JPH10272700A - Sheet for manufacture of multi-layer print wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate waste of sensitized film at the time of conductor pattern forming of a copper-clad laminate provided with copper foil on both surfaces in multi-layer wiring board manufacturing, and eliminate labor of inserting a release film in the copper-clad laminated sheet laminating process. SOLUTION: A sheet 10 is constituted by providing a low-adhesion layer composed of silicone elastomer or the like on a base film having temperature resistance and chemical resistance. When a conductor pattern is to be formed on one copper foil 22 of a copper-clad laminate 21, the sheet 10 functions as a protective film to protect other copper foil 23 by adhering to it. And in next heat-pressing process of the copper-clad laminate 21, the sheet 10 functions as a release film for preventing squeezing out of prepreg inserted between the copper-clad laminates 21, and preventing adhesion between the copper-clad laminates 21, and between the copper-clad laminate 21 and a pressing plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet for producing a multilayer printed wiring board used in the production of a multilayer substrate, and more particularly to a sheet which functions as a protective film for protecting a copper foil as an outer layer which is not patterned when a conductor pattern is formed. Multi-layer printed wiring that also serves as a release film to prevent the prepreg from protruding when multiple copper-clad laminates are crimped, and to prevent adhesion between the copper-clad laminates and the copper-clad laminate and the press plate. The present invention relates to a sheet for manufacturing a plate.

[0002]

2. Description of the Related Art In recent years, multilayer printed wiring boards that can be made denser and thinner have been widely used as circuit boards for small electronic devices such as portable electronic devices. Accordingly, printed wiring boards having interstitial via holes are increasing. Among them, a printed wiring board having a blind via hole has become possible to further reduce the weight and increase the density.

[0003] Such a multilayer printed wiring board is manufactured as follows. First, as shown in FIG.
Is made in a copper-clad laminate (hereinafter referred to as a “double-sided board”) 21 on which a through hole 2 is formed by plating.
1a is made conductive (a, b). Next, a resist is coated on both sides or a photosensitive film 30 called a dry film is laminated, only one of the copper foils is exposed in close contact using a patterned work film, and the other is entirely exposed,
Develop (c). Thereby, only the resist or the photosensitive film in the unexposed portion of one copper foil is removed (d).
Then, the copper foil corresponding to the unexposed portion is removed by etching with a copper etching solution such as copper chloride or iron chloride (e), and the remaining resist or photosensitive film is finally removed (f). The photosensitive film 30 to be laminated on the copper foil 22 on which the conductor pattern is not formed is used for protecting the copper foil from being etched. It is usually called a discarded dry film because it is sometimes removed together.

[0004] Next, a plurality of copper-clad laminates 20 each having a conductor pattern formed on one side in such a manner as shown in FIG.
A prepreg 25 (semi-cured by impregnating with an epoxy resin such as glass fiber) is interposed and heated and pressurized,
The prepreg 25 is completely cured and the copper-clad laminates 20, 2
0 is adhered. In this case, pressing is performed with the release film 40 interposed between the outer layer (a copper foil on which no conductor pattern is formed) and the press plate 50. When several sets of a plurality of copper-clad laminates are stacked and pressed simultaneously, a release film is also interposed between the outer layer of the copper-clad laminate and the outer layer of another copper-clad laminate.

In the release film 40, the prepreg 25 protrudes from the through-hole at the time of heating and pressurizing and adheres to the copper foil to adversely affect the etching process which is a later process, or the copper foil and the press plate stick to each other. To prevent As such a release film, a film using a fluorine-based resin or a silicone-based resin (JP-A-5-167250)
No.), one using a thermoplastic film (JP-A-6-326467), one having a silicone film formed on one surface of a substrate sheet (JP-A-6-24691)
And so on.

