KR20200133516A - Method for manufacturing of an electrically insulated circuit board - Google Patents

Abstract

Provided is a method for manufacturing a circuit board. According to one embodiment of the present invention, a circuit board can be manufactured through the following steps: (1) preparing a circuit board having an electrode installed at a predetermined height and width on a substrate; (2) electrospinning a solder resist forming solution to cover the circuit board in the upper part of one surface, from which the electrode is exposed, of the circuit board; and (3) solidifying the electrospun solder resist forming solution to form a solder resist layer. Accordingly, a manufacturing process for forming a welding prevention cover on a circuit board is easier than an existing manufacturing method and a manufacturing time can be also reduced. Moreover, the manufactured cover can be thinly implemented and thickness uniformity is excellent, thereby providing excellent coating quality. Moreover, a coating error, such as overflow of a coating layer out of a boundary of a selection area in which the coating layer is formed or forming a coating layer not reaching the boundary, is minimized or prevented, such that defects caused by the coating error are effectively prevented in the following SMT process, and thus the method is suitable for increasing the reliability and quality of the circuit board.

Description

Circuit board manufacturing method {Method for manufacturing of an electrically insulated circuit board}

The present invention relates to a method for manufacturing a circuit board.

Solder resist refers to an insulating film that covers a part hole to be soldered on a circuit board or a wiring circuit other than a surface mount mechanism to prevent unintended connection from occurring due to soldering made during component mounting. The solder resist prevents short circuits, lamination, corrosion, contamination, etc. of the circuit board circuit, and plays a role of protecting the circuit from external shock, moisture, and chemical substances by being continuously provided on the circuit board. The solder resist sheet is a direct printing imaging method implemented by selectively treating a solder resist forming solution directly onto a circuit board according to an image method, or by treating the solder resist forming solution on the entire surface of the circuit board and then exposing and leaving only a desired part. It can be divided into photographic imaging methods that are developed and implemented.

In the case of the photographic imaging method, a masking process, an exposure process, and a developing process must be performed to leave only a desired part, so the manufacturing process is complicated and the manufacturing time may be prolonged. In addition, in the case of a space between electrodes having a narrow pitch gap and a low electrode thickness according to the photographic imaging method, it is not easy to perform elaborate exposure work, and there is a problem that a residue may remain after development.

Accordingly, in recent years, there have been increasing attempts for direct printing imaging, an example of which is the screen printing method. However, in the screen printing method, after the solder resist forming solution is applied to the area to be coated with the solder resist, there is a problem in that the solder resist forming solution spreads along the electrode to the place where the solder resist should not be formed due to flow. In addition, there is a problem that the solder resist boundary is formed so that the solder resist boundary does not reach the region where the solder resist is to be formed, so that an open region of the electrode is generated, and thus soldering is formed on the electrode to which the solder should not be formed in the SMT process.

Accordingly, by solving the problems of the conventional manufacturing method as described above, the manufacturing process is very easy, the manufacturing time is shortened, and while implementing a thin and uniform coating layer, the coating layer flows excessively beyond the boundary of the selected area where the coating layer is formed. Or, there is an urgent need for research on a method of manufacturing a circuit board in which the coating layer is prevented from being formed so as not to reach the boundary.

Unexamined Patent Publication No. 10-1989-0008604

The present invention has been devised in consideration of the above points, and an object of the present invention is to provide a thin and uniform coating layer that facilitates the manufacturing process and shortens the manufacturing time.

In order to solve the above-described problem, the present invention provides the steps of: (1) preparing a circuit board having electrodes disposed at a predetermined height and width on a support substrate, and (2) an upper portion of one surface of the circuit board exposed to the electrode. In a circuit board manufacturing method comprising: electrospraying a solder resist forming solution to cover the circuit board, and (3) solidifying the electrosprayed solder resist forming solution to prepare a solder resist layer; .

According to an embodiment of the present invention, the solder resist forming solution may include a main resin, a curing agent, and a solvent.

In addition, the solvent may include at least one selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, glycol ethers, esterified products of glycol ethers, and petroleum solvents.

In addition, the solder resist forming solution may have a viscosity of 5 to 100 cP.

In addition, forming a masking layer on a region of the circuit board that is not to be insulated before performing step (2), and removing the masking layer after step (3) may be further performed.

In addition, the masking layer may include an acrylic or silicone adhesive layer.

In addition, the solder resist forming solution may be electrosprayed to a thickness of 5 μm or more before volatilization.

In addition, the solidification may include a drying process performed at a temperature of 40 to 50°C for 3 to 5 minutes, and a curing process performed at 120 to 150°C for 3 to 5 minutes.

