KR100566912B1 - Method of manufacturing flexible printed circuit board with partial copper plating - Google Patents

Abstract

The present invention relates to a method for manufacturing a flexible printed circuit board made of partial copper plating. In manufacturing a double-sided or multi-layered FPCB, the entire thickness of the FPCB circuit board is made thin by allowing the electric copper plating to be partially made only at the through hole. This is to improve the flexibility of the substrate.

In the manufacturing method of the present invention for realizing this, the step (ST 3) of performing electrocopper plating on the substrate surface on which the electroless plating is made, laminating the dry film on both sides of the substrate on which the electroless plating layer is formed (ST 3-3). One); Performing ultraviolet exposure on a portion of the dry film except for the through hole (ST 3-2); Developing to remove the dry film of the unexposed portion (ST 3-3); A copper plating forming step (ST 3-4) for forming an electric copper plating layer in a portion of the through hole from which the dry film is removed; Characterized in that the dry film peeling step (ST 3-5) to remove the dry film remaining on the substrate surface.

Copper plating, Flexible printed board, Manufacturing, FPCB, Flexibility

Description

A method of manufacturing flexible printed circuit boards with partial copper plating {A MANUFACTURE METHOD OF FLEXIBLE PRINTED CIRCUIT BOARD}

1 is a flow chart of a conventional panel plating method FPCB manufacturing process.

Figure 2 is a flow chart of the FPCB manufacturing process for partial copper plating according to the present invention.

Figure 3 is a cross-sectional state diagram for each manufacturing process of the present invention.

4 is a cross-sectional structural view of the completed double-sided FPCB is shown,

4a is a schematic diagram of a printed circuit board manufactured according to a conventional method.

4b is a schematic diagram of a printed circuit board manufactured according to the method of the present invention.

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

11: copper foil laminated plate (polyimide film) 11a: copper foil layer

12: through hole 13: electroless plating layer

14: electroplated copper layer 15: dry film

16: mask film

The present invention relates to a method of manufacturing a flexible printed circuit board, and more particularly, to manufacturing a double-sided or multi-layer flexible printed circuit board, the thickness of the circuit becomes thick due to the plating of the panel, and thus the partial copper plating for preventing the lowering of the flexibility of the substrate. It relates to a substrate manufacturing method which is made.

In general, with the development of electronic components and component embedding technology, multilayer printed circuit boards that overlap circuit conductors have been continuously developed.

Recently, in the field of electronics industry, the rapid development of integrated density of semiconductor integrated circuits and the surface mount technology for directly mounting small chip components have been developed and the electronic equipments have been miniaturized. Therefore, it is necessary to facilitate the installation in more complicated and narrow spaces. In order to meet these demands, double-sided exposure type and flexible multilayer printed circuit boards have been developed.

In particular, in the case of flexible printed circuit boards (FPCBs) with easy-to-laminate and high-use double-sided exposure structures, the use of cellular batteries, printer heads, LCDs, and PDPs has increased dramatically due to technological developments. However, the demand is increasing.

In general, the manufacturing process of the flexible printed circuit board (FPCB), in particular, double-sided exposure type (DOUBLE ACCESS) type by CNC hole processing of the raw material of the copper foil to set the position and thermocompression bonding one side of the copper foil with a coverlay Bonding through the film to form a circuit through a process such as dry film laminating, exposure, development.

That is, the manufacturing process of the conventional FPCB through the flow chart of Fig. 1, first, the laminated copper foil layer 1 of the cut-out of the copper foil layer (1a) on the upper and lower surfaces (typically 35㎛ copper foil of 35㎛ on 25㎛ polyimide film The through-hole for the electrical connection is formed by using a through-drill, and the electroless copper plating 3 is applied to the entire surface of the copper-clad laminate to a thickness of 0.5 μm, and the formed electroless copper plating layer ( 3) The electrocopper plating is again performed to a thickness of 10 μm so that the electrocopper plating layer 4 is formed over the entire surface of the substrate including the through hole 2.

Then, after performing the front (substrate cleaning) process, the dry film is laminated, and the circuit is formed on both sides of the substrate by performing exposure process using ultraviolet light (UV light), developing process using a developing solution, and etching process using an etching solution. Finally, the flexible printed circuit board is completed by undergoing a peeling process of the dry film remaining on the substrate surface.

However, in the case of the conventional FPCB manufactured by such a process, as shown in FIG. 4A, the electroplated copper layer 4 remains as a layer having a predetermined thickness on the entire circuit forming site as well as the periphery of the through hole 2. The thickness of the copper-clad laminate (1) was a cause of increasing, and this causes a problem such that the circuit is easily broken due to the deterioration of flexibility when applied to devices that require more than tens of thousands of bendability, such as a mobile phone.

The present invention has been proposed to improve the above-described problems in the prior art, and provides a manufacturing method to allow copper plating to be made only partially around the through-holes that are formed by forming through holes in necessary portions in the manufacturing process of the FPCB. The purpose is to improve the flexibility of the circuit board.

The object is, in the process of performing the electroplating, laminating a dry film on both sides of the substrate on which the electroless plating layer is formed; Performing ultraviolet exposure on a portion of the dry film except for the through hole; Developing to remove the dry film of the unexposed portion; A copper plating forming step for forming an electric copper plating layer in the through hole portion from which the dry film is removed; A dry film peeling step of removing the dry film remaining on the substrate surface; It can be achieved through a flexible printed circuit board manufacturing method is made of a partial copper plating, characterized in that consisting of.

