Ferrules and optical modules for multi-core optical connectors

Abstract

[Problem] To provide a multicore optical connector ferrule that has low connection loss even when optical wiring is mounted on a substrate. [Solution] This multicore optical connector ferrule: is obtained by molding a resin composition that includes polyphenylene sulfide; and has optical fiber insertion holes 103 and a guide hole 102 for guide pin insertion. The dimensional variation of the multicore optical connector ferrule when heated at 260°C is no more than 0.1%. The multicore optical connector ferrule is a high-density optical connector having at least eight optical fiber insertion holes provided therein. The optical fiber insertion holes have an internal diameter of 127 μm and are provided at a pitch of no more than 250 μm.

Description

Technical Field

[0001] The present invention relates to a ferrule for a multi-core optical connector and an optical module using such a ferrule.

Background Art

[0002] In optical communication, an optical connector is used to mechanically connect optical fibers. Particularly, the MT connector (Mechanically Transferable connector) developed for optical network equipment is a reliable multi-core optical connector widely used mainly in optical communication networks. This MT connector detachably connects a pair of optical connectors using guide pins and clips, and is used, for example, for connecting optical fiber ribbon cores of 2 to 12 cores, optical fiber cords, etc. Further, not only this MT connector, but also a configuration in which an optical ferrule is housed in a housing and provided with a guide pin, a latch mechanism, etc. as an MPO connector is known.

[0003] For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2002-350680) discloses an optical ferrule capable of physical contact between optical fibers. The optical ferrule described in Patent Document 1 is an injection molded product of a resin composition in which 100 to 300 parts by mass of silica having a maximum particle diameter of 100 μm or less and 50 to 300 parts by mass of barium titanate are blended with 100 parts by mass of polyphenylene sulfide resin.

[0004] Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2001-174666) discloses an optical ferrule capable of physical contact between optical fibers.

[0005] The optical ferrule described in Patent Document 2 is characterized by being a molded article of a resin composition that contains a base resin, silica, and whiskers as essential components, and has a melt viscosity of 300 to 600 [Pa·sec] at a shear rate of 900 [1 / sec] at a temperature of 340°C, as measured using a capillary with a diameter of 0.1 mm and a depth of 30 mm as specified in JIS-K-7199. Preferably, the base resin is a linear polyphenylene sulfide resin, and the resin composition is an injection molded article comprising 100 parts by weight of linear polyphenylene sulfide resin, 250 to 300 parts by weight of silica, and 10 to 70 parts by weight of whiskers.

[0006] Patent Document 3 (Japanese Patent Publication No. 2004-29415) discloses an optical connector equipped with a ferrule that can further improve mechanical strength while maintaining dimensional accuracy and dimensional stability. The optical connector described in Patent Document 3 is an optical connector having an optical fiber hole and a guide hole, and a guide pin is inserted into the guide hole to position the connection of the optical fiber, and the ferrule is molded from a resin composition containing 10 to 20% by weight of polyphenylene sulfide resin and 80 to 90% by weight of silica particles.

[0007] Patent Document 4 (Japanese Patent Publication No. 2003-185886) discloses an optical connector in which an optical connector ferrule is manufactured by injection molding using a PPS resin composition containing an inorganic filler made of silica particles, and in which there is almost no silica detachment even when the optical connector is repeatedly attached and detached, and no scratches are made on the end face of the optical fiber that would affect the characteristics of the optical connector.

[0008] The optical connector described in Patent Document 4 comprises an optical connector ferrule having at least one optical fiber insertion hole and two mating holes for inserting mating pins for connecting optical connectors together, and this optical connector ferrule is molded from a PPS resin composition containing a fibrous filler and silica particles surface-treated with a vinyl-based silane coupling agent.

[0009] Patent Document 5 (Japanese Patent Publication No. 2003-138044) discloses a molded article suitable for optical connector ferrules and the like, which has excellent injection moldability without impairing the melt flowability of the resin composition, excellent mechanical strength of the molded article, and low connection loss even after repeated attachment and detachment. The molded article described in Patent Document 5 is obtained by melt-molding a PPS resin composition comprising (A) a PPS resin in which a specific functional group X has been introduced to the molecular ends or side chains, (B) an organic compound having a carbon-carbon double bond within the same molecule and an atomic group capable of forming a chemical bond with the functional group X introduced to the PPS resin under molten mixing conditions, and (C) an inorganic filler surface-treated with a silane coupling agent having a carbon-carbon double bond, or a silane coupling agent having a carbon-carbon double bond and an inorganic filler, and then irradiating the molded article with ionizing radiation.

[0010] Patent document 6 (Japanese Patent Publication No. 2014-240958) discloses an optical module that can be surface mounted using a reflow oven and emits laser light without extending the optical fiber outside the mounting substrate.

[0011] The optical module described in Patent Document 6 comprises a plurality of optical elements that emit red, green, and blue laser light, a plurality of optical fibers that guide the laser light of each color from the plurality of optical elements, a mounting substrate on which the plurality of optical elements are mounted on the top surface and electrodes for supplying electrical signals to the plurality of optical elements are formed as through electrodes that penetrate from the top surface to the bottom surface, and a multiplexing section arranged at the corner of the mounting substrate that bundles and fixes the output ends of the plurality of optical fibers to emit multiplexed light from which the laser light of each color has been combined. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2002-350680 [Patent Document 2] Japanese Patent Publication No. 2001-174666 [Patent Document 3] Japanese Patent Publication No. 2004-29415 [Patent Document 4] Japanese Patent Publication No. 2003-185886 [Patent Document 5] Japanese Patent Publication No. 2003-138044 [Patent Document 6] Japanese Patent Publication No. 2014-240958 [Overview of the project] [Problems that the invention aims to solve]

[0013] Ferrules are a key component of multi-core optical connectors and are formed by molding synthetic resin material in a mold. The ferrule is provided with an insertion hole for inserting an optical fiber tape, and multiple optical fiber holes for positioning the stripped optical fibers are provided in communication with the optical fiber tape insertion hole. Guide holes for positioning and connecting optical connectors are also provided, running parallel to the optical fiber holes. The optical fiber tape is inserted from the rear side of the ferrule after the coating on its leading edge is removed, and the multiple exposed optical fibers are inserted into each optical fiber hole of the ferrule and secured with adhesive. The connection end faces of the optical fibers are polished together with the connection surface of the ferrule after the optical fibers are inserted into the ferrule.

