Method of manufacturing bonding sheet for printed wiring board and complex multilayered printed wiring board

The present invention is a bonding sheet used for manufacturing a printed wiring board, and is capable of improving workability. Manufacture of a bonded sheet for a printed wiring board and a composite multilayer printed wiring board using the bonding sheet for a printed wiring board. Regarding the method.

Conventionally, in the manufacture of a composite multilayer printed wiring board such as flex / rigid, for example, a bonding sheet is temporarily bonded to the circuit surface of a copper-clad laminate in which only one side is circuit-formed, and the surface to which the bonding sheet is temporarily bonded is placed inside. This was done by superimposing a circuit-formed flexible copper-clad laminate on which the coverlay was laminated and integrating it by heating and pressurizing. Further, after that, a composite multilayer printed wiring board was obtained by performing post-processing such as drilling, plating, and processing of the outer layer circuit.

At this time, in the step of temporarily adhering the bonding sheet to the circuit surface of the copper-clad laminate in which only one side is formed as a circuit, an adhesive is cast on the carrier film, and the adhesive surface of the bonded sheet is dried. It is carried out by heat-bonding with a heat roll or the like according to the circuit surface, and the subsequent steps are carried out sequentially after peeling off the carrier film of the temporarily bonded bonding sheet (see, for example, Patent Document 1).<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-348556</text></patcit>

<p> However, since the film conventionally used for the carrier film is colorless and transparent polypropylene, polyester, etc., it is difficult to visually identify the presence or absence of the carrier film after temporary bonding, and there is a problem that the carrier film is forgotten to be peeled off.</p><p> In order to prevent the carrier film from being forgotten to be peeled off, a colored bonding sheet was proposed by adding various pigments to the film. However, since the colored bonding sheet had completely lost its transparency, it was laminated with copper. When the bonding sheet is temporarily bonded to the plate, it becomes impossible to position the bonding sheet while looking at the circuit through the bonding sheet, which causes a decrease in workability.</p><p> Therefore, the present invention has been made to eliminate the above-mentioned drawbacks, and provides a bonding sheet for a printed wiring board which is excellent in workability of temporary bonding of a bonding sheet and can prevent the carrier film from being forgotten to be peeled off. The purpose is to do.</p>

<p> As a result of intensive research to achieve the above object, the present inventor has obtained a carrier film having a haze value of 20 to 80%, which is coated on one side or both sides with a release agent, and thermosetting adhesive to the release agent surface. The present invention has been completed by finding that the above object can be achieved by using the agent cast, dried and formed into a film for a bonding sheet.</p><p> That is, in the bonding sheet for a printed wiring board of the present invention, a carrier layer having a haze value of 20 to 80%, which is coated on one side or both sides with a release agent, and heat laminated on the release agent surface of the carrier layer. It is characterized by being composed of a curable adhesive layer.</p><p> Further, in the method for manufacturing a composite multilayer printed wiring board of the present invention, a bonding sheet is temporarily bonded to a circuit-formed copper-clad laminate, a carrier layer is peeled from the bonding sheet, and the peeled surface of the carrier layer of the bonding sheet is formed. In a method for manufacturing a composite multilayer printed wiring board in which a flexible circuit board on which a coverlay is laminated is heated and pressurized, the bonding sheet is the bonding sheet for a printed wiring board of the present invention.</p>

<p> According to the method for manufacturing a bonding sheet and a composite multilayer printed wiring board of the present invention, a circuit-formed flexible circuit board on which a coverlay is laminated and a circuit-formed copper-clad laminated board are heated and heated via the bonding sheet. When pressure-integrating, the workability of the process of positioning and temporarily bonding the bonding sheet to the circuit forming surface of the copper-clad laminate can be improved, and the copper-clad laminate and the flexible printed circuit board to which the bonding sheet is temporarily bonded can be improved. Since the presence or absence of the carrier layer can be easily visually confirmed in the laminating process with the above, it is possible to confirm that the bonding sheet is temporarily bonded and prevent forgetting to peel it off, and further workability. Can be improved.</p>

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a structural cross-sectional view of the bonding sheet of the present invention.

First, the bonding sheet of the present invention will be described. The bonding sheet 1 of the present invention is formed by laminating a carrier layer 2, a release agent layer 3, and a thermosetting adhesive layer 4 in this order, and the release agent layer 3 is formed by laminating the carrier layer 2 and the carrier layer 2. This is intended to facilitate peeling from the thermosetting adhesive layer 4. That is, in the bonding sheet 1 of the present invention, the carrier layer 2 is formed integrally with the thermosetting adhesive layer 4 via the release agent layer 3.

Here, the carrier layer 2 may have a haze value of 20 to 80% and may be able to hold the thermosetting adhesive layer 4 until it is temporarily adhered to the copper-clad laminate. The material and shape are not particularly limited.

Further, the carrier layer 2 can be peeled off from the thermosetting adhesive layer 4 after being temporarily bonded to the copper-clad laminate, and is in the form of a film and flexible so that the peeling can be easily performed. For example, an insulating resin having a thickness of 25 to 100 μm is preferable.

