TWI382804B - And a method of manufacturing a printed circuit board having a cable portion - Google Patents

Description

Method for manufacturing printed circuit board having wiring portion

The present invention relates to a printed circuit board used in an electronic device, and in particular, a multilayer flexible printed circuit board formed by connecting a plurality of component mounting portions by a wiring portion protruding from a component mounting portion.

Although the printed circuit board is mounted on the machine by arranging electronic components, in order to achieve densification of the device, a three-dimensional component assembly is often required. For this reason, a method of bending a printed substrate is required.

Therefore, a multilayer flexible printed circuit board in which a part-constructed portion (requires a thickness portion) and a flexible portion (a wire arranging portion) for connecting the component-constructing portions are integrally formed is provided. By using such a printed circuit board, after the component is mounted, the flexible portion is bent to be three-dimensionally arranged, and the space can be effectively utilized to achieve densification.

In recent years, such a printed circuit board has been widely used in a hinged structure such as a notebook computer or a foldable mobile phone, and the switch is frequently repeated. In this case, the wire arranging portion is wound into a spiral shape and housed in the hinge portion (Patent Document 1). Further, recently, a hinge portion structure corresponding to a more complicated operation has been proposed (Patent Document 2). Therefore, it is required to have a more flexible wiring structure. And generally, the force required for bending can be relatively small as compared with the case of the double-sided member, in the case where the one-sided member is a wire portion.

Therefore, when the wiring density is high, a single-sided material having a better bendability is formed into a two-piece structure, and the line portion is made hollow by the space therebetween. The bending stress is relieved (Patent Document 3). In the method described in the above, a single-sided flexible substrate is a two-layered substrate in which two single-sided flexible substrates are stacked. However, an example in which the outer layer material is overlapped to form a multilayer substrate is also known (Patent Document 4) ). In Patent Document 4, the inner layer (the second and third layers) of the four-layer substrate is pulled out from the wiring portion.

Conventionally, in a structure in which a two-layer substrate in which two single-sided flexible substrates are stacked, or a structure in which an inner layer of a multilayer substrate is pulled out, a two-piece structure is used as a single-sided material. Hollow cable line structure. In the case where the wiring portion is pulled out from the inner layer of the multilayer substrate, the relationship of the inner layer material formed by the circuit pattern formation is used, and there is no particular problem in circuit pattern formation.

However, in the structure in which the wire arranging portion is pulled out from the outer layer, for example, as shown in Fig. 7(a), the wire splicing portion cannot be pulled out from the first and fourth layers of the four-layer substrate. In other words, when the single-sided flexible substrate is provided as a two-layered substrate in which two sheets are stacked, patterning is performed after bonding the substrate material, but a step is formed between the hollow portion and the non-hollow portion. If the difference is too large, in the lithography method, a gap is formed between the material and the exposure mask, and the blur of the exposure image generated by the focus shift is caused by the blurring of the exposure, which may result in a thickening or short circuit of the circuit pattern. bad.

Generally, such exposure blurring can be avoided when the material and the exposure mask are within 50 μm, and when the single-sided flexible substrate is placed on two substrates which are overlapped by two sheets, the laminate or the pre-layer is laminated. If the prepreg is thinner than 50 μm, circuit pattern formation can be performed.

However, for example, in the case of a substrate constructed as shown in Fig. 7(a) As shown in Figure 7(b), deflection occurs. That is, as shown in Fig. 7(a), the outer layer core substrate 73 is laminated on the outer side of the inner core substrate via the laminated adhesive (or prepreg) 72, and the outer layer is When lamination is performed by laminating a copper sheet laminate 71 on one side, as shown in Fig. 7(b), deflection occurs in the wire arranging portion.

Therefore, when the wire portion is pulled out from the outer layer with the copper sheet laminate 71, even if such a thin material is selected, the step between the hollow portion and the portion other than the hollow portion cannot be made 50 μm or less. In the lithography process, a gap is formed between the material and the exposure mask, and based on the exposure blur, it is unavoidable that the circuit pattern becomes thick or short-circuited. Further, for example, as shown in Fig. 7(c), even when the outer layer is laminated on the one side with the copper sheet laminate 71 on one side, the deflection is similarly generated in the lithography process. Exposure blurring occurs based on the gap created between the material and the exposure mask.

In addition, when it is manufactured by a subtractive method, the circuit pattern in the wiring portion where the flexibility is required is formed with a plating layer formed when an interlayer conduction portion such as a through hole is formed, and when it is not plated, Brings the result of poor bending.