[0014] In a multi-core optical connector, a guide pin is pre-inserted and fixed into the guide hole of one ferrule. This guide pin is then inserted into the guide hole of the other ferrule, and the connection surfaces of the optical connectors are brought together to connect the optical fibers in a single operation. The ferrules in such optical connectors need to be aligned with high precision along the axes of the optical fibers, and therefore the ferrules require properties such as dimensional stability and mechanical strength.

[0015] Conventionally, polyphenylene sulfide has been known to be used as a molding material for ferrules because it exhibits low shrinkage during molding, excellent dimensional stability over time, high fluidity during molding, and excellent environmental resistance. Polyphenylene sulfide (PPS) has a low melt viscosity, allowing for the incorporation of large amounts of filler, resulting in low molding shrinkage and enabling the production of ferrules with high dimensional accuracy.

[0016] The diameter and pitch of the guide holes and fiber insertion holes in this ferrule require submicron-order precision. For example, a 1 μm axial misalignment of the fiber insertion hole is said to result in a connection loss of approximately 0.2 dB. Therefore, it is necessary to mold the ferrule while taking into account hardening and shrinkage after molding, but due to the large variation in the hardening shrinkage rate of the molding material, it is extremely difficult to mold the ferrule with high dimensional accuracy. Furthermore, if temperature changes occur after the ferrule is formed, the ferrule will expand or contract, causing dimensional deformation. As a result, the position of the optical fiber fixed to the ferrule changes, leading to a problem where good connection loss cannot be obtained.

[0017] Therefore, as shown in Patent Documents 1 to 5, ferrules with excellent dimensional accuracy and dimensional stability have been developed. On the other hand, as shown in Patent Document 6, in recent years, optical modules have been developed in which optical elements are mounted on a substrate and the optical elements are optically coupled to optical fibers. As a result, optical mounting circuits that do not require electrical wiring are being considered, which allow high-speed, high-density optical communication to be directly introduced into (or near) an electronic substrate.

[0018] However, in optical modules that connect photoelectric conversion elements mounted on a substrate to ferrules to which optical fibers are connected, optical connectors with resin ferrules are sometimes mounted on the substrate and then reflowed with solder. In this case, a problem arises in which the dimensions of the ferrule change due to the heating during the reflow soldering process. As a result, the optical fiber is misaligned, which worsens the connection loss. Furthermore, since some electronic components on the circuit board become hot during operation, optical connectors mounted on the board may experience unprecedented temperature changes, which can also cause misalignment and worsen connection loss. Particularly in optical mounting circuits, with the increase in speed and capacity, there is a demand for ferrules with low connection loss and no misalignment of optical fibers even when high-density optical connectors are mounted.

[0019] The present invention is made to solve the above-mentioned drawbacks, and its object is to provide a ferrule for a multi-core optical connector with low connection loss and an optical module equipped with such a ferrule even when optical wiring is mounted on a substrate. Another object of the present invention is to provide a ferrule for a multi-core optical connector and an optical module equipped with such a ferrule, in which characteristics such as connection loss do not fluctuate before and after the solder reflow process. Another object of the present invention is to provide a ferrule for a multi-core optical connector and an optical module equipped with such a ferrule, which can maintain dimensional accuracy and dimensional stability and further improve mechanical strength. Still another object of the present invention is to provide a ferrule for a multi-core optical connector and an optical module equipped with such a ferrule, which can reduce the transmission loss of optical communication even when used in a wide temperature range while achieving weight reduction.

Means for Solving the Problems

[0020] (1) A ferrule for a multi-core optical connector according to one aspect is a molded product of a resin composition containing polyphenylene sulfide, and is a ferrule for a multi-core optical connector having an optical fiber insertion hole and a guide hole for inserting a guide pin, and the dimensional change rate after heating at 260 °C is 0.1% or less.

[0021] However, the dimensional change rate of the present invention can be obtained as shown in the following (Formula 1) from the product dimension L1 after molding and the product dimension L2 after the heating test (Fig. 2 shows L arranged in a row). The value of the dimensional change rate is an absolute value. TIFF0007837332000001.tif19165

[0022] As a result, when an optical connector is mounted on a circuit board and subjected to solder reflow, even if the ferrule is exposed to high temperatures due to the solder reflow process, dimensional changes in the ferrule are less likely to occur. Consequently, misalignment of the optical fiber can be suppressed, and adverse effects on connection loss and other properties are minimized. Therefore, characteristics such as connection loss do not change before and after the solder reflow process. Furthermore, even if electronic components on the circuit board are subjected to temperature changes due to operation, characteristics such as connection loss will not change. Therefore, even when optical wiring is mounted on the substrate, it can be used as a ferrule for a multi-core optical connector with low connection loss. In this specification, ferrules for multi-core optical connectors may sometimes be simply referred to as ferrules.

[0023] (2) The ferrule for a multi-core optical connector according to the second invention is a ferrule conforming to a single surface, further having a boot insertion hole into which a boot can be inserted from the rear end face side facing the connecting end face of the ferrule, and the boot insertion hole may have a thermal expansion absorbing portion that absorbs the thermal expansion of the internal members of the ferrule.

