JP2006022317A - Epoxy resin film, optical waveguide, optoelectric composite substrate, and optical communications module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin film which has a processing temperature suitable for the production process of printed wiring boards, has a sufficient heat resistance against the temperature of the process for mounting electronics parts and optical devices finally on a printed wiring material and has a low loss as an optical waveguide in order to make a multi-mode waveguide usable by unifying it with a printed wiring board. <P>SOLUTION: A resin composition containing an epoxy resin A obtained by adding 1,2-epoxy-4-(2-oxiranyl)cyclohexane to 2,2-bis(hydroxymethyl)-1-butanol, a copolymer B obtained by copolymerizing at least one of styrene, cyclohexylmethyl (meth)acrylate and adamantylmethyl (meth)acrylate, with an epoxidized cyclohexylmethyl (meth)acrylate, and a cation polymerization initiator is molded as a film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photo-curing or thermosetting epoxy resin film used to form an optical waveguide used integrally with an electric wiring such as a printed wiring board, an optical waveguide for optical transmission, and an opto-electric composite. The present invention relates to a substrate and an optical communication module.

As a proposed method for forming a core of a multimode optical waveguide, a necessary part that becomes a core is cured using a liquid curable resin and an unnecessary part is developed and removed (for example, a patent) Reference 1), a method of increasing the refractive index of the exposed portion using diffusion of monomers contained in the thermoplastic resin sheet (see, for example, Patent Document 2), and the refractive index of the exposed portion using polysilane. And by exposing the various acrylates to a pattern by applying a method in which an unexposed portion having a high refractive index is used as a core (see, for example, Patent Document 3) or a technique employed in a resist material such as a dry film. And a method of developing with an aqueous developer (see, for example, Patent Document 4 and Patent Document 5).
Japanese Patent No. 30603903 JP-A-1-302308 JP 2004-12635 A JP 2000-81520 A JP 2003-128737 A

  However, the method of using a liquid curable resin is one in which the epoxy resin is photocured and the unexposed portion is washed away with a solvent and developed. There were problems that it was difficult to increase the area and productivity was poor.

  In addition, according to the method of increasing the refractive index of the exposed portion by utilizing the diffusion of the monomer contained in the thermoplastic resin sheet, the resin is used at the temperature received in the process of being integrated with the printed wiring board or the subsequent solder reflow process. There is a drawback that the waveguide portion is deformed because it does not have its own heat resistance.

  In addition, in the method using polysilane, a heat treatment at about 300 ° C. is necessary to eliminate the exposure property of polysilane in the exposed portion, so that the printed wiring board which is an organic material cannot withstand the temperature, and is used in an integrated manner. Is difficult.

  In addition, in the method using various acrylates by applying the technique adopted for resist materials such as dry film, the transparency of the resin itself cannot be increased, so that the waveguide loss is about 0.3 dB / cm or more. There is a problem of being big.

  The present invention has been made in view of the above points, and in order to enable the practical use of a multimode waveguide that can be used integrally with a printed wiring board, an epoxy having a processing temperature that is easy to introduce into the manufacturing process of the printed wiring board. It is a resin film that has heat resistance that can withstand the temperature of the process of finally mounting electronic components and optical elements on printed wiring materials, and uses a low-loss epoxy resin film as an optical waveguide. It is an object of the present invention to provide an optical waveguide formed in this manner, an optoelectric composite substrate formed with the optical waveguide, and an optical communication module.

  The epoxy resin film according to claim 1 of the present invention is an epoxy resin A obtained by adding 1,2-epoxy-4- (2-oxiranyl) cyclohexane to 2,2-bis (hydroxymethyl) -1-butanol. And at least one compound selected from styrene, a compound represented by the following general formula (1), a compound represented by the following general formula (2), and a compound represented by the following general formula (3) A resin composition containing the coalesced polymer B and a cationic polymerization initiator is formed into a film shape.

  The invention of claim 2 is the copolymer polymer B according to claim 1, wherein the copolymer polymer B is obtained by copolymerizing styrene and the compound represented by the general formula (3), and the copolymer polymer. The molecular weight of B is 4000-40000.

  The invention of claim 3 is the invention according to claim 1 or 2, wherein the cationic polymerization initiator is a photocationic initiator, and one or both of the bisphenol A type epoxy resin and the bisphenol F type epoxy resin are all epoxy. It is characterized by comprising 5 to 40% by weight in the resin.

  The invention of claim 4 is characterized in that, in claim 1 or 2, the cationic polymerization initiator is a thermal cationic initiator, and the resin composition contains a liquid alicyclic epoxy resin. is there.

  The invention of claim 5 is characterized in that, in any of claims 1 to 3, the cationic polymerization initiator is a photocationic initiator, and the resin composition contains a liquid alicyclic epoxy resin. To do.

  The invention of claim 6 is characterized in that in any one of claims 1 to 5, the resin composition contains epoxidized polybutadiene having a hydroxyl group.

  An optical waveguide according to a seventh aspect of the present invention has a refractive index higher than that of the cladding layer 3 in the cladding layer 3 formed by curing the epoxy resin film 1 according to any one of the first to sixth aspects. The high core layer 4 is formed by curing the epoxy resin film 1 according to claim 3.

  An optical / electrical composite substrate according to an eighth aspect of the present invention comprises an optical circuit section 6 having the optical waveguide 2 according to the seventh aspect and an electric circuit section 8 having a metal conductive path 7 integrally. It is characterized by this.

  An optical communication module according to a ninth aspect of the present invention imparts flexibility to the optoelectric composite substrate 5 according to the eighth aspect, and exposes the core layer 4 on both end faces of the optoelectric composite substrate 5. The light-emitting element 21 is provided opposite to the core layer 4 exposed on the other end face, and the light-receiving element 22 is provided opposite to the core layer 4 exposed on the other end face.

  According to the epoxy resin film of the first aspect of the present invention, film characteristics, curability, and heat resistance suitable for manufacturing a multimode waveguide that can be used integrally with a printed wiring board can be realized. It can be processed in a temperature range below the processing temperature range in the manufacturing process. And the multimode optical waveguide manufactured based on this film can realize a sufficiently low waveguide loss. In addition, the opto-electric composite wiring board integrated with this waveguide does not deteriorate the waveguide loss even when solder reflow and heat shock tests are performed, and realizes heat resistance and high reliability that can withstand component mounting. Is something that can be done.

  According to invention of Claim 2, workability and a softness | flexibility as a film can be made into a favorable state, maintaining transparency.

  According to the invention of claim 3, when forming the core portion of the optical waveguide by using a photocation initiator, only the portion to be the core is irradiated with active energy rays such as ultraviolet rays and electron beams, It can be made difficult to dissolve in a developer, and by containing at least one of a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, the content of benzene rings having a high electron density increases, and the composition The cured product can have a high refractive index.

  According to the invention of claim 4, by using a thermal cation initiator, the film-like composition is melted in the thermosetting process to become a low viscosity, and can fill a step, In addition, by using a liquid alicyclic epoxy resin, the viscosity at the time of melting can be lowered and it becomes easy to fill a step, the transparency can be kept high, and the refractive index can be kept low. Is.

  According to the invention of claim 5, by using a photocationic initiator, the film-like composition is applied to the substrate, and then the entire surface is exposed to form an entirely flat clad layer in a short time. In addition, by using a liquid alicyclic epoxy resin, it is possible to reduce the viscosity at the time of melting, to easily fill the step, to maintain high transparency, and to further increase the refractive index. It can be kept low.

  According to the invention of claim 6, the epoxidized polybutadiene having a hydroxyl group has a chain transfer effect in a cationic curing system, can significantly increase the polymerization rate (curing rate), and has compatibility with the epoxy resin. It is good and can maintain transparency, and can make it difficult to deteriorate the hygroscopicity and heat resistance of the cured product.

  According to the optical waveguide according to claim 7 of the present invention, the epoxy resin film made of the resin composition for clad can take a dry process, is cured in a short time, has high transparency, and has high heat resistance. The epoxy resin film made of the resin composition for the core, which is a cured product, can take a dry process, and can form a waveguide with low loss by close exposure of the mask. The optical waveguide as a whole has low loss, high heat resistance, and excellent productivity.

  According to the optoelectric composite substrate according to claim 8 of the present invention, since it is highly compatible with the printed wiring board method, it is easy to manufacture, and surface mounting of electronic parts and optical parts is possible, and the optical waveguide has low loss. In addition, high reliability can be realized in the usage environment from mounting.

