Patent Application
20140224529
The present invention relates to a halogen-free flame-retardant resin composition. More specifically, in the field of electronic materials, the present invention relates to a composite composed of glass fiber and to a flame-retardant resin composition that is primarily used in adhesives for polyimide, metal foil, and the like, as well as a flexible printed wiring board metal-clad laminate, a coverlay, an adhesive sheet, and a flexible printed wiring board that are produced using these materials.
Flame-retardant resin compositions are widely used as adhesives in the field of electronic materials (in particular, in printed wiring boards (more specifically, flexible printed wiring boards (FPCs below) that are composed of metal-clad laminates and other substrates)). These compositions are primarily used as adhesives for adhering metal foils (e.g., copper foil) with films (e.g., polyester film or polyimide film), metal foils with each other, films with each other, composites comprising glass fiber with the aforementioned metal foils, and the aforementioned composites with films.
With the objective of improving adhesive properties or heat resistance for applications such as adhesives for circuit boards, Japanese Unexamined Patent Application Publication No. 2001-002931 discloses a flame-retardant resin composition that comprises a resin having intramolecular phosphorus atoms (e.g., a phosphorus-containing polyester resin or a phosphorus-containing polyurethane resin), a phosphorus-containing compound (e.g., ammonium polyphosphate), and, as necessary, an epoxy resin, and an isocyanate compound or other hardener (Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2001-002931).
However, with the flame-retardant resin composition described in that publication, the low molecular weight phosphorus-containing compound (phosphorus-based flame retardant) is contained at a specified amount, and, when the composition is to be used as an adhesive for printed wiring boards, hydrolysis of the phosphorus-containing compound by the absorbed water content is thought to cause a dramatic decrease in adhesion strength or migration characteristics. In addition, with these flame-retardant resin compositions, the characteristics (e.g., glass transition temperature or elastic modulus) of the resin composition will degrade subsequent to curing and molding, resulting in problems with insufficient manifestation of effects related to electrical characteristics and the like in the molded and cured printed wiring board. Moreover, these flame-retardant resin compositions also have problems with providing sufficient effects particularly in regard to flame retardancy and adhesion, depending on the proportion of epoxy resin and hardener with respect to phosphorus.
The invention is intended to resolve the problems with the prior art described above. Specifically, an aim of the present invention is to provide a flame-retardant resin composition that has superior adhesion subsequent to curing and molding when used as an adhesive for printed wiring boards, and also superior printed wiring board electrical characteristics.
The present invention attains the aim described above by providing a flame-retardant resin composition that comprises a thermosetting resin, a hardener, and a phosphonate-containing polymer.
In accordance with the present invention, a flame-retardant resin composition is provided that has superior adhesion subsequent to curing and molding when used as a printed wiring board adhesive and also superior printed wiring board electrical characteristics. In addition, the present invention also offers a superior flexible printed wiring board metal-clad laminate, a coverlay, an adhesive sheet, and a flexible printed wiring board that are produced by using this flame-retardant resin composition.
The disclosure of the invention presented above does not list all of the necessary features of the present invention. Sub-combinations within these groups of features may also constitute the invention.
(Flame-Retardant Resin Composition)
The flame-retardant resin composition of the present invention is primarily desirable for use in applications such as flexible printed wiring board metal-clad laminates, coverlays, adhesive sheets, flexible printed wiring boards, and the like. The term “flexible printed wiring board metal-clad laminate” used herein refers to a material having a film and metal foil laminated together. In addition, the term “coverlay” refers to a material that is provided in order to protect the circuitry of a flexible printed wiring board metal-clad laminate having a conductor pattern (also referred to as “circuits” below) that has been formed in a metal foil. The coverlay is provided, for example, by a means such as applying a single layer or a multilayer laminate of the resin composition on a synthetic resin film having electrical insulation properties. In addition, the term “flexible printed wiring board” refers to a board in which a coverlay has been provided over the necessary regions on a flexible printed wiring board metal-clad laminate that has circuits.
The flame-retardant resin composition of the present invention is preferably used primarily in the applications described above, but the invention can also be used in multilayer printed wiring boards, flex-rigid printed wiring boards, and the like. An example of a flex-rigid printed wiring board referred to herein that may be cited is the flex-rigid printed wiring board 40 having the configuration shown in
The flame-retardant resin composition of the present invention is produced by blending a thermosetting resin, a hardener, and a phosphonate-containing polymer. The phosphonate-containing polymer is a phosphonate-containing polymer that has properties whereby it provides flame-retardancy. By blending this phosphonate-containing polymer, high flame retardancy is manifested.
