Ferrule, ferrule manufacturing method, ferrule-equipped optical fiber ribbon, and ferrule-equipped optical fiber ribbon manufacturing method

Abstract

A ferrule (1) for an optical connector is a member in which an optical fiber is fixed, and the tip side becomes a connection end surface (7) of the optical fiber. Furthermore, the ferrule (1) for an optical connector is formed from a PPS (polyphenylene sulfide) resin containing a filler (for example, inorganic fibers or a filler), for example, by injection molding. The internal space (13) communicates with the front end side of the ferrule (1) for the optical connector and serves as a hole (9) through which an optical fiber is inserted. The ferrule (1) for an optical connector according to the present embodiment has a shrinkage rate of 0.13% or less at 260 DEG C for 1 minute.

Description

Technical Field

[0001] The present invention relates to a ferrule for an optical connector and the like for fixing an optical fiber inside. Background Art

[0002] In order to connect optical fibers to each other, various optical connectors and ferrules for connectors have been proposed. For example, there is an MT type ferrule, which has a hole on the connection end face side into which a pair of guide pins can be inserted, and the end face of the optical fiber is exposed between the guide pins. Inside such an MT type ferrule, the optical fiber is fixed by an adhesive. Therefore, a window for injecting the adhesive into the inside is formed in a part of the ferrule, and the adhesive is injected from the injection window in a state where the optical fiber is arranged inside, thereby fixing the optical fiber to the ferrule (for example, Patent Documents 1 and 2).

[0003] In recent years, the demand for applying optical wiring to circuit boards has been increasing. In the manufacturing process of circuit boards, there is a process called reflow soldering, which subjects the product to a high temperature of 230 to 260°C. The ferrule, which is an optical connection component, is also required to be resistant to reflow soldering. However, the existing MT ferrule will shrink due to the reflow soldering temperature (230 to 260°C), and it is impossible to maintain the dimensional accuracy required by the ferrule. In addition, due to the thermal expansion difference between the optical fiber built into the ferrule and the epoxy adhesive that bonds the optical fiber, after the reflow soldering is put in, the end face of the optical fiber becomes introduced into the ferrule, making it impossible to perform the so-called PC (Physical Contact) connection.

[0004] In response to this, a method has been proposed in which a base resin of a material is changed from PPS (polyphenylene sulfide) which is generally used to PEEK (polyetheretherketone resin) to impart heat resistance to the material (Patent Document 3).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2-146508

[0008] Patent Document 2: Japanese Patent Application Publication No. 2002-328264

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-24971 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] However, the cost of PEEK resin is about twice that of PPS resin, and its formability and availability are also worse than PPS. In addition, when connecting with the existing PPS ferrule, it is believed that the difference in thermal expansion coefficient, water absorption rate, etc. will affect the connection characteristics. In addition, the problem of introducing optical fiber after reflow soldering has not yet been solved.

[0012] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a ferrule for an optical connector or the like which can suppress the influence in the reflow process without using a special resin material.

[0013] Solutions for solving problems

[0014] In order to achieve the above-mentioned purpose, the first invention is a ferrule for an optical connector, characterized in that the ferrule has an optical fiber fixed inside and the front end side serves as a connecting end face, the ferrule has: a hole for inserting the optical fiber; and a pair of guide holes for inserting guide pins for positioning, the ferrule is composed of a resin composition obtained by adding a filler material including at least inorganic particles to a thermoplastic resin, and the shrinkage rate of the ferrule at 260°C×1 minute is less than 0.13%.

[0015] Preferably, the linear expansion coefficient of the resin composition is 3.0×10 -5 / ℃ below.

[0016] Preferably, the thermoplastic resin contains PPS resin as a main component, and the inorganic particles include spherical silica.

[0017] Preferably, the content of the inorganic particles in the resin composition is 60% by mass or more and 80% by mass or less.

[0018] Preferably, the particle size distribution D100 of the inorganic particles is less than 60 μm.

[0019] Also, the resin composition may include carbon black as carbon particles.

[0020] A recess may be formed on the outer surface of the ferrule on the side opposite to the side where the adhesive injection window is formed.

[0021] According to the first invention, since the shrinkage rate of the ferrule at 260° C.×1 minute is 0.13% or less, the ferrule does not shrink excessively even in the reflow process and the dimensional accuracy can be maintained.

[0022] In addition, if the linear expansion coefficient of the resin composition is 3.0×10 -5 / °C or less, dimensional deformation during heat treatment can be more reliably suppressed.

[0023] In addition, by using PPS resin as the main component, the same resin material as the existing ferrule material can be applied. In this case, if the inorganic particles are spherical silica, the moldability is good.

[0024] Moreover, when the content rate of the inorganic particle in a resin composition is 60 mass % or more and 80 mass % or less, high strength and dimensional accuracy can be obtained.

