KR20050078918A - Method for forming hole of flexible printed circuit board - Google Patents

Abstract

The present invention relates to a method for forming a hole for conduction or insertion of a component during a manufacturing process of a printed circuit board, the configuration of which comprises: a first of cutting a copper foil with polyimide into a sheet having an appropriate size; fair; A second step of corroding the copper foil of the processed portion from the copper foil to which the polyimide is attached; A third step of etching the polyimide resin exposed by the corrosion of the copper foil by using a composition liquid containing an aliphatic amine, an alkali metal compound, a solvent, water, and an additive; A fourth step of applying electroless or electrolytic copper plating to the holes formed after the third step to energize each layer; Characterized in that it comprises a.

According to the present invention, since the hole is formed by a chemical method, process time and cost are saved, and the hole can be precisely formed.

Description

Method for forming hole of Flexible Printed Circuit Board

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a hole for conducting or inserting a component during a manufacturing process of a printed circuit board, and more particularly, a via hole of a flexible printed circuit board using a chemical method. Or a method of forming a through hole.

In general, a printed circuit board is coated with copper foil on an insulating substrate, and may be classified into a single-sided printed circuit board, a double-sided printed circuit board, a multilayer printed circuit board, and the like, and the insulating material is a paper-phenol resin or an epoxy resin. Rigid Printed Circuit Boards and the like, and Flexible Printed Circuit Boards using flexible resins resistant to heat such as polyimide. Conventionally, rigid rigid printed circuit boards have been mainly used, but recently, flexible printed circuit boards are frequently used.

Through-holes or via-holes are formed in the flexible printed circuit board to conduct or insert components. Various methods for hole-processing the polyimide resin have been applied. It can be divided into dry technology such as mechanical drill method, plasma dry etching and laser processing method and wet technology using etching chemicals. Among them, through-hole formation using dry technology is generally performed by forming a hole using a CNC drill on a base of flexible copper clad laminated (polyimide), and performing electroless copper plating and electrolytic copper plating. It plays a role of connecting signal.

In addition, the method for forming the via hole is specifically disclosed in Korean Patent No. 0313612, which is configured to oxidize copper foil of a substrate to change the copper foil surface to black, and then use a CO ₂ type laser drill. By forming blind via holes in the substrate, it is possible to not only drill holes in the copper foil using a CO ₂ type laser drill, but also improve the productivity of the drilling process.

As such, the recent dry technology has brought technical improvements such as increasing the precision of micromachining.However, a surface coated with melamine or the like is placed on the base plate of the drilling machine, and the printed circuit board is laminated thereon, and then a hole is placed at a designated position. In order to prevent the burr phenomenon generated when the hole is punched in the printed circuit board, the board is generally made of a board coated with a special surface such as melamine. In the process of drilling the printed circuit board by the drill bit of the drilling machine, a groove or a hole is generated by the drill bit in the board below the hole where the hole is formed, and when reuse, the drill bit is again placed in the place where the groove or the hole is formed. The perforation of the board causes the occurrence of burrs on the printed circuit board, thereby producing a low quality printed circuit board. It was not reused and disposed of. Therefore, as described above, the hole forming method using the drilling machine is a waste that is not recycled, and the board that is disposed of is used as a waste of expensive coated melamine treatment, and the board is coated with expensive drill equipment. Therefore, the processing cost is very high. In addition, when using a drilling machine it is difficult to process a complex shape, takes a lot of hole formation time, and in particular, the more holes to be processed, the longer the machining time.

Accordingly, in recent years, wet technology is generally used rather than dry technology. As a composition liquid for etching such a polyimide resin, a composition liquid using hydrazine hydrate, a composition liquid mainly containing quaternary ammonium hydroxide, and the like have been introduced. However, these compositions were difficult to use practically due to problems such as toxicity of components, effects on the working environment, and etching speed. In addition, since the polyimide resin exhibits various physical properties depending on the manufacturing process and components, the degree of etching varies depending on the type of polyimide resin. Therefore, there is a need for development of a composition liquid having excellent etching property on various kinds of polyimide resins.

The present invention has been made to solve the above problems, an object of the present invention is to provide a hole forming method of a flexible printed circuit board that can save the processing cost and processing time using a chemical method.

Another object of the present invention is to provide a hole forming method of a flexible printed circuit board using a composition liquid having excellent etching property on various kinds of polyimide resins.

In order to solve the above technical problem, a hole forming method of a printed circuit board according to the present invention includes a first step of cutting a copper foil with polyimide into a sheet having an appropriate size; A second step of corroding the copper foil of the processed portion from the copper foil to which the polyimide is attached; A third step of etching the polyimide resin exposed by the corrosion of the copper foil by using a composition liquid containing an aliphatic amine, an alkali metal compound, a solvent, water, and an additive; A fourth step of applying electroless or electrolytic copper plating to the holes formed after the third step to energize each layer; It is made, including.

