TWI599287B - Method for manufacturing flexible printed circuit board - Google Patents

Description

Flexible circuit board manufacturing method

The present invention relates to the field of circuit board manufacturing, and in particular, to a method for fabricating a flexible circuit board.

At present, in the circuit board manufacturing method generally used in the field of circuit board manufacturing, as shown in FIG. 10, after the circuit is completed, the conductive line 61 is protruded on the substrate 62, and the adhesion between the conductive line 61 and the substrate 62 depends only on The bonding force between the surface 611 of the conductive line 61 in contact with the substrate 62 and the substrate 62. As the conductive line develops toward the refinement direction, the contact area between the conductive line and the substrate gradually becomes smaller, so that the conductive line is easily peeled off from the substrate, thereby causing a short circuit. In addition, as shown in FIG. 11, when the cover film 70 is formed on the conductive line 61, since the adhesive layer 71 of the cover film 70 is filled and filled with a gap between the conductive lines 61, the pressed portion is pressed. The surface of the board is uneven, which is not conducive to subsequent surface packaging.

In view of the above, it is necessary to provide a flexible circuit board manufacturing method that overcomes the above problems.

A flexible circuit board manufacturing method comprising the steps of: forming a photosensitive resin on a removable substrate; selectively removing a portion of the photosensitive resin to form a plurality of grooves, the grooves exposing a portion of the substrate; The trench is filled with a conductive metal to form a conductive line, and the surface of the conductive line is flush with the surface of the photosensitive resin; the substrate is removed to obtain a flexible circuit board in which a conductive line is embedded in the photosensitive resin.

Compared with the prior art, the flexible circuit board manufacturing method provided by the present invention can increase the conductive line and the substrate by using a photosensitive resin as a substrate and embedding a conductive line in the photosensitive resin. The contact area between them is to increase the adhesion between the conductive line and the substrate; on the other hand, the surface of the finally formed flexible circuit board can be flattened to facilitate subsequent surface packaging.

1 is a schematic cross-sectional view of a substrate provided by an embodiment of the present invention.

2 is a schematic cross-sectional view showing the photosensitive resin and the photoresist layer being pressed on opposite sides of the substrate of FIG.

FIG. 3 is a schematic perspective view showing a portion of the photosensitive resin of FIG. 2 selectively removing a plurality of trenches and forming the photoresist layer to form a plating barrier layer.

4 is a schematic cross-sectional view of FIG. 3 after the photosensitive resin is formed into a plurality of grooves.

FIG. 5 is a schematic cross-sectional view showing a conductive line formed by filling a conductive metal from the trench of FIG. 4. FIG.

Figure 6 is a schematic cross-sectional view showing the plating barrier layer of Figure 5 removed.

Fig. 7 is a schematic cross-sectional view showing the surface of the photosensitive resin and the conductive wiring in Fig. 6 after the first cover film is formed.

Figure 8 is a schematic cross-sectional view showing the substrate of Figure 7 removed to expose the photosensitive resin and conductive lines.

Figure 9 is a schematic cross-sectional view showing the photosensitive resin and the conductive trace of Figure 8 after forming a second cover film away from the first cover film side.

Figure 10 is a cross-sectional view showing the completion of the line fabrication in the prior art.

Figure 11 is a cross-sectional view of the line surface of Figure 10 after the cover film is pressed.

The method for fabricating the flexible circuit board provided by the present invention will be described in detail below with reference to specific embodiments.

A flexible circuit board manufacturing method provided by an embodiment of the present invention includes the following steps:

In the first step, referring to Figure 1, a substrate 10 is provided.

The substrate 10 includes opposing first and second surfaces 11 and 12. The substrate 10 may be a conductive metal material such as copper, aluminum or silver. In this embodiment, the substrate 10 is pure copper.

In the second step, referring to FIG. 2, a photosensitive resin 21 is formed on the substrate 10.

In the present embodiment, the photosensitive resin 21 is formed on the first surface 11 of the substrate 10 by vacuum pressing. The substrate 10 is removable from the photosensitive resin 21. In the present embodiment, the photoresist layer 22 is vacuum-bonded to the second surface 12 while a photosensitive resin 21 is formed on the first surface 11.

The photosensitive resin 21 completely covers the first surface 11. The photoresist layer 22 completely covers the second surface 12. In the embodiment, the photoresist layer 22 is a common dry film. The photosensitive resin 21 has excellent flame retardancy, no halogen, no halogen, high resolution, excellent ion migration resistance, gold resistance, and low repellency. The photosensitive resin 21 has a relatively low dissipation factor Df (Dissipation Factor) and a dielectric constant Dk (Dielectric Constant) compared to the photoresist layer 22. In the present embodiment, the photosensitive resin 21 has a dielectric constant Dk of 2.8 and a loss factor Df of 0.005. The photosensitive resin 21 may have a thickness of 25, 30, 38 or 45 μm.

In the third step, referring to FIG. 2, FIG. 3 and FIG. 4, the photosensitive resin 21 is selectively removed to form a plurality of grooves 211.

In the present embodiment, a portion of the photosensitive resin 21 is selectively removed by an exposure development method to form the trench 211. The trench 211 exposes a portion of the first surface 11 of the substrate 10. Each of the grooves 211 has two side walls 2111. In this embodiment, the sidewalls 2111 are parallel to each other, and the sidewalls 2111 are perpendicular to the first surface 11 of the substrate 10.

