KR101201940B1 - Method for manufacturing multilayer wiring board having cable part - Google Patents

Abstract

The present invention provides a low cost and stable method for manufacturing a multilayer wiring board having a high integration density and a cable section capable of mounting a narrow pitch CSP. A method for producing a multilayer flexible wiring board having a cable section on at least one quasi-outer layer, the method comprising: a) manufacturing the inner core boards 8 and 58; b) conduction to the outer layer side in a flexible double-sided copper clad laminate. Forming an opening of the copper foil in the hole forming portion for forming the circuit, and forming a circuit pattern (10,60) including an opening in the through hole forming portion in the inner layer side of the double-sided copper clad laminate, c) a coverlay over the circuit pattern (22,70) to form an outer layer build-up layer (23,67), d) The outer layer build-up layer, with the coverlay formed side toward the inner layer core substrate, the adhesive material is applied to the inner layer core substrate Laminating through to form laminated circuit substrates (25, 73), e) the laminated circuit substrate is subjected to laser processing through the opening of the copper foil toward the through hole forming portion on the outer layer side, and a conductive tool A step of forming the yoke (26, 27, 28, 74, 75, 76), f) the opening of the copper foil toward the conductive hole forming portion on the outer layer side with respect to the laminated circuit substrate, and the circuit pattern Forming a hole for conduction by laser processing the opening of the through hole forming portion as a laser shielding mask, g) conducting treatment to the hole for conduction and conducting a via hole 29,30, 31,77,78,79) is a manufacturing method provided with the process of forming. The double-sided copper clad laminate may be replaced with a single-sided copper clad laminate.

Flexible Wiring Boards, Copper Clad Laminated Boards

Description

Manufacturing method of multilayer wiring board which has cable part {METHOD FOR MANUFACTURING MULTILAYER WIRING BOARD HAVING CABLE PART}

1 is a conceptual cross-sectional view showing a first embodiment of the present invention.

2 is a conceptual cross-sectional view showing the first embodiment of the present invention.

3 is a conceptual cross-sectional view showing the first embodiment of the present invention.

Figure 4 is a schematic cross-sectional view showing a first embodiment of the present invention.

5 is a schematic cross-sectional view showing the first embodiment of the present invention.

6 is a schematic cross-sectional view showing a second embodiment of the present invention.

7 is a schematic cross-sectional view showing a second embodiment of the present invention.

8 is a schematic cross-sectional view showing a second embodiment of the present invention.

9 is a schematic cross-sectional view showing a second embodiment of the present invention.

10 is a schematic cross-sectional view of a method for manufacturing a multilayer wiring board having a cable section according to the conventional method.

11 is a conceptual cross-sectional view of a method for manufacturing a multilayer wiring board having a cable section according to the conventional method.

12 is a schematic cross-sectional view of a method for manufacturing a multilayer wiring board having a cable section according to the conventional method.

13 is a schematic cross-sectional view of a method for manufacturing a multilayer wiring board having a cable section according to the conventional method.

14 is a schematic cross-sectional view of a method for manufacturing a multilayer wiring board having a cable section according to the conventional method.

15 is a schematic cross-sectional view of a method for manufacturing a multilayer wiring board having a cable section according to the conventional method.

** Description of Major Reference Codes **

1: copper foil 2: nickel foil

3: copper foil 4: metal base

5: conductive projection 6: prepreg

7: top of conductive protrusion

8: Circuit board through which conductive protrusion penetrates prepreg

9: metal foil 10: circuit pattern

11: double-sided core board 12: flexible insulating base material

13, 14: copper foil 15: double-sided copper clad laminate

16: resist layer 17: conformal mask

18: inner layer circuit including the opening of the hole-forming part for conduction

19: build up layer 20: polyimide film

21: adhesive 22: coverlay

23: Buildup layer with coverlay 24: Adhesive material

25: laminated circuit substrate 26: first through hole

27: second through hole 28: third through hole

29: via hole 30: stack via hole

31: skip via hole 32: laminated circuit board

33: outer circuit pattern 34: quasi-outer layer cable

35: multilayer wiring board having cable section according to the present invention

51: copper foil 52: nickel foil

53: copper foil 54: metal base

55: conductive protrusion 56: prepreg

57: top of the conductive protrusion

58: circuit board with conductive protrusions penetrating the prepreg

59: metal foil 60: circuit pattern

61: double-sided core board 62: flexible insulating base material

63: copper foil 64: one side copper clad laminate

65: resist layer

66: inner layer circuit including openings in the through hole-forming portion

67: build-up layer 68: polyimide film

69: adhesive 70: coverlay

71: build-up layer with coverlay 72: adhesive material

73: laminated circuit substrate 74: first through hole

75: second through hole 76: third through hole

77: via hole 78: stack via hole

79: skip via hole 80: outer circuit pattern

81: sub-layer cable

82: multilayer wiring board having cable section according to the present invention

131: flexible insulating base material 132, 133: copper foil layer

134: double-sided copper clad laminate 135: circuit pattern

136: inner layer circuit 137: polyimide film

138: adhesive 139: cover

140: cable portion 141: flexible insulating base material

142: copper foil layer 143: copper clad laminate

144: adhesive 145: one-sided copper clad laminate

146: through hole 147: through hole

148: circuit pattern 149: inner core board

150: adhesive insulating resin 151: conductive layer

152: one side copper clad laminate 153: perforated one side copper clad laminate

154: through hole 155: via hole

156: circuit pattern

157: multilayer wiring board having cable section according to conventional method

The present invention relates to a method for manufacturing a buildup type multilayer wiring board, and more particularly, to a method for manufacturing a buildup type multilayer flexible wiring board having a flexible cable part.