Further, in the hole forming method of the printed circuit board of the present invention, the second step is to adhere the dry film to the copper foil to which the polyimide is attached, and to expose and develop to remove the dry film of the processed portion, It is preferable to peel off the dry film which remain | survives after corroding copper foil.

In addition, in the hole forming method of the printed circuit board of the present invention, the additive contained in the composition is preferably at least one selected from the group consisting of inorganic salts, organic acids and surfactants.

In the hole forming method of the printed circuit board of the present invention, the composition liquid is 3 to 75% by weight of aliphatic amine, 5 to 47% by weight of alkali metal compound, 0.1 to 7% by weight of solvent, 0.01 to 42% by weight of additive, It is preferred to include water.

In the hole forming method of the printed circuit board of the present invention, the aliphatic amine contained in the composition is preferably a water-soluble monovalent, divalent amine having a amino group or an amino group and a hydroxyl group, or a mixture thereof.

In addition, in the hole forming method of the printed circuit board of the present invention, the alkali metal compound contained in the composition is preferably at least one selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide.

In addition, in the hole forming method of the printed circuit board of the present invention, the solvent contained in the composition solution is N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, γ-butyrolactone, morpholine, N- It is preferably at least one selected from the group consisting of cyclohexyl-2-pyrrolidone, 1,4-butanediol, 1,4-butenediol, 1,4-butyndiol.

In addition, in the hole forming method of the printed circuit board of the present invention, the inorganic salt contained in the additive is preferably at least one selected from the group consisting of carbonate, nitrate, sulfide, sodium hypochlorite and ammonium chloride.

In addition, in the hole forming method of the printed circuit board of the present invention, the organic acid included in the additive is preferably any one or a mixture of gallic acid and pyrogarol.

In addition, in the hole forming method of the printed circuit board of the present invention, the surfactant included in the additive is preferably a pyrrolidone system.

In addition, in the hole forming method of the printed circuit board of the present invention, it is preferable to etch the polyimide resin by any one of immersion method, spraying method, ultrasonic irradiation method and stirring method or a mixture thereof.

In addition, in the hole forming method of the printed circuit board of the present invention, it is preferable to use a process temperature in the range of 40 to 90 ° C and a process time in the range of 1 to 15 minutes when etching the polyimide resin.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and operation of the present invention.

1 is a shape of a hole formed in a flexible printed circuit board. The flexible printed circuit board is a copper foil (2) coated on an insulating substrate such as polyimide (1), as shown, through-hole shown in Figure 1a as needed to form a hole for conduction or component insertion, Or via holes shown in FIG. 1B.

2 schematically illustrates a through hole forming process of a flexible printed circuit board according to the present invention.

FIG. 2A illustrates a state in which a flexible copper clad laminated sheet of polyimide is first cut into an appropriately sized sheet to form a hole in a flexible printed circuit board.

FIG. 2B shows a state in which a dry film (photosensitive film) is closely adhered to both surfaces of the cut polyimide-attached copper foil. The close contact of the dry film is to remove the copper foil of the portion where the hole is to be formed and to expose the polyimide substrate of the portion.

FIG. 2C shows a state in which part of the dry film 3 (a site in which a hole is to be formed) is attached to the copper foil to which the polyimide is attached. This is performed by exposing to a portion other than the portion where the hole is to be formed in the dry film 3 in close contact with (b) for a suitable time, and then immersing the substrate in a developer. After such an operation, an unnecessary part (processing part) is melt | dissolved as shown, and the copper foil 2 is exposed to the outside.

2D shows a state in which the copper foil 2 at the portion where the hole is to be formed is removed. That is, in FIG. 2C, the dry film 3 of the processed portion is removed, and then the substrate is immersed in a copper corrosion solution to chemically scrape away the exposed copper foil 2. As shown through this process, it is possible to remove the copper foil (2) at the position where the hole is to be formed.

2E shows a state in which the dry film 3 is peeled off. Peeling the dry film 3 is by the method normally used conventionally.

2F shows a state where the polyimide resin 1 is etched. When the copper foil is removed by the above process, the polyimide resin 1 is exposed, and in this state, the polyimide base material 1 is etched by immersing the composition liquid, spraying, or spraying in the liquid. The said composition liquid is mentioned later.

FIG. 2G shows a state where the plated 4 is plated in the through hole formed in the substrate. After the formation of the through hole completed through the above process, the electroless copper plating is performed after the electroless or direct plating on the hole to conduct electricity to each layer, and then go through the circuit forming process.

