KR101170764B1 - Method for manufacturing Multi-layer circuit board - Google Patents

Abstract

The present invention provides a multilayer circuit board capable of forming a fine and high-density circuit and at the same time provides a method for manufacturing such a multilayer circuit board at low cost and stably. In the multilayer circuit board which is laminated and connected by the interlayer connection hole, the thickness of the conductor constituting the receiving land 6 of the interlayer connection hole provided in the inner layer core substrate is the inner layer core except the interlayer connection hole portion. A multilayer circuit board and a method for manufacturing the same are characterized in that they are thicker than the thickness of the conductor of the wiring pattern of the board.

Multilayer circuit board

Description

Method for manufacturing Multi-layer circuit board

1 is a cross-sectional view showing the structure of a multilayer circuit board according to Embodiment 1 of the present invention.

2 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to the first embodiment of the present invention.

3 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to the first embodiment of the present invention.

4 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to the first embodiment of the present invention.

5 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to a conventional method.

6 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to a conventional method.

7 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to a conventional method.

** Description of Major Reference Codes **

1: flexible insulation base material 2, 3: copper foil

4: interlayer connection hole 5: receiving land forming portion

6: Resist layer for partial plating 7: Electrolytic plating film

8: Through Hole Land 9: Wiring Pattern

10: land receiving part 11: polyimide film

12: Adhesive 13: Coverlay

14: double-sided core board 15: flexible insulating base material

16: opening 17: conformal mask

18: adhesive 19: interlayer connection hole

20: electroplated coating 21: pattern of the outer layer

22: fusible cable section

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buildup type multilayer circuit board and a method for manufacturing the same, and more particularly, to a multilayer circuit board for miniaturizing a buildup layer wiring pattern and a method for manufacturing the same.

In recent years, miniaturization and high functionalization of electronic devices have been increasingly promoted, thereby increasing the demand for higher density of circuit boards.

Therefore, in order to realize high-density mounting, a build-up type multilayer flexible circuit board having a double-sided or multilayer flexible circuit board as a core substrate and having one or two build-up layers on both sides or one side has also been put into practical use (for example, , Japanese Patent Application Laid-Open No. 2004-200260).

However, the build-up type multilayer flexible circuit board described above has a problem that high density mounting cannot be easily achieved. That is, when the conductive portion having the bottom electrically connecting the build-up layer and the inner double-sided core board is electrically connected between the circuit of the inner core board and the circuit of the outermost layer through the so-called via holes, the depths of the via holes are increased. There is a problem that the via conduction portion due to thermal expansion in the thickness direction of the member is broken, or the plating liquid easily stays at the bottom portion in the plating film forming step, and thus the thickness cannot be sufficiently obtained.

Therefore, in order to secure electrical reliability, the thickness of the via hole wall is thickened, the thickness of the outermost conductor layer becomes thick, and the formation of the microcircuit becomes difficult, making it difficult to satisfy the demand for high density mounting.

FIG. 5 is a cross-sectional process diagram showing a conventional method for manufacturing a multilayer circuit board. First, as shown in FIG. 5 (1), a flexible insulating base material 151 such as polyimide (here, thickness An interlayer connection hole 154 is formed by an NC drill or the like for the so-called double-sided copper clad laminate having copper foils 152 and 153 having a thickness of 8 μm on both sides of a 25 μm polyimide), and an interlayer connection hole 154 The partial plating resist layer 155 is formed except for a portion thereof.

Subsequently, as shown in FIG. 5 (2), an electroplating film 156 of about 10 µm is formed by the conduction treatment followed by the electrolytic plating treatment in the interlayer connection hole 154 to complete the interlayer connection path. . Through-holes, through-holes are formed in the conventional process. In this way, the plated film is formed only on the conductive portions on both sides, and the plated film is not formed on the copper foil in the region where the wiring pattern is formed. Therefore, since the conductive layer for the wiring pattern can be made thin, a fine circuit is formed. desirable.

Subsequently, as shown in FIG. 5 (3), a series of series of resist layer formation, exposure, development, etching, resist layer peeling and the like for forming the wiring patterns on both sides by a photo-fabrication method By the process, the wiring pattern 158 including the through hole land 157 is formed.

Subsequently, as shown in Fig. 5 (4), for example, the polyimide film 160 having a thickness of 12 μm is adhered using an adhesive material such as acrylic or epoxy having a thickness of 20 μm and covered with a coverlay ( 161 is formed.

