TWI386143B - Muti-layer printed circuit board and method for making same - Google Patents

Description

Multilayer circuit board and manufacturing method thereof

The present invention relates to circuit board technology, and in particular to a multilayer circuit board having a specific adhesive layer structure and a method of fabricating the same.

With the rapid development of the electronics industry, the production technology of circuit boards, which are the basic components of electronic products, is becoming more and more important. The circuit board is generally fabricated by a series of processes such as cutting, drilling, etching, exposing, developing, pressing, and molding a copper-clad substrate. For details, see "Dielectric characterization of printed circuit board substrates" by C. H. Steer et al., Proceedings of the IEEE, Vol. 39, No. 2 (August 2002).

Generally, a multilayer circuit board can be formed by thermal compression bonding of an inner layer board and an outer layer board. A film is disposed between the inner layer and the outer layer, and after the thermocompression, the inner layer and the outer layer are closely adhered by the film to form a multilayer circuit board. Generally, an open area is preliminarily formed on the film, and the open area is mainly used to make the multilayer circuit board have appropriate flexibility in a specific area, so that the multilayer circuit board can be bent and applied to a specific electronic device. However, during the thermal compression bonding of the outer layer and the inner layer, the film is softened and melted due to heat, and when the film is thermally pressed to the open area, the film has a large difference at the opposite edges of the opening region (for example, When the thickness of the film is 25 μm, the difference at the edge of the opening region is 25 μm), so that the gas interposed between the film and the outer layer or the inner layer plate stays at the opposite edges of the opening region and cannot be dissipated in time. Air bubbles are formed after hot pressing. In the subsequent processing of the multilayer circuit board, the air bubbles are thermally expanded to form a raised region, which not only affects the appearance quality of the multilayer circuit board, but also causes the multilayer circuit board to easily cause delamination during subsequent processing or use to cause the circuit board to fail. Moreover, in the process of subsequently pressing the dry film on the multilayer circuit board, the copper layer of the outer layer may be broken at the opening area of the film due to the height difference, causing the line to break and affecting the conduction quality of the multilayer circuit board.

In view of the above, in view of the above problems, it is necessary to provide a multilayer circuit board which can more effectively prevent bubble formation in a multilayer circuit board and prevent breakage of a line, and a manufacturing method thereof.

A multilayer circuit board and a method of fabricating the same will be described below with reference to specific embodiments.

A method of fabricating a multilayer circuit board, comprising the steps of: providing an inner layer board and an outer layer board, the inner layer board comprising a first insulating layer and a first conductive layer disposed on at least one surface of the first insulating layer, the outer layer board comprising a second insulating layer and a second conductive layer disposed on at least one surface of the second insulating layer; a film is provided, the film is pre-opened with an opening area defined by two opposite design reference lines on the film An opening edge region adjacent to each of the design reference lines is formed with a plurality of uniform and continuously arranged zigzag structures or a plurality of evenly and continuously arranged wave-shaped structures projecting into the opening region; placing the film in the film Between the inner layer board and the outer layer board, and rolling and thermally pressing the inner layer board and the outer layer board in a direction perpendicular to the design reference line by using a first rolling device; and providing a dry film, the dry film is placed thereon On the outer side of the outer layer, the dry film is thermocompression bonded to the outer layer by a second rolling device.

A multi-layer circuit board comprising an inner layer board, an outer layer board, a film and a dry film, the film being bonded between the inner layer board and the outer layer board, the film opening an opening area, the opening area adjacent to the opening of the film The edge region has a buffer portion formed of the film, and the dry film is attached to the outer layer.

Compared with the prior art, the multi-layer circuit board of the present technical solution and the manufacturing method thereof have an open area on the film, and a zigzag structure or a wave is arranged in the hot pressing direction in the opening edge area adjacent to the film in the opening area. The zigzag structure or the wavy structure of the film forms a buffer portion in the open area, so that the gas staying in the edge region of the opening can be effectively driven to avoid the edge of the opening. The bubble ridge area is formed at the area to improve the appearance quality of the multilayer circuit board, and effectively prevent the delamination of the multilayer circuit board from being lost during subsequent processing or use. Moreover, since the difference in height between the outer layer and the inner layer at the edge region of the opening is effectively reduced by the buffer portion, the copper layer of the outer layer is not in the film opening during the subsequent pressing of the multilayer circuit board into the dry film. The area is disconnected due to the height difference, causing the line to break, thereby improving the conduction quality of the multilayer circuit board.