[0025] Likewise, by setting the particle size distribution D100 of the inorganic particles to 60 μm or less, high strength and dimensional accuracy can be obtained more reliably.

[0026] By including carbon black as carbon particles in the resin composition, internal defects such as foreign matter and the like become less noticeable.

[0027] In addition, by forming a recessed portion on the outer surface of the ferrule on the side opposite to the side where the adhesive injection window is formed, it is possible to suppress the imbalance of the upper and lower resin amounts during injection molding and make the flow of the resin during injection molding uniform. As a result, the ferrule can be molded with high dimensional accuracy.

[0028] A second invention is a method for manufacturing the ferrule according to the first invention, characterized by comprising a heat treatment step of performing heat treatment at 230° C. or higher and 260° C. or lower for 1 minute or longer after the ferrule is formed.

[0029] Preferably, the heat treatment process is performed in a low-oxygen or oxygen-free atmosphere.

[0030] According to the second invention, the heat shrinkage in the reflow process can be suppressed by heat-treating the ferrule whose dimensions are designed in advance in anticipation of the heat shrinkage at a temperature assuming the reflow process.

[0031] Furthermore, by performing the heat treatment step in a low-oxygen or oxygen-free atmosphere, it is possible to suppress changes in physical properties due to bonding of the resin with oxygen during heat treatment at a relatively high temperature, which is a normal heat treatment temperature for resins.

[0032] A third invention is an optical fiber ribbon with a ferrule using the ferrule of the first invention, wherein a plurality of optical fibers are inserted into each of the plurality of holes and the optical fibers are fixed to the ferrule with an adhesive.

[0033] According to the third invention, it is possible to obtain an optical fiber ribbon with a ferrule which is less susceptible to shrinkage during the reflow process.

[0034] A fourth invention relates to a method for manufacturing an optical fiber ribbon with a ferrule, characterized in that the optical fiber ribbon with a ferrule has an optical fiber fixed inside a ferrule for an optical connector whose front end side serves as a connection end face, the ferrule is composed of a resin composition obtained by adding a filler material including at least inorganic particles to a thermoplastic resin, the ferrule comprises: a plurality of holes for inserting the optical fiber; and a pair of guide holes for inserting guide pins for positioning, the manufacturing method comprises the following steps: heat treating the ferrule at a temperature of not less than 230° C. and not more than 260° C. for not less than 1 minute; inserting the optical fiber into the ferrule; injecting an adhesive from an adhesive injection window to fix the optical fiber to the ferrule; and polishing the front end face of the ferrule so that the optical fiber having a predetermined length or more protrudes from the end face of the ferrule.

[0035] The method may further include a step of performing a heat treatment at 230° C. to 260° C. for 1 minute or more after the polishing step. In this case, the optical fiber preferably projects from the end face of the ferrule by 5 μm or more after polishing and before heat treatment.

[0036] The method may further include a step of performing a heat treatment at 230° C. to 260° C. for 1 minute or more before the polishing step.

[0037] According to the fourth invention, it is possible to obtain an optical fiber ribbon with a ferrule which is less susceptible to shrinkage during the reflow process.

[0038] Furthermore, by making the tip of the optical fiber protrude from the ferrule end surface by a predetermined amount during polishing, the optical fiber core wire can be PC-connected even if the adhesive is pulled in due to shrinkage during heat treatment after polishing.

[0039] Furthermore, by performing heat treatment in a state where the optical fiber protrudes from the end face by a predetermined amount, and then performing polishing, the protrusion amount of the optical fiber from the ferrule can be made appropriate.

[0040] The fifth invention is a method for manufacturing an optical fiber ribbon with a ferrule, characterized in that the optical fiber ribbon with a ferrule has an optical fiber fixed inside a ferrule for an optical connector whose front end side serves as a connection end face, the ferrule is composed of a resin composition obtained by adding a filler material including at least inorganic particles to a thermoplastic resin, the ferrule comprises: a plurality of holes for inserting the optical fiber; and a pair of guide holes for inserting guide pins for positioning, the manufacturing method comprises the following steps: inserting the optical fiber into the ferrule; injecting adhesive from an adhesive injection window to fix the optical fiber to the ferrule; grinding the front end face of the ferrule so that the optical fiber having a length greater than a predetermined length protrudes from the end face of the ferrule; and after the grinding step, performing a heat treatment at a temperature of not less than 230° C. and not more than 260° C. for more than 1 minute.

[0041] In this case, it is preferable that the protrusion amount of the optical fiber from the end surface of the ferrule after polishing and before heat treatment is 5 μm or more.

[0042] According to the fifth invention, by making the tip of the optical fiber protrude from the ferrule end surface by a predetermined amount during polishing, the optical fiber core wire can be PC-connected even if the adhesive is pulled in due to shrinkage during heat treatment after polishing.