Examples of the insulating resin include polyester, polypropylene, polymethylpentene and the like, and polyester is particularly preferable from the viewpoint of heat resistance and cost.

In addition, the carrier layer with a haze value of 20 to 80% has fine scratches on the surface of a transparent insulating resin film having a haze value of less than 20%, or an insulating resin to which fine inorganic powders such as zinc oxide and titanium oxide are added. Can be obtained by processing this into a film using the above as a raw material.

The haze value of the carrier layer in the present specification is a value measured according to JIS K 7136.

Here, the release agent layer 3 is provided on the surface of the carrier layer 2, and as the release agent, the carrier layer 2 and the thermosetting adhesive layer 4 are formed even if they are cast on the carrier layer. There is no particular limitation as long as it does not maintain the releasability and does not hinder the adhesive performance of the thermosetting adhesive layer 4 in the subsequent step, and examples thereof include silicone-based releasers and alkyd-based releasers.

The thermosetting adhesive layer 4 is integrated with the carrier layer 2 via the release agent layer 3, and has a function of adhering the circuit boards of the printed wiring boards to each other, and is used here. The thermosetting adhesive is a thermosetting resin used for known multilayer printed wiring boards, for example, a modified acrylic resin type, an acrylonitrile butadiene rubber / epoxy resin type, a carboxyl group-containing acrylonitrile butadiene rubber / phenol resin type, or the like. Can be mentioned.

The thermosetting adhesive layer 4 is suitably used for adhering a copper-clad laminate and a flexible printed wiring board on which a coverlay is laminated, and its thickness is preferably 10 to 75 μm.

The bonding sheet of the present invention is composed of the above-mentioned layers. For example, a thermosetting adhesive is cast or coated on the release agent surface of the carrier layer 2 coated with the release agent layer 3. The thermosetting adhesive layer 4 which has been dried to form a film or has been formed into a film is superposed on the carrier layer 2 and laminated by a hot press method, a vacuum press method, an autoclave press method, a hot roll press method, a sizing press, or the like. It can be manufactured by squeezing. At this time, there is no limitation on the method of casting or coating the thermosetting adhesive on the carrier layer, and a conventionally known method can be used. For example, a comma coater, a die coater, a roll coater, a knife coater, a reverse coater, etc. This can be done using a coating device such as a gravure coater, a blade coater, or a spin coater.

Further, as a second embodiment, the bonding sheet of the present invention has a configuration in which the release agent layer 3 and the thermosetting adhesive layer 4 are laminated on both sides of the carrier layer 2 as shown in FIG. You can also. In this case, since the copper-clad laminates can be laminated on both sides, two copper-clad laminates can be prepared with one bonding sheet. Further, in a composite multilayer printed wiring board, since copper-clad laminates are usually used on both sides of the printed wiring board, this can be handled as a set used for one printed wiring board, and workability can be improved. ..

Next, a method for manufacturing a composite multilayer printed wiring board using the bonding sheet of the present invention will be described.

FIG. 3 is a diagram showing a laminated structure of a printed wiring board using the bonding sheet of the present invention, and FIG. 4 is a diagram showing a composite multilayer printed wiring board after manufacturing.

The method for manufacturing the composite multilayer printed wiring board 20 described here is to integrate the flexible circuit 21 and the copper-clad laminate 22 using the bonding sheet 1 of the present invention, and is basically the same as the conventional manufacturing method. This is performed by the operation of, and will be described in detail below.

First, the bonding sheet 1 having the opening 23 is positioned on the circuit forming surface of the circuit-formed copper-clad laminate 22, and temporarily bonded. This temporary bonding can be performed by aligning the two sides of the opening 23 so as to overlap the slit 24 on the circuit forming surface side provided on the copper-clad laminate 22, and crimping with a thermal roll. Since the alignment between the opening 23 and the slit 24 can be confirmed through the bonding sheet 1, work efficiency can be improved.

Next, the carrier layer with a release agent is peeled off from the bonding sheet 1 temporarily bonded to the copper-clad laminate 22, the thermosetting adhesive layer is exposed on the surface, and the flexible circuit board 21 on which the coverlay is laminated is copper-clad laminated. It is overlapped with the surface of the thermosetting adhesive of the plate 22 and integrated by heating and pressurizing. At this time, since the carrier layer has a haze value of 20 to 80% and looks cloudy, its existence can be confirmed at a glance, and it is extremely easy to determine whether or not temporary adhesion has been performed and whether or not the carrier layer has been peeled off. It can be confirmed and the work efficiency can be further improved.

Next, drill holes are drilled, through-hole plating is performed, an outer layer circuit is formed, router processing is performed, and then unnecessary parts of the outer layer copper-clad laminate are removed to form a composite multilayer having a rigid portion 25 and a flexible portion 26. The flex rigid printed wiring board 20 is manufactured.

As the coverlay laminated on the flexible circuit board used here, a film based on a polyimide film can be used, and for example, a polypyrromeliteimide-based film, a polybiphenyl-based film, a polyketoneimide-based film, and a polyamide-imide can be used. Examples thereof include based films and polyetherimide-based films.

