KR102216722B1 - Adhesive Composition for coverlay film and coverlay film for flexible printedcircuit board comprising the same - Google Patents

Abstract

The present invention relates to an adhesive composition for a coverlay and to a coverlay for a flexible printed circuit board (FPCB) comprising the same. The adhesive composition for a coverlay comprises: an epoxy resin; a rubber resin; a thermoplastic resin; a hardener; inorganic particles; and a flame retardant. In addition, when manufacturing a novel FPCB by a roll lamination method, the flowability can be improved to exhibit an excellent filling rate and have fillability, and the occurrence of a lifting phenomenon is capable of being prevented during drying due to heat.

Description

Adhesive composition for coverlay, and coverlay for FPCB including the same {Adhesive Composition for coverlay film and coverlay film for flexible printed circuit board comprising the same}

The present invention relates to an adhesive composition for a coverlay and a coverlay for an FPCB comprising the same, and more specifically, to an adhesive composition for a coverlay for use in manufacturing an FPCB using a roll lamination method and a coverlay for FPCB comprising the same will be.

With the recent development of electronic component technology, a flexible flat cable (hereinafter, referred to as'FFC') has been used in various fields to reduce the weight and volume of products and free wiring.

FFC is manufactured through a process in which conductors are arranged at regular intervals between the top and bottom of the insulating film and laminated with instantaneous heat and pressure. However, the width and thickness of the applicable conductors are limited, and only straight wires are possible. Due to such a low degree of freedom in circuit design, there is a disadvantage that it is difficult to expand to various application fields.

In order to overcome the limitations of the conventional FFC, recently, a flexible printed circuit board (hereinafter referred to as'FPCB') has been developed. Since it has the flexible characteristics of FFC and forms a circuit pattern through an etching process, it has a higher degree of freedom in circuit design than FFC, and has the advantage of being able to cope with the line width of narrow microcircuits, which is expanding to various application fields.

In general, the coverlay bonded to the FPCB is coated with a semi-cured adhesive layer on the end face of the heat-resistant film, and is composed of a release paper to protect the adhesive. Since these coverlays are bonded to FPCB to protect printed circuits, heat resistance, adhesion, and flame retardancy are important properties required, and all of these properties must be provided at the same time.

In the conventional coverlay temporary folding, in general, the open point is aligned and the temporary welding is performed with an iron. In addition, the laminated subsidiary material 40 is made of Kraft paper, Sus plate, PVC, or the like.

This conventional coverlay bonding method has the following problems. Since manual work is reflected, it is difficult to manufacture FPCBs with a size larger than a certain area. In addition, the process of stacking and removing subsidiary materials takes a lot of time, and thus there is a problem in that work efficiency is deteriorated. In addition, there is a problem in that the cost burden for the provision of a large amount of laminated subsidiary materials increases.

In order to improve this problem, a new FPCB manufacturing method such as a roll lamination method is being developed, but the existing adhesive composition for coverlay is difficult to apply due to a problem of physical properties under the roll lamination method under high temperature and high pressure conditions exposed for a short time. There is.

There is a need to develop an adhesive composition for a coverlay that can improve this problem.

KR 10-2011-0011918 A1

An object of the present invention is to provide an adhesive composition for a coverlay and a coverlay for FPCB comprising the same.

Another object of the present invention is to provide an adhesive composition for a coverlay capable of exhibiting an excellent filling rate by improving flowability when manufacturing a new FPCB by a roll lamination method, and a coverlay for FPCB comprising the same.

Another object of the present invention is to provide an adhesive composition for a coverlay that does not generate a lift phenomenon upon drying by filling and heat, and a coverlay for FPCB comprising the same.

In order to achieve the above object, the adhesive composition for a coverlay according to an embodiment of the present invention is an epoxy resin; Rubber resin; Thermoplastic resin; Hardener; Inorganic particles; And a flame retardant, wherein the inorganic particles are surface-treated in order to improve dispersibility, and are excellent in filling properties and adhesion when bonding the coverlay by a roll lamination method.

The epoxy resin is a bisphenol A resin, a bisphenol F resin, a hydrogenated epoxy resin, a noblock epoxy resin, a biphenyl epoxy resin, a brominated epoxy resin, and a mixture thereof. It may be selected from the group consisting of.

The epoxy resin may further include a phenoxy resin having a weight average molecular weight (Mw) of 10,000 or more.

The rubber resin is nitrile-butadiene rubber, butadiene rubber, styrene-butadiene rubber, hydrogenated nitrile-butadiene rubber, carboxy-terminated liquid It may be selected from the group consisting of butadiene-acrylonitrile rubber (Carboxyl terminated butadiene acrylonitrile) and mixtures thereof.

The thermoplastic resin may be selected from the group consisting of polyester resin, polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, polyvinyl alcohol, acrylic resin, and mixtures thereof.