[0006]

In the production of the above-mentioned multilayer printed wiring board, when a conductor pattern is formed on one copper foil of a double-sided board, a resist or a photosensitive film is required to protect the other. In addition, since the photosensitive film is removed in the peeling step after the formation of the conductor pattern, there is waste. On the other hand, in the hot pressing step performed after the formation of the conductor pattern, a step of sandwiching the release film 40 between the copper-clad laminate and the press plate and between the copper-clad laminate outer layer and the copper-clad laminate outer layer is newly performed. Needed.

Accordingly, the present invention provides a sheet for producing a multilayer printed wiring board, which eliminates waste of a photosensitive film used for protecting a copper foil as an outer layer, and serves both as a protective film for a copper foil and a release film in a hot pressing step. The purpose is to do. The present invention also has excellent performance as a release film,
An object of the present invention is to provide a sheet for producing a multilayer printed wiring board, which can prevent the prepreg from protruding and can surely prevent the adhesion between the copper-clad laminate, the press plate and the copper-clad laminate.

[0008]

The sheet for producing a multilayer printed wiring board of the present invention, which achieves the above object, comprises a copper-clad laminate having copper foils on both sides, a copper pattern formed on one copper foil, A plurality of laminated laminates and thermocompression bonding, when manufacturing a multilayer printed wiring board, a protective film for protecting the other copper foil of the copper clad laminate, copper clad laminates at the time of thermocompression bonding or It also serves as a release film for preventing the adhesion between the copper-clad laminate and the press plate, and as a preferred embodiment, a release substrate film having heat resistance and chemical resistance, and on the substrate film And a formed weakly adhesive layer.

In the sheet for producing a multilayer printed wiring board according to the present invention, the releasable base film is made of a material which is insoluble or hardly soluble in chemicals such as a developing solution of a photosensitive film and a copper etching solution in the production of the multilayer printed wiring board. Consisting of
It preferably comprises polyphenylene sulfide.

The weak adhesive layer has a peel strength (JIS Z-0237) of preferably 100 gf / 25 mm width or less, more preferably 1 to 20 gf.
/ 25mm width. The peeling strength according to JIS Z-0237 is measured by measuring the peeling strength from a stainless steel plate (SUS). By setting the peeling strength within such a range, the copper can be removed from the copper foil in the conductor pattern forming step without peeling from the copper foil. The foil can be protected and, after hot pressing, can be easily peeled off without remaining on the copper foil surface. A preferred low tack layer comprises a silicone elastomer.

In order to manufacture a multilayer printed wiring board using the multilayer printed wiring board manufacturing sheet of the present invention, a conductive pattern is first formed when a conductive pattern is formed on a double-sided board provided with through holes that have been subjected to conduction treatment. A resist coating or a photosensitive film is attached to one of the copper foils, and the weak adhesive layer side of the sheet for producing a multilayer printed wiring board of the present invention is attached to the other copper foil. Next, according to a normal process, the exposed portion of the resist or the photosensitive film is cured by exposing and developing, and after removing the non-exposed portion, the copper foil corresponding to the non-exposed portion is removed by etching. Then, the exposed portions of the photosensitive film are peeled off by dipping the double-sided board in a peeling solution. During the period from the pattern formation to the peeling step, the copper foil to which the sheet for producing a multilayer printed wiring board of the present invention is adhered is protected by the sheet for producing a multilayer printed wiring board.

Next, two copper-clad laminates are stacked with the prepreg therebetween with the copper foil layer (inner layer) on which the conductor pattern is formed facing inside. If necessary, a plurality of such laminates of the copper-clad laminate and the prepreg are laminated. These laminates are hot pressed. In this case, since the sheet for producing a multilayer printed wiring board of the present invention is directly adhered to the outer layer of the copper-clad laminate, a new release film is added between the copper-clad laminate and the copper-clad laminate and the press plate. There is no need to intervene between
The prepreg is prevented from protruding from the through hole during pressing. After pressing, the prepreg is easily peeled off from the weak adhesive layer of the sheet for producing a multilayer printed wiring board, so that the copper-clad laminates and the copper-clad laminate and the press plate can be easily peeled off.

