JPS6295887A - Flexible printed circuit substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flexible printed circuit board with excellent flame retardancy.

[Prior art]

Conventionally, flexible printed circuit boards having flame retardancy equivalent to UL94V-0 have been based on films of polyimide, polyamideimide, fluororesin, etc., but these are expensive and lack versatility. Furthermore, when a glass woven fabric or a nonwoven fabric is used as the base material, the flame retardance and other properties are excellent, but the flexibility is poor.

On the other hand, there are films made of polyester, polyetherimide, dirietherketone, polysulfone, etc., which are low-cost and have excellent flexibility, electrical properties, and dimensional stability. , UL94V- for flexible printed circuit boards based on these films.
It was impossible to achieve flame retardancy equivalent to zero.

[Purpose of the invention]

As a result of research aimed at solving the above-mentioned drawbacks and obtaining an economical substrate that passes UL94V-0, the present invention has been developed by coating one side of a plastic film with a specific resin composition and a specific flame-retardant film. UL94V-
The present invention was achieved by discovering that it is possible to pass 0.

[Structure of the invention]

In the present invention, a coating layer of a resin composition mainly composed of an epoxy resin and containing a phosphorus compound and/or a halogen compound is coated on one side of a plastic film to a thickness of 3 to 18 cm.
μm, and a metal foil is bonded to the other side of the film via a flame-retardant adhesive containing one of (a) to (d) and having a thickness of 10 to 40 μm. The present invention relates to a characteristic flexible printed circuit board.

(a) Obtained by copolymerization of 15 to 35% by weight of acrylonitrile, 55 to 83% by weight of an ester of an alcohol having 5 or less carbon atoms and acrylic acid or methacrylic acid, and 2 to 10 TL of acrylic acid or methacrylic acid. Acrylic resin ゛)
100 heavy background (b) epoxy resin 5
~70 parts by weight (c) Polyisocyanate 20-10
0 parts by weight (d) Flame retardant (a) to (
25 to 100 parts by weight per 100 parts by weight of the mixture c) Examples of the plastic film include polyester film, polyetherimide, polyether ether ketone,
Hirisulfone, polyethersulfone, polyethylene film, -lipropylene film, etc. can be used. The thickness of this film is 25-75 μm.

The coating layer uses an epoxy resin as a product and contains a phosphorus compound and/or a nitrogen compound.

As the epoxy resin, bisphenol-based, resol-based, novolak-based, ether ester-based glycidyl ethers, cycloaliphatic epoxy compounds, etc. can be used, and brominated ones are preferably used. By using a brominated epoxy resin, it is possible to reduce the amount of liquid phosphorus compounds and halogen compounds that cause the coating layer to become sticky. In addition, curing agents for epoxy resins include amines such as diethylenetriamine, triethylenetetramine, diethylaminopropylamine, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, Various acid anhydrides such as maleic anhydride can be used.

Examples of phosphoric acid compounds and halogen compounds include tricresyl phosphate, cresyl diphenyl phosphate, octyldiphenyl phosphate, Examples include ethane, tribromozoloethane, I+2-sifukumo-3-chloropronozone, and the like. Furthermore, halides of phosphoric acid compounds, such as tris(2,3-dibromopropyl) phosphate, tris(monobromopropyl) phosphate, tris(bromochloropropyl) phosphate, tris(2
, 3-dichloropropyl) phosphate, tris(monochloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, tris(2-chloroethyl) phosphate, tris(2-bromoethyl) phosphate, bis(2°3-Schif') lomoprovir)-2,
3-dichloropropyl phosphate, trichloroethyl phosphite, bis(chloropropyl) monophenytl phosphate, bis(chlorozolovir) monooctyl phosphate, tris-2 chloroethyl phosphate, etc. can be used. These phosphorus compounds, halogen compounds, and halides of phosphorus compounds may be used alone or in combination.

Additionally, the coating layer contains flame-retardant inorganic compounds such as antimony trioxide, aluminum hydroxide, and barium borate.
Silica, alumina, mica, titanium oxide, zirconia,
A filler-free material such as calcium silicate, magnesium hydroxide, magnesium oxide, calcium carbonate, or silicon carbide may be added. Furthermore, in addition to these, melamine resins, polyester resins, acrylic resins, etc. may be blended according to various purposes.

