JPH11300487A - Drilling method and drilled body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drill a hole having a desired size and a beautiful shape by applying an optical process, a process of reducing reflection as blackening process, to a conductive layer of a prescribed shape provided on a base body, forming an insulation layer on the conductive layer, and then irradiating the insulation layer with light beam. SOLUTION: On the surface of a substrate 1 consisting of a hard resin for multilayer wiring board, a copper foil 2 is formed in a prescribed wiring pattern by means of photolithography and etching. Then, with an oxidation (blackening process) applied to the surface of the copper foil 2 using a potassium permanganate solution, an oxide film (blackened substance) 3 is formed. This oxide 3 is a copper oxide film(CuO) and a black layer with a rough surface. Next, on the surface of the substrate 1, an insulation layer 4 is formed in film by means of a glass fiber resin for example. Then, with a few pulses of laser beam emitted at a prescribed position with a desired diameter value (circular shape), the insulation layer 4 and the oxide film 3 are destroyed by the heat of the laser beam to form a hole 6 reaching the copper foil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling method for drilling a hole such as a connection hole using a beam such as a laser beam, and a drilled body formed by the drilling method. .

[0002]

2. Description of the Related Art At present, the mainstream of printed wiring boards is a multilayer printed wiring board having a laminated structure in which planar conductive layers and insulating layers are alternately arranged.

In general, many holes are formed in a multilayer printed wiring board for the purpose of forming through-hole (blind via hole) connection holes and forming lead component insertion paths, as in the case of a double-sided wiring board. .

[0004] With the progress of plating technology, the aspect ratio also tends to increase in holes in a multilayer printed circuit board, and there is a limit in the processing accuracy and positional accuracy in the conventional drilling of holes.

Therefore, in recent years, a plurality of double-sided wiring boards having a conductive circuit on the front side and the back side are bonded with a prepreg (for example, glass fiber reinforced resin), and necessary conductive layers are formed in a multilayer printed wiring board in which these are laminated. For processing holes (blind barrier holes and through holes) in an insulating layer for connecting the holes, a laser processing technique using laser light using a carbon dioxide gas laser or an excimer laser as a light source is used.

[0006]

Here, an example of perforating an insulating layer by a conventional laser processing technique will be described with reference to FIG.

First, as shown in FIG. 8A, a laminated structure in which a copper foil 2 having a predetermined shape as a conductive layer is provided on a substrate 1 and an insulating layer 4 is further provided on the entire surface thereof. In step, a predetermined position is irradiated with a laser beam 11.
Then, as shown in FIG. 8B, the portion of the insulating layer 4 irradiated with the laser beam 11 is eroded, and a fine hole 12 having a predetermined shape reaching the copper foil is formed.

However, the surface of the copper foil 2 has a fine and uneven shape with gloss, and the laser light is irregularly reflected by the fine unevenness on the surface of the copper foil. Then, FIG.
As shown in (C), the insulating layer 4 near the bottom around the microhole 12 is ablated by the irregularly reflected laser beam 11 ′,
The hole shape will be deformed.

It is sufficient that the laser beam is not irradiated until the hole shape is deformed. However, if the laser beam is not sufficiently irradiated, a part of the insulating layer 4 remains on the surface of the copper foil 2. It is necessary to irradiate a sufficient amount of laser light, since it may not be meaningful to form a hole.

Generally, when a hole is formed in an insulating layer having a thickness of 30 μm to 40 μm, a predetermined hole shape is formed by irradiating about 3 to 4 pulses of laser light. Later, the inspection of whether or not the insulating material remains is performed visually, so in order to sufficiently remove the insulating layer, it is necessary to irradiate a large amount of laser light with a reliable hole processing method. I have.

As described above, laser light is used as a means for forming a small-diameter hole in an insulating layer of a multilayer printed wiring board (build-up wiring board) because the laser light is linear light and the shape after processing is used. But clean shape (eg cylindrical)
It is to become.