Hereinafter, a specific embodiment to which the manufacturing method of the present invention is applied will be described with reference to FIG. 3, which shows a flowchart of a double-sided FPCB manufacturing process of FIG. 2 and a substrate cross-sectional structure in each process.

First, a copper foil layer 11a is formed on both sides of the polyimide film, and thus, the copper foil laminated plate 11 forming the substrate body is subjected to a cutting process in which cutting is performed in a predetermined shape when supplied in a roll state.

Then, the hole forming process (ST 1) of forming the through-hole 12 by using a through-drill in advance is performed in a portion of the copper foil laminated plate 11 is made of the cutting is required for the conduction between both sides of the circuit formation.

Thereafter, an electroless plating process (ST 2) of forming an electroless plating layer 13 having a thickness of approximately 0.5 μm on both surfaces of the copper clad laminate 11 is performed. The electroless plating layer 13 may selectively execute a shadow made of copper plating or graphite.

On the other hand, in the process (ST 3) for forming a partial electric copper plating layer in the conductive hole 12, the step of laminating the dry film 15 of the thin film on both sides (ST 3-1), and the substrate surface An exposure step of curing an exposed film part by performing ultraviolet (UV light) exposure while covering a portion of the through hole 12 of the dry film 15 laminated on the mask film 16 (ST 3-3). 2) and a developing step (ST 3-3) to remove the dry film around the through-holes 12 which are not cured in the exposure step by developing using a developing solution, and electricity to the entire surface of the substrate. A copper plating layer forming step (ST 3-4) in which copper plating is performed so that the electric copper plating layer 14 may be formed only at a portion around the through hole 12 where the dry film is partially removed, and a circuit on both sides of the substrate is formed. Left to prevent plating Since the dry film peeling step (ST 3-5) to remove the dun dry film 15 is sequentially performed, the partial electrocopper plating layer 14 may be formed.

In particular, in the step (ST 3-4) of performing the electro-copper plating in the above process, only the periphery of the conductive hole 12, the electroless plating layer 13 is exposed, the electro-copper plating layer 14 is formed by electrical conduction, etc. Since the part is insulated by the dry film 15, it can be seen that the electric copper plating cannot be formed.

Through the above process, the substrate on which the partial electrocopper plating layer 14 of the present invention is formed is completed by performing a conventional post-process for forming a circuit on both sides of the flexible printed circuit board.

That is, in the post process for circuit formation, washing is performed through the front surface process (ST 4), laminating a new dry film on the cleaned substrate surface (ST 5), and UV exposure process for the circuit area (ST 6). And a known circuit forming process through the developing process (ST 7) for removing the non-exposed part and the etching process (ST 8) and film peeling process (ST 9) for removing the copper foil layer 11a of the non-circuit part. Through the flexible printed circuit board (FPCB) is formed on the substrate surface is completed.

The FPCB of the present invention made as described above is partially formed only in the portion of the conductive hole 12 where the electrical copper plating layer 14 requires conduction, as shown in the completed cross-sectional view of FIG. It can be seen that.

Therefore, as shown in FIG. 4A, the present invention provides a method for printing printed circuit boards, in which the electroplated layer 4 remains at a predetermined thickness (about 10 mu m) even in the circuit formation portion, compared to the conventional substrate, which caused the deterioration in flexibility. It can be seen that the thickness can be relatively thin.

In addition, although specific embodiments of the present invention have been described and illustrated above, it is obvious that the method of manufacturing the flexible printed circuit board of the present invention may be variously modified and implemented by those skilled in the art.

For example, in the above embodiment, a description has been made and illustrated using a double-sided FPCB manufacturing process as an example, but this partial copper plating technique may be applied to a multi-layered FPCB manufacturing process.

Therefore, such modified embodiments should not be understood individually from the technical spirit or the prospect of the present invention, and such modified embodiments should fall within the appended claims of the present invention.

According to the method of manufacturing a flexible printed circuit board of the present invention as described above, in the process of manufacturing a double-sided or multi-layered printed circuit board, the electric copper plating may be partially made only in the through-hole of the board, thereby the overall circuit board of the FPCB. The thickness can be made thin, and thus the flexibility of the substrate can be improved.

In particular, by improving the flexibility of the flexible printed circuit board, there is an advantage in that the conventional problem due to the broken circuit is solved, thereby improving durability and reliability of the product.

Claims (1)

Forming a through hole using a through-drill in the copper-clad laminate to be the substrate body (ST 1), the process of electroless plating on both sides of the copper-clad laminate (ST 2), and the electroless plating The process of performing electrocopper plating on the substrate surface (ST 3), the front process of washing the substrate surface on which the electrocopper plating is performed (ST 4), and laminating the dry film to form a circuit on the cleaned substrate surface (ST 5) In the manufacturing process of the flexible printed circuit board to perform the exposure (ST 6), development (ST 7), etching (ST 8), film peeling process (ST 9) sequentially: The electroplating process (ST 3) may include laminating dry films on both sides of the substrate on which the electroless plating layer is formed in a state in which a circuit is not formed on the substrate surface (ST 3-1); Performing ultraviolet exposure and development on the remaining portion of the substrate except for the through hole of the dry film (ST 3-2, ST 3-3); A copper plating forming step (ST 3-4) for forming an electroplated copper layer partially around the through hole from which the dry film is removed; Dry film peeling step (ST 3-5) for removing the dry film remaining on the substrate surface after forming the copper plating layer; a flexible copper substrate manufacturing method of the partial copper plating is made through.

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