  According to the optical communication module according to claim 9 of the present invention, since the photoelectric composite substrate constituting the main part has flexibility, it can be bent at this part, and can be used for a notebook personal computer or the like. It is possible to greatly relieve the restrictions on assembly in the representative portable devices and devices, and to realize downsizing of the devices and devices incorporating such optical communication modules. is there.

  Embodiments of the present invention will be described below.

(Embodiment 1)
The epoxy resin film according to the present invention is obtained by forming a resin composition containing a specific epoxy resin A, a copolymer polymer B, and a cationic polymerization initiator into a film shape. Hereinafter, these contents will be described in order.

  In the present invention, the epoxy resin A is not particularly limited as long as it is obtained by adding 1,2-epoxy-4- (2-oxiranyl) cyclohexane to 2,2-bis (hydroxymethyl) -1-butanol. For example, what is represented by the following general formula (4) can be used.

  The epoxy resin A is a so-called alicyclic and highly transparent polyfunctional epoxy resin having a melting point of about 85 ° C., and is suitable for forming a film by casting a varnish on a base film and drying it. In addition, the heat resistance of the cured product can be increased. A preferable blending ratio of the epoxy resin A is 30 to 80% by weight in the total resin. If it is less than 30% by weight, the heat resistance after curing may be lowered, or the tackiness of the film may be deteriorated. On the other hand, if it exceeds 80% by weight, there is no problem of heat resistance, but the flexibility (softness) of the film deteriorates, and there is a possibility that problems such as cracks occur during handling. In addition, although the molecular weight of the epoxy resin A is not specifically limited, For example, it is about 2000-3000.

  In the present invention, the copolymer polymer B includes at least one compound selected from styrene, a compound represented by the following general formula (1), a compound represented by the following general formula (2), and the following general formula: What is obtained by copolymerizing the compound represented by (3) is used.

  The copolymer polymer B contains the compound represented by the general formula (3) as a structural unit, so that it has excellent curability as an alicyclic internal epoxy resin, and the cured product has excellent transparency. Therefore, the transparency can be maintained even under moisture absorption, and the moisture resistance reliability can be enhanced. The monomer used as the raw material of the copolymer polymer B is styrene, other than the compounds represented by the general formulas (1), (2) and (3), for example, various epoxies, as long as the object of the present invention is not impaired. Acrylate, divinylbenzene, etc. can be used together as appropriate. A preferable blending ratio of the copolymer polymer B is 5 to 50% by weight in the total resin.

  Moreover, since the compound represented by the general formulas (1) and (2) is a kind of cycloolefin compound, the refractive index of the cured product is about 1.50 for those containing these compounds as structural units. It is possible to make it a low level and to exhibit excellent transparency. The fact that the refractive index can be lowered in this way means that the refractive index can be reduced by a simple method such as using a copolymer with a monomer having an effect of increasing the refractive index such as an aromatic ring or using an epoxy resin together. There is an advantage that a high resin composition can be obtained, and the core and the clad constituting the optical waveguide can be easily formed.

  In addition, the copolymer polymer B obtained by copolymerizing styrene and the compound represented by the general formula (3) has excellent compatibility with the epoxy resin A, and thus has excellent transparency when varnish is dried. It is necessary to develop the film characteristics of the epoxy resin film after coating and drying the varnish, and the refractive index can be adjusted by the ratio of the styrene unit, and since it has an internal epoxy group, it can be easily incorporated into the curing system. The transparency after curing can be kept high.

In the present invention, the cationic polymerization initiator is not particularly limited as long as it generates Lewis acid or Bronsted acid by light, heat, electron beam or the like and does not impair transparency. Can be used. Specific examples include aryldiazonium salts having PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , SbCl ₆ ²⁻ , BF ₄ ⁻ , SnCl ₆ ⁻ , FeCl ₄ ⁻ , BiCl ₅ ^2−, etc. as anions. As anions, PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , SbCl ₆ ²⁻ , BF ₄ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , FSO ₃ ⁻ , F ₂ PO ₂ ⁻ , B (C ₆ F _{5) 4} ^- diaryliodonium salt having the like, triarylsulfonium salt, triarylselenonium salt, as an ^{_{anion, PF 6 -, AsF 6 -}} , SbF 6 - dialkyl phenacyl sulfonium salts with such as dialkyl -4-hydroxyphenylsulfonium salt and α-hydroxymethylbenzoin sulfonate ester And sulfonic acid esters such as N-hydroxyimide sulfonate, α-sulfonyloxyketone and β-sulfonyloxyketone, iron allene compounds, silanol-aluminum complexes, o-nitrobenzyl-triphenylsilyl ether, etc. It can be illustrated. A preferable blending ratio of the cationic polymerization initiator is 0.5 to 5% by weight in the total resin.

  Since the resin composition containing the above essential components is finally formed into a film, the varnish is dissolved in some solvent (for example, toluene, 2-butanone, propylene glycol monoethyl ether acetate (PGEA), etc.). Make it. A general method can be adopted for film formation. For example, as shown in FIG. 1, when the varnish 9 is coated and dried on the base film 10 (FIG. 1A) and the cover film 11 is adhered, the epoxy resin film 1 is completed (FIG. 1B). )). Various surfactants can be blended in order to improve the coatability in this processing process. Examples thereof include a leveling agent for improving wettability to the base film 10 and an antifoaming agent for preventing the generation of bubbles.

  Depending on the type of solvent, care must be taken because the solvent itself remaining in the epoxy resin after drying may impair the curability. Moreover, since the uneven | corrugated state of the surface may be transcribe | transferred to the surface of a core or a clad, it is preferable to use the base film 10 with few unevenness | corrugations.

  In addition, in the present invention, other resins as described below can be used in combination as long as the characteristics of the optical waveguide are not deteriorated.

  That is, the epoxy resin is not particularly limited as long as it has a plurality of epoxy groups in one molecule, and a commercially available liquid epoxy resin or solid epoxy resin can be appropriately used. Specific examples of the epoxy resin include alicyclic epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin having biphenyl skeleton, naphthalene ring-containing epoxy resin, dicyclopentadiene Dicyclopentadiene type epoxy resin having a skeleton, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, bromine-containing epoxy resin, aliphatic epoxy resin, triglycidyl isocyanurate, etc. From these, only one type or two or more types can be selected and used in combination.

  Any polymer that can be dissolved in the varnish can be used in combination. Specific examples include phenoxy resin, polyamide resin, and PPE resin. A butyral resin, which is a polymer but regarded as a rubber component, a polybutadiene resin with a functional group, and the like can be used in combination.

  In the present invention, an oxetane resin may be used in combination with the epoxy resin. Oxetane resin is a compound having a 4-membered ring consisting of 3 saturated carbon atoms and 1 oxygen atom, which has one more carbon than epoxy ring, and is supplied by Toagosei Co., Ltd. 3- (2-ethylhexyloxymethyl) oxetane (product name: “OXT-212”), 3-ethyl-3-hydroxymethyloxetane (product name: “OXT-101”) or 1,4-bis {[( 3-ethyl-3-oxetanyl) methoxy] methyl} benzene (product name: “OXT-121”), oxetanyl-silsesquioxane (product name: “OX-SQ”), and the like. When oxetane is used in combination with an epoxy resin, a highly transparent cured product can be obtained, and the good aspects of the epoxy resin curing start rate and the oxetane polymerization growth rate are manifested. Furthermore, an excellent composition can be obtained.

  When the cationic polymerization initiator is a type that initiates curing by light, a so-called sensitizer can be used in combination so that the initiator can be cured even with light having a wavelength longer than the wavelength of the light that generates the acid most efficiently. . As an example, benzophenone, acridine orange, perylene, anthracene, phenothiazine, 2,4-diethylthioxanthone and the like can be exemplified.

  In the cationic curing system, a chain transfer agent used for the purpose of increasing the polymerization rate and preventing unreacted epoxy resin from being left behind can be used in combination. In general, polyfunctional alcohols are used, and examples include ethylene glycol, butanediol, trimethylolpropane triol, pentaerythritol, polyvinyl alcohol, and the like. There is also a drawback that heat resistance is lowered.

  Moreover, it is preferable that Tg after finally baking (after-curing) the film which consists of a composition is 140 degreeC or more. When Tg is lower than 140 ° C., there is a possibility that problems may occur in the high temperature received in the element mounting process and the durability to the temperature cycle test when integrated with a printed wiring board and used in an electronic device. Absent. On the other hand, when Tg is high, there is no problem with respect to durability against temperature, but since it is a cured product of the epoxy resin composition, it generally does not exceed about 250 ° C.

