Ferrules, method for manufacturing ferrules, fiber ribbons with ferrules, and method for manufacturing fiber ribbons with ferrules

Abstract

To provide a ferrule for an optical connector which can suppress an influence in a solder reflow step without using a special resin material.SOLUTION: A ferrule 1 for an optical connector is a member where an optical fiber is fixed therein, and its tip side acts as a connection end face 7 of the optical fiber. The ferrule 1 for the optical connector is, for example, molded by injection molding, and is formed of a PPS (polyphenylene sulfide) resin containing a filler (for example, inorganic fiber and fiber). An internal space 13 communicates with the tip side of the ferrule 1 for the optical connector, and acts as a hole 9 to which the optical fiber is inserted. Here, a shrinkage rate at 260°C for 1 minute of the ferrule 1 for the optical connector is 0.13% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ferrule for an optical connector in which an optical fiber is fixed inside, and the like.

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 having holes into which a pair of guide pins can be inserted on the connection end face side, 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. For this reason, a window for injecting the adhesive is formed in a part of the ferrule, and with the optical fiber disposed inside, the optical fiber is fixed to the ferrule by injecting the adhesive from the injection window (for example, Patent Documents 1 and 2).

[0003] In recent years, the demand for applying optical wiring to an electric circuit board has been increasing. In the manufacturing process of an electric circuit board, there is a process called solder reflow in which the product is placed at a high temperature of 230 to 260°C, and solder reflow resistance is also required for the ferrule which is an optical connection component. However, in a conventional MT ferrule, it thermally contracts with respect to the solder reflow temperature (230 to 260°C), and it is impossible to maintain the dimensional accuracy required for the ferrule. Further, due to the difference in thermal expansion between the optical fiber built in the ferrule and the epoxy-based adhesive that adheres the optical fiber, after the solder reflow is introduced, the end face of the optical fiber is pulled into the ferrule, resulting in a state where so-called PC (Physical Contact) connection cannot be achieved.

[0004] On the other hand, a method of imparting heat resistance by changing the base resin of the material from commonly used PPS (polyphenylene sulfide) to PEEK (polyether ether ketone resin) has also been proposed (Patent Document 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, PEEK resin generally has a cost about twice that of PPS resin, and its moldability and availability are also inferior to those of PPS. In addition, when connected to a conventional PPS ferrule, the difference in the coefficient of thermal expansion, water absorption rate, etc. may affect the connection characteristics. Also, the problem of the pulling-in of the optical fiber after the solder reflow process has not been solved yet.

[0007] The present invention has been made in view of such problems, and an object thereof is to provide a ferrule for an optical connector that can suppress the influence in the solder reflow process without using a special resin material.

Means for Solving the Problems

[0008] In order to achieve the above-described object, a first invention is a ferrule for an optical connector in which an optical fiber is fixed inside and the tip side serves as a connection end face, the ferrule including a hole into which the optical fiber is inserted, a pair of guide holes into which positioning guide pins are inserted, and an adhesive injection window that opens to the outside, and the ferrule is Based on PPS resin as the main component composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin, At a temperature higher than the glass transition temperature of PPS resin and is characterized in that the shrinkage rate of the ferrule at 260°C for 1 minute is 0.13% or less.

[0009] It is desirable that the linear expansion coefficient of the resin composition is 3.0×10 -5 / °C or less.

[0010] Before It is desirable that the inorganic particles include spherical silica.

[0011] It is desirable that the content of the inorganic particles in the resin composition is 60% by mass or more and 80% by mass or less.

[0012] The particle size distribution D of the inorganic particles 100 is desirably 60 μm or less.

[0013] Furthermore, the resin composition may contain carbon black as carbon particles.

[0014] Of the ferrule An adhesive injection window opening to the outside, and A recess may be formed on the outer surface on the side opposite to the side where the adhesive injection window is formed.

[0015] According to the present invention, since the shrinkage rate of the ferrule at 260 °C for 1 minute is 0.13% or less, it does not shrink excessively even in the reflow process, and dimensional accuracy can be maintained.

[0016] Also, 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.

[0017] Also, by using a PPS resin as the main component, the same resin material as the conventional ferrule material can be applied. At this time, if the inorganic particles are spherical silica, the moldability is good.

[0018] Also, if the content of the inorganic particles in the resin composition is 60% by mass or more and 80% by mass or less, high strength and dimensional accuracy can be obtained.

[0019] Similarly, by setting the particle size distribution D of the inorganic particles 100 to 60 μm or less, high strength and dimensional accuracy can be more reliably obtained.

