TWI490266B - A resin composition for forming a bonding layer of a multilayer flexible printed circuit board, a resin varnish, a porous flexible printed circuit board, and a multilayer flexible printed circuit board - Google Patents

Description

A resin composition for forming a bonding layer of a multilayer flexible printed circuit board, a resin varnish, a resin copper foil, a method for producing a resin copper foil for manufacturing a multilayer flexible printed circuit board, and a multilayer flexible printed circuit board

The present invention relates to a resin composition for forming a bonding layer of a multilayer flexible printed circuit board, a resin copper foil for forming a resin layer using the resin varnish, a method for producing the resin copper foil, and a multilayer flexible printed circuit board.

The printed circuit board used in the electronic signal supply of electronic equipment uses a flexible printed circuit board with a bend. The flexible wiring board disclosed in Patent Document 1 (Japanese Laid-Open Patent Publication No. Hei. No. 2006-70176) has a layer of an adhesive layer I, a conductor layer on which a circuit pattern has been formed, and an adhesive layer. The structure of the layer II and the cover film, and in the flexible wiring board, the adhesive composition is used for the purpose of obtaining a sufficient flex life even when used at a high temperature.

Accordingly, the flexible printed circuit board is characterized by the characteristics of the product having the bending property, and the flex resistance is important. In addition, in the manufacture of the flexible printed circuit board, in the reflow step or the like, since there is a heat load, it is required that the folding resistance does not deteriorate even when used at a high temperature. Therefore, even if the adhesive used for the flexible printed circuit board is expected, the folding resistance and heat resistance are expected.

In addition, the demand for miniaturization and high-performance of electronic equipment has been increasing, and in order to make the flexible printed circuit board smaller in size, it has been reviewed for miniaturization and multi-layering. However, in order to achieve multilayering of flexible printed circuit boards, adhesives for flexible printed circuit boards are required to have characteristics superior to those of conventional ones. For example, in order to achieve multilayering of a flexible printed circuit board, it is desired to achieve heat resistance and folding resistance in the case where the adhesive layer is thinned. Moreover, when the flexible printed circuit board is multi-layered, it is necessary to improve the precision of interlayer coupling.

In view of the high-density mounting of such a flexible printed circuit board, it is disclosed in Patent Document 2 (Japanese Patent Application Laid-Open No. Hei No. 2005-248134) that it is resistant to flame retardancy, flexing resistance, and environmental protection. A non-halogenated resin composition.

The resin compositions disclosed in Patent Document 1 and Patent Document 2 are all inorganic fillers (inorganic fillers) for improving heat resistance, elastic modulus, flame retardancy, and the like. Thus, when an adhesive which is a multilayer flexible printed circuit board is used, there is a limit in flexibility and thinning of the adhesive layer. Further, in the multilayer flexible printed wiring board, when the via hole for interlayer coupling is formed, if the inorganic filler is contained, the laser workability is lowered, and the formation accuracy of the via hole is lowered. Further, since the B-stage adhesive layer is subjected to the puncture processing, the powder falling and cracking of the adhesive layer are liable to occur. As a result, the powder of the adhesive layer adheres to the conductor layer, resulting in a decrease in coupling reliability. Further, if the adhesive layer is cracked, the insulation performance is lowered.

In addition, when the adhesive composition disclosed in Patent Document 1 is verified, when the molding is performed by lamination processing or press-bonding processing or the like, the inner layer circuit transfer, the outermost layer curl, the void, and the like are likely to occur. If the inner layer circuit is transferred, the outermost wave is curled, which causes an obstacle to the application of the photoresist and the circuit formation step. Further, when voids occur, there is a problem in that foaming is likely to occur by heat treatment such as a reflow step.

Here, the object of the present invention is to provide a so-called B-stage crack, which can prevent the powder falling during the manufacturing process of the flexible printed circuit board, and the related folding resistance, heat resistance, and resin flow. A resin composition for forming a bonding layer of a multilayer flexible printed circuit board having a suitable balance, a resin varnish, a resin copper foil, a method for producing the resin copper foil, and a multilayer flexible method A printed circuit board.

As a result of intensive studies, the inventors of the present invention have achieved the above problems by using the following resin composition.

The resin composition for forming a bonding layer of the multilayer flexible printed wiring board according to the present invention is a resin composition used for forming a bonding layer, which is formed by multilayering an inner flexible printed circuit board. It is characterized in that the resin composition contains the following components A to E:

A component: a solid high heat resistant epoxy resin having a softening point of 50 ° C or higher (except for biphenyl type epoxy resin);

Component B: an epoxy resin curing agent comprising one or more of a biphenyl type phenol resin and a phenol aralkyl type phenol resin;

Component C: a rubber-modified polyamidoximine resin which is soluble in a solvent having a boiling point of from 50 ° C to 200 ° C;

Component D: organic phosphorus-containing flame retardant;

Component E: Biphenyl type epoxy resin.

The resin varnish of the present invention is characterized in that a solvent is added to the resin composition to prepare a resin varnish in a range of 30% by weight to 70% by weight of the resin solid content, and when a semi-hardened resin layer is formed, according to MIL specifications MIL-P-13949G, when measured according to the resin thickness of 55 μm, the resin flow range is 0% to 10%.

The resin copper foil having a resin copper foil on the surface of the copper foil according to the present invention is characterized in that the resin layer is formed by using a resin composition for forming a bonding layer of the multilayer flexible printed wiring board. .

A method for producing a resin copper foil for producing a multilayer flexible printed circuit board according to the present invention is a method for producing a resin copper foil for manufacturing the multilayer flexible printed circuit board, which is characterized in that: In the order of step b, the resin varnish used in the formation of the resin layer is prepared, and the resin varnish is applied onto the surface of the copper foil, and dried to form a semi-hardened resin layer having a thickness of 10 μm to 80 μm to form a resin copper foil. .

Step a: When the weight of the resin composition is 100 parts by weight, the component A is 3 parts by weight to 30 parts by weight, the B component is 13 parts by weight to 35 parts by weight, and the C component is 10 parts by weight to 50 parts by weight. The D component is in a range of 3 parts by weight to 16 parts by weight, and the E component is in a range of 5 parts by weight to 35 parts by weight, and a resin composition of each component is contained.

