KR100651335B1 - Rigid-flexible Print circuit board and method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a flexible printed circuit board and a method for manufacturing the same. More specifically, by not using a polyimide copper clad laminate in manufacturing a flexible printed circuit board, the cost burden and dissimilar materials The present invention relates to a flexible printed circuit board and a method for manufacturing the same, which improve the difficulty of interfacial adhesion reliability.

Rigid, Flexible, Polyimide, Prepreg, Bonding Sheets, Coverlays

Description

Rigid-flexible printed circuit board and method for manufacturing thereof

1A to 1I are cross-sectional views showing the flow of a method for manufacturing a flexible substrate according to the prior art.

2A to 2R are views for explaining a method of manufacturing a flexible substrate according to a first embodiment of the present invention.

3A to 3K are views for explaining a method of manufacturing a flexible substrate according to a second embodiment of the present invention.

4A to 4R are views for explaining a method of manufacturing a flexible substrate according to a third embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

200, 300, 400: circuit layers 201, 301, 401: first prepreg

202, 302, 403: Copper foil layer 202-1, 302-1, 404-1: Internal circuit pattern

203b, 303b, 402b: first coverlay 203a, 303a, 402a: second coverlay

204, 404, 214: dry film 205, 310, 410: second prepreg

207: first inner layer 208: second inner layer

209, 321, 421: third prepreg 210b, 323b, 406b: third coverlay

210a, 323a, 406a: fourth coverlay 211: insulating substrate

212, 322, 423: copper foil layer 213, 331, 424: copper plating layer

213-1, 331-1, 424-1: outer layer circuit patterns 210, 330, 420: outer layer

C, D, H, I, J, M, O, P: Window N: Internal via hole

F, K, Q: Through Hole G, L, R: Blind Via Hole

The present invention relates to a flexible printed circuit board and a method of manufacturing the same, and more particularly, to improve the difficulty of the cost burden and the interfacial adhesion reliability due to the dissimilar materials when the flexible printed circuit board is manufactured. The present invention relates to a flexible printed circuit board that does not use a polyimide copper clad laminate, and a method of manufacturing the same.

Recently, printed circuit boards that are employed as the electronic device has become smaller, lighter, and thinner have also been required to be lighter, thinner and denser. Therefore, the adoption of multilayer flexible printed circuit boards to meet such demands is rapidly expanding. However, the manufacturing process of the multilayer flexible printed circuit board is more expensive and has a higher defect rate than the conventional rigid printed circuit board because of the complexity and the number of processes. Particularly, among the multilayer flexible printed circuit boards, a product called a flexible printed circuit board, which is a structure in which a part of the board is flexible, has been adopted in a recent clamshell mobile phone and is expected to grow rapidly. Such flexible areas of flexible printed circuit boards make it difficult to work in the manufacturing process and increase the defective rate. To solve these problems, it is possible to differentiate from other companies by developing special materials and establishing methods using them. The basic requirement for flexible printed circuit boards is the ability to form fine circuits with thin and durable materials. In other words, material selection and manufacturing method selection are important points. The material has been used as the main material because there is no substitute for polyimide resin in heat resistance, mechanical strength, flame retardancy, and electrical properties. However, in recent years, materials are being replaced to replace them in terms of high frequency response, moisture resistance, numerical stability, and cost.

In addition, as miniaturization and integration of electronic components have been developed, various multilayer circuit boards that can be mounted on the surface have been developed. Among them, rigid-flexible printed circuit boards capable of minimizing the space occupied by the board and enabling 3D change are possible. Active research on the Multi-Layer Printed Circuit Board, hereinafter referred to as a flexible printed circuit board) is being conducted.

A flexible printed circuit board can combine multiple boards into one printed circuit board without a separate connector or cable between boards, which has the advantage of reducing the delay or distortion of an electrical signal and reducing the mounting volume. Therefore, it is considered as a static & dynamic application that allows one bend and an application of several hundred thousand cycles. However, the use of polyimide copper clad laminate material, which is an expensive flexible material, costs 3 to 4 times more than a flexible printed circuit board based on a general flexible substrate. In addition, the weak interfacial adhesion between prepreg (or bonding sheet) and polyimide, which is used as an interlayer adhesive layer for the multilayer implementation of a rigid part, has been pointed out as a difficulty in securing a substrate and securing long-term reliability. In particular, as the price of printed circuit boards has recently declined, the cost burden on polyimide materials is increasing, and some companies are increasing the adoption of connectors or cables, which are con to con connection methods. Considering the tendency of a small electronic product, manufacture of a low cost flexible printed circuit board by a new construction method is required.

1A to 1I are cross-sectional views showing the flow of a conventional method for manufacturing a flexible substrate.

As shown in Fig. 1A, a prepreg 101 having a window A processed at a predetermined position is prepared.

As shown in FIG. 1B, polyimide copper clad laminates including polyimide films 102a and 102b and copper foil layers 103a and 103b are laminated on both surfaces of the prepreg 101.