[0043] The sixth invention is a method for manufacturing an optical fiber ribbon with a ferrule, characterized in that the optical fiber ribbon with a ferrule has an optical fiber fixed inside a ferrule for an optical connector whose front end side serves as a connection end face, the ferrule is composed of a resin composition in which a filler material including at least inorganic particles is added to a thermoplastic resin, the ferrule comprises: a plurality of holes for inserting the optical fiber; and a pair of guide holes for inserting guide pins for positioning, the manufacturing method comprises the following steps: inserting the optical fiber into the ferrule; injecting adhesive from an adhesive injection window to fix the optical fiber to the ferrule; performing a heat treatment at a temperature of not less than 230°C and not more than 260°C for more than 1 minute; and after the heat treatment, polishing the front end face of the ferrule so that the optical fiber having a predetermined length or more protrudes from the end face of the ferrule.

[0044] According to the sixth invention, the optical fiber can be properly protruded from the ferrule by performing heat treatment in a state where the optical fiber protrudes from the end face by a predetermined amount and then performing polishing.

[0045] Effects of the Invention

[0046] According to the present invention, it is possible to provide a ferrule for an optical connector or the like which can suppress the influence in a reflow process without using a special resin material. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1A It is a perspective view showing the optical connector ferrule 1 .

[0048] Figure 1B It is a cross-sectional view of the optical connector ferrule 1 in the axial direction.

[0049] Figure 2 1 is a flowchart showing a manufacturing process of the optical connector ferrule 1 .

[0050] Figure 3A This is a cross-sectional view in the axial direction of the optical fiber ribbon with a ferrule in a state where the optical fiber 17 is fixed by the adhesive 19 .

[0051] Figure 3B This is an axial cross-sectional view of the optical fiber ribbon with the ferrule after the end surface of the optical ferrule is polished.

[0052] Figure 4It is a flowchart showing another manufacturing process of the optical connector ferrule 1 .

[0053] Figure 5A This is a cross-sectional view in the axial direction of the optical fiber ribbon with a ferrule in a state where the front end of the optical fiber 17 is protruded by grinding.

[0054] Figure 5B It is an axial cross-sectional view of the optical fiber ribbon with a ferrule after heat treatment.

[0055] Figure 6 It is a flowchart showing another manufacturing process of the optical connector ferrule 1 . DETAILED DESCRIPTION

[0056] Hereinafter, an optical connector ferrule according to an embodiment of the present invention will be described. Figure 1A 1 is a perspective view showing a ferrule 1 for an optical connector. Figure 1B The optical connector ferrule 1 is a member for fixing an optical fiber inside, and its front end side serves as a connection end face 7 of the optical fiber. The optical connector ferrule 1 can be used as a so-called MT connector (Mechanically Transferable Connector) having a guide hole 11.

[0057] An internal space 13 for accommodating the optical fiber is formed inside the optical connector ferrule 1. The internal space 13 passes through from the rear end to the front end of the optical connector ferrule 1. Figure 1B The right side of the optical fiber is the rear end side, and the side with the end face of the optical fiber exposed ( Figure 1B That is, Figure 1B The left-right direction is used as the front and rear end direction of the optical connector ferrule 1 (or the connection direction as the case may be).

[0058] The optical connector ferrule 1 is formed by, for example, injection molding, and is made of a PPS (polyphenylene sulfide) resin containing a filler (for example, inorganic fibers, fillers).

[0059] The inner space 13 is connected to the front end of the optical connector ferrule 1 to form a hole 9 for inserting the optical fiber. In addition, in this embodiment, a multi-core connector ferrule can be arranged and fixed with multiple optical fibers. That is, a plurality of holes 9 are arranged in parallel on the connection end surface 7.

[0060] In addition, the connection end surface 7 is a plane inclined relative to the connection direction. That is, a plurality of holes 9 are arranged on the inclined surface. In addition, a pair of guide holes 11 are provided on both sides of the hole 9. A guide pin or the like for positioning with the connection object is inserted into the guide hole 11. In addition, the inclined surface of the connection end surface 7 is not necessary, and may be perpendicular to the front and rear end directions, or may be a slightly curved surface.

[0061] An adhesive injection window 5 opening to the outside is formed on the upper surface of the optical connector ferrule 1. The adhesive injection window 5 communicates with the internal space 13, and the adhesive can be injected into the internal space 13 from the adhesive injection window 5.

[0062] In addition, a recess 15 is formed as needed on the outer surface (i.e., the lower surface) of the optical connector ferrule 1 on the opposite side to the side where the adhesive injection window 5 is formed. The recess 15 is formed at a predetermined depth relative to the outer surface and is not connected to the internal space 13. The hollowed volume of the recess 15 is formed to be substantially consistent with the volume of the space from the adhesive injection window 5 to the internal space 13, for example.

[0063] As described above, the optical connector ferrule 1 is formed by injection molding. That is, resin is injected into the cavity of the mold from a predetermined position to form a shape corresponding to the shape of the cavity. At this time, the molten resin flows from the injection position to the inside of the mold and fills the cavity.