The multi-layer circuit board of the present technical solution and the manufacturing method thereof will be further described in detail below with reference to the accompanying drawings and embodiments.

Referring to FIG. 1 , an embodiment of the present technical solution provides a method for fabricating a multi-layer circuit board, which includes the following steps:

Step 110, providing an inner layer and an outer layer, the inner layer comprising a first insulating layer and a first conductive layer disposed on at least one surface of the first insulating layer, the outer layer including a second insulating layer and disposed on the first a second conductive layer of at least one surface of the second insulating layer.

Referring to FIG. 2 , the inner layer 10 provided in this embodiment includes a first insulating layer 11 and a first conductive layer 12 . The first insulating layer 11 has a first surface 111 and a second surface 112 opposite to each other. The first surface 111 is parallel to the second surface 112. A first conductive layer 12 is disposed on each of the first surface 111 and the second surface 112, that is, the inner layer 10 is a double-sided circuit board. Of course, the inner layer 10 can also be a single panel having only one layer of the first conductive layer 12. In addition, a cover layer (not shown) may be disposed on the outer side of the first conductive layer 12, and the cover layer may be used to protect the first conductive layer 12. However, the overlay can also be omitted according to the actual requirements of different boards.

The outer layer 20 includes a second insulating layer 21 and a second conductive layer 22. The second insulating layer 21 has opposite third and second surfaces 211, 212. The third surface 211 is parallel to the fourth surface 212. In this embodiment, the second conductive layer 22 is disposed on the fourth surface 212. Of course, the outer layer 20 can also be provided with a second conductive layer 22 on the third surface 211 to form a double-sided circuit board.

Step 120, providing a film, the film is pre-opened with an opening area defined by two opposite design reference lines, and an opening edge area adjacent to each design reference line on the film is formed in the opening area A plurality of uniformly and continuously arranged zigzag structures or a plurality of evenly and continuously arranged wave structures.

Referring to FIG. 3, the film 30 is pre-opened with an opening area 32. The open area 32 defines two design reference lines L ₀ that are parallel to each other, the two design reference lines L ₀ being the original boundaries of the open areas 32 that are predetermined according to customer design requirements. The two design reference lines L ₀ are both perpendicular to the thermal pressing direction P of the film.

The film 30 and the design of each reference line L ₀ adjacent to the edge region of the opening 305 is formed with a plurality of zigzag structures 34. Each zigzag structure 34 has a first end 341 and a second end 342 opposite thereto. The first end 341 is coupled to the body 302 of the film 30. The second end 342 extends to the open area 32. A line defining a first end 341 of the plurality of zigzag structures 34 is a first reference line L ₁ , and a line defining a second end 342 of the plurality of zigzag structures 34 is a second reference line L ₂ . The first reference line L ₁ L ₀ of the distance to the reference line designed D ₁ equal to the second reference line L ₀ L ₂ of a distance to the reference line designed D _2. Preferably, the first reference line L ₁ to L ₀ distance D of the baseline design _1, and the second reference line L ₀ L ₂ of a distance to the reference line D design values are in the range of ₂ to 0.5mm Between 2mm. The regions of the plurality of zigzag structures 34 are collectively formed with a glue region 343, and all regions between each adjacent two zigzag structures 34 together form a glueless region 344. The glued zone 343 and the glueless zone 344 together form an open edge region 305. In this embodiment, the rubberized area 343 is equal to the area of the glueless area 344. Each zigzag structure 34 has a first side 345 and a second side 346 that are joined. The first side 345 is equal in length to the second side 346. Preferably, the angle between the first side 345 and the second side 346 is 60°. In the present embodiment, only the film 30 has an open area 32. Further, in other embodiments, the film 30 may have a plurality of open areas 32 which may be arranged in a line on the film 30 or Matrix arrangement.

