JP5452759B1 - Wiring board manufacturing method - Google Patents

Abstract

The present invention provides a method of manufacturing a wiring board that can efficiently and inexpensively drill a small-diameter hole corresponding to fine wiring.
Electrolytic plating is performed on both surfaces of a first substrate 3 on which a conformal mask 4 is formed, and the conductor layer 5 thickened so as to narrow the opening diameter of the opening 4a is masked. As a result, the opening 4a is irradiated with laser light to remove the insulating resin base material layer 1 and the bottomed via 6 is formed.
[Selection] Figure 1

Description

  The present invention relates to a method of manufacturing a wiring board having a small diameter via hole corresponding to, for example, a fine wiring.

  In addition to machining, laser machining is used as a method of machining via holes and other small-diameter holes connected to a wiring pattern on a wiring board. In order to process small holes with high accuracy, a conductor film such as copper foil formed on a printed circuit board for circuit wiring is used as a laser processing mask (conformal mask) for drilling holes. The method is used.

First, a conductive film (copper foil or the like) laminated on an insulating resin substrate is etched to form a conformal mask having openings, and laser light such as YAG laser or carbon dioxide (CO ₂ ) laser is opened. Is irradiated to form a hole (via hole formation). After that, electroless copper plating and electrolytic copper plating are applied to the conductor film including the via hole to form a conductor layer, and a necessary wiring pattern is formed by patterning (etching resist formation⇒etching⇒etching resist peeling). (See Patent Document 1).

JP 2008-198922 A

  When a small-diameter hole is processed by irradiating a laser to the opening provided in the conductor film of the wiring board, the smaller the hole diameter of the conductor film, the smaller the hole can be processed. However, when a conformal mask is formed on a conductor film such as a copper foil by etching, side etching occurs due to the etching solution, and etching is performed with an opening diameter larger than the opening diameter of the etching resist. Therefore, for example, in order to form a via hole having an opening diameter of φ40 μm or less, it is necessary to bake an etching resist pattern of φ20 μm or less, and a special jig such as a glass dry plate is required.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method of manufacturing a wiring board capable of drilling a small diameter in a board efficiently and inexpensively corresponding to fine wiring.

In order to achieve the above object, a method for manufacturing a wiring board according to the present invention comprises the following arrangement.
That is, a step of preparing a first substrate in which a copper foil with a carrier is laminated on both surfaces of an insulating resin base material and a copper foil with a carrier is laminated, and etching the copper foil with a carrier of one of the first substrates by etching. Removing the step of forming a conformal mask having an opening, and performing electroplating on both surfaces of the first substrate on which the conformal mask is formed, including the wall surface of the opening of the copper foil with carrier. A step of thickening the conductive layer; and the insulating resin base layer is formed by irradiating the opening with a laser beam using the conductive layer thickened as the mask so as to narrow the opening diameter of the opening. And forming a bottomed via in which the copper foil of the other carrier-attached copper foil is exposed at the bottom.

If the above method for manufacturing a wiring board is used, the conductive layer is thickened so that the opening diameter of the opening is narrowed by performing electrolytic plating on both surfaces of the first substrate on which the conformal mask is formed. As the mask irradiates the opening with laser light, the insulating resin substrate layer is removed and a bottomed via is formed, so the opening diameter of the opening can be changed by changing the thickness of the conductor layer thickened on the wall of the opening By controlling this, a via hole having a desired diameter can be formed in the wiring board.
In addition, since a small-diameter opening is formed in the conductor layer by etching, a special jig such as a glass dry plate with high resolution is not required for baking of the etching resist, and it is inexpensively configured using general equipment. In addition to forming a formal mask, a via hole having a fine hole diameter can be formed in a short time by using a carbon dioxide laser having a high energy level.

In the method for manufacturing a multilayer wiring board, the first substrate in which the copper foil with a carrier is laminated by bringing the copper foil into close contact with the double-sided insulating resin layer in which the inner layer conductor pattern is formed on the inner layer of the insulating resin base material And a step of forming a conformal mask having an opening in which the insulating resin layer is exposed at the bottom by respectively removing the copper foil with carrier laminated on both surfaces of the first substrate by etching. And performing electrolytic plating on both surfaces of the first substrate on which the conformal mask is formed, and thickening the conductor layers including the opening wall surfaces of the copper foil with carrier. And
By using the above method for manufacturing a wiring board, it is possible to efficiently and inexpensively form a fine via hole filled with a conductor that connects the fine wiring patterns of the multilayer wiring board to each other.

In the production of the wiring board, the opening diameter of the surface of the conductor layer opening serving as a conformal mask for irradiating laser light is 10 μm or more larger than the minimum opening diameter.
By increasing the opening diameter of the surface of the conductor layer opening, the minimum opening diameter that determines the processing diameter of the hole is small, but the energy of the laser beam can be collected in a larger area than the minimum opening, so the laser beam Can be efficiently used for drilling.