The copper-clad laminate is not particularly limited as long as it is a commonly used copper-clad laminate, but due to the characteristics of the flex / rigid composite multilayer printed wiring board, the glass-based epoxy copper-clad laminate and the glass base The material is preferably a polyimide copper-clad laminate or the like. These copper-clad laminates are used by forming a conductor pattern on one side.

At this time, the copper foil used for the outermost layer of the composite multilayer printed wiring board is not a conductor pattern formed in advance, but is laminated using the above-mentioned copper-clad laminate so that the pattern-unformed copper foil is the outermost layer. After that, a conductor pattern may be formed on the copper foil.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1) Carboxyl group-containing acrylonitrile butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade name: Nipol 1072) 50 parts by mass, bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 1001) 34 mass 7 parts by mass of phenol novolac resin (manufactured by Showa High Polymer Co., Ltd., trade name: BRG-558), 0.2 parts by mass of 2-ethyl-4-methylimidazole is dissolved in methethylketone to prepare a thermosetting adhesive composition. Manufactured. This adhesive composition is applied to a polyester film (manufactured by Fujimori Kogyo Co., Ltd., trade name: Binasheet 38E-NSD (H)) with a thickness of 38 μm and a haze value of 25%, which is coated with a release agent on one side, with a roll coater. , Dryed and semi-cured to produce a bonding sheet.

This bonding sheet was punched with a punching die, the opening was aligned with the slit portion of the circuit forming surface of the copper-clad laminate in which the circuit pattern was formed on only one side in advance, and temporarily bonded with a laminator roll at 100 ° C. .. After peeling off the polyester film, this copper-clad laminate is laminated on a flexible circuit board with a coverlay, 160 ° C, 60 minutes, 40 kgf / cm.²It was hot-pressed under the conditions of (1) and pasted together to form a shield plate.

After drilling holes in this shield plate and plating through holes, the circuit pattern of the outer layer was formed and router processing was performed. A composite multilayer printed wiring board was manufactured by removing unnecessary parts of the outer layer copper-clad laminate.

(Example 2) As the carrier film of the adhesive, a polyester film having a haze value of 35% (manufactured by Galware Polyester Limited, trade name: Gull Film ER) was used instead of the polyester film having a haze value of 25%. A bonding sheet and a composite multilayer printed wiring board were manufactured in the same manner as in Example 1 except for the above.

(Comparative Example 1) As the carrier film for the adhesive, a polyester film with a haze value of 3.7% (manufactured by Toyobo Co., Ltd., trade name: Toyobo Ester E-5000) was used instead of the polyester film with a haze value of 25%. Manufactured a bonding sheet and a composite multilayer printed wiring board in the same manner as in Example 1.

(Comparative Example 2) As a carrier film for adhesives, a white opaque polyester film containing titanium oxide instead of a polyester film with a haze value of 25% (manufactured by Fujimori Kogyo Co., Ltd., trade name: Binasheet 38E-NSD (W)) ) Was used, and a bonding sheet and a composite multilayer printed wiring board were manufactured in the same manner as in Example 1.

Table 1 shows the workability in the manufacturing process of the flex rigid composite multilayer printed wiring board manufactured in Examples and Comparative Examples.

<tables num="1"><img file="JP2005294294A_D0001.tif" /></tables>

[Slit visibility]

When the bonding sheet provided with the opening and the copper-clad laminate having the slit portion were temporarily bonded by aligning the slit portion and the opening portion, the visibility of the slit portion was confirmed through the bonding sheet. ... The position of the slit part is clear, × ... The position of the slit part is unclear [Detection of the presence or absence of the carrier layer]

It was judged by whether or not the existence of the carrier layer could be confirmed only by glancing at the bonding sheet adhesive surface of the copper-clad laminate. ... could be confirmed, × ... could not be confirmed

From this result, it was confirmed that the bonding sheet for a printed wiring board of the present invention has excellent workability, can prevent forgetting to peel off the carrier layer, and has an excellent effect of the present invention.

<figref num="1">It is sectional drawing of the bonding sheet which provided the release agent layer and the thermosetting adhesive layer on one side of the carrier layer of this invention.</figref><figref num="2">It is sectional drawing of the bonding sheet which provided the release agent layer and the thermosetting adhesive layer on both sides of the carrier layer of this invention.</figref><figref num="3">It is a figure which showed the laminated structure of the composite multilayer printed wiring board using the bonding sheet of this invention.</figref><figref num="4">It is a figure which showed the composite multilayer printed wiring board obtained by the manufacturing method of the composite multilayer printed wiring board of this invention.</figref>

Code description

1,11 ... Bonding sheet, 2 ... Carrier layer, 3 ... Mold release agent layer, 4 ... Thermosetting adhesive layer, 20 ... Composite multilayer printed wiring board, 21 ... Flexible circuit board, 22 ... Copper-clad laminate, 23 ... Opening, 24 ... Slit, 25 ... Rigid, 26 ... Flexible