JP2002290036A - Method of manufacturing wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which is improved in durability by enhancing the adhesion of a wiring circuit layer to an insulating sheet when the wiring circuit layer is formed on the surface of the thermosetting resin-containing insulating sheet by transfer. SOLUTION: A thermosetting resin-containing uncured or semi-cured insulating sheet 1 is formed, a metal foil is bonded on the surface of a prescribed transfer film 5 and then subjected to etching for the formation of a wiring circuit layer 4, and then the wiring circuit layer 4 is transferred onto the surface of the insulating sheet 1. Before the wiring circuit layer 4 formed on the surface of the transfer film 5 is transferred onto the surface of the insulating sheet 1, the surface of the wiring circuit layer 4 which is to come into contact with the insulating sheet 1 is subjected to plasma processing or subjected to a surface- roughening process before plasma processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, for a motherboard of a large computer called a mainframe, a substrate for mounting a semiconductor element, or a package for storing a semiconductor element. And a method for manufacturing a wiring board having a wiring circuit layer.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size.
In recent years, with the development of portable information terminals and the spread of so-called mobile computing in which a computer is carried and operated, there is a tendency that a smaller, thinner, and higher-definition multilayer wiring board is required.

[0003] Further, electronic devices that require high-speed operation, such as communication devices, have been widely used. The requirement for high-speed operation includes various requirements such as accurate switching of high-frequency signals. In order to cope with such electronic devices, a multilayer printed wiring board suitable for high-speed operation is required.

In order to perform high-speed operation, it is necessary to reduce the length of wiring and the time required for transmitting an electric signal. In order to reduce the length of the wiring, there is a tendency for a small, thin, and high-definition multilayer wiring substrate in which the width of the wiring is reduced and the gap between the wirings is reduced. In order to meet such a demand for high-density wiring, various methods for manufacturing a multilayer wiring board have been proposed.

For example, after a metal foil is adhered to the surface of a sheet containing a thermosetting resin, resist coating / exposure / development /
A method of forming a wiring circuit layer of a predetermined pattern by an etching / resist removing process and laminating them, and in forming a multilayer, a photosensitive resin is applied to a surface of a core substrate, and exposed and developed to form a via hole. And then
A plating layer of copper or the like is formed on the entire surface of the insulating layer including the inner wall of the via hole, and then a photosensitive circuit is applied to the surface of the plating layer, followed by exposure / development / etching / resist removal to form a wiring circuit layer. A so-called built-up method is also known in which the above-described steps are repeated as necessary to form a multilayer wiring layer by repeatedly forming an insulating layer and a wiring circuit layer.

However, in the above-described method, forming a wiring circuit layer through a process such as exposure / development on a metal foil or a plating layer formed on the surface of an insulating sheet requires an increased number of steps. For development, etching, etc.
There is a problem that the insulating sheet is likely to undergo a chemical change because the insulating sheet comes into contact with the chemical.

Therefore, a metal foil is adhered to a predetermined transfer film, an etching process is performed to form a wiring circuit layer, and this is transferred and formed on the surface of an uncured insulating sheet. It has also been proposed to form

[0008]

However, the insulating sheet containing a thermosetting resin or the like and the wiring circuit layer made of metal foil are not sufficient in terms of adhesiveness, so that a fine wiring pattern is transferred. Insulation reliability and continuity reliability, such as when micro patterns are left on the transfer film side or in a resistance test after completion of the wiring board, the wiring circuit layer made of copper foil is peeled off from the insulating sheet. There was a problem in terms of durability that could not be maintained.

Accordingly, the present invention provides a method for manufacturing a wiring board having improved durability by improving the adhesion of the wiring circuit layer to an insulating sheet when the wiring circuit layer is formed by the above-described transfer. The purpose is to provide.

[0010]

Means for Solving the Problems As a result of intensive studies on the above objects, the present inventor has found that the transfer film surface is not transferred onto the insulating sheet containing the thermosetting resin before the transfer circuit layer is formed. It has been found that the plasma treatment is applied to the wiring circuit layer made of metal foil formed on the insulating sheet to improve the adhesion between the insulating sheet and the wiring circuit layer, and the present invention has been accomplished.