[0020] By including carbon black as carbon particles in the resin composition, internal defects such as foreign matter become less noticeable.

[0021] Also, by forming a recess on the outer surface opposite to the side where the ferrule's adhesive injection window is formed, it is possible to suppress the imbalance in the amount of resin above and below during injection molding and to equalize the resin flow during injection molding. As a result, the ferrule can be molded with high dimensional accuracy.

[0022] A second invention is a method for manufacturing a ferrule according to the first invention, characterized in that after molding the ferrule, At a temperature higher than the glass transition temperature of PPS resin it has a heat treatment step at 230°C or higher and 260°C or lower for 1 minute or more.

[0023] It is desirable that the heat treatment step be performed in a low-oxygen or oxygen-free atmosphere.

[0024] According to the second invention, by performing heat treatment on the ferrule whose dimensions are designed in anticipation of heat shrinkage at a temperature assuming reflow soldering, it is possible to suppress heat shrinkage in the reflow process.

[0025] Also, by performing the heat treatment step in a low-oxygen or oxygen-free atmosphere, it is possible to suppress physical property changes due to the combination of the resin and oxygen in heat treatment, which is a considerably high temperature as the heat treatment temperature of ordinary resins.

[0026] A third invention is a fiber ribbon with a ferrule using the ferrule according to the first invention, characterized in that a plurality of optical fibers are respectively inserted into the plurality of holes and fixed to the ferrule with an adhesive.

[0027] According to the third invention, it is possible to obtain a fiber ribbon with a ferrule that is less affected by shrinkage in the reflow process.

[0028] The fourth invention is a method for manufacturing a fiber ribbon with a ferrule in which an optical fiber is fixed inside a ferrule for an optical connector whose tip side is a connection end face, wherein the ferrule is Based on PPS resin as the main component composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin, and includes a plurality of holes into which the optical fiber is inserted and a pair of guide holes into which positioning guide pins are inserted. The ferrule is At a temperature higher than the glass transition temperature of PPS resin subjected to a heat treatment at 230°C or higher and 260°C or lower for 1 minute or more, a step of inserting the optical fiber into the ferrule, and , Before a step of fixing the optical fiber to the ferrule, and a step of polishing the tip end face of the ferrule to project the optical fiber by a predetermined length or more from the end face of the ferrule. A method for manufacturing a fiber ribbon with a ferrule, characterized by comprising the steps.

[0029] After the polishing step, a step of performing a heat treatment at 230°C or higher and 260°C or lower for 1 minute or more may be provided. In this case, it is desirable that the protruding amount of the optical fiber from the end face of the ferrule before the heat treatment after polishing is 5 μm or more.

[0030] Before the polishing step, a step of performing a heat treatment at 230°C or higher and 260°C or lower for 1 minute or more may be provided.

[0031] According to the fourth invention, a fiber ribbon with a ferrule that is less affected by shrinkage in the reflow process can be obtained.

[0032] Also, by protruding the tip of the optical fiber from the ferrule end face by a predetermined amount in advance during polishing, even if drawing occurs due to shrinkage of the adhesive during the heat treatment after polishing, it becomes possible to perform PC connection of the optical fiber core wire.

[0033] Also, by performing heat treatment with the optical fiber protruding from the end face by a predetermined amount and then performing polishing, the protruding amount of the optical fiber from the ferrule can be made appropriate.

[0034] The fifth invention is a method for manufacturing a fiber ribbon with a ferrule in which an optical fiber is fixed inside a ferrule for an optical connector whose tip side is a connection end face, and the ferrule is Based on PPS resin as the main component composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin, and includes a plurality of holes into which the optical fiber is inserted and a pair of guide holes into which positioning guide pins are inserted, and a step of inserting the optical fiber into the ferrule , Before a step of fixing the optical fiber to the ferrule, a step of polishing the tip end face of the ferrule to project the optical fiber by a predetermined length or more from the end face of the ferrule, and after the polishing step, At a temperature higher than the glass transition temperature of PPS resin a step of performing a heat treatment at 230°C or higher and 260°C or lower for 1 minute or more, and is a method for manufacturing a fiber ribbon with a ferrule, characterized by comprising the above steps.

[0035] In this case, it is desirable that the protruding amount of the optical fiber from the end face of the ferrule after polishing and before heat treatment is 5 μm or more.

[0036] According to the fifth invention, by protruding the tip of the optical fiber from the ferrule end face by a predetermined amount in advance during polishing, even if drawing occurs due to shrinkage of the adhesive during the heat treatment after polishing, it is possible to perform PC connection of the optical fiber core wire.