[0064] For example, when injecting resin from the rear end side of the optical connector ferrule 1, since the hole 9 and the internal space 13 are arranged at the approximate center of the optical connector ferrule 1 in the vertical direction, the resin is divided at the upper and lower parts of the internal space 13 and flows toward the front end side. At this time, the adhesive injection window 5 is formed on the upper side of the internal space 13, so the flow of the resin is hindered. On the other hand, there is no adhesive injection window 5 on the lower side of the hole 9, so the fluid resistance of the resin becomes smaller than that on the upper side of the hole 9. With such a setting, an imbalance in the flow of the resin occurs above and below the hole 9, which becomes a major cause of the deterioration of the dimensional accuracy of the optical connector ferrule 1.

[0065] In this regard, by providing a recess 15 on the outer surface on the opposite side of the adhesive injection window 5, the resistance to the flow of the resin and the volume difference can be reduced in the upper and lower parts of the internal space 13, so that the upper and lower balance of the resin becomes good, and the dimensional accuracy of the optical connector ferrule 1 can be improved. In addition, the recess 15 is not essential.

[0066] Here, the optical connector ferrule 1 is composed of a resin composition obtained by adding a filler material including at least inorganic particles to a thermoplastic resin. The thermoplastic resin is not particularly limited, and polyphenylene sulfide (PPS) resin, polycarbonate (PC) resin, polyether sulfone (PES) resin, liquid crystal polymer (LCP), modified polyphenylene ether (PPE) resin, etc. can be used. From the perspective of dimensional stability, strength, and formability, it is desirable to preferably use PPS resin as the main component. The structure of the PPS resin can be a cross-linked type or a linear type, and its structure, molecular weight, etc. can be appropriately selected according to the characteristics required by the optical connector ferrule 1.

[0067] In addition, the linear expansion coefficient of the resin composition is preferably 3.0×10-5 This is because if the linear expansion coefficient is larger than this value, the relative position of the guide hole 11 and the hole 9 will shift due to the change in ambient temperature, and the increase in connection loss due to this shift will become non-negligible.

[0068] In addition, the content of inorganic particles in the resin composition is preferably 60% by mass or more and 80% by mass or less. In addition, as inorganic particles, particles of silica and calcium carbonate can be applied, but preferably spherical silica is included. By setting in this way, the thermal shrinkage and formability of the optical connector ferrule 1 can be stabilized. For example, if the inorganic particles are flattened, there will be hidden dangers of hindering the expansion and contraction of the surrounding resin and increasing anisotropy, but by making them spherical, such anisotropy can be suppressed.

[0069] In addition, it is preferred that the particle size distribution D100 (maximum particle size) of the inorganic particles is 60 μm or less. In particular, the cumulative 99% particle size D99 of the spherical silica particles is preferably 25 μm or less, more preferably 10 μm or less, and further preferably 1 μm or less. This can prevent the inclusion of coarse particles in the resin composition and prevent microscopic (local) composition imbalance. In addition, the particle size of the inorganic particles can be obtained, for example, by measuring the particle size distribution based on the laser diffraction scattering method.

[0070] Furthermore, the resin composition may include carbon black as carbon particles. In this way, the optical connector ferrule 1 can be colored black, and foreign matter inside the optical connector ferrule 1 is less noticeable, thereby improving the appearance.

[0071] Here, the shrinkage rate of the optical connector ferrule 1 in this embodiment at 260°C × 1 minute is 0.13% or less. For example, the change rate of the interval between the guide holes 11 before and after the heat treatment at 260°C × 1 minute is 0.13% or less. In addition, the shrinkage rate is calculated by (size before shrinkage - size after shrinkage) / size after shrinkage × 100%.

[0072] By doing so, the shrinkage of the optical connector ferrule 1 can be suppressed to a predetermined value or less even under the temperature condition of the normal substrate reflow process, that is, 230° C. to 260° C. The method of reducing the shrinkage rate in the reflow process will be described later.

[0073] Next, a method for manufacturing the optical connector ferrule 1 is described. As described above, the optical connector ferrule 1 is formed by injection molding. Next, after the optical connector ferrule 1 is formed, a heat treatment is performed at 230° C. to 260° C. for more than 1 minute in a heating furnace. In order to achieve greater stability, the heat treatment is preferably performed at 230° C. to 260° C. for more than 10 minutes.

[0074] Here, generally, the heat treatment (annealing) of thermoplastic resins is generally for the purpose of releasing internal stress during molding, etc. For non-crystalline resins, it is performed at a temperature slightly lower than the glass transition temperature Tg, and for crystalline resins, it is often performed at a temperature slightly higher than the glass transition temperature. On the other hand, if the melting point of the resin is increased, the resin softens and becomes unable to maintain its shape. Therefore, for example, the glass transition temperature of PPS resin, which is a crystalline resin, is about 90°C, so it is generally heat treated at a temperature of about Tg+20 to +30°C.