That is, the method of manufacturing a wiring board according to the present invention comprises the steps of: preparing an uncured or semi-cured insulating sheet containing at least a thermosetting resin; and bonding a metal foil to a predetermined transfer film surface. By etching the metal foil to form a predetermined wiring circuit layer, and after laminating and pressing a transfer film having the wiring circuit layer formed on the surface of the insulating sheet, peeling off the transfer film, A step of transferring and forming a wiring circuit layer on the surface of an insulating sheet; and a step of heating and curing the insulating sheet on which the wiring circuit layer is formed. Before the transfer to the insulating sheet, the surface of the wiring circuit layer in contact with the insulating sheet is subjected to a plasma treatment.

In this plasma treatment, the metal foil area 1c
It is suitably performed for 0.05 to 3 seconds per m < ² >. Further, before the plasma treatment, the surface of the wiring circuit layer which is in contact with the insulating sheet is subjected to a roughening treatment to further enhance the adhesion.

According to the present invention, a wiring circuit layer made of a metal foil patterned by etching or the like is transferred to an uncured or semi-cured insulating sheet to form a wiring circuit layer on the transfer film as described above. By performing plasma treatment on the surface of the wiring circuit layer before transfer,
The organic material on the surface of the metal foil is removed and washed, and the low-activity layer to which the gas is adsorbed is decomposed to expose the high-activity metal oxide layer on the surface. As a result of improving the wettability of the organic resin in the low viscosity component, the adhesion between the wiring circuit layer made of metal foil and the insulating sheet can be improved. In addition, after roughening the surface of the wiring circuit layer made of metal foil, plasma treatment is performed to further improve the adhesion. As a result, it is possible to prevent the occurrence of transfer failure, improve the yield in manufacturing the wiring board, and increase the durability of the wiring board.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a multilayer wiring board according to the present invention will be described with reference to the process chart of FIG. In FIG. 1, first, an insulating sheet 1 containing a thermosetting resin is prepared, and a through hole 2 for forming a via-hole conductor is formed in the insulating sheet 1 by a punching method, laser processing, plasma etching, or the like. (A). Then, the via-hole conductor 3 is formed by filling the through-hole 2 with a conductor paste (b).

Next, a wiring circuit layer 4 is formed on the surface of the insulating sheet 1. According to the present invention, the wiring circuit layer 4
Is formed by a transfer method. According to the transfer method, after a metal foil is bonded to the surface of the transfer film 5, a mirror image pattern of the wiring circuit layer 4 is formed by resist printing / etching or the like (c).

According to the present invention, the wiring circuit layer 4 formed on the surface of the transfer film 5 is subjected to plasma processing. This plasma treatment is performed by air, oxygen, argon, CF
_And a plasma source of high frequency (13.56 MHz) to microwave (2.45 GHz) at a plasma temperature of 20 ° C. to 80 ° C.
It is appropriate to carry out at Torr to 760 Torr (normal pressure). The plasma treatment is suitably performed for 0.05 to 3 seconds per 1 cm ^{2 of} metal foil area. By this plasma treatment, organic substances on the metal foil surface are removed and washed, and the low-activity gas adsorption layer is decomposed and the high-activity oxide layer is exposed on the surface, so that it is easily wetted by the low-viscosity component of the resin. Thus, the adhesion of the metal foil to the insulating sheet can be improved.

This plasma treatment can be applied to the side of the metal foil on which the circuit pattern is not formed, which is in contact with the insulating sheet. Since the surface state returns to the state before the plasma treatment due to the contact with the substrate, it is necessary to perform the operation before the transfer to the insulating sheet after the formation of the circuit pattern.

The plasma processing is performed on the wiring circuit layer 4.
0.05 to 3 seconds per 1 cm ² of the metal foil area of
It is suitably performed for 08 to 2 seconds. This is because if it is shorter than 0.05 seconds, it is difficult to obtain a sufficient plasma processing effect,
If the time is longer than 3 seconds, the adhesive component of the transfer film to the copper foil deteriorates.