However, if the thickness of the insulating layer is always constant and has the same component, the irradiation pulse of the laser beam may always be a constant value. It is necessary to irradiate as much laser light as possible and to destroy and remove the insulator on the copper foil surface so that the insulator does not remain. Then
Due to the unevenness and the gloss of the copper foil surface, the laser light exceeding the amount that ablates a predetermined thickness of the insulating layer is reflected on the copper foil surface, especially irregularly reflected, and destroys the periphery of the finished hole. As a result, a hole having a hole diameter larger than a value required by design or a hole having a rough hole wall is formed. The hole diameter tends to increase as the insulator remaining on the copper foil surface is surely removed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object a hole drilling method for drilling a hole having a desired size and a beautiful shape, and a hole drilling formed by this hole drilling method. Is to provide the body.

[0014]

That is, the present invention comprises a step of performing a reflection reduction process on a lower layer of a predetermined shape provided on a substrate, a step of forming a coating layer on the lower layer, and a step of forming the coating layer on the lower layer. Forming a hole that reaches the lower layer through a step of irradiating the coating layer with a beam on the lower layer on which the coating is performed (hereinafter, referred to as a hole processing method of the present invention). It is related to.

According to the hole drilling method of the present invention, a step of performing a reflection reduction process on a lower layer (particularly, a conductive layer) of a predetermined shape provided on a substrate, and forming a coating layer (particularly, an insulating layer) on the lower layer And a step of irradiating the coating layer with a beam such as a laser beam or an electron beam on the lower layer on which the reflection reduction processing has been performed to form holes such as fine connection holes that reach the lower layer. The coating layer is not destroyed by the reflection of the beam on the lower surface (particularly, irregular reflection), and therefore, a hole having a desired size and a clean shape is machined.

That is, the beam (particularly the light beam)
For example, taking advantage of the property of being easily absorbed in black and being hardly reflected on a rough surface, a film (for example, oxidation) by the reflection reduction processing is used to process an extra beam other than destroying the coating for drilling. By irradiating the film on the film, reflection of the beam on the surface of the lower layer is eliminated, and the shape of the hole is not deformed.

However, in the hole drilling method of the present invention, the reflection reducing process is a process for reducing the reflection of the beam on the lower surface, such as a blackening process (oxidation process) on the lower surface. Various reflection reduction treatments such as a non-reflective coating on the lower surface and a light absorption treatment (roughening of the lower surface) on the lower surface may be used.

Further, the present invention has a coating layer on a lower layer of a predetermined shape provided on a substrate, wherein a hole reaching the lower layer is formed in the coating layer, and the lower layer and the coating layer are In between, a drilled body (hereinafter, referred to as a drilled body of the present invention) in which a layer formed by the reflection reduction processing of the lower layer is formed.
Is provided.

The hole-formed body of the present invention is formed by the hole-forming method of the present invention, and is a work-piece (for example, a multilayer printed wiring board or a semiconductor device) having a desired size and a clean hole shape. is there.

However, the layer formed by the reflection reduction processing is a layer formed by the reflection reduction processing, and is, for example, a blackened material (oxide film) formed by the blackening processing of the lower surface.
The lower layer surface may be a coating layer formed by an anti-reflection coating, or a layer formed by various reflection reduction processes such as a light absorption process (for example, the lower layer roughened layer) on the lower layer surface.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the hole drilling method of the present invention, a conductive layer having a predetermined shape provided on the substrate is subjected to a blackening process as the reflection reducing process, and then an insulating layer is formed on the conductive layer. By irradiating the insulating layer with a light beam as the beam, fine holes having a predetermined shape reaching the conductive layer via the insulating layer can be formed. That is, the drilled body of the present invention has an insulating layer on a conductive layer of a predetermined shape provided on the base, and a hole reaching the conductive layer through the insulating layer is formed. The hole processing body may have a layer formed by blackening the conductive layer between the layer and the insulating layer.

The above-mentioned blackening treatment generally means, in the step of producing a multilayer printed wiring board, an inner layer made of copper foil and a prepreg (resin forming an insulating layer of the multilayer wiring board).
In order to improve the adhesion with the surface of the inner layer made of the copper foil, for example, a mixed solution of sodium chlorite, sodium hydroxide and sodium phosphate, or a strong alkali solution such as a potassium permanganate solution (Anchor treatment) to form a black copper oxide film having a rough surface.