In FIG. 2, only the through-hole forming method is illustrated, but the via-holes may be processed by total exposure of the cross-section during the process. That is, the dry film 3 is adhered to the copper foil with polyimide to be exposed and developed, and the substrate from which the dry film 3 of the unnecessary portion is removed is dipped in a copper corrosion solution to remove the copper foil, and then the composition liquid is deposited by a method such as deposition. The via holes can be formed in the flexible printed circuit board by scanning and etching and plating the polyimide resin 1.

Hereinafter, the composition liquid for etching the polyimide resin will be described.

The composition liquid comprises an aliphatic amine, an alkali metal compound, a solvent, water, and an additive.

The aliphatic amine is a composition for promoting alkali penetration into the polyimide resin and eluting the hydrolysis product of the resin. In the present invention, a water-soluble monovalent, divalent amine having a amino group or an amino group and a hydroxyl group is used. . Specifically, cyclohexylamine, hydroxylamine, n-butylamine, isopropylamine, diethylamine, dibutylamine, triethylamine, ethylenediamine, triethylenediamine, tetramethyldiamine, pentamethylenediamine, hexamethylenediamine Amines and mixtures thereof can be used. The concentration of such aliphatic amines is preferably in the range of 3% by weight to 75% by weight, especially 8% by weight to 40% by weight. If the concentration of the amine is too low, it is difficult to obtain the desired physical properties by reducing the etching rate, and even at a concentration of 75% by weight or more does not show a significant increase in the etching rate because it is disadvantageous in terms of economics.

The alkali metal compound is a composition for resin swelling and resin etching, specifically, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc. may be used. Among them, potassium hydroxide, which can obtain economical etching rate, is most preferable. Metal compounds and mixtures thereof can also be used. These may be used up to a saturation concentration at 5% to the use temperature, but preferably includes a concentration of 5% to 47% by weight, more preferably 15% to 45% by weight. At low concentrations, the etching rate is slow and it takes a long time, so it is easy to break the pattern and it is uneconomical. If the concentration is too high, the viscosity of the solution rises, handling is difficult, and when the temperature is low, the pipes may be precipitated and become clogged.

The solvent swells the resin to speed up the etching rate and the composition for the removal of the etching residue, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, γ-butyrolactone, morpholine, N-cyclo Hexyl-2-pyrrolidone, 1,4-butanediol, 1,4-butenediol, 1,4-butynediol, and the like can be used, and the content is 0.1% to 7% by weight, more preferably 0.5% by weight. To 5% by weight. If the concentration is less than 0.1% by weight, the effect on the etching rate is very small, and even if it is added in excess of 7% by weight, no significant increase in the etching rate is observed.

 The additive is at least one substance selected from the group consisting of an inorganic salt, an organic acid and a surfactant, and in combination, 0.01 wt% to 42 wt% is preferred.

The inorganic salt is a composition for swelling the resin to increase the etching rate and remove the etching residues, such as carbonates such as potassium carbonate and sodium carbonate, nitrates such as sodium nitrite, sodium nitrate, ammonium nitrate and potassium nitrate, and thiourea Sulphides and chlorides such as sodium hypochlorite and ammonium chloride are used. When the inorganic salt is added to the composition liquid as an additive, the concentration is preferably 1% by weight to 35% by weight, and more preferably 5% by weight to 30% by weight. If the inorganic salt is less than 1% by weight, the influence on the resin swelling and etching is insignificant, and if it exceeds 35% by weight, it may be precipitated and separated.

In addition, the organic acid swells the resin to speed up the etching rate, and in the present invention, a gallic acid, pyrogarol, or the like is used as a composition for removing the etching residue. When adding an organic acid as an additive to the composition liquid, it is preferable to use in the range of 0.5% by weight to 2% by weight.

The surfactant is a composition for increasing the penetration force of the composition liquid into the hole to be etched. Since the composition liquid is a strong alkali, there are many limitations in the selection of a surfactant which does not decompose even in such a composition and exhibits desired characteristics. In the present invention, a pyrrolidone-based surfactant is used, and among these, n-alkylpyrrolidone-based surfactants are selected in the range of 0.01% by weight to 5% by weight, preferably 0.1% by weight to 3% by weight. Add. If the concentration is too low, it does not exhibit the required properties, and even when added too much, there is no noticeable performance improvement.

When etching the polyimide resin using the composition liquid as described above, the working temperature is preferably between 40 ℃ to 90 ℃, preferably 65 ℃ to 85 ℃, the etching time is in the range of 1 to 15 minutes is appropriate. . As an etching method, a polyimide resin can be etched using immersion method, the spraying method, the ultrasonic irradiation method, and the stirring method, respectively, or two or more of these methods are mixed and used.