Step b: The resin composition is dissolved using an organic solvent to form a resin varnish having a resin solid content of 30% by weight to 70% by weight.

The multilayer flexible printed circuit board of the present invention is characterized in that it is obtained by using a resin composition for forming a bonding layer of a multilayer flexible printed circuit board.

Effect of the invention

The resin composition of the present invention can prevent a decrease in folding endurance due to thermal deterioration and can improve the cracking at the B-stage. Further, when the resin composition of the present invention is used, the resin copper foil is obtained. When the constituent material of the flexible printed wiring board is used, since the inorganic filler is not required, the flexibility is excellent and the precision can be accurately performed. Laser processing and puncture processing, and can prevent powder and cracking. Further, the resin copper foil of the present invention is suitable for the formation of via holes in a multilayer flexible printed circuit board because it does not contain an inorganic filler, and the reliability of interlayer coupling can be improved.

Hereinafter, preferred embodiments of the present invention will be described.

Resin composition: The resin composition of the present invention is used to form a bonding layer which is formed by multilayering an inner layer flexible printed wiring board. Further, it is characterized by containing each component such as the following components A to E.

Component A: Solid high heat resistant epoxy resin with a softening point of 50 ° C or higher (except for biphenyl type epoxy resin).

Component B: an epoxy resin curing agent comprising one or more of a biphenyl type phenol resin and a phenol aralkyl type phenol resin.

Component C: A rubber-modified polyamidoximine resin which is soluble in a solvent having a boiling point of from 50 ° C to 200 ° C.

Component D: Organic phosphorus-containing flame retardant.

Component E: Biphenyl type epoxy resin.

The component A is a solid high heat-resistant epoxy resin having a softening point of 50 ° C or more. The component A is an epoxy resin having a high glass transition temperature Tg. In the epoxy resin, a solid heat-resistant epoxy resin having a softening point of 50 ° C or more is used, and the glass transition temperature Tg is high, and a high heat resistance can be obtained by adding a small amount.

Here, the "solid high heat resistant epoxy resin having a softening point of 50 ° C or higher" is preferably one of a cresol novolac type epoxy resin, a phenol novolak type epoxy resin, and a naphthalene type epoxy resin. 2 or more types.

Further, in the component A, in addition to the solid high heat resistant epoxy resin having a softening point of 50 ° C or higher, the phenolic epoxy resin, the cresol novolac epoxy resin, and the phenol novolac type may be further contained. A high heat resistant epoxy resin composed of one or more of an epoxy resin and a naphthalene epoxy resin. In this case, the component A further contains one or two of a novolac type epoxy resin, a cresol novolac type epoxy resin, a phenol novolac type epoxy resin, and a naphthalene type epoxy resin which are liquid at room temperature. The high heat-resistant epoxy resin composed above can further increase the glass transition temperature Tg and further improve the effect of improving the B-stage crack.

On the other hand, when the resin composition is 100 parts by weight, the component A is preferably used in an amount of from 3 parts by weight to 30 parts by weight. When the component A is less than 3 parts by weight, it is difficult to achieve high Tg of the resin composition. On the other hand, when the A component exceeds 30 parts by weight, since the hardened resin layer becomes brittle, the flexibility is completely damaged, and thus it is not suitable for use in a flexible printed circuit board. More preferably, the component A is used in an amount of from 10 parts by weight to 25 parts by weight, and the high Tg of the resin composition and the resin layer after curing can be stably obtained.

The component B is an epoxy resin curing agent comprising one or more of a biphenyl type phenol resin and a phenol aralkyl type phenol resin. The amount of the epoxy resin hardener to be added is derived from the reaction equivalent of the cured resin, and it is not necessary to limit the amount. However, in the case of the resin composition of the present invention, when the resin composition is 100 parts by weight, the component B is preferably used in an amount of from 13 parts by weight to 35 parts by weight. When the component B is less than 13 parts by weight, considering the resin composition of the present invention, a sufficient hardened state cannot be obtained, and the flexibility of the cured resin layer cannot be obtained. On the other hand, when the amount of the component B exceeds 35 parts by weight, the moisture-absorbing property of the cured resin layer tends to be deteriorated, so that it is preferably avoided.

A specific example of a biphenyl type phenol resin is shown in Formula 1:

[Chemical 1]

Further, a specific example of the phenol aralkyl type phenol resin is shown in Chemical Formula 2:

[Chemical 2]

The component C is a rubber-modified polyamidoximine resin which is soluble in a solvent having a boiling point of from 50 ° C to 200 ° C. By blending the component C, the flexibility can be improved, and the effect of suppressing the flow of the resin can be obtained. The rubber-modified polyamidoximine resin is obtained by reacting a polyamide amine imide resin with a rubber resin, and is carried out for the purpose of improving the flexibility of the polyamide amine imide resin itself. In other words, a part of the acid component (cyclohexanedicarboxylic acid, etc.) of the polyamidoximine resin is replaced with a rubber component by reacting the polyamide amide imine resin with a rubber resin. The rubber component covers the concept of natural rubber and synthetic rubber. The latter synthetic rubber is such as: styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber, acrylonitrile-butadiene rubber, etc. . Further, it is also useful to use a heat-resistant synthetic rubber such as a nitrile rubber, a chloroprene rubber, a ruthenium rubber or a urethane rubber from the viewpoint of ensuring heat resistance. The rubber-based resin is a copolymer which can be reacted with a polyamidoximine resin to produce a copolymer, and it is preferred to have various functional groups at both ends. In particular, it is useful to use a CTBN (carboxy terminal butadiene nitrile rubber) having a carboxyl group. In addition, the rubber component may be copolymerized in only one type or may be copolymerized in two or more types. Further, when a rubber component is used, it is preferred to use a rubber having a number average molecular weight of 1,000 or more from the viewpoint of flexibility.