The thermoplastic resin may be a polyester resin having a glass transition temperature (Tg) of 20 to 100°C.

The adhesive composition for coverlay may further include a modified alicyclic amine (Cycloaliphatic modified amine)-based curing agent as a fast curing agent.

The adhesive composition for the coverlay may further include inorganic particles and a flame retardant.

A coverlay for FPCB according to another embodiment of the present invention includes a coverlay film; And a coverlay adhesive layer including the coverlay adhesive composition, and a coverlay adhesive layer may be formed on one surface of the coverlay film.

The flexible printed circuit board according to another embodiment of the present invention may include the coverlay for FPCB.

Hereinafter, the present invention will be described in more detail.

The adhesive composition for a coverlay according to an embodiment of the present invention is an epoxy resin; Rubber resin; Thermoplastic resin; Hardener; Inorganic particles; And a flame retardant.

When manufacturing the FPCB by the roll lamination method, the adhesive composition for a coverlay of the present invention forms an adhesive layer on one side of the coverlay, thereby securing excellent filling properties and adhesion.

The roll lamination method of the present invention is different from the method for manufacturing the existing FPCB, and the release film, the coverlay and the base constituting the FPCB are manufactured in a roll form, and the cover is passed through a pair of rollers to sequentially contact them. Lay and base are combined.

There is a difference from the conventional FPCB manufacturing method in that it shortens working time and reduces cost by omitting the process of attaching coverlays and laminating subsidiary materials in the conventional FPCB manufacturing process, and can manufacture FPCBs of various sizes that are not restricted by size. do.

In the manufacturing method of the existing FPCB, the process of grounding the coverlay uses the hot press method in the process of temporary bonding and lamination of subsidiary materials. More specifically, a coverlay is attached on the base, subsidiary materials are laid-up, and hot press is performed through a press machine.

At this time, the coverlay is a coverlay film and a coverlay adhesive layer are sequentially stacked. In the conventional coverlay temporary folding, in general, the open point is aligned and the temporary welding is performed with an iron.

This conventional coverlay bonding method has the following problems. Since manual work is reflected, it is difficult to manufacture FPCBs with a size larger than a certain area. In addition, the process of stacking and removing subsidiary materials takes a lot of time, and thus there is a problem in that work efficiency is deteriorated. In addition, there is a problem in that the cost burden for the provision of a large amount of laminated subsidiary materials increases.

In the FPCB manufacturing method using the roll lamination method instead of the coverlay bonding method described above, the release film, the coverlay, and the base are manufactured in a roll form, and the coverlay and the base are laminated by passing through so as to sequentially contact between a pair of rollers. , Compared with the conventional FPCB manufacturing process, it is possible to shorten the working time and reduce the cost by omitting the coverlay temporary bonding and subsidiary material lamination process.

In addition, it is possible to manufacture FPCBs of various sizes that are not restricted by size, and damage to the coverlay in the lamination process can be minimized.

In order to ground the coverlay of FPCB by applying the roll lamination method, when using the same coverlay adhesive layer used in the conventional hot press method, under the conditions of temperature and pressure due to penetration between a pair of rollers, the adhesive layer Resin flowability is poor, and filling problems may occur.

In addition, after roll lamination, even under hot air drying conditions for thermal curing, the hot press adhesive layer has poor flowability of the adhesive layer resin, resulting in a lifting phenomenon.

In the conventional hot press method, as described above, a coverlay is temporarily bonded on a base, subsidiary materials are laid up, and a hot press process is performed through a press machine.

At this time, the hot press process uses a hot press machine to provide continuous temperature and pressure for about 1 hour, so that the adhesive layer of the coverlay has sufficient flowability, so that there is no problem in filling, and temperature and pressure are provided for a long time. As a result, it has sufficient adhesiveness.

That is, in the case of the conventional coverlay adhesive layer used in the hot press process, it is not necessary to have high flowability under the temperature and pressure conditions provided within a short time, and there is no hot air drying process, so the problem of the excitation phenomenon in the hot air drying process Did not occur.

However, in the FPCB manufacturing process, in order to improve the problems of the conventional hot press method, when applying the roll lamination method, for the grounding of the coverlay, it is applied to the roll lamination method rather than the conventional coverlay adhesive composition. There is a need to develop an adhesive composition that can be done.

As described above, in the case of the roll lamination method, the release film, the coverlay, and the base constituting the FPCB are manufactured in a roll form, and the coverlay and the base are laminated by passing through so as to sequentially contact between a pair of rollers.

That is, the release film, the coverlay, and the base necessary for manufacturing the FPCB are stored in a roll form, and the release film, the coverlay, and the base are passed through a pair of rollers to be laminated.

