalyzed by palladium (Pd) ion (trade name CF Activator of YMT Co., Ltd.) Treatment was followed by washing with water. Thereafter, a vertically grown electroless nickel plating process was performed on the copper layer as follows. Then, it was immersed at 85 ° C. for 6 minutes in a immersion plating solution (trade name MIKO Auromerse II manufactured by WMT Co., Ltd.) based on citric acid. A gold plated layer was formed on the vertically grown electroless nickel plated layer.

TABLE 1

Experimental Example

After preparing a vertically grown electroless nickel plating solution having the composition shown in Table 1, the flexible printed circuit board treated with palladium (Pd) catalyst was washed with water, and then immersed in a 5 wt% sulfuric acid solution for 1 minute and washed with water. Thereafter, electroless nickel plating was performed using the vertically grown electroless nickel plating solution. At this time, the temperature of the electroless nickel plating solution was 82 ° C, the plating time was 15 minutes, the pH was 4.5, and the liquid circulation amount was plated at 3 revolutions / hour.

The electroless nickel plated layer was formed and washed with water in the same manner as described above and dried at 80 ° C. for 15 minutes. Thereafter, the plating thickness, weldability, flex resistance, adhesion, porosity, and heat resistance of the electroless nickel plating layer were measured.

Plating thickness measurement

The measuring equipment used was as follows and the results are shown in Table 2.

* measuring equipment

-. Manufacturer: Oxford Instrument

-. Model Name: CMI 900

-. Measuring pad size 1 x 1 mm

<Measurement of Solderability>

Weldability was performed by the solder ball shear test and the solder spread test under the following conditions, and the results are shown in Table 3 below.

1) solder ball shear test

* Condition :

Bond Tester: DAGE 4000

Location: 100 ㎛

Shear Speed: 700㎛ / sec

Load: 5 kgf

-Ball Size: 0.4mmΦ (Alpha Metal Co.)

-Ball Material: Sn / Ag / Cu (96.5 / 3 / 0.5) Weight%

Flux (RMA type): WF-6063M (Senju Co.)

Reflower: Heller (1809 UL)

-Reflow condition: 245 ℃ (peak temperature)

* Assessment Methods :

This is to measure the connection strength between soldering pad and solder ball. When the ball shear test is performed by fixing a specimen with solder bumps on the table under the above conditions and setting a constant load and shear height, the stylus The breakage occurs by pushing the bump, and the value is then measured.

* Evaluation standard :

-If ball shear strength exceeds 600gf, no abnormality is assumed.

2) Solder Paste Spreadability Test

* Condition :

Solder paste: Sn / Ag / Cu (96.5 / 3 / 0.5) wt% (Senju Co.)

Reflower: Heller (1809 UL)

-Reflow condition: 245 ℃ (peak temperature)

* Assessment Methods :

After applying solder paste to the soldering pad part, it passes through a reflow machine and measures the solder spreadability in a pad part.

* Evaluation standard :

If reflowing more than 95% of the soldering pad portion, the weldability is not abnormal.

<Flexibility Measurement>

While performing the bending test under the measurement conditions as described below, the number of occurrences of disconnection due to cracks in the circuit was measured, and the results are shown in Table 4.

* Measuring conditions

Load: 500 g

Bending radius: 0.38 mm

Speed: 175 times / minute

-Bending angle: 270 ° (135 °)

Measurement mode: single line evaluation

* Test specimen

-Thickness: 25㎛ polyimide, 12㎛ copper (electric copper foil)

* measuring equipment

*-Manufacturer: TOYOSEIKI

-Model Name: MIT-DA

<Measurement of adhesion>

After pressing the 3M # 810 tape on the plated surface with acupressure, it was removed in the vertical direction to check whether the plated layer was in close contact. The results are shown in Table 5.

<Porosity test>

After plating the flexible printed circuit board coated with 12 wt% nitric acid solution for 15 minutes, it was confirmed whether or not pores were generated by corrosion of nickel and gold plated tissue under a microscope. The results are shown in Table 5 below.

<Heat resistance measurement>

After three passes using a reflow machine, nickel-gold plating was used to check whether the surface was oxidized by heat, whether it was corroded by a close test using a tape, and the results are shown in Table 5.

Table 2 Plating Thickness Measurement Results

<Table 3> Result of weldability measurement (solder ball shear strength)

Table 4 Measurement of Flexibility

<Table 5> Property Evaluation Results

In Table 5, the mark "○" means that the test result specification is satisfied.

In view of the results of Table 5 in Table 2, it was confirmed that the vertically grown nickel plated layer and the gold plated layer according to the embodiment of the present invention satisfy both weldability and crack resistance.

7 is a photograph showing the fracture surface of the electroless nickel plating layer having the vertical growth structure according to the embodiment of the present invention.

8 is a photograph showing the fracture surface of the electroless nickel plating layer having the vertical growth structure according to the comparative example of the present invention.

