JP2002361770A - Cover lay film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To industrially provide a novel cover lay film which has excellent solder heat resistance, adhesive properties and storage stability, low halogen content and electromagnetic wave shielding properties, and also to industrially provide a flexible printed circuit board. SOLUTION: The cover lay film comprises an insulating plastic film layer, an adhesive layer and a protective layer. The cover lay film further comprises a conductive layer having an electric resistance value of 500 Ω/square or less on at least one surface of the plastic film layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel coverlay film and a flexible printed circuit board which are used for protecting a substrate for a printed wiring board and which are excellent in solder heat resistance, adhesiveness and storage stability and have electromagnetic wave shielding properties.

[0002]

2. Description of the Related Art In recent years, with the increase in the frequency of electronic circuits such as computers, the problem of malfunctions and noise occurring in other electronic devices due to electromagnetic waves emitted from such electronic circuits has been regarded as a problem. For this reason, countermeasures such as providing an electromagnetic wave shield in a casing accommodating an electronic circuit have been taken. When an electromagnetic wave shielding material is provided on a printed circuit board such as a flexible printed wiring board, it must be flexible. As a method of providing an electromagnetic wave shielding material, there is a method of providing a conductive layer on an insulating film of a copper-clad laminate for a flexible printed wiring board (JP-A-1-287999). In addition, when a circuit pattern is formed, a number of steps such as etching are required, so that the stability of the conductive layer becomes insufficient.

[0003] In addition, as electronic devices have been increasingly miniaturized and densified, the role of a flexible printed circuit board has become important for mounting components in a narrow space. Demands for fine patterning and high performance of flexible printed circuit boards have been increasing, and in particular, further improvement in solder heat resistance, adhesiveness, and electrical insulation has become necessary. Regarding solder heat resistance, a higher temperature is required because the solder is put into a reflow furnace at a higher temperature with the lead-free solder.

[0004] On the other hand, as the influence on the environment is regarded as a social problem, the regulation of flame retardancy required for electric and electronic products is shifting to higher safety in consideration of safety for the human body. That is, it is demanded that not only electric and electronic products are not easily burnt but also generate less harmful gas and smoke. Flame retardants that have been used in printed wiring boards (copper-clad laminates) such as glass epoxy boards, flexible printed boards, and encapsulants for mounting electronic components for safety reasons such as fire prevention and delay, In particular, derivatives mainly containing tetrabromobisphenol A (brominated epoxy resins and the like) are widely and generally used. And, as the flame-retardant adhesive used in such applications, for example, a saturated copolymerized polyester resin as a main component, a brominated organic flame retardant and an inorganic filler added thereto, or a brominated epoxy resin as well, Flame-retardant adhesive sheets using brominated polyvinyl phenol are known.

[0005]

SUMMARY OF THE INVENTION The present invention solves such problems and has excellent solder heat resistance, adhesiveness, and storage stability.
It is an object of the present invention to provide a novel cover lay film and a flexible printed board having a low halogen content and an electromagnetic wave shielding property.

[0006]

That is, the present invention relates to a coverlay film having an insulating plastic film layer, an adhesive layer and a protective layer, wherein at least one surface of the insulating plastic film layer has an electric resistance value of 500 Ω /. □ A coverlay film characterized by having a conductive layer of:

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a cover lay film having an insulating plastic film layer, an adhesive layer and a protective layer provided with a conductive layer, wherein the conductive layer is at least one of the insulating plastic film layers. Must have on the surface. Preferably, the surface on which the adhesive layer is not present is preferable, but it may be on the adhesive layer surface or on both surfaces.

[0008] The conductive layer laminated on the insulating plastic film layer used in the present invention is not particularly limited as long as it has conductivity.
Platinum, palladium, rhodium copper, aluminum, nickel, tungsten, chromium, titanium, tin, lead and other metals, tin oxide, indium oxide, antimony oxide, titanium oxide, zirconium oxide, or indium oxide-tin oxide, tin oxide- Examples include metal oxides such as antimony oxide. More preferably, high conductivity silver, copper,
Gold and aluminum.

As a method of laminating the conductive layer on the insulating plastic film layer, a general thin film forming method can be used, and examples thereof include a vacuum deposition method, a sputtering method, and an ion plating method. More preferably, those formed by a vacuum evaporation method or a sputtering method are preferable.