When penetrating between a pair of rollers, instantaneous pressure and heat are provided in the area where the pair of rollers abut, and pressure and heat are provided by the pair of rollers in a very short time compared to the hot press method. Flowability is increased under the pressure and heat conditions provided for a short time, and the etched copper copper foil layer must be filled, and then sufficient adhesiveness must be maintained under hot air drying conditions.

However, in order to apply the roll lamination method, the coverlay is stored in the form of a roll, and is moved while contacting between a pair of rollers.

That is, the coverlay is composed of a coverlay film and a coverlay adhesive layer, and the coverlay is stored while being wound on a winding roller, and is used in the manufacture of an FPCB.

When the coverlay is wound on a winding roller, the coverlay adhesive layer and one side of the coverlay film come into contact with each other, and at this time, adhesion should not occur by the adhesive layer. In addition, the shape of the adhesive layer should be maintained in the room temperature storage state.

More specifically, for the application of the roll lamination method, even if it contacts one side of the coverlay film while it is wound around the take-up roller, it is not adhered and the shape of the adhesive layer can be maintained. However, when passing through a pair of rollers, When the release film is pressed by a roller, the coverlay adhesive layer instantaneously increases the flowability and is filled in the etched copper copper foil layer, and there is no lifting phenomenon due to excellent adhesion even in the subsequent hot air drying process. do.

In the case of the coverlay adhesive layer used in the conventional hot press method, when pressed at 160° C. for 1 hour, it is 60 to 90 μm, whereas the coverlay adhesive layer is formed on one side of the coverlay film with the coverlay adhesive composition of the present invention and the same Under the conditions, when the flowability of the resin is measured, it can be seen that the flowability is higher in the range of 90 to 150 μm.

Thereafter, in the case of the conventional hot press adhesive layer, as a result of checking whether a lifting phenomenon occurred during hot air drying at 120°C for 5 hours, a lifting phenomenon occurred in some cases, and the flowability of the adhesive layer resin was 0 to 20 μm, which was less than 160°C. It can be seen that little flow occurs at temperature.

On the other hand, in the case of the coverlay adhesive layer of the present invention, as a result of confirming whether a lifting phenomenon occurred during hot air drying at 120° C. for 5 hours, a lifting phenomenon did not occur, and the flow of the adhesive layer resin under the same conditions was 40 to 60 μm. As a result, a certain flow property is generated and the adhesive property is increased, so that the lifting phenomenon does not occur during hot air drying.

More specifically, the adhesive composition for a coverlay of the present invention forms an adhesive layer on one side of the coverlay film, exhibits a resin flowability of 90 to 150㎛/hr at 150℃ to 180℃, and 40 to 130℃ at 110 to 130℃. It can exhibit a resin flowability of 60㎛/hr.

When the coverlay adhesive layer is formed by using the coverlay adhesive composition of the present invention, the flowability of the resin is too high under the hot press method, and the adhesive layer may flow down under high temperature and high pressure conditions.

On the other hand, under the roll lamination method, as a pair of rollers are in contact with each other to provide high temperature and high pressure conditions for a short period of time, due to improved flowability, excellent filling properties can be exhibited in the etched copper copper foil layer. After passing through, the flowability of the adhesive layer becomes smaller again, so that the problem of the adhesive layer flowing down can be prevented.

In addition, after the roll lamination method, a slight flow occurs even during hot air drying, and the adhesion of the coverlay is improved due to the flow of the resin, so that the lifting phenomenon by hot air drying does not occur.

More specifically, by the roll lamination method, the pressure and temperature conditions that a pair of rollers are in contact with and transmitted to the coverlay adhesive layer are 0.5 MPa and 120 to 150°C, and the speed at which the rollers rotate is 0.3 to 3.0 m/min. to be.

More specifically, the epoxy resin is a bisphenol A resin, a bisphenol F resin, a hydrogenated epoxy resin, a noblock epoxy resin, a biphenyl epoxy resin, a brominated epoxy resin, and It may be selected from the group consisting of a mixture thereof, and is preferably a bisphenol A type epoxy resin, but is not limited to the above example.

The bisphenol A type epoxy resin is more specifically, an epoxy equivalent (EEW, g/eq) of 184 to 190 bisphenol A type epoxy resin and an epoxy equivalent of 450 to 500 (EEW, g/eq) bisphenol A type epoxy resin. It can be mixed and used. At this time, the mixing molar ratio is a bisphenol A type epoxy resin having an epoxy equivalent (EEW, g/eq) of 184 to 190 and an epoxy equivalent of 450 to 500 (EEW, g/eq) of a bisphenol A type epoxy resin of 1:3 to 1:7. It can be used by mixing in a molar ratio of, preferably 1:5, but is not limited to the above example.

The epoxy resin may further include a phenoxy resin having a weight average molecular weight (Mw) of 10,000 or more.

The phenoxy resin 　 contains an epoxy group at both ends, and the epoxy group participates in curing because the equivalent is very small compared to the molecular weight, but it can impart fluidity at high temperatures.

