JP4389627B2 - Method for producing flexible metal laminate - Google Patents

Description

  The present invention relates to a method for manufacturing a laminated plate manufactured by a pressure heating molding apparatus. In particular, the present invention relates to a method for manufacturing a flexible metal laminate used in electronic and electrical equipment.

  As a typical example of a laminated board used for an electronic / electrical equipment printed circuit board, there is a flexible printed circuit (hereinafter abbreviated as FPC).

  A copper-clad polyimide film (hereinafter abbreviated as CCL), which is a flexible metal laminate used for flexible printed wiring boards, is made of three materials: copper foil, polyimide base film, and epoxy thermosetting adhesive. Three-layer type, two-layer type having no adhesive layer, and three-layer type (hereinafter referred to as pseudo-two-layer) having a polyimide adhesive of the same quality as the polyimide base film.

  The two-layer type and the pseudo two-layer type can be manufactured by directly plating copper on a polyimide film without using an adhesive (plating two-layer CCL), applying polyamic acid to a copper foil, drying and imidizing. A polyimide layer is formed without using a polyimide film (cast two-layer CCL), or a polyimide film having a thermocompression-bonding polyimide layer formed on the surface is laminated with a copper foil (laminate two-layer CCL (pseudo two-layer type)) It is known that it is performed by such as.

There have been proposed several methods for producing a laminate of two-layer CCL. For example, there is a method in which a polyimide adhesive is joined in a sandwich between a polyimide film and a metal foil using a vacuum press machine or the like as a heat and pressure molding apparatus (see, for example, Patent Document 1). It is impossible to obtain a scale, and depending on the type of polyimide film, there is a problem that the target performance cannot be obtained because of low adhesive strength. On the other hand, a method of continuously performing heat and pressure molding using a hot roll laminator has also been proposed (see, for example, Patent Document 2). However, in this method, in order to prevent appearance defects such as wrinkles that occur at the time of heat and pressure molding at 200 ° C. or higher, it is shown that pressure heat molding is performed via a protective material between the pressure surface and the laminated material. As a protective material, it is indicated that a polyimide film having a thickness of 75 μm or more is suitable. However, when a protective material having a large thickness is used, heat conduction between the high-temperature heating roll and the laminated material is hindered, and the heating and pressing temperature must be higher than when not used. The hot press molding at a high temperature has a larger dimensional change rate than the molding at a low temperature. Further, it becomes an obstacle to increasing the production speed, and it is difficult to improve productivity and reduce production cost. In addition, if a protective material is not used, it can be manufactured at a lower temperature and at a lower cost, but appearance defects such as wrinkles and copper foil burning occur.
U.S. Pat. No. 4,543,295 JP-A-13-129918 (3rd, 4th page, 18th paragraph)

  Therefore, the objective of this invention is providing the manufacturing method of the flexible metal laminated board which was cheaper and excellent in the dimensional change rate and the external appearance quality.

That is, the present invention is a method for producing a laminated plate in which two or more kinds of laminated materials including a metal foil are bonded together by a pressure heating molding device, and is 50 μm or less between the pressing surface of the device and the laminated material. It is a method for producing a flexible metal laminate, characterized by performing pressure heating molding through an aramid film having a thickness.

  By using the method for producing a flexible metal laminate according to the present invention, even in the case of laminating at a high temperature, which tends to cause appearance defects such as wrinkles, the appearance is good and heat pressing can be performed at a low temperature. A laminate having an excellent rate of change can be obtained at low cost. Therefore, the present invention provides a material suitable as a flexible metal laminate for electronic and electrical equipment.

Details of the present invention will be described below.
Although the use of the laminated board obtained by the manufacturing method of this invention is not specifically limited, It is mainly used as a flexible laminated board for electronic electric devices.

  Although it does not specifically limit as a laminated material used for this invention, Two or more types of laminated materials, More preferably, the laminated material which has thermocompression bonding property, and the laminated material which does not have thermocompression bonding property are used suitably.

  Laminate material with thermocompression bonding is thermocompression bonding on one or both sides on a film selected from thermoplastic polyimide film, thermoplastic polyether film, thermoplastic polyamideimide film, thermoplastic polyesterimide film or heat resistant film. The resin is formed in advance.

  Here, the heat resistant film is a film having a glass transition temperature or decomposition temperature of 200 ° C. or higher, and is preferably an aromatic polyimide film, an aramid film, a liquid crystal polymer film, or the like. The thickness of the film is preferably 5 to 200 μm. Furthermore, the surface of the heat resistant film can be subjected to surface treatment such as hydrolysis, corona discharge, low temperature plasma, physical roughening, and easy adhesion coating treatment. The thermocompression bonding resin is a polyimide-based adhesive composition such as a solvent-soluble polyimide composition, a silicone diamine-containing polyimide composition, a thermoplastic polyimide composition, a polyamideimide composition, or an epoxy composition. Or the hybrid type composition which mixed them can be illustrated. Furthermore, various additives may be blended in the thermocompression bonding resin in order to improve various properties.