As shown in FIG. 1C, dry films 104a and 104b or photosensitive materials in a liquid state are coated on both surfaces of the copper foil layers 103a and 103b, respectively.

As shown in Fig. 1D, the artwork film having a predetermined pattern printed thereon is brought into close contact with the dry films 104a and 104b, and then a predetermined etching resist pattern is formed through an exposure and development process. Further, by using the dry films 104a and 104b as etching resists and immersing them in the etching liquid, the copper foil layers 103a and 103b of the remaining portions except for the portions corresponding to the predetermined patterns of the dry films 104a and 104b are removed. do.

As shown in FIG. 1E, the applied dry films 104a and 104b are removed using a stripping solution to form predetermined circuit patterns 103a and 103b.

As shown in FIG. 1F, the coverlays 105a and 105b are applied to both surfaces of the circuit patterns 103a and 103b corresponding to the window A at a predetermined position, and then presses are applied.

As shown in FIG. 1G, the prepregs 106a and 106b prepared in FIG. 1A are stacked on the circuit patterns 103a and 103b so that a part of the coverlays 105a and 105b are exposed.

As shown in FIG. 1H, the polyimide copper-clad laminate composed of the polyimide films 107a and 107b and the copper foil layers 108a and 108b is again laminated on both surfaces of the prepregs 106a and 106b laminated at the outermost side, and then photographed. Through the etching process, predetermined circuit patterns 108a and 108b are formed.

As shown in FIG. 1I, after performing the step of FIG. 1H once more and finally applying the coverlays 113a and 113b to both sides of the outermost circuit patterns 108a and 108b corresponding to the window A at a predetermined position. Press to complete the flexible printed circuit board.

U. S. Patent No. 6,745, 463 discloses a method for manufacturing a flexible printed circuit board associated therewith.

However, the printed circuit board according to the conventional method is composed of a polyimide copper clad laminate and a prepreg of the heterogeneous material to form a rigid region, the adhesion characteristics are inferior. In order to solve this problem, the polyimide copper clad laminate had a problem of performing surface treatment through plasma (or corona) treatment or mechanical brushing.

In addition, in the conventional printed circuit board, the coverlay is laminated on a polyimide copper clad laminate (Polyimide CCL) on which a circuit pattern is formed. The circuit pattern curled to the side, causing a bad mountability in the surface mount device, thereby increasing the defect rate.

In addition, the unit cost of the polyimide copper clad laminate requires a higher cost than the prepreg, and thus there is a problem in that a low-cost flexible copper clad laminate cannot be formed.

The technical problem of the present invention for solving the above problems is a flexible printed circuit board and a method of manufacturing the adhesive reliability is good, the bending characteristics can be implemented, there is no opening of the bent portion, and inexpensive polyimide copper clad laminate To provide.

In order to solve the above technical problem, a method of manufacturing a flexible printed circuit board according to an embodiment of the present invention (A) of the first insulating layer formed with the first window, the first insulating layer including the first window Preparing a circuit layer including an internal circuit pattern formed on one surface, first and second protective films protecting the internal circuit pattern formed on the first window, and (B) a second corresponding to the first window. Preparing a second insulating layer in which a window is formed, (C) stacking a plurality of circuit layers and a second insulating layer to form a laminate, and (D) an external circuit pattern corresponding to an internal circuit pattern And forming upper and lower layers of an outer layer formed on the third window corresponding to the second window and protected by the third and fourth protective films, respectively, corresponding to the first, second and third windows. The area is characterized in that the flexible area.

In the method of manufacturing a flexible printed circuit board according to an embodiment of the present invention, in step (A), (A-1) providing a first insulating layer having a first window formed therein, (A-2) first Applying a first protective film to include a first window on one surface of the insulating layer, (A-3) laminating a copper foil layer on the other side of the first insulating layer, and (A-4) the inside of the copper foil layer It is preferable to include forming a circuit pattern, and (A-5) applying the 2nd protective film which protects the internal circuit pattern formed on the 1st window with a 1st protective film.

In the method of manufacturing a flexible printed circuit board according to an embodiment of the present invention, the step (A) includes (A-1) applying a first protective film having a predetermined size to one surface of the copper foil layer, (A-2 ) Laminating a first insulating layer having a first window having a smaller size than the first protective film on one surface of the copper foil layer so that a part of the first protective film is exposed, (A-3) forming an internal circuit pattern on the copper foil layer. And forming a second protective film corresponding to the first protective film and protecting the internal circuit pattern on the internal circuit pattern (A-4).

In the method of manufacturing a flexible printed circuit board according to an embodiment of the present invention, the first insulating layer and the second insulating layer are preferably prepregs or bonding sheets.
In the method of manufacturing a flexible printed circuit board according to an embodiment of the present invention, the first, second, third and fourth protective films may include a coverlay of a general film type, a coverlay of a liquid type, or a cover of a dry film type. It is characterized by being a ray.

