JPH08255981A - Formation method of circuit board and circuit board - Google Patents

Abstract

PURPOSE: To obtain a formation method in which a fine pattern can be formed and in which a glass substrate is endowed wit thermal conductivity by a method wherein a light blocking film is formed on the surface of the glass substrate, photosensitive resin is applied, patterned and hardened, an insulation layer is formed and a circuit is formed on the insulation layer. CONSTITUTION: A light blocking film 2 composed of Al is formed on the whole face of a glass substrate 1 by a DC sputtering operation, and the light blocking film 2 is coated with photosensitive resin composed of polyimide. Then, an insulation layer 5 comprising a prescribed pattern is formed via a glass mask. Then, a metal layer for a circuit is formed on the insulating layer 5. In addition, the metal layer for the circuit is coated with a photoresist, and the photoresist is formed via a precuring treatment, a UV ray exposure operation, a developing treatment and the like. Then, by making use of the photoresist as a mask. an etching treatment is executed, and a circuit 6 is formed. When the multiple reflection of UV rays is prevented by the light blocking film 2, a fine pattern can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board forming method and a circuit board. More specifically, the present invention makes it possible to form a fine pattern of a photosensitive material when a glass substrate is used as a substrate for supporting a circuit board, and in addition, the circuit board has improved heat dissipation (heat conductivity). The present invention relates to a forming method and a circuit board.

[0002]

2. Description of the Related Art With the recent miniaturization and weight reduction of electronic devices, the mounting method represented by the multilayered printed circuit board and the surface mounting of electronic components has been increased. Also,
Higher functionality and downsizing of electronic components typified by ICs, and higher functionality and downsizing of circuit boards typified by multi-chip modules (MCM) are also in progress.

In particular, with respect to the circuit board, the thinning and high functionality of the multi-layer wiring method and the narrow pitch wiring method are being advanced. In order to reduce the thickness of such a circuit board, a ceramic substrate such as aluminum nitride or alumina (aluminum oxide), a metal substrate such as Al or Cu, and an insulating layer (several μm thick) on a smooth plate material such as a glass substrate. A circuit board for high-density mounting of a multi-layer wiring system in which circuits (thickness of several μm) are alternately laminated has attracted attention.

In the manufacturing process of the circuit board described above, the exposure of the photosensitive material with UV (ultraviolet) light is required when forming the fine via holes and wirings. Is an essential condition that the warp is small (several tens of μm or less). From this point of view, a silicon wafer or a glass substrate is suitable as the substrate to be used, and a glass substrate is more suitable from the viewpoint of cost.

A circuit is formed on the glass substrate as follows. First, a photosensitive material (photosensitive polyimide, photoresist, or the like) for forming an insulating layer is applied on a glass substrate. Next, the photosensitive material is patterned,
At this time, an insulating layer is formed by exposing the photosensitive material to UV light through a glass mask to cause a difference in solubility in the photosensitive material and patterning it through a developing process. Next, a circuit metal is laminated on the insulating layer and patterned to form a circuit. In addition, the formation of the insulating layer and the circuit,
Repeatedly, a multilayer circuit board is formed.

[0006]

However, in the above-mentioned conventional method, since UV light is reflected multiple times between the upper surface and the lower surface of the glass substrate, the UV light of the photosensitive material should not be originally irradiated. UV light is radiated to the site, and as a result, a difference in solubility of the photosensitive material is less likely to occur, which causes a problem that a fine pattern cannot be formed. Therefore, in the field of holograms and liquid crystal displays, multiple reflection is prevented by forming a UV light antireflection film on the lower surface side of the glass substrate and absorbing UV light on the lower surface of the glass substrate.

Further, the glass substrate has a problem that it is inferior in heat dissipation (heat conductivity) to other substrate materials.
In view of the above problems, the inventors of the present invention have earnestly studied,
Finding a circuit board forming method and a circuit board which prevent multiple reflection of UV light when using a glass substrate, enable formation of fine patterns, and improve heat dissipation (heat conductivity) of the glass substrate Invented.

[0008]

Thus, according to the present invention, the step of forming a film for blocking light on the surface of the glass substrate, applying a photosensitive resin on the film, patterning,
It consists of a step of forming an insulating layer by hardening, a step of forming a circuit by laminating a circuit metal on the insulating layer and patterning, and a step of forming an insulating layer and a step of forming a circuit in this order. A method for forming a circuit board is provided, which is performed at least once.

