JPH0412638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive-coated copper foil that is bonded to a copper-clad laminate mainly used as a printed wiring board.

Copper-clad laminates are widely used as printed wiring boards by etching the copper foil bonded to the surface, but this type of laminate is made of paper phenolic resin laminates, paper epoxy resin laminates, and polyester laminates. It is formed by bonding a so-called adhesive-coated copper foil whose surface is coated with an adhesive onto a substrate such as a plate. In order to bond the above-mentioned substrate and copper foil with adhesive, a hot press method is generally used, and for example, pressure bonding is performed at a temperature of 170°C and a pressure of 100 kg/cm ² for about 2 hours. As a result, the base and the adhesive-coated copper foil are bonded together with sufficient adhesive strength.

However, the above-mentioned hot press method requires a huge amount of equipment, which increases manufacturing costs due to equipment investment, and the hot press method is a batch system with limited processing capacity. However, productivity has become extremely poor.

Therefore, conventionally, attempts have been made to continuously bond adhesive-coated copper foils using hot rolls to improve productivity, but the butyral/phenol adhesives currently used are Heating with the hot roll does not provide sufficient adhesion, and the copper foil becomes lifted and wrinkled, resulting in extremely low reliability. It is also possible to use an adhesive that exhibits good adhesion when heated with a hot roll, but this type of adhesive generally has weak adhesion strength to copper foil and cannot be used for copper-clad laminates. No one is known that has the adhesive strength that can be obtained.

Therefore, the present invention was proposed in order to eliminate the drawbacks of the above-mentioned conventional methods, and it is possible to continuously bond to a substrate by a hot roll, and has sufficient adhesive strength. The purpose of the present invention is to provide adhesive-coated copper foil to be bonded.

As a result of intensive research, the inventors of the present invention discovered that an adhesive layer having a predetermined adhesive strength to the copper foil and an adhesive layer that exhibits adhesive properties by hot rolls are laminated on the copper foil. The present invention was completed by discovering that the adhesion with copper foil was good and hot roll lamination was possible. The first adhesive layer having the above peel strength and the second adhesive layer having thermal activation are sequentially laminated.

That is, as shown in FIG. 1, the adhesive-coated copper foil constructed according to the present invention is formed by first coating a first adhesive layer 2 with good adhesion to the copper foil on a copper foil 1. Furthermore, a thermally active second adhesive layer 3 is formed by coating on the first adhesive layer 2. To form each of these adhesive layers 2 and 3, for example, after coating liquid adhesive 5 or 6 using a roll 4 as shown in FIG. Or 130℃,
A method of heating for 1 minute is used.

The first adhesive layer 2 has a
An adhesive having a peel strength of 1.5 kg/cm or more is used, and such adhesives include butyral/phenol adhesives and epoxy/nitrile adhesives. For example, resol type phenol
By dissolving 30 parts by weight of polyvinyl butyral, 70 parts by weight of polyvinyl butyral, and 1 part by weight of epoxy resin (1001 manufactured by Ciel Chemical Co., Ltd.) in 200 parts by weight of methyl ethyl ketone, a suitable material having a peel strength of about 2.3 kg/cm with respect to copper foil 1 is obtained. An adhesive is obtained. By the way, the above-mentioned peel strength indicates the peel strength of the conductor (copper foil) of the printed wiring board, and its measurement method is defined in JIS C5012 8.1 according to the JIS standard. That is, as shown in Figure 3, the width is 25
The width is 10±0.1mm and the length is at the center of the insulating plate 101 of mm.
Prepare a sample with 100 mm of copper foil 102 remaining, peel off one end of this copper foil 102 to an appropriate length, attach it to a support fitting (not shown), and then attach the tip of the peeled copper foil 102 to a suitable length. Grasp the copper foil with a grip (not shown) and peel it off by about 50 mm at a speed of 50 mm per minute in a direction where the pulling direction is perpendicular to the copper foil surface.The lowest value of the load during this time is determined as the peeling strength, It is expressed as peel strength in Kg/cm.