In the method of manufacturing a flexible printed circuit board according to an embodiment of the present invention, step (D) may include: (D-1) a third window having a third window having the same size and position as the first window and the second window; Stacking a preliminary outer layer including an insulating layer, a copper foil layer formed on one surface of the third insulating layer, and a third protective film formed on the third insulating layer to include a third window, above and below the laminate, (D-2) Forming an external circuit pattern including a plurality of via holes on the copper foil layer, and (D-3) applying a fourth protective film for sealing the third window together with the third protective film and protecting the external circuit pattern. It is preferred to include the step of forming an outer layer.

In the method of manufacturing a flexible printed circuit board according to an embodiment of the present invention, the plurality of via holes in step (D-2) preferably include through holes and blind via holes.

A flexible printed circuit board according to an embodiment of the present invention is characterized by being manufactured by the above-described method.

In order to solve the above technical problem, a method of manufacturing a flexible printed circuit board according to another embodiment of the present invention, (A) the first and second electrically connected to both sides of the first insulating layer on which the first window is formed Internal circuit patterns are formed, and first, second, third and fourth protective films corresponding to the first window and protecting the first and second internal circuit patterns on the first window are coated on both surfaces of the first insulating layer. Preparing a circuit layer, (B) preparing a second insulating layer on which a second window corresponding to the first window is formed, and (C) stacking a plurality of circuit layers and a second insulating layer to form a laminate. And (D) an outer circuit pattern corresponding to the first and second inner circuit patterns is formed on the third window corresponding to the first and second windows and protected by the fifth and sixth protective films. Forming the upper and lower portions of the laminate, wherein the first, second and third winches Characterized in that the Yiwu area corresponding to the flexible area.

In the method of manufacturing a flexible printed circuit board according to another embodiment of the present invention, step (A) includes (A-1) providing a first insulating layer having a first window, and (A-2) first insulating Applying a first protective film and a second protective film to the upper and lower surfaces of the layer, (A-3) a copper foil layer on the upper and lower surfaces of the first insulating layer to which the first protective film and the second protective film are applied. Laminating, (A-4) forming internal via holes on the copper foil layer and performing electroless plating and electrolytic copper plating, and (A-5) forming first and second internal circuit patterns on the copper foil layer (A-6) It is preferable to include applying a third protective film and a fourth protective film to protect the first and second internal circuit patterns on the first protective film and the second protective film.

In the method of manufacturing a flexible printed circuit board according to another embodiment of the present invention, the first insulating layer and the second insulating layer are preferably prepregs or bonding sheets.
In the method of manufacturing a flexible printed circuit board according to another embodiment of the present invention, the first, second, third, fourth, fifth, and sixth protective films may include a coverlay of a general film type and a coverlay of a liquid type. Or a dry film type coverlay.

In the method of manufacturing a flexible printed circuit board according to another embodiment of the present invention, the step (D) may include (D-1) a third insulation having a third window having the same size and position as the first window and the second window. Stacking a preliminary outer layer including a layer, a copper foil layer formed on one surface of the third insulating layer, and a fifth protective film formed on the third insulating layer to include a third window, (D-2) copper foil Forming an external circuit pattern including a plurality of via holes on the layer, and (D-3) embedding a third window together with the fifth protective film and applying a sixth protective film for protecting the external circuit pattern to form an outer layer. It is preferred to include the step of forming.

In the method of manufacturing a flexible printed circuit board according to another embodiment of the present invention, the plurality of via holes in step (D-2) preferably include through holes and blind via holes.

A flexible printed circuit board according to another embodiment of the present invention is characterized by being manufactured by the above-described method.

Hereinafter, a flexible printed circuit board and a method of manufacturing the same according to the present invention will be described in detail without using a polyimide copper-clad laminate with reference to the drawings.

2 and 3 are process diagrams illustrating a method of manufacturing a six-layer flexible printed circuit board by stacking single side surfaces.

First, FIGS. 2A to 2R are diagrams for describing a method of manufacturing a flexible substrate according to a first embodiment of the present invention.

As shown in FIG. 2A, the window C is machined inside the first prepreg 201. The window C can be formed using a punch, a drill bit, or the like in the first prepreg 201. The window C is a part to be a flexible area after the completion of the product.

In FIG. 2B, the copper foil 202 is apply | coated to the upper surface of the 1st prepreg 201, and it presses after apply | coating a protective film like the 1st coverlay 203b so that the lower surface may include the window C. In FIG. When the copper foil 202 is applied and pressed, the copper foil of the portion corresponding to the window C is pushed into the window C as shown in FIG. 2B to be in close contact with the adhesive of the first coverlay 203b. It becomes possible. The first coverlay 203b serves as a support layer for protecting the circuit pattern of the copper foil 202 formed in the window portion of the first prepreg 201, and also in the flexible printed circuit board according to the first embodiment of the present invention. It can provide a continuous bend of.

Meanwhile, as shown in FIG. 2B, the first coverlay 203b may be partially coated to cover only the portion of the window C of the first prepreg 201, and may cover the entire first prepreg 201. It can also be applied to the front.

Here, the said process may use the batch lamination method which presses the 1st prepreg 201, the copper foil 202, and the 1st coverlay 203b collectively at once.