Further, according to the present invention, there is also provided a circuit board in which a film having good thermal conductivity and an electronic component formed on the circuit board are connected via a thermal via. The glass substrate used in the present invention is not particularly limited, and a known glass substrate can be used. It is preferable that the surface of the glass substrate is treated with a pear satin, because the adhesion (anchor effect) with a film that blocks light (hereinafter referred to as a light blocking film) is improved. In addition, in the pear-skin formation treatment, Ra = 10 to 50 nm is particularly preferable as the surface roughness. In addition, when using the light blocking film having excellent adhesion to the glass substrate, it is not necessary to carry out the pear surface treatment.

Next, the above-mentioned glass substrate is mainly coated with isopropyl alcohol (IP) for the purpose of removing organic substances on the surface.
A), using an organic solvent such as ethanol, methanol, acetone, trichloroethylene, trichloroethane, methylene chloride, or an alkaline aqueous solution such as phosphate, silicate, sodium carbonate, sodium hydroxide, etc. Is preferred. Further, it is more preferable to apply ultrasonic waves during the cleaning treatment because the cleaning efficiency is improved.

After that, a light blocking film is formed on the surface of the glass substrate. The light blocking film may be formed on one surface of the glass substrate as shown in FIG. 2, or may be formed so as to cover the entire surface of the glass substrate as shown in FIG. 2 and 3, 1 means a glass substrate and 2 means a light blocking film. By thus forming the light blocking film on the glass substrate, it is possible to prevent multiple reflection of UV light when patterning the photosensitive resin. Further, when the light blocking film is a film having good thermal conductivity, the heat dissipation property (heat conductivity) of the circuit board can be improved.
The material of the light blocking film that can be used in the present invention is not particularly limited as long as it can block the transmission of UV light. Here, the light blocking film is
It is particularly preferably made of metal. Specifically, the light blocking film is made of Ti, Cr, Al, Ni, W, Mo, Ta and C.
It is preferable to include at least one metal composed of u.
Further, Fe, Au, etc. capable of forming an alloy with the above metals can be included. Of these, Ti, Al and Cr are particularly preferable. In addition, the thickness of the light blocking film is U when patterning.
Although it depends on the wavelength of the V light and the type of the light blocking film, it is preferably at least 3 μm or more, and particularly preferably 3 to 10 μm. When the thickness is 3 μm or more, in addition to preventing multiple reflection of UV light, heat dissipation (heat conductivity) can be further improved.

The light blocking film is formed by chemical vapor deposition (CVD),
It can be formed by a vacuum film forming method such as vacuum deposition, ion plating or sputtering, or a wet plating method such as electroplating or electroless plating. Here, a vacuum film forming method is preferable for forming the light blocking film on one surface of the glass substrate, and a wet plating method is preferable for forming the light blocking film so as to cover the entire surface of the glass substrate.

On the glass substrate on which the light blocking film is formed as described above, an insulating layer and a circuit having a desired pattern are laminated to form a multilayer wiring. Here, a photosensitive resin such as a polyimide resin, an epoxy resin, or a benzocyclobutene (BCB) resin can be used for forming the insulating layer.
Further, the thickness of the insulating layer is preferably 10 to 20 μm. 10
If it is smaller than μm, sufficient insulation cannot be obtained, which is not preferable, and if it is larger than 20 μm, it takes a long time to manufacture and cannot meet the demand for thinning.

The method for laminating the insulating layer is not particularly limited, and any known method can be used. For example, a spin coater, a roller coater, a dip coater, a spray is used for coating, a pre-cure step is performed, and a glass is applied. The insulating layer having a desired pattern can be laminated by performing a UV exposure process through a mask and performing a development and a full cure process.
In the present invention, since the light blocking film is formed on the glass substrate, it is possible to prevent the UV light from being multiple-reflected and being applied to a region that should not be originally applied during the UV exposure processing. Therefore, the diameter of the via hole formed in the insulating layer can be reduced to about 1/3 of that in the case where the light blocking film is not provided.

On the other hand, the circuit can be formed by laminating a known circuit metal on the insulating layer and patterning it with a photoresist or the like. By this laminating step, the circuit metal is filled also in the via hole formed in the insulating layer. Examples of the circuit metal include A
1, Cu, Au, Mo, W and the like, and alloys thereof can also be used. It is also possible to add Si or the like in a few%. Al and Cu are particularly preferable as the circuit metal. The thickness of the circuit depends on the type of the underlying insulating layer, but is preferably 1 to 5 μm. If smaller than 1 μm,
The resistance of the circuit increases due to the influence of the insulating layer.