　Phenoxy resin that can be additionally included in the present invention is a resin that exhibits fluidity while controlling the curing rate, and has a softening point and a glass transition temperature (Tg) in the range of 0℃ to 200℃, and has a weight average molecular weight of 10,000 It is preferably within the range of 1,000,000. When the phenoxy resin has a softening point and a weight average molecular weight within the above range, it maintains a solid state at room temperature to reduce adhesion to the coverlay film during processing, thereby facilitating storage on the take-up roller, and flowability at high temperature. By giving it, the filling property can be improved.

The rubber resin is nitrile-butadiene rubber, butadiene rubber, styrene-butadiene rubber, hydrogenated nitrile-butadiene rubber, carboxy-terminated liquid It may be selected from the group consisting of butadiene-acrylonitrile rubber (Carboxyl terminated butadiene acrylonitrile) and mixtures thereof, and is preferably carboxylated NBR with xNBR, but is not limited to the above examples.

The xNBR has almost the unique characteristics of NBR, and additionally has high tear resistance, abrasion resistance, tensile strength, and modulus.

The thermoplastic resin may be selected from the group consisting of polyester resin, polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, polyvinyl alcohol, acrylic resin, and mixtures thereof, preferably polyester resin, but in the above example Not limited.

Thermoplastic resin is a polymer that melts when heat is applied and returns to a solid state when the temperature is sufficiently lowered. Many thermoplastics are produced by polymer compounds that interact with weak molecular forces. Unlike thermosetting plastics, when heat is applied, they melt and return to their original state, so they can be recycled, and the general molecular structure is a linear structure that allows only weak interactions between molecules.

As the thermoplastic resin of the present invention is included as a component of the adhesive composition for a coverlay, it plays a role in improving the flow characteristics and enhancing the filling properties under instantaneous high temperature and high pressure conditions in the roll lamination method.

As described above, thermoplastic resin refers to a polymer resin that can be melted and recycled when heat is applied, and due to this characteristic, its shape is easily deformed by heat.

The thermoplastic resin in the present invention is included in the adhesive composition, increases flowability by instantaneous heat and pressure, and increases the filling property of the etched copper copper foil due to this flowability.

That is, in the case of an adhesive composition that does not contain a thermoplastic resin, when the roll lamination method is applied, the flowability under instantaneous high temperature and high pressure conditions is not improved, and thus an unfilled problem that is not sufficiently filled in the etched copper copper foil may occur.

On the other hand, since the adhesive composition for a coverlay of the present invention contains a thermoplastic resin, an adhesive layer is formed on one side of the coverlay film, and when laminated by a roll lamination method, a pair of rollers come into contact with high temperature conditions. When pressurized under the pressure, as described above, the resin flowability of the adhesive layer is increased, the filling property is increased, and the problem of unfilling does not occur.

Preferably, the thermoplastic resin is a polyester resin having a glass transition temperature (Tg) of 20 to 100°C, but is not limited to the above example, and when used in the adhesive composition for a coverlay of the present invention, flowability due to instantaneous heat and pressure If it can be improved, all can be used without limitation.

The adhesive composition for coverlay may further include a modified alicyclic amine (Cycloaliphatic modified amine)-based curing agent as a fast curing agent.

The adhesive composition for a coverlay of the present invention may include a curing agent, and may further include the fast curing agent.

The curing agent may be selected from the group consisting of an amine-based curing agent, a phenol-based curing agent, an imidazole-based curing agent, and a mixture thereof.

As the curing agent used in the epoxy resin composition, any compound having an active group capable of reacting with an epoxy group can be used. For example, aliphatic amines such as ethylenediamine, ethylene triamine, triethylenetetramine, hexamethylenediamine, m-xylene diamine as amine-based curing agents, metaphenylenediamine, diaminodiphenylmethane, diamino diethyl diphenyl Aromatic amines such as methane and diamino diethyl diphenyl sulfone, tertiary amines such as benzyl dimethyl amine, tetramethyl guanidine, 2,4,6-tris (dimethylamino methyl) phenol, adipic acid dihydra And imidazoles such as organic acid dihydrazide such as zide, 2-methylimidazole, 2-ethyl-4-methylimidazole, and the like. Non-limiting examples of the phenolic curing agent include phenol novolac, cresol novolak, bisphenol A novolac, naphthalene type, and the like, which may be used alone or in combination of two or more. In the present invention, since it is cured at a relatively low temperature and has good storage stability, any curing agent can be used without limitation. Preferably, the curing agent may be used by mixing 3,3'-diaminodiphenylsulfone and 2-undecylimidazole, but is not limited to the above examples.

The main feature of the present invention is to use a fast curing agent, rather than using a passing agent alone.