Thereafter, the sheet for producing a multilayer printed wiring board is peeled off from the outer layer, and a conductor pattern is formed on the outer layer. At this time, since the sheet for producing a multilayer printed wiring board of the present invention is adhered to the outer layer by the weak adhesive layer, it can be easily peeled from the outer layer without damaging the outer layer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the sheet for producing a multilayer printed wiring board according to the present invention will be described in more detail.

The sheet 10 for manufacturing a multilayer printed wiring board according to the present invention has a basic structure as shown in FIG. 1 comprising a base material 11 and a weak adhesive layer 12 formed on the base material. A release film 13 is provided on 12.

The base material 11 is insoluble or hardly soluble (chemical resistance) in a developing solution of a resist or a photosensitive film, a copper etching solution, and a resist (photosensitive film) stripping solution in a conductor pattern forming step of manufacturing a multilayer printed wiring board.
Material at the heating temperature of the hot pressing step (usually 150
(200 ° C.).

Examples of such a material include fluorine resins such as heat-resistant polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polyimide, polyaminobismaleimide, and polytetrafluoroethylene. Of these, polyphenylene sulfide and fluororesin are preferred, and polyphenylene sulfide is particularly preferred in terms of ease of molding and cost. Usually, the press plate is made of copper or SUS, but polyphenylene sulfide is excellent in the releasability (back surface releasability) from such a press plate material.

The thickness of the base material 11 is not particularly limited as a protective film of a copper foil, but is 4 to 250 μm, preferably 8 to 50 μm as a release film in a hot pressing step.
More preferably, the thickness is 10 to 40 μm. If the thickness of the base material 11 is too thin, the handleability and the back surface treatment property are poor, and the prepreg cannot be effectively prevented from protruding. On the other hand, if the thickness is more than 250 μm, it is disadvantageous in applying sufficient heat and pressure to the entire substrate, which is not desirable in terms of cost.

The weak adhesive layer 12 is a layer that is adhered to a copper foil with a weak adhesive force, and is made of a resin having excellent adhesive properties, heat resistance, chemical resistance, and release properties. It is preferable that the adhesive strength is considerably lower than that of a normal adhesive. Specifically, the peel strength of a normal adhesive is about 400 to 1000 gf / 25 mm width, but the weak adhesive layer of the present invention has a peel strength (JIS Z-0237) of 100 gf /
The width is 25 mm or less, preferably 1 to 20 gf / 25 mm. By setting such a range, the copper foil can be protected without peeling off from the copper foil in the conductor pattern forming step, and can be easily peeled off after hot pressing without remaining on the copper foil surface.

In the present invention, the peel strength is JIS Z-02
It was measured according to 37. That is, a sample having a width of 25 mm was applied to a stainless steel plate of SUS304 polished at # 280 with a load of 2 kgf and pressed with a rubber roller.
After standing for 30 minutes under the condition of 5% RH, the sample was peeled at a peeling rate of 300 mm / min and peeled at 180 ° to measure the strength.

As the material of the weak adhesive layer 12, a silicone elastomer having an organopolysiloxane skeleton represented by the following formula is preferably used.

[0022]

Embedded image In general, silicone elastomers include heat-curable silicone rubber and liquid silicone rubber. Liquid silicone rubber is preferred because it can form a weakly adhesive layer by easy application and can easily adjust the adhesive force. . Liquid silicone rubber is condensation type, addition type,
There is an ultraviolet curing type, and any type of liquid silicone rubber can be used. However, an addition type, which has a high reaction speed, a wide range of resin selection, and easy adjustment of adhesive strength, is particularly preferable. After curing, the addition type liquid silicone rubber is used alone or in combination of two or more so that a desired adhesive strength is obtained. For example, a desired adhesive strength can be obtained by mixing and using a liquid silicone rubber which becomes a gel after curing and a liquid silicone rubber which becomes a sol after curing.