As shown in FIG. 7 and FIG. 8, when the vertical growth inducing agent was provided, it was confirmed that the vertical growth structure had a horizontal structure.

Accordingly, in the embodiment of the present invention, the pad portion, the external connection portion of the flexible printed circuit board provided according to the present invention, that is, satisfy all the plating characteristics required for each of the terminal portion and the connector portion, and at the same time the conventional flexible printed circuit board The double plating process of normal electroless nickel and direct gold plating performed during manufacture could be replaced by a single plating process. As a result, the production process of the flexible printed circuit board was simplified and the productivity was improved, and the cost reduction was also possible.

In addition, the electroless nickel plating solution composition according to an embodiment of the present invention has been described as being used to manufacture a flexible printed circuit board, but is not limited thereto and may be applied to all kinds of printed circuit boards.

100 substrate 110 pad portion
120: terminal portion 130: connector portion
140: insulating layer 150: nickel plating layer
160: gold plated layer

Claims (23)

An electroless nickel plating solution composition comprising a vertical growth inducing agent comprising a water-soluble nickel compound, a reducing agent, a complexing agent and a compound having bismuth ions.
The method of claim 1,
The composition range of the vertical growth inducing agent has an electroless nickel plating solution composition having a 0.001 to 1% by weight based on the total content of the electroless nickel plating solution composition.
The method of claim 1,
An electroless nickel plating solution composition further comprising a vertical growth aid comprising at least one or two or more selected from the group consisting of thallium ions, iron ions, and copper ions.
The method of claim 1,
The water-soluble nickel compound is an electroless nickel plating solution composition containing at least one of nickel sulfate and nickel chloride.
The method of claim 1,
The composition range of the water-soluble nickel compound has an electroless nickel plating solution composition having 1 to 10% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 1,
The reducing agent is an electroless nickel plating liquid composition comprising at least one selected from the group consisting of hypophosphite, potassium hypophosphite, hydrazine and sodium hypophosphite.
The method of claim 1,
The composition range of the reducing agent has an electroless nickel plating solution composition having 1 to 10% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 1,
The complexing agent is an electroless nickel plating solution composition comprising at least one or two or more selected from the group consisting of lactic acid, glycolic acid and malic acid.
The method of claim 1,
The composition range of the complexing agent has an electroless nickel plating solution composition having 1 to 10% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 1,
An electroless nickel plating solution composition further comprising at least one of a metal ion sequestrant, an organic acid and an alkali metal salt thereof, a monosaccharide, a surfactant, and a stabilizer.
The method of claim 10,
The metal ion sequestrant may be at least one selected from the group consisting of derivatives of polycarboxylic acid, derivatives of amino acetic acid and derivatives of nitrilo-triacetic acid. Electroless nickel plating solution composition comprising.
The method of claim 10,
The composition range of the metal ion blocking agent has an electroless nickel plating solution composition having 0.01 to 1% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 10,
The organic acid and the alkali metal salt of the organic acid are acetic acid, sodium acetate, propionic acid, sodium propionate, formic acid, sodium hydroxide, potassium hydroxide (electrode) containing at least one or two or more selected from the group consisting of (potassium formate), adipic acid, sodium adipate, succinic acid, sodium succinate, and the like Nickel plating solution composition.
The method of claim 10,
The composition range of the organic acid and the alkali metal salt of the organic acid has an electroless nickel plating solution composition having 0.1 to 10% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 10,
The monosaccharide is an electroless nickel plating liquid composition comprising at least one or two or more selected from the group consisting of glucose, fructose and galactose.
The method of claim 10,
The composition range of the monosaccharide has an electroless nickel plating solution composition having 0.1 to 10% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 10,
The surfactant is an electroless nickel plating solution composition which is a polyoxyethylene alkyl ether derivative.
The method of claim 10,
The surfactant may be polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyoxyethylene octyl ether, At least one selected from the group consisting of polyoxyethylene tridecyl ether, polyoxyethylene laurylamine ether and polyoxyethylene stearylamine ether; An electroless nickel plating solution composition.
The method of claim 10,
The composition range of the surfactant has an electroless nickel plating solution composition having 0.01 to 10% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 10,
The stabilizer is a thio compound electroless nickel plating solution composition.
The method of claim 10,
The stabilizer is thiourea, alkyl thiourea, mercapto compound, thiazole compound, sodium thiosulfate, sodium thiocyanate, thiocyanate An electroless nickel plating solution composition comprising at least one or two or more selected from the group consisting of potassium thiocyanate, thio glycolic acid, and thio diglycolic acid.
The method of claim 10,
The composition range of the stabilizer is an electroless nickel plating solution composition having a 0.0001 to 0.1% by weight based on the total composition of the electroless nickel plating solution.
The method of claim 1,
The electroless nickel plating solution composition has a pH range of 4 to 6 electroless nickel plating solution composition.

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