In the hole forming method of the present invention, fine holes having a predetermined shape reaching the conductive layer via the insulating layer and the layer formed by the blackening treatment can be formed as the holes. That is, the drilled body of the present invention may be a drilled body in which fine holes of a predetermined shape reaching the conductive layer via the insulating layer and the layer formed by the blackening process are formed as the holes. .

Further, in the hole drilling method of the present invention, it is desirable that the copper foil provided as the conductive layer on the wiring board (particularly the printed wiring board) is subjected to the oxidation treatment as the blackening treatment. As the oxidation treatment, for example, a treatment of the surface of the copper foil with a chemical treatment solution such as a strong alkali solution of potassium permanganate can be given. That is, the drilled body of the present invention is a drilled body in which the insulating layer is a copper foil provided on a wiring board, and the copper foil has been subjected to the oxidation treatment as the blackening treatment. May be.

Therefore, a light beam of energy equal to or more than the energy required for processing a predetermined hole is not reflected by the copper foil surface and is absorbed by the blackened copper foil surface (that is, a blackened material or an oxide film). Therefore, the hole shape is not deformed. This copper foil is a conductive material that is easily blackened (oxidized) to form a divalent oxide film (CuO).

In the hole drilling method of the present invention, a laser beam is used as the light beam, and the hole can be formed in the insulating layer by heat generated by the irradiation of the laser beam. That is, the insulating layer is made of a material that can be ablated by a laser beam (for example, an epoxy resin, a polyimide resin, or the like), and is ablated by a laser beam using a carbon dioxide gas laser or an excimer laser as a light source. The holes can be formed.

Further, in the hole drilling method of the present invention and the drilled body of the present invention, the hole connects predetermined conductive layers of a multilayer printed wiring board having a laminated structure of the conductive layer and the insulating layer. Connection hole for the connection. Further, an upper conductive layer is provided so as to connect the conductive layer through the connection hole, and the present invention can be applied to manufacture a multilayer printed wiring board.

That is, the hole forming method of the present invention is desirably applied to the processing of a connection hole for connecting predetermined conductive layers of a multilayer printed wiring board (build-up wiring board). The conductive layer is also preferably a conductive layer having a predetermined shape formed by patterning a copper foil.

Next, a preferred embodiment based on the hole drilling method of the present invention will be described with reference to FIGS.

First, as shown in FIG. 2, a substrate 1 made of a hard resin for a multilayer wiring board such as a polyimide film is used.
Are formed in a predetermined wiring pattern on both surfaces of the copper foil 2a, 2b and 2c by photolithography and etching. These copper foils become inner layer copper foils in the multilayer printed wiring board.

Next, as shown in FIG.
When the surfaces of b and 2c are oxidized (blackened) using a potassium permanganate solution, the surfaces of the copper foils 2a, 2b and 2c are each formed by oxidation (hereinafter referred to as an oxide film or black film). 3a, 3b and 3c are respectively formed. These oxide films 3a, 3b and 3c
Is a copper oxide film (CuO), which is a black layer having a rough surface.

Next, as shown in FIG. 4, an insulating layer (prepreg) 4a is formed on one surface of the substrate 1 by, for example, a glass fiber resin, and similarly, on the other surface of the substrate 1, The insulating layer 4b is also formed.

Next, as shown in FIG. 5, a predetermined position (circular shape) of a few pulses of laser light 5 is irradiated to a predetermined position using a carbon dioxide gas laser or an excimer laser as a light source. As a result, the insulating layer 4a is broken (sprayed), and a hole 6a reaching the oxide film 3a is formed. Holes 6b and 6c are formed in the same manner as hole 6a.

Further, when the laser beam 5 is continuously irradiated,
As shown in FIG. 6, oxide film 3 applied on top of copper foil 2a
a is absorbed by the laser beam 5, and the oxide film 3a is destroyed.
The copper foil 2a underlying the oxide film 3a appears, and a hole 6a 'reaching the copper foil 2a is formed. Similarly, copper foils 2b and 2b
c, the holes 6b 'and 6c' have the desired pore diameter,
It is formed in a clean circular shape.