Further, according to the present invention, it is desirable to roughen the surface of the wiring circuit layer 4 which is in contact with the insulating sheet 1 before performing the above-mentioned plasma processing, and particularly the surface roughness Rz is 2.0 μm or more. It is appropriate to make Then, by performing the plasma treatment thereafter, the contact area of the wiring circuit layer 4 with the insulating sheet 1 is increased. As a result, the activation by the plasma treatment can be further improved, and the adhesion with the insulating sheet 1 can be improved. .

In the formation of the wiring circuit layer 4 by the transfer method, since the formation of the insulating sheet 1 and the formation of the wiring circuit layer 4 can be performed simultaneously in parallel, the process can be shortened. .

Next, the transfer film 5 on which the wiring circuit layer 4 is formed is laminated and pressure-bonded while positioning the transfer film 5 on the insulating sheet 1, and then the transfer film 5 is peeled off so that the wiring circuit layer 4 is placed on the surface of the insulating sheet 1. Transferred to the wiring sheet a
(E). At this time, the lamination pressure bonding
It is appropriate to carry out under the condition of 0.5 MPa or more and 80 to 150 ° C.

Next, after positioning and laminating a plurality of wiring sheets a, b and c produced as described above (f),
By heating at a curing temperature of 150 to 300 ° C. to completely cure the organic resin of the insulating sheet 1, the multilayer wiring board A can be manufactured (g).

The insulating sheet 1 used in the manufacturing method of the present invention contains a thermosetting resin. For example, a thermosetting resin or a composition comprising a thermosetting resin and an inorganic filler is kneaded with a kneader or a kneader. After sufficiently mixing by means such as a three-roll mill, and forming this into a sheet by a rolling method, an extrusion method, an injection method, a doctor blade method or the like, a sheet obtained by semi-curing an organic resin is used. For semi-curing, heating may be performed to a temperature slightly lower than a temperature sufficient for complete solidification. Alternatively, a commercially available prepreg may be used.

As the inorganic filler, Si is used.
O ₂ , Al ₂ O ₃ , AlN and the like are suitable, and as the filler, a substantially spherical powder having an average particle diameter of 20 μm or less, particularly 10 μm or less, and optimally 7 μm or less is used. The inorganic filler is mixed in a range of 70:30 to 20:80 in volume ratio of organic resin: inorganic filler.

The organic resin constituting the insulating sheet 1 is preferably a resin such as PPE (polyphenylene ether), BT resin (bismaleimide triazine), epoxy resin, polyimide resin, fluororesin, phenol resin, and polyaminobismaleimide. It is desirable that the thickness of the insulating sheet 1 is 10 to 300 μm, particularly 40 to 100 μm.

The conductor paste to be filled into the through-hole 2 is prepared by adding a resin component such as epoxy or cellulose to a metal powder and kneading with a solvent such as butyl acetate, and is used in the conductor paste. The metal powder is desirably made of at least one low-resistance metal of copper, aluminum, silver, and gold. If desired, after filling the via holes, heat treatment may be performed at 60 to 140 ° C. to decompose, volatilize and remove the solvent and resin components in the paste. Further, the wiring circuit layer 4 is made of copper,
A metal such as aluminum is preferably used.

In the above-described method for manufacturing a wiring board, a method in which printed wiring circuit layers are individually transferred onto a plurality of insulating sheets is laminated and cured together. For example, after the insulating sheet is attached to the surface of the core substrate on which the wiring circuit layer is formed, the wiring circuit layer is transferred and formed on the surface of the insulating sheet in the same manner as described above, and the insulating sheet and the By repeating the formation of the wiring circuit layer, it is multilayered, and after forming each wiring circuit layer,
Alternatively, the present invention can also be applied to a so-called build-up method in which heat treatment is performed at once to thermally cure the insulating sheet.