In addition, the flame-retardant resin composition of the present invention comprises, as basic components, a thermosetting resin, a hardener, and a phosphonate-containing polymer or oligomer. As a result, the amount of additive for imparting flame retardancy relative to the entire resin composition can be decreased. As a result, the compatibility and mold workability of the flame-retardant resin composition prior to curing are favorable, and the adhesion characteristics and electrical characteristics of the flame-retardant resin composition subsequent to curing and molding can be improved.
Examples of the phosphonate-containing polymer that may be cited include polymers and copolymers or oligomeric versions thereof having the structural units represented by formula (1) below in the polymer main chain or in the polymer side chains.
(In formula (1), Ar is an aromatic group-containing structure and —O—Ar—O— is derived from a group consisting of resorcinol, hydroquinone, biphenol, or bisphenol, R is a C1-20 alkyl, C2-20 alkene, C2-20 alkyne, C5-20 cycloalkyl, or C6-20 aryl, and n is an integer from 1 to 300, and the phosphorus in the phosphonate-containing polymer is contained at 12 wt % or less. In such embodiments, —O—Ar—O— is derived from a group consisting of bisphenol A, bisphenol F, 4,4′-bisphenol, phenolphthalein, 4,4′-thiodiphenol, 4,4′-sulfonyldiphenol, 3,3,5-trimethylcyclohexyldiphenol, and combinations thereof.)
Further specific examples of the phosphorus-containing polymer that may be cited include polymers and copolymers having the structural units represented by formula (2) below in the polymer main chain or in the polymer side chains.
(In formula (2), R1 and R2 may be the same or different and denote hydrogen atoms, methyl groups, or lower alkyl groups and n is an integer of 50 to 300.)
The phosphorus content in the phosphonate-containing polymer is less than about 12 wt %, less than about 10 wt %, or less than about 9.5 wt %, or from about 5 wt % to about 12 wt % or about 7 wt % to about 10 wt %. The phosphonate-containing polymer exhibits a weight average molecular weight (molecular weight measured against polystyrene (polystyrene standards), the same hereinafter) of greater than about 2,500, greater than about 5,000, greater than about 9,000, greater than about 20,000, or about 2,500 to about 200,000, about 5,000 to about 150,000, or about 9,000 to about 100,000. The phosphonate-containing polymer exhibits a high Tg (glass transition temperature), where high Tg is defined as being 100° C. or greater. As a result of these properties or a combination thereof, high flame retardancy effects can be manifested while using only small amounts of the phosphonate-containing polymer in the cured resin composition. Moreover, the phosphorus-containing polymer incorporates structures related to the phosphorus compounds in its main chain or in its side chains. Specifically, the structures related to the phosphorus component are protected by chemical bonding. As a result, the phosphorus component will not precipitate from the resin composition, and a flame-retardant resin composition will be produced that has excellent electrical characteristics and is resistant to hydrolysis by its water content.
The phosphonate-containing polymer or oligomer can also be a block copolymer or random copolymer (phosphonate carbonate). These copolymers (phosphonate carbonate) may include at least 20 mol % high-purity diaryl alkylphosphonate or optionally substituted diaryl alkylphosphonate, and one or more aromatic dihydroxide, wherein the mol % of the high-purity diaryl alkylphosphonate is based on the total amount of transesterification components, e.g., total diaryl alkylphosphonate and total diaryl carbonate. The term “random” means that the monomers of the copolymer (phosphonate carbonate) of various embodiments are incorporated into the polymer chain randomly. Therefore, the polymer chain may include copolymerized phosphonate and carbonate monomers alternately linked by an aromatic dihydroxide and/or various segments in which several phosphonate or several carbonate monomers form oligophosphonate or polyphosphonate or oligocarbonate or polycarbonate segments. Additionally, the length of various oligomers or polyphosphonate oligomers or polycarbonate segments may vary within individual copolymers (phosphonate carbonate).
The phosphonate and carbonate content of the copolymers (phosphonate carbonate) may vary and is not limited by the phosphonate and/or carbonate content or range of phosphonate and/or carbonate content. For example, the copolymer (phosphonate carbonate) may have a phosphorus content, which is indicative of the phosphonate content of from about 1% to about 20% by weight of the total copolymer (phosphonate carbonate), or the phosphorous content of the copolymer (phosphonate carbonate) of the invention may be from about 2% to about 10% by weight of the total polymer.