On the other hand, for the second adhesive layer 3, a so-called thermally activated adhesive is used, which becomes adhesive when heated to a temperature higher than the softening point by the heat of a hot roll, which will be described later, and becomes adhesive. Examples of suitable adhesives include epoxy/acrylic adhesives, epoxy/polyamide adhesives, and the like. For example, 30 parts by weight of acrylic rubber (manufactured by Teikoku Kagaku Co., Ltd.), brominated bisphenol
21 parts by weight, 21 parts by weight of cresol novolac epoxy, 28 parts by weight of polyvinylphenol and a catalyst,
100 parts by weight of methyl ethyl ketone, 100 parts by weight of toluene, and 200 parts by weight of ethyl alcohol dissolved in a mixed solvent to give a solid content of 25%, 100 parts by weight of acrylic rubber (manufactured by Teikoku Kagaku Co., Ltd.), and epoxy resin (made by Ciel Kagaku Co., Ltd.). 1001) 20 parts by weight and 0.15 parts by weight of undecimidazole to 50 parts by weight of methyl ethyl ketone
parts by weight and dissolved in 20 parts by weight of toluene,
It has the above-mentioned thermal activity and is suitable for use in the second adhesive layer 3.

As shown in FIG. 4, the adhesive-coated copper foil described above is easily roll-laminated to the substrate 10 using a pair of hot rolls 8 and 9, resulting in a copper-clad laminate with sufficient adhesive strength. It will be done. As the substrate 10, all kinds of substrate materials can be used, such as a paper phenolic resin laminate, a paper epoxy resin laminate, a glass epoxy resin substrate, an aluminum plate or a steel plate whose surface is coated with an insulating layer.

In addition, after the above roll lamination, 130℃, 2
Post-curing is performed for about 5 hours to further ensure the cured state of each of the adhesive layers 2 and 3. Further, it is preferable that the substrate 10 be heated in advance in order to drive out unreacted components and volatile components such as organic solvents remaining in the substrate 10.

As mentioned above, the adhesive-coated copper foil is easily laminated to the substrate 10 with the hot rolls 8 and 9 due to the thermal activation of the second adhesive layer 3, and
Due to the adhesive strength of the adhesive layer 2 to the copper foil 1, it is reliably joined to the base 10.

By the way, by using the above adhesive-coated copper foil in the multilayer wiring board previously proposed by the applicant of the present application, it becomes possible to significantly improve the reliability of the multilayer wiring board.

Hereinafter, the manufacturing process of manufacturing the multilayer wiring board using the adhesive-coated copper foil according to the present invention will be explained.
This will be explained with reference to the drawings.

FIGS. 5 to 11 show the process order of the multilayer wiring board. In this example, first, as shown in FIG. 5, a conductive foil, e.g.
A copper-clad laminate coated with copper foil is prepared, and the copper foil is selectively etched to form a first conductive foil pattern, that is, a wiring pattern 22. At this time, it is possible to perform surface treatment on the wiring pattern 22 in order to improve the adhesion between the wiring pattern 22 and an insulating layer to be formed next. Surface treatments include, in addition to blackening treatment, chemical roughening treatment to form an oxide film of CuO, Cu ₂ O, etc. on the surface, mechanical roughening treatment by sandblasting or brushing, and the like.
Next, on the substrate 21 including the first wiring pattern 22, an insulating layer 23 made of, for example, an ultraviolet curable resin is placed on the connection portion of the first wiring pattern 22 (approximately circular in the illustrated example) as shown in FIG. ) 22a are formed by printing. The insulating layer 23 is formed by so-called reciprocating printing in which a squeegee is moved back and forth. According to this, even if the shoulder portion of the first wiring pattern is in the shadow, due to the reciprocating coating, the shadow portion is sufficiently coated, and an insulating layer 23 without pinholes can be formed.

Next, as shown in FIG.
The copper foil 1 with the adhesive layer 3 laminated thereon is laminated onto the substrate 21 using a roll laminating device (for example, inserted between a pair of silicone rubber rolls heated to 150° C. at a speed of 5 m/min). For laminating the copper foil 1, it is necessary to keep the adhesive in a semi-cured state, so the hot press method cannot be used. Conventionally, thermally activated adhesives with poor adhesion to the copper foil 1 have been used. Therefore, the adhesive strength of the copper foil 1 was low and reliability was poor. However, by using the adhesive-coated copper foil according to the present invention, the second adhesive layer 3 has thermal activation when bonded by the roll laminating device, so that it can be attached to the substrate 21 in a semi-cured state with good adhesion. Not only can the copper foil 1 be laminated and combined, but also the copper foil 1 can be bonded to the substrate 21 with a predetermined adhesive strength due to the peel strength of the first adhesive layer 2 in the curing process described later.