In order to bond the coverlay 161 to both surfaces, it is adhered using a vacuum press, a vacuum laminator, or the like, in order to prevent bubbles from entering into the circuit gap or the interlayer connection hole.

The double-sided core substrate 162 is obtained by the above processes.

Then, as shown to (5) of FIG. 6, what is called one-side copper field which has copper foil of thickness 12micrometer on one surface of flexible insulating base materials 163 (here, polyimide of thickness 25micrometer), such as a polyimide With respect to the copper foil of the laminated board, the interlayer connection hole having a bottom is removed by laser processing by a photofabrication method by a series of processes such as formation of a resist layer, exposure, development, etching, and peeling of a resist layer. The opening 164 for forming is formed, and it is made into the light shielding conformal mask 165 of a laser, and is laminated | stacked on the double-sided core board 162 by the adhesive 166 for building up on the double-sided core board 162. Glue. The adhesive 166 is preferably one having a low outflow such as a low flow type prepreg and a bonding sheet.

Next, as shown in FIG. 6 (6), the interlayer connection hole 167 is formed by laser processing using the conformal mask 165 produced at the said process. As the laser processing method, a UV-YAG laser, a carbonic acid laser, an excimer laser, or the like can be selected.

Subsequently, as shown in FIG. 6 (7), an electrolytic plating film 168 having a thickness of about 25 to 30 μm for interlayer connection is formed by conduction treatment and subsequent electroplating treatment. The branches form an interlayer connection path by via holes.

Subsequently, as shown in FIG. 7 (8), the pattern 169 of the outer layer is formed by a normal photofabrication method. Thereafter, if necessary, a photo solder resist layer is formed, solder plating, nickel plating, gold plating, and the like are subjected to surface treatment to form a multilayer circuit board.

As described above, when electroplating is performed on a copper foil having a thickness of 12 µm to about 25 to 30 µm, the total conductor thickness of the outer layer becomes 37 to 42 µm, and it is difficult to form fine patterns with a circuit pitch of 100 µm with good yield. However, it cannot satisfy the demand for high density mounting.

As described above, in the conventional method, the via hole of the build-up layer, which is necessary for securing the connection reliability of the via-hole electrically connecting the build-up layer and the double-sided core board of the inner layer, also has a thick gold thickness, making it difficult to form a microcircuit and Can not meet the demand. For this reason, there is a demand for a method of manufacturing a multilayer circuit board capable of high density mounting at low cost and stably.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described points, and provides a multilayer circuit board capable of forming a circuit capable of fine and high density mounting, and at the same time, provides a method of manufacturing such a multilayer circuit board at low cost and stably. For the purpose of

In order to achieve the above object, in the present invention,
In the manufacturing method of the multilayer circuit board which laminated | stacked the outer layer buildup layer on the flexible inner core board, and connected by the interlayer connection hole,
a) a process of preparing a double-sided copper clad laminate having copper foil on both sides of the flexible insulating base material and forming a through hole,
b) partially plating the interlayer connecting portion of the circuit board positioned at the bottom of the through hole and its periphery and the via hole formed in a subsequent process;
c) a step of forming a wiring pattern by treating copper foil by a photo-fabrication method in the double-sided copper clad laminate, and forming a receiving land thicker than the thickness of the wiring pattern in the interlayer connection portion;
d) attaching the coverlay with a press apparatus having a smooth hot plate, to produce an inner layer core substrate,
e) A base insulating resin side of the outer layer build-up layer having a perforation opening is formed to face the inner core board in a portion of the one-side copper-clad laminate to face the inner core board through an adhesive material. Laminating to to form a laminated circuit board,
f) perforating the laminated circuit substrate by laser processing using the opening to form a bottomed interlayer connection hole reaching the receiving land, and
g) a method of manufacturing a multilayer circuit board, comprising the step of forming a via hole by conducting a conductive treatment and electroplating on the interlayer connection hole.

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Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(Example 1)

1 is a conceptual cross-sectional view showing the structure of a multilayer circuit board according to a first embodiment of the present invention. In the first embodiment, the outer layer circuit board of one surface is laminated on the inner double-sided core board 14, and the inner circuit and the circuit of the outer layer circuit board built up are joined by a bottomed via hole.