The coverlay adhesive composition used in the hot press method does not cause problems due to sufficient curing even if only a curing agent is used, but in the case of the roll lamination method, some curing occurs when passing through a pair of rollers, followed by hot air drying. It is characterized in that it further includes an inner curing agent to enable rapid curing so as not to cause a lifting phenomenon in the process (baking process).

However, when the fast curing agent of the present invention is used within the range to be described later, some curing occurs in the roll lamination process, and then rapid curing in the hot air drying process can be promoted to prevent lift-off.If it is less than the range value, hot air A lifting phenomenon may occur during the drying process, and if the content exceeds the range value, curing may proceed before sufficient filling occurs during the roll lamination process, resulting in a problem of unfilling.

The fast curing agent is a modified alicyclic amine (Cycloaliphatic modified amine)-based curing agent.

The adhesive composition for the coverlay may further include inorganic particles and a flame retardant.

The inorganic particles may be selected from the group consisting of titanium dioxide, talc, aluminum hydroxide trihydroxide, alumina, magnesium hydroxide, and mixtures thereof, preferably aluminum hydroxide and titanium dioxide, but are not limited to the above examples. Does not.

The inorganic particles may include surface-treated inorganic particles to improve dispersibility in the coverlay adhesive composition.

Inorganic particles generally have poor dispersibility in the polymer resin, and thus dispersibility is improved by further including a dispersant.

When the dispersibility is low, when the adhesive layer is formed using the adhesive composition, it is not uniformly distributed, and there is a problem in that it does not exhibit uniform characteristics of mechanical properties and heat resistance according to the use of inorganic particles.

However, when the dispersibility is improved in the form of a dispersion, a problem of deteriorating the adhesive properties may occur due to a solvent used for preparing the dispersion.

Therefore, it is most preferable to improve the dispersibility through surface treatment of the inorganic particles.

Accordingly, in the present invention, in order to improve dispersibility, it is intended to improve dispersibility through surface treatment of titanium dioxide.

The titanium dioxide is surface-treated so that silicon is bonded to the surface.

More specifically, titanium dioxide and tetramethyl orthosilicate (TMOS) are added to alcohol, ammonia is added as a catalyst, and heated at 25 to 60° C. to prepare a surface-treated titanium dioxide.

The flame retardant is selected from the group consisting of a phosphorus-based flame retardant, a nitrogen-based flame retardant, an inorganic flame retardant and a mixture thereof, and a phosphorus-based flame retardant, preferably, a particulate phosphorus-based flame retardant and a resin-type phosphorus-based flame retardant are used.

In particular, the resin-type phosphorus-based flame retardant is a flowable flame retardant and is used to impart flame retardancy to the adhesive layer.When a simple phosphorus-based flame retardant, nitrogen-based flame retardant, and inorganic flame retardant are used, when applied to the roll lamination method, flowability is Since the improved effect can be reduced by the flame retardant, a flame retardant with flowability is used.

The inorganic particles and flame retardants are included for lead heat resistance more specifically. More specifically, recently, SMT (Surface mounted technology) method is used to increase the floor area ratio of chips according to the miniaturization of electric/electronic equipment. In this process, molten lead is reflowed, but this technique cannot be applied unless the heat deflection temperature (HDT) is about 260℃.

That is, lead is mounted on the FPCB manufactured by laminating the coverlay to the base by applying the roll lamination method, and at this time, the SMT method is used. In order to apply this process, the adhesive layer must maintain high heat resistance, and if the heat resistance cannot be maintained, the mechanical properties may be rapidly deteriorated and lead may be lifted during printing.

In order to improve this problem, the present invention is characterized in that it further comprises inorganic particles and a flame retardant.

As described above, the inorganic particles may include aluminum hydroxide and titanium dioxide, and the flame retardant includes a phosphorus-based flame retardant, a particulate phosphorus-based flame retardant and a resin-type phosphorus-based flame retardant to increase lead heat resistance, and after evaluation in the reflow process This can be prevented from occurring.

The adhesive composition for a coverlay of the present invention is an epoxy resin; Rubber resin; Thermoplastic resin; Hardener; Inorganic particles; And containing a flame retardant, based on 100 parts by weight of the epoxy resin, 50 to 80 parts by weight of a rubber resin; 3 to 10 parts by weight of a thermoplastic resin; 8 to 15 parts by weight of a curing agent; 30 to 60 parts by weight of inorganic particles; And 50 to 80 parts by weight of a flame retardant.

The adhesive composition may further include an inner curing agent, and in this case, it may be included in an amount of 0.01 to 0.1 parts by weight based on 100 parts by weight of the epoxy resin.

Epoxy resin when prepared as an adhesive using the adhesive composition; Rubber resin; Thermoplastic resin; Hardener; It can be prepared by mixing inorganic particles and flame retardants with a solvent, and the solvent is selected from the group consisting of methyl ethyl ketone (MEK), toluene, and mixtures thereof, and preferably a mixed solvent of methyl ethyl ketone and toluene can be used. .