(Embodiment 2)
The molecular weight of the copolymer polymer B containing the styrene and the compound represented by the general formula (3) used in the present invention as essential components is 4,000 to 40,000, and processing as a film while maintaining transparency This is particularly preferable because the properties and flexibility can be made good. When the molecular weight is less than 4000, the composition becomes brittle and the flexibility of the epoxy resin film after coating and drying may be impaired. On the other hand, when the molecular weight is larger than 40000, the solubility in the solvent is lowered, making it difficult to prepare the varnish, or the workability is lowered due to a skinning phenomenon on the varnish surface during coating. In addition, there is a tendency to increase light scattering, which is considered to be caused by micro-uniformity formed by the aggregation of the copolymer polymer B during the curing process, and deterioration of waveguide loss. It is not preferable because it may appear.

(Embodiment 3)
In the present invention, the cationic polymerization initiator is a photocationic initiator, and either one or both of the bisphenol A type epoxy resin and the bisphenol F type epoxy resin is 5 to 40% by weight in the total epoxy resin. % -Containing resin composition can be used.

  When trying to form the core portion of the optical waveguide, it is necessary to irradiate only the portion to be the core with active energy rays such as ultraviolet rays and electron beams to make it difficult to dissolve in the developer. By using a photocationic initiator, the above required characteristics can be realized.

  Further, since the core needs to have a higher refractive index than the clad portion, the content of the benzene ring having a high electron density is increased by containing at least one of the bisphenol A type epoxy resin and the bisphenol F type epoxy resin, A cured product of the composition can have a high refractive index. The bisphenol A type epoxy resin and bisphenol F type epoxy resin can be used from a liquid or crystalline monomer to a solid oligomer as required in terms of viscosity, film performance and developability. The content of either one or both of the bisphenol A type epoxy resin and the bisphenol F type epoxy resin is preferably 5 to 40% by weight in all the epoxy resins. When the content is less than 5% by weight, the effect of increasing the refractive index of the composition is small, and it may be difficult to perform the function as a core. Conversely, if the above content exceeds 40% by weight, the refractive index increases, but the heat resistance of the cured product decreases, and the heat resistance temperature of an FR4 grade printed wiring board generally used as a substrate for electronic equipment. (Tg) is lower, and there is a possibility that reliability in the use environment may be lowered.

(Embodiment 4)
Moreover, in this invention, the cationic polymerization initiator is a thermal cation initiator, and the resin composition containing a liquid alicyclic epoxy resin can be used.

  The clad portion of the optical waveguide needs to have a refractive index lower than that of the core. In general, it is not necessary to form only in a specific portion like the core, and the entire surface may be cured, particularly the core. When the core is covered with the clad after formation, it is also necessary to bury the stepped portion without any gap. By using the thermal cation initiator, the film-like composition is melted in the thermosetting process to have a low viscosity and can be filled with a step. And by using a liquid alicyclic epoxy resin, it is possible to reduce the viscosity at the time of melting and to easily fill a step, to maintain high transparency, and to maintain a low refractive index. Is.

  Here, the liquid alicyclic epoxy resin is an epoxy resin having no unsaturated bond in the molecular structure, and the epoxy group is an internal epoxy resin in the form of epoxidized cycloalkene, and the vinyl group is an epoxy. Either of the so-called external epoxy resins may be used. As the main skeleton, there are only hydrocarbons such as a hydrogenated bisphenol skeleton and those having a functional group such as an ester group in the molecule, either of which may be used. And the compounding quantity of a liquid alicyclic epoxy resin has preferable 5 to 30 weight% in all the resins. If the amount is less than 5% by weight, the effect of reducing the viscosity may be reduced. On the other hand, if it exceeds 30% by weight, the problem that the tackiness of the film deteriorates may become significant.

(Embodiment 5)
Moreover, in this invention, the cationic polymerization initiator can be a photocationic initiator, and the resin composition containing a liquid alicyclic epoxy resin can be used.

  The clad portion of the optical waveguide needs to have a refractive index lower than that of the core. In general, it is not necessary to form only in a specific portion like the core, and the entire surface may be cured, particularly the core. When forming the clad before formation, it is necessary to make it flat without a step. By using the photocationic initiator, the film-like composition is attached to the substrate and then exposed to the whole surface, and such a flat clad layer can be formed in a short time. The characteristics and blending amount of the liquid alicyclic resin are as described above.

(Embodiment 6)
Moreover, in this invention, you may mix | blend the epoxidized polybutadiene which further has a hydroxyl group with a resin composition.

  The epoxidized polybutadiene having a hydroxyl group used here is typified by CAS number 68441-49-6, and has a hydroxyl group in the molecular chain and a hydroxyl group at the molecular chain terminal. This is manufactured by Daicel Chemical Industries, Ltd. under the trademark “Epolide”, and illustrates the product number “PB3600” having a hydroxyl group in the molecule and at the molecular end, and the product number “PB4700” having a hydroxyl group in the molecule. Can do.

  The epoxidized polybutadiene having a hydroxyl group is liquid and has a chain transfer effect in a cationic curing system because the molecular chain easily moves and has a hydroxyl group, so that the polymerization rate (curing rate) can be remarkably increased. It is compatible with and can maintain transparency. In addition, the epoxidized polybutadiene having a hydroxyl group is an aliphatic non-glycidyl ether epoxy resin having a large molecular weight unlike the aforementioned polyfunctional alcohol as a chain transfer agent, and the reactivity of the epoxy group is the same as that of the alicyclic epoxy resin. Since it is about a level and is taken into the curing system, it has a feature that the hygroscopicity and heat resistance of the cured product are hardly deteriorated.

  The epoxidized polybutadiene having a hydroxyl group is preferably blended in the range of 1 to 30% by weight in the resin. If it is less than 1% by weight, the effect of increasing the polymerization rate may not be exhibited. On the other hand, if it exceeds 30% by weight, the heat resistance of the cured product may be lowered, or the tackiness of the film may be deteriorated. A more preferable range of the blending amount is 2 to 15% by weight.

  Moreover, when manufacturing a resin composition, it is preferable to mix and manufacture the epoxidized polybutadiene which has a hydroxyl group in the composition which mixed epoxy resin other than the epoxidized polybutadiene which has a hydroxyl group, and a cationic polymerization initiator beforehand. If it manufactures by this method, the obtained resin composition turns into a uniform hardened | cured material and can implement | achieve high Tg stably. The reason for this is presumed to be due to a slight difference in compatibility between the epoxy resin and the epoxidized polybutadiene having a hydroxyl group, but it is not clear. In this method, a method in which a cationic polymerization initiator is added to a mixture of epoxidized polybutadiene having a hydroxyl group and other epoxy resin, a phenomenon in which the cured product of the resulting composition becomes non-uniform or Tg significantly decreases. May occur, which is not preferable.

(Embodiment 7)
The optical waveguide according to the present invention can be formed as follows. First, the clad layer 3 is formed by curing the photocurable or thermosetting epoxy resin film 1 in the first to sixth embodiments. Next, a core layer 4 having a refractive index higher than that of the cladding layer 3 is formed inside the cladding layer 3 by curing the photocurable epoxy resin film 1 in the third embodiment. Then, the optical waveguide according to the present invention can be obtained.

  The epoxy resin film made of the resin composition for the clad is capable of taking a dry process, becomes a cured product having high transparency and high heat resistance by curing in a short time, and the resin composition for the core. The epoxy resin film made of can take a dry process, and can form a low-loss waveguide by close exposure of the mask. Therefore, the optical waveguide as a whole has low loss and high heat resistance, Productivity is also excellent. Further, the refractive index of the clad and the core is preferably about 0.5 to 3% larger than that of the clad. If the difference in refractive index is small, it is difficult to receive light from the light emitting element, and there is a possibility that loss at the light incident portion increases. On the other hand, if the refractive index difference is too large, the radiation angle of the light exiting the waveguide increases, making it difficult to apply all the light to the light receiving part of the light receiving element and increasing the loss. There is a risk that the pulse pattern of the above will deteriorate.

  To illustrate a specific method of forming the optical waveguide 2, as shown in FIG. 2, first, light for cladding is applied to some substrate 12 (for example, FR4 grade printed wiring board, glass, film, resin plate, metal plate, etc.). A curable or thermosetting epoxy resin film 1a is laminated, and the entire surface is cured (FIG. 2 (a)). Next, the base film 10 is peeled off (FIG. 2B), a photocurable epoxy resin film 1b for the core is laminated, a negative type film mask 13 on which a desired pattern is drawn is brought into close contact, and is exposed with UV14 or the like. After (FIG. 2 (c)), after-exposure after cure is performed by heating for several minutes to several tens of minutes. Thereafter, the base film 10 is peeled off, and development is performed from room temperature to warm using a solvent or an aqueous flux remover (FIG. 2D). Then, after cleaning and drying, a clad epoxy resin film 1a is laminated and the entire surface is cured to complete the optical waveguide 2 (FIGS. 2E and 2F).