In the present embodiment, the photoresist layer 22 is subjected to exposure development to selectively form the plating resist layer 31 while selectively removing a portion of the photosensitive resin 21. The plating barrier layer 31 completely covers the second surface 12.

In the fourth step, referring to FIG. 5, a conductive metal is filled in the trench 211 to form a conductive line 40.

The conductive line 40 is embedded in the photosensitive resin 21. The surface of the conductive line 40 is flush with the surface of the photosensitive resin 21. That is, the surface of the conductive line 40 facing away from the substrate 10 and the surface of the photosensitive resin 21 facing away from the substrate 10 are in the same plane.

In this embodiment, the conductive line 40 can be formed by electroplating.

In the fifth step, referring to FIG. 5 and FIG. 6, the plating barrier layer 31 is removed to expose the substrate 10.

In the sixth step, referring to FIG. 7, a first cover film 51 is formed on the surface of the photosensitive resin 21 and the conductive line 40.

The first cover film 51 includes a first adhesive layer 511 and a first film layer 512. The first adhesive layer 511 is closer to the photosensitive resin 21 and the conductive line 40 than the first film layer 512.

In the seventh step, referring to FIG. 7 and FIG. 8, the substrate 10 is removed to expose the photosensitive resin 21 and the conductive line 40.

In the present embodiment, the substrate 10 is removed by etching.

In the eighth step, referring to FIG. 8 and FIG. 9, a second cover film 52 is formed on the side of the photosensitive resin 21 and the conductive line 40 facing away from the first cover film 51.

The second cover film 52 includes a second adhesive layer 521 and a second film layer 522. The second adhesive layer 521 is closer to the photosensitive resin 21 and the conductive line 40 than the second film layer 522.

It can be understood that in other embodiments, the foregoing fifth step and the sixth step can change the order.

It can be understood that, in other embodiments, the flexible circuit board manufacturing method may not include vacuum-bonding the photoresist layer 22 on the second surface 12 of the substrate 10; exposing the photoresist layer 22 Developing the plating barrier layer 31; and removing the plating barrier layer 31 to expose the substrate 10. At this time, while the conductive metal is filled in the trench 211 to form the conductive line 40, a plating layer is formed on the second surface 12 of the substrate 10; while the substrate 10 is removed, the substrate 10 is removed. The plating on the second surface 12 is sufficient.

It can be understood that in other embodiments, the substrate 10 can be made of a dielectric material. At this time, before the conductive metal is filled in the trench 211 to form the conductive line 40, a plating seed layer is formed on the first surface 11 of the substrate 10 and the sidewall 2111 of the trench 211 exposed by the trench 211. .

Compared with the prior art, the flexible circuit board manufacturing method provided by the present invention can increase the conductive line and the substrate by using a photosensitive resin as a substrate and embedding a conductive line in the photosensitive resin. The contact area between them is to increase the adhesion between the conductive line and the substrate; on the other hand, the surface of the finally formed flexible circuit board can be flattened to facilitate subsequent surface packaging.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only for the preferred embodiment of the present invention and the data listed therein are used for testing and reference, and the scope of patent application in this case cannot be limited thereby. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

10, 62‧‧‧ base

11‧‧‧ first surface

12‧‧‧ second surface

21‧‧‧Photosensitive resin

22‧‧‧Photoresist

211‧‧‧ trench

31‧‧‧ plating barrier

40, 61‧‧‧ conductive lines

51‧‧‧First cover film

511‧‧‧First layer

512‧‧‧ first film

52‧‧‧second cover film

521‧‧‧Second layer

522‧‧‧Second film

70‧‧‧ Cover film

71‧‧‧ glue layer

611‧‧‧ surface

no

21‧‧‧Photosensitive resin

40‧‧‧Electrical circuit

51‧‧‧First cover film

52‧‧‧second cover film

521‧‧‧Second layer

522‧‧‧Second film

Claims (7)

A method for manufacturing a flexible circuit board, comprising the steps of:
Forming a photosensitive resin on a removable substrate;
Selectively removing a portion of the photosensitive resin to form a plurality of grooves, the grooves exposing a portion of the substrate;
Filling a conductive metal in the trench to form a conductive line, the conductive line surface being flush with the surface of the photosensitive resin;
The substrate is removed to obtain a flexible circuit board in which a conductive line is embedded in the photosensitive resin. The method of fabricating a flexible circuit board according to claim 1, wherein the conductive line in the trench has two sidewalls parallel to each other, the sidewall being perpendicular to the substrate. The method of fabricating a flexible circuit board according to claim 1, wherein after the conductive metal is filled in the trench to form a conductive line, and before the substrate is removed, the photosensitive resin and the surface of the conductive line are further included A first cover film is formed. The method of fabricating a flexible circuit board according to claim 3, wherein after the substrate is removed, the method further comprises forming a second cover film on the side of the conductive line and the photosensitive resin facing away from the first cover film. The flexible circuit board manufacturing method according to claim 1, wherein a photosensitive resin is formed on a removable substrate by vacuum pressing. The flexible circuit board manufacturing method according to claim 1, wherein a plurality of grooves are formed by selectively removing a portion of the photosensitive resin by an exposure developing method. The method of fabricating a flexible circuit board according to claim 1, wherein the conductive metal is filled in the trench by electroplating to form a conductive line.