The method for laminating the circuit metal is not particularly limited, and any known method can be used. For example, C
It can be formed by a vacuum film forming method such as VD, vacuum deposition, ion plating, sputtering, or a wet plating method. After the circuit metal is laminated, a photoresist is applied for patterning, an etching mask is formed by forming a desired pattern, and the circuit metal is subjected to etching treatment. The etching method is not particularly limited, and a known method can be used. For example, wet etching using an etchant such as cupric chloride, ferric chloride, hydrogen peroxide / sulfuric acid, ammonium persulfate, sodium persulfate and potassium persulfate can be mentioned.

By forming a plurality of layers of the photosensitive resin and the circuit metal alternately while patterning, a multilayer circuit including an insulating layer and a circuit can be formed. Further, the circuit metal is exposed on the uppermost layer, and the electronic component is placed and connected to the circuit metal. Examples of electronic components that can be used in the present invention include electronic components that are normally used for circuit boards such as IC chips, LSI chips, resistor chips, and capacitor chips.

Further, according to the present invention, it is possible to provide a circuit board in which a film having good thermal conductivity and an electronic component formed on the circuit board are connected via a thermal via.
The heat generated in the electronic component can be released to the film having good thermal conductivity via the thermal via. For example, when the thermal via is provided, it depends on the material, shape and size of the thermal via, but it is about 1
The heat can be reduced by about 0 ° C. This thermal via is preferably made of the same material as the circuit metal,
It can be formed at the same time as the insulating layer and the circuit.

[0019]

The method of forming a circuit board of the present invention comprises the steps of forming a light blocking film on the surface of a glass substrate, applying a photosensitive resin on the film, patterning, and curing to form an insulating layer. Since a circuit metal is laminated on the insulating layer and patterned to form a circuit, the step of forming the insulating layer and the step of forming the circuit are performed at least once in this order. A fine pattern can be formed, and heat dissipation (heat conductivity) to the glass substrate is imparted. The reason for this is as follows.

That is, the glass substrate has a thickness and UV
Allows light to pass through. Therefore, in the case of a glass substrate having no light blocking film, UV light is reflected on the lower surface of the glass substrate as shown in FIG. This reflected light is multiple-reflected between the upper surface and the lower surface of the glass substrate, and UV light is irradiated to the portion of the photosensitive resin that should not be originally irradiated with UV light. The UV light accelerates the photoreaction of the photosensitive resin, and an insulating film is formed on an unnecessary portion, making it difficult to form a fine pattern. On the other hand, in the present invention, since the light blocking film is formed on the glass substrate, as shown in FIG. 4, multiple reflection of UV light does not occur and a desired fine pattern can be formed. In addition, 4 in FIG. 4 and FIG. 9 means a mask.

Further, the light blocking film is formed by vacuum deposition, ion plating, sputtering, chemical vapor deposition (CV).
D), the light blocking film can be easily formed by forming it by the wet plating method. Further, the light blocking film is made of Ti, C
By containing at least one element consisting of r, Al, Ni, W, Mo, Ta and Cu, the UV light shielding property and the heat dissipation property of the glass substrate are improved.

Also provided is a circuit board having a finer circuit and improved heat dissipation (thermal conductivity) as compared with a circuit board using a glass substrate having no light blocking film. Further, in the circuit board, since the film having good thermal conductivity and the electronic parts formed on the circuit board are connected through the thermal vias, heat generated in the electronic parts formed on the uppermost layer is generated. Since it is easily transferred to the metal film, a circuit board excellent in heat dissipation (heat conductivity) is provided.

[0023]

【Example】

Example FIG. 1 is a sectional view of an example of the present invention, in which a multilayer circuit is formed on a glass substrate on which a light blocking film is formed. In the figure, 1 is a glass substrate, 2 is a light blocking film, 5 is an insulating layer, 6 is a circuit, 7 is a thermal via, 8 is a via hole, and 9 is an IC chip. Below, FIG.
The circuit board forming method of FIG. 1 will be described in more detail with reference to FIGS.

First, in order to improve the adhesion between the light blocking film and the glass substrate, the glass substrate 1 was dipped in a strong alkaline solution (NaOH) to make the surface of the glass substrate 1 a satin finish (surface roughness). Ra = 10 to 50 nm). A cleaning treatment was performed using IPA which is an organic solvent, mainly for removing (degreasing) organic substances on the surface of the glass substrate 1 (FIGS. 5A and 5B).