[0075] However, in the present embodiment, the heat treatment is performed for more than 1 minute at a set temperature of 230°C or more and 260°C or less, which is much higher than this temperature. For example, with respect to the melting point Tm=290°C of the PPS resin, the heat treatment condition is set to a temperature higher than (Tg+Tm) / 2. In this way, by heating at a temperature that cannot be used under the heat treatment conditions of the usual resin, the resin can be reliably heat-shrunk. In addition, the heat treatment temperature can be set according to the temperature of the predetermined reflow process.

[0076] Here, in the general annealing heat treatment of crystalline resin, the crystalline part and the non-crystalline part are mixed, and by increasing the temperature to about Tg+20 to 30°C, the crystallization of the non-crystalline part is promoted to stabilize it. In contrast, in the present embodiment, by heat treatment at a temperature closer to Tm than Tg, the crystalline part and the non-crystalline part move and shrink in a denser manner. By setting in this way, compared with the resin that is not subjected to the heat treatment of the present embodiment, the shrinkage amount in the subsequent reheating (reflow process) can be reduced.

[0077] In addition, the shrinkage caused by the heat treatment may reduce the interval between the guide holes 11, for example, but the shrinkage amount can be predicted in advance to set the dimensions during injection molding. That is, by obtaining data on the amount of heat shrinkage under predetermined heat treatment conditions in advance and designing the injection molding mold so that the target dimensions are achieved by the shrinkage, the required dimensions after the heat treatment can be ensured.

[0078] In addition, the heat treatment process is preferably carried out in a low-oxygen or oxygen-free atmosphere. For example, it is preferred to carry out the heat treatment in a nitrogen atmosphere or under reduced pressure. Similarly, in order to eliminate the influence of moisture, it is preferred to carry out the heat treatment in a dry atmosphere. Alternatively, it is also possible to maintain the temperature at a temperature of 100°C or above and dry it before rising to the heat treatment temperature, and then rise to a predetermined temperature. By setting it in this way, it is possible to suppress the physical property changes caused by the combination of the resin composition with oxygen and moisture at high temperatures.

[0079] Next, a method for producing an optical fiber ribbon with a ferrule in which optical fibers are fixed inside using the optical connector ferrule 1 will be described. Figure 2 As described above, the optical connector ferrule 1 is first injection molded and then heat treated at a set temperature of 230° C. to 260° C. for pre-shrinkage for 1 minute or more.

[0080] Next, the optical fiber is inserted from the rear end side of the optical connector ferrule 1. In this state, the adhesive is injected from the adhesive injection window 5 of the optical connector ferrule 1 to fix the optical fiber to the optical connector ferrule 1.

[0081] Figure 3A 1 is a cross-sectional view of the optical fiber ribbon 10 with a ferrule, in which the optical fiber 17 is fixed to the ferrule 1 for an optical connector by an adhesive 19. The optical fiber 17 has an inner glass optical fiber core and a resin layer formed around the inner glass optical fiber core. The resin layer near the front end of the optical fiber 17 is peeled off to expose the inner optical fiber core, and the optical fiber 17 is inserted into the hole 9. The hole 9 is smaller than the outer diameter of the resin layer, so the end face of the resin layer abuts against the tapered portion on the rear end side of the hole 9, thereby positioning the optical fiber 17.

[0082] In addition, the internal space 13 is composed of the following components in order from the rear end side of the optical connector ferrule 1: a first tapered portion, which functions as a guide when inserting the optical fiber 17, etc., and the diameter decreases toward the front end side; a second tapered portion, which abuts the above-mentioned resin layer and functions as an insertion guide for the optical fiber bare core, and the diameter decreases toward the front end side; and a hole 9, which is formed in a substantially identical manner to the front end.

[0083] When the adhesive 19 is injected from the adhesive injection window 5, the adhesive 19 is injected into the internal space 13. At this time, the adhesive injection window 5 has a sufficient opening area, so the adhesive can be easily injected. In addition, as the adhesive 19, for example, a thermosetting resin such as epoxy resin can be applied, but the type of ultraviolet curing resin is not particularly limited.

[0084] By curing the adhesive 19 in this state, the optical fiber 17 can be fixed to the optical connector ferrule 1. In addition, in this state, the front end of the optical fiber 17 is previously protruded from the connection end face 7. Figure 3B As shown, the connection end face 7 is polished together with the optical fiber 17. When the connectors are connected to each other, in order to make a PC connection, the end face of the optical fiber 17 is polished so that it protrudes slightly (about 1 to 3.5 μm) from the connection end face 7 after polishing. By the above operation, an optical fiber ribbon with a ferrule can be obtained.

