JPH0246790A - Fire retardant flexible printed circuit board - Google Patents

Abstract

PURPOSE:To obtain a low-cost and fire retardant flexible printed circuit board excellent in fire retardance and bondability, by making a polyethylene terephthalate film and a metal film in a unified body, via an adhesive agent layer composed of a specified composition of polyester resin, epoxy resin, phenol resin, curing accelerator and fire retardant agent. CONSTITUTION:A polyethylene terephtalate film and a metal foil are unified in a body via an adhesive agent layer composed of the following; polyester resin 100 part by weight, resin mixture 20-100 part by weight of epoxy resin 10-90wt.% and phenol resin 90-10wt.%, curing accelerator 0.5-20 part by weight and fire retardant 30-200 part by weight. As the curing accelerator, imidazole system compound, acid anhydride amine system, etc., can be used. As fire retardant agent, organic compound containing halogen such as tetrabromophthalic imide, compound containing phosphorus atom and nitrogen atom, and inorganic compound such as antimony trioxide and aluminum hydroxide are cited.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a flame-retardant flexible printed circuit board made of polyethylene terephthalate film (hereinafter referred to as PET film) and metal foil, which are useful for electronic circuits. It is.

(Conventional technology) In recent years, as electronic equipment has become lighter, thinner, smaller, and more sophisticated, demand for printed wiring boards has increased.In particular, flexible printed circuit boards made of plastic film and metal foil are being used in a wider range of applications. Demand is growing significantly.

These flexible printed circuit boards are required to have good properties such as heat resistance and electrical properties. The demand for improvement is increasing. A flame-retardant plastic film such as polyimide is mainly used for this flame-retardant flexible printed circuit board. However, although polyimide films have excellent heat resistance, electrical properties, and mechanical properties, they have the drawback of being very expensive.

On the other hand, PET film has poor heat resistance, but since it is inexpensive, it is used for printed circuit boards that do not require much heat resistance. However, since PET film itself is flammable, it is not suitable as a material for flame-retardant flexible printed circuit boards. Moreover, those made flame-retardant using a flame-retardant adhesive have the disadvantage that heat resistance, adhesiveness, etc. are significantly lowered.

In recent years, flame-retardant PET films in which a flame retardant is sandwiched between PET films have appeared on the market, but these also have the disadvantage of being relatively expensive compared to conventional films.

(Problems to be Solved by the Invention) The present invention provides a P
The present invention aims to provide an inexpensive flame-retardant flexible printed circuit board made of ET film and metal foil.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present inventors have conducted extensive research and have arrived at the present invention.

The gist of the present invention is to prepare a polyethylene terephthalate film and metal foil by: a) 100 parts by weight of polyester resin;
) A resin mixture of 10 to 90% by weight of an epoxy resin and B) 90 to 10% by weight of a phenolic resin.
20-100 parts by weight c) Curing accelerator
0.5-20 parts by weight 2) Flame retardant 30
The flame retardant flexible printed circuit board is integrated with an adhesive layer having a composition of ~200 parts by weight.

The present invention will be explained in detail below.

A) Used in the adhesive composition that is the most characteristic feature of the present invention
As the component polyester resin, one synthesized from the following polyols and acid components is used. Examples of polyols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol,
Dipropylene glycol, neopentyl glycol, trimethylolpropane, 1,4-butanediol, pentaerythritol, bisphenol-ethylene oxide adduct, bisphenol-brobylene oxide adduct, etc. Acid components include terephthalic acid, isophthalic acid,
Examples include adipic acid, maleic acid, fumaric acid, trimellitic acid, pyromellitic acid, and acid anhydrides thereof.

Of the epoxy/phenol resin mixture of ingredients A)
The epoxy resin may have two or more epoxy groups in one molecule, such as bisphenol A
type epoxy resin, glycidyl ether type such as novolak resin, cycloaliphatic epoxy resin, aromatic epoxy resin,
Halogenated epoxy resins and the like can be used alone or in combination of two or more.

B) Phenol resins include those obtained by reacting formaldehyde or paraformaldehyde with phenols such as phenol, cresol, xylenol, and alkylphenols.C) As curing accelerators, imidazole compounds such as 2- alkylimidazole, 2-alkyl-4-methylimidazole,
2-alkyl-4-ethylimidazole, 1-(2-cyanoethyl)-2-alkylimidazole [alkyl group preferably has 1 to 4 carbon atoms], 2-phenylimidazole, 2.4-diphenylimidazole, 2-phenyl -4-methylimidazole and the like are exemplified. Further, examples of the acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, and the like. Furthermore, examples of amines include diethylenetriamine, triethylenetetramine, metaxylene diamine, diaminodiphenylmethane, and the like, which may be used alone or in combination of two or more.

Examples of the flame retardant component (2) include halogen-containing organic compounds such as tetrabromophthalimide, tetrabromo-phthalic anhydride, and decabromodiphenyl ether; compounds containing phosphorus and nitrogen atoms; and inorganic compounds such as antimony trioxide and aluminum hydroxide. These can be used alone or in combination of two or more.