  When the device that inputs light into the optical waveguide is a surface emitting laser (VCSEL), or the light receiving device that receives light from the optical waveguide is a surface mount photodiode (PD), the above optical waveguide formation process is performed. Alternatively, after the optical waveguide is completed, it is necessary to provide a deflector that bends the light of the optical waveguide by 90 degrees. It is possible to bend the optical axis by 90 degrees by a micro mirror inclined by 45 degrees, or to deflect the optical axis by a grating formed by femtosecond laser or interference exposure.

(Embodiment 8)
The optoelectric composite substrate according to the present invention can be formed by integrally including the optical circuit portion 6 including the optical waveguide 2 and the electric circuit portion 8 including the metal conductive path 7 in the seventh embodiment.

  The optical waveguide 2 may be sequentially formed in the order of clad-core-cladding on the surface of a general printed wiring board or a flexible printed wiring board in which a metal conductive path 7 such as an electric circuit is embedded, or the optical waveguide 2 is light-guided on a temporary substrate. The waveguide 2 may be formed and adhered and transferred to a printed wiring board (see Example 16 described later). Then, a metal conductive path 7 such as a conductor circuit is disposed on the uppermost layer, and electrode pads and in-plane wiring for mounting electronic components for surface mounting, as well as via holes (Via Hole) for electrical conduction with the lower layer are provided. ) Or through holes may be formed.

  The optoelectric composite substrate obtained in this way is easy to manufacture because of its high compatibility with the printed wiring board construction method, enables surface mounting of electronic and optical components, has low loss as an optical waveguide, and is mounted Therefore, high reliability can be realized in the use environment.

(Embodiment 9)
FIG. 6 shows an example of the optical communication module A according to the present invention, and the optical communication module A can be manufactured as follows.

  First, flexibility is imparted to the photoelectric composite substrate 5 constituting the main part of the optical communication module A. If both the electric circuit portion 8 and the optical circuit portion 6 constituting the optoelectric composite substrate 5 are formed with flexibility, the optoelectric composite substrate 5 can be provided with flexibility. Specifically, in forming the electric circuit portion 8 including the metal conductive path 7, flexibility such as a polymer film such as polyimide or polyester, a glass cloth or a composite material composed of various nonwoven fabrics and a resin is used. If the metal conductive path 7 is formed on the substrate 12 having the electric circuit portion 8, the electric circuit portion 8 can be formed flexibly. On the other hand, when the optical circuit portion 6 including the optical waveguide 2 is formed, the optical circuit portion 6 can be formed flexibly by adjusting the Tg of the epoxy resin film 1 to about 70 to 140 ° C. If the Tg is higher than 140 ° C., the flexibility of the optical circuit unit 6 may be reduced or the entire warpage may be increased. If the Tg is lower than 70 ° C., the optical waveguide 2 is deformed by an external force and guided. Loss may get worse.

  Next, the core layer 4 is exposed on both end faces of the photoelectric composite substrate 5. The core layer 4 can be exposed, for example, by cutting the photoelectric composite substrate 5 in the stacking direction. As shown in FIG. 6, the light emitting element 21 is provided to face the core layer 4 exposed at one end face, and the light receiving element 22 is provided to face the core layer 4 exposed at the other end face. 6, the optical communication module A is mounted by fitting a U-shaped connector 24 having a light emitting element 21 or a light receiving element 22 and an external connection terminal 23 into an end of the photoelectric composite substrate 5. I try to manufacture. Although the external connection terminal 23 is connected to the metal conductive path 7, it may be connected to the light emitting element 21 or the light receiving element 22.

  In the optical communication module A manufactured as described above, since the optoelectric composite substrate 5 constituting the main part has flexibility, it can be bent at this part, and the notebook personal computer can be bent. It is possible to greatly ease the restrictions on the assembly in portable devices and devices represented by computers and the like, and to realize downsizing of the devices and devices incorporating such an optical communication module A. It is something that can be done.

  Hereinafter, the present invention will be specifically described by way of examples.

  The raw materials used to produce the epoxy resin film are as follows.

  As an epoxy resin A obtained by adding 1,2-epoxy-4- (2-oxiranyl) cyclohexane to 2,2-bis (hydroxymethyl) -1-butanol, “EHPE3150” which is an alicyclic epoxy resin ( Daicel Chemical Industries, Ltd., solid at room temperature) was used.

  As the liquid alicyclic epoxy resin, “Celoxide 2021P” (manufactured by Daicel Chemical Industries, Ltd., liquid at room temperature, abbreviated as “CEL2021P”) was used.

  As the bisphenol A type epoxy resin, “Epiclon 840S” (Dainippon Ink Industries, Ltd., liquid at room temperature) and “Epicron 1050” (Dainippon Ink Industries, Ltd., solid at room temperature) were used.

  As the bisphenol F type epoxy resin, “Epicoat 4007P” (manufactured by Japan Epoxy Resin Co., Ltd., solid at room temperature) was used.

  As copolymer polymer B of the compound represented by the above general formula (1) (3), “GX8643P” (Daiichi Kogyo Seiyaku Co., Ltd., epoxidized cyclohexyl acrylate and cyclohexyl acrylate having a molar ratio of 1: 1) Polymer, molecular weight 6000), “GX8643R” (Daiichi Kogyo Seiyaku Co., Ltd., copolymer of epoxidized cyclohexyl acrylate and cyclohexyl acrylate, molar ratio 1: 5, molecular weight 6000) was used. Moreover, as copolymer polymer B of the compound represented by the general formulas (2) and (3), “GX8643Q” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., molar ratio of epoxidized cyclohexyl acrylate, isobornyl acrylate and styrene is 1). 1: 2 copolymer, molecular weight 7000). Moreover, as copolymer polymer B of the compound represented by styrene and the general formula (3), “GX8643C” (Daiichi Kogyo Seiyaku Co., Ltd., copolymer of styrene and epoxidized cyclohexyl methacrylate with a molar ratio of 1: 1). Unit, molecular weight 160000), “GX8643E” (Daiichi Kogyo Seiyaku Co., Ltd., copolymer of styrene and epoxidized cyclohexyl methacrylate, molar ratio 1: 1, molecular weight 33000), “GX8643J” (Daiichi Kogyo Seiyaku Co., Ltd.) , A copolymer of styrene and epoxidized cyclohexyl methacrylate in a molar ratio of 1: 1, molecular weight 5000), “GX8643K” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., molar ratio of styrene, epoxidized cyclohexyl methacrylate and dicyclohexyl fumarate 1: 2 1 copolymer, molecular weight 5000)

  As the epoxidized polybutadiene having a hydroxyl group, “PB3600” (manufactured by Daicel Chemical Industries, Ltd.) was used.

  As the cationic polymerization initiator, “SP-170” (manufactured by Asahi Denka Kogyo Co., Ltd.) which is a UV cationic curing initiator is used, and “SI-160L” (manufactured by Sanshin Chemical Industry Co., Ltd.) which is a thermal cationic curing initiator. )It was used.

  Industrial solvents were used for the solvents toluene, 2-butanone, and propylene glycol monoethyl ether acetate (PGEA).

(Examples 1-14, Comparative Examples 1-4)
The resin compositions of Examples 1 to 14 and Comparative Examples 1 to 4 were prepared by mixing raw materials shown in the following [Table 1] and [Table 2]. Resin and solvent other than “PB3600” and the cationic curing initiator were weighed, and this was heated to 80 ° C. with stirring and mixed, then cooled to room temperature, and the cationic curing initiator was added and mixed with stirring. When “PB3600” was used, it was added at the end and further stirred and mixed. The mixture was filtered through a membrane filter having a pore size of 1 μm and degassed under reduced pressure to prepare a varnish.

  Evaluation of the resin composition obtained as a varnish as described above as an epoxy resin film was performed as follows.