  If the manufacturing method of a wiring board mentioned above is used, a small diameter drilling process can be performed to a board | substrate efficiently and cheaply corresponding to fine wiring.

It is sectional drawing which shows the manufacturing process of the manufacturing method of a wiring board. It is sectional drawing which shows the manufacturing process of the manufacturing method of a multilayer wiring board. It is the cross-sectional photograph figure of the opening part of a conformal mask, and the cross-sectional photograph figure of the opening part after thickening electrolytic copper plating.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
A method for manufacturing a wiring board will be described with reference to FIGS. 1A to 1K together with the structure of the wiring board. In the following description, the carrier-attached copper foil is, for example, an ultra-thin copper foil (copper foil; thickness 2 to 5 μm) laminated with a carrier copper foil (thickness 18 μm; carrier foil) via a release layer. (For example, F-HP; Heat-Resistant Peelable Copper Foil) is used.

  As shown in FIG. 1A, a first substrate 3 having a carrier-attached copper foil 2 pasted on both surfaces of an insulating resin base material 1 (for example, FR-4) is prepared. In the first substrate 3, the carrier-attached copper foil 2 is bonded to a copper foil 2 a bonded to the insulating resin base material 1 with a carrier copper foil 2 b called a carrier foil through a release layer. The carrier copper foil 2b can be more easily separated from the release layer than the copper foil 2a.

In FIG. 1B, one of the first substrates 3 (for example, the upper surface side) copper foil 2 with a carrier is removed by etching to form a conformal mask 4 having an opening 4a. Etching is performed by laminating an etching resist corresponding to a mask pattern on the copper foil 2 with a carrier on the first substrate 3, so that the copper foil 2 with a carrier is partially removed and the insulating resin substrate 1 is exposed at the bottom. Opened portion 4a is formed.
The cross section of the opening 4a formed by etching the carrier-attached copper foil 2 is finished in a tapered state by etching side etching. The shape of the taper can be changed by adjusting the thickness of the copper foil 2 with a carrier.

  In FIG. 1C, electrolytic copper plating is performed on both surfaces of the first substrate 3 on which the conformal mask 4 is formed, and the conductor layer 5 including the inner wall surface of the opening 4a of the copper foil with carrier 2 is thickened. Attach. Adjustment of the copper plating thickness at this time can be performed according to the magnitude of the current value or the length of the plating time. When the value of the current flowing through the electrolyte is increased, the copper deposition rate is increased, so that the copper plating can be thickened. Further, even if the plating time is increased with the same current value, the copper plating can be similarly thickened. Generally, in order to increase production efficiency, the plating thickness is adjusted by the magnitude of the current value.

  When the conductive layer 5 is electrolytically plated, the conductor edge portion is markedly rounded due to the phenomenon that the plating shape is rounded by the effect of the additive of the plating bath and the taper shape of the opening conductor layer cross section. Since the shape can be formed, the opening diameter of the surface of the conductor layer 5 can be made larger than the minimum opening diameter of the opening 4a.

According to the experiment, when copper plating with a thickness of 28 μm is formed on the carrier copper foil 2b having an opening diameter of φ60 μm in the opening 4a in FIG. 3, the opening diameter of the opening 4a is φ16 μm.
This is because, when copper plating with a thickness of 24 μm is performed, the opening diameter 4a is 4 μm (60 μm−28 × 2 μm). However, the surface copper thickness increases, and the smaller the opening diameter, the more the copper plating is applied to the wall surface of the opening. The cause is thought to be worse.

  Next, in FIG. 1D, the opening 4a is irradiated with laser light using the conductor layer 5 with the conductor layer 5 thickened so as to narrow the opening diameter of the opening 4a. As the laser beam, a carbon dioxide laser having a high energy level is preferably used. Thereby, as shown in FIG. 1E, the insulating resin base material layer 1 exposed in the opening 4a is partially removed, and the bottomed via in which the copper foil 2a of the other carrier-attached copper foil 2 is exposed at the bottom. 6 is formed. Even if the minimum opening diameter of the opening 4a is small, the laser light can receive more light because the opening diameter on the surface of the conductor layer is large, and the insulating resin base material 1 exposed to the opening 4a using the conductor layer 5 as a mask has energy. It can be removed efficiently.

  Next, after removing the copper foil 2a exposed at the bottom of the bottomed via in FIG. 1 (F), the carrier copper foil 2b laminated on both surfaces of the first substrate 3 is peeled off to form the insulating resin base material layer 1. Only the copper foil 2a (thin film) is laminated, and the second substrate 8 having the via hole 7 penetrating therethrough is formed.