Referring to FIG. 4, another film 40 of the present technical solution is provided with an opening area 42 in advance. The open area 42 defines two design reference lines L ₁₀ that are parallel to each other, the two design reference lines L ₁₀ being the original boundaries of the open area 42 that is predetermined according to customer design requirements. The two design reference lines L ₁₀ are both perpendicular to the thermal pressing direction P of the film. Design of the reference line to each edge region of the opening with a plurality of wave-shaped structure 44 405 40 ₁₀ on the film adjacent to the L. Each undulating structure 44 has a first end 441 and a second end 442 opposite. The first end 441 is coupled to the body 402 of the film 40. The second end 442 extends to the open area 42. A line defining a first end 441 of the plurality of undulating structures 44 is a first reference line L ₁₁ , and a line defining a second end 442 of the plurality of undulating structures 44 is a second reference line L ₁₂ . The first reference line L ₁₁ designed to distance from the reference line L ₁₀ D ₁₁ is equal to the reference line L _{12 is} the second design to the reference line L a distance of ₁₀ D _12. Preferably, the first reference line L ₁₁ from the design to the reference line L _{10. 11} D, L and the second reference line ₁₂ to reference line L from the design of the D ₁₀ values are in the range of ₁₂ to 0.5mm Between 2mm. The regions of the plurality of undulating structures 44 are collectively formed with a glue zone 443, and all regions between each adjacent two undulating structures 44 together form a glueless zone 444. The glued zone 443 and the glueless zone 444 together form an open edge region 405. In this embodiment, the glued area 443 is equal to the area of the glueless area 444. In the present embodiment, only the film 40 has an open area 42. Further, in other embodiments, the film 40 may have a plurality of open areas 42, which may be arranged in a line or on the film 40. Matrix arrangement.

In this embodiment, the film 30 or 40 is a prepreg which is softened and melted after being heated.

Step 130, placing the film between the inner layer and the outer layer, and rolling and thermally pressing the inner layer and the outer layer in a direction perpendicular to the design reference line by using a first rolling device.

Referring to FIG. 5, a film 30 or 40 is placed between the inner layer 10 and the outer layer 20, and the inner layer 10 and the outer layer 20 are thermally pressed by the first rolling device 200. In the present embodiment, the film 30 is taken as an example for specific description. The film 30 is softened and softened by thermal compression, and the first conductive layer 12 of the inner layer 10 and the second insulating layer 21 of the outer layer 20 are bonded. When the first roll 200 rolling means to the film when opening the region 3230, the plurality of zigzag structure 34 is heated to melt and glue filled in the openings corresponding to the design ₀ reference line L of the edge adjacent to area 305.

After the thermocompression bonding, the zigzag structure 34 of the film 30 forms a buffer portion 36 on the opening edge region 305. The buffer portion 36 has a slope shape, and the buffer portion 36 has a wedge portion 362 that connects the inner layer plate 10 and the outer layer plate 20. In this embodiment, the wedge portion 362 connects the first conductive layer 12 and the second insulating layer 21.

Referring to FIG. 6 , in the embodiment, the buffer portion 36 has a buffer boundary 364 that is in contact with the inner layer plate 10 , and the buffer boundary 364 has a micro wave shape.

In addition, the wavy structure 44 of the film 40 can also form a corresponding buffer on the corresponding open edge region 405. The buffer boundary of the buffer portion and the inner layer plate 10 is also slightly wave-shaped.

In step 140, a dry film is provided, and a dry film is placed on the outer side of the outer layer, and the dry film is thermally pressed to the outer layer by a second rolling device.

Referring to FIG. 7, the dry film 50 is placed on the outer side of the outer layer 20, and the dry film 50 is thermally pressed to the outer layer 20 by a second rolling device 300. Since the buffer portion 36 of the film 30 can buffer the degree of bending of the outer layer plate 20 at the corresponding position of the opening edge region 305 during the thermal compression process, the outer layer plate 20 can be prevented from being excessively bent to cause the second conductive layer 22 to be excessively large due to the height difference. Disconnected, causing the line to break.