Preferably, the adhesive composition for the coverlay is based on 100 parts by weight of the epoxy resin, 50 to 80 parts by weight of a rubber resin; 3 to 10 parts by weight of a thermoplastic resin; 8 to 15 parts by weight of a curing agent; 30 to 60 parts by weight of inorganic particles; 50 to 80 parts by weight of a flame retardant; It may contain 0.01 to 0.1 parts by weight of the fast curing agent and 500 to 600 parts by weight of the solvent.

The epoxy resin is a bisphenol A type epoxy resin having an epoxy equivalent (EEW, g/eq) of 184 to 190 and an epoxy equivalent of 450 to 500 (EEW, g/eq) of a bisphenol A type epoxy resin of 1:3 to 1:7. It can be used by mixing in a molar ratio of, preferably 1:5, but is not limited to the above example. When mixed within the above range, it moves between a pair of rollers, and flowability increases under conditions of instantaneous high-temperature and high-pressure provision to improve the filling of FPCB, and also at room temperature when an adhesive layer is formed on one side of the coverlay film. It is easily cured to facilitate formation into an adhesive layer.

The phenoxy resin may be additionally included in the epoxy resin, and may be included in an amount of 80 to 100 parts by weight based on 100 parts by weight of the epoxy resin, and it is possible to exhibit fluidity while controlling the curing rate within the above range value. By maintaining the process, it is possible to reduce the adhesion to the coverlay film during the process, thereby facilitating storage in the take-up roller, and improving the filling property by imparting flowability at high temperature.

Although a small amount of the thermoplastic resin is included, when used within the above range, flowability is increased by instantaneous heat and pressure, and due to this flowability, the filling property of the etched copper copper foil can be improved.

The inner curing agent is also included in a small amount like a thermoplastic resin, but when used within the above range, the filling property is increased by causing some curing in the roll lamination process, and then rapid curing in the hot air drying process can be promoted to prevent the lifting phenomenon. have. If the value is less than the above range, a lifting phenomenon may occur during the hot air drying process, and if the value exceeds the range, curing proceeds before sufficient filling occurs during the roll lamination process, resulting in a problem of unfilling.

When the inorganic particles and the flame retardant are included within the above range, lead heat resistance may be increased, and a lifting phenomenon after evaluation in a reflow process may be prevented.

A coverlay for an FPCB according to another embodiment of the present invention includes a coverlay film and a coverlay adhesive layer including the coverlay adhesive composition, and a coverlay adhesive layer is formed on one surface of the coverlay film.

A flexible printed circuit board (FPCB) according to another exemplary embodiment of the present invention includes the coverlay for FPCB, and is manufactured by a roll lamination method.

According to the adhesive composition for a coverlay of the present invention and a coverlay for an FPCB including the same, when a new FPCB is manufactured by a roll lamination method, it is possible to improve flowability and exhibit an excellent filling rate.

In addition, it is possible to prevent the occurrence of excitation during filling and drying by heat.

1 is a result of measuring the storage elasticity (Strage modulus) of the coverlay adhesive layer according to an embodiment of the present invention.
FIG. 2 is a photograph of a result of not filling a coverlay adhesive layer on an etched copper copper foil when a coverlay is laminated when manufacturing an FPCB according to an embodiment of the present invention.
3 is a photograph of a result of filling an etched copper copper foil with a coverlay adhesive layer when the coverlay is laminated when manufacturing an FPCB according to an embodiment of the present invention.
4 is a reflow temperature condition table according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[Production Example: Preparation of adhesive composition for coverlay]

It was mixed according to the composition ratio of Table 1 to prepare an adhesive composition for a coverlay. An adhesive composition was prepared by mixing an epoxy resin, a phenoxy resin, a rubber resin, a thermoplastic resin, a curing agent, a fast curing agent, an inorganic particle and a flame retardant in a solvent.

HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 Epoxy 100 100 100 100 100 100 100 100 100 100 100 100 100 100 Phenoxy - - - 90 - - - - - - - - - - Rubber resin 50 60 80 60 60 60 60 60 40 90 60 60 60 60 Thermoplastic resin 3 5 10 5 5 5 One 15 5 5 5 5 5 5 Hardener 8 12 15 12 12 12 12 12 12 12 12 12 12 12 Fast curing agent 0.01 0.05 0.1 0.05 - 0.15 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Inorganic particles 30 45 60 45 45 45 45 45 45 45 20 70 45 45 Flame retardant 50 65 80 65 65 65 65 65 65 65 65 65 40 90 solvent 500 500 500 500 500 500 500 500 500 500 500 500 500 500

(Unit weight part) where,

The epoxy resin is a mixture of a bisphenol A type epoxy resin having an epoxy equivalent (EEW, g/eq) of 184 to 190 and a bisphenol A type epoxy resin having an epoxy equivalent of 450 to 500 (EEW, g/eq), and a molar ratio of 1:5 It is an epoxy resin mixed with,