[0024] The ferrule of the present invention is characterized by the fact that it undergoes almost no dimensional change even when exposed to high temperatures. On the other hand, internal components that can be combined with the ferrule include optical fibers, ferrule boots through which multiple optical fibers are inserted, and adhesives for fixing them together. Of these, adhesives have a large coefficient of thermal expansion and are filled inside the ferrule. Therefore, if existing adhesives are used, the thermal expansion of the adhesive can put a load on the ferrule, and in some cases, the ferrule may break. Therefore, by providing a thermal expansion absorption section in the boot insertion hole, the thermal expansion of the internal components can be spatially absorbed, relieving unnecessary stress and preventing deformation or damage to the ferrule.

[0025] (3) The ferrule for a multi-core optical connector according to the third invention is a single-faced or a ferrule for a multi-core optical connector according to the second invention, wherein the length in the width direction of the thermal expansion absorbing portion may be 0.5 times or more and 0.9 times or less of the length in the width direction of the boot insertion hole.

[0026] This allows the boot to be securely held in place while adequately absorbing the thermal expansion of the internal components.

[0027] (4) The ferrule for a multi-core optical connector according to the fourth invention is a ferrule according to any of the third inventions from one perspective, and is a high-density optical connector provided with eight or more optical fiber insertion holes, wherein the optical fiber insertion holes may have an inner diameter of 127 μm or less and a pitch of 250 μm or less.

[0028] In optical connectors with small fiber diameters and high density, malfunctions can occur even if the relative positions of all the fiber optics deviate slightly from the design. By using the ferrule according to the fourth invention, high-density, high-speed, high-capacity optical communication can be directly introduced to (or near) the substrate, and an optical mounting circuit without electrical wiring can be realized. Note that the inner diameter and pitch values ​​are nominal values ​​and may have tolerances.

[0029] (5) The ferrule for a multi-core optical connector according to the fifth invention is a ferrule for a multi-core optical connector according to any of the fourth inventions from one perspective, wherein the ferrule may be connected to a photoelectric conversion element provided on a substrate.

[0030] This allows for direct connection between the photoelectric conversion element on the circuit board and the optical fiber, enabling optical mounting closer to electronic components (such as CPUs) on the circuit board. Furthermore, because it is a multi-core optical connector ferrule with dimensional stability and low connection loss even under thermal fluctuations, high-density optical lines can be mounted even in close proximity to electronic components, enabling high-speed, high-capacity information processing.

[0031] (6) The optical module according to the sixth invention is an optical module in which a multi-core optical connector equipped with a ferrule for a multi-core optical connector is mounted on a substrate by solder reflow, wherein the ferrule is a molded article of a resin composition containing polyphenylene sulfide, has an optical fiber insertion hole and a guide hole for inserting a guide pin, and the dimensional change rate of the ferrule when heated at 260°C is 0.1% or less.

[0032] This design minimizes dimensional changes in the ferrules when they are exposed to high temperatures during the solder reflow process when optical modules are manufactured by mounting optical connectors onto a substrate using solder reflow. As a result, misalignment of the optical fibers is suppressed, minimizing adverse effects on connection loss and other properties. Therefore, characteristics such as connection loss do not change before and after the solder reflow process. Furthermore, even if electronic components on the substrate are subjected to temperature changes due to operation, characteristics such as connection loss will not change. Therefore, even when optical wiring is mounted on the substrate, it can be used as a ferrule for a multi-core optical connector with low connection loss.

[0033] (7) The optical module according to the seventh invention is an optical module in which a multi-core optical connector equipped with a ferrule for a multi-core optical connector is mounted on a substrate by solder reflow, wherein the ferrule has an optical fiber insertion hole and a guide hole for inserting a guide pin, and the ferrule is a molded product made of a resin composition containing polyphenylene sulfide that has been heat-treated at a temperature T3, the heat-treated temperature T3 is a temperature below the glass transition temperature T1 of polyphenylene sulfide and a temperature above the solder reflow temperature T2.

[0034] As a result, the ferrules obtained by heat treatment are annealed at a predetermined temperature, which sufficiently suppresses the generation of distortion due to thermal shrinkage and improves the dimensional accuracy of the ferrules.

[0035] (8) The optical module according to the eighth invention is the optical module according to the seventh invention, wherein the solder reflow temperature T2 is 20°C to 50°C lower than the glass transition temperature T1 of polyphenylene sulfide, and the temperature T3 for heat-treating the molded product is 5°C to 20°C higher than the solder reflow temperature T2.

[0036] As a result, the ferrules obtained through heat treatment are less susceptible to distortion due to thermal shrinkage, and the dimensional accuracy of the ferrules can be improved. If the heat treatment temperature T3 for the molded product is too low, deviating from the solder reflow temperature T2 by 5°C to 20°C, the heat treatment may be insufficient, leading to significant dimensional changes in the ferrule. Conversely, if the temperature is too high, the ferrule may deform or its mechanical strength may decrease.

[0037] (9) The optical module according to the ninth invention is the optical module according to the eighth invention, wherein the glass transition temperature T1 of polyphenylene sulfide is 290°C or more and 310°C or less, the solder reflow temperature T2 is 250°C or more and 270°C or less, and the heat treatment temperature T3 is 265°C or more and 290°C or less.

[0038] As a result, the ferrules obtained by heat treatment are further sufficiently protected from distortion caused by thermal shrinkage, thereby improving the dimensional accuracy of the ferrules.

[0039] (10) The optical module according to the tenth invention is an optical module according to any of the seventh to nineth inventions, wherein the dimensional change rate of the ferrule heated at the solder reflow temperature T2 is 0.1% or less when heated at 260°C.