When blending the above components, a) polyester resin 10
If the amount of the epoxy/phenol resin mixture in the first component is less than 20 parts by weight, the soldering heat resistance will decrease, and the
If the amount exceeds 0.00 parts by weight, the peel strength will decrease. Regarding the blending ratio of the epoxy resin and phenolic resin components, if the epoxy is less than 10% by weight and the phenol is more than 90% by weight, the heat resistance will decrease, and if the epoxy is more than 90% by weight and the phenol is less than 10% by weight, the heat resistance will decrease. If present, flexibility and adhesive strength will be reduced. If the amount of the curing accelerator component (c) is less than 0.5 parts by weight, the reactivity will decrease, resulting in poor heat resistance and solvent resistance, and if it exceeds 20 parts by weight, the amount will be more than equivalent to the epoxy group. On the contrary, heat resistance decreases. If the flame retardant component (2) is less than 30 parts by weight, the flame retardancy will be lowered, and if it exceeds 200 parts by weight, the peel strength will be lowered.

The polyethylene terephthalate film used in the present invention may have a glass transition point as high as possible, and preferably has a thickness of 25 to 200 μm. As the metal foil, electrolytic copper foil, rolled copper foil, aluminum foil, tungsten foil, etc. are used.

The method for producing the flame-retardant flexible printed circuit board of the present invention involves applying an adhesive composition dissolved in a solvent to a PET film or metal foil in a dry state using a reverse roll coater, a comma coater, etc. 20~40μm
The adhesive is dried at 80 to 120°C for 3 to 10 minutes to evaporate the solvent and leave the adhesive in a semi-cured state. Lay the metal foil (or PET film) on the adhesive side of this adhesive-backed PET film (or metal foil), and
A flame-retardant flexible printed circuit board can be obtained by heat-pressing with a laminator and performing after-curing if necessary.

(Effects of the Invention) The present invention has made it possible to provide a flame-retardant flexible printed circuit board made of PET film and metal foil that is inexpensive and has excellent flame retardancy and adhesive properties.

EXAMPLES Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

All parts in the specific examples are by weight.

(Examples 1 to 3) For 100 parts of the polyester resin shown in Table 1 (Vylon 30P or 300, manufactured by Toyobo Co., Ltd.), A) as an epoxy resin, bisphenol A type epoxy resin Epicoat 828 (manufactured by Yuka Shell Co., Ltd.) / novolac type epoxy resin Epicoat 154 = 7/3 mixture and B) novolac type phenol formaldehyde resin (phenol equivalent: 107) were added in the amounts shown in Table 1 at a weight ratio of A/B = 1/1, As a curing agent, 1 part of 2-ethyl-4-methylimidazole and 5 parts of trimellitic anhydride were added, and a flame retardant (in Table 1, X: 5bzO+, Y: PO64
P: Polydibromophenylene oxide: Grea
t Manufactured by Lakes Chemica 1, Z: BT
-93=Ethylethylenebistetrabromophthalimide Eth
(manufactured by Y1), two of the three types of X, Y, and Z (7) were added at the blending ratio and amount (parts) shown in Table 1, and 30
% dioxane solution and uniformly dispersed using a ball mill to obtain an adhesive solution.

Next, this adhesive solution was applied to a coating thickness of 25 μm after drying.
Coat it on a 75 μm PET film so that it becomes 80 μm.
Heat and dry at ℃ x 2 minutes and 120℃ x 5 minutes to a thickness of 35μ
m copper foils were laminated at a temperature of 140°C and a roll pressure of 5.
kg/cm and a speed of 2 m/min using a roll laminator. Then, put it in the oven at 80°C for 2 hours.
and after-cured at 140° C. for 5 hours. Table 1 shows the characteristics of the flame-retardant flexible printed circuit board thus obtained.

(Comparative Examples I to 3) In Comparative Example 1, in Example 2, the added amount of flame retardant was 140
A substrate was obtained by laminating under the same conditions except that the portion was changed to 25 parts. This characteristic is shown in Table-1.

Comparative Example 2.3 is obtained by laminating under the same conditions as in Example 2, except that the amounts of the epoxy and phenolic resins (1) component were changed to 15 parts and 150 parts, respectively, and the amount of flame retardant added was slightly changed. A substrate was obtained and its characteristics were measured and shown in Table 1.

The method for measuring the properties of the substrates shown in these specific examples is as follows.

(Measurement method) 1) Peel strength: Performed in accordance with JI 5C6481 1
The copper foil was peeled off from a sample with a width of 0 mm in a direction of 90° C. at a speed of 50 mm/min.

2) Soldering heat resistance: [Normal state] is determined by floating the sample in a solder bath for 30 seconds, and then measuring the temperature at which no blistering occurs. [Moisture absorption]: sample at 40'CX90%RH
After absorbing moisture under XIHr conditions, it was floated in a solder bath for 30 seconds and checked for appearance, blisters, etc.

3) Flame retardancy: Conduct a combustion test in accordance with UL-94 standards. The UL-94 standard defines flame retardancy as V-OlV-1, V-
2, HB (7) 4 G: Ranked, ■-〇 is the most excellent in flame retardancy.

Claims (1)

[Scope of Claims] Polyethylene terephthalate film and metal foil, a) 100 parts by weight of polyester resin, b) 20 to 100 parts by weight of a resin mixture of A) 10 to 90 parts by weight of epoxy resin and B) 90 to 10 parts by weight of phenol resin. Parts by weight c) A curing accelerator (d) 0.5 to 20 parts by weight d) A flame retardant flexible printed circuit board integrated through an adhesive layer having a composition of 30 to 200 parts by weight.