In recent years, miniaturization and high functionalization of electronic devices are increasingly promoted, and as a result, demand for higher density of wiring boards is increasing. Therefore, the wiring board is made to be a double-sided or multi-layered wiring board having three or more layers from one side, thereby increasing the density of the wiring board.

As a part thereof, a separate flexible wiring board or flexible flat cable which connects between a multilayer wiring board or a rigid wiring board on which various electronic devices are mounted, mainly through small electronic devices such as a mobile phone, is connected through a connector or the like. Multilayer flexible wiring boards having a flexible cable portion have been widely used (see, for example, FIG. 5 of Japanese Patent No. 2631287).

Among them, high-performance of mobile phones is noticeable, and accordingly, components mounted on multilayer flexible wiring boards are also changed to CSP (chip size package), and high-performance and high-density packaging are in a trend to provide high-performance without increasing board size. The pad pitch of this CSP was also 0.8 mm initially, and recently, there has been a demand for mounting a narrow pitch of 0.5 mm or less.

The following are the requirements for mounting a narrow pitch CSP on a multilayer flexible wiring board.

(a) There should be no through holes in the CSP mounting land.

  : This is to prevent the solder necessary for mounting from flowing.

(b) High density arrangement of conductive parts should be possible.

  : Pitch equal to the pad pitch of the CSP to be mounted as the minimum pitch required for connecting to the wiring layer below directly from the narrow pitch CSP mounting land.

(c) formation of fine wiring

  This is because wire drawing out from many pads of 100 pads or more is necessary regardless of the outer layer or the inner layer. In addition, the number of wires drawn out between the CSP mounting lands is an important factor in determining the specification of the mountable CSP. In particular, at the time of CSP mounting, it is effective to make the wiring of the inner layer below finer than the wiring of the outer layer in which the CSP mounting land exists.

(d) Flatness of CSP Mount Lands

  This is because, when flip chip mounting the CSP face down on the multilayer flexible wiring board, it is necessary to absorb the unevenness of the CSP mounting land at the height of the solder balls on the CSP side pads. In a multilayer flexible wiring board, it is necessary to fill the step by the thickness of the semiconductor of each layer with an adhesive or the like to ensure flatness.

The typical structure of a multilayer flexible wiring board is a four- to eight-layer layer having a double-sided or one-sided flexible wiring board as an inner layer, a flexible or rigid base wiring board as an outer layer, and a through-hole connection by plating or the like. The structure is a multilayer flexible wiring board having a degree of precision (see, for example, FIG. 5 of Japanese Patent No. 2631287).

However, the through-hole connection penetrates all the layers, which makes it difficult to increase the density, but there is a problem in that when the component mounting land is installed on the through hole, solder flows and the land cannot be placed on the through hole. For this reason, it is impossible to mount a narrow pitch CSP because the above-mentioned requirement of narrow pitch CSP is not satisfied.

Among them, it has been very difficult to mount a narrow pitch CSP in which CSP pads of 10 pads or more and 10 pads or more are arranged in a full grid, in a conventional multilayer flexible wiring board.

Therefore, in order to realize high-density mounting, build-up type multilayer flexible wiring boards having a multilayer flexible wiring board as a core board and having a buildup layer of about one or two layers on both sides or one side have also been put into practical use.

However, when building up a multilayer flexible core board, it is difficult to build up because a flexible component such as a cable part impairs the flatness of the core board. In addition, since through-hole plating is performed on the core substrate, the thickness of the conductor layer is increased, making it difficult to form a fine circuit.

In addition, since it is necessary to secure the flatness by filling the above-mentioned thick conductor layer with the build-up adhesive material, the required adhesive material thickness is increased, and the via-hole plating thickness of the build-up layer required for securing the connection reliability is also increased. There is a need. As a result, since the formation of the fine circuit is also difficult, it does not satisfy the requirements of the above-mentioned narrow pitch CSP mounting, and it is impossible to mount the narrow pitch CSP.

Therefore, in order to compensate for the lack of microcircuit forming ability by increasing the number of layers, a method of further building up the second stage has been proposed. However, in order to fabricate a two-stage build-up type multilayer flexible wiring board using this method, stacking is repeated several times. As the number of layers increases, the process becomes complicated and the yield decreases.

In addition, a method of stacking the first stage build-up layer by the conductive protrusion on the core substrate to ensure flatness and then building up the second stage can also be considered (see Japanese Patent Application Laid-Open No. 2003-129259, paragraphs 0020 to 0030). ).

However, when the conductive protrusion is brought into contact with the multilayer flexible core board made of a flexible component such as a cable part, the core board may be deformed or damage may be caused to the through hole of the core board. Due to this, the process is complicated and the yield is lowered, and thus the problem cannot be solved.

For this reason, there is a demand for a method of manufacturing a multilayer wiring board having a high integration density and a cable portion capable of mounting a narrow pitch CSP, at low cost and in a stable manner.

10 to 15 are cross-sectional process diagrams illustrating a conventional method for manufacturing a multilayer wiring board having a cable section (Japanese Patent Laid-Open No. 2004-20026, FIG. 3). First, as shown in FIG. What is called a double-sided copper clad laminated board 134 which has conductive layers 132 and 133, such as copper foil, on both surfaces of the flexible insulating base material 131, such as mead, is prepared.

Subsequently, as shown in FIG. 10 (2), the copper foil layers 132 and 133 of the double-sided copper clad laminate 134 are etched using a conventional photo fabrication method, such as a cable. The circuit pattern 135 is formed to be an inner layer circuit 136.

Subsequently, as shown in FIG. 10 (3), the cover 139 is formed by bonding the polyimide film 137 to the circuit pattern 135 such as a cable through the adhesive material 138 to form the cable part 140. To form.