  Here, as a laminated material having thermocompression bonding used in electronic circuit materials, it is necessary to have high heat resistance, a polyimide film is used as a heat resistant film, and a thermoplastic polyimide is used as a thermocompression bonding resin. A multilayer polyimide film laminated with is often used. Although the manufacturing method of this multilayer polyimide film is not specifically limited, The multilayer extrusion film-forming method which forms several types of layers into a lump and the coating method which forms another layer sequentially on a heat-resistant film are mentioned. As a coating method, various methods such as a gravure coater, a comma coater, a reverse coater, a bar coater, and a slit die coater can be used according to the physical properties of the coating material.

  Examples of the laminated material that does not have thermocompression bonding include the heat-resistant film and the metal foil described above, and copper foil is preferable for the flexible laminated board. In general, rolled copper foil, electrolytic copper foil, special electrolytic copper foil, copper foil of a type with a small rough surface profile, and the like having a thickness of 5 to 70 μm can be used as the copper foil. Can do. Moreover, it is common that the copper foil surface has an antioxidant layer in order to prevent oxidation.

  The pressurizing and forming apparatus used in the present invention is not particularly limited as long as it is an apparatus that heats a laminated material and applies pressure to laminate. For example, a single-action press apparatus, a multistage press apparatus, a vacuum press apparatus, a multistage vacuum press An apparatus, an autoclave apparatus, a hot roll laminating machine, a double belt press machine, etc. are mentioned, Among these, a hot roll laminating machine can be preferably used. The heating method is not particularly limited as long as it can be heated at a predetermined temperature, and examples thereof include a heat medium circulation method, a hot air heating method, and a dielectric heating method. The heating temperature is preferably 200 ° C. or higher. However, when the laminated board is used for the purpose of passing through a solder reflow furnace having an atmospheric temperature of 240 ° C. for mounting electronic components, It is necessary to have a corresponding Tg, that is, a Tg of 240 ° C or higher. Accordingly, the heating temperature is preferably Tg or higher, and in this case, 240 ° C. or higher is preferable. The pressurization method is not particularly limited as long as a predetermined pressure can be applied, and includes a hydraulic method, a pneumatic method, a gap pressure method, and the like, and the pressure is not particularly limited. In addition, as a device that enables continuous heat and pressure molding, unwinding shaft, winding shaft, tension control device, line adjustment device (EPC), etc., as well as clean to maintain the quality as electronic circuit materials As the equipment, an adhesive roll, a static eliminator, a clean booth, etc. can be used as necessary.

  The thickness of the protective material used in the present invention is preferably 50 μm or less. If the thickness is greater than 50 μm, the molding temperature must be higher, and the dimensional change rate of the CCL becomes large. The dimensional change rate of CCL is determined by the linear expansion coefficient of each laminated material and the heating molding temperature. In order to reduce the dimensional change rate, it is necessary to reduce the difference in linear expansion coefficient of each laminated material. It is well known that the dimensional change rate is a value close to zero if the respective materials have the same linear expansion coefficient. However, actually, not only materials with the same linear expansion coefficient are laminated, but also different materials are often laminated. In that case, it is preferable to process at a lower temperature in order to reduce the difference in dimensional change due to thermal expansion between the materials as much as possible. In the present invention, by using a protective material of 50 μm or less, the heat conduction efficiency of the heating member and the laminated body of the heating and pressing apparatus can be increased, and the heating and pressing can be performed at a lower temperature, and the dimensional change rate can be improved. CCL can be obtained. Here, it is more preferably 25 μm or less. More preferably, it is 15 μm or less. Further, when the thickness of the protective material is increased, the price of the protective material is increased and the product cost is increased.

  The protective material used in the present invention is required to withstand the processing temperature. For example, when processing at 200 ° C. or higher, an aramid film, polyimide film, metal foil or the like having higher heat resistance is effective. Furthermore, an aramid film is particularly preferable from the viewpoint of the antioxidant effect and transportability of the metal foil.

When a thin protective material as described above is used, the oxygen transmission rate may be increased, which may cause oxidation of the copper foil. In this case, the oxygen permeability of the protective material is preferably 10 ml / m ² / atm / 24 hr or less. If it is larger than 10 ml / m ² / atm / 24 hr, it becomes difficult to use a metal foil that is not subjected to oxidation prevention treatment or is weakly treated, and oxygen permeation occurs while the product is cooled to room temperature after lamination, It will cause oxidation of the metal foil and will no longer serve as a protective material. More preferably, it is 5 ml / m ² / atm / 24 hr or less.

  The elastic modulus of the protective material is preferably 8 to 20 GPa. If it is less than 8 GPa, the film will not be distorted, handling properties will deteriorate, and the dimensional change rate of the product will increase. On the other hand, when the pressure is higher than 20 GPa, scratches on the pressure member, dust adhering to the pressure member, and the like are transferred to the product, so that it does not serve as a cushion for the protective material. More preferably, it is 10-15 GPa.