  Next, in FIG. 1G, via fill plating is applied to both surfaces of the second substrate 8, and the via hole 7 is filled with the conductor of the conductor layer 9, and the conductor layer 9 is thickened on the copper foil 2a. Via fill plating is a plating method in which copper is preferentially deposited inside the via hole 7 by using a copper sulfate plating bath plating to which an inhibitor for suppressing plating growth and an accelerator for promoting plating growth are added.

  Finally, in FIG. 1 (H), an etching resist is laminated on the conductor layer 9 formed on both surfaces of the second substrate 8, exposed and developed to form a resist pattern, and then the conductor layer 9 is partially etched. The conductor pattern 10 is formed by removing. Then, by removing the etching resist, the wiring substrate 11 having the conductor pattern 10 formed on both surfaces of the insulating resin base material 1 is obtained.

  Further, in place of the above-described via fill plating for the second substrate 8 in FIG. 1G, the conductive layer 12 patterned by applying pattern plating on the copper foil 2a as shown in FIG. Attach. Thereafter, as shown in FIG. 1 (J), the copper foil 2a exposed between the patterned conductor layers 12 is removed by soft etching to form conductor patterns 10 on both surfaces of the second substrate 8. Thus, you may form the wiring board 11 in which the conductor pattern 10 was formed in both surfaces of the insulating resin base material 1. FIG.

If the above-described method for manufacturing a wiring board is used, electrolytic conductor plating is performed on both surfaces of the first substrate 3 on which the conformal mask 4 is formed, and the conductor layer 5 is thickened so as to narrow the opening diameter of the opening 4a. Further, the insulating resin base material 1 is removed by irradiating the opening 4 with laser light using the conductor layer 5 as a mask to form the via hole 7, so the thickness of the conductor layer 5 thickened on the wall surface of the opening 4 By controlling the opening diameter accordingly, the via hole 7 having a desired diameter can be formed in the wiring substrate 11.
In addition, since a small-diameter opening is formed in the conductor layer by etching, a special jig such as a glass dry plate with high resolution is not required for baking of the etching resist, and it is inexpensively configured using general equipment. In addition to the formation of the formal mask 4, the via holes 7 having a fine hole diameter can be efficiently formed in a short time by condensing more carbon dioxide lasers having a high energy level.

Next, a method for manufacturing a multilayer wiring board will be described with reference to FIG.
In FIG. 2 (A), the copper foil 2a with a carrier is laminated | stacked by sticking the copper foil 2a to the double-sided insulating resin layer 21a of the 1st board | substrate 22 with which the inner layer conductor pattern 22 was formed in the inner layer of the insulating resin base material 21, respectively. The prepared first substrate 23 is prepared.

  In FIG. 2B, the carrier-attached copper foils 2 laminated on both surfaces of the first substrate 23 are respectively removed by etching to form conformal masks 24 each having an opening 24a. Etching is performed by laminating an etching resist corresponding to the mask pattern on the copper foil 2 with a carrier on the first substrate 22, so that the copper foil 2 with a carrier is partially removed and the insulating resin layer 21 a is exposed at the bottom. An opening 24a is formed.

  In FIG. 2C, electrolytic copper plating is performed on both surfaces of the first substrate 23 on which the conformal mask 24 is formed, and the conductor layers 25 including the inner wall surfaces of the openings 24a of the carrier-attached copper foil 2 are formed. Thicken. Since the surface layer of the first substrate 23 is the carrier copper foil 2b of the carrier-attached copper foil 2, the copper plating is thickened. Adjustment of the copper plating thickness at this time is performed according to the magnitude of the current value.

  In FIG. 2D, the opening 24a is irradiated with laser light using the conductor layer 25 thickened so as to narrow the opening diameter of the opening 24a as a mask. As the laser beam, a carbon dioxide laser having a high energy level is preferably used. 2E, the insulating resin layer 21a exposed at the opening 24a is partially removed, and the bottomed via 26 where the inner layer conductor pattern 22 is exposed at the bottom is formed on both surfaces of the first substrate 23. Formed.

  In FIG. 2 (F), the carrier copper foil 2b laminated on both surfaces of the first substrate 23 is peeled off, so that only the copper foil 2a is laminated on the double-sided insulating resin layer 21a and the inner layer conductor pattern 22 is exposed. A second substrate 27 having bottom vias 26 on both sides is formed.

  Next, in FIG. 2G, the copper foil 2a laminated on both surfaces of the second substrate 27 is removed by soft etching. The former is wide and the latter is narrow in the opening diameter of the conformal mask 24 formed on the copper foil 2 with a carrier and the opening diameter after electrolytic copper plating (after laminating the conductor layer 25). The copper around the opening 24a after the electrolytic copper plating is not bonded to the insulating resin layer 21a because the copper plating is thickened on the end face of the copper foil 2 with a carrier of the conformal mask 24. Therefore, when the carrier copper foil 2b and the conductor layer 25 (electrolytic copper plating) are peeled off, an exposed portion of the insulating resin layer 21a without the copper foil 2a is formed. In order to prevent this exposed portion from becoming a step in the subsequent plating step, it is removed by soft etching. As the etching solution, an aqueous solution of sulfuric acid / hydrogen peroxide, sodium persulfate, potassium persulfate or the like is used.

