JPH07126585A - Cover lay film - Google Patents

Abstract

PURPOSE:To provide a cover lay film used for protecting a flexible printed circuit and having advantages such as excellent humidity resistance and machinability and no necessity for a release agent. CONSTITUTION:An adhesive comprising 100 pts.wt. polyester resin of an acid value of 70-150, 20-150 pts.wt. mixture of 10-90wt.% epoxy resin with 90-10wt.% phenolic resin, 2-20 pts.wt. inorganic fine powder, 0.5-10 pts.wt. cure accelerator and 1-10 pts.wt. reactive diluent is applied to either surface of a heat-resistant insulating plastic film and dried to a tack-free state. The tack-free adhesive surface is laid under pressure on a release paper formed by sticking poly-4- methylpentene-1 films to both surfaces of a base paper to obtain the objective film.

Description

Detailed Description of the Invention

[0001]

The present invention has excellent moisture resistance, releasability, and
The present invention relates to a coverlay film for protecting a flexible printed circuit, which has machinability and does not require a release agent.

[0002]

2. Description of the Related Art In recent years, electronic products have become light, thin, short, and small.
Demand for printed circuit boards has increased along with higher performance, and in particular, flexible printed circuit boards have expanded their use range and demand. As a result, the use of protective coverlay films for flexible printed circuits has increased,
It is desired to improve its performance. In general, a coverlay film has a B stage (hereinafter referred to as a semi-cured adhesive).
It consists of a heat-resistant insulating film with heat-resistant adhesive and a release paper. This release paper has polyethylene (hereinafter PE), poly-4-methylpentene-1 on one or both sides of the base paper.
(Hereinafter referred to as TPX) or polypropylene (hereinafter referred to as PP) film laminated, polyvinylidene chloride (hereinafter referred to as PVdC) coated on both sides of the base paper, PE or PP film attached to one side of the base paper PVdC on the opposite side
There are those coated with. Further, it is known that one or both of these release papers are subjected to a release treatment with a silicone release agent or the like.

[0003]

The above-mentioned release paper, which has a PE, PP or TPX film bonded to only one side of the base paper, or a PVdC-coated one, is not provided with a moisture absorption / release prevention property. Due to the difference in the dimensional change rate due to the humidity change between the heat resistant insulating film with adhesive and the release paper, there is a drawback that the cover lay film is curled during the low humidity winter and the high rainy season. Curling does not occur when PE and PP films are attached to both sides, PVdC is coated on both sides of the base paper, and PE or PP film is attached to one side of the base paper and PVdC is coated on the opposite side. Although it can be prevented, it has a defect that the punchability of the coverlay film and the releasability from the adhesive surface are inferior. In order to improve the releasability from this adhesive surface, a releasing treatment is performed with a silicone-based releasing agent or the like, and this releasing agent is transferred to the heat-resistant adhesive surface of the B stage and the adhesive has Decreases the adhesive strength with the substrate. The same applies to the polymer-coated paper having only one side. In addition, when the PE and PP films are bonded together, the PE and PP films have a cushioning effect when the cover lay film is punched, making it difficult to punch holes as usual.
In particular, it is remarkable for those attached on both sides. Due to the above, double-sided TPX film-coated release paper, which has excellent punchability and flatness and does not require release agent treatment, has come to be used. Poorly, there was a problem that the insulating film with the heat-resistant adhesive forming the coverlay film and the release paper were easily separated.