Phenoxy resin has a weight average molecular weight (Mw) of 10,000 or more,

The rubber resin is xNBR,

The thermoplastic resin is a polyester resin with a glass transition temperature (Tg) of 20 to 100°C,

The curing agent is a mixture of 3,3'-diaminodiphenylsulfone and 2-undecylimidazole, and 3,3'-diaminodiphenylsulfone and 2-undecylimidazole are 1 : It is mixed at a weight ratio of 0.5,

The inner curing agent is a modified alicyclic amine (Cycloaliphatic modified amine) type curing agent,

The inorganic particles are a mixture of aluminum hydroxide and titanium dioxide, and are a mixture of aluminum hydroxide and titanium dioxide in a weight ratio of 3:1,

The titanium dioxide is titanium dioxide, which is surface-treated by adding titanium dioxide, tetramethylorthosilicate (TMOS) and ammonia to alcohol and heating at 25 to 60°C, and titanium dioxide and TMOS are included in a weight ratio of 1:3, Ammonia was mixed in 5 parts by weight based on 100 parts by weight of alcohol.

The flame retardant is a particulate phosphorus-based flame retardant and a resin-type phosphorus-based flame retardant, and is a mixture of the particulate phosphorus-based flame retardant and a resinous phosphorus-based flame retardant in a weight ratio of 1:3.

[Experimental Example 1: Preparation of Coverlay]

A polyimide film (PI) was used as a coverlay film, and an adhesive layer was formed on one side of the polyimide film using the adhesive composition for a coverlay of Preparation Example.

The adhesive layer may be formed on one surface of the polyimide film using a known method.

[Experimental Example 2: Storage elasticity measurement result]

The storage modulus (Pa) of the coverlay formed with the adhesive layer using the adhesive compositions of HL2, HL5, HL7, HL9 and HL11 was measured.

The storage modulus was measured using TA's Dynamic Mechanical Analyzer (DMA) Q800. Each coverlay was cut to be 5 mm in width and 50 mm in length in the mechanical direction (MD) and the width direction (TD), and then mounted on a dynamic mechanical analyzer so that the actual measurement length was about 20 mm. Then, after raising the temperature at a rate of 10 °C/min from 20 °C to 200 °C under the following conditions, the storage modulus value was measured.

The results are shown in FIG. 1.

Referring to FIG. 1, it can be seen that HL2 is formed at the lowest temperature based on the lowest storage elasticity value compared to HL5, HL7, HL9, and HL11, and has the lowest storage elasticity value.

[Experimental Example 3: Filling Test Results]

After the coverlay prepared in Experimental Example 1 was bonded to the base using a roll lamination method, the degree of filling was checked.

More specifically, a pair of rollers was used to simultaneously pass the wound base, the coverlay and the release film, bonded to each other, and then subjected to a hot air drying (baking) process at 120° C. for 5 hours.

At this time, the filling property was evaluated after the roll lamination method was performed, and whether or not a lifting phenomenon occurred after the hot air process was confirmed.

As shown in FIG. 2, when unfilling occurred, it was marked as X, and as shown in FIG. 3, it was evaluated as O.

HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 Fillability Roll lamination O O O O O X X O O X O O O O hot air dry O O O O X X X O O X O O O O

According to the above experimental results, it can be confirmed that unfilling is affected depending on whether the inner curing agent is included. When the inner curing agent was not included, the problem of unfilling did not occur under the roll lamination process, but a lifting phenomenon occurred in the hot air drying process step.

In addition, when the thermoplastic resin is included in the content range, it was confirmed that unfilling and lifting phenomena appear simultaneously in the roll lamination process and the hot air drying process. On the other hand, it was confirmed that the unfilled and lifted phenomena were not a problem when included in excess.

Judging from the above experimental results, it was confirmed that when the thermoplastic resin was included in the minimum range or more, it was possible to prevent the occurrence of the unfilling problem in the roll lamination process step and the lifting phenomenon in the hot air drying process.

In addition to that, it was confirmed that unfilling and lifting phenomena did not occur in other adhesive layers.

[Experimental Example 4: Lead heat resistance test result]

For the evaluation of the reflow process, the lead bath evaluation was performed. The solder bath temperature condition was floating at 280°C for 30 seconds, and after the evaluation, it was confirmed that the occurrence of a lifting phenomenon occurred.

The reflow temperature condition table is shown in FIG. 4, and the experimental results are shown in Table 3 below.

HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 Lead heat resistance O O O O O O O X X O X X X X

According to the experimental results, it was confirmed that the lifting phenomenon occurred in HL8, HL9, and HL11 to HL14. In the other adhesive layers, it was confirmed that the lifting phenomenon did not occur, and the lead heat resistance was excellent.