Thereafter, as shown in FIG. 2C, the dry film 204 is coated on the copper foil 202. At this time, a liquid photosensitive material may be used instead of the dry film 204.

As shown in FIG. 2D, the artwork film having a predetermined pattern printed thereon is brought into close contact with the dry film 204, and then a predetermined etching resist pattern is formed through an exposure and development process. When the substrate is immersed in the etchant, the dry film 204 or the liquid photosensitive material serves as an etching resist, and the copper foil 202 of the remaining portion except for the portion corresponding to the predetermined pattern of the dry film 204 is removed. . As the developing solution, it is preferable to use an aqueous solution of sodium carbonate (Na ₂ CO ₃ ) or potassium carbonate (K ₂ CO ₃ ).

In FIG. 2E, the dry film 204 is removed using a stripping solution to form a predetermined internal circuit pattern 202-1. Here, it is preferable to use the stripping solution containing sodium hydroxide (NaOH), potassium hydroxide (KOH), or the like as the stripping solution.

In FIG. 2F, a second coverlay 203a is applied to protect the internal circuit pattern 202-1 formed on the predetermined window C of the first prepreg 201. In this case, the second coverlay 203a may be partially coated to cover only a portion corresponding to the window of the first prepreg 201, or may be completely coated to apply the entire first prepreg 201. have.

In the embodiment described with reference to FIGS. 2A to 2F, the copper foil 202 is laminated on one surface of the first prepreg 201 where the window C is formed, and the first surface is formed to include the window C on the other surface. After applying the coverlay 203b, the internal circuit pattern 202-1 is formed on the copper foil 202, and then the internal circuit pattern corresponding to the first coverlay 203b and formed on the window C ( A second coverlay 203a protecting 202-1 was applied to form a circuit layer 200.

Thereafter, as illustrated in FIG. 2G, a second prepreg 205 having a window D formed therein is prepared for further stacking. In this case, the window D may be formed to correspond to the window C of the first prepreg 201 and may be formed using a punch, a drill bit, or the like.

On the other hand, although it is preferable to use the second prepreg 205 as the insulating layer, a bonding sheet may be used, and any insulating material having an adhesive flatness may be used. The second prepreg 205 is a material impregnated with glass fiber, which is excellent in dimensional stability and thermal stability but inferior in adhesive strength, and in the case of the bonding sheet, it is composed of only resin, so the adhesiveness is excellent but thermal stability and workability are excellent. It has a downside.

More preferably, the first prepreg 201 and the second prepreg 205 are preferably made of the same material, but in the drawings, hatching is shown differently for explanation. In addition, as shown in FIG. 2H, the second prepreg 205 is preferably made of a material thicker than the first prepreg 201, but the thickness thereof may be the same.

The thickness of the prepreg used as the insulating layer in the manufacturing process of a conventional flexible printed circuit board is about 40 ~ 100㎛, in consideration of the thickness of the finished product, workability and economical efficiency according to the first embodiment of the present invention The thickness of the prepreg 205 is preferably about 40 μm. At this time, according to the embodiment, it is also possible to use a bonding sheet having a thickness of 15 to 25 μm instead of the second prepreg 205 for thin plate molding.

As shown in FIG. 2H, the circuit layer 200 is stacked on both surfaces of the second prepreg 205. This substrate may be the first inner layer 207 of the substrate, as described below.

In addition, as shown in FIG. 2I, the second inner layer 208 having the circuit layer 200 stacked on one surface of the second prepreg 205 is prepared.

Also, as illustrated in FIG. 2J, one surface of the third prepreg 209 in which the window C of the first prepreg 201 and the window E corresponding to the window D of the second prepreg 205 are formed. The insulating substrate 211 to which the third coverlay 210b including the window E is applied is prepared.

Then, as illustrated in FIG. 2K, the second inner layer 208, the second prepreg 205, the insulating substrate 211, and the copper foil layer 212 are formed on both surfaces of the first inner layer 207. After arranging in order, the arranged substrates are pressed from both sides to form a six-layer substrate as shown in FIG. 2L. According to the embodiment, the number of substrates to be laminated may be adjusted.

At this time, the circuit layer 200 and the second prepreg 205 are alternately stacked so that the internal circuit pattern 202-1 faces outward, and then the insulating substrate 211 and the copper foil layer 212 are placed on the outermost side. By laminating and thermocompressing, a six-layer substrate as shown in FIG. 2L can be formed.

In FIG. 2M, a plurality of via holes including a through hole (F) and a blind via hole (G) are formed. The through hole F is for connecting the entire layers of the substrate, and the blind via hole G is for connecting the outer circuit pattern and the circuit pattern thereunder. The through hole F is preferably machined and the blind via hole G is processed by laser drilling.

Then, as shown in FIG. 2N, the copper plating layer 213 is formed by plating for electrical conduction of the inner wall of the hole. Here, since the inner wall of the hole includes the first prepreg 201, the second prepreg 205, and the third prepreg 209, which is an insulating resin, the inside of the hole and electroless copper plating are first performed, It is preferable to form the copper plating layer 213 by performing good electrolytic copper plating.