The thickness of the coating layer should be 3 to 18 μm. If the thickness is less than 3 μm, the target flame retardance cannot be achieved. If the thickness exceeds 18 μm, the coating workability will be significantly reduced, and the bending resistance of the flexible printed circuit board will also be reduced.

Regarding each component of the adhesive, component (a) must contain 15 to 35 parts acrylonitrile. 15 layers! If it is less than Jk, the adhesive strength and iron soldering heat resistance will decrease. As the acrylonitrile component increases, the adhesive strength increases.
The iron soldering heat resistance is improved, but if the iron soldering temperature exceeds 35 degrees, the flexibility decreases. In order to achieve sufficient adhesive strength, iron soldering heat resistance, and flexibility, a value of 15 to 351 is desirable.

Examples of esters of alcohols having carbon atoms of 5 or less and acrylic acid or methacrylic acid include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, egyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, etc. can be given. The amount of acrylic or methacrylic must be 2 to 10% by weight.

If it is less than 2, the adhesive strength and iron soldering heat resistance will decrease. If it exceeds 10% by weight, flexibility decreases. As the resin/component (b), common resins such as bisphenol, resol, novolac, and ether ester glycidyl ethers and cycloaliphatic epoxy compounds and their brominated products can be used. If the Eixy resin is less than 5 parts by weight, the flow of the entire adhesive will be small, making it difficult to adhere uniformly to metal foil by heat-press bonding, especially roll lamination, and the adhesive strength, iron soldering heat resistance, etc. will be unstable. . If it exceeds 70 parts by weight, flexibility will decrease. As a polyisocyanate, 2.6-)
Lylene diisocyanate, 2,4-tolylene diisocyanate type, diphenylmethane-4,4'-diisocyanate type, polymethylene polyphenyl base? Riisosia 4-
Various types of insea adhesives such as hexamethylene diisocyanate type and hexamethylene diisocyanate type can be used. In particular, polyisocyanate made from hexamethylene diisocyanate (hereinafter referred to as ■■) has excellent weather resistance, and the adhesive strength of the circuit portion of a flexible printed circuit board is less likely to deteriorate due to heat. F1? The ratio of incyanate to xylene fat is 0.4 to 1.2.
If it is less than 0.4, the soldering heat resistance and solvent resistance will deteriorate, and if it exceeds 1.2, the varnish life will be extremely shortened, and preferably from 0.6 to 0.9.

As the flame retardant, halogen compounds such as bromine compounds and chlorine compounds, phosphorus compounds, halogen-containing phosphate esters, and the like can be used. The amount added is as follows (a) to (c) above.
) is required to be 25 to 100 parts by weight per 100 parts by weight of the mixture. If it is less than 25 parts by weight, the flame retardant element content is insufficient, and if it is less than 100 parts by weight? Exceeding this will reduce the adhesive strength. Furthermore, flame-retardant inorganic compounds such as antimony trioxide, water-dispersed aluminum, and barium borate may be added.

When these inorganic compounds are added, the total particle size must be 1 μm or less, and the total solid content must be 45 mm or less. If the particle size exceeds 1 μm, the sedimentation rate in the varnish will be high and the coating workability will be poor. Moreover, unevenness occurs on the surface of the adhesive, which impairs its appearance. The amount added is 45 weights! If it exceeds -%t-, the adhesive flow becomes small, roll lamination properties are reduced, and adhesive strength is further reduced.

Furthermore, the adhesive for the flexible printed circuit board of the present invention includes inorganic compounds such as silica, alumina, mica, titanium oxide, zirconia, calcium silicate, magnesium hydroxide, magnesium oxide, calcium carbonate, and silicon carbide, stabilizers, and interfaces. Various commonly used additives such as activators may be blended depending on the purpose, or glass cloth, Kevlar cloth, etc. may be impregnated with an adhesive. In addition, the thickness of the adhesive is 10 to 40 μm.
It is necessary to do so. If the thickness is less than 10 μm, the flame retardant adhesive strength will decrease, and if it exceeds 40 μm, the flexibility will decrease. It is preferably 20 to 30 Iirr1.