1. Refractive Index For Examples 1 to 7 and Comparative Examples 1 and 2, the above varnish was applied to a smooth surface of a high refractive index glass (refractive index 1.6) having a size of 5 mm and a thickness of 20 mm × 10 mm. Drying was performed for 30 minutes and then at 120 ° C. for 30 minutes. For Examples 1 to 3 and 5 to 6 and Comparative Examples 1 and 2 that are photo-curing blended with "SP170", UV light from an ultra-high pressure mercury lamp is exposed at a light amount of ² J / cm ² and cured. And heat treatment at 160 ° C. for 30 minutes. On the other hand, about the thermosetting Examples 4 and 7 which mix | blended "SI-160L", the heat processing for 1 hour was performed at 160 degreeC. The resin surface was polished to make it smooth, and the refractive index was measured with a refractive index measuring device manufactured by Atago Co., Ltd.

Moreover, about Examples 8-14 and Comparative Examples 3-4, said varnish was apply | coated to the smooth surface of the high refractive index glass (refractive index 1.6) of the magnitude | size of 5 mm thickness 20mm * 10mm, 80 degreeC, Drying was performed for 5 minutes and then at 120 ° C. for 30 minutes. For Examples 8 to 11, 13 to 14 and Comparative Examples 3 to 4 which are photo-curing blended with “SP170”, UV light from an ultrahigh pressure mercury lamp is exposed at a light amount of ² J / cm ² and cured. And heat treatment at 160 ° C. for 30 minutes. On the other hand, about the thermosetting Example 12 which mix | blended "SI-160L", the heat processing for 1 hour was performed at 160 degreeC. The resin surface was polished to make it smooth, and the refractive index was measured with a refractive index measuring device manufactured by Atago Co., Ltd.

2. Varnishing The varnish was placed in an 85 mmφ petri dish and swung to observe the state of the varnish surface. If the surface of the varnish is skinned, it is not preferable because it is difficult to produce a uniform coating film during film coating. The case where skinning occurred was defined as “present”, and the case where skinning did not occur was defined as “none”.

  For subsequent film property evaluation, film production was performed according to the following procedure.

  The varnish was coated on a PET film having a thickness of 25 μm with a bar coater, followed by primary drying at 80 ° C. for 5 minutes and then secondary drying at 120 ° C. for 5 minutes. The thickness of the coating film was 50 μm.

3. Film adhesion The touch of the epoxy resin film after drying was evaluated. When the finger was strongly pressed, it was evaluated whether there was no adhesion at all ("None"), only the fingerprint was attached to the resin ("Fingerprint"), or whether the resin adhered to the finger ("Adhesion"). Those with resin attached to the finger are not preferable because they cannot withstand industrial use.

4). Film Flexibility The dried epoxy resin film was bent, and the appearance of the coated / dried resin layer was observed. “X” indicates that the resin layer has cracks, “O” indicates that there is no crack, but the resin layer and the PET film peel slightly at the end of the film, and “◎” indicates that there is no change. .

5. Curability (1) Resistance to development The curability of Examples 1 to 3, 5 to 6, 8 to 11, 13 to 14 and Comparative Examples 1 to 4, which are photocured with “SP170”, is a mask by UV light. Development was performed after exposure, and the development resistance was evaluated. Specifically, a 1.2 mm-thick FR4 copper-clad double-sided copper-etched plate is laminated with a film made of the resin composition produced by the bar coater, and a 40 μm wide linear pattern is formed on the base film side. A negative film mask on which is drawn was adhered, and the film was exposed with an ultrahigh pressure mercury lamp at a light intensity of 1500 mJ / cm ² . Then, it heat-processed at 100 degreeC for 10 minute (s), peeled off the cover film, and developed with toluene for 15 second with the ultrasonic cleaner. The cured resin pattern of the resin composition thus obtained was observed with a microscope, and there was no damage such as melting, chipping, peeling, or meandering of the pattern, and the spread of the bottom (surface joined with FR4) “◎” indicates that there is no spread, “○” indicates that there is no damage such as melting, chipping, peeling, or meandering of the pattern, and “△” indicates that the pattern is partially melted or chipped. ”, And those with peeling or meandering were evaluated as“ x ”. In this evaluation, as the epoxy resin reaction sufficiently progresses and the curability is better, the bottom of the pattern cross section does not spread (better rectangularity) and is less susceptible to damage by the solvent during development. This is a substitute evaluation.

(2) Gel time About Example 4, 7, 12 which is thermosetting which mix | blended "SI-160L", the gel time of the varnish was measured at 170 degreeC. The varnish was placed on a hot plate at 170 ° C. in an amount of 0.3 to 0.5 g, the time was measured after the boiling of the solvent subsided, and the time until gelation was measured while stirring with a Teflon (registered trademark) bar. A shorter gel time means better curability.

6). Tg
The film produced by the bar coater was laminated on the smooth surface of a 35 μm thick copper foil. For Examples 1-3, 5-6, 8-11, 13-14, and Comparative Examples 1-4, which are photo-curing blended with “SP170”, the UV light of the ultra-high pressure mercury lamp is ² J / cm ² . Then, the base film was peeled off and subjected to heat treatment at 160 ° C. for 1 hour. On the other hand, about Example 4, 7, 12 which is thermosetting which mix | blended "SI-160L", 160 degreeC and the heat processing for 1 hour were performed, and the base film was peeled.

  The copper foil with the resin film-like cured product obtained as described above was punched into a 7 mm wide and 3 cm long rectangle, and the copper foil was peeled off to obtain a cured resin film. About this, Tg of tan-delta peak temperature was measured with Seiko Denshi Kogyo's viscoelasticity spectrometer "DMS200".

  As seen in [Table 1] above, Examples 1-7 were prepared by adding 1,2-epoxy-4- (2-oxiranyl) cyclohexane to 2,2-bis (hydroxymethyl) -1-butanol. A film comprising a resin composition containing the obtained epoxy resin A, a copolymer polymer B obtained by copolymerizing styrene and a compound represented by the above general formula (3), and a cationic polymerization initiator. Therefore, it can be seen that the heat resistance is high and the film flexibility is superior to that of Comparative Example 1.

  In Examples 2 to 7, the molecular weight of copolymer polymer B obtained by copolymerizing styrene and the compound represented by the general formula (3) is 4000 to 40000, as compared with Example 1. It can be seen that there is no varnishing and it is easy to form a uniform coating.

  Example 3 contains 5 to 40% by weight of bisphenol A type epoxy resin and bisphenol F type epoxy resin in the total epoxy resin, and further contains a photocationic initiator, compared with Examples 1 and 2 and Comparative Example 2. It can be seen that it is photocurable, has excellent film properties, has high heat resistance of the cured product, has a high refractive index, and is suitable for forming the core of an optical waveguide.

  Since Example 4 contains a thermal cation initiator and a liquid alicyclic epoxy resin as compared with Examples 1 and 2, it can be seen that it has excellent film properties, can be thermally cured, and can lower the refractive index of the cured product. .

  Since Example 5 contains a photocationic initiator and a liquid alicyclic epoxy resin as compared with Examples 1-2, it can be seen that the film properties are excellent, photocuring is possible, and the refractive index of the cured product can be lowered. .

  Since Example 6 contains the epoxidized polybutadiene which has a hydroxyl group compared with Examples 1-4, it turns out that it is excellent in curability from solvent resistance being high.

  Since Example 7 contains the epoxidized polybutadiene which has a hydroxyl group compared with Example 4, it turns out that gel time is short and it is excellent in sclerosis | hardenability.

  Moreover, as seen in the above [Table 2], in Examples 8 to 14, 1,2-epoxy-4- (2-oxiranyl) cyclohexane was added to 2,2-bis (hydroxymethyl) -1-butanol. Containing a copolymer polymer B obtained by copolymerizing the epoxy resin A obtained by styrene, a compound represented by the above general formulas (1), (2) and (3), and a cationic polymerization initiator Since it is a film made of a resin composition, it can be seen that it is excellent in curability.

  Since Examples 11, 12, and 14 contain the epoxidized polybutadiene which has a hydroxyl group, it turns out that it is especially excellent in sclerosis | hardenability.

(Example 15)
A film 1a having a resin thickness of 40 μm prepared by the varnish of Example 5 was vacuum-treated on a 5 cm × 15 cm plate obtained by etching away the copper foil of the 1.0 mm thick FR4 double-sided copper clad laminate 15. Laminate and harden the entire surface over the base film 10 with an ultra high pressure mercury lamp with an energy of 2000 mJ / cm ² (FIG. 2 (a)), and then perform post-curing at 160 ° C. for 1 hour. The lower clad 3a was formed by peeling (FIG. 2 (b)).