[0037] The sixth invention is a method for manufacturing a fiber ribbon with a ferrule in which an optical fiber is fixed inside a ferrule for an optical connector whose tip side is a connection end face, and the ferrule is Based on PPS resin as the main component composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin, and includes a plurality of holes into which the optical fiber is inserted and a pair of guide holes into which positioning guide pins are inserted, and a step of inserting the optical fiber into the ferrule , Before a step of fixing the optical fiber to the ferrule, At a temperature higher than the glass transition temperature of PPS resinA method for manufacturing a fiber ribbon with a ferrule, comprising: a step of performing a heat treatment at a temperature of 230°C or higher and 260°C or lower for 1 minute or more; and after the heat treatment, a step of polishing the tip surface of the ferrule to project the optical fiber by a predetermined length or more from the end surface of the ferrule.

[0038] According to the sixth invention, by performing a heat treatment with the optical fiber protruding by a predetermined amount from the end surface and then performing polishing, the protruding amount of the optical fiber from the ferrule can be made appropriate.

Effect of the Invention

[0039] According to the present invention, it is possible to provide a ferrule for an optical connector or the like that can suppress the influence in the solder reflow process without using a special resin material.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiment for Carrying Out the Invention

[0041] Hereinafter, a ferrule for an optical connector according to an embodiment of the present invention will be described. FIG. 1(a) is a perspective view showing a ferrule 1 for an optical connector, and FIG. 1(b) is a cross-sectional view. The ferrule 1 for an optical connector is a member in which an optical fiber is fixed inside, and the tip side serves as the connection end face 7 of the optical fiber. The ferrule 1 for an optical connector can be used for a so-called MT connector (Mechanically Transferable Connector) having a guide hole 11.

[0042] An internal space 13 for accommodating an optical fiber is formed inside the ferrule 1 for an optical connector. The internal space 13 penetrates from the rear end to the front end of the ferrule 1 for an optical connector. Note that, with the insertion side of the optical fiber in the ferrule 1 for an optical connector (the right side in FIG. 1(b)) as the rear end side and the side where the end face of the optical fiber is exposed (the left side in FIG. 1(b)) as the front end side. That is, the left-right direction in FIG. 1(b) is the front-rear direction (or in some cases, the connection direction) of the ferrule 1 for an optical connector.

[0043] Note that the ferrule 1 for an optical connector is formed, for example, by injection molding and is made of a PPS (polyphenylene sulfide) resin containing a filler (for example, inorganic fiber or filler).

[0044] The internal space 13 communicates with the front end side of the ferrule 1 for an optical connector to form a hole 9 through which an optical fiber is inserted. In this embodiment, it is a ferrule for a multi-core connector in which a plurality of optical fibers can be provided and fixed together. That is, a plurality of holes 9 are provided side by side on the connection end face 7.

[0045] Also, the connection end face 7 is a plane inclined with respect to the connection direction. That is, the plurality of holes 9 are arranged on the inclined plane. 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 target is inserted into the guide hole 11. Note that the inclined plane of the connection end face 7 is not necessarily essential and may be perpendicular to the front-rear direction, or may be a somewhat curved surface.

[0046] On the upper surface of the ferrule 1 for an optical connector, an adhesive injection window 5 that opens to the outside is formed. The adhesive injection window 5 communicates with the internal space 13, and an adhesive can be injected from the adhesive injection window 5 into the internal space 13.

[0047] Also, on the outer surface (i.e., the lower surface) on the side opposite to where the adhesive injection window 5 of the ferrule 1 for an optical connector is formed, a recess 15 is formed as needed. The recess 15 is formed at a predetermined depth with respect to the outer surface and is not connected to the internal space 13. The volume of the cutout of the recess 15 is formed to substantially match, for example, the volume of the space from the adhesive injection window 5 to the internal space 13.

[0048] As described above, the ferrule 1 for an optical connector is formed by injection molding. That is, resin is injected into the cavity of the mold from a predetermined position, and a shape corresponding to the shape of the cavity is formed. At this time, the molten resin flows through the inside of the mold from the injection position and fills the cavity.