In the present invention, the surface electric resistance of the conductive layer is 50.
0 Ω / □ or less, preferably 100 Ω / □ or less, more preferably 50 Ω / □ or less. These conductive layers may be a single layer, or may be a multilayer of two or more layers.

The adhesive layer used in the present invention is not particularly limited, and examples thereof include a thermosetting type in which a thermoplastic resin mixed with a thermosetting resin by modification so as to be chemically bonded is used. . Examples of the thermosetting resin include an epoxy resin, a phenol resin, a melamine resin, a xylene resin, a furan resin, a cyanate ester resin, and the like. Examples of the thermoplastic resin include acrylonitrile-butadiene rubber-based, polyamide-based, polyester-based, and polyacryl-based resins. As the thermoplastic resin, it is more preferable to use acrylonitrile butadiene rubber from the viewpoint of adhesiveness. These thermosetting resins and thermoplastic resins may be used alone or in combination of two or more.

On the other hand, the halogen content in the adhesive layer used in the present invention is preferably 0.09% or less (J
PCA standard, based on JPCA-ES-01-1999). In order to reduce the halogen content to 0.09% or less, it is preferable to use a non-halogen type flame retardant. The non-halogen flame retardant is not particularly limited, for example,
Examples thereof include a phosphorus-containing compound, a nitrogen-containing compound, a hydrated metal compound, and a silicon compound. These may be used alone or as a mixture of two or more.

The heat-resistant temperature of the adhesive layer used in the present invention is 2
50 ° C. or higher is preferred. For example, it is possible to use a filler of inorganic particles for the adhesive layer. As inorganic particles,
Metal hydroxides such as aluminum hydroxide, magnesium hydroxide, calcium aluminate hydrate, metal oxides such as silica, alumina, zinc oxide, antimony trioxide, antimony pentoxide, magnesium oxide, titanium oxide, and calcium carbonate And the like, and carbon black. These may be used alone or in combination of two or more.

The insulating plastic film referred to in the present invention is a film having a thickness of 5 to 200 μm made of a plastic such as polyimide, polyester, polyphenylene sulfide, polyether sulfone, polyether ether ketone, aramid, polycarbonate, polyarylate and the like. Yes, a plurality of films selected from these may be laminated and used. If necessary, a surface treatment such as hydrolysis, corona discharge, low-temperature plasma, physical roughening, and easy adhesion coating treatment can be performed.

The protective layer referred to in the present invention is not particularly limited as long as it can be peeled off without impairing the form of the adhesive layer. For example, polyester, polyolefin, polyvinyl chloride, polyvinyl fluoride coated with silicone or a fluorine compound, etc. Examples include plastic films of vinylidene, polyphenylene sulfide, etc., paper laminated with these, and paper impregnated or coated with a resin having releasability.

The flexible printed wiring board has a structure in which the coverlay film is laminated on a copper-clad laminate. The copper-clad laminate is made by laminating copper foil on one or both sides of an insulating film with an adhesive, or laminating copper foil on one or both sides of an insulating film without an adhesive. One. The flexible printed wiring board can be manufactured by laminating the coverlay film on the copper foil surface of the copper-clad laminate, bonding them together by using a heating press or a heating roll device, and further heating and curing.

[0017]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. Before starting the description of the embodiment, an evaluation method will be described.

(1) Surface Electric Resistance Value A sample cut to a width of 35 mm is placed on a rubber sheet having a rubber hardness (according to JIS K6301-1975) of about 60,
A measuring electrode having a 2 mm thick palladium plate set at an interval of 35 mm is placed at a position orthogonal to the sample, a load of 3 kg is applied, and the resistance between the terminals is measured using a digital tester (VOAC707 manufactured by Iwasaki Communication Equipment Co., Ltd.). The resistance value was read directly.

(2) Electromagnetic Wave Shielding Effect The KEC method (based on MIL-STD285 which is a standard measurement method of Kansai Electronics Industry Promotion Center)
A shield box in which a transmitting antenna and a receiving antenna are installed in a short distance (MA8602B, manufactured by Anritsu Corporation)
The sample cloth is held at a predetermined position (between the antennas) in the inside, and the frequency is changed within a range of 100 to 600 MHz, and the transmission is performed. ) Made by Advantest), and the electromagnetic wave shielding property in the near field can be evaluated. Those having the attenuation state of 30 dB or more are evaluated as good.