When the rubber modified polyamidoximine resin is polymerized, the solvent used in the dissolution of the polyamide amidoximine resin and the rubber resin is preferably used such as dimethylformamide or dimethyl group. Ethylamine, N-methyl-2-pyrrolidone, dimethyl hydrazine, nitromethane, nitroethane, tetrahydrofuran, cyclohexanone, methyl ethyl ketone, acetonitrile, γ-butyrolactone, or the like the above. Further, when the polymerization reaction is caused, it is preferred to use a polymerization temperature in the range of 80 ° C to 200 ° C. In the case of such polymerization, when a solvent having a boiling point of more than 200 ° C is used, it is preferred to replace the solvent with a solvent having a boiling point of from 50 ° C to 200 ° C for subsequent compounding purposes.

Here, the solvent having a boiling point in the range of 50 ° C to 200 ° C is, for example, a single solvent or a mixed solvent of two or more selected from the group consisting of methyl ethyl ketone, dimethyl acetamide, and dimethylformamide. . When the boiling point is less than 50 ° C, the solvent diffusion due to heating tends to be conspicuous, and when the semi-hardened resin is formed from the resin paint state, a good semi-hardened state is not easily obtained. On the other hand, when the boiling point exceeds 200 ° C, when a semi-hardened resin is formed from a resin varnish state, since the solvent is not easily dried, it is difficult to obtain a good semi-hardened resin layer.

In the rubber-modified polyamidoximine resin used in the resin composition of the present invention, when the weight of the rubber-modified polyamidoximine resin is 100% by weight, the copolymerization amount of the rubber component is preferably Up to 0.8% by weight or more. When the amount of the copolymerization is less than 0.8% by weight, even if a rubber-modified polyamidoximine resin is formed, the resin layer formed by using the resin composition of the present invention is hardened after being cured, and is in contact with copper. The adhesion between the foils is also reduced and is therefore best avoided. Moreover, it is more preferable that the copolymerization amount of the rubber component is 3% by weight or more, and particularly preferably 5% by weight or more. Empirically, even if the amount of copolymerization exceeds 40% by weight, no particular problem occurs. However, since the effect of improving the flexibility of the resin layer after the hardening has reached saturation, it is considered to be a waste of resources, so it is preferable to avoid it.

The rubber modified polyamidoximine resin described above is required to be soluble in a solvent. The reason is that if it is not soluble in a solvent, it is difficult to prepare when forming a resin varnish. Moreover, the rubber-modified polyamidoximine resin is used in an amount of from 10 parts by weight to 50 parts by weight based on 100 parts by weight of the resin composition. When the rubber-modified polyamidoximine resin is less than 10 parts by weight, the effect of suppressing the flow of the resin is not easily exhibited. Further, the hardened resin layer becomes brittle, resulting in difficulty in improving the flexibility. As a result, the resin layer is likely to be affected by fine cracks. On the other hand, when the rubber-modified polyamidoximine resin is added in an amount of more than 50 parts by weight, the burial property to the inner layer circuit is lowered, and as a result, pores are easily generated, and thus it is preferably avoided.

The D component is an organic phosphorus-containing flame retardant and is used to improve flame retardancy. The organic phosphorus-containing flame retardant is, for example, a phosphorus-containing flame retardant composed of a phosphate ester and/or a phosphazene compound. When the D component is 100 parts by weight of the resin composition, it is preferably used in an amount of from 3 parts by weight to 16 parts by weight. If the content of the component D is less than 3 parts by weight, the effect of flame retardancy cannot be obtained. On the other hand, even if the content of the component D exceeds 16 parts by weight, the improvement in flame retardancy cannot be expected. Further, a more preferable content of the component D is from 5 parts by weight to 14 parts by weight.

In addition, when the resin composition of the present invention has a resin composition weight of 100% by weight, it is preferable to add a total phosphorus content in the range of 0.5% by weight to 5% by weight to ensure flame retardancy. .

The E component is a biphenyl type epoxy resin. The biphenyl type epoxy resin contributes to the improvement of the so-called glass transition temperature Tg and the improvement of the flexibility. The biphenyl type epoxy resin is, for example, a biphenyl aralkyl type epoxy resin. When the component E is 100 parts by weight of the resin composition, it is preferably used in an amount of from 5 parts by weight to 35 parts by weight. When the content of the component E is less than 5 parts by weight, the effect of increasing the glass transition temperature Tg and the flexibility can not be obtained. On the other hand, even if the content of the component E exceeds 35 parts by weight, in addition to the inability to expect high Tg, the improvement in flexibility cannot be expected. Further, a more preferable content of the component E is 7 parts by weight to 25 parts by weight.

In addition to the above-mentioned components A to E, if the resin composition containing the phosphorus-containing flame retardant epoxy resin of the F component is further contained, the flame retardancy can be further improved. The "phosphorus-containing flame retardant epoxy resin" is a general term for an epoxy resin containing phosphorus in an epoxy skeleton, and is a so-called halogen-free flame retardant epoxy resin. Further, the phosphorus atom content of the resin composition of the present application is such that when the weight of the resin composition is 100% by weight, the phosphorus atom derived from the F component can be in the range of 0.1% by weight to 5% by weight. Phosphorus flame retardant epoxy resin can be used. However, from the viewpoint of excellent resin quality stability in a semi-hardened state and high flame retardancy effect, it is preferable to use 9,10-dihydro-9-oxo-10-phosphinophen-10-oxide. A phosphorus-containing flame retardant epoxy resin having two or more epoxy groups in the molecule of the derivative. For reference, the structural formula of 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide is shown in Figure 3:

[Chemical 3]

The phosphorus-containing flame-retardant epoxy resin having 2 or more epoxy groups in the molecule of the 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide derivative is preferably 9, 10-Dihydro-9-oxo-10-phosphanthene-10-oxide, reacting with naphthoquinone or hydroquinone to form a compound represented by the following 4 or 5, and then making the OH group portion and epoxy The resin is reacted to become a phosphorus-containing flame retardant epoxy resin.

[Chemical 4]

[Chemical 5]

Further, a phosphorus-containing flame retardant epoxy resin having 2 or more epoxy groups in the molecule of the 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide derivative is preferably exemplified. A compound having a structural formula represented by Chemical Formula 6, Chemical Formula 7, or Chemical Formula 8 is used.