[0040] As a result, the ferrules obtained through heat treatment are less susceptible to distortion due to thermal shrinkage, and the dimensional accuracy of the ferrules can be improved.

[0041] (11) The optical module according to the 11th invention is the optical module according to the 7th invention, further comprising a boot insertion hole into which a boot can be inserted from the rear end face side facing the connecting end face of the ferrule, and the boot insertion hole may have a thermal expansion absorbing portion that absorbs the thermal expansion of the internal member of the ferrule.

[0042] The ferrule of the present invention is characterized by the fact that it undergoes almost no dimensional change even when exposed to high temperatures. On the other hand, internal components that can be combined with the ferrule include optical fibers, ferrule boots through which multiple optical fibers are inserted, and adhesives for fixing them together. Of these, adhesives have a large coefficient of thermal expansion and are filled inside the ferrule. Therefore, if existing adhesives are used, the thermal expansion of the adhesive can put a load on the ferrule, and in some cases, the ferrule may break. Therefore, by providing a thermal expansion absorption section in the boot insertion hole, the thermal expansion of the internal components can be spatially absorbed, relieving unnecessary stress and preventing deformation or damage to the ferrule. [Brief explanation of the drawing]

[0043] [Figure 1] This is a schematic diagram showing an example of a ferrule according to this embodiment. [Figure 2] This is a schematic diagram illustrating the ferrule of this embodiment. [Figure 3] This is a schematic diagram of an optical module mounted on a circuit board. [Figure 4] This is a schematic diagram of an optical module mounted in close proximity to electronic components on a circuit board. [Figure 5] This is a schematic diagram showing an example of a ferrule according to Embodiment 3. [Figure 6] This is a schematic diagram showing an example of a ferrule according to Embodiment 4. [Modes for carrying out the invention]

[0044] Embodiments of the present invention will be described below with reference to the drawings. In the following description, identical parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0045] [Embodiment 1] Figures 1(a), (b), (c), and (d) are the left side view, front view, right side view, and cross-sectional view of the ferrule 100 of this embodiment, respectively. Figure 2 is a schematic diagram illustrating the ferrule 100 of this embodiment. The ferrule 100 is a key component of the multi-core optical connector and can be formed by injection molding a resin composition containing PPS in a mold.

[0046] The ferrule 100 has an insertion hole 103 for the optical fiber 11 and a guide hole 102 for inserting a guide pin, and is a molded article made of a resin composition containing polyphenylene sulfide. In this invention, the dimensional change rate when the ferrule 100 is heated at 260°C is 0.1% or less. However, the dimensional variation rate of the present invention can be determined from the product dimensions L1 after molding and the product dimensions L2 after heating, as shown in (Equation 1) below (Figure 2 shows L arranged in a single row). The value of the dimensional variation rate is an absolute number. JPEG0007837332000002.jpg19165

[0047] By keeping the dimensional change rate of the ferrule 100 when heated at 260°C to 0.1% or less, dimensional changes are less likely to occur in the ferrule 100 even when it is exposed to high temperatures (usually around 260°C) during the solder reflow process when the optical connector 12 is mounted on the substrate 14 by solder reflow. If the dimensional change rate exceeds 0.1%, the dimensional change of the ferrule 100 will be large, which can cause misalignment of the optical fiber 11 inserted and fixed in the fiber hole of the ferrule 100, leading to increased connection loss.

[0048] As shown in Figure 1, the ferrule 100 of this embodiment is provided with an optical fiber tape receiving port 101 into which an optical fiber tape is inserted, and a plurality of fiber insertion holes 103 for inserting and positioning an optical fiber 11 with its coating removed are provided communicating with the optical fiber tape receiving port 101. In addition, the ferrule 100 is provided with guide holes 102 for positioning and connecting an optical connector 12, which penetrate parallel to the optical fiber insertion holes 103.

[0049] In this embodiment, the ferrule 100 has an opening 104 formed therein as an adhesive filling hole for filling with adhesive. The optical fiber tape is inserted into the fiber tape receiving port 101 from the rear side of the ferrule 100 after removing the coating from the tip portion, and the multiple exposed optical fibers 11 are inserted into each optical fiber insertion hole 103 and fixed by the adhesive filled in the opening 104. The connecting end faces of the optical fibers 11 are polished together with the connecting surface of the ferrule 100 after the optical fibers 11 are inserted into the ferrule 100.

[0050] The optical fiber 11 is led out with its exit portion on the back of the ferrule protected by a boot made of an elastic material such as rubber or synthetic resin. The boot is fixed with adhesive to the boot insertion hole 110 on the back of the ferrule 100.

[0051] As the optical fiber tape to be attached to the ferrule 100, an optical fiber tape core in which coated optical fiber strands are integrated with a common coating, or an optical fiber ribbon cord in which an additional protective coating is applied to the optical fiber tape core can be used. A guide pin is pre-inserted and fixed into the guide hole 102 of one of the ferrules 100 that make up the multi-core optical connector. By inserting this guide pin into the guide hole 102 of the other ferrule 100 and bringing the connection surfaces of the optical connector 12 together, the optical fibers 11 are connected.

[0052] In the optical connector 12 configured in this way, the axis of the optical fiber 11 is positioned by guide pins, and the connection surfaces are brought together by coupling clips or the like to perform the optical connection. As the optical fiber 11, for example, single-mode or multi-mode optical fiber can be used, and a nominal cladding diameter of 125 μm or 80 μm can be used. In addition, the number of cores in the optical fiber insertion hole 103 can be, for example, 8 cores, 12 cores, 24 cores, 32 cores or 60 cores, and if the number of cores is large, it may be formed in multiple stages.

