JPS6155647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferrule for an optical connector used for connecting optical fibers and a method for manufacturing the same.

Conventionally, ferrules for optical connectors have been molded by transfer molding of thermosetting resin containing inorganic fillers or injection molding of thermoplastic resin. Holes are also machined at the same time as molding by placing core pins in the mold. However, in this method, there remain major problems such as rapid degassing within the mold during molding and ease of demolding the molded product from the mold. That is, when molding is performed using a mold in which a hole-forming core pin 8 for inserting an optical fiber wire is installed at the bottom of the cavity 3 as shown in FIG. Although the effect is sufficiently demonstrated, the work of setting the pipe into the mold is complicated, which significantly reduces work efficiency.
It had the disadvantage of being inferior to mass production. In addition, when molding is performed using a mold in which a core pin receiving hole 9 is installed at the bottom of the cavity 3 as shown in FIG. Since degassing is performed with a clearance of The eccentricity of the important optical fiber insertion hole cannot be determined accurately. On the other hand, if the clearance is made small in order to achieve eccentricity of the optical fiber insertion hole with high accuracy, there is a problem that degassing may be insufficient or the core pin 8 may be damaged when inserted into the core pin receiving hole 9.
Furthermore, since ferrules for optical connectors require extremely high dimensional accuracy, they must be molded at a high molding pressure, which has the greatest effect on mold transfer accuracy. Therefore, when molding is performed using a mold as shown in Figures 1 and 2, it is necessary to remove the ferrule, which has a length approximately 2 to 4 times the outer diameter, from the cavity 3, which has a dead-end structure, under reduced pressure. This was difficult due to the low productivity, and the problem was that there was a disadvantage in terms of price due to decreased productivity.

In this way, in the ferrule molding method, in which the hole for inserting the optical fiber wire is processed simultaneously during molding, the dimensions,
The drawback was that ferrule molded products with excellent shape accuracy could not be efficiently molded.

Therefore, the present inventors attempted a ferrule processing method in which a ferrule with excellent outer diameter accuracy was formed by transfer molding of an epoxy resin containing silica powder, and then a hole for inserting an optical fiber was formed by drilling. As shown in Fig. 3, the ferrule molding die with excellent outer diameter accuracy used for this process does not have a core pin for forming a hole for inserting the optical fiber wire, but has a core 12 for communicating with the outside air and a core receiver for communicating with the outside air. It has a structure with holes 13. In a method using a mold having such a structure, the outside air communication core 12 (φ0.5
Sufficient gas can be vented from the gap (0.1 mm) between the outside air communication core insertion part 13 (mm) and the outside air communication core insertion part 13 (φ0.7mm), and the outside air communication core 12 can be removed from the outside air communication core insertion part 13 before demolding. As a result, the tip of the ferrule molded product communicates with the outside air, and the reduced pressure inside the cavity 3 can be avoided, resulting in a marked improvement in demoldability. However, when an attempt was made to form a hole for inserting an optical fiber wire in the center of the tip of a molded product obtained by this method using a drill with a diameter of 0.126 mm, the tip of the drill was significantly worn due to silica powder in the resin. A new problem arose.

As a result of further studies, the inventors of the present invention found that a ferrule body having a through hole larger than the diameter of the optical fiber in the center was molded in advance with a resin containing a hard inorganic filler, and the through hole The inventors have discovered that a ferrule with excellent precision can be obtained by closing the ferrule with a relatively soft resin and then providing a through hole for inserting the optical fiber in the closed portion, leading to the present invention.

That is, the gist of the present invention is to provide a ferrule for a resin non-adjustable optical connector, in which the ferrule main body is made of a resin containing an inorganic filler having a Mohs hardness of 2 or more, and the portion including the hole for inserting the optical fiber wire is The ferrule for an optical connector is characterized in that it is made of a resin that is softer than the ferrule main body, and the resin contains an inorganic filler with a Mohs hardness of 2 or more, so that a through hole with a diameter larger than the optical fiber wire is formed in the center. Manufacturing a ferrule for an optical connector, characterized in that a ferrule body having a ferrule body is molded, the through hole is closed with a resin softer than the ferrule body, and a through hole for inserting an optical fiber wire is bored in the closed part. It's in the method.