[Chemical 6]

[Chemistry 7]

[化8]

When a phosphorus-containing flame retardant epoxy resin is used, the resin composition may be a single phosphorus-containing flame retardant epoxy resin or a mixture of two or more phosphorus-containing flame retardant epoxy resins. Resin. However, when considering the total amount of the phosphorus-containing flame retardant epoxy resin of the F component and the weight of the resin composition is 100% by weight, it is preferable that the phosphorus atom derived from the F component is in the range of 0.1% by weight to 5% by weight. Way to add. The phosphorus-containing flame retardant epoxy resin differs in the amount of phosphorus atoms contained in the epoxy skeleton depending on the type thereof. Here, the amount of the phosphorus component can be replaced by the content of the phosphorus atom as specified above. However, the F component is usually in the range of 5 parts by weight to 50 parts by weight when the resin composition is 100 parts by weight. When the F component is less than 5 parts by weight, considering the blending ratio of the other resin components, it is difficult to make the phosphorus atom derived from the F component 0.1% by weight or more, and the flame retardancy improving effect cannot be obtained. On the other hand, even if the F component exceeds 50 parts by weight, the flame retardancy-improving effect is saturated, and the hardened resin layer becomes brittle, so that it is preferably avoided.

The "high Tg" and "flexibility" of the above-mentioned cured resin layer are generally inversely proportional. In this case, the phosphorus-containing flame-retardant epoxy resin contributes to the flexibility of the resin layer after curing and contributes to high Tg. Therefore, compared with the case of using a single phosphorus-containing flame retardant epoxy resin, the "phosphorus-containing flame retardant epoxy resin contributing to high Tg" and "for the flexible lifting device" The contribution of the phosphorus-containing flame retardant epoxy resin can be used in a flexible printed circuit board as a preferred resin composition after being used in a balanced manner.

The resin composition of the present invention may further contain a G component which is a bisphenol A epoxy resin or a bisphenol F epoxy resin having an epoxy equivalent of 200 or less and a liquid at room temperature, and One or two or more epoxy resins are selected from the group consisting of bisphenol AD type epoxy resins. Here, the reason why the bisphenol-based epoxy resin is selected is that the compatibility with the component C (the rubber-modified polyamidoximine resin) is good, and it is easy to impart moderate flexibility to the semi-hardened resin layer. . However, if the epoxy equivalent exceeds 200, the resin will be semi-solid at room temperature, resulting in a decrease in flexibility in a semi-hardened state, and thus it is preferably avoided. In addition, in the case of the bisphenol-based epoxy resin, one type may be used alone or two or more types may be used in combination. In addition, when two or more types are used in combination, the mixing ratio is not particularly limited.

When the resin composition of the component G is 100 parts by weight, the resin composition is used in an amount of from 2 parts by weight to 15 parts by weight, and the thermosetting property can be sufficiently exhibited, and the general term can be reduced in a semi-hardened state. The curling phenomenon occurs, and it is preferable to further enhance the flexibility of the resin layer in the semi-hardened state. When the epoxy resin exceeds 15 parts by weight, the flame retardancy is lowered or the cured resin layer tends to be hard from the balance with other resin components. Further, considering the addition amount of the component C (rubber-modified polyamidoximine resin), sufficient hardness cannot be obtained in the cured resin layer.

The resin composition of the present invention may further contain a low-elastic substance composed of a thermoplastic resin and/or a synthetic rubber of the H component. By forming the resin composition containing the H component, it is possible to prevent the resin composition from being cracked in a semi-hardened state and to improve the flexibility after curing. Examples of the low-elastic substance of the H component include acrylonitrile-butadiene rubber, acrylic rubber (acrylate copolymer), polybutadiene rubber, isoprene, hydrogenated polybutadiene, and polyvinyl butadiene. Aldehyde, polyether oxime, phenoxy group, polymer epoxy, aromatic polyamine. One type may be used alone or two or more types may be used in combination. In particular, acrylonitrile-butadiene rubber is preferably used. Even in the acrylonitrile-butadiene rubber, if it is a carboxy modified product, a crosslinked structure can be obtained between the epoxy resin and the epoxy resin, and the flexibility of the cured resin layer can be improved. The carboxyl group-modified material preferably uses a carboxyl terminal nitrile butadiene rubber (CTBN), a carboxyl terminal butadiene rubber (CTB), or a carboxy modified nitrile butadiene rubber (C-NBR).

When the resin composition is 100 parts by weight, the H component is preferably used in an amount of 25 parts by weight or less. When more than 25 parts by weight of the H component is added, it is preferable to avoid problems such as a decrease in the glass transition temperature Tg, a decrease in solder heat resistance, a decrease in peel strength, and an increase in the coefficient of thermal expansion.

In the resin composition of the present invention, by combining the components A to E described above, it is possible to improve flame retardancy, increase the glass transition temperature Tg, and prevent thermal deterioration of the folding resistance. Further, in the case where an inorganic filler such as a resin composition for an adhesive is not conventionally added, sufficient flexibility can be obtained. Further, it is possible to prevent the occurrence of cracking in the semi-hardened state and the occurrence of the powder falling during the punching process.

The resin varnish of the invention of the present invention is a resin varnish according to the invention, wherein a solvent is added to the resin composition, and the solid content of the resin is adjusted to a range of 30% by weight to 70% by weight. Further, the semi-cured resin layer formed by the resin varnish is characterized in that the resin flow rate is in the range of 0% to 10% when the resin thickness is 55 μm according to MIL-P-13949G of the MIL standard. Here, the "solvent" is preferably selected from the group consisting of methyl ethyl ketone, dimethyl acetamide, dimethylformamide, and the like in the above-mentioned solvent having a boiling point of from 50 ° C to 200 ° C, or Two or more mixed solvents. The reason is as described above, and a good semi-hardened resin layer can be obtained. In addition, the "range of the amount of the solid content of the resin" shown here can be controlled to a range of high precision when applied to the surface of the copper foil. When the solid content of the resin is less than 30% by weight, the viscosity is too low, and it is difficult to ensure uniformity of the film thickness immediately after coating the surface of the copper foil. On the other hand, when the resin solid content exceeds 70% by weight, the viscosity is increased, which tends to cause difficulty in film formation on the surface of the copper foil.