Referring to FIG. 8-9, the technical solution further provides a multilayer circuit board 100 formed by the above manufacturing method. The multilayer circuit board 100 includes an inner layer 10, an outer layer 20, a film 30, and a dry film 50. The film 30 is bonded between the inner layer 10 and the outer layer 20. The film 30 is provided with an open area 32 having an opening portion 305 adjacent to the film 30 having a buffer portion 36 formed by the film 30. The dry film 50 is attached to the outer layer 20.

Specifically, the inner layer 10 includes a first insulating layer 11 and a first conductive layer 12 disposed on opposite surfaces of the first insulating layer 11. The outer layer 20 includes a second insulating layer 21 and a second conductive layer 22 disposed on at least one surface of the second insulating layer 21. The buffer portion 36 has a slope shape. The buffer portion 36 has a wedge portion 362 that connects the inner layer plate 10 and the outer layer plate 20. The buffer boundary 364 of the buffer portion 36 that is in contact with the inner layer plate 10 has a micro wave shape. In this embodiment, the wedge portion 362 connects the first conductive layer 12 and the second insulating layer 21.

In addition, the inner layer panel 10 may further include a cover layer (not shown) disposed on the outer side of the first conductive layer 12. At this time, the wedge portion 362 of the buffer portion 36 connects the cover layer and the second insulating layer 21.

When the multi-layer circuit board 100 has a plurality of inner-layer boards 10, the multi-layer board manufacturing method provided by the embodiment can be used to first heat-press the plurality of inner layer boards 10 with film 30 or 40, and then use the film 30 or The outer layer 20 is thermocompression bonded to the opposite sides of the plurality of inner layer sheets 10 to obtain a multilayer circuit board 100 having a more conductive layer structure.

Compared with the prior art, the multi-layer circuit board of the present technical solution and the manufacturing method thereof have an open area on the film, and a zigzag structure or a wave is arranged in the hot pressing direction in the opening edge area adjacent to the film in the opening area. The zigzag structure or the wavy structure of the film forms a buffer portion in the open area, so that the gas staying in the edge region of the opening can be effectively driven to avoid the edge of the opening. The bubble ridge area is formed at the area to improve the appearance quality of the multilayer circuit board, and effectively prevent the delamination of the multilayer circuit board from being lost during subsequent processing or use. Moreover, since the difference in height between the outer layer and the inner layer at the edge region of the opening is effectively reduced by the buffer portion, the copper layer of the outer layer is not in the film opening during the subsequent pressing of the multilayer circuit board into the dry film. The area is disconnected due to the height difference, causing the line to break, thereby improving the conduction quality of the multilayer circuit board.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. In the prior art, the above description is only a preferred embodiment of the present invention, and the scope of the patent application of the present invention 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.

100‧‧‧Multilayer circuit board

10‧‧‧ Inner board

11‧‧‧First insulation

12‧‧‧First conductive layer

111‧‧‧ first surface

112‧‧‧ second surface

20‧‧‧ outer board

21‧‧‧Second insulation

22‧‧‧Second conductive layer

211‧‧‧ third surface

212‧‧‧ fourth surface

30, 40‧‧‧ film

302, 402‧‧‧ subjects

32, 42‧‧‧Open area

34‧‧‧Sawtooth structure

341, 441‧‧‧ first end

342, 442‧‧‧ second end

343, 443‧‧‧ with glue zone

344, 444‧‧‧No glue zone

345‧‧‧ first side

346‧‧‧ second side

305, 405 ‧ ‧ open edge area

36‧‧‧ buffer

362‧‧‧Wedge

364‧‧‧buffer boundary

44‧‧‧Wave structure

200‧‧‧First rolling device

300‧‧‧Second rolling device

FIG. 1 is a flow chart of a method for fabricating a multilayer circuit board according to an embodiment of the present technical solution.

Figure 2 is a schematic view showing the structure of the inner layer and the outer layer used in the method of Figure 1.

Figure 3 is a schematic view showing the first structure of the film used in the method of Figure 1.