The thickness of the weak adhesive layer 12 is preferably 1 to 50.
μm, more preferably 5 to 20 μm. It is preferable to adjust the thickness in this range so as to obtain a desired peel strength according to the adhesive strength of the material itself. If the thickness of the weak adhesive layer 2 is less than 1 μm, a sufficient adhesive force cannot be obtained even if a silicone rubber having a large adhesive force is used as a material. If the thickness exceeds 50 μm, the layer may protrude from both ends of the layer during hot pressing and may remain after pressing.

The weak adhesive layer 12 is formed by applying a mixture of the above-described silicone rubber material, a catalyst such as platinum, and an organic solvent as required on the base material 11 to a predetermined thickness and curing the mixture. . As a coating method, a known method such as a bar coating method, a roll coating method, a curtain flow method, an extrusion method, and a die coating method can be adopted. When the material constituting the weak adhesive layer 12 is an ultraviolet-curable material, it is cured by irradiating ultraviolet rays after application.

The release film 13 protects the weak adhesive layer 12 when the sheet for producing a multilayer printed wiring board of the present invention is not used, and is made of paper such as release paper, plastic such as polyethylene, polyethylene terephthalate, and polypropylene. There is no particular limitation as long as the film or the like can be easily peeled off from the weak adhesive layer 12 when used.

Next, a method for manufacturing a multilayer printed wiring board using the sheet for manufacturing a multilayer printed wiring board of the present invention will be described with reference to FIGS. FIG. 2 is a view showing one embodiment of a conductor pattern forming step. In this step, first, a through hole 21a is formed in a copper-clad laminate (double-sided board) 21 in which copper foils 22 and 23 are laminated on both sides (a). ), The through holes 21a are plated to make them conductive (b). Next, the photosensitive film 30 is laminated on one copper foil 22, and the weak adhesive layer 12 of the sheet 10 for producing a multilayer printed wiring board is laminated on the other copper foil 23 (c). Lamination of the photosensitive film 30 and the sheet 10 for producing a multilayer printed wiring board can be performed simultaneously by one laminator, and is usually performed under heating at 100 to 120 ° C.

Next, the photosensitive film 30 is contact-exposed using a work film on which a predetermined pattern is formed by an exposure device such as a high-pressure mercury lamp, and further developed with a weakly basic developer such as an aqueous solution of sodium carbonate. The portions of the photosensitive film 30 that have not been removed are removed (d). The exposed copper foil portion is etched with an etchant to form a conductor pattern (e). Finally, the remaining photosensitive film 30 is peeled off and removed with a relatively strong base remover such as sodium hydroxide. In this step, the multilayer printed wiring board manufacturing sheet 10 is also exposed to a developing solution, an etching solution, and a stripping solution, but both the base material 11 and the weak adhesive layer 12 of the multilayer printed wiring board manufacturing sheet 10 are chemically resistant. Since it is made of a strong material, it functions as a protective film for copper foil without being affected by these materials.

The copper-clad laminate 20 having the conductor pattern formed on the inner layer 22 'as described above is laminated by a hot press shown in FIG. 3 to form a multilayer printed wiring board. In this step, two copper-clad laminates 20 are stacked with the prepreg 25 therebetween with the patterned inner layer 22 ′ inside, and set between the press plates 50, 50 of a press machine. Although only two copper-clad laminates are shown in FIG. 3, a plurality of such laminates of the copper-clad laminate and the prepreg 25 are usually stacked. These laminates are hot pressed at about 150-200 ° C. As a result, the semi-cured prepreg is cured,
Adhere two copper-clad laminates. At this time, since the multilayer printed wiring board manufacturing sheet 10 is adhered to the outer layer 23 (copper foil having no conductor pattern) of the copper-clad laminate 20, the prepreg 25 is prevented from protruding from the through hole. At the same time, the press plate 50 and the outer layer 23 or the outer layer 23 and the outer layer of another copper-clad laminate are prevented from being bonded by the prepreg in the through-hole portion. Therefore, when the multilayer printed wiring board is taken out of the press device after pressing, the individual multilayer printed wiring boards can be easily peeled off.