Subsequently, as shown in FIG. 10 (4), what is called a one-sided copper clad laminated board 143 which has the conductive layer 142, such as copper foil, on one surface of the insulating base material 141, and this is shape | molded in a desired shape by a metal mold | die etc. The adhesive material 144 for bonding to the processed cable part 140 of FIG. 10 (3) is prepared.

As thickness of the conductive layer 142 at this time, 50 micrometers or less are possible, and 35 micrometers or less are preferable. Thereafter, as shown in FIG. 10 (5), the one-side copper clad laminate 143 and the adhesive material 144 are glued together, and this can be viewed in a desired shape by a mold or the like.

Subsequently, as shown in FIG. 11 (6), the one-sided copper clad laminate 145 of the bonded process of FIG. 10 (5) is laminated on the cable portion 140 of FIG. 10 (3) through the adhesive material 144. do. Subsequently, as shown in FIG. 11 (7), the conductive hole 146 is formed with an NC drill or the like.

At this time, the polyimide film 137 and the adhesive 138 of the inner layer cover 139 cause heat sag during the drilling process, and through-hole plating to the copper foil layers 132 and 133 of the inner layer circuit 136 is performed. Since adhesiveness deteriorates, a desmear process is performed. As diameter of the through hole 146, about 150-500 micrometers is preferable.

However, there is a correlation between the diameter of the through hole and the connection reliability (see Japanese Patent Application Laid-Open No. 2002-84069, paragraphs 0005 to 0008). If the diameter of the through hole is designed to be small in order to improve the degree of integration, It is known that the plating thickness required to secure the reliability becomes thick.

Subsequently, as shown in FIG. 12 (8), the through hole 147 is formed by electroplating after electroless plating or conduction treatment is performed on the through hole 146. As plating thickness of the through hole 147 at this time, about 30-50 micrometers is preferable in order to ensure reliability.

Thereafter, as shown in FIG. 12 (9), a circuit pattern 148 is formed on the through hole surface using an etching method by a conventional photofabrication method, and the cable of the build-up type multilayer flexible wiring board is formed. An inner core board 149 having a portion is obtained.

Subsequently, as shown in (10) of FIG. 13, copper foil or the like is formed on one surface of the adhesive insulating resin 150 with little leakage such as low flow type prepreg or bonding sheet. A so-called copper clad laminate 152 having a conductive layer 151 is prepared.

As the thickness of the adhesive insulating resin 150, since it is necessary to fill the conductor layer including the thick through-hole plating of Fig. 2 (8) and ensure flatness, a thickness of at least 50 µm or more is required, and here One 100 µm thick was used.

Subsequently, as shown in FIG. 13 (11), one surface copper clad laminated board 152 is bonded by a metal mold | die or the like. Subsequently, as shown in FIG. 13 (12), the one-sided copper clad laminated board 153, which has been subjected to the bonding process, is laminated on the inner layer core substrate 149 obtained in FIG.

Thereafter, as shown in FIG. 14 (13), the conductive hole 154 is formed by a laser or the like. As the diameter of the through hole 154, about 100-300 micrometers is preferable in order to mount the narrow pitch CSP of 0.5 mm pitch or less.

However, as mentioned above, when the diameter of the through hole is designed to be small, the thickness of the plating required for securing reliability is increased. On the other hand, when the hole diameter is designed to be large, not only the degree of integration decreases, but also the processing time required for laser processing increases, which leads to deterioration in productivity.

Subsequently, as shown in FIG. 14 (14), the via hole 155 is formed by electroplating after electroconductive plating or conduction treatment is performed on the through hole 154. Considering the thickness of the adhesive insulating resin 150, the plating thickness of the via hole 155 at this time also depends on the diameter of the via hole 155, but in order to ensure reliability, 30 mu m or more is preferable.

Thereafter, as shown in FIG. 15 (15), the circuit pattern 156 is formed on the outermost conductive layer including the plated metal layer surface by using an etching method by a conventional photofabrication method. .

Subsequently, if necessary, the surface of the substrate is subjected to surface treatment such as formation of a photo solder resist layer, soldering, nickel plating, gold plating, and the like, and externally processed to obtain a multilayer wiring substrate 157 having a cable portion.

As such, since the thickness of the through hole plating and the via hole plating needs to be thickened, the thickness of the first and second conductor layers from the outside of the six layers becomes thicker, and as a result, it is difficult to form fine wiring of these layers. This results in lowering the degree of integration and lowering the yield. For this reason, the narrow-pitch CSP of the full-grip with a large number of grips cannot be mounted, and there exists a problem that it becomes the board | substrate specification with low freedom.

Although not shown, a two-stage build-up is possible by repeating the process from FIG. 13 (10), and the degree of freedom of the specification of the narrow-pitch CSP that can mount the multilayer flexible substrate thus obtained increases, but also outside Since the thickness of the first and second conductor layers from the side becomes thicker, it is difficult to form fine lines of these layers. Moreover, since the lamination is repeated as described above, the process becomes more complicated as the number of layers increases, which causes a problem that the yield falls.

As described above, a problem in manufacturing a multilayer wiring board having a high directivity and a cable section capable of mounting a narrow pitch CSP by using a conventional manufacturing method is that the complicated perforated plating is required several times. It is mentioned that there is a problem in yield, and there are many wiring layers that increase the thickness of the plating, so that it is difficult to form a fine circuit, so that the build density of several stages is inevitably lowered.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and an object of the present invention is to provide a method for manufacturing a multilayer wiring board having a high integration density and a cable portion capable of mounting a narrow pitch CSP, at low cost and in a stable manner.

In order to achieve the above object, the present invention provides each of the following inventions.