As the metal foil used as the printed circuit board of the present invention, in addition to copper foil, various metal foils such as copper alloy (eg, brass), aluminum, iron, nichrome, etc. may be used. In addition to flexible steel clad plates, these include insulating coverlays of flexible printed circuits, laminated products of multiple flexible printed circuits, and those with hard reinforcing plates bonded to them.

〔Effect of the invention〕

According to the present invention, it was possible to obtain a flexible printed circuit board that was inexpensive and had flame retardancy equivalent to UL94V-0.

Example 1 Brominated epoxy resin (Dainippon Ink, Epicron) 15
3) as the main component, triethylenetetramine as the curing agent, and tris(2) as the halide of the phosphorus compound.
, 3-dibromozolovir) phosphate is added to give 1.3% by weight of phosphorus in total solids. This resin composition was coated on one side of a 25 μm thick 4-liester film to a thickness of 15 μm. Next, Table 1
The other side of the film was coated with an adhesive prepared according to recipe table (&1) to a thickness of 30 μm, and a copper foil having a thickness of 35 mm was laminated thereon. Example 2 The same resin composition as in Example 1 was coated on one side of a 25 μm thick etherimide film to a thickness of 10 μm. Next, an adhesive prepared according to the recipe (A1) in Table 1 was applied to the other side of the film to a thickness of 30 μm.
35 μm thick copper foil was laminated thereon.

Example 3 Brominated poxy resin (Dainippon Ink, Evicron 153
), a melamine resin, an acrylic resin, a polyester resin, and a halokenide of a phosphorus compound, tositetris-2-chloroethyl phosphate, are added so that the phosphorus in the total solid content is 1.2% by weight. Furthermore, in order to improve the tackiness of the flame retardant layer and eliminate uneven coating during coating, silica with a particle size of 0.1/Am was added to the solid content at 3% by weight.
This resin composition was added to a thickness of 25 μm.
d One side of the IJ ester film was coated to a thickness of 15 μm. Next, the recipe in Table 1 (A1
) was coated on the other side of the film to a thickness of 30 μm, and a 35 μm thick copper foil was laminated thereon.

Comparative Example 1 Composition table (&1) in Table 1 for HoIJ ester with a thickness of 25 μm
The adhesive prepared according to the above was coated to a thickness of 30 μm, and a 35 μm thick copper foil was laminated thereon.

Comparative Example 2 The same resin composition as in Example 1 was coated on one side of a 25 μm thick ester film to a thickness of 18 μm. Next, the other side of the film was coated with an adhesive prepared according to Table 1 (42) to a thickness of 30 μm, and a 35 μm thick copper foil was laminated thereon.

Table 1 Adhesive formulation table *1 32 parts by weight of acrylonitrile, 100 parts by weight of acrylic [n-dipyl, 13 parts by weight of acrylic Fj, 4 parts by weight of toluene
A mixture consisting of 0.00 parts by weight was heated at 60 to 65°C in a nitrogen stream.
Compounds reacted with stirring for 16 hours (160 parts by weight→solid content 40 parts by weight) *2 Bisphenol A type engineered epoxy resin epoxy *190 *3 Coronate E manufactured by Nippon Polyurethane) (*4 Daihachi Chemical CR- 8 *5 particle diameter 0.4 μm or more, the flame retardance and adhesive strength of Examples 1 to 3 and Comparative Example 1.2 are as shown in Table 2.

Table 2

[Brief explanation of drawings]

1 and 2 show the layer structure of the flexible printed circuit board of the present invention.

Claims (1)

[Claims] A coating layer of a resin composition mainly composed of an epoxy resin and containing a phosphorus compound and/or a halogen compound is provided on one side of a plastic film to a thickness of 3 to 18 μm, while the following ( Contains a) to (d) and has a thickness of 10
A flexible printed circuit board comprising a metal foil bonded to the other surface of the film via a flame-retardant adhesive of ~40 μm. (a) Acrylic obtained by copolymerizing 15 to 35% by weight of acrylonitrile, 55 to 83% by weight of an ester of an alcohol having 5 or less carbon atoms and acrylic acid or methacrylic acid, and 2 to 10% by weight of acrylic acid or methacrylic acid. 100 parts by weight of system resin (b) 5 to 70 parts by weight of epoxy resin (c) 20 to 100 parts by weight of polyisocyanate (d) Flame retardant 25 to 100 parts by weight per 100 parts by weight of the mixture of (a) to (c) above