[0053] Furthermore, the ferrule 100 can also be configured to allow for multi-stage connection of optical fibers 11 by applying the shape of an MT connector (JIS C5981) with a positioning pin coupling method. Since the ferrule 100 in this embodiment conforms to existing pin coupling standards, optical mounting to the substrate 14 can be achieved by utilizing conventional connection components. As described above, the optical fiber 11 is used as a tape core, where multiple fibers are bundled together in a tape shape. The outer sheathing layer of this tape core is removed to a predetermined terminal length to expose the optical fiber 11, which is then inserted into the ferrule 100 and supported at a specified pitch for connection. The ferrule 100 may be a roughly rectangular parallelepiped with a stepped portion on its outside. One end face of the ferrule 100 is provided with a fiber tape receiving port 101 for receiving the tape core into the ferrule 100, and a support portion 105 for supporting the optical fiber 11 is provided.

[0054] The opening 104 is formed on the upper end surface of the ferrule 100 to connect the internal space with the outside, and as shown in Figure 2, it is a rectangular opening that allows a view of the interior, located vertically above the surface to which the adhesive is filled. The opening 104 is used to visually check the insertion of the optical fiber 11 into the support part 105, and also as a filling port for pouring in adhesive to fix it after insertion. The shape of the filling port (opening) 104 is arbitrary as long as the optical fiber insertion hole 103 can be seen. The optical fiber insertion hole 103 is a hole that penetrates from the insertion surface to the connection surface of the support part 105, and adjacent holes are formed parallel to each other.

[0055] Figure 3 shows a schematic diagram of an optical module mounted on a substrate 14. The ferrule 100 in this embodiment is fixed directly on or near the substrate 14 and is connected to the photoelectric conversion element 13 via an optical fiber 11. There are no particular restrictions on what the ferrule 100 in this embodiment connects to; for example, it can be connected to an existing MT ferrule 200, and the optical fiber 11' extending from the MT ferrule 200 is wired to the side of the housing 10. The ferrule 100 of this embodiment can be connected as an optical connector 12 using a general MPO housing. The housing may contain a compression spring for mechanically connecting the optical fiber 11. The end face of the connector may also be polished to 8° to reduce the return loss. Furthermore, when optically mounting the electronic circuit onto the substrate 14, an optical transceiver having a photoelectric conversion element 13 can be provided at the edge of the substrate 14, thereby connecting it to the optical connector 12 (Figure 3(a)). An example of an optical transceiver is one in which a photodetector and a light-emitting element are housed together with a lens in a device holder as a photoelectric conversion element 13. In this device holder type optical transceiver, the leads (or their FPCs) of the photoelectric conversion element 13 are soldered to a substrate 14 and connected to a ferrule 100 attached to a receptacle fixed to the substrate 14.

[0056] The ferrule 100 of this embodiment is formed by molding a resin composition mainly composed of polyphenylene sulfide (hereinafter also referred to as PPS). In addition to PPS, the resin composition may contain an inorganic filler. The inorganic filler may include silica particles or fibrous fillers.

[0057] (PPS) The PPS used in this invention can be of the cross-linked, semi-cross-linked, or linear type, or a mixture thereof. PPS of the grade used for injection molding can be used. While a linear molecular structure is preferable for PPS in terms of melt flowability, tensile strength, and fracture bending strain, a branched structure can also be introduced to improve various properties.

[0058] The molecular weight of PPS is determined at 300°C for 500 seconds to ensure the melting properties of the resin composition containing inorganic fillers. -1 Expressed as a melt viscosity at a shear rate, a range of 10 to 100 Pa·s is preferred, and a range of 15 to 80 Pa·s is more preferred. With PPS having a melt viscosity in this range, melt fluidity is ensured, the dimensional accuracy of the molded product is good, and the mechanical strength is also excellent.

[0059] Examples of fibrous fillers include glass fibers, carbon fibers, tungsten core wires, or so-called boron fibers or silicon carbide fibers obtained by depositing boron or silicon carbide onto carbon fibers, aromatic polyamide fibers, and various other types of fibrous fillers. These fibrous fillers may be used individually or in combination of multiple types.

[0060] Among the fibrous fillers mentioned above, glass fibers or carbon fibers are particularly preferred. By using glass fibers and carbon fibers, the molded product can exhibit excellent mechanical strength, such as tensile strength, flexural strength, and flexural modulus, and the coefficient of thermal expansion can also be reduced.

[0061] Carbon fibers can be used regardless of the type of raw material, including rayon-based, polyacrylonitrile-based (PAN-based), lignin-poval-based mixtures, and special pitch-based materials. Furthermore, the carbon fibers can be either long or short single fibers.

[0062] Furthermore, in order to improve the adhesion between the fibrous filler and the base resin PPS and to improve the mechanical properties of the ferrule 100, the surface of the fibrous filler may be surface-treated using a treatment agent containing epoxy resin, polyamide resin, polycarbonate resin, polyacetal resin, etc., and / or a silane coupling agent. When the resin composition contains silica particles and fibrous fillers, it is preferable that the resin composition is a mixture containing 20-40% by weight of PPS resin and 60-80% by weight of inorganic fillers.

[0063] (Silica particles) When only fibrous material is used as a filler, the molded product is prone to anisotropy, and problems such as different molding shrinkage rates depending on the part of the ferrule 100 may occur. In the present invention, it is preferable to use a combination of fibrous filler and silica particles with good isotropy in the ferrule 100.

[0064] The silica particles may be fused silica, crystalline silica, or a mixture thereof. The silica particles may also be spherical or crushed, or a mixture thereof. Silica particles are classified into spherical and amorphous types based on their shape, and in this invention, either of these, or a mixture of both, can be used; however, the use of spherical silica is preferred. The silica particles contained in the resin composition of the present invention preferably have an average particle size in the range of 0.1 μm to 1.0 μm.