The copolymer (phosphonate carbonate) of various embodiments exhibits both a high molecular weight and a narrow molecular weight distribution (e.g., low polydispersity). For example, the block copolymer or random copolymer (phosphonate carbonate) may have a weight average molecular weight (Mw) of about 10,000 g/mole to about 100,000 g/mole as determined by ηrel or GPC, or the block copolymer or random copolymer (phosphonate carbonate) may have a weight average molecular weight (Mw) of about 12,000 g/mole to about 80,000 g/mole as determined by ηrel or GPC. The narrow molecular weight distribution (e.g., Mw/Mn) of such a block copolymer or random copolymer (phosphonate carbonate) may be from about 2 to about 7 or about 2 to about 5. This block copolymer or random copolymer (phosphonate carbonate) may have a relative viscosity of about 1.10 to about 1.40.
The high molecular weight distribution and narrow molecular weight distribution of the block copolymer and random copolymer (phosphonate carbonate) may impart a superior combination of properties. For example, the block copolymer and random copolymer (phosphonate carbonate) are generally tough, extremely flame-retardant, and exhibit superior hydrolytic stability. In addition, the block copolymer and random copolymer (phosphonate carbonate) exhibit an excellent combination of processing characteristics including, for example, good thermal and mechanical properties.
The blend amount of the phosphonate-containing polymer in the flame-retardant resin composition is preferably 5 to 50 parts, more preferably 10 to 40 parts by weight, with respect to 100 parts by weight of the thermosetting resin.
Examples of thermosetting resins that are used in the flame-retardant resin composition include epoxy resins and phenol resins. Epoxy resins are particularly preferred form the standpoint of adhesion with respect to metal foils or films and stability in a semi-cured state (known as the B-stage).
Examples of epoxy resins that may be used include epoxy resins that have at least two epoxy groups per molecule and do not contain halogen. Specific examples that may be cited include bisphenol epoxy resins (e.g., bisphenol A, bisphenol F, and bisphenol S resins), novolak epoxy resins (e.g., phenol novolak and cresol novolak resins), biphenyl epoxy resins, naphthalene ring-containing epoxy resins, and aliphatic epoxy resins. From the standpoint of improving flame retardancy, bisphenol F epoxy resins, bisphenol S epoxy resins, and novolak epoxy resins are preferred.
The epoxy resins described above may be used in conjunction with phosphorus-containing epoxy resins. In addition, phosphorus-containing epoxy resins may be used instead of epoxy resins. Moreover, phosphorus-containing epoxy resins and phosphorus-containing polymers may be used in conjunction. Phosphonate-containing epoxy resin, for example, may be obtained by allowing an oligomer represented by formula (2) below to react with at least one of the epoxy resins described above for 2 to 5 hours at 100 to 150° C.
(In formula (3), n denotes an integer of 1 to 16.)
There are no particular restrictions on the hardener, provided that it is used as a hardener for thermosetting resins. For example, when an epoxy resin is used as the thermosetting resin, the hardener is preferably used in combination with a hardener for the epoxy resin.
Specific examples of hardeners include diaminodiphenylmethane (DDM), diaminodiphenylsulfone (DDS), diaminodiphenylether (DDE), imidazole, hexamethylenediamine, polyamidoamine, dicyan diamide, and phenol novolak. In particular, from the standpoint of reaction stability, amine-based hardeners and phenol-based hardeners are preferred, with amine-based hardeners being particularly preferred. An oligomer of formula (2) may be used as a phenol-type hardener. In this case, it is preferable to use an imidazole that will serve as the epoxy resin polymerization catalyst in conjunction. As a result, the phosphorus content in the resin composition will increase, allowing a further increase in flame retardancy.
The blend amount of hardener in the flame-retardant resin composition is preferably 1 to 200 parts by weight, more preferably 3 to 100 parts by weight, with respect to 100 parts by weight of the thermosetting resin. A curing accelerator may be used in conjunction as necessary with these hardeners.
From the standpoint of improving flexibility and adhesion, flexibilizing agents are preferably added to the flame-retardant resin composition. Examples of flexibilizing agents that may be cited include acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), acrylate butadiene rubber (ABR), acrylic rubber (ACM, ANM) and other synthetic rubbers, as well as polyester resin, polystyrene resin (PS), polyether sulfone resin (PES), polyurethane resin (PU), polyamide resin (PA), and other thermoplastic resins.