[0049] For example, when resin is injected from the rear end side of the ferrule 1 for an optical connector, since the hole 9 and the internal space 13 are arranged substantially at the center in the vertical direction of the ferrule 1 for an optical connector, the resin is divided above and below the internal space 13 and flows toward the front end side. At this time, since the adhesive injection window 5 is formed above the internal space 13, the flow of the resin is inhibited. On the other hand, since there is no adhesive injection window 5 below the hole 9, the fluid resistance of the resin is smaller compared to the upper side of the hole 9. Thus, when an imbalance in the resin flow occurs above and below the hole 9, it becomes a factor in the deterioration of the dimensional accuracy of the ferrule 1 for an optical connector.

[0050] On the other hand, by providing the recess 15 on the outer surface on the opposite side of the adhesive injection window 5, the resistance and volume difference of the resin flow can be reduced above and below the internal space 13, so that the balance of the resin in the vertical direction becomes good, and the dimensional accuracy of the ferrule 1 for an optical connector can be improved. Note that the recess 15 is not essential.

[0051] Here, the ferrule 1 for an optical connector is composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin. The thermoplastic resin is not particularly limited, but polyphenylene sulfide (PPS) resin, polycarbonate (PC) resin, polyethersulfone (PES) resin, liquid crystal polymer (LCP), modified polyphenylene ether (PPE) resin, etc. are applicable, and from the viewpoints of dimensional stability, strength, moldability, etc., it is desirable to mainly contain PPS resin. The PPS resin may have a crosslinked structure or a linear structure, and its structure, molecular weight, etc. can be appropriately selected and used according to the characteristics required for the ferrule 1 for an optical connector.

[0052] In addition, the linear expansion coefficient of the resin composition is preferably 3.0×10 -5 / °C or less. If the linear expansion coefficient is greater than this, the relative positions of the guide hole 11 and the hole 9 will shift due to changes in the environmental temperature, and the increase in connection loss due to this shift will become non-negligible.

[0053] Also, the content of the inorganic particles in the resin composition is preferably 60% by mass or more and 80% by mass or less. As the inorganic particles, silica or calcium carbonate particles are applicable, but it is desirable to contain spherical silica. By doing so, the thermal shrinkage and moldability of the ferrule 1 for an optical connector can be stabilized. For example, when the inorganic particles have a flat shape, the expansion and contraction of the surrounding resin are hindered, and there is a risk of increasing anisotropy, but being spherical can suppress such anisotropy.

[0054] Also, the particle size distribution D 100 (maximum particle diameter) of the inorganic particles is preferably 60 μm or less. In particular, the cumulative 99% particle diameter D 99It is preferably 25 μm or less, more preferably 10 μm or less, and still more preferably 1 μm or less. This can prevent coarse particles from being contained in the resin composition and prevent the deviation of the microscopic (local) composition. The particle diameter of the inorganic particles can be obtained, for example, from the measurement of the particle diameter distribution by the laser diffraction / scattering method.

[0055] Furthermore, the resin composition may contain carbon black as carbon particles. By doing so, the ferrule 1 for an optical connector can be colored black, and foreign matters inside the ferrule 1 for an optical connector are less likely to be noticeable, so the appearance is excellent.

[0056] Here, the shrinkage rate of the ferrule 1 for an optical connector in this embodiment at 260 °C for 1 minute is 0.13% or less. For example, the change rate of the pitch between the guide holes 11 before and after the heat treatment at 260 °C for 1 minute is 0.13% or less. The shrinkage rate is calculated by (dimension before shrinkage - dimension after shrinkage) / dimension after shrinkage × 100%.

[0057] By doing so, even at a temperature of 230 °C to 260 °C, which is the temperature condition of the reflow process of a normal substrate, the shrinkage amount of the ferrule 1 for an optical connector can be suppressed to a predetermined value or less. The method of reducing the shrinkage rate in the reflow process will be described later.

[0058] Next, the manufacturing method of the ferrule 1 for an optical connector will be described. As described above, the ferrule 1 for an optical connector is molded by injection molding. Next, after the ferrule 1 for an optical connector is molded, heat treatment is performed at 230 °C or higher and 260 °C or lower for 1 minute or more using a heating furnace. In order to make it more stable, it is desirable to perform heat treatment at 230 °C or higher and 260 °C or lower for 10 minutes or more.

[0059] Here, usually, the heat treatment (annealing) of a thermoplastic resin is generally for the purpose of releasing internal stress during molding, etc. For an amorphous resin, it is carried out at a temperature slightly lower than the glass transition temperature Tg, and for a crystalline resin, it is often carried out at a temperature slightly higher than the glass transition temperature. On the other hand, when the temperature is raised to the melting point of the resin, the resin softens and the shape cannot be maintained. Therefore, for example, in the case of PPS resin which is a crystalline resin and has a glass transition temperature of about 90 °C, it is common to perform heat treatment at a temperature of about Tg + 20 to +30 °C.