[0065] Furthermore, in this invention, silica particles can be included after silane treatment. Since silane treatment of silica particles improves adhesion with PPS, the mechanical strength of the ferrule 100 after molding can be increased. Various silanes such as vinylsilane, phenylsilane, aminosilane, metalcrylsilane, epoxysilane, and mercaptosilane can be used as silane coupling agents for this purpose.

[0066] The amount of silica particles can be blended in an amount of 100 to 300 parts by mass per 100 parts by mass of polyphenylene sulfide. Preferably, it is 100 to 200 parts by mass per 100 parts by mass of polyphenylene sulfide. To maintain sufficient fluidity for good injection molding of the resin composition, it is desirable to keep the silica particle content at 70% by weight or less.

[0067] (Other additives) In addition, the resin composition used in the present invention may contain conventional additives such as antioxidants, heat stabilizers, UV inhibitors, lubricants, colorants, and flame retardants, as long as they do not impair the effects of the present invention.

[0068] (Manufacturing method for ferrule 100) The materials constituting the resin composition can be dry-mixed as needed using a Henschel mixer, ball mixer, ribbon blender, Reidige mixer, Ultra Henschel mixer, etc., and then melt-kneaded in a melt extruder such as a twin-screw compounding extruder to obtain molding pellets. The ferrule 100 can be molded by extruding a molten resin composition into a mold using a molding machine such as an injection molding machine, forming it into the shape of an MT ferrule, and then cooling and solidifying it. After molding, a heat treatment process (also called annealing) is performed to remove distortion and / or residual stress.

[0069] Here, the "annealing process" is a process in which a material from which strain and / or residual stress is to be removed is exposed to high temperatures. The maximum temperature in the annealing process is below the temperature at which the molded product does not deform. There is no particular limit to the holding time, but 30 minutes or more is preferred, and 1 hour or more is more preferred.

[0070] Exposure of the resin composition to the annealing temperature causes dimensional changes (shrinkage). This promotes crystallization of PPS, increasing its mechanical strength and improving its dimensional stability. In particular, annealing at a temperature higher than the solder reflow temperature T2 minimizes the dimensional change rate when the ferrule 100 is exposed to the solder reflow temperature T2.

[0071] Furthermore, the glass transition temperature of the ferrule 100 is preferably 85°C or higher, more preferably 100°C or higher, and particularly preferably 130°C or higher. The upper limit of the glass transition temperature is usually 300°C, preferably around 200°C. This improves the heat resistance of the ferrule 100 and makes it less susceptible to thermal deformation, allowing the optical module to be used without problems even in high-temperature environments.

[0072] (Optical module) The optical module of the present invention has an optical connector 12 equipped with a ferrule 100 mounted on a substrate 14 by solder reflow. More specifically, the optical module includes a photoelectric conversion element, a ferrule 100 having an optical fiber insertion hole at a position corresponding to the photoelectric conversion element, and an optical fiber 11 inserted through the optical fiber insertion hole of the ferrule 100 and optically connected to the photoelectric conversion element. An optical waveguide can be provided between the photoelectric conversion element and the optical fiber 11.

[0073] As described above, the ferrule 100 has an insertion hole 103 for the optical fiber 11 and a guide hole 102 for inserting a guide pin. The ferrule 100 is obtained by forming a molded article from a resin composition containing polyphenylene sulfide and then heat-treating the molded article at a heat treatment temperature T3. The heat treatment temperature T3 is preferably less than the glass transition temperature T1 of polyphenylene sulfide and greater than the solder reflow temperature T2.

[0074] In particular, the solder reflow temperature T2 is the glass transition temperature T1-(20~50°C) of polyphenylene sulfide, and the temperature T3 for heat-treating the molded product can be the solder reflow temperature T2+(5~20°C). The glass transition temperature T1 of polyphenylene sulfide can be 290-310°C, the solder reflow temperature T2 can be 240-270°C, and the heat treatment temperature T3 can be 250-290°C.

[0075] If the solder reflow temperature T2 is significantly higher than the glass transition temperature T1 of polyphenylene sulfide (which is 20-50°C lower), the dimensional variation of ferrule 100 may increase. Conversely, if the temperature is too low, the effect on improving the dimensional accuracy of ferrule 100 may be small. The heat treatment temperature T3 for the molded product may be 5 to 20°C higher than the solder reflow temperature T2. Increasing the heat treatment temperature will result in greater dimensional changes. On the other hand, temperatures close to the melting temperature make the product more susceptible to deformation and other effects. Temperature T3 can be selected depending on the product type or application. [Examples]

[0076] (Example 1) Examples of the present invention will be described. (1) Resin composition for ferrules As the resin composition for the ferrules, we prepared DuraFide manufactured by Polyplastics Co., Ltd. This resin composition contains a linear polyphenylene sulfide resin, silica particles, and fibrous fillers.

[0077] (2) Forming of ferrules The resin composition was manufactured by melt-kneading the above-mentioned PPS, silica particles surface-treated with a silane coupling agent, and fibrous filler in a twin-screw extruder, and then processing them into pellets. Using the obtained resin composition, a ferrule 100 with the configuration shown in Figure 1 was molded by injection molding. It was confirmed that the ferrule 100 obtained by injection molding had shrunk by 0.5% relative to the mold design.

[0078] (3) Heat treatment Next, the molded product (MT ferrule) was placed in a constant temperature bath and subjected to a 3-hour annealing treatment at a set temperature higher than the reflow temperature (270°C, 280°C, 290°C, and 300°C, respectively). The dimensional change rate of ferrule 100 after heat treatment was compared with that before heat treatment. The dimensional change values ​​before and after heat treatment are shown in Table 1.