As shown in FIG. 2O, after the dry film 214 is coated on the copper plating layer 213, a predetermined etching resist pattern is formed through an exposure and development process.

Subsequently, the substrate is etched as shown in FIG. 2P to remove the copper plating layer 213 except for the portion corresponding to the predetermined pattern of the dry film 214, and as shown in FIG. 2Q, the etching resist pattern The outer circuit pattern 213-1 is formed by peeling off the dry film 214 used.

Lastly, as shown in FIG. 2R, the outer layer 220 is coated by applying a fourth coverlay 210a that protects the outer circuit pattern 213-1 formed on the window E while sealing the window E. FIG. By forming the flexible substrate according to the first embodiment of the present invention is completed. In some embodiments, a pretreatment or posttreatment process such as a surface treatment process may be inserted or added.
In the flexible printed circuit board and the method of manufacturing the same according to the first embodiment of the present invention, the first, second, third and fourth coverlays used as the protective film are a general film type, a liquid type and a dry film type. It can include both.
Meanwhile, portions in which the first prepreg 201, the second prepreg 205, and the third prepreg 209 are inserted into both side surfaces of the substrate of FIG. 2R constitute a rigid region, and the center windows C and D are formed. , E) The forming portion constitutes the flexible region.

delete

That is, the rigid region is composed of a plurality of circuit layers on which circuit patterns are formed and a plurality of insulating layers stacked between the plurality of circuit layers, and the flexible region capable of 3D change is a plurality of circuit patterns inserted between a pair of protective films. It consists of.

In the above-described first embodiment of the present invention, additional substrates are stacked on both sides of the first inner layer 207 shown in FIG. 2H to have symmetry, but according to the embodiment, only one surface of the first inner layer 207 may be formed. 2 After the plurality of inner layers 208 and the second prepreg 205 are stacked, the insulating substrate 211 and the copper foil layer 212 are laminated on both sides of the stacked substrates, and then the process shown in FIGS. 2M to 2R. You can also do

3A to 3K are views for explaining a method of manufacturing a flexible substrate according to a second embodiment of the present invention.

First, as shown in FIG. 3A, a first coverlay 303b having a predetermined size is coated on one surface of the copper foil layer 302.

Here, the first coverlay 303b is to protect the circuit pattern of the flexible region to be formed later, and may be applied to a part or the entire surface of the copper foil layer 302.

Thereafter, as illustrated in FIG. 3B, the first prepreg 301 having the window H having the same size or smaller than the size of the first coverlay 303b is formed on the first surface of the copper foil layer 302. Laminate so that 303b is exposed.

In this case, the window H region of the first prepreg 301 forms a flexible region of the flexible substrate according to the second embodiment of the present invention.

In addition, the window H process can be formed using a punching process, a drill bit, etc.

Next, as shown in FIG. 3C, the etching resist pattern 304 is formed on the other surface of the copper foil layer 302.

As an example of a method of forming the etching resist pattern 304, an etching resist having a predetermined circuit pattern formed by performing an exposure and developing process after closely contacting an artwork film having a predetermined circuit pattern printed on a photosensitive material such as a dry film. Pattern 304 may be formed.

Thereafter, as illustrated in FIG. 3D, an etching process is performed on the copper foil layer 302 on which the etching resist pattern 304 is formed to form the internal circuit pattern 302-1.

That is, when the copper foil layer 302 on which the etching resist pattern 304 is formed is immersed in the etching liquid, the copper foil layer 302 of the remaining portions except for the portion corresponding to the etching resist pattern 304 is removed and the etching resist pattern 304 is removed. By peeling off, the internal circuit pattern 302-1 can be formed.

Next, as shown in FIG. 3E, an internal circuit pattern 302-1 corresponding to the first coverlay 303b on the internal circuit pattern 302-1 and formed on the first coverlay 303b is formed. The protective cover layer 303a is applied to form the circuit layer 300.

As described above, in the flexible printed circuit board according to the second embodiment of the present invention, the first coverlay 303b and the second coverlay 303a protecting the internal circuit pattern 302-1 form a flexible region. There is an effect that can implement a flexible region having a softness like polyimide without using a polyimide copper clad laminate.

Thereafter, as illustrated in FIG. 3F, a plurality of circuit layers 300 and a plurality of second prepregs 310 in which the windows I are formed are alternately stacked, and a coverlay 323b is applied on the upper and lower surfaces. The preliminary outer layer 520 having the window J on one surface of the copper foil layer 322 and the third prepreg 321 stacked thereon is stacked.

Here, the window J formed in the third prepreg 321 is formed to correspond to the window I formed in the second prepreg 310 and the window H formed in the first prepreg 301.

The third prepreg 321, the second prepreg 310, and the first prepreg 301 may use the same material, but are shown with different hatching for explanation. In addition, the semipre-cured prepreg 301, 310, 321 which forms the insulating layer can use a bonding sheet instead.