[0060] However, in this embodiment, heat treatment is carried out at a set temperature of 230 °C or higher and 260 °C or lower, which is much higher than that, for 1 minute or more. For example, with respect to the melting point Tm of PPS resin being 290 °C, the heat treatment conditions are set at a temperature higher than (Tg + Tm) / 2. By heating at a temperature that is impossible under normal resin heat treatment conditions in this way, the resin can be surely thermally shrunk. Note that the heat treatment temperature may be set according to the temperature of the planned reflow process.

[0061] Here, in the general annealing heat treatment of a crystalline resin, the crystalline part and the amorphous part are mixed, and by raising the temperature to about Tg + 20 to 30 °C, the crystallization of the amorphous part is promoted and stabilized. In contrast, in this embodiment, by performing heat treatment at a temperature closer to Tm rather than Tg, the crystalline part and the amorphous part move to become denser and shrinkage occurs. By doing so, the shrinkage amount in the subsequent re-heating (reflow process) can be reduced compared to the resin without performing the heat treatment of this embodiment.

[0062] Note that due to the shrinkage by heat treatment, for example, the pitch between the guide holes 11 becomes smaller, but the dimensions at the time of injection molding are set in anticipation of this shrinkage amount. That is, by obtaining data on the thermal shrinkage amount under predetermined heat treatment conditions in advance and designing the injection molding die so as to achieve the target dimensions due to this shrinkage, the required dimensions after heat treatment can be ensured.

[0063] Incidentally, the heat treatment process is preferably carried out in a low-oxygen or oxygen-free atmosphere. For example, it is desirable to perform the heat treatment in a nitrogen atmosphere or under reduced pressure conditions. Similarly, in order to exclude the influence of moisture, it is desirable to perform the heat treatment in a dry atmosphere. Also, before raising the heat treatment temperature, it may be held at a temperature of 100 °C or higher to dry and then raised to a predetermined temperature. By doing so, it is possible to suppress the bonding of the resin composition with oxygen at high temperatures and the change in physical properties due to moisture.

[0064] Next, a method for manufacturing a fiber ribbon with a ferrule in which an optical fiber is fixed inside using the ferrule 1 for an optical connector will be described. FIG. 2 is a diagram showing the manufacturing process of the fiber ribbon with a ferrule. As described above, first, the ferrule 1 for an optical connector is injection-molded, and then heat treatment is performed at a set temperature of 230 °C or higher and 260 °C or lower for 1 minute or more for pre-shrinkage.

[0065] Next, an optical fiber is inserted from the rear end side of the ferrule 1 for an optical connector. In that state, an adhesive is injected through the adhesive injection window 5 of the ferrule 1 for an optical connector to fix the optical fiber to the ferrule 1 for an optical connector.

[0066] FIG. 3(a) is a cross-sectional view showing a fiber ribbon 10 with a ferrule in which an 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 bare core and a resin layer formed around it. The resin layer near the tip of the optical fiber 17 is peeled off, the inner optical fiber bare core is exposed, and it is inserted into the hole 9. Since the hole 9 is smaller than the outer diameter of the resin layer, the end face of the resin layer abuts against the tapered portion on the rear end side of the hole 9 to position the optical fiber 17.

[0067] Incidentally, the internal space 13 functions as a guide when inserting the optical fiber 17 etc. in order from the rear end side of the ferrule 1 for an optical connector, and includes a tapered portion that tapers toward the tip side, and the resin layer described above abuts against it and functions as a guide for inserting the optical fiber bare core, a tapered portion that tapers toward the tip side, and a hole 9 formed with substantially the same diameter up to the tip.

[0068] 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, since the adhesive injection window 5 has a sufficient opening area, the injection of the adhesive is easy. As the adhesive 19, for example, a thermosetting resin such as an epoxy resin can be applied, but the type is not particularly limited, such as an ultraviolet curable resin.

[0069] By curing the adhesive 19 in this state, the optical fiber 17 can be fixed to the ferrule 1 for an optical connector. In this state, the tip of the optical fiber 17 is made to protrude from the connection end face 7. Finally, the connection end face 7 is polished together with the optical fiber 17. Since PC connection is performed when the connectors are connected to each other, polishing is performed so that the end face of the optical fiber 17 slightly (about 1 to 3.5 μm) protrudes from the connection end face 7 after polishing. Thus, a fiber ribbon with a ferrule can be obtained.