  Next, in FIG. 2H, electroless copper plating is performed on both surfaces of the soft-etched second substrate 27 to form a conductive film 28 that covers the insulating resin layer 21a and the wall surface of the bottomed via 26.

  Next, in FIG. 2I, panel plating is performed on both surfaces of the second substrate 27 on which the conductor film 28 is formed, and the conductor layer 29 is thickened on the conductor film 28. In the panel plating, via hole plating in the bottomed via 26 and electrolytic copper plating are simultaneously performed on both surfaces of the second substrate 27 to fill the via holes with the conductor layer 29 and thicken the conductor layer 29 on both surfaces of the substrate.

  Next, in FIG. 2J, an etching resist is laminated on the conductor layer 29 formed on both surfaces of the second substrate 27 and patterned, and then the conductor layer 29 is partially removed by etching to form a conductor pattern 30. Form. Then, by removing the etching resist, a multilayer wiring substrate 31 in which the conductor pattern 30 is formed on both surfaces of the second substrate 27 is obtained.

  Also, in FIG. 2 (I), both sides of the second substrate 27 are replaced with panel plating, and pattern plating is applied as shown in FIG. 2 (K) to thicken the conductor layer 32 patterned on the conductor film 28. May be. Next, as shown in FIG. 2 (L), the conductor film 28 exposed between the patterned conductor layers 32 is partially removed by flash etching to form a conductor pattern 30 on both surfaces of the second substrate 27. The multilayer wiring board 31 thus manufactured may be manufactured. In the flash etching, a copper layer (conductor film 28) having a thickness of about 2 to 5 μm is removed without using a plating resist.

In this embodiment, the hole forming process of the insulating resin layer is performed with a carbon dioxide gas laser, but the same process can be performed using a UV-YAG laser or another laser.
In addition, the conduction of the holes formed by the drilling method of the present invention can be achieved by plating the conductors of the conductor layer on the hole walls in addition to filling the conductors of the conductor layer.

  If the above-described method for manufacturing a wiring board is used, the fine bottomed via 26 filled with the conductor layers 29 and 32 for connecting the fine wiring patterns of the multilayer wiring board 31 to each other can be efficiently and inexpensively formed. .

  DESCRIPTION OF SYMBOLS 1,21 Insulation resin base material 2 Copper foil with carrier 2a Copper foil 2b Carrier copper foil 3,23 First substrate 4,24 Conformal mask 4a, 24a Opening 5, 9, 12, 25, 29, 32 Conductor layer 6, 26 Bottomed via 7 Via hole 8, 27 Second substrate 10, 30 Conductor pattern 11 Wiring substrate 21a Insulating resin layer 22 Inner layer conductor pattern 28 Conductor film 31 Multilayer wiring substrate

Claims (3)

Preparing a first substrate in which a copper foil with a carrier is laminated by adhering a copper foil to both surfaces of an insulating resin base;
Removing the copper foil with carrier of one of the first substrates by etching to form a conformal mask having an opening;
Performing electrolytic plating on both surfaces of the first substrate on which the conformal mask is formed, and thickening a conductor layer including an opening wall surface of the copper foil with carrier;
Using the conductor layer with the conductor layer thickened to narrow the opening diameter of the opening as a mask, the opening is irradiated with laser light to remove the insulating resin base material layer, and the other carrier is attached to the bottom. Forming a bottomed via in which the copper foil is exposed;
A method for manufacturing a wiring board, comprising: Preparing a first substrate in which the copper foil with carrier is laminated by bringing the copper foil into close contact with the double-sided insulating resin layer in which the inner layer conductor pattern is formed on the inner layer of the insulating resin base material;
Removing the copper foil with carrier laminated on both surfaces of the first substrate by etching to form a conformal mask having an opening in which the insulating resin layer is exposed at the bottom; and
Performing electroplating on both surfaces of the first substrate on which the conformal mask is formed, and thickening each of the conductor layers including the wall surface of the opening of the copper foil with carrier;
The opening layer is exposed to a laser beam using the conductor layer with the conductor layer thickened so as to reduce the opening diameter of the opening to remove the insulating resin layer, and the inner layer conductor pattern is exposed at the bottom. Forming bottomed vias on both sides of the first substrate;
A method for manufacturing a wiring board, comprising:   3. The method of manufacturing a wiring board according to claim 1, wherein the opening diameter of the surface of the opening portion of the conductor layer serving as a conformal mask for irradiating the laser light is 10 μm or more larger than the minimum opening diameter.

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