In addition, the prepreg 301, 310, 321 is about 40 ~ 100㎛ in the conventional manufacturing process of the flexible printed circuit board, but the flexible printed circuit board according to the present invention in consideration of the thickness, workability and economical efficiency of the finished product In the prepreg (301, 310, 321) it is preferable to use about 40㎛, according to the embodiment it is also possible to use a bonding sheet having a thickness of 15 ~ 25㎛ instead of the prepreg according to the embodiment.

Meanwhile, the prepregs 301, 310, and 321 not only increase the mechanical strength of the rigid region of the flexible substrate according to the present invention, but also serve as an adhesive layer during thermocompression bonding.

Next, as illustrated in FIG. 3G, the plurality of stacked circuit layers 300, the plurality of second prepregs 310, and the preliminary outer layer 320 are thermocompressed.

Thereafter, as shown in FIG. 3H, a through hole J and a blind via hole K for interlayer electrical connection are formed.

The through hole J is for connecting the entire substrate layers, and the blind via hole K is for connecting the outer layer and the circuit layer thereunder, and may be formed by mechanical drilling or laser drilling.

Next, as shown in FIG. 3I, a copper plating layer 331 is formed on the copper foil layer 322, the through hole J, and the blind via hole K for the electrical conduction of the inner wall of the hole.

The copper plating layer 331 is formed by performing electroless copper plating and electrolytic copper plating. In this case, the blind via hole K may be filled by the copper plating layer 331.

Thereafter, as illustrated in FIG. 3J, an etching resist pattern (not shown) is formed on the copper plating layer 331 and an etching process is performed to form the outer circuit pattern 331-1.

Finally, as shown in FIG. 3K, by forming the outer layer 330 by applying a fourth coverlay 323a corresponding to the third coverlay 323b and protecting the outer circuit pattern 331-1, A flexible printed circuit board according to a second embodiment of the present invention is completed.

In this case, the fourth coverlay 323a may be entirely coated on the outer circuit pattern 331-1.
In the flexible printed circuit board and the manufacturing method thereof according to the second embodiment of the present invention, the first, second, third and fourth coverlays used as the protective film are a general film type, a liquid type and a dry film type. It can include both.
Meanwhile, portions in which the first prepreg 301, the second prepreg 310, and the third prepreg 321 are inserted into both side surfaces of the substrate of FIG. 3K constitute a rigid region, and the center windows H and I are formed. , J) the forming portion constitutes the flexible region.

delete

That is, the rigid region is composed of a plurality of circuit layers on which circuit patterns are formed and a plurality of insulating layers stacked between the plurality of circuit layers, and the flexible region capable of 3D change is a plurality of circuit patterns inserted between a pair of protective films. It consists of.

4A to 4R illustrate a method of manufacturing a six-layer flexible printed circuit board by stacking double side surfaces according to a third embodiment of the present invention.

First, as shown in FIG. 4A, a first prepreg 401 having a window L having a predetermined size is prepared. The window L can be formed using a punch, a drill bit, or the like.

Next, as shown in FIG. 4B, protective films such as the first coverlay 402a and the second coverlay 402b are coated on both surfaces of the first prepreg 401. The first coverlay 402a and the second coverlay 402b are provided to cover and protect the circuit patterns to be formed in a later process. Although FIG. 4B illustrates a partial coating to cover the window L, the first coverlay 402a and the second coverlay 402b are covered. The front cover may be applied so that the coverlay 402a and the second coverlay 402b cover the entire substrate.

In FIG. 4C, the copper foil layer 403 is laminated on both surfaces of the first prepreg 401 including the first coverlay 402a and the second coverlay 402b and then pressed. The said process may use the batch lamination method which presses the 1st prepreg 401, the 1st coverlay 402a, the 2nd coverlay 402b, and the copper foil layer 403 at once.

After pressing, the inner via hole M is formed as shown in FIG. 4D.

As shown in FIG. 4E, a copper plating layer 404 is formed on the copper foil layer 403 for electrical connection between the layers in the inner via hole M. Referring to FIG. Here, the copper plating layer 404 is formed by performing electroless copper plating on the inner wall of the via hole M since the first prepreg 401, which is an insulator, is exposed to the electroless copper plating first.

In FIG. 4F, a dry film 405 is applied on the copper plating layer 404 to be used as an etching resist. Instead of the dry film 405, another etching resist material such as a liquid photosensitive material may be applied. Then, the artwork film on which the predetermined pattern is printed is brought into close contact with the dry film 405, and then a predetermined etching resist pattern is formed through an exposure and development process.

In FIG. 4G, the copper foil layer 403 and the copper plating layer 404 of the remaining portion except for the portion corresponding to the predetermined pattern of the dry film 405 are etched by immersing the substrate in the etching solution.

As shown in FIG. 4H, the applied dry film 405 is removed using a stripping solution to form a predetermined internal circuit pattern 404-1. Here, the stripping solution is removed using a stripping solution containing sodium hydroxide (NaOH) or potassium hydroxide (KOH).