Figure 4 is a schematic view showing the second structure of the film used in the method of Figure 1.

Figure 5 is a schematic view showing the method of Figure 1 using a first rolling device to thermally press the inner and outer sheets through a film.

Figure 6 is a plan view of Figure 5 taken along the I-I direction.

Figure 7 is a schematic view of the method of Figure 1 using a second rolling device to thermocompress a dry film to an outer sheet.

FIG. 8 is a schematic structural view of a multilayer circuit board formed by using the multilayer circuit board manufacturing method of FIG. 1.

Figure 9 is a plan view of Figure 8 taken along the line II-II.

Claims (13)

A method for fabricating a multilayer circuit board, comprising the steps of:
Providing an inner layer board and an outer layer board, the inner layer board including a first insulating layer and a first conductive layer disposed on at least one surface of the first insulating layer, the outer layer board including a second insulating layer and disposed on the second insulating layer a second conductive layer on at least one surface;
Providing a film, the film is pre-opened with an opening area defined by two opposite design reference lines, and an opening edge area adjacent to each design reference line on the film is formed with a convex surface toward the opening area a plurality of evenly and continuously arranged zigzag structures or a plurality of uniformly and continuously arranged wave-shaped structures;
Placing the film between the inner layer board and the outer layer board, and rolling and thermally pressing the inner layer board and the outer layer board in a direction perpendicular to the design reference line by using a first rolling device; and providing a dry film, A dry film is placed on the outer side of the outer layer, and the dry film is heat-compressed to the outer layer by a second rolling device. The method of fabricating a multi-layer circuit board according to claim 1, wherein each of the zigzag structures or each of the wavy structures has opposite first and second ends, and the first end is connected to the main body of the film. The second end extends to the open area. The method of fabricating a multi-layer circuit board according to claim 2, wherein the line connecting the first end of the plurality of zigzag structures or the plurality of undulating structures is a first reference line, and the plurality of zigzags are defined The line connecting the second end of the structure or the plurality of undulating structures is a second reference line, and the distance from the first reference line to the design reference line is equal to the distance from the second reference line to the design reference line. The method of fabricating a multi-layer circuit board according to claim 3, wherein a distance between the first reference line and the design reference line and a distance from the second reference line to the design reference line are both Between 0.5mm and 2mm. The method of fabricating a multi-layer circuit board according to claim 1, wherein the plurality of sawtooth structures or the regions of the plurality of wavy structures are collectively formed with a glue zone, each adjacent two zigzag structures or waves All areas between the structures together form a glue-free zone that is equal to the area of the glue-free zone. The method of fabricating a multilayer circuit board according to claim 1, wherein each of the zigzag structures has a first side and a second side connected to each other, and the first side and the second side are equal in length. The method for fabricating a multilayer circuit board according to claim 6, wherein the angle between the first side and the second side is 60°. The method of fabricating a multilayer circuit board according to claim 1, wherein the film is placed between the inner layer and the outer layer and the inner layer and the outer layer are thermally pressed by a first rolling device. After the plate, a plurality of serrated structures or a plurality of undulating structures of the film form a buffer on the edge region of the opening. The method of fabricating a multilayer circuit board according to claim 8, wherein the buffer portion has a slope shape, and the buffer portion has a wedge portion connecting the inner layer plate and the outer layer plate. The method of fabricating a multilayer circuit board according to claim 8, wherein the buffer portion has a buffer boundary that is in contact with the inner layer plate, and the buffer boundary has a micro wave shape. A multi-layer circuit board comprising an inner layer board, an outer layer board, a film and a dry film, the film being bonded between the inner layer board and the outer layer board, the film opening an opening area, the opening area adjacent to the opening of the film The edge region has a buffer portion formed of the film, and the dry film is attached to the outer layer. The multi-layer circuit board of claim 11, wherein the buffer portion has a slope shape, and the buffer portion has a wedge portion connecting the inner layer board and the outer layer board. The multi-layer circuit board of claim 11, wherein the buffer portion has a buffer boundary that is in contact with the inner layer plate, and the buffer boundary has a micro wave shape.