According to the first invention,

In the manufacturing method of the multilayer flexible wiring board which has a cable part in at least one quasi outer layer, and a through hole in a CPS mounting land,

a) a process for manufacturing the inner core board,

b) forming a circuit pattern including an opening of the copper foil in the conductive hole forming portion on the outer side of the flexible double-sided copper clad laminate, and an opening of the conductive hole forming portion in the inner layer of the double-sided copper clad laminate; fair,

c) forming a coverlay on the circuit pattern to form an outer layer buildup layer,

d) forming a laminated circuit substrate by directing the side on which the coverlay is formed toward the inner core board, and laminating the outer layer build-up layer on the inner core board through an adhesive;

e) laser-processing the said laminated circuit base material using the opening of the said copper foil toward the conduction hole formation site of the said outer layer, and the opening of the said conduction hole formation site in the said circuit pattern as a laser shielding mask, Forming a hole for conduction,

delete

f) a step of conducting a conductive process on the conductive hole and electroplating to form a via hole

And a control unit.

Furthermore, according to the second invention,

In the manufacturing method of the multilayer flexible wiring board which has a cable part in at least one quasi-outer layer, and a through hole in a CPS mounting land,

a) a process for manufacturing the inner core board,

b) forming a circuit pattern including an opening in the hole-forming portion for conducting in the copper foil layer of the flexible single-sided copper clad laminate;

c) forming a coverlay on the circuit pattern to form an outer layer buildup layer,

d) forming a laminated circuit substrate by directing the side on which the coverlay is formed toward the inner core board, and laminating the outer layer build-up layer on the inner core board through an adhesive;

e) A process of forming a through hole with respect to the laminated circuit substrate by laser processing the opening of the through hole forming portion on the outer layer side and the through hole forming portion in the circuit pattern as a laser shielding mask. ,

delete

f) a step of conducting a conductive process on the conductive hole and electroplating to form a via hole

And a control unit.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 9.

(Example 1)

1 to 5 are cross-sectional process charts showing the first embodiment of the present invention, and as shown in FIG. 1 (1), the copper foil 1 (for example, thickness 100 at the time of manufacture of a double-sided flexible wiring board) is shown. A metal substrate 4 having a three-layer structure of (micrometer) / nickel foil (2) (for example, 2 micrometers in thickness) / copper foil 3 (for example, 1 micrometer in thickness) is prepared.

Next, as shown to Fig.1 (2), the electroconductive protrusion 5 is formed on the copper foil 3 by the selective etching method. As etching liquid at this time, about 80-90% of the total thickness of the copper foil 1 is etched using the etching liquid used in a normal copper etching process, for example, etching liquid containing cupric chloride, and then nickel Using a etching solution that selectively etches copper, for example, an alkaline etching solution containing ammonia, to etch away the remaining portion of the copper foil 1 to expose nickel foil, and subsequently to a low corrosion resistance to copper The exposed nickel foil 2 is etched away using an etching solution for selectively etching nickel, for example, an etching solution containing hydrogen peroxide or nitric acid. Thereby, the structure shown in FIG. 1 (2) can be obtained.

Subsequently, as shown in Fig. 1 (3), the prepreg 6 in the B-stage state is attached to the surface on which the conductive protrusions are provided with a press, a laminate, or the like. Instead of the prepreg 6, an insulating resin having adhesiveness such as a polyimide film having thermoplastic polyimide on both sides may be used. As shown in FIG. 1 (4), in order to expose the top portion 7 of the conductive protrusion from the prepreg 6, mechanical polishing such as roll polishing, chemical polishing such as CMP, and the like are performed. By the process so far, the circuit substrate 8 in which the conductive protrusion 5 penetrates the prepreg 6 is obtained.

Subsequently, as shown in FIG. 1 (5), the circuit substrate 8, through which the conductive protrusions 5 penetrate the prepreg 6, is laminated on the metal foil 9. Here, the prepreg 6 is completely thermosetted and it will be in a C stage state. Subsequently, as shown in FIG. 1 (6), the circuit pattern 10 is formed on the copper foil of the laminated base material, and the filled-via structure used as a core board of a multilayer wiring board by the process up to here is provided. A double-sided core substrate 11 is obtained.

As in the first embodiment, in the case of a double-sided core substrate having interlayer conduction by conductive protrusions, there is no need to increase the thickness of the plating, and the thickness of the wiring layer of the core substrate can be reduced, so that the wiring can be miniaturized. Moreover, about the adhesive material used for adhesion | attachment with a subsequent buildup layer, since it can fill with a thin thickness, the outflow amount becomes small. And since the interlayer connection distance with a buildup layer becomes short, connection reliability improves comparatively when it is the same plating thickness.

The field via structure can be applied in various ways, and not only the metal conductive protrusions formed by the etching process, but also the conductive protrusions formed by printing the metal conductive protrusions, the conductive paste and the ink by the plating method, and the inner walls during the via hole plating. It is possible to apply, including a double-sided core substrate manufactured by via filling plating with increased plating precipitation, and a combination of these.

Furthermore, since the core substrate has a field via structure, it is possible to have a structure that is stacked on the field via when built up in the next step, which is advantageous for high density. In addition, the effect of reducing the reflection of the connecting portion during high-speed signal transmission can also be expected.

Then, as shown to (7) of FIG. 2, what is called double-sided copper field which has the copper foils 13 and 14 of thickness 12micrometer on the both sides of the flexible insulating base material 12 (here, polyimide of thickness 25micrometer). The laminated board 15 is prepared. The material and thickness of the flexible insulating base material 12 are not limited to 25 micrometers polyimide, According to a use, it can divide and use. For example, in applications where it is necessary to reduce the dielectric loss in high-speed signal transmission, a double-sided copper clad laminate based on a low-k dielectric liquid crystal polymer or the like can be used, and a polyimide film can be used for high refractive index requirements. A thin one, such as 12.5 micrometers, can be selected.