Finally, the multilayer printed wiring board manufacturing sheet 10 adhered to the outer layer of the multilayer printed wiring board is peeled off, and a conductor pattern is formed on the outer layer 23. In this case, since the multilayer printed wiring board manufacturing sheet 10 is attached to the copper foil with a weak adhesive force by the weak adhesive layer 12, the sheet 10 is easily attached without damaging the outer layer and remaining on the outer layer. Peeled off.

Although the illustrated manufacturing method shows the case of manufacturing a four-layer multi-layer printed wiring board, a copper-clad laminate having conductor patterns formed on both sides is used as an inner-layer board, and copper-clad laminates serving as outer layers are provided on both sides. The sheet 10 for producing a multilayer printed wiring board can also be used for producing a three-layer copper-clad laminate produced by hot-pressing a laminated board or a multilayer printed wiring board having four or more layers.

[0031]

Embodiments of the present invention will be described below. Example 1 An addition-type two-component liquid silicone rubber (KE109: manufactured by Shin-Etsu Chemical Co., Ltd.) and an addition-type one-component liquid silicone (KE104: Shin-Etsu Chemical Co., Ltd.) were placed on a 25 μm-thick polyphenylene sulfide film. )) By weight ratio 50:50
The mixture was applied at a ratio of about 10 μm to form a weakly adhesive layer having a thickness of about 10 μm, and a 25 μm thick release film was formed thereon.
m of polyethylene terephthalate film to obtain a sheet for producing a multilayer printed wiring board.

When the peel strength of the weak adhesive layer of the sheet for producing a multilayer printed wiring board was measured by a 180 ° peeling method according to JIS Z-0237 at a speed of 300 mm / min using a stainless steel plate as a test piece, it was 3 gf / 25 mm. Was.

Using this multi-layer printed wiring board manufacturing sheet, a four-layer multi-layer printed wiring is formed by using a dry film (Nichigo Alfo 801Y40: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) according to the method shown in FIGS. When the plate was prepared, the copper foil could be protected without being affected by the developing solution, the etching solution and the stripping solution. Further, even during lamination by hot pressing, it was possible to prevent the prepreg from protruding from the through-hole portion and to easily peel off the individual printed wiring boards.

Example 2 An addition-type two-component liquid silicone rubber (TSE3033: manufactured by Toshiba Silicone Co., Ltd.) was applied on a polyphenylene sulfide film having a thickness of 38 μm to form a weak adhesive layer having a thickness of about 15 μm. 25 μm thick as a release film on it
m of polyethylene film was laminated to obtain a sheet for producing a multilayer printed wiring board.

The peel strength of the weak adhesive layer of the sheet for producing a multilayer printed wiring board was measured in the same manner as in Example 1 and found to be 5 gf / 25 mm.

Using this multilayer printed wiring board manufacturing sheet, a four-layered multilayer printed wiring board was prepared in the same manner as in Example 1, and the copper foil was protected without being affected by the developing solution, etching solution, and stripping solution. Was completed. Further, even when laminating by hot pressing, it was possible to prevent the protrusion of the blebreg from the through-hole portion and to easily peel off the individual printed wiring boards.

Comparative Example 1 An addition-type two-component liquid silicone rubber (KE109: manufactured by Shin-Etsu Chemical Co., Ltd.) and an addition-type one-component liquid silicone (KE10) were placed on a 25 μm-thick polyolefin film.
4: Shin-Etsu Chemical Co., Ltd.) mixed at a weight ratio of 50:50 to form a weakly adhesive layer having a thickness of about 10 μm, and polyethylene having a thickness of 25 μm as a release film thereon. The terephthalate film was overlaid to obtain a sheet for producing a multilayer printed wiring board.

The peel strength of the weak adhesive layer of the sheet for producing a multilayer printed wiring board was measured in the same manner as in Example 1.
It was 3 gf / 25 mm.

Using this multilayer printed wiring board manufacturing sheet, a four-layered multilayer printed wiring board was prepared in the same manner as in Example 1, and the copper foil was protected without being affected by the developing solution, etching solution and stripping solution. Was completed. However, due to the lack of heat resistance of the polyolefin film, it was deformed by heat during lamination by hot pressing.