(3) Heat resistance of solder The cover film is made of 35 μm electrolytic copper foil (Nikko Gould
160 ° C on the glossy surface of Foil Co., Ltd., JTC foil)
Lamination was carried out under a pressing condition of 3 MPa for 30 minutes to prepare a sample for evaluation. The cover lay film had an adhesive thickness of 30 μm. The measurement is based on JIS-C6481.
The method was performed in accordance with the following method. 25m pressed on electrolytic copper foil
An m-square sample was placed in an atmosphere of 22 ° C. and 90% RH for 2 minutes.
After conditioning for 4 hours, the sample was immediately floated on a solder bath for 30 seconds, and the maximum temperature without swelling and peeling was measured.

(4) Preparation of coverlay film Preparation of Polyimide Film with Conductive Layer A predetermined metal was adhered to a 25 μm-thick polyimide film (“Kapton” 100 V, manufactured by Du Pont-Toray Co., Ltd.) by a sputtering method or a vacuum deposition method to laminate a conductive layer to obtain a conductive film. . Sputtering degree of vacuum 1
The ^test was carried out at 0 ^-2 Pa under the introduction of an Ar / O ₂ mixed gas.
Vacuum deposition was performed at a degree of vacuum of 10 ⁻³ Pa.

B. Preparation of coverlay film with conductive layer 100 parts by weight of carboxylated NBR (manufactured by JSR Corporation, PNR-1H) and polyimide resin (Japan Epoxy Resin Co., Ltd.)
50 parts by weight of "Epicoat" 834), epoxy resin: polyfunctional phosphorus compound (FX-2 manufactured by Toto Kasei Co., Ltd.)
79BEK75) 100 parts by weight, 3,3'-diaminodiphenylsulfone 6 parts by weight Aluminum hydroxide (H-43, manufactured by Showa Denko KK) 30 parts by weight An adhesive having a composition of 30 parts by weight was coated with a coating having a thickness of 30 μm. And dried at 150 ° C. for 5 minutes, and a 25 μm-thick release paper with a silicone release agent was laminated to obtain a coverlay film. For the measurement of the electromagnetic wave shielding effect, the coverlay film with a conductive layer prepared in B was used as a sample.

Examples 1 to 5 and Comparative Examples 1 and 2 Each of the metals shown in Table 1 was fixed on a polyimide film by the method indicated by A so as to have the electric resistance values shown in Table 1, and the effect of shielding electromagnetic waves was obtained. Was measured. Table 1 shows the characteristics.

Further, the flexible printed wiring board obtained according to the present invention from the examples and comparative examples in Table 1 has sufficient electromagnetic wave shielding properties equal to or higher than that of metal foil, and has a thin conductive layer. It had the same flexibility as the wiring board.

[0025]

[Table 1]

[0026]

According to the present invention, it is possible to industrially provide a novel coverlay film and a flexible printed circuit board having excellent solder heat resistance, adhesiveness and storage stability, a low halogen content and an electromagnetic wave shielding property. it can.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F100 AB24 AK01A AK49 AR00B AR00D AS00C BA04 BA07 BA10A BA10D EH66 EJ91C GB41 JA20 JD08 JG01D JG04A JJ03 JL11B 5E314 AA25 AA33 AA34 AA36 BB01 CG01 FF01 GG03

Claims (5)

[Claims] 1. A coverlay film having an insulating plastic film layer, an adhesive layer, and a protective layer, wherein at least one surface of the insulating plastic film layer has a conductive layer having an electric resistance of 500Ω / □ or less. A coverlay film characterized by the following. 2. The conductive layer comprises at least one of a metal and a metal oxide.
The coverlay film according to claim 1, comprising a seed. 3. The method according to claim 1, wherein the halogen content in the adhesive layer is 0.1.
The coverlay film according to claim 1, wherein the content is not more than 09%. 4. The coverlay film according to claim 1, wherein the heat-resistant temperature of the adhesive layer is 250 ° C. or higher. 5. A flexible printed wiring board using the cover lay film according to claim 1.