In addition, the circuit board may be any one selected from the group consisting of PCB, FPCB, and COF.

In addition, the present invention is a circuit board including a circuit board having electrodes disposed at a predetermined height and width on a support substrate, and a solder resist layer provided to cover at least a part of an exposed surface of the electrode of the circuit board Provides.

According to an embodiment of the present invention, the solder resist layer may have an average thickness of 2 μm to 40 μm.

In the circuit board according to the present invention, when the circuit board is provided with an anti-solder coating, the manufacturing process is very easy and the manufacturing time can be shortened compared to the conventional manufacturing method. In addition, the provided coating can be implemented very thin, and at the same time, the thickness uniformity is very excellent, so the coating quality is excellent. Furthermore, coating errors such as the coating layer flowing beyond the boundary of the selected area where the coating layer is formed, or the coating layer is formed so as not to reach the boundary is minimized or prevented, which is effective in preventing defects in the subsequent SMT process caused by coating errors. Therefore, it is very suitable for improving the reliability and quality of circuit boards.

1 is a schematic diagram of a manufacturing process of a circuit board according to an embodiment of the present invention;
2 is a cross-sectional view of an article implemented in stages in a manufacturing process for implementing a circuit board according to an embodiment of the present invention using a masking film;
3 is an optical photograph of a circuit board according to a comparative example of the present invention, and,
4 is a cross-sectional SEM photograph of a circuit board according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the present invention. The present invention may be implemented in various different forms, and is not limited to the embodiments described herein. In the drawings, parts not related to the description are omitted in order to clearly describe the present invention, and the same reference numerals are added to the same or similar components throughout the specification.

Referring to FIG. 1, the insulating treatment of the circuit board 200 according to an embodiment of the present invention includes (1) preparing a circuit board 200 having electrodes disposed at a predetermined height and width on a support substrate. Steps, (2) electrospraying a solder resist forming solution (20a) so as to cover the circuit board 200 from an upper surface of the circuit board 200 to which the electrodes are exposed, and (3) the electrosprayed solder It may be prepared by solidifying the resist forming solution 20a to prepare the solder resist layer 20.

The step (1) is a step of preparing the circuit board 200. The circuit board may have electrodes disposed on a support substrate with a predetermined height and width, and the electrodes may be disposed on one or both sides. The circuit board 200 may be a circuit board used in a typical electric and electronic field, and for example, may be any one selected from the group consisting of PCB, FPCB, and COF. However, it should be noted that they can be used as the circuit board 200 even when they are integrated into one circuit board.

The circuit board 200 includes a support substrate 210 and an electrode 221 disposed on the support substrate 210. The support substrate 210 may properly adopt a material and structure of a known support substrate of a circuit board, so the present invention is not particularly limited thereto. For example, when the circuit board 200 is a COF, the support substrate 210 may be a polyimide film. The polyimide-based film may have a thickness of 10 to 50 μm, for example. In addition, the electrode 221 may have a material, a height, and a width of an electrode provided on a known circuit board, and the electrode pattern may be appropriately changed according to a circuit design, so the present invention is not particularly limited thereto. The electrode 221 may be copper or copper plated with at least one of tin, nickel, palladium, gold, and silver. In addition, the electrode 221 may have a height of 1 to 20 μm, but is not limited thereto.

On the other hand, when the solder resist layer 20 is selectively provided only in a specific area on the circuit board 200, after preparing the circuit board 200, before performing the electrospray process of step (2) to be described later, the solder resist layer ( The step of masking the area on the circuit board 200 in which 20) will not be formed may be further performed.

Referring to FIG. 2, the masking may be used without limitation in the case of a known masking film, and as an example, as shown in FIG. 2(a), each of the masking layer 50 and the masking layer 50 It may include a protective film 40 and a release film 60 provided.

The masking layer 50 is a layer adhered to or adhered to the circuit board, and is a layer adhered to the circuit board even when steps (2) and (3) described later are performed in a region where the solder resist layer is not formed on the circuit board. to be. The masking layer 50 may be used without limitation in the case of a known masking layer 50 that does not have a physical or chemical effect on the electrode 221 of the circuit board 200 or the support substrate 210. Preferably, it is easy to remove, and it is better not to leave a residue on the circuit board upon removal. Further, more preferably, it is preferable to select one that is not subject to infringement, such as being dissolved by a solvent in the solder resist layer forming solution 20a, during electrospinning in step (2) described later. The masking layer 50 may include an acrylic or silicone adhesive layer, for example.