The blend amount of flexibilizing agent in the flame-retardant resin composition is preferably 3 to 80 parts by weight, more preferably 5 to 60 parts by weight, with respect to 100 parts by weight of thermosetting resin.
In addition, flame retardants other than the phosphonate-containing polymer may be added to the flame-retardant resin composition in order to improve handling (e.g., control tack) when the resin composition is made to assume a semi-cured state (B-stage state), in order to improve adhesion of the resin composition subsequent to curing, and in order to facilitate adjustment of melt viscosity. Examples of flame retardants that may be cited include metal hydrates such as aluminum hydroxide and magnesium hydroxide, metal carbonates such as calcium carbonate, and other such metal-containing flame retardants.
The blend amount of metal-containing flame retardant in the flame-retardant resin composition is 10 to 200 parts by weight, preferably 20 to 150 parts by weight, with respect to 100 parts by weight of the thermosetting resin. As a result, the electrical characteristics and adhesion of the resin composition subsequent to curing can be improved. In addition, when used in a coverlay, the resin composition can be fully transferred between the circuits, allowing an improvement in flame retardancy.
In addition to the various components mentioned above, various types of additives (e.g., antioxidants, surfactants, and coupling agents) may also be added, as required, to the flame-retardant resin composition in ranges that do not compromise its various characteristics.
The flame-retardant resin composition is used after curing thereof at the time of use (in particular, when used in the above applications). The extent to which the resin composition is cured is determined in accordance with the application, equipment, and the like. Normally, the composition is used after curing under prescribed conditions of heating, pressure, and the like. In terms of prescribed conditions, a temperature of 130 to 180° C. is preferred, a pressure of 2 to 5 MPa/cm2 is preferred, and a time of 10 to 60 min is preferred.
(lexible Printed Wiring Board Metal-Clad Laminate)
The flexible printed wiring board metal-clad laminate of the present invention, as shown in
With the metal-clad laminate of the present invention, the film thickness is 4 to 75 μm, and the thickness of the layer that is composed of the flame-retardant resin composition that is used as adhesive is preferably 5 to 30 μm.
In another embodiment of the metal-clad laminate of the present invention, as shown in
Examples of the film that is used include a polyimide film, polyester film, and polyamide film. Among these, a polyimide film is preferred from the standpoint of flame retardancy, electrical insulation, heat resistance, and elastic modulus. Films made from other materials may also be used.
In addition, for example, a conductive material such as metal copper foil or silver foil may be used as the metal foil.
Polyimide film is used as the film 2 in the metal-clad laminates 20, 21 shown in
(Coverlay)
The coverlay of the present invention, as shown in
Examples of the coverlay of the present invention that may be cited are coverlays having a configuration in which the flame-retardant resin composition described above is applied in the form of a laminate to a synthetic resin film having electrical insulation properties. This type of coverlay is used as a material that is provided in order to protect circuits, such as with a flexible printed wiring board metal-clad laminate that has circuits.
With the coverlay of this embodiment, the thickness of the synthetic resin film is 4 to 75 μm, and the thickness of the layer composed of flame-retardant resin composition is preferably 5 to 50 μm.
Examples of synthetic resin films that may be cited include polyimide films, polyester films, and polyamide films, with polyimide films being preferred among them from the standpoint of flame retardancy, electrical insulation, heat resistance, and elastic modulus.
A polyimide film is used as the film 2 in the coverlay 10 shown in
(Flexible Printed Wiring Board Adhesive Sheet)
The flexible printed wiring board adhesive sheet of the present invention is composed of the flame-retardant resin composition described above and has the form of a sheet. Specifically, the flame-retardant resin composition is applied to the mold-release surface of a mold release film to produce a sheet-form adhesive sheet that is in a semi-cured state.
The thickness of the adhesive sheet of the present invention is preferably 10 to 60 μm. The adhesive sheet of the present invention is a sheet that can be used when adhering metal foils, films, metal foils with composites composed of glass fiber and thermosetting resin, or films with these composites.
(Flexible Printed Wiring Board)
The overall thickness of the flexible printed wiring board of the present invention can be set as desired in accordance with the application.