[0070] In the above description, a method of fixing an optical fiber to the ferrule 1 for an optical connector that has been heat-treated in advance has been shown, but it is not limited to this. FIG. 4 is a diagram showing another manufacturing process of a fiber ribbon with a ferrule.

[0071] In the present embodiment, as described above, after the ferrule 1 for an optical connector is injection-molded, the above-described heat treatment A for pre-shrinkage is performed, and then the optical fiber 17 is inserted into the ferrule 1 for an optical connector and fixed with the adhesive 19.

[0072] FIG. 5(a) is a diagram showing a fiber ribbon with a ferrule 10 in which the optical fiber 17 is fixed to the ferrule 1 for an optical connector with the adhesive 19. Different from the above-described manufacturing process, in a state where the optical fiber 17 is fixed to the ferrule 1 for an optical connector, the protruding length of the optical fiber 17 from the connection end face 7 is made longer.

[0073] In this state, the ferrule-attached fiber ribbon is subjected to a heat treatment B at 230°C or higher and 260°C or lower for 1 minute or more. Here, in the ferrule-attached fiber ribbon 10, in the above heat treatment, the shrinkage amount of the adhesive 19 is larger than that of the ferrule 1 for an optical connector. In this case, as shown in Fig. 5(b), due to the shrinkage of the adhesive 19, the optical fiber 17 is pulled backward, and the tip of the optical fiber 17 is drawn into the ferrule 1 for an optical connector.

[0074] After such a heat treatment B, the front end face of the ferrule 1 for an optical connector is polished together with the optical fiber 17. As described above, the polishing is performed so that the end face of the optical fiber 17 slightly protrudes (about 1 to 3.5 μm) from the connection end face 7 after polishing. Thus, the ferrule-attached fiber ribbon 10 can be obtained.

[0075] Note that the timing of polishing may be changed. Fig. 6 is a diagram showing another manufacturing process of the ferrule-attached fiber ribbon. In the example shown in Fig. 6, after performing the heat treatment A, the adhesive 19 is injected from the adhesive injection window 5, and the optical fiber 17 is fixed to the ferrule 1 for an optical connector. Then, before performing the above-described heat treatment B for pre-shrinkage, the front end face of the ferrule 1 for an optical connector is polished to protrude the optical fiber 17 by a length equal to or longer than a predetermined length from the end face of the ferrule. For example, the protruding amount of the optical fiber 17 from the end face of the ferrule 1 for an optical connector after polishing and before heat treatment is set to 5 μm or more.

[0076] Here, usually, the polishing of the end face of the ferrule for an optical connector is performed with high precision by stepping from rough polishing and reducing the particle size of the abrasive. At this time, in order to protrude the optical fiber by 5 μm or more from the end face of the ferrule for an optical connector, for example, it can be achieved by adjusting the abrasive grain particle size and polishing time of the abrasive used in the last buff polishing.

[0077] After polishing, from a state where the protruding amount of the optical fiber 17 from the end face of the ferrule for an optical connector is accurately made constant, heat treatment of the fiber ribbon with a ferrule is performed under the conditions of 230°C or higher and 260°C or lower for 1 minute or more. As described above, due to the shrinkage of the adhesive 19 by heat treatment (the difference in thermal shrinkage between the adhesive 19 and the ferrule 1 for an optical connector), the tip of the optical fiber 17 is drawn into the inside of the ferrule 1 for an optical connector. For example, by checking this drawing amount in advance, the protruding amount of the optical fiber 17 from the end face of the ferrule for an optical connector after drawing can be set to about 1 to 3.5 μm. For example, when there is a drawing amount of about 8 μm due to heat treatment, the optical fiber may be protruded about 10 μm from the end face of the ferrule for an optical connector by prior polishing.

[0078] As described above, according to the present embodiment, before being mounted on the substrate sent to the reflow process, heat treatment corresponding to the reflow process is performed in advance on the ferrule for an optical connector, and thermal shrinkage is performed, so that the influence of shrinkage in the reflow process can be reduced. Therefore, since the dimensions after shrinkage by reflow can be confirmed before mounting on the substrate, it is possible to suppress the occurrence of dimensional defects due to shrinkage after the reflow process.

[0079] In addition, since there is no need to use a special resin, the cost is low. Also, for example, since the linear expansion coefficient does not change significantly between the optical connector made of PPS or the like to be connected, an increase in optical loss due to environmental temperature can be suppressed.