<Example 1>

The result of immersing the polyimide resin which formed the through-hole in the composition liquid which consists of 20 weight% of hydroxylamine, 30 weight% of potassium hydroxide, 0.5 weight% of 1,4 butyne diols, 5 weight% of sodium hypochlorite, and the remainder at 80 degreeC After 3 minutes and 20 seconds, the hole was completely etched.

<Example 2>

A through-hole was formed in the composition consisting of 25% by weight of ethylenediamine, 35% by weight of potassium hydroxide, 0.7% by weight of N-methyl-2-pyrrolidone, 15% by weight of thiourea, 0.1% by weight of n-octylpyrrolidone and the remaining water. The polyimide resin thus formed was immersed at 80 ° C., and the holes were completely etched after 2 minutes and 5 seconds.

<Example 3>

Polyi formed through holes in the composition consisting of 18% by weight of cyclohexylamine, 35% by weight of potassium hydroxide, 1% by weight of γ-butyrolactone and 1% by weight of gallic acid, 0.3% by weight of n-octylpyrrolidone and the remaining water After dipping the mid resin at 75 ° C., the holes were completely etched after 2 minutes and 45 seconds.

Comparative Example

The result of immersing the polyimide resin in which the through-hole was formed at 80 ° C. for 20 minutes was added to 6 wt% of potassium hydroxide in a solution of ethyl alcohol and water prepared according to US Pat. No. 4,426,253 at a ratio of 4: 1. Even after the elapse of time, the polyimide resin swelled a little but the holes were not etched.

According to the present invention, since the hole is formed in the flexible printed circuit board using a chemical method rather than a mechanical method, processing cost and processing time can be saved.

In addition, the polyimide resin composition according to the present invention can be applied to various types of polyimide resin, and also has excellent effect of etching.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the present invention, and such modifications and variations belong to the appended claims.

1 illustrates a shape of a hole formed in a printed circuit board, in which FIG. 1A is a through hole and FIG. 1B is a via hole.

2A to 2G schematically illustrate a hole forming process of a printed circuit board according to the present invention.

<Description of the symbols for the main parts of the drawings>

1: polyimide resin 2: copper foil

3: dry film 4: plating layer

Claims (12)

A first step of cutting the copper foil with polyimide into a sheet having an appropriate size; A second step of corroding the copper foil of the processed portion from the copper foil to which the polyimide is attached; A third step of etching the polyimide resin exposed by the corrosion of the copper foil by using a composition liquid containing an aliphatic amine, an alkali metal compound, a solvent, water, and an additive; A fourth step of applying electroless or electrolytic copper plating to the holes formed after the third step to energize each layer; Hole forming method of a printed circuit board comprising a. The method of claim 1, In the second step, the dry film is brought into close contact with the copper foil to which the polyimide is attached, the exposure and development are performed to remove the dry film of the processed portion, and the copper foil of the exposed portion is corroded, and the remaining dry film is peeled off. The hole forming method of the printed circuit board. The method of claim 1, The additive included in the composition solution is at least one selected from the group consisting of inorganic salts, organic acids and surfactants. The method of claim 1, The composition of the printed circuit board, characterized in that it comprises 3 to 75% by weight of aliphatic amine, 5 to 47% by weight of alkali metal compound, 0.1 to 7% by weight of solvent, 0.01 to 42% by weight of additives, and water as the remaining amount. Hole formation method. The method according to claim 1 or 4, The aliphatic amine contained in the composition is a water-soluble monovalent, divalent amine having a amino group or an amino group and a hydroxyl group, or a mixture thereof. The method according to claim 1 or 4, The alkali metal compound included in the composition is at least one or more selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide. The method according to claim 1 or 4, The solvent contained in the composition is N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, γ-butyrolactone, morpholine, N-cyclohexyl-2-pyrrolidone, 1,4-butanediol At least one selected from the group consisting of 1,4-butenediol and 1,4-butynediol. The method according to claim 1 or 3, The inorganic salt included in the additive is at least one selected from the group consisting of carbonate, nitrate, sulfide, sodium hypochlorite and ammonium chloride. The method according to claim 1 or 3, The organic acid included in the additive is a hole forming method of the printed circuit board, characterized in that any one or a mixture of gallic acid and pyrogarol. The method according to claim 1 or 3, The surfactant included in the additive is a method for forming a hole in the printed circuit board, characterized in that the pyrrolidone system. The method of claim 1, The polyimide resin is etched by any one of immersion method, spraying method, ultrasonic irradiation method and stirring method, or a mixture thereof, to form a hole in the printed circuit board. The method of claim 1, And a process temperature in the range of 40 to 90 ° C. and a process time in the range of 1 to 15 minutes during etching of the polyimide resin.