Subsequently, as shown in (8) of FIG. 2, the inner layer which includes the opening of the hole formation site | part for conduction in the conformal mask and copper foil 14 at the time of laser processing of the copper foil 13 of the double-sided copper clad laminated board 15 is carried out. The resist layer 16 for forming a circuit pattern by the photofabrication method is formed on both surfaces of the double-sided copper clad laminate 15. At this time, since the positioning of both surfaces is performed with respect to the whole material, positioning accuracy can be easily ensured without being influenced by expansion and contraction of a material. If necessary, it is also possible to use an exposure machine capable of high-precision alignment.

In addition, the thickness of the copper foils 13 and 14 is preferably about 5 to 12 μm, and within this thickness range, fine wiring having an inner layer pitch of 100 μm or less necessary for mounting the narrow pitch CSP can be formed, and then laser processing. It also functions as a laser light shielding mask in the city. In addition, since the coverlay adhesive material can be charged after securing flatness with a thin thickness, the connection distance between layers with a buildup layer becomes short, and when the plating thickness is the same, connection reliability improves relatively.

Subsequently, as shown in FIG. 2 (9), an inner layer circuit including the conformal mask 17 and the openings of the conductive hole forming portions at the time of laser processing by the photofabrication method using the resist layer 16 are used. The pattern 18 is formed and the resist layer is peeled off again. As needed, the roughening process is improved in order to improve adhesiveness with a buildup adhesive material.

On the other hand, when blind-via holes are formed on the conductive protrusions, blackening treatment or blackening reduction is performed to facilitate inspection of the conductive holes formed by the laser or the like after the build-up, or to mitigate the effects of laser heat. Roughening by etching with acid is preferred rather than treatment. The buildup layer 19 of the multilayer wiring board is obtained by the above processes.

Then, as shown to (10) of FIG. 2, the so-called coverlay 22 which has the adhesive material 21, such as acrylic and epoxy of 15 micrometers thickness, on the polyimide film 20 of 12 micrometers thickness, for example. Prepare.

Subsequently, as shown in FIG. 2 (11), the coverlay 22 is attached to the inner layer side of the buildup layer 19 of the multilayer wiring board by a vacuum press, a laminate or the like. The cover-up buildup layer 23 is obtained by the processes so far. On the other hand, the process of Fig. 2 (7) to (11) can be roll-to-roll (roll-to-roll) method, it can be expected that the productivity is further improved.

Thereafter, as shown in Fig. 3 (12), the adhesive material 24 for building up the buildup layer 23 with the coverlay onto the double-sided core substrate 11 is previously modeled and positioned. As the adhesive material 24, those having a low flow rate such as a low flow type prepreg or a bonding sheet are preferable. As for the thickness of the adhesive material 24, even if it considers filling property and flatness, a thin thing of 15-20 micrometers can be selected.

Subsequently, as shown in FIG. 3 (13), the buildup layer 23 with coverlay and the double-sided core substrate 11 are laminated by a vacuum press or the like through the adhesive material 24. The laminated circuit board 25 is obtained by the process so far.

Next, as shown to Fig.4 (14), it laser-processes using the conformal mask 17 at the time of the laser processing previously manufactured, and forms three types of conduction holes 26,27,28. When forming the 2nd conductive hole 27, the laser processing is performed using the opening of the conductive hole formation site of the circuit pattern 18 previously prepared as a laser shielding mask at the time of laser processing. For laser processing, UV-YAG laser, carbonic acid laser, excimer laser, etc. are selected and used.

The diameter of each conduction hole was set as follows. First, when the first conductive hole 26 is made of a polyimide having a thickness of 25 μm for the flexible insulating base material 12, a diameter of 50 μm can be manufactured, and the required plating thickness for securing reliability is about 10 μm. Therefore, the diameter was set to 50 µm here.

The second and third conductive holes 27 and 28 have problems of integration degree and interlayer connection reliability. In the first embodiment, the thickness of the conductor layer is from the second layer (the quasi-outer layer) to the fifth layer among the six conductor layers. There is no need for plating leading to an increase in the thickness of the conductor layer. For this reason, the thickness of the adhesive material 21 and the adhesive material 24 required for filling can be made thin, and reliability can be ensured even with comparatively thin plating thickness. As the hole diameter which can ensure the reliability about 15-20 micrometers of plating thickness, in the 2nd through hole 27, the diameter of a lower hole is 150 micrometers, and the diameter of an upper hole is considered the lower hole in consideration of alignment with a lower hole. It was set to 200 micrometers which added 50 micrometers to the diameter of a hole, and set it to 150 micrometers of hole diameters in the 3rd through hole 28. As shown in FIG. As a result, the degree of integration can be improved while enabling fine wiring to be formed, and all the through holes can be formed at a narrow pitch.

Moreover, the desmear process and electroconductive process for interlayer connection are performed by electroplating. On the other hand, in addition to the process using a conformal mask as mentioned above, the laser processing can also apply the large window method which laser-processes by offsetting a copper mask larger than the beam diameter of a laser previously. Of course, the direct laser method which penetrates copper foil and resin directly with a laser beam can also be applied.

Moreover, you may combine the process using the said conformal mask with the large window method and the direct laser method. On the other hand, when using the direct laser method, it is preferable that the thickness of copper foil is 20 micrometers or less.