Comparative Example 2 A silicone pressure-sensitive adhesive (TSR1510: commercially available pressure-sensitive adhesive) was placed on a 25 μm-thick polyphenylene sulfide film.
Toshiba Silicone Co., Ltd.) was applied to form an adhesive layer having a thickness of about 20 μm, on which a release film having a thickness of 25 μm was formed.
m of polyester film were laminated to obtain a sheet for producing a multilayer printed wiring board.

The peel strength of the weak adhesive layer of the sheet for producing a multilayer printed wiring board was measured in the same manner as in Example 1.
It was 800 gf / 25 mm.

Using this multilayer printed wiring board manufacturing sheet, a four-layered multilayer printed wiring board was prepared in the same manner as in Example 1, and the copper foil was protected without being affected by the developing solution, etching solution, and stripping solution. Was completed. However, at the time of lamination by hot press, the prepreg protruded from the through hole part,
There was a problem to be corrected in a later process.

Further, when the sheet for producing a multilayer printed wiring board was to be peeled off from the copper foil, the adhesive force was too strong to be peeled off, and the pressure-sensitive adhesive left adhesive on the copper foil.

[0044]

As is apparent from the above examples, the sheet for producing a multilayer printed wiring board according to the present invention can be used for forming a pattern of one copper foil of a copper-clad laminate having copper foils on both sides when the other copper foil is formed. It functions as a protective film to protect the film and also as a release film in the hot pressing process.
Exposure of the discarded dry film and stripping with a stripping solution are not required, the power for exposure and the amount of stripping solution used can be reduced, and the trouble of interposing a release film in the hot pressing step can be omitted. Further, since the sheet for producing a multilayer printed wiring board of the present invention, since the weak adhesive layer has a predetermined adhesive strength, in the hot press step, the prepreg protrudes and the copper-clad laminates or the copper-clad laminate in the through-hole portion are pressed together. Adhesion with the plate can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a sheet for producing a multilayer printed wiring board according to the present invention.

FIG. 2 is a diagram showing an example of a conductor pattern forming step in a multilayer printed wiring board manufacturing process using the multilayer printed wiring board manufacturing sheet of the present invention.

FIG. 3 is a view showing an example of a hot pressing step in a multilayer printed wiring board manufacturing process using the multilayer printed wiring board manufacturing sheet of the present invention.

FIG. 4 is a view showing a part of a conventional multilayer printed wiring board manufacturing process.

FIG. 5 is a view showing a part of a conventional multilayer printed wiring board manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Multilayer printed wiring board manufacturing sheet 11 ... Substrate 12 ... Weak adhesive layer 13 ... Release film 20 ... Copper-clad laminates 22, 23 ... copper foil 22 '... inner layer (copper foil with conductor pattern) 25 ... prepreg 30 ... photosensitive Film 50 Press plate

Claims (5)

[Claims] When a conductor pattern is formed on one copper foil of a copper-clad laminate having copper foils on both sides, a plurality of copper-clad laminates are laminated and thermocompressed to produce a multilayer printed wiring board. A protective film for protecting the other copper foil of the copper-clad laminate, and a multilayer that also serves as a release film for preventing adhesion between the copper-clad laminates during thermocompression bonding or between the copper-clad laminate and the press plate. Sheet for manufacturing printed wiring boards. 2. A sheet for producing a multilayer printed wiring board, comprising: a releasable base film having heat resistance and chemical resistance; and a weak adhesive layer formed on the base film. 3. The sheet for producing a multilayer printed wiring board according to claim 2, wherein the release base film is made of polyphenylene sulfide. 4. The weak adhesive layer has a peel strength (JIS Z-0237).
3. The sheet for producing a multilayer printed wiring board according to claim 2, wherein the sheet has a width of 100 gf / 25 mm or less. 5. The sheet for producing a multilayer printed wiring board according to claim 2, wherein said weak adhesive layer is made of a silicone elastomer.