In this multilayer circuit board, an inner circuit board and an outer circuit board are made of a flexible circuit board material having flexibility, and a part of the flexible inner layer double-sided board is extended to the outside of the multilayer part to form a cable part. It is.

The feature of the first embodiment is that the electroplating film 7 is formed in the receiving land portion 10 of the via hole for electrically connecting the circuit of the inner circuit board and the circuit of the outer circuit board.

2 is a cross-sectional process diagram showing a method for manufacturing a multilayer circuit board according to the first embodiment of the present invention. In the first embodiment, the flexible multilayer circuit board shown in Fig. 1 is employed as an example of production.

First, what is called a double-sided copper clad laminated board which has copper foils 2 and 3 of thickness 8micrometer in the upper and lower surfaces shown in flexible insulating base material 1 (here, polyimide of thickness 25micrometer), such as polyimide, is prepared. . At this time, the copper foil is preferably a rolled copper foil or a special electrolytic copper foil having excellent flexibility.

Subsequently, as shown in FIG. 2 (1), the interlayer connection hole 4 is formed in this double-sided copper clad laminate with an NC drill or the like. Furthermore, except for the via hole receiving land forming portion 5 located at the bottom of the interlayer connection hole 4 and its periphery and the interlayer connection hole formed in a later step, the partial plating resist layer 6 is formed. do.

Subsequently, as shown in FIG. 2 (2), an electroplating film 7 having a thickness of about 10 μm is formed in the interlayer connection hole 4 and the receiving land portion 5 by a conduction treatment followed by an electrolytic plating treatment. To form an interlayer connection hole. At this time, the conductor thickness of the accommodation land portion 5 is made thick. Through-holes, through-holes are formed in the conventional process.

Subsequently, a series of processes, such as formation, exposure, development, etching, and resist layer peeling, of forming a resist layer for forming a double-sided wiring pattern by a photofabrication method are performed, and through-hole land shown in FIG. The wiring pattern 9 and the receiving land portion 10 including the 8 are formed.

Subsequently, as shown in FIG. 2 (4), the coverlay 13 is adhered by, for example, attaching a polyimide film 11 having a thickness of 12 µm using an adhesive 12 such as acrylic or epoxy having a thickness of 20 µm. ). When forming this coverlay 13, it adhere | attaches with the press apparatus which has a hot plate with parallelism and smoothness, for example of a flat plate fryer.

Here, the reason for using a flat plate press or the like is because the coverlay surface needs to be smoothly processed even at a place where the conductor thickness is different. In addition, the same effect can be acquired also if a mirror-treated stainless plate etc. are used as an intermediate plate.

Moreover, when applying a sequential lamination process, it is also possible to employ the method of using an above-mentioned flat plate press etc. after advancing an initial lamination to the apparatus with good fillability, such as a vacuum lamination, at the temperature which does not lose the fluidity | liquidity of an adhesive agent. . By the above processes, the double-sided core board | substrate 14 used as a core board | substrate of a multilayer circuit board is obtained.

Thereafter, as shown in Fig. 3 (5), an opening 16 is formed in the copper foil of the one-side copper-clad laminate to form a conformal mask 17 and laminated on the upper and lower surfaces shown in the double-sided core substrate 14. .

That is, formation and exposure of a resist layer with respect to the copper foil of what is called one-side copper clad laminated board which has copper foil of 12 micrometers in thickness on one side of soluble insulating base material 15 (here, polyimide of 25 micrometers in thickness), such as a polyimide, And the opening 16 for removing the resin by laser processing to form a bottomed interlayer connection hole by a photofabrication method by a series of processes such as development, etching, peeling of a resist layer, and the like. Is used as the light shielding conformal mask 17. At the same time, lamination and adhesion are performed on the double-sided core substrate 14 by an adhesive 18 for building up on the double-sided core substrate 14. The adhesive 18 is preferably one which is low in leakage, such as a low flow type prepreg or a bonding sheet.

Subsequently, as shown in FIG. 3 (6), the interlayer connection hole 19 is formed by laser processing using the conformal mask 17 produced by the said process. The laser processing method can be performed by selecting a UV-YAG laser, a carbonic acid laser, an excimer laser, or the like.