In addition, the protective film 40 is a layer that serves to protect the masking layer 50 in a punching process, etc., and as shown in FIG. 2(b), a masking film ( After 70) is punched, it may be removed before the masking layer 50' is attached to the circuit board. The protective film 40 may have a material and thickness that can protect the masking layer 50 even when an external force such as a punching process is applied, and heat resistance such as PET, PI, PC, PAN, PES, etc. It may be a film, and the thickness may be appropriately adjusted in consideration of the material of the protective film and the degree of external force applied during the punching process.

In addition, the release film 60 supports the masking layer 50 to facilitate transfer and attaching to the circuit board, and can be used without limitation if it is a material that can be easily removed from the masking layer 50. And, for example, it may be a PET film. In addition, the antistatic treatment may be performed on one surface to be easily removed, but is not limited thereto. In addition, the thickness of the release film 60 can be appropriately adjusted in consideration of the ease of operation and support, the present invention is not particularly limited thereto.

Referring to FIG. 2, a process of forming the masking layer 50 ′ on the circuit board 200 will be described. The masking film 70 prepared as shown in FIG. 2A is used in the area where the solder resist layer is not formed on the circuit board. By performing a punching process in shape, a punched masking film 70 ′ as shown in FIG. 2B may be manufactured. Thereafter, as shown in FIG. 5C, with the protective film 40 removed, the masking layer 50 ′ of the masking film 70 ′ may be attached so as to correspond to a region in which the solder resist layer is not formed on the circuit board. Thereafter, the release film 60 is removed from the masking film 70 ″ attached on the circuit board 200 to prepare a circuit board in which a selected area of the circuit board 200 is masked as shown in FIG. 5D.

Next, the step (2) is a step of electrospraying a solder resist forming solution 20a so as to cover the circuit board 200 from an upper surface of the prepared circuit board 200 to which the electrodes are exposed.

The electrospray can be performed through a conventional electrospray device 3. The solder resist forming solution 20a electrosprayed onto the carrier film 10 may include a main resin, a curing agent, and a solvent. The main resin may be used without limitation if it is a known material known to form a solder resist. For example, it may be an epoxy resin, a phenol resin, an unsaturated polyester resin, an alkyd resin, a melamine resin, a urethane resin, or an acrylic resin. Not limited.

In addition, the curing agent may be used by appropriately selecting a known curing agent in consideration of the selected main resin and functional groups provided in the main resin. For example, imidazoles, guanamines such as benzoguanamine or acetoguanamine, diamino Polyamines such as diphenylmethane, dashiandiamide and melamine, triazine derivatives such as ethyldiamino-S-triazine, trimethylamine, triethanolamine, N,N-dimethyloctylamine, N-benzyldimethylamine, pyridine , N-methylmorpholine, hexa (n-methyl) melamine, 2,4,6-tris (dimethylaminophenol), tetramethylguanidine, amines such as m-aminophenol, polyvinylphenol, polyvinylphenol bromide, Polyphenols such as phenol novolak and alkylphenol novolak, organic phosphines such as tributylphosphine, triphenylphosphine, and tris-2-cyanoethylphosphine may be used in combination of one or two or more. It is not limited thereto. The curing agent is preferably included in an amount of 1 to 25 parts by weight based on 100 parts by weight of the main resin, but is not limited thereto.

In addition, the solvent may be a known solvent suitable for dissolving and reacting the above-described main resin and the curing agent, for example, aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, glycol ethers, esterified products of glycol ethers and petroleum It may include at least one selected from the group consisting of solvents. Specifically, the aliphatic hydrocarbons may include at least one selected from the group consisting of ethyl acetate, hexane, octane, and decane. In addition, the aromatic hydrocarbons may include at least one selected from the group consisting of ethyl benzene, propyl benzene, toluene, and xylene. In addition, the alcohols may include at least one selected from the group consisting of ethanol, propanol, isopropanol, butanol, 2-methoxy propanol, and hexanol. In addition, the glycol ethers may include at least one selected from the group consisting of diethylene glycol mono ethyl ether, diethylene glycol mono methyl ether, and dipropylene glycol mono methyl ether. In addition, the esterified product of the glycol ether may be diethylene glycol monoethyl ether acetate as an example. In addition, the petroleum-based solvent may include one or more ketones such as acetone and methyl ethyl ketone, solvent naphtha, petroleum naphtha, and the like. These may be used alone or in combination of two or more.