Subsequently, as shown in Fig. 4 (15), the laminated circuit substrate 25 having the conductive holes 26, 27, and 28 is subjected to electroplating on the order of 15 to 20 µm and interlayer conduction is performed. In the conventional process, that is, one laser machining and plating process, the vias 29 obtained by the first through holes 26 and the stack vias 30 obtained by the second through holes 27 and the first through holes 26 are obtained. It is possible to form the skip via 31 obtained by the through hole 26 at once, and to obtain all interlayer conduction from the outer layer to the inner layer.

By the above processes, the laminated circuit base 32 in which interlayer conduction was completed is obtained. In addition, in the case where mounting holes such as insert parts and the like are required, through holes may be formed by NC drill or the like at the time of forming the through hole, and through holes may be simultaneously formed when plating the via holes.

Subsequently, as shown in Fig. 5 (16), the pattern 33 of the outer layer is formed by a normal photofabrication method. At this time, if there is a plating layer deposited on the cover film 20 located on the inner layer side of the buildup layer 23, this is also removed. Thereafter, if necessary, the surface of the substrate is subjected to surface treatment such as solder plating, nickel plating, and gold plating, to form a photosolder resist layer, and a shield layer toward the outer layer of the cable is formed using silver paste, film, or the like. By performing the external processing, the multilayer wiring board 35 having the cable section 34 in the outer layer is obtained.

In the multilayer wiring board having the cable section according to the first embodiment, since the cables are arranged in the second layer, which is a quasi-external layer without a plating layer, vias 29 having a diameter of 50 µm can be arranged at a pitch of 0.3 mm or less. Fine wiring with a pitch of 100 µm or less is possible. For this reason, it is possible to provide a method for producing a multi-layered wiring board having a cable section on which a narrow pitch CSP can be mounted at low cost and stably. In addition, there is no through hole in the CSP mounting land, thereby ensuring sufficient flatness of CSP mounting.

As described above, most of the wiring wound from the CSP to the cable can be processed in the first layer and the second layer (quasi-external layer), so that the third layer and the fourth layer serve as power sources and ground layers.

In the present invention, the third and fourth layers are connected by conductive projections, and the diameter of the conductive projections can be arbitrarily changed, for example, to secure the current capacity to the power supply, match the characteristic impedance, and adjust the signal at the connection portion. The optimum diameter for reflection suppression and other design factors may be considered.

(Example 2)

6 to 9 are cross-sectional process charts showing the second embodiment of the present invention. First, as shown in FIG. 6 (1), the copper foil 51 (for example, thickness at the time of manufacture of the double-sided flexible wiring board) is shown. A metal base 54 having a three-layer structure of 100 µm) / nickel foil 52 (for example, 2 µm thick) / copper foil 53 (for example, 12 µm thick) is prepared.

Next, as shown to Fig.6 (2), the electroconductive protrusion 55 is formed on the copper foil 53 by the selective etching method. As the etchant at this time, first, about 80 to 90% of the total thickness of the copper foil 1 is etched using an etchant used in a normal copper etching process, for example, an etchant containing cupric chloride. Using a etchant which selectively etches copper, for example an alkaline etchant comprising ammonia, to etch away the remaining portions of copper foil 1 and expose nickel foil, and then to Using the etching solution for selectively etching nickel, for example, an etching solution containing hydrogen peroxide or nitric acid, the exposed nickel foil 2 is etched away to have a structure shown in FIG. 6 (2).

Subsequently, as shown in Fig. 6 (3), the prepreg 6 in the B stage state is attached to the surface on which the conductive protrusions are provided with a press, a laminate, or the like. Instead of the prepreg 56, insulating resin with adhesiveness, such as a polyimide film which has thermoplastic polyimide on both surfaces, can also be used.

Next, as shown in FIG. 6 (4), in order to expose the top portion 57 of the conductive protrusion from the prepreg 56, mechanical polishing such as roll polishing, chemical polishing such as CMP, and the like are performed.

By the process so far, the circuit substrate 58 through which the conductive protrusion 55 penetrates the prepreg 56 is obtained.

Subsequently, as shown in FIG. 6 (5), the circuit substrate 58 having the conductive protrusion 55 penetrated through the prepreg 56 is laminated on the metal foil 59. Here, the prepreg 56 is completely thermosetted, and it will be in a C stage state.

Then, as shown in FIG. 6 (6), the circuit pattern 60 is formed in the copper foil of the laminated base material, and the double-sided core board which has the field via structure which becomes the core board of a multilayer wiring board by the process to here. Get 61.

As in the second embodiment, in the case of a double-sided core substrate having interlayer conduction by conductive projections, the thickness of the wiring layer of the core substrate can be reduced because the plating is not required to be thick, so that the wiring can be miniaturized. In addition, the adhesive used for bonding to the subsequent build-up layer can be filled with a thin thickness so that the amount of outflow is reduced or the distance between layers with the build-up layer is shortened. Reliability is improved.

The field via structure includes not only metal conductive protrusions formed by etching, but also conductive protrusions formed by printing metal conductive protrusions, conductive paste inks and the like by the plating method, and vias having increased plating precipitation to the inner wall during via hole plating. It can be applied including a double-sided core substrate manufactured by peel plating and a combination of these. In addition, since the core substrate has a field via structure, the core substrate can be stacked on the field via when built up in the next step, which is advantageous for high density. In addition, the effect of reducing the reflection of the connecting portion during high-speed signal transmission can also be expected.

Subsequently, as shown in FIG. 7 (7), a so-called one-sided copper clad laminate 64 having a copper foil 63 having a thickness of 12 µm on one surface of the flexible insulating base material 62 (polyimide having a thickness of 25 µm in this case). Prepare. The material and thickness of the flexible insulating base material 62 are not limited to 25 micrometers polyimide, It can divide and use according to a use.