When the resin lacquer is used to form a semi-hardened resin layer, it is preferred that the resin flow is in the range of 0% to 10%. If the flow of the resin is too high, the thickness of the insulating layer formed using the resin layer of the resin copper foil may be uneven. However, the resin paint of the invention of the present invention can suppress the flow of the resin to a value of less than 10%. Further, in the resin paint system of the present invention, the degree of resin flow is hardly observed, and thus the lower limit of the flow of the resin is set to 0%. In addition, the resin flow of the resin paint of the present invention is more preferably in the range of 0% to 5%.

In the present specification, the term "resin flow" refers to a sample in which four 10 cm squares are sampled from a resin copper foil having a resin thickness of 55 μm according to MIL-P-13949G of the MIL standard, and the four samples are placed in an overlapping state ( The laminated body was bonded at a pressure of 171 ° C, a pressure of 14 kgf/cm ² , and a pressing time of 10 minutes, and the calculated value of the resin outflow weight at this time was calculated based on the number 1.

[Number 1]

The resin copper foil of the present invention has a resin copper foil for producing a multilayer flexible printed circuit board having a resin layer on the surface of a resin copper foil-based copper foil. Further, the resin copper foil is characterized in that the resin layer is formed by using a resin composition for forming a bonding layer of the multilayer flexible printed wiring board.

Here, the copper foil is not particularly limited, and the relevant thickness is not particularly limited. Further, the method for producing the copper foil is not limited, and those obtained by various production methods such as an electrolytic method or a rolling method can be used. Further, one surface of the copper foil-forming resin layer may be subjected to a roughening treatment or may not be performed. If the roughening treatment is performed, the adhesion between the copper foil and the resin layer can be improved. However, if the roughening treatment is not performed, the formation of the ultrafine pitch circuit is enhanced because of the flat surface. Moreover, the surface of the copper foil may not be subjected to rustproof treatment. The relevant rust-preventing treatment may be carried out by using an inorganic rust such as zinc or a zinc-based alloy or the like, or an organic rust-proofing using an organic monomolecular film such as benzimidazole or triazole. Further, on the surface of the copper foil having the resin layer formed thereon, a decane coupling agent treatment layer is preferably provided.

The decane coupling agent layer has a function as an auxiliary agent for improving the wettability between the surface of the copper foil which is not subjected to the roughening treatment and the resin layer, and for improving the adhesion. For example, in the case where the roughening treatment of the copper foil is not performed, the rustproof treatment is performed, and for the decane coupling agent treatment, for example, an epoxy functional decane coupling agent, an olefin functional decane, an acrylic functional decane, or the like may be used. Various materials such as an amine functional decane coupling agent or a thiol-functional decane coupling agent can be selected and used as a decane coupling agent by a suitable use, and the peeling strength can be more than 0.8 kgf/cm.

The decane coupling agent which can be used is more specifically shown here. As the center of the same coupling agent used for the glass fiber cloth of the prepreg for printed circuit boards, for example, ethylene trimethoxy decane, ethylene phenyl trimethoxy decane, γ-methyl propylene methoxy propyl group can be used. Trimethoxydecane, γ-glycidoxypropyltrimethoxydecane, 4-epoxypropylbutyltrimethoxydecane, γ-aminopropyltriethoxydecane, N-β (amino group) Ethyl)-γ-aminopropyltrimethoxydecane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxydecane, imidazole Decane, three Decane, γ-thiolpropyltrimethoxydecane, and the like.

The formation of the decane coupling agent layer is, for example, a dipping method, a shower method, a spray method, or the like which are generally used, and the method is not particularly limited. As long as the step design is used, any method which can most uniformly contact the copper foil with the solution containing the decane coupling agent and adsorb it can be used. These decane coupling agents are dissolved in water of a solvent of 0.5 to 10 g/l and used at a temperature of room temperature. The decane coupling agent forms a film by condensing and bonding with an OH group protruding from the surface of the copper foil, so that even if a solution having a deliberately concentrated concentration is used, the effect is not significantly increased. Therefore, the Yuan should be determined in accordance with the processing speed of the steps. However, when it is less than 0.5 g/l, the adsorption rate of the decane coupling agent becomes slow, which is inconsistent with general commercial interests, and the adsorption is also uneven. Moreover, even if the concentration exceeds 10 g/l, the adsorption speed will not be particularly accelerated, and it is not economical.

The resin copper foil described above may be formed between a copper foil and a semi-hardened resin layer, such as a polyimide resin, a polyamide resin, a polyether oxime resin, a phenoxy resin, and an aromatic resin. One or a mixture of two or more kinds of a polyamide resin and a polyvinyl acetal resin constitutes an auxiliary resin layer. The auxiliary resin layer is formed before the formation of the semi-hardened resin layer. By using the two-layer structure of the auxiliary resin layer and the semi-hardened resin layer, the flexibility of the resin copper foil can be further improved, and it is preferable for the use of the flexible printed circuit board. These auxiliary resin layers can be formed by a general method called "casting method". More specifically, a resin varnish which is formed by forming a quinone imine resin, a polyamide resin, or both of these mixed resins is applied onto a copper foil surface, and a part of the solvent is subjected to a drying step. The removal is carried out by a solvent removal and/or a dehydration condensation reaction using a high temperature drying step. The thickness of the auxiliary resin layer at this time is preferably 10 μm or less. If it exceeds 10 μm, when combined with the semi-hardened resin layer referred to in the present invention, since the overall thickness is increased, it is difficult to thin the overall thickness when processed into a flexible printed circuit board, and at the same time, The heating at the time of forming the semi-hardened resin layer causes the resin copper foil to be easily curled, and thus it is preferably avoided.

The present invention provides a method for producing a resin copper foil, which is a method for producing a resin copper foil, which is a method for producing a resin copper foil for producing a multilayer flexible printed circuit board, characterized in that the following steps a and b are followed. The resin lacquer used in the formation of the resin layer is prepared in this order, and the resin varnish is applied onto the surface of the copper foil, and dried to form a semi-hardened resin layer having a thickness of 10 μm to 80 μm, thereby having a resin copper foil. Here, when the thickness of the semi-hardened resin layer is less than 10 μm, the adhesion between the semi-cured resin layer and the inner layer flexible printed circuit board is likely to vary.