[0080] In addition, since fine inorganic particles are appropriately added, deformation during heat treatment can be suppressed, and strength and dimensional stability can be ensured.

[0081] Also, in the production of the ferrule-attached fiber ribbon, by performing heat treatment after fixing the optical fiber 17 with the adhesive 19, not only the ferrule 1 for the optical connector but also the adhesive 19 can be pre-shrunk. Therefore, in the reflow process, the pitch of the optical fiber 17 and the protruding amount from the end face of the ferrule 1 for the optical connector can be stabilized.

[0082] In addition, in the processes shown in FIGS. 4 and 6, heat treatment A may be omitted. In this case, by only heat treatment B, the same effect as heat treatment A can be obtained simultaneously. However, when it is necessary to extend the heat treatment time of heat treatment A (for example, when 230°C to 260°C for 10 minutes or more is required to obtain a more stable effect), it is desirable to set the conditions of heat treatment B to 230°C to 260°C for 10 minutes or more, or to perform both heat treatment A and heat treatment B.

[0083] As described above, the embodiments of the present invention have been described with reference to the accompanying drawings. However, the technical scope of the present invention is not limited by the above-described embodiments. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention.

Example

[0084] (Shrinkage rate) The shrinkage amount during heat treatment for the reflow process was actually confirmed by manufacturing a ferrule for an optical connector. PPS was used as the resin composition, and spherical silica was added. When heat treatment A at 260°C for 1 minute was performed in a heating furnace after injection molding, the shrinkage rate (measured at the guide hole pitch distance (=4.6 mm)) was in the range of 0.15% to 2.0%. After cooling these, when heat treatment at 260°C for 1 minute was performed again in the heating furnace, the shrinkage rate was all 0.13% or less with respect to the dimensions after heat treatment A.

[0085] From the above results, since the actual general reflow process involves holding for about one minute, when a ferrule for an optical connector without heat treatment A is introduced into the reflow process (for example, 260°C × 1 minute), a greater shrinkage occurs. However, it was found that if heat treatment A is performed first, the shrinkage during the reflow process can be suppressed.

[0086] Thus, if heat treatment A (pre - heat treatment) is not performed, there is a risk of significant shrinkage and variation occurring during the reflow process.

[0087] On the other hand, by performing heat treatment A (pre - heat treatment) first, the shrinkage rate is small and the variation is also small in the subsequent heat treatment (reflow process). Therefore, by forming the ferrule taking into account the shrinkage amount in heat treatment A, the reference dimensions can be satisfied after shrinkage. Further, by excluding those whose dimensions deviate from the standard after heat treatment A, it is possible to suppress the dimensions from deviating from the reference after the subsequent reflow process.

[0088] When the time of heat treatment A was changed and the shrinkage rate by time was evaluated, at 10 minutes or more, the shrinkage rate hardly changed and became almost constant. As described above, the effect of pre - heat treatment was confirmed sufficiently even in 1 minute for heat treatment A, but in order to obtain a more stable pre - heat treatment effect, it is desirable that the above heat treatment A be 10 minutes or more.

[0089] (Pull - in amount) An optical fiber was fixed to the ferrule for an optical connector after heat treatment A with an adhesive and polished to have a protrusion amount of 1 - 3.5 μm. Then, heat treatment B of 260°C × 1 minute was performed in a heating furnace, and the pull - in amount of the optical fiber after heat treatment B was evaluated.

[0090] As a result, although there was a difference in the amount of retraction depending on the position of the optical fiber (hole), the amount of retraction was about 4 to 6 μm on the end side in the parallel direction (the side closer to the guide hole), and 6 to 10 μm in the vicinity of the center in the width direction. It is considered that the vicinity of the center, which is farther from the wall surface of the internal space of the ferrule for the optical connector, is more easily affected by the shrinkage due to the adhesive. For this reason, by polishing so that the protruding amount of the optical fiber at the center gradually increases in consideration of the amount of retraction depending on the position, the protruding amount of the tip of the optical fiber after the heat treatment B can be kept within a predetermined range.

[0091] In addition, even if only the heat treatment B is performed without performing the pre-heat treatment A, the same effect can be obtained. For example, an optical fiber was fixed to a ferrule for an optical connector without performing the heat treatment A with an adhesive and polished so that the protruding amount was 1 to 3.5 μm. Then, if a heat treatment at 260 °C for 1 minute is performed in a heating furnace, an effect almost equivalent to performing the heat treatment A and the heat treatment B can be obtained.