Next, the light blocking film 2 made of Al was formed on the entire surface of the glass substrate 1 by DC sputtering so as to have a thickness of 5 μm. The substrate temperature during formation was room temperature (Fig. 5).
(C)). Then, a photosensitive resin 3 made of polyimide was applied on the light blocking film 2 (FIG. 6A). After the photosensitive resin 3 was pre-cured, UV exposure was applied through the glass mask 4, and after development and full curing steps, an insulating layer 5 having a desired pattern and a thickness of 5 μm was formed (see FIG. 6 ( b) and FIG. 7 (a)). At this time, fine thermal vias 7 (or via holes 8) having a minimum diameter of 10 μm could be formed.

Then, a circuit metal (Al-Si alloy) 11 having a thickness of 3 μm was formed on the insulating layer 5 by sputtering (FIG. 7B). Photoresist is applied on the circuit metal 11, and pre-cure treatment, UV light exposure, development treatment,
A photoresist 10 was formed into a desired pattern through a full cure process (FIGS. 7C and 8A). Next, using the photoresist 10 as an etching mask, etching was performed to form the circuit 6 having a desired pattern (FIG. 8B). Here, in the etching treatment, a mixed acid solution containing phosphoric acid as a main component was used as a solution for etching.

Thereafter, the steps of FIGS. 6 (a) to 8 (b) are repeated to mount and connect the IC chip 9 as an electronic component to form a circuit board having the thermal via 7 as shown in FIG. I was able to get it. When the heat generated from the IC chip 9 is transferred to the light blocking film 2 through the thermal vias 7 of the obtained circuit board and is radiated, the temperature of the IC chip 9 becomes about 10 ° C. lower than the compensation temperature of the chip. I was able to.

Comparative Example A circuit board was formed in the same manner as in the above example except that the light blocking film 2 was not formed. The minimum diameter of the via hole 8 of the obtained circuit board was 30 μm.

[0029]

According to the method of forming a circuit board of the present invention, a step of forming a light blocking film on a glass substrate, a step of applying a photosensitive resin on the film, patterning and curing the film to form an insulating layer. , A step of forming a circuit by laminating a circuit metal on the insulating layer and patterning,
Since the step of forming the insulating layer and the step of forming the circuit are performed at least once in this order, a fine pattern can be formed, and heat dissipation (heat conductivity) can be imparted to the glass substrate. You can

The light blocking film is formed by vacuum vapor deposition, ion plating, sputtering, chemical vapor deposition (CV).
D), the light blocking film can be easily formed by forming by the wet plating method. Furthermore, the light blocking film
By containing at least one element consisting of Ti, Cr, Al, Ni, W, Mo, Ta and Cu, it is possible to realize the shielding of UV light and the improvement of heat dissipation of the glass substrate.

Further, it is possible to provide a circuit board having a finer circuit as compared with a circuit board using a glass substrate having no light blocking film. Further, since the circuit board has a structure in which the film having good thermal conductivity and the electronic parts formed on the circuit board are connected via the thermal vias, the electronic parts formed on the uppermost layer Since the generated heat is easily transferred to the film having good thermal conductivity, it is possible to provide a circuit board excellent in heat dissipation (thermal conductivity).

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a circuit board of the present invention.

FIG. 2 is an example of a glass substrate coated with a light blocking film in the method for forming a circuit board of the present invention.

FIG. 3 is an example of a glass substrate coated with a light blocking film in the method for forming a circuit board of the present invention.

FIG. 4 is a schematic diagram showing the behavior of UV light during UV light irradiation in the circuit board forming method of the present invention.

FIG. 5 is a schematic process diagram of a circuit board forming method of the present invention.

FIG. 6 is a schematic process diagram of a circuit board forming method of the present invention.

FIG. 7 is a schematic process diagram of a circuit board forming method of the present invention.

FIG. 8 is a schematic process diagram of a circuit board forming method of the present invention.

FIG. 9 is a schematic diagram showing the behavior of UV light during UV light irradiation in the conventional circuit board forming method.

[Explanation of symbols]

 1 Glass Substrate 2 Light Blocking Film 3 Photosensitive Resin 4 Mask 5 Insulating Layer 6 Circuit 7 Thermal Via 8 Via Hole 9 IC Chip 10 Photoresist 11 Circuit Metal

Claims (2)

[Claims] 1. A step of forming a film for blocking light on a surface of a glass substrate, a step of applying a photosensitive resin on the film to form an insulating layer by patterning and curing, and a circuit on the insulating layer. A method for forming a circuit board, comprising the steps of forming a circuit by laminating and patterning a working metal, and performing the step of forming an insulating layer and the step of forming a circuit at least once in this order. 2. A circuit board in which a film having good thermal conductivity and an electronic component formed on the circuit board are connected via a thermal via.