Step a: When the weight of the resin composition is 100 parts by weight, the component A is 3 parts by weight to 30 parts by weight, the B component is 13 parts by weight to 35 parts by weight, and the C component is 10 parts by weight to 50 parts by weight. The D component is 3 parts by weight to 16 parts by weight, and the E component is in a range of 5 parts by weight to 35 parts by weight, and a resin composition of each component is contained. The description of each component and the blending ratio described herein is as described above, and thus will not be described herein. Further, the mixing order, the mixing temperature, the mixing order, the mixing device, and the like of the components are not particularly limited.

Step b: The above resin composition is dissolved using an organic solvent to form a resin varnish. The organic solvent at this time is a solvent having a boiling point of 50 ° C to 200 ° C, preferably a single solvent or a group selected from the group consisting of methyl ethyl ketone, dimethyl acetamide, dimethylformamide or the like. More than one kind of mixed solvent. The reason is as above. Further, a resin paint having a resin solid content of 30% by weight to 70% by weight is formed here. The reason for determining the range of the solid content of the resin is also as described above. Further, it is of course not possible to use all of the resin components used in the present invention in addition to the solvent specifically exemplified herein.

When the resin varnish obtained as described above is applied to one side of the copper foil, the relevant coating method is not particularly limited. However, in consideration of the necessity to apply the coating to the target thickness portion, it is sufficient to appropriately select a coating method or a coating device in which the film thickness to be formed is used. Further, drying after forming a resin film on the surface of the copper foil may be carried out by appropriately adding a heating condition capable of forming a semi-hardened state as long as the resin solution is blended.

The multilayer flexible printed circuit board of the present invention is characterized in that the multilayer flexible printed circuit board of the present invention is obtained by using a resin composition for forming a bonding layer of the above multilayer flexible printed wiring board. That is, the resin composition of the present invention is formed into a resin varnish, and the resin varnish is used to produce a resin copper foil. Then, the resin copper foil is used to form a multilayer flexible printed circuit board. At this time, there is no particular limitation on the manufacturing procedure until the multilayer flexible printed circuit board is formed using the resin copper foil. All known manufacturing methods can be used. In addition, the "multilayer flexible printed circuit board" as used in the present invention means a conductor layer having a circuit shape of three or more layers. The following examples are exemplified.

[Examples]

The resin components used in the examples and comparative examples are as follows. The synthesis example of the rubber-modified polyamidoximine resin of the C component and the phosphorus-containing flame retardant epoxy resin of the F component will be described later.

Component A: Solid high heat resistant epoxy resin (cresol novolac type epoxy resin YDCN-704 manufactured by Dongdu Chemical Co., Ltd., softening point 90 °C)

Liquid high heat resistant epoxy resin (HP4032-D made of naphthalene type epoxy resin DIC Co., Ltd.)

Component B: Epoxy resin hardener (biphenyl type phenol resin MEH-7851M manufactured by Minghe Chemical Co., Ltd.)

C component: rubber modified polyamidoximine resin

Component D: Phosphorus-containing flame retardant (aromatic condensed phosphate ester PX-200 manufactured by Daiba Chemical Co., Ltd.)

Component E: Biphenyl type epoxy resin (NC-3000, manufactured by Nippon Kayaku Co., Ltd.)

F component: phosphorus-containing flame retardant epoxy resin

Component G: Bisphenol A type liquid epoxy resin (Epicron 850S, manufactured by DIC Corporation)

H component: low elastic material (PNR-1H made by acrylonitrile-butadiene rubber JSR Co., Ltd.)

Modification of the rubber-modified polyamine amidoxime resin of the component C: Here, a four-necked flask equipped with a thermometer, a cooling tube, and a nitrogen introduction tube is used in the method described in JP-A-2004-152675. Among them, trimellitic anhydride (TMA) 0.9 mol, dicarboxy poly(acrylonitrile-butadiene) rubber (HIKER CTBN1300×13: molecular weight 3500) 0.1 mol, diphenylmethane diisocyanate (MDI) 1 Mole, and potassium fluoride 0.01 mol, according to the method of 20% solid content, loaded with N-methyl-2-pyrrolidone, stirred at 120 ° C for 1.5 hours, and then heated At 180 ° C, the mixture was stirred for about 3 hours to synthesize a 9-9 % by weight rubber polyami oxime imine resin. The obtained polyamidoximine resin had a logarithmic viscosity of 0.65 dl/g and a glass transition temperature of 160 °C.

Next, a synthesis example of the phosphorus-containing flame retardant epoxy resin of the relevant F component will be described.

Synthesis Example of Phosphorus-Containing Flame Retardant Epoxy Resin: 10-(2,5-dihydroxyphenyl) is packed in a four-neck glass separation flask equipped with a stirring device, a thermometer, a cooling tube, and a nitrogen gas introduction device. -10H-9-oxy-10-phosphaphenanthrene-10-oxide (HCA-HQ manufactured by Sanko Co., Ltd.), 324 parts by weight, and 300 parts by weight of ethyl cyproterone were dissolved by heating. 680 parts by weight of YDF-170 (bisphenol F-type epoxy resin manufactured by Tosho Kasei Co., Ltd.) was charged, and stirring was carried out while introducing nitrogen gas, and the mixture was heated to 120 ° C and mixed. 0.3 parts by weight of a triphenylphosphine reagent was added, and the reaction was carried out at 160 ° C for 4 hours. The obtained epoxy resin had an epoxy equivalent of 501 g/eq and a phosphorus content of 3.1% by weight.

Example 1: Example 1 is a resin composition containing the phosphorus-containing flame retardant epoxy resin, the rubber-modified polyamidoximine resin obtained by the above-described synthesis method, and the like, and the resin composition described in Table 1 is formed. A mixed solvent in which a solvent is a ratio of dimethylacetamide:methyl ethyl ketone = 3:2 (weight ratio) is used to prepare a resin varnish.