Explanation of symbols

[0092] 1......... Ferrule for optical connector 5......... Adhesive injection window 7......... Connection end face 9......... Hole 11......... Guide hole 13......... Internal space 15......... Recess 17......... Optical fiber 19......... Adhesive

Claims

1. A ferrule for an optical connector in which an optical fiber is fixed inside and the tip side serves as a connection end face, a hole into which the optical fiber is inserted, a pair of guide holes into which positioning guide pins are inserted, and comprising, the ferrule is composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin mainly composed of PPS resin, a ferrule characterized in that the shrinkage rate of the ferrule at 260 °C × 1 minute, which is higher than the glass transition temperature of the PPS resin, is 0.13% or less.

2. The linear expansion coefficient of the resin composition is 3.0×10 －５ / °C or less, and the ferrule according to claim 1 is characterized by this.

3. The ferrule according to claim 1, characterized in that the inorganic particles include 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 particle size distribution D of the inorganic particles １００ The ferrule according to claim 1, characterized in that it is 60 μm or less.

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

7. The ferrule according to claim 1, characterized in that an adhesive injection window is opened outside the ferrule, and a concave portion is formed on the outer surface 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 by having a heat treatment step at 230 °C or higher and 260 °C or lower for 1 minute or more, which is higher than the glass transition temperature of the PPS resin, after the ferrule is molded.

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

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

11. A method for manufacturing an optical fiber ribbon with a ferrule in which an optical fiber is fixed inside a ferrule for an optical connector whose tip side serves as a connection end face, the ferrule is composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin mainly composed of PPS resin, a plurality of holes into which the optical fiber is inserted, a pair of guide holes into which positioning guide pins are inserted, and comprising, a step of performing heat treatment on the ferrule at 230 °C or higher and 260 °C or lower for 1 minute or more, which is higher than the glass transition temperature of the PPS resin, A step of inserting an optical fiber into the ferrule; A step of fixing the optical fiber to the ferrule; A step of polishing the tip surface of the ferrule to project the optical fiber of a predetermined length from the end surface of the ferrule; A method for manufacturing a fiber ribbon with a ferrule, comprising the above steps.

12. The method for manufacturing a fiber ribbon with a ferrule according to claim 11, further comprising a step of performing a heat treatment at 230 °C or higher and 260 °C or lower for 1 minute or more after the polishing step.

13. The method for manufacturing a fiber ribbon with a ferrule according to claim 12, wherein the protruding amount of the optical fiber from the end surface of the ferrule after polishing and before heat treatment is 5 μm or more.

14. The method for manufacturing a fiber ribbon with a ferrule according to claim 11, further comprising a step of performing a heat treatment at 230 °C or higher and 260 °C or lower for 1 minute or more before the polishing step.

15. A method for manufacturing a fiber ribbon with a ferrule in which an optical fiber is fixed inside a ferrule for an optical connector whose tip side is a connection end surface, The ferrule is composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin mainly composed of PPS resin, A plurality of holes into which the optical fiber is inserted, A pair of guide holes into which positioning guide pins are inserted, Comprising, A step of inserting the optical fiber into the ferrule; A step of fixing the optical fiber to the ferrule; A step of polishing the tip surface of the ferrule to project the optical fiber of a predetermined length or more from the end surface of the ferrule; A step of performing a heat treatment at 230 °C or higher and 260 °C or lower for 1 minute or more, which is higher than the glass transition temperature of the PPS resin, after the polishing step; A method for manufacturing a fiber ribbon with a ferrule, comprising the above steps.

16. The method for manufacturing a fiber ribbon with a ferrule according to claim 15, wherein the protruding amount of the optical fiber from the end surface of the ferrule after polishing and before heat treatment is 5 μm or more.

17. A method for manufacturing a fiber ribbon with a ferrule in which an optical fiber is fixed inside a ferrule for an optical connector whose tip side is a connection end surface, The ferrule is composed of a resin composition in which a filler containing at least inorganic particles is added to a thermoplastic resin mainly composed of PPS resin, A plurality of holes into which the optical fiber is inserted, A pair of guide holes into which guide pins for positioning are inserted, comprising: a step of inserting the optical fiber into the ferrule, a step of fixing the optical fiber to the ferrule, a step of performing heat treatment at 230°C or higher and 260°C or lower, which is higher than the glass transition temperature of the PPS resin, for 1 minute or longer, after the heat treatment, a step of polishing the tip surface of the ferrule to project the optical fiber of a predetermined length from the end surface of the ferrule, A method for manufacturing a fiber ribbon with a ferrule, characterized by comprising the above.

Images