[Experimental Example 5: Evaluation of physical properties]

The adhesion and flame retardancy of the prepared coverlay adhesive layer were evaluated. The adhesion was measured by applying the JIS K 6850 test method. Flame retardancy was measured according to UL94 flame retardant regulations. The experimental results are shown in Table 4 below.

HL1 HL2 HL3 HL4 HL5 HL6 HL7 HL8 HL9 HL10 HL11 HL12 HL13 HL14 Adhesion (kgf/cm) 0.98 1.05 1.02 1.03 0.90 0.89 1.01 1.00 0.67 1.01 0.79 0.75 0.65 0.64 Flame retardant O O O O O O O O O O O O O O

According to the experimental results, it was confirmed that the flame retardancy in all adhesive layers exhibited a flame retardancy of V0 grade. On the other hand, in the case of adhesion, it was confirmed that HL9 containing a small amount of rubber resin, and HL11 to HL14 that did not contain inorganic particles and flame retardants as values within the range showed low adhesion.

[Experimental Example 6: Evaluation of flowability of adhesive layer]

In order to evaluate the flowability of the adhesive layer of the present invention, a specimen was prepared using a hot press.

Between the hot press upper plate and the lower plate, an aluminum plate; TPX film; Coverlay; TPX film; PVC film; Kraft paper and aluminum plate were sequentially stacked and pressed at 160° C. for 1 hour at a pressure of 45 kgf/cm ² .

Resin flowability was measured using a Visual Microscops system. The adhesive layer of the coverlay was formed to have a thickness of 38 μm to conduct an experiment, and the experimental result was an average value of five samples measured in μm units.

As a comparative example, a conventional hot press coverlay adhesive composition was used. More specifically, in the same content range as HL2, the fast curing agent is not included, only aluminum hydroxide is included as inorganic particles, and only the particulate phosphorus-based flame retardant is mixed as the flame retardant.

Resin flow measurement by hot pressing Resin flow measurement by heat curing after roll lamination Comparative example 60 to 90 μm 0 to 20 μm HL2 90 to 150 μm 40 to 60 μm

According to the above experimental results, HL2, which is an embodiment of the present invention, has high flowability in the hot press process and is difficult to apply to the hot press process.However, when applying the roll lamination process, there is no problem in the filling property with proper flowability, but general In the case of compounding, the flowability is suitable during the hot press process, so that there is no problem in the filling property, but when the roll lamination process is applied, the resin hardly flows, and a problem of unfilling may occur.

In addition, after the roll lamination process, in the case of the adhesive layer of the general formulation during thermal curing, a lifting phenomenon occurs because there is little flowability, but in the case of HL2 of the present invention, it was confirmed that the lifting phenomenon does not occur due to flowability.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

Claims (10)

Epoxy resin;
Rubber resin;
Thermoplastic resin;
Hardener;
Inorganic particles; And
Contains flame retardants,
The inorganic particles are titanium dioxide and are surface-treated with tetramethylorthosilicate (TMOS) to improve dispersibility,
It further includes a modified alicyclic amine curing agent as a fast curing agent,
When applied to the roll lamination method for manufacturing FPCB, the pattern filling property of the coverlay adhesive layer is excellent.
Adhesive composition for coverlay. The method of claim 1,
The epoxy resin is a bisphenol A resin, a bisphenol F resin, a hydrogenated epoxy resin, a noblock epoxy resin, a biphenyl epoxy resin, a brominated epoxy resin, and a mixture thereof. Selected from the group consisting of
Adhesive composition for coverlay. The method of claim 1,
The epoxy resin further comprises a phenoxy resin having a weight average molecular weight (Mw) of 10,000 or more.
Adhesive composition for coverlay. The method of claim 1,
The rubber resin is nitrile-butadiene rubber, butadiene rubber, styrene-butadiene rubber, hydrogenated nitrile-butadiene rubber, carboxy-terminated liquid Selected from the group consisting of butadiene-acrylonitrile rubber (Carboxyl terminated butadiene acrylonitrile) and mixtures thereof
Adhesive composition for coverlay. The method of claim 1,
The thermoplastic resin is selected from the group consisting of polyester resin, polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, polyvinyl alcohol, acrylic resin, and mixtures thereof.
Adhesive composition for coverlay. The method of claim 5,
The thermoplastic resin is a polyester resin having a glass transition temperature (Tg) of 20 to 100°C.
Adhesive composition for coverlay. delete The method of claim 1,
The coverlay adhesive composition further comprises inorganic particles and a flame retardant
Adhesive composition for coverlay. Coverlay film; And
It comprises a coverlay adhesive layer comprising the adhesive composition for a coverlay according to claim 1,
A coverlay adhesive layer is formed on one side of the coverlay film
Coverlay for FPCB. Including the FPCB coverlay according to claim 9
Flexible printed circuit board.

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