Example 2 to Example 7: Example 2 to Example 7 were replaced with the resin composition of Example 1, and the resin composition was used instead, and the resin composition of the formulation ratio shown in Table 1 was formed, and the solvent was further used. Ethyl amide, prepared as a resin lacquer. The rest are the same as in the first embodiment.

The resin paint was applied by an edge coater on a roughened surface of a commercially available electrolytic copper foil (thickness of 18 μm) so as to have a thickness of 50 μm after drying, and further 150 ° C, 3 After drying for a few minutes, the solvent was dispersed to form a resin copper foil. Using the resin copper foil, the glass transition temperature Tg, the resin layer flexibility evaluation after hardening, and the puncture performance evaluation were performed. Further, a multilayer printed wiring board having a resin copper foil was used, and a peeling strength, a normal solder heat resistance test, a boiling solder heat resistance test, and a moisture absorption solder heat resistance test were performed. Further, a resin copper foil having a resin layer having a thickness of 55 μm was produced in the same manner as in the above-described resin copper foil, and the flow of the resin was evaluated. The results of these assessments and test results are shown in Table 2.

[Evaluation of flexibility of resin layer after hardening]

Here, the resin copper foil was vacuum-bonded at a heating temperature of 190 ° C and a pressure of 40 kgf / cm ^{2 for} 90 minutes, and the copper foil was removed by etching, whereby a resin film having a thickness of 46 μm was obtained. Further, the resin film was cut into 30 mm × 5 mm to form a flexural test film. Then, using the flexural resistance test film, the flexural resistance test according to the MIT method was carried out. The flexural resistance test according to the MIT method is a grooved film fatigue fatigue tester (model: 549) manufactured by Toyo Seiki Co., Ltd., which is a MIT folding device, and has a deflection radius of 0.8 mm and a load of 0.5 kgf. The repeated bending test of the flexural test film prepared above was carried out. In Table 2 showing the results, the flexural resistance test film capable of measuring 2000 times or more of repeated bending times was rated as "acceptable ○". In addition, the number of times of repeated bending was determined by taking the drive head of the MIT folding device as one stroke (one cycle).

[resin flow]

The resin flow of the resin copper foil having a resin thickness of 55 μm was measured in accordance with the above conditions. Further, the resin flow was evaluated. First, the resin copper foil having the B-stage was punched from the copper surface side by a punch, and then vacuum-pressed for 90 minutes at a heating temperature of 190 ° C and a pressure of 40 kgf / cm ² . Then, after the press-fitting, the pierced portion was observed, and the resin bleed out from the edge of the pierced portion due to the press working was investigated, and the resin flow evaluation was performed. Here, the case where the resin bleed out from the edge of the pierced portion was 200 μm or less was evaluated as "pass ○". The evaluation results are shown in Table 2.

[Puncture performance]

The puncture performance of the resin copper foil in the B-stage is a resin copper foil of the B-stage, which is placed on the surface of the copper foil, and is punched by the punch from the lower side (resin surface) toward the upper surface (copper foil surface). machining. When the punching was performed by the punch, the case where the resin powder was generated was evaluated as "failed x", and although the resin powder did not occur, the crack occurred in the B-stage resin was rated as "acceptable". The case where no resin powder and cracks occurred in the B-stage resin was rated as "excellent ◎". The evaluation results are shown in Table 2.

[Measurement of glass transition temperature Tg]

A resin copper foil prepared as described above. The film was vacuum-bonded at a heating temperature of 190 ° C and a pressure of 40 kgf / cm ^{2 for} 90 minutes, and the copper foil was removed by etching, whereby a resin film having a thickness of 46 μm was obtained. Then, the resin film was cut into 30 mm × 5 mm, and the glass transition temperature Tg was measured. The glass transition temperature Tg was measured by a dynamic viscoelasticity measuring apparatus (model: SDM5600) manufactured by Seiko Instruments Inc. using a dynamic viscoelasticity measuring apparatus (DMA). The results are shown in Table 2 below.

[Evaluation using multilayer printed circuit boards]

Stripping strength and normal solder heat resistance test: On a double-sided 0.4 mm thick FR-4 (glass-epoxy substrate), a 18 μm-thick electrolytic copper foil was bonded to form a copper-clad laminate, and The inner layer circuit is formed on both sides, and the inner core material is obtained by wet blackening treatment. Next, on the both sides of the inner core material, the resin copper foil was laminated under vacuum pressure conditions of a heating temperature of 190 ° C and a pressure of 40 kgf / cm ² for 90 minutes to obtain a multilayer of four layers. A printed circuit board. Then, using the multilayer printed wiring board, a linear circuit for stripping test having a width of 10 mm was formed, and this was pulled and peeled toward the substrate surface at 90°, and the "stripping strength" was measured. In addition, a sample for solder heat resistance measurement of 50 mm × 50 mm size was cut out from a multilayer printed circuit board of four layers, floated in a solder bath of 260 ° C, and the time until expansion occurred was measured, and it was regarded as "normal solder heat resistance". "." The peeling strength was rated as "○" in the case of exceeding 1.0 kgf/cm, and "x" in the case of less than 1.0 kgf/cm. Moreover, the normal solder heat resistance was rated as "○" when it was more than 300 seconds, and it was rated as "x" when it was less than 300 seconds. The evaluation results are shown in Table 2.

Boiler solder heat resistance test: A sample of solder heat resistance measurement of 50 mm × 50 mm size is cut out from the above-mentioned four-layer multilayer printed wiring board, and the copper foil layer of the outer layer is etched and removed, and then immersed in boiling ion-exchanged water. 3 hours of boiling treatment. Then, from the sample which had been subjected to the boiling treatment, the water was sufficiently removed immediately, and immersed in a solder bath at 260 ° C for 20 seconds to confirm the presence or absence of expansion. If the non-expansive person is rated as "○", it will be confirmed by visual inspection that the expander is rated as "X". The results are shown in Table 2.