FIG. 1 is an enlarged view of the structure in the vicinity of the fine hole produced through such steps. That is, as shown in FIG. 1, through the insulating layer 4 and the oxide film (black matter) 3,
A hole 6 reaching the copper foil 2 (inner layer copper foil) formed in a predetermined wiring pattern on the substrate 1 is processed in a good processing shape.

Accordingly, the insulating layer 4 in a mass production process or the like can be used.
Even if there is variation in the thickness, material, etc., extra laser light 5 other than destroying the insulating layer 4 for processing the holes 6
Absorbed by the oxide film having a black and rough surface, that is, without being reflected on the surface of the copper foil 2, particularly without being irregularly reflected,
A hole having a desired value required by design and a hole having an excellent hole wall shape (in the present embodiment, a connection hole (blind via hole) for connecting predetermined conductive layers) are formed. In this step, it is only necessary to add the above-described blackening step to the hole forming step using the conventional laser beam technology, and the production cost and the like do not increase significantly.

As shown in FIG. 6, predetermined holes 6a ',
After processing 6b 'and 6c', a copper foil to be a further upper conductive layer is formed, for example, based on an electroplating method,
By processing this into a wiring pattern of a predetermined shape, as shown in FIG. 7, multilayer wiring of a conductive layer made of copper foils 2a, 2b and 2c and an upper conductive layer made of copper foils 7a, 7b and 7c The pattern is processed.

As described above, according to the present embodiment, (1) formation of a copper foil having a predetermined pattern (2) blackening treatment (oxidation treatment) (3) formation of an insulating layer (4) hole processing by laser light Since the holes are formed through a process, the holes can be formed with a hole diameter matching the laser beam irradiation diameter (for example, a circle), and the insulator is sufficiently removed (destroyed) for good hole processing. Even if the laser beam is irradiated with extra laser light, the energy of this laser light is only absorbed by the oxide film (black matter) on the copper foil and destroyed, and the pore diameter (size) , Shape, etc. are formed with desired design values.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to the above embodiment.

For example, as the lower layer (conductive layer), it is desirable to use the above-mentioned copper (copper foil) in terms of cost and resistance value. For example, tungsten, gold, and chromium may be used. Tungsten, gold, chromium, and the like change their surface to a color that easily absorbs light, such as black or reddish brown, by the oxidation treatment, so that the surface portion can be used as the oxide film.

The layer formed by the reflection reduction treatment may not be a blackened material obtained by the above-described blackening treatment of the copper foil surface.
For example, a light-absorbing (non-reflective) coating may be separately formed (coated), or a layer in which a predetermined surface roughness is applied to the lower layer surface so as to reduce light reflection on the lower layer surface ( Surface layer).

The hole by the laser beam is not limited to a connection hole for connecting predetermined conductive layers in a multilayer printed wiring board, but may be, for example, a detection hole for marking. Further, the present invention can be applied to formation of through holes, via holes, and the like in a semiconductor device.

The insulating layer may be formed of a photosensitive resin. When exposing the photosensitive resin by photolithography, a film formed by the reflection reduction treatment may be provided as a base.

[0044]

According to the hole drilling method of the present invention, a step of performing a reflection reduction process on a lower layer of a predetermined shape provided on a substrate, a step of forming a coating layer on the lower layer, On the treated lower layer, through a step of irradiating the coating layer with a beam such as a laser beam or an electron beam,
Forming a hole reaching the lower layer, so that the extra beam other than forming the hole is absorbed by the layer formed by the reflection reduction process, and the beam is absorbed by the lower layer surface. A hole having a desired size and a clean shape is processed without the coating layer being destroyed by irregular reflection.

The drilled body of the present invention has a coating layer on a lower layer of a predetermined shape provided on a substrate, and a hole reaching the lower layer is formed in the coating layer. Between the layers, a layer formed by the reflection reduction processing of the lower layer is formed, and the hole-formed body has a desired size and a clean shape.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a drilled body having holes drilled based on the drilling method of the present invention.