In a preferred mode of the flexible printed wiring board of the present invention, the coverlay described above and the flexible printed wiring board metal-clad laminate on which circuits have been formed are glued together by hot-pressing. In this case, preferred hot-pressing conditions are a temperature of 130 to 180° C., a pressure of 2 to 5 MPa, and a time of 10 to 60 min.
The flexible printed wiring board of the present invention is desirable for use, for example, in so-called “chip-on-flex” applications on flexible printed wiring boards for mounting IC chips.
With the flexible printed wiring boards 30, 31 shown in
Working examples of the present invention are provided below in order to describe the present invention in additional detail, but the invention is not in any way restricted by these working examples.
The compounds shown in Tables 1 and 2 were each prepared. The values indicated for parts reflect the solid content equivalent. The examples shown in Tables 3 and 4 were made using different flame retardants as indicated in the Tables.
The data in Table 1 show that a non flame-retardant epoxy resin does not exhibit any flame retardancy. When using only metal-containing flame retardant (with or without flexibilizing agent), it was not possible to achieve flame retardancy.
Table 2 shows the use of phosphonate-containing polymers (FRX-100), phosphonate-containing copolymers (FRX CO-35, FRX CO-60, and FRX CO-95), or oligomers (FRX-OL1001-based phosphonate-containing epoxy resin). FRX-100 is aphosphonate polymer having the structure shown in Formula 1. FRX CO-35, FRX CO-60, and FRX CO-95 are random copolymers comprising diphenyl carbonate, diphenylmethylphosphonate, and bisphenol A together with different weight percentages of phosphonate. Phosphonate-containing portions of the copolymers have the structure shown in Formula 1. FRX (OL1001) is an oligomeric version of FRX-100, with a smaller degree of polymerization than FRX-100 and having the structure shown in Formula 3. Using the correct structures containing these materials, it is possible to obtain materials that fulfill the requirements for flame retardancy, heat resistance, and migration resistance.
The data in Table 3 show that by using polyphosphonate compounds as the flame retardant component in the compositions, it is possible to obtain an optimized characteristics profile of the flexible printed wiring board, these characteristics passing the FR test, having a desired low loop stiffness (lower is better) and having solder float heat resistance (at least 288° C. is required) such as to be adequate for the application. Surprisingly, a decrease in molecular weight of the phosphonate-containing material (from 80,000 to 30,000 g/mole (polystyrene standards)) improves the loop stiffness.
The data in Table 4 show that by using a relatively high molecular weight flame retardant compound in the formulation, the migration resistance of the composition can be considerably improved.
In order to balance all the characteristics for the final application (e.g. low loop stiffness combined with excellent migration resistance), an optimum molecular weight is required that will be between 2,000 and 40,000 g/mole.
The details of the components in Tables 1 to 4 are as follows. Epoxy resin: Bisphenol-type epoxy resin with an epoxy equivalent weight of 170 g/eq (solid content 100%).
Phosphonate-containing polymer: FRX-100 (manufactured by FRX Polymers, solid content 100%, phosphorus content 10.8 wt %, molecular weight (Mw) 30,000 to 200,000 g/mole (polystyrene standards), glass transition temperature 100° C. to 107° C.); FRX-0095 (manufactured by FRX Polymers, solid content 100%, phosphorus content 10.1 wt %, molecular weight (Mw) 30,000 to 100,000 g/mole (polystyrene standards), glass transition temperature 100° C. to 107° C.); FRX CO-60 (manufactured by FRX Polymers, solid content 100%, phosphorus content 6.4 wt %, molecular weight (Mw) 30,000 to 100,000 g/mole (polystyrene standards), glass transition temperature 115° C. to 125° C.); FRX-CO35 (manufactured by FRX Polymers, solid content 100%, phosphorus content 3.7 wt %, molecular weight (Mw) 30,000 to 100,000 g/mole (polystyrene standards), glass transition temperature 125° C. to 135° C.); FRXL100 (manufactured by FRX Polymers, solid content 100%, phosphorus content 10.8 wt %, molecular weight (Mw) 25,000 to 45,000 g/mole (polystyrene standards), glass transition temperature 100° C. to 107° C.); FRX-OL5000 (manufactured by FRX Polymers, solid content 100%, phosphorus content 10.5 wt %, molecular weight (Mw) 8,000 to 10,000 g/mole (polystyrene standards), glass transition temperature 85° C. to 95° C.). In the tables, the phosphorus content (wt %) is a percentage value determined by dividing the amount of phosphorus contained in the phosphorus-containing polymer by the total amount of the thermosetting resin (solid content equivalent), hardener (solid content equivalent), and phosphorus-containing polymer (solid content equivalent).