However, if the volatilization of the solvent on the circuit board 200 is delayed after electrospraying, thickness variation due to flowability may occur and smoothness may be impaired. In addition, the masking layer may be partially dissolved by a solvent, and due to this, the masking layer residue may remain on the circuit board even after the masking layer is removed. There is a concern that a layer may be formed by invading a region where a layer should not be formed, or a tolerance may occur at the boundary of the solder resist layer. Furthermore, there may be a concern that productivity and manufacturing cost increase due to prolonged drying time. Accordingly, the solvent is preferably a solvent having high volatility at room temperature, for example, 25°C, and ethyl acetate may be used as an example.

In addition, the solder resist forming solution 20a may further contain additives in addition to the above-described main resin, curing agent, and solvent. As the additive, a silicone powder which is advantageous for improving adhesion, matteness, and electrical insulation may be included. Further, as additives, inorganic fillers such as barium sulfate, talc, calcium carbonate, alumina, glass powder, quartz powder, and silica; Fiber reinforcing materials such as glass fiber, carbon fiber, and boron nitride fiber; Coloring agents such as titanium oxide, zinc oxide, carbon black, iron black, organic pigments and organic dyes; Antioxidants such as hindered phenol compounds, phosphorus compounds, and hindered amine compounds; Ultraviolet absorbers such as benzotriazole-based compounds and benzophenone-based compounds can also be blended. Further, depending on the application, a viscosity modifier, a flame retardant, an antibacterial agent, a flame retardant, an anti-aging agent, an antistatic agent, a plasticizer, a lubricant, a foaming agent, and the like may be blended.

In addition, the solder resist forming solution (20a) may have a viscosity of 5 to 100 cP, and through this, a solder resist layer having a uniform thickness, thin but no masking layer residue on the circuit board, and excellent surface roughness is formed. It may be more advantageous to form. If the viscosity of the solder resist forming solution 20a is less than 5 cps, there is a fear of generation of residues due to dissolution of the masking layer described later. In addition, since it is not easy to control flowability, it may be formed by invading an undesired area through an electrode through capillary phenomenon or the like. In addition, if the viscosity exceeds 100cp, electrospraying is difficult and a solder resist layer with pores may be implemented, and the size of the particles sprayed due to uneven ejection from the nozzle during electrospraying is different, so that the thickness variation of the solder resist layer is May occur, and the drying time may be prolonged.

The above-described solder resist forming solution 20a is electrosprayed through the spray nozzle of the electrospray device 3, and the electrospray device 3 may use a conventional electrospray device. At this time, the voltage applied to the injection nozzle may be 10 to 50 kV, and the air gap between the injection nozzle and the circuit board 200 may be 10 to 30 cm, but is not limited thereto. In addition, the electrospray device 3 may further include an air nozzle provided adjacent to the spray nozzle, and when the solder resist forming solution 20a is electrosprayed, air is sprayed together through the air nozzle. Air injection method can also be used.

On the other hand, when the spraying amount of the solder resist forming solution (20a) is excessive, for example, when the spraying amount of the solder resist forming solution (20a) is 20 μm/min or more and/or electric spraying with a thickness of 5 μm or more before volatilization, flowability A solder resist layer having an uneven thickness may be formed due to difficulty in control. In addition, the masking layer is dissolved by the solvent contained in the forming solution sprayed in an excessive amount, and thus the residue of the masking layer may remain on the circuit board (see FIG. 3). Alternatively, when the spraying amount of the solder resist forming solution 20a is too small, tearing of the implemented solder resist layer may occur during the process of removing the masking layer at the boundary of the selective region where the solder resist layer is provided. In this case, there is a concern that an error may significantly increase between the boundary line of the target area in which the solder resist layer is to be provided and the boundary line of the actually implemented solder resist layer.

Next, as step (3), a step of preparing the solder resist layer 20 by solidifying the electrosprayed solder resist forming solution 20a is performed.

The electrosprayed solder resist forming solution 20a may be solidified and implemented as a solder resist layer 20, where the solidification may be drying and/or curing. That is, when the final solder resist layer 20 is formed only by drying, the solidification means drying, and when the solder resist layer 20 is a composition requiring curing, the solidification means drying and curing.