[0028]

EXAMPLES The following experiments were conducted to confirm the effects of the plasma processing in the present invention. First, as an insulating sheet, a thermosetting polyphenylene ether resin (PPE) was used for 50% by volume of glass cloth woven with E glass.
Resin) A prepreg (120 μm thick) was prepared by impregnating a glass cloth with a PPE resin at a ratio of 50% by volume. Thereafter, the insulating sheet was semi-cured by heat treatment at 150 ° C. for 1 minute.

On the other hand, a 12 μm thick electrolytic copper foil formed by electrolytic plating was adhered to the surface of a 35 μm thick polyethylene terephthalate (PET) transfer film via an acrylic adhesive.

Then, a photosensitive resist was applied to the surface of the copper foil and exposed through a glass mask to form a wiring pattern, which was removed by etching to form a wiring circuit layer on the surface of the insulating sheet. The pattern of the wiring circuit layer was a pattern having an effective area having a line width of 3 mm and a length of 60 mm.

Then, the wiring circuit layer formed on the surface of the transfer film is appropriately subjected to a roughening treatment or a microwave (2.45 GHz) at 760 Torr using oxygen gas.
z) Plasma treatment was performed with plasma (plasma temperature 50 ° C.). The roughening treatment was performed by spraying a 10% by weight formic acid solution onto the surface of the wiring circuit layer to roughen the surface. The surface roughness after the treatment was measured by an atomic force microscope (AFM).
The plasma treatment was performed under the conditions shown in Table 1.

Thereafter, the wiring circuit layer was positioned on the insulating sheet, laminated and pressed at 120 ° C. and 4.9 MPa, and then the transfer film was peeled off to transfer and form the wiring circuit layer on the surface of the insulating sheet. Then, the insulating sheet to which the wiring circuit layer was transferred was heated at 240 ° C. for 2 hours and completely thermally cured to obtain a single-layer wiring board.

Effective area of wiring circuit layer (3 × 60 mm)
The edge of the outer pattern was peeled off, and the peeled portion was pulled vertically, and the tensile strength when the wiring circuit layer in the effective area was peeled off from the insulating sheet was evaluated as the adhesive strength of the wiring circuit layer. The destruction mode was observed by observing the separated surface of the separated wiring circuit layer. The results are shown in Table 1.

[0034]

[Table 1]

As is clear from the results in Table 1, the adhesion strength of the wiring circuit layer to the insulating sheet is improved by performing the plasma treatment.
It was confirmed that the adhesion strength was further increased.

[0036]

As described above, according to the present invention, when a wiring circuit layer is formed by transfer, the adhesion of the wiring circuit layer to the insulating sheet is improved, and a wiring board having excellent durability is manufactured. be able to.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a method of manufacturing a wiring board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation sheet 2 Through-hole 3 Via-hole conductor 4 Wiring circuit layer 5 Transfer film

Claims (3)

[Claims] 1. A step of producing an uncured or semi-cured insulating sheet containing at least a thermosetting resin, and after adhering a metal foil to a surface of a predetermined transfer film, etching the metal foil to a predetermined level. Forming a wiring circuit layer, and laminating and pressing a transfer film having the wiring circuit layer formed on the surface of the insulating sheet, and then peeling off the transfer film to transfer and form the wiring circuit layer to the surface of the insulating sheet. And a step of heating and curing the insulating sheet on which the wiring circuit layer is formed. In the method for manufacturing a wiring board, the wiring circuit before transferring the wiring circuit layer on the transfer film surface to the insulating sheet is provided. A method for manufacturing a wiring board, comprising a step of performing a plasma treatment on a surface of a layer in contact with an insulating sheet. 2. The method according to claim 1, wherein the plasma treatment is performed by using a metal foil area of 1 cm ^2.
2. The method according to claim 1, wherein the process is performed for 0.05 to 3 seconds. 3. The method for manufacturing a wiring board according to claim 1, further comprising a step of roughening a surface of the wiring circuit layer in contact with the insulating sheet before the plasma processing.