  The linear expansion coefficient of the protective material is preferably 20 ppm / ° C. or less. In addition, it is preferable to confirm the linear expansion coefficient in this invention at the temperature in 50-200 degreeC. If it is greater than 20 ppm / ° C., it will expand due to heat during heating and pressurization, causing wrinkles in the product. More preferably, it is 10 ppm / ° C. or less. However, the protective material is not particularly limited as long as it satisfies the above conditions, the product appearance is free of wrinkles and dents, can be peeled off from the product at room temperature, and can be recycled. .

Further, the protective material is not limited to various surface treatments for adjustment of peelability, adhesion, running property, and the like. Examples thereof include hydrolysis, corona discharge, low temperature plasma, physical roughening, easy adhesion coating treatment, release agent coating treatment, and the like. Here, considering the CCL manufacturing cost, it is preferable that the protective material is cheaper and can be recycled more times. Although the cost of the protective material affects the material and the yield, in general, a thinner film requires less raw material per m ² and can be manufactured at a low cost. In other words, it is important to effectively recycle thinner films.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Prior to the description of the examples, a method for evaluating physical properties and a method for heating and pressing a laminated plate will be described.

Method for measuring physical properties of protective materials Thickness Indicates the thickness at room temperature and is measured using a contact type digital micrometer MFC-101 manufactured by Nikon Corporation.
B. Oxygen permeability Based on ASTM D1434, measured under conditions of 20 ° C. and 65% relative humidity.
C. Elastic modulus Shows the elastic modulus at room temperature and is measured according to ASTM D-882.
D. Linear expansion coefficient The value of 50-200 degreeC was measured with the temperature increase rate of 10 degree-C / min under nitrogen by TMA8140 by Rigaku Corporation.

CCL creation method and characteristic evaluation method CCL Creation Method Here, a method for creating a double-sided CCL using a hot roll laminator will be described.
As shown in FIG. 1, 12 μm electrolytic copper foil (NA-VLP, Mitsui Kinzoku Co., Ltd.) is placed on both sides of a 25 μm thermoplastic polyimide film (UPILEX 25VT manufactured by Ube Industries, Ltd.) and further protected on both sides. The material was placed and a double-sided CCL was created using a hot roll laminator. Here, the protective material and the heating and pressing conditions are as shown in Examples and Comparative Examples. Moreover, the arrow shown in FIG. 1 represents the advancing direction of a protective material, a film, and copper foil.
B. Dimensional change rate evaluation method Based on JIS C6481, four holes are made in a laminated board, and each distance is measured (measurement value 1). Next, after etching and removing both sides of the copper foil, it was left in a constant temperature and humidity chamber of 20 ° C./60% RH for 24 hours, and the distance of each of the four holes was measured (measured value) as before the etching. 2) Then, the dimensional change rate was obtained by the following equation.

Dimensional change rate [%] = [(measured value 2−measured value 1) / measured value 1] × 100
C. Adhesive strength evaluation method When a copper foil pattern having a width of 2 mm is created by etching and the copper foil having a width of 2 mm is peeled off in a 90-degree direction using Tensilon (Orientec Co., Ltd., UTM-11-5HR type). The strength is measured (tensile speed: 50 mm / min).

Examples 1-4, Comparative Examples 1-5
In the CCL preparation methods, the protective materials and heating and pressing conditions shown in Examples and Comparative Examples in Table 1 were used. As a result, it was possible to obtain an excellent CCL having no defects in appearance such as wrinkles due to laminating and burning of copper foil due to high temperature and a dimensional change rate within ± 0.05. Furthermore, the appearance of the protective material after winding was the same as that before use and was recyclable.

Comparative Examples 6 to 10
In the CCL preparation method, the protective materials and heating and pressing conditions shown in Comparative Examples 6 to 10 in Table 2 were used. As a result, defects such as wrinkles due to lamination and copper foil burning due to high temperatures occurred, and the dimensional change rate became CCL.

The figure which showed the laminating apparatus which manufactures 2 layer CCL.

Explanation of symbols

1 Copper foil unwinding 2 Thermoplastic polyimide film unwinding 3 Protective material unwinding 4 Protective material winding 5 Product winding 6 Laminating roll 7 Protective material peeling roll

Claims (5)

A method for producing a laminated board in which two or more kinds of laminated materials including a metal foil are bonded together by a pressure heating molding device, wherein an aramid film having a thickness of 50 μm or less is provided between the pressing surface of the device and the laminated material. A method for producing a flexible metal laminate, characterized by performing pressure heating molding. The method for producing a flexible metal laminate according to claim 1, wherein an aramid film having a thickness of 50 µm or less is interposed between the pressing surface of the apparatus and the metal foil. The oxygen permeability of the aramid film is 10 ml / m ² The method for producing a flexible metal laminate according to claim 1, which is not more than / atm / 24 hr. The method for producing a flexible metal laminate according to claim 1, wherein the aramid film has an elastic modulus of 8 to 20 GPa. The method for producing a flexible metal laminate according to claim 1, wherein the aramid film has a linear expansion coefficient of 20 ppm / ° C. or less.

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