Focusing on the adhesive, conventionally, as an adhesive for the coverlay, NBR / phenol resin, epoxy / phenol / NBR, NBR / epoxy resin, epoxy / polyester resin, epoxy / acrylic resin, Acrylic resins and the like have been used, but all have advantages and disadvantages, and in reality, few satisfy the adhesiveness with the release paper on which the double-sided TPX film is attached. The present invention intends to provide a coverlay film in which these problems, particularly, the adhesive strength between the double-sided TPX film-coated release paper and the heat-resistant adhesive is improved from the viewpoint of the adhesive composition.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have paid attention to adhesives in terms of releasability and heat resistance,
As a result of various investigations for a heat-resistant adhesive composition having good adhesion to the TPX film of the release paper, the present invention has been achieved, and the gist is as follows: 1) One side of heat-resistant insulating plastic film A coverlay film obtained by pressure-bonding a surface which is semi-cured by applying an adhesive having the following composition and 2) a release paper in which a poly-4-methylpentene-1 film is attached to both surfaces of a base paper. It is in. B) Acid value
Polyester resin of 70 to 150: 100 parts by weight, b) Mixture of 10 to 90% by weight of epoxy resin and 90 to 10% by weight of phenolic resin: 20 to 150 parts by weight, c) Fine inorganic powder: 2
˜20 parts by weight, d) curing accelerator: 0.5 to 10 parts by weight, e) reactive diluent: 1 to 10 parts by weight.

The present invention will be described in detail below. First, the composition of the heat resistant adhesive most suitable for the present invention will be described. B) Polyester resin with an acid value of 70 to 150 has a softening point
It is selected from those above 120 ℃. If the acid value is less than 70, the solder heat resistance will decrease, and if it exceeds 150, the peel strength will decrease. In addition, when the softening point is lowered, the adhesive surface becomes sticky during handling, the thermal softening during heating is large, and the high temperature characteristics deteriorate.
As such a polyester resin, the one synthesized from the following polyols and acid components is used. Polyols: ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, trimethylolpropane, 1,4-butanediol, pentaerythritol, bisphenol A-ethylene oxide adduct, bisphenol A-propylene oxide adduct. Things etc. Acid component: terephthalic acid, isophthalic acid, adipic acid, maleic acid, fumaric acid, trimellitic acid, pyromellitic acid and their acid anhydrides.

Among the epoxy / phenolic resin mixture of component (b), the A) epoxy resin may be one having two or more epoxy groups in one molecule, such as bisphenol type epoxy resin and novolac resin. Glycidyl ether type, cycloaliphatic type epoxy resin, aromatic type epoxy resin, halogenated epoxy resin, etc. alone or 2
A mixture of two or more species can be used. Further, B) phenol resin includes phenol, cresol, xylenol,
Examples thereof include those obtained by reacting phenols such as alkylphenols with formaldehyde or paraformaldehyde.

Examples of the fine particle inorganic powder of component (c) include silica powder, alumina powder, mica, talc, calcium carbonate, clay, titanium oxide, magnesium oxide, silicon carbide, boron nitride, and the like, but especially ultrafine particles. The anhydrous silica, aluminum oxide, titanium oxide and the like are preferable, and one kind or two or more kinds of them can be used in combination. The particles of the inorganic powder have a particle size of 2 μm or less, preferably 1 μm or less. If the particle size exceeds 2 μm, the surface properties (irregularities) of the film deteriorate, and the demand for fine patterning cannot be met. That is, in recent years, a flexible printed circuit has been made into a fine pattern and a pattern of several tens of μm has been put into practical use, and it is preferable to use an inorganic powder as fine as possible in the resin composition. The use of this powder improves the moisture absorption resistance of the resin and reduces the strain of the adhesive due to thermal shock.
Incidentally, it is convenient to carry out a hydrophobic treatment in order to improve the fixability and water resistance of these powders to the resin matrix. For this purpose, chlorosilanes such as dimethyldichlorosilane,
A treating agent such as a silane coupling agent such as silicone oil, alkyltriethoxysilane, or methyltriethoxysilane is used. The reason why the use of the inorganic powder further improves the moisture resistance soldering property and the like is considered to be because the heat resistance and the moisture absorption property of the resin are improved and the strain of the adhesive due to thermal shock is reduced.

As the curing accelerator of the component (d), an imidazole compound 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 can be mentioned. An acid anhydride is also used, and examples thereof include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, and the like. Examples of amines include diethylenetriamine, triethylenetetramine, metaxylenediamine, diaminophenylmethane and the like. These may be used alone or in combination of two or more.