On top of this, the film 1b having a resin thickness of 40 μm prepared with the varnish of Example 3 according to the above-described film manufacturing procedure is vacuum-laminated, and a negative film mask 13 having a slit of 40 μm width and 14 cm length is formed over the base film 10. It is made to adhere and cured with an energy of 2000 mJ / cm ² with a light source of an ultra high pressure mercury lamp (FIG. 2C), after heat treatment at 120 ° C. for 5 minutes, the base film 10 is peeled off and developed with toluene. A 40 μm square 14 cm long core was formed (FIG. 2D). After that, after laminating the film 1a having a resin thickness of 80 μm prepared with the varnish of Example 7 according to the above-described film preparation procedure at 100 ° C. (FIG. 2 (e)), heat treatment was performed at 160 ° C. for 1 hour, The base film 10 was peeled off to form the upper clad 3b (FIG. 2 (f)). Both ends of the FR4 plate 15 are cut off and optically polished to obtain an optical waveguide having a length of 12 cm. Light from a light source of 850 nm is introduced into the core on one side of the optical waveguide 2 through an optical fiber having a core diameter of 10 μm. Was connected to a power meter through an optical fiber having a core diameter of 200 μm, and the waveguide loss of the optical waveguide 2 was evaluated. As a result, it was 0.10 dB / cm.

  Thus, in Example 15, the clad layer 3 (consisting of the upper clad 3b and the lower clad 3a) formed by curing the epoxy resin film 1a of Examples 5 and 7 is refracted more than the clad layer 3. Since the core layer 4 having a high rate is formed by curing the epoxy resin film 1b of Example 3, the wet and dry process that does not require the application of the liquid material can be performed, the productivity is high, and the optical waveguide 2 has a loss. Is very low and has excellent heat resistance.

(Example 16)
An optical waveguide layer is provided on a printed wiring board in which an 18 μm copper foil of a 1.6 mm thick FR4 double-sided copper clad laminate 15 of 4 cm × 14 cm is patterned, and a copper circuit for component mounting is provided on the surface of the optical waveguide layer. A substrate having the arranged configuration was produced. Specifically, the 0.6 mm-thick 6 cm × 16 cm aluminum plate 16 and the 35 μm-thick 6 cm × 16 cm smooth surface of the copper foil 17 are opposed to each other, and the outer peripheral portion is 3 mm wide through a hot-melt thermoplastic adhesive sheet. Then, the laminate was heat laminated to produce an aluminum-supported copper foil 17 (FIG. 3A). This is because the roughened surface of the copper foil 17 is on the outside, and a film with a resin thickness of 30 μm prepared with the varnish of Example 5 is vacuum laminated according to the above-described film preparation procedure, and over the base film 10. The entire surface was cured with an ultrahigh pressure mercury lamp at an energy of 2000 mJ / cm ² (FIG. 3B), and then post-curing was performed at 150 ° C. for 30 minutes, and the base film 10 was peeled off to form the clad 3a. This clad surface was treated with oxygen plasma at a high frequency output of 200 W for 1 minute. On this surface, a film 1b having a resin thickness of 40 μm prepared with the varnish of Example 6 according to the above-described film manufacturing procedure was vacuum-laminated, and 12 slits having a width of 16 μm and a width of 16 μm across the base film 10 were formed at a pitch of 250 μm (see FIG. 3) 4) Negative film masks 13 are arranged so that the slit direction is parallel to the longitudinal direction of the copper foil 17 and the waveguide slit is located in the center in the short direction, and they are brought into close contact with each other. Curing with an energy of 2000 mJ / cm ² with a mercury lamp light source (FIG. 3D), after heat treatment at 120 ° C. for 5 minutes, the base film 10 is peeled off and developed with toluene, and the length is 16 cm with a cross section of 40 μm square. The waveguide 2 was formed on the copper foil 17. Next, a film 1a having a resin thickness of 60 μm prepared with the varnish of Example 7 according to the above-described film manufacturing procedure was vacuum-laminated at 100 ° C. and then heat-treated at 150 ° C. for 30 minutes (FIG. 3 (f)). The film 10 was peeled off to form the clad 3b, and an aluminum-reinforced copper foil with a waveguide was produced (FIG. 3 (g)).

  Next, with a dicing machine equipped with a blade having a tip angle of 90 degrees of No. 5000 abrasive grains, a blade is inserted to a depth of 70 μm from the resin surface at a location 3 cm from both ends of the copper foil 17 perpendicular to the longitudinal direction of the core, The width of the copper foil 17 in the short direction was cut by 6 cm, and two mirror V-grooves were formed at an interval of 10 cm (FIG. 4A, which is a cross-sectional view taken along the line I-I in FIG. 3G).

  After smoothing the unevenness of the V-groove 18 surface by excimer laser, gold 20 is vacuum-deposited over only the V-groove 18 through the metal mask 19 (FIG. 4B), and a micromirror-formed aluminum reinforced waveguide The attached copper foil was produced (FIG.4 (c)).

  Next, one side of the 1.6 mm thick 6 cm × 16 cm FR4 double-sided plate 15 was etched off, and a 40 μm thick resin la produced in the varnish of Example 4 was vacuum laminated at 100 ° C. according to the above-mentioned film production procedure. Then, the resin surface of the copper foil with a waveguide of aluminum reinforcement formed with micromirrors was aligned with the surface from which the cover film was peeled off, and vacuum laminated at 140 ° C. (FIG. 5A). Thereafter, heat treatment was performed at 160 ° C. for 1 hour.

  Four sides of the substrate were cut off in 5 mm increments, and the aluminum plate 16 was removed to obtain a double-sided copper-clad optoelectric composite substrate (FIG. 5B). Etch off only 1 cm from the periphery of the copper foil on the waveguide side of the substrate so that the positions of the waveguide core and the micromirror can be confirmed. The position of the intersection of a certain waveguide core and mirror was calculated, and mask guide holes required for copper foil patterning were made at the four corners of the substrate based on the position. Thereafter, although not shown in the figure, the waveguide-side copper foil includes an electrode pad portion for mounting the VCSEL element array and the light receiving element array immediately above the light input / output portion, and a through-hole pad portion to the substrate back surface circuit. A circuit pattern connecting them is formed, and a copper hole on the side opposite to the waveguide is formed with a through-hole portion pad portion, a pad portion for an electrical connection terminal with an external circuit, and a circuit pattern connecting them with the through-hole. A photoelectric composite substrate was produced by forming a conductor on the part. From just above the light input / output part of this photoelectric composite substrate, silicone oil is interposed as a matching oil, light from a light source of 850 nm is introduced by an optical fiber having a core diameter of 10 μm, and directly above the light input / output part on the opposite side. Received silicone fiber as a matching oil, received light with an optical fiber having a core diameter of 200 μm, connected to a power meter, and evaluated the loss of the optical circuit. As a result, the total loss (insertion loss) of the micromirror input / 10 cm waveguide waveguide / micromirror output was 3.1 dB. The insertion loss after the solder reflow process was performed three times on this board under the lead-free solder reflow condition with a peak temperature of 265 ° C. was 3.3 dB. In addition, when another heat shock test was repeatedly performed on another substrate produced in the same manner in the liquid phase at −50 ° C., 5 minutes and 125 ° C. for 5 minutes, the insertion loss was 3.2 dB before treatment. There was only a slight increase to 3.6 dB.

  A mirror portion of another photoelectric composite substrate manufactured in the same manner is cut off and optical polishing is performed to obtain a waveguide having a length of 9 cm. Light from an 850 nm light source passes through an optical fiber having a core diameter of 10 μm on one side of the waveguide. Inserted into the core and connected to a power meter through an optical fiber having a core diameter of 200 μm from the opposite side, and the loss of the optical waveguide portion was evaluated. As a result, it was 0.11 dB / cm.

  As described above, in Example 16, the core layer 4 having a refractive index higher than that of the cladding layer 3 is formed in the epoxy layer of Example 6 inside the cladding layer 3 formed by curing the epoxy resin film 1a of Examples 5 and 7. Since the optical circuit portion 6 including the optical waveguide 2 formed by curing the resin film 1b and the electric circuit portion 8 including the metal conductive path 7 made of the copper foil 17 or the like are integrally provided, High compatibility, easy manufacturing, surface mounting of electronic components and optical components is possible, the optical waveguide 2 has low loss, and high reliability can be realized in the usage environment from mounting.

(Example 17)
A film 1a having a resin thickness of 40 μm prepared with the varnish of Example 8 was vacuum-treated on a 5 cm × 15 cm plate obtained by etching away the copper foil of the 1.0 mm thick FR4 double-sided copper clad laminate 15. Laminate and harden the entire surface over the base film 10 with an ultra high pressure mercury lamp with an energy of 2000 mJ / cm ² (FIG. 2 (a)), and then perform post-curing at 160 ° C. for 1 hour. The lower clad 3a was formed by peeling (FIG. 2 (b)).