As shown in FIG. 4I, an internal circuit pattern 404-1 corresponding to the first coverlay 402a and the second coverlay 402b and formed on the first coverlay 402a and the second coverlay 402b. The third coverlay 406a and the fourth coverlay 406b are respectively applied to form the circuit layer 400. In this case, the third coverlay 406a and the fourth coverlay 406b may be completely coated on the entire substrate according to the embodiment.

In addition, as illustrated in FIG. 4J, an insulating layer such as a second prepreg 410 or a bonding sheet having a window N corresponding to the window M of the first prepreg 401 is prepared. The second prepreg 410 and the first prepreg 401 may be made of the same material, but are shown by different hatching for explanation.

The second prepreg 410 of FIG. 4J preferably uses a thicker thickness than the first prepreg 401. For example, it is preferable to use a material having a thickness of about 60 μm for the second prepreg 410 and about 40 μm for the first prepreg 401. In some embodiments, the thicknesses of the second prepreg 410 and the first prepreg 401 may be the same.

Thereafter, as shown in FIG. 4K, when the circuit layer 400 is disposed on both surfaces of the second prepreg 410, and as shown in FIG. 4L, the substrate is composed of four layers by pressing under heating and pressing.

In addition, as in FIG. 4M, the second prepreg 410 is stacked on both sides of the substrate of FIG. 4K.

Thereafter, as shown in FIG. 4N, a window O corresponding to the window M of the first prepreg 401 and the window N of the second prepreg 410 is formed, and the window O is formed on one surface thereof. The third prepreg 421 and the copper foil layer 423 to which the fifth coverlay 422b including) is laminated are pressed, respectively.

As shown in FIG. 4O, a through hole P for electrical connection of the entire substrate and a blind via hole Q for electrical connection between the two layers are formed.

Thereafter, as shown in FIG. 4P, a copper plating layer 424 is formed for electrical conduction of the inner wall of the hole. Here, since the first, second and third prepregs 401, 410, and 421 that are insulators are exposed on the inner wall of the hole, the electroless copper plating is performed first, and then the electroplating layer 424 is formed by performing electrolytic copper plating having good physical properties. ).

Thereafter, as shown in FIG. 4Q, after forming an etching resist pattern (not shown) on the copper plating layer 424, an etching process is performed to form an outer layer circuit pattern 424-1.

Finally, as shown in FIG. 4R, the sixth coverlay 422a corresponding to the fifth coverlay 422b and protecting the outer circuit pattern 424-1 formed on the fifth coverlay 422b is provided. By applying and completing the outer layer 420, the flexible printed circuit board according to the second embodiment of the present invention is completed.
In the flexible printed circuit board and the manufacturing method thereof according to the third embodiment of the present invention, the first, second, third, fourth, fifth and sixth coverlays used as the protective film may be a general-purpose film type, Both liquid type and dry film type may be included.
On the other hand, as shown in Figure 4r, the substrate according to the third embodiment of the present invention has a form in which a plurality of double-sided circuit layer 400, a plurality of second prepreg 410 and the outer layer 420 is stacked. . The number of circuit layers 400 and second prepregs 410 stacked may vary according to embodiments.

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Portions in which the first, second and third prepregs 401, 410, and 421 are inserted into both sides of the substrate of FIG. 4R constitute a rigid region, and a center where the windows M, N, and O are formed is a flexible region. Configure.

That is, the rigid region is composed of a plurality of circuit layers and a plurality of insulating layers stacked between the plurality of circuit layers, and the flexible region is composed of a plurality of circuit layers inserted between a pair of protective films.

In the flexible printed circuit board according to the third exemplary embodiment of the present invention, a plurality of circuit layers 400 and a plurality of second prepregs 410 are alternately stacked, and a window O is formed so that only one window O is formed. After the third prepreg 421 and the copper foil layer 423 to which the fifth coverlay 422b including) is applied are laminated on the outer shell and thermally compressed, the third prepreg 421 and the copper foil layer 423 may be formed by performing the processes of FIGS. 4O to 4R. have.

In addition, the flexible printed circuit board according to the present invention forms a circuit pattern of a flexible region by using a coverlay and forms a rigid region by stacking an insulating layer having a window, thereby forming a rigid printed circuit board without using a polyimide copper clad laminate. Can be formed.

In other words, by using a low-cost coverlay to support the flexible area and to connect the rigid area instead of the expensive polyimide copper clad laminate, the adhesive reliability is good, the bending property can be realized, and there is no opening of the bent part, It can bring about an effect of reducing.

Although the present invention has been described above by way of examples, the scope of the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the present invention. It is intended that the scope of the invention only be limited by the following claims.

As described above, according to the present invention, since the expensive polyimide copper-clad laminate (PICCL) to which the copper foil and the polyimide film are adhered is not required, the manufacturing cost of the substrate is greatly reduced.

Further, according to the present invention, it is possible to produce a product having the same flexibility as that of the existing product because it is made of a coverlay instead of a prepreg at a low cost and a bent portion.