[0079] [Table 1]

[0080] (4) Reflow mock test After annealing, the MT ferrules were returned to room temperature and then heated in a constant temperature bath at 260°C for 20 minutes to simulate a reflow soldering test. While typical solder reflow soldering can be done at 260°C for a few minutes, this test involved exposing the ferrules to a high-temperature environment for 20 minutes to ensure that no thermal fluctuations occurred. After the test, the MT ferrules were returned to room temperature and their dimensions were measured to confirm the changes due to heating. As a result, the MT ferrules that underwent heat treatment showed a dimensional change rate of 0.1% or less (below the measurement limit) at all annealing temperatures listed in Table 1.

[0081] (Comparative example) As a comparative example, a reflow simulation test was performed on an MT ferrule that had not undergone heat treatment, in the same manner as in Example 1. As a result, it was confirmed that the dimensional change rate was 0.2% or more. Therefore, it was confirmed that heat treatment of the PPS MT ferrule at 265°C to 290°C reliably suppresses dimensional changes at the simulated test reflow temperature (260°C).

[0082] [Embodiment 2] In Embodiment 1, an example of the shape of an MT connector (JIS C5981) was shown, but when mounting it on an electronic circuit board, it is preferable to position the optical terminal closer to the electronic component 15. In this case, as shown in Figure 3(b), an optical connector 12 that can be wired perpendicular to the circuit board 14 can be used.

[0083] Figure 4 is a schematic diagram of an optical module mounted in close proximity to an electronic component 15 on a substrate. In this case, the optical connector 12 connects the photoelectric conversion element 13 mounted on the substrate 14 to the optical fiber 11, and the optical fiber 11 is routed parallel to the substrate 14 while maintaining a predetermined radius of curvature. This allows the optical connector 12 to be mounted in close proximity to an electronic component 15 such as a CPU.

[0084] [Embodiment 3] Figures 5(a), (b), (c), (d), and (e) are left side view, front view, right side view, bottom view, and G-section view of the ferrule 100 of Embodiment 3, respectively, and are examples of a ferrule 100 equipped with a thermal expansion absorbing portion 111 in the boot insertion hole 110 to absorb the thermal expansion of the internal member.

[0085] In the third embodiment, the ferrule 100 has a boot insertion hole 110 on the rear end face side facing the connecting end face of the ferrule 100, and the thermal expansion absorbing portion 111 is on the upper side adjacent to the rear end face, and is provided such that the boot insertion hole 110 protrudes toward the upper side to form a notch. In addition, boot holding portions 112 for holding the boot are formed on both ends in the width direction of the thermal expansion absorbing portion 111. In Embodiment 3, the upper surface of the ferrule 100 is formed in the same manner as in Embodiment 1, and the thermal expansion absorption portion 111 is formed inside the ferrule 100.

[0086] The ferrule 100 of the present invention exhibits almost no dimensional changes even when exposed to high reflow temperatures. On the other hand, internal components to be combined with the ferrule 100 include optical fibers 11, a ferrule boot through which tapes of multiple optical fibers are inserted, and an adhesive for fixing the optical fibers. Of these, the adhesive has a large coefficient of thermal expansion and is filled inside the ferrule 100. Therefore, if an existing adhesive is used, the thermal expansion of the adhesive will put a load on the ferrule 100, and in some cases the ferrule 100 may break. By providing a thermal expansion absorption section 111 in the boot insertion hole 110, the thermal expansion of the adhesive can be absorbed spatially, relieving unnecessary stress and thereby preventing deformation or breakage of the ferrule 100. Examples of existing adhesives include epoxy resins, which typically have a coefficient of linear expansion of about 100 to 250 ppm / °C. Examples of existing boots include those made of elastic and deformable materials such as rubber and silicone elastomer.

[0087] In this case, the thickness of the thermal expansion absorbing portion 111 in the height direction (up and down direction) is preferably 0.1 times or more, and more preferably 0.5 times or more, the thickness of the boot insertion hole 110 in the height direction. This allows for sufficient absorption of the thermal expansion of the adhesive. Furthermore, the widthwise length B of the thermal expansion absorbing portion 111 is preferably 0.5 to 0.9 times the widthwise length A of the boot insertion hole 110, and more preferably 0.6 to 0.8 times. This ensures that the boot is securely held while adequately absorbing the thermal expansion of the internal components. In Figure 5, the thermal expansion absorbing portion 111 is provided on the upper side of the ferrule 100, but it may also be provided on the lower side of the ferrule 100. Furthermore, the length of the thermal expansion absorbing portion 111 in the depth direction (along the fiber axis direction) is set to communicate with the opening 104, but this can be appropriately designed depending on the size of the boot to be inserted. Also, it is preferable that the widthwise length B of the thermal expansion absorbing portion 111 is shorter than the widthwise length of the opening 104.

[0088] [Embodiment 4] Figures 6(a), (b), (c), (d), and (e) are left side view, front view, right side view, bottom view, and G-section view of the ferrule 100 of Embodiment 3, respectively, which are other examples of the ferrule 100 having a thermal expansion absorbing portion 111 in the boot insertion hole 110 to absorb the thermal expansion of the internal members.

[0089] The ferrule 100 according to Embodiment 4 is similar to Embodiment 3 in that the thermal expansion absorbing portion 111 is provided on the upper surface adjacent to the rear end surface, however, the expansion absorbing portion 111 in this embodiment is formed to open to the upper surface of the ferrule 100. Therefore, the boot insertion hole 110 is formed to open in a way that connects the rear end surface and a portion of the upper surface of the ferrule 100. This allows for spatial absorption of thermal expansion of the internal components, thereby relieving unnecessary stress and preventing deformation or breakage of the ferrule 100, similar to embodiment 3. Furthermore, since only a connecting lower opening is provided on the rear end surface side of the ferrule 100, the structure is simple and easy to manufacture. Furthermore, boot holding portions 112 for holding the boot are formed at both ends in the width direction of the thermal expansion absorbing portion 111.