Moisture-absorbing solder heat resistance test: In the production of the above-mentioned four-layer multilayer printed wiring board, the resin copper foil was kept in a constant temperature and humidity chamber at a temperature of 30 ° C and a relative humidity of 65% for 15 hours to make the moisture absorber . The remaining four-layer multilayer printed circuit boards are fabricated as described above. Then, a sample for solder heat resistance measurement of 50 mm × 50 mm size was cut out from the four-layer multilayer printed wiring board, floated in a 260 ° C solder bath, and the time until expansion occurred was measured. The results are shown in Table 2. Those who have reached the time of swelling for more than 300 seconds are rated as "○", and those who have not exceeded 300 seconds are rated as "X".

[Comparative example]

In Comparative Example 1 and Comparative Example 2, instead of using the resin component described above, the resin composition was used instead, and the resin composition of the formulation ratio disclosed in Table 1 was formed, and the solvent was dimethylacetamide. A resin paint is prepared. The rest are the same as in the first embodiment.

As shown in Table 2, the resin copper foils shown in Examples 1 to 7 were able to obtain good evaluation results in terms of peeling strength, solder heat resistance, flexibility, and puncture performance. Further, the resin flow system was found to be 1% in Example 1 and Example 5, and Examples 2 to 4, Example 6, and Example 7 were extremely low results of less than 1%. The puncture performance of Example 2 and Example 3 showed very good results. In addition, in the holes formed by the punching process, the resin flow was also small, and good results were obtained. Moreover, the glass transition temperature Tg can form a sufficiently high temperature. On the other hand, in Comparative Example 1, the results of poor puncture performance were obtained, and in Comparative Example 2, the results of the difference between the normal solder heat resistance and the moisture absorption solder heat resistance were obtained.

Industrial availability

The resin composition of the present invention can be mounted in accordance with the high density of the flexible printed circuit board, and particularly has the flexibility and heat resistance of the multilayer flexible printed circuit board, and has high coupling reliability and can be utilized for high performance. Fabrication of multilayer flexible printed circuit boards.

Claims (12)

A resin composition for forming a bonding layer of a multilayer flexible printed circuit board, which is used for forming a bonding layer, which is used for multilayering an inner layer flexible printed circuit board, characterized in that: The resin composition contains the following components A to E: A component: a solid high heat resistant epoxy resin having a softening point of 50 ° C or higher (except for a biphenyl type epoxy resin); B component: An epoxy resin hardener composed of one or more of a biphenyl type phenol resin and a phenol aralkyl type phenol resin; and a C component: a rubber modified polyglycol which is soluble in a solvent having a boiling point of 50 ° C to 200 ° C Amidoxime resin; component D: organic phosphorus-containing flame retardant; and component E: biphenyl type epoxy resin. A resin composition for forming a bonding layer of a multilayer flexible printed wiring board according to the first aspect of the invention, which further comprises a phosphorus-containing flame retardancy of the F component in addition to each of the components A to E. Epoxy resin. The resin composition for forming a bonding layer of a multilayer flexible printed wiring board according to the first aspect of the invention, further comprising a G component which is liquid at an epoxy equivalent of 200 or less at room temperature. One or two or more epoxy resins selected from the group consisting of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol AD epoxy resin group. A resin composition for forming a bonding layer of a multilayer flexible printed wiring board according to the first aspect of the invention, further comprising an H component which is low in elasticity composed of a thermoplastic resin and/or a synthetic rubber. substance. The resin composition for forming a bonding layer of a multi-layer flexible printed circuit board according to the first aspect of the invention, wherein the above-mentioned component A has a softening point of 50 ° C or higher and a solid high heat-resistant epoxy resin, which is a cresol Any one or two or more of a phenolic epoxy resin, a phenol novolak epoxy resin, and a naphthalene epoxy resin. The resin composition for forming a bonding layer of a multilayer flexible printed wiring board according to the first aspect of the invention, wherein the component A further contains a phenolic epoxy resin or cresol which is liquid at room temperature. A high heat-resistant epoxy resin comprising one or more of a phenolic epoxy resin, a phenol novolak epoxy resin, and a naphthalene epoxy resin. The resin composition for forming a bonding layer of a multilayer flexible printed wiring board according to the first aspect of the invention, wherein the component A is from 3 parts by weight to 30 parts by weight when the weight of the resin composition is 100 parts by weight. The component B is 13 parts by weight to 35 parts by weight, the C component is 10 parts by weight to 50 parts by weight, the D component is 3 parts by weight to 16 parts by weight, and the E component is 5 parts by weight to 35 parts by weight. A resin varnish, which is added to a resin composition of the first application of the patent application, and is prepared in a range of 30% by weight to 70% by weight of the resin solid content, and is characterized in that, when a semi-hardened resin layer is formed, according to MIL specifications MIL-P-13949G, when measured according to the resin thickness of 55 μm, the resin flow range is 0% to 10%. A resin flexible copper foil for manufacturing a multilayer flexible printed circuit board having a resin layer on the surface thereof, wherein the resin layer is bonded using a multilayer flexible printed circuit board of claim 1 It is formed by the resin composition for layer formation. A resin copper foil for producing a multilayer flexible printed circuit board according to claim 9 is characterized in that the surface of the copper foil-forming resin layer is provided with a decane coupling agent treatment layer. A method for producing a resin copper foil for manufacturing a multilayer flexible printed circuit board, and a method for producing a resin copper foil for manufacturing a multilayer flexible printed circuit board according to claim 9 characterized in that: In the order of step a and step b, the resin varnish used in the formation of the resin layer is prepared, and the resin varnish is applied onto the surface of the copper foil, and dried to form a semi-hardened resin layer having a thickness of 10 μm to 80 μm. Resin copper foil; Step a: When the weight of the resin composition is 100 parts by weight, the component A is 3 parts by weight to 30 parts by weight, the B component is 13 parts by weight to 35 parts by weight, and the C component is 10 parts by weight. 50 parts by weight, 3 parts by weight to 16 parts by weight of the D component, and 5 parts by weight to 35 parts by weight of the E component, and a resin composition containing each component; Step b: Dissolving the above resin composition using an organic solvent A resin varnish having a resin solid content of 30% by weight to 70% by weight is formed. A multilayer flexible printed circuit board obtained by using a resin composition for forming a bonding layer of a multilayer flexible printed circuit board according to the first aspect of the invention.