Examples of the reactive diluent of component e) include those having one or more glycidyl groups, ester groups, ether groups and the like in the molecule of glycidyl ester type or glycidyl ether type. Examples thereof include C _{10 to} C ₁₅ fatty acid monoglycidyl ester, C _{2 to} C ₂₀ alkyl monoglycidyl ether, C _{2 to} C ₅ alkylphenol monoglycidyl ether, and polyglycol diglycidyl ether. Such a reactive diluent is added in an amount of 1 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of the polyester resin.

The present invention is based on the above a), b), c), d),
(E) The adhesive having the composition consisting of the respective components achieves the intended effect. In particular, since the crosslinking and curing reaction occurs between the polyester resin and the epoxy / phenolic resin, heat resistance and solvent resistance are improved. improves. If the composition is out of the above range, the following problems occur. That is, if the amount of the epoxy-phenol resin mixture of the component (b) is less than 20 parts by weight with respect to 100 parts by weight of the polyester resin of the component (a), the solder heat resistance is lowered, and if it exceeds 150 parts by weight, the peel strength is lowered. If the amount of the finely divided inorganic powder as the component (c) is less than 2 parts by weight, the heat resistance to moisture-absorption soldering will decrease, and if it exceeds 20 parts by weight, the peel strength will decrease. If the curing accelerator of component (d) is less than 0.5 parts by weight, the reactivity will decrease and the heat resistance and solvent resistance will deteriorate.
If it exceeds 10 parts by weight, the amount becomes equal to or more than the epoxy group, and the heat resistance is rather deteriorated. (B) Regarding the compounding ratio of the epoxy resin and the phenol resin of the component, epoxy is 10
If the amount is less than 10% by weight and the amount of phenol exceeds 90% by weight, the heat resistance is lowered. If the amount of epoxy is more than 90% by weight and the amount of phenol is less than 10% by weight, flexibility and adhesiveness are deteriorated. If the reactive diluent of the component (e) is less than 1 part by weight, the adhesiveness to the release paper will not be improved, and if it exceeds 10 parts by weight, the solder heat resistance in the normal state and when absorbing moisture will deteriorate.

If necessary, the adhesive may be a halogen-containing organic compound such as tetrabromophthalimide, tetrabromophthalic anhydride or decabromodiphenyl ether, a compound containing phosphorus or a nitrogen atom, or an inorganic compound such as antimony trioxide or aluminum hydroxide. A flame retardant can be added.

The heat-resistant insulating film serving as the base of the coverlay film of the present invention has a thickness of 12.5 to 125 μm.
Examples thereof include a polyimide film, a polyphenylene sulfide film, a polyparabanic acid film, a heat resistant polyester film, a polyethersulfone film, and a polyether / etherketone film. Among them, a polyimide film is preferably used.

The release paper used in the present invention is obtained by laminating a poly-4-methylpentene-1 film (abbreviated as TPX film) on both sides of a base paper. The thickness of the TPX film used here is preferably in the range of 5 to 50 μm and 5 μm.
When it is less than m, the hardness characteristics of the TPX film are not reflected in the release paper, and the release paper exerts a cushion-like action at the time of punching,
Inferior in workability. On the other hand, if the thickness exceeds 50 μm, the release paper becomes too hard, which accelerates the wear of the mold at the time of punching and reduces the number of punches.

The coverlay film of the present invention is obtained by applying a solution of a heat-resistant adhesive having the above composition such as dioxolane, MEK, toluene or benzene in an organic solvent to the heat-resistant insulating film so as to have a dry thickness of 10 to 60 μm. , The solvent is removed to bring the adhesive into a semi-cured state (also referred to as B stage). In this case, heating can be performed at about 100 ° C for a short time if necessary. Next, this heat-resistant insulating film with heat-resistant adhesive of the B stage is overlaid on the above-mentioned release paper, and the temperature is 20 to 100 ° C and the linear pressure is 0.5 to 20 Kg by a roll laminator or the like.
It is manufactured by laminating under the condition of / cm and winding in a roll.