[0085] Furthermore, in the above description, the method of fixing the optical fiber to the optical connector ferrule 1 which has been subjected to heat treatment in advance is shown, but the present invention is not limited to this. Figure 4 It is a diagram showing another manufacturing process of the optical fiber ribbon with a ferrule.

[0086] In the present embodiment, as described above, after the optical connector ferrule 1 is injection molded, the above-mentioned heat treatment A for pre-shrinkage is performed (at a set temperature of not less than 230° C. and not more than 260° C. for more than 1 minute), and then the optical fiber 17 is inserted into the optical connector ferrule 1 and fixed with the adhesive 19.

[0087] Figure 5A The figure shows the optical fiber ribbon 10 with a ferrule obtained by fixing the optical fiber 17 to the optical connector ferrule 1 with the adhesive 19. Different from the above-mentioned manufacturing process, the protruding length of the optical fiber 17 from the connection end face 7 is extended in advance in the state where the optical fiber 17 is fixed to the optical connector ferrule 1.

[0088] In this state, the optical fiber ribbon with ferrule is subjected to heat treatment B for more than 1 minute at a temperature of 230°C to 260°C. Here, in the optical fiber ribbon with ferrule 10, the shrinkage amount of the adhesive 19 is greater than that of the optical connector ferrule 1 during the above-mentioned heat treatment. In this case, Figure 5B As shown, due to the contraction of the adhesive 19, the optical fiber 17 is pulled rearward, and the front end of the optical fiber 17 is introduced into the optical connector ferrule 1.

[0089] After the heat treatment B, the front end face of the optical connector ferrule 1 is polished together with the optical fiber 17. As described above, the end face of the optical fiber 17 is polished so that it slightly protrudes (about 1 to 3.5 μm) from the connection end face 7 after polishing. By the above operation, the optical fiber ribbon 10 with a ferrule can be obtained.

[0090] Furthermore, the timing of grinding can be changed. Figure 6 FIG. 2 is a diagram showing another manufacturing process of an optical fiber ribbon with a ferrule. Figure 6 In the example shown, after the heat treatment A is performed, the adhesive 19 is injected from the adhesive injection window 5 to fix the optical fiber 17 to the optical connector ferrule 1. Then, before the above-mentioned heat treatment B for pre-shrinkage is performed, the front end surface of the optical connector ferrule 1 is polished so that the optical fiber 17 of a predetermined length or more protrudes from the end surface of the ferrule. For example, the protrusion amount of the optical fiber 17 from the end surface of the optical connector ferrule 1 after polishing and before the heat treatment is set to 5 μm or more.

[0091] Here, generally, the end face of the optical connector ferrule is polished with good precision by gradually reducing the particle size of the abrasive from rough polishing. In this case, in order to make the optical fiber protrude from the end face of the optical connector ferrule by more than 5 μm, for example, the abrasive particle size and polishing time of the abrasive used in the final polishing can be adjusted.

[0092] After polishing, the optical fiber ribbon with the ferrule is heat-treated at a temperature of 230°C to 260°C for 1 minute or more, from a state where the protrusion amount of the optical fiber 17 from the end face of the optical connector ferrule is constant with good accuracy. As described above, due to the shrinkage of the adhesive 19 caused by the heat treatment (difference in thermal shrinkage between the adhesive 19 and the optical connector ferrule 1), the tip of the optical fiber 17 is introduced into the interior of the optical connector ferrule 1. For example, by confirming the introduction amount in advance, the protrusion amount of the optical fiber 17 from the end face of the optical connector ferrule after introduction can be about 1 to 3.5 μm. For example, in the case where the introduction amount is about 8 μm due to the heat treatment, the optical fiber can be made to protrude about 10 μm from the end face of the optical connector ferrule by prior polishing.

[0093] As described above, according to this embodiment, the optical connector ferrule is subjected to a heat treatment equivalent to the reflow process before being mounted on the substrate to be sent to the reflow process, and is heat-shrunk in advance, so that the influence of shrinkage in the reflow process can be reduced. Therefore, the size after shrinkage due to reflow can be confirmed before being mounted on the substrate, so that the situation of dimensional defects due to shrinkage after the reflow process can be suppressed.

[0094] In addition, since there is no need to use special resin, the cost is low, and since the linear expansion coefficient does not vary significantly between optical connectors such as those made of PPS to be connected, it is possible to suppress an increase in light loss due to the ambient temperature.

[0095] Furthermore, since fine inorganic particles are appropriately added, deformation during heat treatment can be suppressed, thereby ensuring strength and dimensional stability.

[0096] Furthermore, in the manufacture of the optical fiber ribbon with a ferrule, by performing heat treatment after fixing the optical fiber 17 with the adhesive 19, not only the optical connector ferrule 1 but also the adhesive 19 can be shrunk in advance. Therefore, in the reflow process, the interval between the optical fibers 17 and the amount of protrusion from the end face of the optical connector ferrule 1 can be stabilized.