[Patent Document 1] Japanese Patent Laid-Open No. Hei 6-311216

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-133764

[Patent Document 3] Japanese Patent Laid-Open No. Hei 7-312469

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2003-133733

[Patent Document 5] Japanese Patent Publication No. Hei 2-65377

[Patent Document 6] Japanese Patent Laid-Open No. 61-58294

In the case of the structure in which the wire arranging portion is pulled out from the outer layer, for example, as in Patent Document 5, only the structure in which the flexible substrate is bonded to the flexible substrate is used, or as shown in the conventional example of Patent Document 6, The method of connecting a rigid substrate with a flexible substrate cannot be integrally formed.

The present invention has been made in view of the above problems, and an object thereof is to provide a method in which a multilayer substrate which is obtained by pulling out an outer layer portion of at least one surface of a multilayer substrate and connecting the component mounting portions.

In order to achieve the above object, the present invention is to form a circuit pattern of a layer wiring portion which is difficult to form a circuit after formation of a multilayer substrate before lamination. that is:

(1) forming, by the etching method, a circuit pattern of the flexible wiring portion and a flexible row on a copper foil laminated with a copper laminate on one side of the inner core substrate A connection pad portion is formed at a base end portion of the component mounting portion side of the line portion circuit pattern.

(2) The flexible wiring portion circuit pattern formed in the above-mentioned item (1) and the connection pad portion formed on the component mounting portion side base end portion of the circuit pattern, except for the connection pad portion A surface protective insulating film is formed outside a portion of the front end of the component mounting portion.

(3) at least one side of the inner core substrate, by In the outer connecting member, the outer connecting member of the flexible wiring portion is formed by laminating a single-sided copper sheet laminated sheet produced by the above-mentioned items (1) and (2) so that the copper foil faces outward. The integrated body forms an interlayer conduction portion at a desired position of the component mounting portion.

(4) a copper foil having a copper laminated plate on one side of the laminate formed in the above-mentioned item (3), the flexible wiring portion circuit pattern and the circuit pattern formed on the flexible wiring portion An outer layer circuit pattern is formed by etching by a portion other than the connection pad portion of the base end portion of the component mounting portion side.

(5) A surface protective insulating film having an opening at a desired position is formed on the outer layer circuit pattern including the connection pad portion.

A method for producing a multilayer flexible printed circuit board, characterized in that, through the above-mentioned items (1) to (5), a copper-clad laminate is attached to one side of at least one side of the inner core substrate, The flexible wiring portion between the component mounting portions that connect the plurality of parts is formed.

In the present invention, at least one surface of the inner core substrate is laminated, and not only the component construction portion but also a single layer of the flexible wiring portion is formed with a copper laminate. In the method for producing a multilayer flexible printed circuit board, it is possible to establish a circuit pattern in which a layer wiring portion which is conventionally difficult to form before the lamination is formed.

In addition, in the method of the present invention, the problem of miniaturization of the circuit pattern of the flexible wiring portion which is difficult to form the interlayer conduction portion such as a through hole by pannel plating is caused by the method of the present invention. In order to form a fine circuit pattern in advance, it is possible to etch only the thickness of the copper foil to which the copper laminated board material is attached, and it is an effective means for miniaturization.

Hereinafter, embodiments of the present invention will be described with reference to Figs. 1 to 6 .

[Embodiment 1]

Fig. 1 is a view showing the overall flow of the process of the method of the present invention, and Fig. 2 to Fig. 6 are views showing the formation process of the outer layer circuit pattern on the way of the project.

In the method of the present invention, a printed substrate is produced through the respective processes shown in Fig. 1. That is, the outer layer substrate is formed by steps S1 to S3, and the inner layer substrate is formed by step S4, and the two substrates are laminated by step S5 to form a multilayer substrate. Further, the multilayered substrate is processed by steps S6 to S10 to form an outer layer flexible printed substrate.

First, a copper laminated board is attached to one side (step S1), and a circuit pattern is formed only around the wiring portion (S2). Thereafter, a surface protective insulating film is formed only around the wiring portion (S3). On the other hand, the inner core substrate (S4) is separately formed, and in step S5, the multilayer substrate is formed by laminating the outer substrate and the inner substrate in addition to the adhesive member corresponding to the wiring portion.

Next, an interlayer conduction portion for interlayer connection is formed on the multilayer substrate (step S6), and after the outer layer circuit pattern is formed (step S7), a surface protective insulating film is formed (step S8). After that, apply shape processing (step S9), the multilayer flexible printed circuit board is completed (step S10).