On the other hand, when the electrosprayed solder resist forming solution 20a has strong volatilization properties of the solvent in the solution, it may be naturally dried while being electrosprayed while contacting the circuit board 200 in air or before reaching the circuit board 200. In this case, if the solder resist forming solution 20a has a composition in which the solder resist layer 20 can be formed only by drying, the solder resist layer 20 may be formed through natural drying after electrospraying without a separate drying device. Alternatively, even if the solder resist forming solution 20a is formed as the solder resist layer 20 only by drying, if the amount of the sprayed solder resist forming solution 20a is large or the volatilization property of the used solvent is weak, after electrospraying In addition to drying through natural drying, the solder resist layer 20 may be formed through drying through an additional predetermined drying device. The drying device may be a conventional drying device capable of applying a predetermined heat, and for example, may be a hot air drying device and/or a drying device using electromagnetic waves (for example, an infrared drying device). Meanwhile, when passing through a separate drying device, drying conditions in the drying device may be performed at a temperature of 40 to 50° C. for 3 to 5 minutes, but may be appropriately changed in consideration of the thickness of the solder resist layer 20.

Alternatively, when the solder resist forming solution 20a is embodied as the solder resist layer 20 through curing, even if drying is performed through the above-described natural drying, curing may be performed through a separate heating device afterwards. For example, the curing process may be performed at 120 to 150° C. for 3 to 5 minutes, additionally, the heat treatment and the pressing process may be performed simultaneously, and the pressure applied during the pressing process may be 0.5 to 3.0 MPa. However, the temperature, time, and pressure to be heat-treated during curing may be appropriately changed in consideration of the material and thickness of the solder resist layer 20.

On the other hand, in the embodiment in which the solder resist layer 20 is selectively provided only in a partial area on the circuit board 200, the above-described step (3) is performed on the circuit board 200 as shown in FIG. 2(e). After the solder resist layer 20 is implemented, a process of removing the masking layer 50 ′ may be further performed.

The removal of the masking layer 50 ′ may be performed through a film (for example, tapes) having higher adhesion than the adhesion (or adhesion) of the masking layer, but is not limited thereto, and the material of the masking layer 50 ′ Therefore, it can be appropriately selected.

The circuit board implemented by the above-described manufacturing method includes a circuit board 200 having an electrode 221 disposed on a support base 210 with a predetermined height and width, and the electrode 221 of the circuit board 200 Includes a solder resist layer 20 provided to cover at least a portion of the exposed surface of the circuit board 1000 ′, as shown in FIG. A layer 20 may be provided.

In addition, the solder resist layer 20 may have an average thickness of 2 µm to 40 µm, and when it has a predetermined average thickness, the thickness variation by location is 5% or less, more preferably 3% or less. It may be implemented as a layer of. The improved thickness uniformity of the solder resist layer 20 is advantageous in that a constant heat and pressure can be applied to the solder resist layer 20 as a whole, thereby improving the bonding state with the circuit board.

Although an embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in the present specification, and those skilled in the art who understand the spirit of the present invention can add components within the scope of the same idea. It will be possible to easily propose other embodiments by changing, deleting, adding, etc., but it will be said that this is also within the scope of the present invention.

3: electrospray device 20: solder resist layer
70: masking film 200: circuit board
1000': circuit board

Claims (11)

(1) preparing a circuit board having electrodes disposed at a predetermined height and width on a support substrate;
(2) electrospraying a solder resist forming solution so as to cover the circuit board from an upper surface of the circuit board to which the electrode is exposed; And
(3) preparing a solder resist layer by solidifying the electrosprayed solder resist forming solution. The method of claim 1,
The solder resist forming solution comprises a base resin, a curing agent, and a solvent. The method of claim 2,
The solvent is a circuit board manufacturing method, characterized in that it contains at least one selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, glycol ethers, esterified products of glycol ethers, and petroleum solvents. The method of claim 1,
The method of manufacturing a circuit board, wherein the solder resist forming solution has a viscosity of 5 to 100 cP. The method of claim 1,
Forming a masking layer in a region not to be insulated on the circuit board before performing the (2) step,
After the step (3), the step of removing the masking layer is further performed. The method of claim 5,
The method of manufacturing a circuit board, wherein the masking layer comprises an acrylic or silicone adhesive layer. The method of claim 5,
The method for manufacturing a circuit board, wherein the solder resist forming solution is electrosprayed to a thickness of 5 μm or more before volatilization. The method of claim 1,
The solidification is a method of manufacturing a circuit board, characterized in that it includes a drying process performed at a temperature of 40 to 50°C for 3 to 5 minutes, and a curing process performed at 120 to 150°C for 3 to 5 minutes. The method of claim 1,
The circuit board manufacturing method, characterized in that any one selected from the group consisting of PCB, FPCB and COF. A circuit board having electrodes disposed at a predetermined height and width on the support substrate; And
And a solder resist layer provided to cover at least a portion of the exposed surface of the electrode of the circuit board. The method of claim 10,
A circuit board, wherein the solder resist layer has an average thickness of 2 μm to 40 μm.

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