[0097] In addition, Figure 4 , Figure 6 In the process shown in , heat treatment A can be omitted. In this case, the same effect as heat treatment A (pre-shrinkage effect of optical connector ferrule 1) can be obtained by heat treatment B alone. However, when it is necessary to extend the heat treatment time of heat treatment A (for example, when 230°C to 260°C × 10 minutes or more is required to obtain a more stable effect), it is preferred to set the conditions of heat treatment B to 230°C to 260°C × 10 minutes or more, or to perform both heat treatment A and heat treatment B.

[0098] The embodiments of the present invention are described above with reference to the accompanying drawings, but the technical scope of the present invention is not limited to the above-mentioned embodiments. Those skilled in the art can clearly think of various modifications or amendments within the scope of the technical ideas described in the claims, and understand that these modifications or amendments certainly belong to the technical scope of the present invention.

[0099] Example

[0100] (Shrinkage)

[0101] The ferrule for optical connector was actually manufactured, and the shrinkage during the heat treatment for the reflow process was confirmed. PPS was used as the resin composition, and spherical silica was added. After injection molding, the shrinkage rate during the heat treatment A at 260°C × 1 minute in a heating furnace (measured by the distance between the guide holes (= 4.6mm)) was in the range of 0.15% to 2.0%. After they were cooled, they were again heat treated at 260°C × 1 minute in a heating furnace. The results showed that the shrinkage rates were all below 0.13% relative to the dimensions after heat treatment A.

[0102] Based on the above results, it can be seen that since the actual general reflow process is maintained for about 1 minute, if the optical connector ferrule without heat treatment A is put into the reflow process (for example, 260°C × 1 minute), it will produce greater shrinkage. However, if heat treatment A is performed, the shrinkage during the reflow process can be suppressed.

[0103] As described above, if the heat treatment A (preliminary heat treatment) is not performed, there is a risk that large shrinkage and deviation may occur in the reflow process.

[0104] On the other hand, by performing heat treatment A (preliminary heat treatment) in advance, the shrinkage rate in the subsequent heat treatment (reflow process) becomes smaller, and the deviation also becomes smaller. Therefore, by forming the ferrule in consideration of the shrinkage amount in heat treatment A, the reference size can be satisfied after shrinkage. In addition, by removing the ferrule whose size exceeds the reference after heat treatment A, it is possible to suppress the ferrule from exceeding the reference size after the subsequent reflow process.

[0105] In addition, the shrinkage rate based on time was evaluated by changing the time of the heat treatment A. As a result, when the time was 10 minutes or more, the shrinkage rate hardly changed and became approximately constant. As described above, the effect of the pre-heat treatment can be fully confirmed even if the heat treatment A is 1 minute, but in order to obtain a more stable pre-heat treatment effect, it is preferred that the heat treatment A be set to 10 minutes or more.

[0106] (Introduction amount)

[0107] The optical fiber was fixed to the optical connector ferrule after heat treatment A with an adhesive and polished to a protrusion amount of 1 to 3.5 μm. Then, heat treatment B was performed at 260° C. for 1 minute in a heating furnace, and the amount of optical fiber introduced after heat treatment B was evaluated.

[0108] As a result, the lead-in amount differs depending on the position of the optical fiber (hole), with the lead-in amount being about 4 to 6 μm on the end side in the parallel direction (the side close to the guide hole) and 6 to 10 μm near the center in the width direction. This is believed to be because the center portion away from the wall surface of the internal space of the optical connector ferrule is more susceptible to the shrinkage caused by the adhesive. Therefore, by considering the lead-in amount based on the position and polishing in advance in a manner that gradually increases the protrusion amount of the optical fiber in the center portion, the protrusion amount of the front end of the optical fiber after heat treatment B can be within a predetermined range.

[0109] In addition, even if the heat treatment A is not performed in advance and only the heat treatment B is performed, the same effect can be obtained. For example, the optical fiber is fixed to the optical connector ferrule that has not been subjected to the heat treatment A by using an adhesive, and is polished so that the protrusion amount becomes 1 to 3.5 μm. Then, if a heat treatment is performed at 260°C × 1 minute in a heating furnace, an effect almost equivalent to that of performing the heat treatment A and the heat treatment B can be obtained.

[0110] Description of reference numerals:

[0111] 1………Ferrules for optical connectors

[0112] 5… Adhesive injection window

[0113] 7………Connection end face

[0114] 9...hole

[0115] 11…………Guide hole

[0116] 13…Interior Space

[0117] 15………concave part

[0118] 17...Optical Fiber

[0119] 19… Adhesive

Claims

1. A ferrule for an optical connector, characterized in that: The ferrule has an optical fiber fixed inside and a front end side serving as a connection end face, and the ferrule includes: a hole for inserting an optical fiber; and A pair of guide holes for inserting guide pins for positioning. The ferrule is composed of a resin composition obtained by adding a filler including at least inorganic particles to a thermoplastic resin. The shrinkage rate of the ferrule at 260° C.×1 minute was 0.13% or less.