Subsequently, as shown in FIG. 4 (7), an electroplating film 20 having a thickness of about 25 to 30 μm for interlayer connection is formed by conducting and subsequent electroplating. The via hole interlayer connection route

Subsequently, as shown in FIG. 4 (8), the pattern 21 of the outer layer is formed by a normal photofabrication method. After that, a multilayer circuit board is obtained by forming a photosolder resist layer, performing surface treatment such as solder plating, nickel plating, and gold plating, if necessary, to perform external processing.

According to the above manufacturing method, since the plating film 7 is formed in the receiving land portion 10 of the interlayer connection hole, the depth of the interlayer connection hole 19 is about 10 占 퐉 shallower than that of the conventional structure, and the interlayer connection Easiness of electrodeposition of the wall plated film of the via hole with respect to the hole 19 improves, and it becomes an advantageous structure, such that it becomes hard to be influenced by the thermal expansion of a structural member. For this reason, the plating thickness required for improving the yield and ensuring the reliability can be reduced.

In addition, the structure in which the accommodation land portion 10 is also plated has an effect of alleviating thermal damage during laser processing for forming the interlayer connection hole.

In addition, when the interlayer connection hole is formed by non-through processing using an NC drill, the conventional method requires a high machining precision in the depth direction, which increases the working margin as compared to the difficult work. For this reason, it becomes possible to select the non-penetrating process by NC drill which is cheaper than laser processing depending on a design specification.

In Example 1, the method of shallowing the depth of the interlayer connection hole was selected by increasing the thickness of the plating. However, a method such as printing a conductive paste or ink on the receiving land can also be selected.

On the other hand, in addition to the processing using a conformal mask as described above, the laser processing can be applied to the laser processing in which the copper mask is opened larger than the beam diameter of the laser in advance, and the laser processing is performed there.

Moreover, 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, 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 like Example 1.

(Another embodiment)

In the multilayer circuit board shown in Figs. 2 to 4, a flexible multilayer circuit board having a core board as the flexible circuit board and a part thereof as the flexible cable section 22 extending from the multilayer component mounting section. The same applies to the case where the core board is a multilayer circuit board which does not constitute a flexible cable.

In addition, the multilayer circuit board may have a structure in which an outer layer buildup layer is laminated on only one surface of the core board rather than both surfaces thereof.

By the above-mentioned features, the present invention has the following effects.

According to the manufacturing method of the present invention, an inner layer core substrate having a thickly plated receiving land is formed, an outer layer build up substrate having a perforation opening is formed, and an outer layer build up substrate is laminated on the inner layer core substrate, and the receiving land and Since the interlayer connection is performed using the apertures for drilling, circuit boards capable of high-density mounting, which have been difficult in the conventional manufacturing method, can be manufactured at low cost and stably.
In addition, since the multilayer circuit board manufactured by the present invention thickens the plating of the receiving lands of the via holes, it is possible to form a via hole having a shortened wall surface by shallowing the depth of the via hole using this receiving land as the bottom surface. As a result, electrodeposition of the plated film on the wall becomes easy, and it is difficult to be affected by thermal expansion of the component.
As a result, the plating thickness required for improving the yield and securing the reliability can be reduced, and fine wiring patterns can be formed in the outer layer with good yield, thereby enabling high-density mounting of the circuit board.

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Claims (2)

delete In the manufacturing method of the multilayer circuit board which laminated | stacked the outer layer buildup layer on the flexible inner core board, and connected by the interlayer connection hole, a) a process of preparing a double-sided copper clad laminate having copper foil on both sides of the flexible insulating base material and forming a through hole, b) partially plating the interlayer connecting portion of the circuit board positioned at the bottom of the through hole and its periphery and the via hole formed in a subsequent process; c) a step of forming a wiring pattern by treating copper foil by a photo-fabrication method in the double-sided copper clad laminate, and forming a receiving land thicker than the thickness of the wiring pattern in the interlayer connection portion; d) attaching the coverlay with a press apparatus having a hot plate having smoothness to manufacture an inner layer core substrate, e) A base insulating resin side of the outer layer build-up layer having a perforation opening is formed to face the inner core board in a portion of the one-side copper-clad laminate to face the inner core board through an adhesive material. Laminating to to form a laminated circuit board, f) perforating the laminated circuit substrate by laser processing using the opening to form a bottomed interlayer connection hole reaching the receiving land, and g) a step of forming a via hole by conducting a conductive process and electroplating on said interlayer connection hole.

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