Next, each project will be described based on FIGS. 2 to 6 .

First, as shown in Fig. 2, a copper laminated plate is attached to one surface of the component mounting portion 100 and the wire arranging portion 200, and a copper foil laminated with a copper laminated plate on one side thereof is used. Etching is performed to form the outer-layer circuit pattern of the wiring portion circuit pattern 1 and the subsequent component mounting portion. At this time, the connection pad portion 2 for connecting the outer layer circuit pattern of the wiring portion circuit pattern 1 and the component mounting portion is formed. The broken line portion of Fig. 2 is the connection pad 2.

The width 2a of the connection pad 2 is preferably set to be 0.05 mm or more wider than the line width 1a of the wire portion in consideration of the amount of exposure deviation in forming the outer layer circuit pattern of the component mounting portion of the post-engineering. Further, the length 2b of the connection pad 2 is based on the amount of exposure deviation when forming the outer layer circuit pattern of the component construction portion, and in order to obtain connection reliability, the outer layer circuit pattern of the component assembly portion is overlapped as will be described later. The exposure is preferably carried out, and it is preferable to use 0.5 mm or more in consideration of variations in the formation of the surface protective insulating film to be described later.

In this stage, a copper foil layer having a copper laminated plate on one side of the plating layer is formed into a circuit pattern, which is an etching of a copper foil layer which is thinner than the copper foil layer on which the plating layer is formed, and can be formed in the wiring portion. Fine circuit pattern. The circuit pattern can be formed by a usual etching process.

Next, as shown in Fig. 3(a), in the portion where the circuit pattern is formed in Fig. 2, a flexible insulating resin film such as polyimide or the like is bonded by an adhesive. At this time, when the surface protective insulating film 3 is displaced and the portion of the copper foil on the side of the component mounting portion 100 that is connected to the pad portion 2 is left, the post-work is performed. In the process, after forming the outer layer circuit pattern of the component mounting portion 100, the flexible insulating resin film is adhered from the etched portion to the near side portion in a relationship of short circuit.

Therefore, the shape of the A1-A1 cross section of the portion including the bonding pad 2 at this time is as shown in Fig. 3(b), and the shape of the A2-A2 cross section which does not include the portion to which the bonding pad 2 is attached is as As shown in Figure 3(c). Here, the 11-series outer layer is provided with a copper foil of a copper laminated board, and 4 is an insulating base material.

The distance g between the etched portion and the portion of the bonded cover layer 3 is preferably 0.1 to 0.3 mm in consideration of the deviation at the time of bonding.

Then, the circuit pattern and the connection pad described above are formed on the inner core substrate formed in advance, and the copper laminate laminate obtained by bonding the surface protection insulating film 3 is laminated to form a multilayer substrate. Then, an interlayer conduction portion such as a via hole or a via hole is formed. The projects so far have been carried out in the past. Here, a method of forming an interlayer conduction portion by subtraction and full-plate plating is assumed.

The fourth (a) figure is a state in which the image is exposed and developed using the dry film 5 after the whole plate is plated. Further, the portion 31 to which the surface protective insulating film 3 is attached in the prior art is a region 31. Further, although the wiring portion circuit pattern 1 is hidden by the full-plate electroplated copper foil 12, it is not visible, but it is conveniently displayed. The shape of the A3-A3 cross section including the portion of the bonding pad 2 at this time is as shown in Fig. 4(b).

In the fourth (b) diagram, in the portion of the dry film 5 where the bonding pad 2 is connected, only the portion of the length p overlaps with the portion covered by the covering layer 3, whereby The overlap is performed, and when the etching is performed later, the connection pad 2 is not broken. The overlap length p is preferably 0.07 mm or more in consideration of side etching during etching.

Fig. 5(a) shows a state in which the outer peripheral circuit pattern other than the connection pad 2 formed on the proximal end portion of the configuration portion side of the wiring portion circuit pattern 1 is formed by etching. The cross-sectional shape of the A4-A4 line including the portion where the bonding pad 2 is connected at this time is as shown in Fig. 5(b). By overlapping the length p, the circuit pattern 1 formed before the lamination is surely connected to the circuit pattern 13 formed later.