2. The ferrule according to claim 1, characterized in that The linear expansion coefficient of the resin composition is 3.0×10 -5 / ℃ below.

3. The ferrule according to claim 1, characterized in that The thermoplastic resin contains PPS resin as a main component, and the inorganic particles contain spherical silica.

4. The ferrule according to claim 1, characterized in that The content of the inorganic particles in the resin composition is 60% by mass or more and 80% by mass or less.

5. The ferrule according to claim 1, characterized in that: The particle size distribution D100 of the inorganic particles is less than 60 μm.

6. The ferrule according to claim 1, characterized in that Furthermore, the resin composition includes carbon black as carbon particles.

7. The ferrule according to claim 1, characterized in that A recessed portion is formed on the outer surface of the ferrule on the side opposite to the side where the adhesive injection window is formed.

8. A method for manufacturing a ferrule according to any one of claims 1 to 7, characterized in that: have: After the ferrule is formed, a heat treatment step is performed at 230° C. to 260° C. for 1 minute or more.

9. The method for manufacturing a ferrule according to claim 8, characterized in that: The heat treatment process is performed in a low-oxygen or oxygen-free atmosphere.

10. An optical fiber ribbon with a ferrule, characterized in that: Using the ferrule according to any one of claims 1 to 7, Optical fibers are inserted into the plurality of holes respectively, and the optical fibers are fixed to the ferrule using an adhesive.

11. A method for manufacturing an optical fiber ribbon with a ferrule, characterized in that: The optical fiber ribbon with ferrule has an optical fiber fixed inside a ferrule for an optical connector whose front end side serves as a connection end face. The ferrule is composed of a resin composition obtained by adding a filler including at least inorganic particles to a thermoplastic resin. The ferrule has: a plurality of holes for inserting the optical fibers; and A pair of guide holes for inserting guide pins for positioning. The manufacturing method comprises the following steps: heat treating the ferrule at a temperature of 230°C to 260°C for more than 1 minute; inserting an optical fiber into the ferrule; Injecting adhesive from the adhesive injection window to fix the optical fiber to the ferrule; as well as The front end surface of the ferrule is polished so that a predetermined length of the optical fiber protrudes from the end surface of the ferrule.

12. The method for manufacturing an optical fiber ribbon with a ferrule according to claim 11, characterized in that: The following processes are available: After the polishing step, heat treatment is performed at 230° C. or higher and 260° C. or lower for 1 minute or longer.

13. The method for manufacturing an optical fiber ribbon with a ferrule according to claim 12, characterized in that: The protrusion amount of the optical fiber from the end surface of the ferrule after polishing and before heat treatment is set to 5 μm or more.

14. The method for manufacturing an optical fiber ribbon with a ferrule according to claim 11, characterized in that: The following processes are available: Before the polishing step, heat treatment is performed at 230° C. or higher and 260° C. or lower for 1 minute or longer.

15. A method for manufacturing an optical fiber ribbon with a ferrule, characterized in that: The optical fiber ribbon with ferrule has an optical fiber fixed inside a ferrule for an optical connector whose front end side serves as a connection end face. The ferrule is composed of a resin composition obtained by adding a filler including at least inorganic particles to a thermoplastic resin. The ferrule has: a plurality of holes for inserting the optical fibers; and A pair of guide holes for inserting guide pins for positioning. The manufacturing method comprises the following steps: inserting the optical fiber into the ferrule; Injecting adhesive from the adhesive injection window to fix the optical fiber to the ferrule; Grinding the front end surface of the ferrule so that the optical fiber having a predetermined length or more protrudes from the end surface of the ferrule; as well as After the polishing step, heat treatment is performed at 230° C. or higher and 260° C. or lower for 1 minute or longer.

16. The method for manufacturing an optical fiber ribbon with a ferrule according to claim 15, characterized in that: The protrusion amount of the optical fiber from the end surface of the ferrule after polishing and before heat treatment is set to 5 μm or more.

17. A method for manufacturing an optical fiber ribbon with a ferrule, characterized in that: The optical fiber ribbon with ferrule has an optical fiber fixed inside a ferrule for an optical connector whose front end side serves as a connection end face. The ferrule is composed of a resin composition obtained by adding a filler including at least inorganic particles to a thermoplastic resin. The ferrule has: a plurality of holes for inserting the optical fibers; and A pair of guide holes for inserting guide pins for positioning. The manufacturing method comprises the following steps: inserting the optical fiber into the ferrule; Injecting adhesive from the adhesive injection window to fix the optical fiber to the ferrule; Performing heat treatment at 230° C. or higher and 260° C. or lower for 1 minute or longer; and After the heat treatment, the front end surface of the ferrule is polished so that a predetermined length of the optical fiber protrudes from the end surface of the ferrule.

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