For example, in applications where it is necessary to reduce dielectric loss during high-speed signal transmission, a double-sided copper clad laminate based on a liquid crystal polymer having a low dielectric loss tangent can be used, and a film thickness of polyimide is set to 12.5 for high refractive index requirements. It may be selected to be thin, such as μm.

Subsequently, as shown in FIG. 7 (8), a resist layer 65 for forming an inner circuit pattern on the copper foil 63 of the one-side copper-clad laminate 64 by the photofabrication method is formed. On one side of). As for the thickness of the copper foil 63, about 5-12 micrometers is preferable, and if it is the range of this thickness, the fine wiring formation of the inner-layer pitch of 100 micrometers or less required for narrow pitch CSP mounting is possible, and the mask for laser shading at the time of next laser processing It also functions as.

In addition, since the coverlay adhesive material can be charged after securing flatness with a thin thickness, the connection distance between layers with a buildup layer becomes short, and connection reliability improves relatively, when it is the same plating thickness.

Subsequently, as shown in FIG. 7 (9), the resist layer 65 is used to form a circuit pattern 66 including an opening in the through hole forming portion by the photofabrication method, and the resist layer is again formed. Peel off. As needed, the roughening process for improving the adhesiveness with a buildup adhesive material is performed.

On the other hand, if a blind via hole is formed on the conductive protrusion, an acid rather than a blackening treatment or a blackening reduction treatment is used to facilitate the inspection of the conductive holes formed by the laser or the like after the buildup, or to mitigate the effects of the laser heat. Roughening by etching is preferred. By the above processes, the buildup layer 67 of the multilayer wiring board is obtained.

Then, as shown to (10) of FIG. 7, the so-called coverlay 70 which has the adhesive material 69, such as acrylic and epoxy of 15 micrometers thickness, on the 12-micrometer-thick polyimide film 68, for example. Prepare.

Subsequently, as shown in FIG. 7 (11), the coverlay 70 is attached to the inner layer side of the buildup layer 67 of the multilayer wiring board by a vacuum press, a laminate or the like. By the process so far, the buildup layer 71 with a coverlay is obtained. On the other hand, the process of (7)-(11) of FIG. 7 can be performed by a roll-to-roll method, and it can expect that productivity improves further by this.

Subsequently, as shown in FIG. 8 (12), the adhesive material 72 for building up the buildup layer 71 with a coverlay to the double-sided core board | substrate 61 is previously modeled, and the position is set. It is preferable that the adhesive material 72 has a small flow rate such as a low flow type prepreg or a bonding sheet. The thickness of the adhesive material 72 may be selected as thin as 15 ~ 20㎛ even in consideration of filling and flatness.

Subsequently, as shown in FIG. 8 (13), the buildup layer 71 with coverlay and the double-sided core substrate 61 are laminated by a vacuum press or the like through the adhesive material 72. As shown in FIG. The laminated circuit board 73 is obtained by the process so far.

Thereafter, as shown in Fig. 9 (14), the laser processing is performed at the position which becomes a through hole, and three kinds of through holes 74, 75, and 76 are formed. When forming the second conductive hole 75, laser processing is performed by using the opening of the conductive hole formation portion of the circuit pattern 66 prepared in advance as a laser shielding mask during laser processing. As the laser processing method, a UV-YAG laser, a carbonic acid laser, an excimer laser, or the like can be selected. The diameter of each conduction hole was set as follows. First, when the first conductive hole 74 is made of a polyimide having a thickness of 25 μm for the flexible insulating base material 62, a diameter of 50 μm can be manufactured, and the required plating thickness for securing reliability is about 10 μm. For this reason, it was set to 50 micrometers in diameter here.

The second and third conductive holes 75 and 76 have a problem of integration degree and interlayer connection reliability. In this embodiment 2, plating of the sixth conductor layer among the second to fifth layers leads to an increase in the conductor layer thickness. Since the conductor layer can be made thin, the thickness of the adhesive material 69 and the adhesive material 72 required for filling can be reduced, and reliability can be ensured even with a relatively thin plating thickness.

As the hole diameter which can ensure the reliability about 15-20 micrometers of plating thickness, in the 2nd through hole 75, the lower hole diameter is 150 micrometers, and the upper hole diameter considers alignment with a lower hole diameter, and considers a lower hole diameter. Was added to 50 µm and 200 µm. In the third conductive hole 76, the diameter was 150 µm. For this reason, while making it possible to form fine wirings, the degree of integration is also improved, and all the through holes can be formed at a narrow pitch.

Moreover, the desmear process and electroconductive process for obtaining interlayer connection by electroplating are performed. On the other hand, in addition to the process using a conformal mask as mentioned above, the laser processing can also use the direct laser method which penetrates copper foil and resin directly with a laser beam.

Moreover, you may combine the process using the said conformal mask and the direct laser method. On the other hand, when using the direct laser method, it is preferable that the thickness of copper foil is 20 micrometers or less.

Subsequently, as shown in Fig. 9 (15), the laminated circuit substrate 73 having the conductive holes 74, 75, and 76 is subjected to electroplating on the order of 15 to 20 mu m and interlayer conduction is obtained. The via 77 obtained by the 1st through hole 74, the stack via 78 obtained by the 2nd through hole 75, and the 3rd process by the past process, ie, a single laser processing and plating process, are carried out. It is possible to form the skip via 79 obtained by the through hole 76 at once, and to obtain all interlayer conduction from the outer layer to the inner layer.

In addition, in the case where mounting holes such as insert parts and the like are required, through holes may be formed by NC drill or the like at the time of forming the through hole, and through holes may be simultaneously formed when plating the via holes.