FIG. 2 is a schematic cross-sectional view showing one process step in producing the drilled body.

FIG. 3 is a schematic cross-sectional view showing another process step in producing the drilled body.

FIG. 4 is a schematic cross-sectional view showing another process step of producing the drilled body.

FIG. 5 is a schematic cross-sectional view showing another process step in producing the drilled body.

FIG. 6 is a schematic cross-sectional view showing another process step in producing the drilled body.

FIG. 7 is a schematic cross-sectional view showing another process step of producing the drilled body.

FIG. 8 is a schematic cross-sectional view of a main part of a drilled body having holes drilled according to a conventional drilling method.

[Explanation of symbols]

1 ... substrate, 2, 2a, 2b, 2c ... conductive layer (copper foil),
3, 3a, 3b, 3c ... oxide film (black matter), 4, 4a,
4b: insulating layer, 5, 11, 11 ': laser beam, 6, 6
a, 6b, 6c, 6a ', 6b', 6c ', 12 ... holes,
7a, 7b, 7c: Upper conductive layer

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 3/00 H05K 3/00 K N

Claims (14)

[Claims] A step of performing a reflection reduction process on a lower layer of a predetermined shape provided on the substrate; a step of forming a coating layer on the lower layer; and forming the coating layer on the lower layer on which the reflection reduction processing is performed. Forming a hole that reaches the lower layer through a step of irradiating the coating layer with a beam. 2. A blackening process is performed on a conductive layer having a predetermined shape provided on the base, and then an insulating layer is formed on the conductive layer, and the insulating layer is irradiated with a light beam to form the insulating layer. 2. The hole processing method according to claim 1, wherein a fine hole having a predetermined shape reaching the conductive layer via an insulating layer is formed. 3. The hole processing method according to claim 2, wherein a fine hole having a predetermined shape reaching the conductive layer via the insulating layer and the layer formed by the blackening treatment is formed as the hole. 4. The hole forming method according to claim 2, wherein the copper foil provided as the conductive layer on the wiring board is subjected to an oxidation treatment as the blackening treatment. 5. The method according to claim 4, wherein the surface of the copper foil is oxidized by a chemical treatment solution. 6. A laser beam as the light beam,
The hole processing method according to claim 2, wherein the holes are formed in the insulating layer by heat generated by the irradiation of the laser light. 7. The hole processing according to claim 2, wherein the hole is a connection hole for connecting predetermined conductive layers in a multilayer printed wiring board having a laminated structure of the conductive layer and the insulating layer. Method. 8. The hole processing method according to claim 7, wherein an upper conductive layer is provided so as to connect the conductive layer through the connection hole, and the upper conductive layer is applied to manufacture a multilayer printed wiring board. 9. A coating having a coating layer on a lower layer of a predetermined shape provided on a substrate, wherein a hole reaching the lower layer is formed in the coating layer, and between the lower layer and the coating layer, A perforated body, wherein a layer is formed by the lower layer reflection reduction process. 10. An insulating layer is provided on a conductive layer having a predetermined shape provided on the base, and a hole reaching the conductive layer through the insulating layer is formed, and the conductive layer and the insulating layer are formed. The drilled body according to claim 9, wherein a layer formed by blackening of the conductive layer is formed between the hole and the conductive layer. 11. The drilled body according to claim 10, wherein fine holes having a predetermined shape reaching the conductive layer via the insulating layer and the layer formed by the blackening treatment are formed as the holes. 12. The perforated body according to claim 10, wherein the insulating layer is a copper foil provided on a wiring board, and the copper foil has been subjected to an oxidation treatment as the blackening treatment. . 13. The connection hole for connecting predetermined conductive layers in a multilayer printed wiring board having a laminated structure of the conductive layer and the insulating layer.
The drilled body described in 1. 14. The drilled body according to claim 13, wherein an upper conductive layer connected to the conductive layer via the connection hole is provided to constitute a multilayer printed wiring board.