Next, as shown in FIG. 8, selective etching is performed on the copper foil 1 using an aqueous solution of ferrous chloride (etching solution) to form a second conductive foil pattern, that is, a wiring pattern 26. At this time, the connecting portion 26a of the second wiring pattern 26 with the first wiring pattern 22 has a shape (so-called annular shape) having a closed inner peripheral surface.
Instead, as shown in the figure, the first wiring pattern 2
For example, in the illustrated example, it is formed into a substantially semicircular shape so as to partially overlap the connecting portion 22a of No. 2. This copper foil 1
During selective etching, the adhesive layers 2 and 3 on the back surface are not removed.

Next, as shown in FIG. 9, a solder resist layer 27 is formed by printing except for the portions corresponding to both the connecting portions 22a and 26a. This solder resist layer 27 can be made of an ultraviolet curing resin such as epoxy acrylate resin, and has the property of not being affected by the organic solvent used to peel off the adhesive layers 2 and 3. Then, this solder resist layer 27 and the second wiring pattern 2
Using an organic solvent (for example, a solution of methylene chloride), the semi-cured adhesive layers 2 and 3 exposed at the connection portions 26a of the first wiring pattern 22, that is, the portions corresponding to the connection portions 22a of the first wiring pattern 22, using the copper foil as a mask. It is selectively dissolved and peeled off to expose the surface of the connecting portion 22a.

Next, the connection portion 22a of the first wiring pattern 22
The base material 21 is pressed by mechanical means such as pressing so that the central part thereof includes at least a portion 33 where the connecting portion 26a of the second wiring pattern 26 does not overlap.
An electrical component insertion hole 28 is formed so as to penetrate therethrough. Next, each semi-cured adhesive layer 2, 3 is cured with an electron beam or thermally to obtain a multilayer wiring board 29 shown in FIG. Although the insertion hole 28 was formed in the process shown in FIG. 10, it is also possible to form the insertion hole 28 in advance before the selective etching of the copper foil shown in FIG. This is to prevent the adhesion strength of the connecting portion 22a to the base material 21 from decreasing due to impact when drilling with a press, and the copper foil is attached to the base material 21.
If press holes are punched when the entire surface of the adhesive is adhered, a decrease in adhesive strength can be avoided.

Thereafter, the lead wire 31 of the electrical component 30 is inserted into the insertion hole 28 as shown in FIG. do. The conductive substance 32 may be solder (solder flow, manual soldering,
Conductive materials such as reflow with solder cream, solder coater leveler), gallium alloy (which has the property of forming a paste at initial working temperature and then becoming alloyed and solidifying over time), silver paint, carbon paint, copper paint, etc. can be used. .

As described above, by using the copper foil with adhesive according to the present invention, even when the adhesive is first used in a semi-cured state and is completely cured at the end, the copper foil 1 can be bonded with high adhesive strength. It becomes possible to
It becomes possible to improve the reliability of the multilayer wiring board 29.

As described above, according to the present invention, it is possible to obtain an adhesive-coated copper foil that has sufficient adhesive hardness and can be bonded to a substrate with good productivity.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part showing an adhesive-coated copper foil according to the present invention, FIG. 2 is a schematic diagram showing a method of forming each adhesive layer, and FIG. 3 is a perspective view showing a method of measuring peel strength. , FIG. 4 is a schematic diagram showing a method of laminating an adhesive-coated copper foil to a substrate according to the present invention. 5 to 11 are partially sectional perspective views showing the sequence of steps in the manufacturing process of the multilayer wiring board. 1... Copper foil, 2... First adhesive layer, 3... Second adhesive layer.

Claims (1)

[Claims] 1. On a copper foil, a first adhesive layer having a peel strength of 15 kg/cm or more with respect to the copper foil and a second adhesive layer that is thermally active and can be bonded with a hot roll are sequentially laminated. Copper foil with adhesive formed by forming.