Phosphorus-containing epoxy resin: The resins indicated below were used.
Hardener: Diaminodiphenylmethane (DDM, solid content 100%).
Flexibilizing agent: Nipol 1072 (manufactured by Nippon Zeon, solid content 100%).
Metal-containing flame retardant: Aluminum hydroxide (Higilite H43STE, manufactured by Showa Denko K.K.).
(Preparation of Phosphorus-Containing Epoxy Resin)
The phosphorus-containing epoxy resin was prepared by weighing 550 g of bisphenol A epoxy resin (JER 828, manufactured by Mitsubishi Kagaku) with an epoxy equivalent weight of 188 g/eq and 450 g of phosphorus-containing oligomer (FRX OL 1001, manufactured by FRX Polymers, solid content 100%, phosphorus content 8 to 10 wt %, Mw 2,000 to 4,500 g/mole (polystyrene standards)) into a 2-L separable flask, then stirring the materials while heating at 130° C. 2.5 g of triphenylphosphine was then added, and the materials were stirred while heating for approximately 3 hours to obtain a phosphorus-containing epoxy resin with an epoxy equivalent weight of about 510 g/eq and a phosphorus content of about 4.1 mass %.
(Flame Retardancy (UL-94-V0))
Resin sheet samples were prepared from the respective resin compositions in accordance with the UL94 standard. The curing conditions for the sheet samples were adjusted to produce a C-stage state (completely cured state). The curing conditions were as follows.
Flame retardancy was evaluated using the following criteria based on whether or not the material reached the V-0 grade in accordance with the UL94 standard.
(Heat Resistance)
Heat resistance was evaluated by producing samples for evaluation from the respective resin compositions. The evaluation method was carried out as prescribed by IPC TM650.
The samples for evaluation were produced by the following procedure. First, the respective resin compositions were applied onto a polyimide film (Apical 25NPI, manufactured by Kanegafuchi Chemical Industry) using a bar coater to produce a dried thickness of 10 μm. After heating and drying for 5 min at 150° C. to produce a B-stage state (semi-cured state), the roughened surface of an electrolytic copper foil (3EC-3, 18 μm, manufactured by Mitsui Mining and Smelting) was glued to the resin composition surface using a laminator to produce a one-sided board, which was then cured to a C-stage state for 1 hour at 180° C., thereby producing a sample.
(Migration Resistance)
The migration resistance was tested under prescribed conditions (voltage: 100 V, temperature: 85° C., humidity: 85% RH), and evaluation was carried out based on the change in voltage over a constant time period (1000 hrs). The migration resistance was evaluated based on the following criteria.
(Loop Stiffness)
Measured in accordance with JPCA-TM0002
(Soldering Resistance)
Measured in accordance with IPC TM650.
(Peel Strength)
The 90° peel strength was measured using an autograph AGS-500 produced by Shimadzu as the measurement apparatus. The conditions involved pulling a base film, the test speed was 50 mm/min, and the test was carried out at room temperature.
(Flame Retardancy (UL-94-VTM-0))
Resin sheet samples of the respective resin compositions were produced in accordance with the UL94 standard. The samples were prepared in a C-stage cured state (completely cured state). The curing conditions were as follows.
(1) Heating Temperature: 180° C., (2) Time: 60 Min.
The flame retardancy (UL-94-VTM-0) was used to confirm whether or not the VTM-0 grade of the UL94 standard could be attained.
Samples for evaluation were produced by the procedure described below. First, the one-sided copper-clad laminate shown in
The pattern for evaluating migration was a comb-shaped pattern with an L/S (line/space) ratio of 100/100.
Migration (also referred to as “copper migration”) refers to a phenomenon in which the application of voltage between copper foil circuits causes elution of copper ions from the positive electrode and deposition of copper at the negative electrode with ionic impurities in the adhesive serving as a medium. Increasing deposition of this type is reflected by a decrease in resistance value between the circuits.
In accordance with the experimental results obtained in the various examples described above, the flame-retardant resin composition of the present invention was confirmed to have superior flame retardancy subsequent to curing and molding when used as a printed wiring board adhesive, while also providing superior adhesion and printed wiring board electrical characteristics.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-125437 | Jun 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/064859 | 6/4/2012 | WO | 00 | 3/24/2014 |