[0090] In this case, the thickness of the thermal expansion absorbing portion 111 in the height direction is preferably 0.1 times or more, and more preferably 0.5 times or more, the thickness of the boot insertion hole 110 in the height direction. This allows for sufficient absorption of the thermal expansion of the internal components. Furthermore, the widthwise length B of the thermal expansion absorbing portion 111 is preferably 0.5 to 0.9 times the widthwise length A of the boot insertion hole 110, and more preferably 0.6 to 0.8 times. This ensures that the boot is securely held while adequately absorbing the thermal expansion of the internal components. The length of the thermal expansion absorption section 111 in the depth direction (along the fiber axis direction) is set to communicate with the opening 104, but it can be appropriately designed depending on the size of the boot to be inserted. Furthermore, it is preferable that the length B of the thermal expansion absorption section 111 in the width direction be shorter than the length of the opening 104 in the width direction.

[0091] (Reflow mock exam) In the ferrules shown in Embodiments 1 and 4 (Figures 1 and 6), a silicone boot was attached, a quartz optical fiber was inserted, an epoxy thermosetting adhesive was applied and filled through the receiving port 101, and the adhesive was cured by heating to approximately 120°C to complete the assembly. Then, a simulated reflow test was conducted at 260°C for 10 minutes. In the sample using the ferrule 100 shown in Figure 1, some cracks developed due to internal stress. On the other hand, the sample using the ferrule 100 shown in Figure 6, which is equipped with a thermal expansion absorption section 111, did not develop any defects such as cracks even after the simulated reflow test.

[0092] In this invention, the ferrule 100 corresponds to a "ferrule," the insertion hole 103 corresponds to an "optical fiber insertion hole," the guide hole 102 corresponds to a "guide hole," the substrate 14 corresponds to a "substrate," and the optical connector 12 corresponds to a "multi-core optical connector."

[0093] While the above describes a preferred embodiment of the present invention, the present invention is not limited thereto. It will be understood that various other embodiments can be made without departing from the spirit and scope of the present invention. Furthermore, although the operation and effects of the configuration of the present invention are described in this embodiment, these operation and effects are examples and do not limit the present invention. [Explanation of symbols]

[0094] 10 cabinets 11 Optical Fiber 12 Optical Connectors 13 Photoelectric conversion element 14 circuit boards 15 Electronic Components 100 ferrules 101 Receptor opening 102 Guide hole 103 Optical fiber insertion hole 104 Opening 105 Support part 110 Boot insertion hole 111 Thermal expansion absorption section 112 Boot retaining part

Claims

1. This is a molded article of a resin composition containing polyphenylene sulfide as the main component of the base resin. A ferrule for a multi-core optical connector having an optical fiber insertion hole and a guide hole for inserting a guide pin, A ferrule for multi-core optical connectors with a dimensional change rate of 0.1% or less when heated at 260°C.

2. The resin composition contains 20% by weight or more and 40% by weight or less of polyphenylene sulfide, the ferrule for a multi-core optical connector according to claim 1.

3. The resin composition further comprises 60% by weight or more and 80% by weight or less of an inorganic filler, as described in claim 2, for a ferrule for a multi-core optical connector.

4. The ferrule further has a boot insertion hole into which the boot can be inserted from the rear end face side facing the connecting end face of the ferrule, The ferrule for a multi-core optical connector according to claim 1, wherein the boot insertion hole has a thermal expansion absorbing portion that absorbs the thermal expansion of the internal member of the ferrule.

5. The ferrule for a multi-core optical connector according to claim 4, wherein the length in the width direction of the thermal expansion absorbing portion is 0.5 times or more and 0.9 times or less the length in the width direction of the boot insertion hole.

6. The ferrule for a high-density optical connector is provided with eight or more optical fiber insertion holes. The ferrule for a multi-core optical connector according to claim 1, wherein the optical fiber insertion holes have an inner diameter of 127 μm or less and a pitch of 250 μm or less.

7. The ferrule is connected to an optoelectronic conversion element provided on a substrate, as described in claim 1, for a multi-core optical connector.

8. An optical module comprising a ferrule as described in claim 1, a photoelectric conversion element, and a substrate, The ferrule is an optical module optically connected to the photoelectric conversion element.

9. An optical module comprising a ferrule according to claim 4, a photoelectric conversion element, and a substrate, The ferrule is an optical module optically connected to the photoelectric conversion element.

10. This is a molded article of a resin composition containing polyphenylene sulfide as the main component of the base resin. A method for manufacturing a ferrule for a multi-core optical connector having an optical fiber insertion hole and a guide hole for inserting a guide pin, The process involves heat treatment at a temperature T3 after molding. A method for manufacturing a ferrule for a multi-core optical connector, wherein the heat treatment temperature T3 is a temperature below the glass transition temperature T1 of the polyphenylene sulfide and above the solder reflow temperature T2.

11. The method for manufacturing a ferrule for a multi-core optical connector according to claim 10, wherein the solder reflow temperature T2 is 20°C to 50°C lower than the glass transition temperature T1 of the polyphenylene sulfide, and the temperature T3 for heat-treating the molded product is 5°C to 20°C higher than the solder reflow temperature T2.

12. A method for manufacturing a ferrule for a multi-core optical connector according to claim 10, wherein the glass transition temperature T1 of the polyphenylene sulfide is 290°C or more and 310°C or less, the solder reflow temperature T2 is 250°C or more and 270°C or less, and the heat treatment temperature T3 is 265°C or more and 290°C or less.

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