Claims (15)

(A) a first insulating layer having a first window formed therein, an internal circuit pattern formed on one surface of the first insulating layer including the first window, and a first protecting the internal circuit pattern formed on the first window; And preparing a circuit layer including a second protective film; (B) preparing a second insulating layer on which a second window corresponding to the first window is formed; (C) laminating a plurality of the circuit layer and the second insulating layer to form a laminate; And (D) third and fourth external circuit patterns corresponding to the internal circuit patterns and third windows corresponding to the first and second windows are formed, and protect external circuit patterns formed on the third windows. Forming an outer layer including a protective film on the upper and lower parts of the laminate And a region corresponding to the first, second, and third windows is a flexible region. The method of claim 1, wherein step (A) (A-1) providing a first insulating layer having a first window formed thereon; (A-2) applying a first protective film to one surface of the first insulating layer to include the first window; (A-3) laminating a copper foil layer on the other side of the first insulating layer; (A-4) forming an internal circuit pattern on the copper foil layer; And (A-5) applying a second protective film to protect the internal circuit pattern formed on the first window together with the first protective film Method of manufacturing a flexible printed circuit board comprising a. The method of claim 1, wherein step (A) (A-1) applying a first protective film of a predetermined size to one surface of the copper foil layer; (A-2) stacking a first insulating layer having a first window having a smaller size than the first protective film on one surface of the copper foil layer such that a portion of the first protective film is exposed; (A-3) forming an internal circuit pattern on the copper foil layer; And (A-4) applying a second protective film corresponding to the first protective film and protecting the internal circuit pattern on the internal circuit pattern; A flexible printed circuit board manufacturing method comprising a. The method of claim 1, wherein the first insulating layer and the second insulating layer are prepregs or bonding sheets. The flexible printed circuit board of claim 1, wherein the first, second, third, and fourth protective films are coverlays of a general-purpose film type, coverlays of a liquid type, or coverlays of a dry film type. Manufacturing method. The method of claim 1, wherein step (D) (D-1) to include a third insulating layer having a third window having the same size and position as the first window and the second window, a copper foil layer formed on one surface of the third insulating layer, and the third window Stacking a preliminary outer layer including a third protective film formed on the third insulating layer above and below the laminate; (D-2) forming an external circuit pattern including a plurality of via holes on the copper foil layer; And (D-3) forming an outer layer by applying a fourth protective film that protects the external circuit pattern on the third window together with the third protective film. Method of manufacturing a flexible printed circuit board comprising a. The method of claim 6, wherein the plurality of via holes in the step (D-2) include through holes and blind via holes. A flexible printed circuit board manufactured by the method according to claim 1. (A) forming first and second internal circuit patterns electrically connected to each other on both surfaces of the first insulating layer on which the first window is formed, and corresponding to the first window on both surfaces of the first insulating layer and on the first window; Preparing a circuit layer by applying first, second, third and fourth protective films protecting the first and second internal circuit patterns; (B) preparing a second insulating layer on which a second window corresponding to the first window is formed; (C) laminating a plurality of the circuit layer and the second insulating layer to form a laminate; And (D) forming an external circuit pattern corresponding to the first and second internal circuit patterns and a third window corresponding to the first and second windows, and protecting the external circuit pattern formed on the third window. Forming an outer layer including a fifth and a sixth protective film on the upper and lower parts of the laminate; And a region corresponding to the first, second, and third windows is a flexible region. The method of claim 9, wherein step (A) (A-1) providing a first insulating layer having a first window formed thereon; (A-2) applying a first protective film and a second protective film to upper and lower surfaces of the first insulating layer to include the first window; (A-3) laminating a copper foil layer on upper and lower surfaces of the first insulating layer to which the first protective film and the second protective film are applied; (A-4) forming internal via holes on the copper foil layer and performing electroless plating and electrolytic copper plating; (A-5) forming first and second internal circuit patterns on the copper foil layer; And (A-6) applying a third protective film and a fourth protective film to protect the first and second internal circuit patterns on the first protective film and the second protective film; A flexible printed circuit board comprising a. The method of claim 9, wherein the first insulating layer and the second insulating layer are prepregs or bonding sheets. The method of claim 9, wherein the first, second, third, fourth, fifth and sixth protective film is a coverlay of the general film type, liquid coverlay or dry film type coverlay, characterized in that Method for manufacturing a flexible printed circuit board. The method of claim 9, wherein step (D) (D-1) to include a third insulating layer having a third window having the same size and position as the first window and the second window, a copper foil layer formed on one surface of the third insulating layer, and the third window Stacking a preliminary outer layer including a fifth protective film formed on the third insulating layer above and below the laminate; (D-2) forming an external circuit pattern including a plurality of via holes on the copper foil layer; And (D-3) forming an outer layer by applying a sixth protective film protecting the external circuit pattern on the third window together with the fifth protective film; Method of manufacturing a flexible printed circuit board comprising a. 15. The method of claim 13, wherein the plurality of via holes in the step (D-2) include through holes and blind via holes. A flexible printed circuit board manufactured by the method according to claim 9.

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