On top of this, the film 1b having a resin thickness of 40 μm prepared by the varnish of Example 9 according to the above-described film manufacturing procedure was vacuum-laminated, and a negative film mask 13 having a slit of 40 μm width and 14 cm length was passed through the base film 10. It is made to adhere and cured with an energy of 2000 mJ / cm ² with a light source of an ultra high pressure mercury lamp (FIG. 2C), after heat treatment at 120 ° C. for 5 minutes, the base film 10 is peeled off and developed with toluene. A 40 μm square 14 cm long core was formed (FIG. 2D). After that, after laminating a film 1a having a resin thickness of 80 μm prepared with the varnish of Example 8 according to the above-described film preparation procedure at 100 ° C. (FIG. 2 (e)), heat treatment was performed at 160 ° C. for 1 hour, The base film 10 was peeled off to form the upper clad 3b (FIG. 2 (f)). Both ends of the FR4 plate 15 are cut off and optically polished to obtain an optical waveguide having a length of 12 cm. Light from a light source of 850 nm is introduced into the core on one side of the optical waveguide 2 through an optical fiber having a core diameter of 10 μm. Was connected to a power meter through an optical fiber having a core diameter of 200 μm, and the waveguide loss of the optical waveguide 2 was evaluated. As a result, it was 0.10 dB / cm.

  Thus, Example 17 has a refractive index higher than that of the cladding layer 3 in the cladding layer 3 (consisting of the upper cladding 3b and the lower cladding 3a) formed by curing the epoxy resin film 1a of Example 8. Since the high core layer 4 is formed by curing the epoxy resin film 1b of Example 9, the wet and dry process that does not require application of a liquid material can be performed, the productivity is high, and the optical waveguide 2 has a very high loss. The heat resistance is also low.

(Example 18)
An optical waveguide layer is provided on a printed wiring board in which an 18 μm copper foil of a 1.6 mm thick FR4 double-sided copper clad laminate 15 of 4 cm × 14 cm is patterned, and a copper circuit for component mounting is provided on the surface of the optical waveguide layer. A substrate having the arranged configuration was produced. Specifically, the 0.6 mm-thick 6 cm × 16 cm aluminum plate 16 and the 35 μm-thick 6 cm × 16 cm smooth surface of the copper foil 17 are opposed to each other, and the outer peripheral portion is 3 mm wide through a hot-melt thermoplastic adhesive sheet. Then, the laminate was heat laminated to produce an aluminum-supported copper foil 17 (FIG. 3A). This is because the roughened surface of the copper foil 17 is on the outside, and a film with a resin thickness of 30 μm prepared with the varnish of Example 8 according to the above-described film manufacturing procedure is vacuum laminated, and over the base film 10. The entire surface was cured with an ultrahigh pressure mercury lamp at an energy of 2000 mJ / cm ² (FIG. 3B), and then post-curing was performed at 150 ° C. for 30 minutes, and the base film 10 was peeled off to form the clad 3a. This clad surface was treated with oxygen plasma at a high frequency output of 200 W for 1 minute. On this surface, the film 1b having a resin thickness of 40 μm prepared with the varnish of Example 13 was vacuum-laminated in accordance with the above-described film manufacturing procedure, and 12 slits having a width of 16 μm and a width of 16 μm across the base film 10 were formed at a pitch of 250 μm (see FIG. 3) 4) Negative film masks 13 are arranged so that the slit direction is parallel to the longitudinal direction of the copper foil 17 and the waveguide slit is located in the center in the short direction, and they are brought into close contact with each other. Curing with an energy of 2000 mJ / cm ² with a mercury lamp light source (FIG. 3D), after heat treatment at 120 ° C. for 5 minutes, the base film 10 is peeled off and developed with toluene, and the length is 16 cm with a cross section of 40 μm square. The waveguide 2 was formed on the copper foil 17. Next, a film 1a having a resin thickness of 60 μm prepared with the varnish of Example 8 was vacuum laminated at 100 ° C. according to the above-described film manufacturing procedure, and then heat-treated at 150 ° C. for 30 minutes (FIG. 3F). The film 10 was peeled off to form the clad 3b, and an aluminum-reinforced copper foil with a waveguide was produced (FIG. 3 (g)).

  Next, with a dicing machine equipped with a blade having a tip angle of 90 degrees of No. 5000 abrasive grains, a blade is inserted to a depth of 70 μm from the resin surface at a location 3 cm from both ends of the copper foil 17 perpendicular to the longitudinal direction of the core, The width of the copper foil 17 in the short direction was cut by 6 cm, and two mirror V-grooves were formed at an interval of 10 cm (FIG. 4A, which is a cross-sectional view taken along the line I-I in FIG. 3G).

  After smoothing the unevenness of the V-groove 18 surface by excimer laser, gold 20 is vacuum-deposited over only the V-groove 18 through the metal mask 19 (FIG. 4B), and a micromirror-formed aluminum reinforced waveguide The attached copper foil was produced (FIG.4 (c)).

  Next, one side of the 1.6 mm thick 6 cm × 16 cm FR4 double-sided plate 15 was etched off, and a 40 μm-thick resin film 1a prepared with the varnish of Example 12 was vacuum laminated at 100 ° C. according to the above-described film manufacturing procedure. Then, the resin surface of the copper foil with a waveguide of aluminum reinforcement formed with micromirrors was aligned with the surface from which the cover film was peeled off, and vacuum laminated at 140 ° C. (FIG. 5A). Thereafter, heat treatment was performed at 160 ° C. for 1 hour.

  Four sides of the substrate were cut off in 5 mm increments, and the aluminum plate 16 was removed to obtain a double-sided copper-clad optoelectric composite substrate (FIG. 5B). Etch off only 1 cm from the periphery of the copper foil on the waveguide side of the substrate so that the positions of the waveguide core and the micromirror can be confirmed. The position of the intersection of a certain waveguide core and mirror was calculated, and mask guide holes required for copper foil patterning were made at the four corners of the substrate based on the position. Thereafter, although not shown in the figure, the waveguide-side copper foil includes an electrode pad portion for mounting the VCSEL element array and the light receiving element array immediately above the light input / output portion, and a through-hole pad portion to the substrate back surface circuit. A circuit pattern connecting them is formed, and a copper hole on the side opposite to the waveguide is formed with a through-hole portion pad portion, a pad portion for an electrical connection terminal with an external circuit, and a circuit pattern connecting them with the through-hole. A photoelectric composite substrate was produced by forming a conductor on the part. From just above the light input / output part of this photoelectric composite substrate, silicone oil is interposed as a matching oil, light from a light source of 850 nm is introduced by an optical fiber having a core diameter of 10 μm, and directly above the light input / output part on the opposite side. Received silicone fiber as a matching oil, received light with an optical fiber having a core diameter of 200 μm, connected to a power meter, and evaluated the loss of the optical circuit. As a result, the total loss (insertion loss) resulting in a micromirror input · 10 cm waveguide waveguide · micromirror output was 3.3 dB. The insertion loss after the solder reflow process was performed three times on this substrate under the lead-free solder reflow condition with a peak temperature of 265 ° C. was 3.5 dB. In addition, when another heat shock test was repeatedly performed on another substrate produced in the same manner in the liquid phase at −50 ° C., 5 minutes and 125 ° C. for 5 minutes, the insertion loss was 3.1 dB before treatment. There was only a slight increase of 3.5 dB.

  A mirror portion of another photoelectric composite substrate manufactured in the same manner is cut off and optical polishing is performed to obtain a waveguide having a length of 9 cm. Light from an 850 nm light source passes through an optical fiber having a core diameter of 10 μm on one side of the waveguide. Inserted into the core and connected to a power meter through an optical fiber having a core diameter of 200 μm from the opposite side, and the loss of the optical waveguide portion was evaluated. As a result, it was 0.13 dB / cm.

  Thus, in Example 18, the core layer 4 having a refractive index higher than that of the cladding layer 3 was formed in the cladding layer 3 formed by curing the epoxy resin film 1a of Example 8. Since the optical circuit portion 6 including the optical waveguide 2 formed by curing 1b and the electric circuit portion 8 including the metal conductive path 7 made of the copper foil 17 or the like are integrally provided, the compatibility with the printed wiring board method It is easy to manufacture, can be mounted on the surface of electronic parts and optical parts, has a low loss as the optical waveguide 2, and can realize high reliability in the usage environment from mounting.