As shown in FIG. 5(b), the connection pad portion 2 is in a state in which the circuit pattern is protruded, and is easily subjected to an impact from the outside. Therefore, as shown in Fig. 6(a) and Fig. 6(b) showing the cut surface along the A5-A5 line, it is formed by printing of a flexible insulating film or solder resist. It is preferable to cover the connection pad portion 2 with the surface protective insulating film 6. The region 61 of Fig. 6(a) is a region covered by these surface protective insulating films 6.

[Application example]

The work (5) in the embodiment may be used instead of the surface protective insulating film, and the outer layer forming material may be used for build-up lamination. In this case, the substrate obtained in the works (1) to (4) in the examples is a new inner core substrate.

1‧‧‧Circuit circuit pattern

11‧‧‧Material copper foil with outer layer of copper laminated board

12‧‧‧Full plated copper foil

2‧‧‧Connecting pads

3‧‧‧Surface protection insulating film

31‧‧‧Attached area with surface protective insulating film

4‧‧‧Insulating substrate with a laminate of copper sheets

5‧‧‧Dry film after image exposure

6‧‧‧Surface protective insulating film

61‧‧‧A zone covered with a surface protective insulating film

71‧‧‧ Single-sided laminated copper sheet

72‧‧‧Subsequent components

73‧‧‧ Inner substrate

a‧‧‧Line department

b‧‧‧Parts Construction Department

G‧‧‧distance

P‧‧‧overlapping length

Fig. 1 is an explanatory view showing a series of works of one of the methods of the present invention.

Fig. 2 is a plan view showing a connecting portion of a component mounting portion and a wiring portion to which a printed circuit board of the present invention is applied.

Fig. 3(a) is an explanatory view showing a connection pad used in the present invention, and Fig. 3(b) is a sectional view taken along line A1-A1 in Fig. 3(a), 3(c) is a cross-sectional view taken along the line A2-A2 in the third (a) diagram.

Fig. 4(a) is an explanatory view showing a circuit pattern of a component mounting portion and a wiring portion connected by a connection pad formed in accordance with the present invention, and Fig. 4(b) is along the fourth (a) ) A cross-sectional view of the A3-A3 line in the figure.

Fig. 5(a) is an explanatory view showing a circuit pattern of a component mounting portion and a wiring portion connected by a connection pad formed in accordance with the present invention, and Fig. 5(b) is along the fifth (a) ) A cross-sectional view of the A4-A4 line in the figure.

Fig. 6(a) is an explanatory view showing a circuit pattern of a component mounting portion and a wiring portion connected by a connection pad formed in accordance with the present invention, and Fig. 6(b) is along the sixth (Fig. 6(b) a) A section of the line A5-A5 in the figure.

The seventh (a), (b), and (c) drawings are explanatory views showing the configuration of the conventional example and the deflection generated therefrom.

Claims (2)

A method for manufacturing a multilayer flexible printed circuit board is a multilayer flexible printed circuit board in which at least one side of an inner core substrate is laminated with a copper laminated plate on one side thereof, and a plurality of parts are arranged between the components. A method for manufacturing a multilayer flexible printed circuit board in which a flexible wiring portion extending from the component mounting portion is electrically connected is characterized in that: (1) a layer is formed by the following processes in sequence Forming a copper foil having a copper laminated plate on one side of the inner core substrate, and forming a circuit pattern of the flexible wiring portion and a circuit pattern of the flexible wiring portion by etching a connection pad portion is formed at a base end portion of the component portion; and (2) the flexible wire portion circuit pattern formed in the above-mentioned item (1) and a base portion of the component structure portion formed on the circuit pattern The connection pad portion is formed with a surface protective insulating film except for a portion of the front end of the connection pad portion on the component mounting portion side; and (3) at least one side of the inner core substrate is formed by In addition to the aforementioned flexible cable portion, the outer connecting member is made of copper. a layered body is laminated on one side of the above-mentioned items (1) and (2) to form a layered body, and an interlayer conduction portion is formed at a desired position of the part structure portion; And (4) a copper foil laminated with a copper laminate on one side formed by laminating the above-mentioned item (3), the flexible wiring portion circuit pattern and the circuit pattern formed on the flexible wiring portion a portion other than the connection pad portion of the base end portion of the component mounting portion side is formed by an etching method to form an outer layer circuit pattern; And (5) forming the surface protective insulating film having an opening at a desired position in the outer layer circuit pattern including the connection pad portion. The method for producing a multilayer flexible printed circuit board according to the first aspect of the invention, wherein in the above-mentioned item (5), the surface protective insulating film is replaced with a material for forming an outer layer, and the layered layer is laminated.