After the conductive treatment, a plating resist layer such as a dry film resist is formed by a conventional photofabrication method, a via hole and an outer layer pattern are formed by plating, and a so-called semi-additive which removes the conductive coating film. The interlayer conduction can be obtained by an additive method, and the circuit pattern 80 can be formed finely, so that a narrow pitch CSP can be mounted with more grips than in the first embodiment.

On the other hand, as a method of forming an outer layer pattern, it is also possible to make via-hole plating mentioned above into panel plating, and to form by a normal photofabrication method after that. At this time, if there is a plating layer deposited on the cover film 68 located on the inner layer side of the buildup layer 71, this is also removed.

Thereafter, if necessary, the surface of the substrate is subjected to surface treatment such as solder plating, nickel plating, and gold plating, to form a photosolder resist layer, and a shield layer toward the outer layer of the cable is formed using silver paste, film, or the like. By performing the external processing, a multilayer wiring board 82 having a cable portion 81 on the outer layer side is obtained.

In the multilayer wiring board having the cable section according to the second embodiment, since the cables are arranged in the quasi-outer layer (second layer) without the plating layer, the vias can be arranged at a narrow pitch and fine wiring can be formed. A multilayer wiring board having a cable section capable of mounting a pitch CSP can be manufactured at low cost and stably. In addition, there is no through hole in the CSP mounting land to ensure sufficient flatness of CSP mounting.

As described above, since most of the wiring wound from the CSP to the cable can be processed in the first layer and the second layer (quasi-external layer), the third layer and the fourth layer have a power source and a ground layer. do. In the present invention, the third and fourth layers are connected by conductive projections, and the diameter of the conductive projections can be arbitrarily changed, for example, in order to ensure a current capacity for the power supply, and to match the characteristic impedance and the connection portion. The optimum diameter for the reflection suppression of the signal can be selected in consideration of other design factors.

The present invention has the following effects by the above-described features.

According to the first invention, since the multilayer circuit board using the double-sided copper-clad laminate is connected between layers by conductive projections, the interlayer connection due to the increase in the thickness of the plating, which causes a decrease in wiring density, becomes unnecessary on the inner core board, and thus the first layer Vias connecting the second layer, which is the semi-outer layer, can be arranged at a narrow pitch, and the wiring of the quasi-outer layer can be made fine, thereby ensuring reliability. In addition, there is no through hole in the CSP mounting land, and the flatness that can be mounted by CSP is sufficiently secured.

Further, according to the second invention, since the multilayer circuit board using the one-side copper-clad laminate is connected between layers by conductive projections, the interlayer connection due to the increase in the thickness of the plating, which causes a decrease in wiring density, becomes unnecessary on the inner core board, and the outer layer The circuit pattern can be formed more finely than in the first invention, and a narrow pitch CSP with a larger number of grips can be mounted.

In addition, the laser shielding mask and the inner circuit pattern of the inner and outer layers of the outer layer build-up layer are simultaneously processed and laminated on the inner core board, and then all interlayer conduction holes of the six-layer substrate can be formed by one laser processing. Since a process is also once, productivity is high and a yield is high.

In addition, since only the outermost layer is required to increase the thickness of the plating leading to a decrease in wiring density, fine wiring can be formed in all other layers. In addition, since the core substrate and the buildup layer can be manufactured separately, the productivity is further improved.

As a result, according to the present invention, it is possible to provide a method for manufacturing a multi-layered wiring board having a higher integration degree than a conventional manufacturing method and having a cable portion on which a narrow pitch CSP can be mounted, at low cost.

Claims (4)

In the manufacturing method of the multilayer flexible wiring board which has a cable part in at least one quasi-outer layer, and a through hole in a CPS mounting land, a) a process for manufacturing the inner core board, b) forming a circuit pattern including an opening of the copper foil in the conductive hole forming portion on the outer side of the flexible double-sided copper clad laminate, and an opening of the conductive hole forming portion in the inner layer of the double-sided copper clad laminate; fair, c) forming a coverlay on the circuit pattern to form an outer layer buildup layer, d) forming a laminated circuit substrate by directing the side on which the coverlay is formed toward the inner core board, and laminating the outer layer build-up layer on the inner core board through an adhesive; e) Laser processing is carried out with respect to the said laminated circuit base material using the opening of the said copper foil and the opening of the said through hole formation site in the said circuit pattern as a laser shielding mask toward the through hole forming site on the outer side. Process of forming dragon holes, f) a step of conducting a conductive process on the conductive hole and electroplating to form a via hole A method for manufacturing a multilayer flexible wiring board having a cable section on at least one quasi-outer layer, comprising: The method of claim 1, And the inner layer core board is a double-sided wiring board having interlayer connection by a field via structure. In the manufacturing method of the multilayer flexible wiring board which has a cable part in at least one quasi-outer layer, and a through hole in a CPS mounting land, a) a process for manufacturing the inner core board, b) a step of forming a circuit pattern including an opening in a hole-forming portion for conducting in a copper foil layer of a flexible one-sided copper clad laminate, c) forming a coverlay on the circuit pattern to form an outer layer buildup layer, d) forming a laminated circuit substrate by directing the side on which the coverlay is formed toward the inner core board, and laminating the outer layer build-up layer on the inner core board through an adhesive; e) A process of forming a through hole with respect to the laminated circuit substrate by laser processing the opening of the through hole forming portion on the outer layer side and the through hole forming portion in the circuit pattern as a laser shielding mask. , f) a step of conducting a conductive process on the conductive hole and electroplating to form a via hole A method for manufacturing a multilayer flexible wiring board having a cable section on at least one quasi-outer layer, comprising: The method of claim 3, wherein And the inner layer core board is a double-sided wiring board having interlayer connection by a field via structure.

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