(Example 19)
The following was manufactured as a photoelectric composite substrate with flexibility. That is, a substrate having a structure in which an optical waveguide is provided on a flexible printed wiring board in which a 12 μm copper foil of a 25 μm thick polyimide copper-clad substrate of 1 cm × 8 cm is patterned was manufactured.

Specifically, a polyimide substrate having a polyimide thickness of 25 μm on which a 12 μm thick copper circuit having a line width of 100 μm and an interval of 150 μm was formed was cut into 10 cm □ so that the copper pattern was parallel to one side after cutting. This copper circuit surface was affixed to a 10 cm square glass plate with Riva Alpha (manufactured by Nitto Denko Corporation) as a heat release sheet. Then, the film having a thickness of 20 μm prepared with the varnish of Example 10 was vacuum laminated according to the above-described film preparation procedure, and the entire surface was cured with an ultrahigh pressure mercury lamp with an energy of 2000 mJ / cm ² through the base film. After curing at 150 ° C. for 30 minutes, the base film was peeled off to form a clad. This clad surface was treated with oxygen plasma at a high frequency output of 200 W for 1 minute. On this surface, the film prepared with the varnish of Example 14 was vacuum-laminated according to the above-described film manufacturing procedure, and a negative film mask with 40 μm wide slits arranged on the entire surface with a 250 μm pitch over the base film was placed in the slit direction and copper. Arrange the foils in parallel so that the foil longitudinal direction is parallel, and let them harden with an energy of 2000 mJ / cm ² with a light source of an ultrahigh pressure mercury lamp. After heat treatment at 120 ° C. for 5 minutes, peel off the base film to toluene. Then, a 16 cm long core having a cross section of 40 μm square was formed, and a waveguide was formed on the copper foil. Next, a film having a resin thickness of 60 μm prepared with the varnish of Example 10 was vacuum-laminated at 100 ° C. according to the above-described film manufacturing procedure, and the entire surface was passed through the base film with an energy of 2000 mJ / cm ² with an ultrahigh pressure mercury lamp. After curing, post-curing was performed at 150 ° C. for 30 minutes. Next, heat treatment was performed at 170 ° C. for 30 minutes to peel off Ribaalpha and the glass plate from the polyimide substrate, peeled off the base film, and manufactured a flexible optical circuit board including an electric circuit integrated with a waveguide.

  This flexible optical circuit board was affixed to a dicing tape and fixed, and was cut with a dicing machine so that individual pieces having dimensions of 8 cm in the longitudinal direction of the core and 1 cm in the direction perpendicular to the core were obtained. Abrasive grains of No. 3000 were used. A substrate having a structure in which an optical waveguide is provided on a flexible printed wiring board in which a 12 μm copper foil of a 25 μm thick polyimide copper-clad substrate of 1 cm × 8 cm is patterned by peeling an individual piece from a dicing tape (providing flexibility) A photoelectric composite substrate) was obtained.

  The optical characteristics of this photoelectric composite substrate were evaluated as follows. Light from an 850 nm light source passes through an optical fiber with a core diameter of 10 μm and silicone oil intervenes as a matching oil and enters the core cross section on one side of the waveguide. From the opposite core cross section, silicone oil intervenes as a matching oil and core diameter The waveguide loss of the optical waveguide was evaluated by connecting to a power meter through a 200 μm optical fiber. As a result, it was 0.16 dB / cm. Similarly, the waveguide loss of the optical waveguide was evaluated in a state where the central portion of the flexible photoelectric composite substrate was bent to a radius of 6 mm. As a result, it was 0.18 dB / cm. Further, even if the central portion of the flexible photoelectric composite substrate was bent with a radius of 1 mm and then extended, no cracks or bending marks were left.

  As described above, the above-described optoelectric composite substrate can realize a very low waveguide loss and has flexibility, so that it can be suitably used for optical communication applications that are bent and used in a narrow device. It is something that can be done.

(Example 20)
Using the flexible photoelectric composite substrate, as shown in FIG. 6, the core layer 4 is exposed on both end faces of the photoelectric composite substrate 5, and light is emitted facing the core layer 4 exposed on one end face. The optical communication module A was manufactured by providing the element 21 and providing the light receiving element 22 so as to face the core layer 4 exposed on the other end face. The communication light emitted from the light emitting element 21 is guided to the light receiving element 22 through the core layer 4 of the flexible photoelectric composite substrate 5, and optical communication can be performed between the two elements.

  Specifically, this communication module A has a circuit portion (not shown) having a light emitting / receiving function at both ends, the light emitting portion is composed of a VCSEL having a wavelength of 850 nm and its driving device, and the light receiving circuit is a photodiode and It consists of a signal amplification device and a waveform shaping device. Then, an electrical signal is converted into an optical signal in the circuit portion of the light emitting portion, and the optical signal is incident on the core layer 4 of the flexible photoelectric composite substrate 5. It can be received by a light receiving circuit composed of an amplifier circuit, converted back to an electric signal, amplified and transmitted.

  In addition, since the flexible photoelectric composite substrate 5 is also formed with a copper circuit wiring (metal conductive path 7), the power source and the ground for driving the electrical circuit of the communication module A are on the back surface of the optical transmission portion. Wiring is formed in parallel with the optical waveguide 2. This has the effect of stabilizing the power supply ground potential of the circuit portions at both ends, and at the same time as transmitting a signal with light, an electric signal can be transmitted if necessary.

  Then, an eye pattern signal of 2.5 Gbps generated by a pulse generator is sent to the input part (not shown) of the communication module A, and after the electro-optical conversion by the light emitting circuit, the light transmitted through the core layer 4 of the optical waveguide 2 is transmitted. As a result of reverse conversion with a light receiving circuit and observing the waveform shape of the eye pattern with a sampling oscilloscope, a good transmission state was confirmed.

An example of the manufacturing process of the epoxy resin film which concerns on this invention is shown, (a) (b) is sectional drawing. An example of the formation process of the optical waveguide which concerns on this invention is shown, (a) thru | or (f) is sectional drawing. The other example of the formation process of the optical waveguide which concerns on this invention is shown, (a) thru | or (g) is sectional drawing. (A) thru | or (c) is the II sectional view taken on the line of FIG.3 (g). An example of the manufacturing process of the photoelectric composite board | substrate which concerns on this invention is shown, (a) (b) is sectional drawing. An example of the optical communication module which concerns on this invention is shown, and it is a fragmentary sectional view.

Explanation of symbols

A optical communication module 1 epoxy resin film 2 optical waveguide 3 clad layer 4 core layer 5 optoelectric composite substrate 6 optical circuit part 7 metal conductive path 8 electric circuit part 21 light emitting element 22 light receiving element

Claims (9)

Epoxy resin A obtained by adding 1,2-epoxy-4- (2-oxiranyl) cyclohexane to 2,2-bis (hydroxymethyl) -1-butanol, styrene, represented by the following general formula (1) A copolymer polymer B obtained by copolymerizing at least one compound selected from the compounds represented by the following general formula (2) and a compound represented by the following general formula (3), and cationic polymerization: An epoxy resin film comprising a resin composition containing an initiator and formed into a film.

  The copolymer polymer B is obtained by copolymerizing styrene and a compound represented by the above general formula (3), and the molecular weight of the copolymer polymer B is 4000 to 40000 The epoxy resin film according to claim 1.   The cationic polymerization initiator is a photocationic initiator, and contains one or both of bisphenol A type epoxy resin and bisphenol F type epoxy resin in an amount of 5 to 40% by weight in the total epoxy resin. The epoxy resin film according to claim 1 or 2, characterized in that:   The epoxy resin film according to claim 1 or 2, wherein the cationic polymerization initiator is a thermal cationic initiator, and the resin composition contains a liquid alicyclic epoxy resin.   The epoxy resin film according to any one of claims 1 to 3, wherein the cationic polymerization initiator is a photocationic initiator, and the resin composition contains a liquid alicyclic epoxy resin.   The epoxy resin film according to any one of claims 1 to 5, wherein the resin composition contains an epoxidized polybutadiene having a hydroxyl group.   A core layer having a refractive index higher than that of the cladding layer is cured inside the cladding layer formed by curing the epoxy resin film according to any one of claims 1 to 6. An optical waveguide characterized by being formed.   An optical / electrical composite substrate comprising: an optical circuit unit comprising the optical waveguide according to claim 7; and an electric circuit unit comprising a metal conductive path.   The optoelectric composite substrate according to claim 8 is provided with flexibility, a core layer is exposed on both end faces of the optoelectric composite substrate, and a light emitting element is provided facing the core layer exposed on one end face. An optical communication module comprising a light receiving element facing a core layer exposed on the other end face.

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