[0016]

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. All parts and percentages in the specific examples are based on the weight of the solid content. (Examples 1 to 6, Comparative Examples 1 and 2) Carboxyl group-containing polyester resins of the grades shown in Table 1 (Examples of grades:
297 [Toyobo Co., Ltd. product name]) 100 parts of bisphenol A
50 parts of Epicoat 828 (trade name of Yuka Shell Epoxy Co., Ltd.), 10 parts of Epicoat 154 (trade name of Yuka Shell Epoxy Co., novolac type epoxy resin), 15 parts of novolac type phenol formaldehyde resin, Table 1,
The type and amount of finely divided inorganic powder (anhydrous silica:
Aerosil R972, 130 [trade name of Nippon Aerosil Co., Ltd.)), reactive diluent (manufactured by Yuka Shell Epoxy Co., Ltd.), and 0.8 parts of 2-ethylmethylimidazole as a curing agent and 4 parts of trimellitic anhydride, 30 parts by weight. % Dioxolane solution and uniformly dispersed by a ball mill to obtain an adhesive solution.

Next, this adhesive solution was applied to a 25 μm-thick polyimide film: Kapton 100H (trade name, manufactured by Toray DuPont Co., Ltd.) so that the coating thickness after drying was 30 μm, and the temperature was 80 ° C. × 2 minutes, 120 ° C. It was dried by heating for 5 minutes, the solvent was removed, and the adhesive was B-staged. Next, this B-stage film and release paper with both-side TPX film attached to the base paper are pressure-laminated by a roll laminator at a temperature of 50 ° C., a linear pressure of roll pressure of 5 kg / cm, and a speed of 2 m / min to produce a coverlay film. The releasability was measured. Next, release the release paper from the coverlay film, and laminate the semi-cured polyimide film with adhesive on the glossy surface of electrolytic copper foil 35μm and press at 160 ℃, 50kg / cm ² for 30 minutes. A flexible laminated film was produced. The characteristics of the flexible laminated film thus obtained are shown in Tables 1 and 2. ．

[0018]

[Table 1]

[0019]

[Table 2]

(Physical property measuring method) The physical property measuring methods of these films shown in Tables 1 and 2 are as follows. 1) Releasability: A sample with a width of 50 mm is 100 mm / mi in the 180 ° direction.
Peel off the polyimide film with adhesive at a speed of n.
The releasability means the adhesive strength between the release paper and the adhesive. 2) Peel strength: Perform according to JIS C6481. A 10 mm wide sample is peeled off the copper foil in the 90 ° direction at a peeling speed of 50 mm / min. 3) Solder heat resistance: After the sample is floated in the solder bath for 30 seconds, the temperature at which blistering does not occur is measured. For moisture-absorbing solder, absorb the sample under the conditions of 40 ° C × 90% RH × 1 hr, and then flow the sample for 30 seconds in the solder bath to check the appearance, blistering, etc.

[0021]

EFFECTS OF THE INVENTION The cover lay film of the present invention does not cause curling due to changes in humidity, has excellent adhesiveness between the adhesive and the release paper on which the TPX film is attached, and has improved mechanical continuous processability such as perforation and cutting. Has been done. Further, since a release treatment with a silicone-based release agent or the like is unnecessary, there is no transfer to the heat-resistant adhesive surface of the B stage, and the adhesive strength of the adhesive with the base material can be maintained. It has features. The present invention makes it possible to provide an excellent protective coverlay film for flexible printed circuits, and its practical utility value is extremely high.

Claims (1)

[Claims] 1. A heat-resistant insulating plastic film having a semi-cured surface coated with an adhesive having the following composition on one surface, and 2) a poly-4-methylpentene-1 film attached to both surfaces of a base paper. A coverlay film made by pressure-bonding laminated release paper. A) Polyester resin having an acid value of 70 to 150: 100 parts by weight, b) Mixture of 10 to 90% by weight of epoxy resin and 90 to 10% by weight of phenolic resin: 20 to 150 parts by weight,
C) Finely divided inorganic powder: 2 to 20 parts by weight, d) Curing accelerator: 0.5 to 10 parts by weight, e) Reactive diluent: 1 to 10 parts by weight.