The present invention will be described below with reference to drawings showing embodiments. In FIG. 4, reference numeral 14 is a ferrule main body, and an optical fiber core introduction hole 16 is provided in the center of the ferrule body. It consists of a closing part 17 having a hole 18 for inserting an optical fiber in the center.

It is desirable that the resin used for the ferrule body 14 of the present invention has low shrinkage and low material.
It must not only have little dimensional change due to temperature, humidity, chemicals, etc., but also have excellent mechanical properties such as abrasion resistance and bending strength.
A system in which an inorganic filler having a Mohs hardness of 2 or more is added to a resin is used. Examples of resins used include thermosetting resins such as epoxy resins, phenolic resins, and unsaturated polyester resins.
Other thermoplastic resins such as polycarbonate, polybutylene terephthalate, or polyphenylene sulfide may also be used. Examples of inorganic fillers added to the resin include powdered materials such as silicon carbide, silica, and calcium carbonate, which have a Mohs hardness of 2 or more, fibrous materials such as glass fiber, and various metal powders. Although the amount of the filler added is not particularly limited, the amount added to the resin is generally 30 to 80 wt%. Furthermore, the resin used for the closing part 17 forming the optical fiber insertion hole 18 may be one containing a filler as long as it has good adhesion to the ferrule body and has good drillability. However, the hardness of the filler is preferably less than 2 on the Mohs hardness scale.

The length of the optical fiber insertion hole 18 is not particularly limited as long as it is at least long enough to hold the optical fiber in the hole so as not to break, but if it is too long, the size and shape may be affected. It is very difficult to achieve high precision and also reduces workability, so it is preferably about 0.5 mm to 3 mm.

Next, to explain the manufacturing method of the above-mentioned ferrule, a ferrule body 14 having pores 15 larger than the diameter of the optical fiber is produced by transfer molding or injection molding, which will be described later. After being closed with resin, the optical fiber wire insertion hole 18 is re-drilled for manufacturing. A drilling method, a laser method, a water jet method, an electron beam method, etc. can be used as a drilling method for the hole 18 for inserting the optical fiber wire, but the drilling method is preferably used.

The ferrule main body 14 has a pore-forming core pin 11 installed in the cavity 3 as shown in FIG.
Molding can be performed using a mold in which a core pin receiving hole 19 for forming pores is installed at the bottom thereof.

The outer diameter of the end of the core pin 11 for forming the pore is larger than the diameter of the hole for inserting the optical fiber wire and the amount of misalignment of the device when drilling the hole for inserting the optical fiber wire. Although there is no particular limitation as long as it can be formed, preferably a diameter of φ0.3 or more and smaller than the outer diameter of the ferrule is used in consideration of preventing breakage and bending during molding.

The material and shape of the core pin 11 are also included in the pore 15 having a size larger than the diameter of the optical fiber wire.
Although there is no particular limitation as long as it can be formed, a cylindrical one made of SKH-9 or SKD-61 is generally used.

The clearance between the pore-forming core pin 11 and the pore-forming core receiving hole 19 used in the present invention is not particularly limited as long as the cavity 3 can be sufficiently vented, but is preferably
It is about 20 to 400 μm.

Example 1 The ferrule body was made from Hitachi Chemical Co., Ltd. as a material.
An epoxy molding material CEL-7000 [containing 70% silica powder (Mohs hardness 7)] was produced by transfer molding using a mold having the structure shown in FIG. 5. The mold has a length of 0.8 mm of the tip (φ0.5 mm x 1.5 mm) of the pore forming core pin 11 that forms the pore 15 in the pore forming core pin receiving hole 19 ( φ0.7mm×0.8
mm), with a tapered part of approximately 1 mm (gradient 1/4)
12mm of the straight part (diameter 1.0mm) excluding
2.5mm is inside cavity 3, 2.5mm is outside cavity 3, and the rear part has a stopper 10 to prevent movement due to resin pressure during molding.

Next, the pores 1 of the molded product produced by the above method are
In step 5, seal the epoxy resin up to approximately 0.7 mm from the tip, and place a diameter of 126 μm and a length of 0.9 mm at the center of the end surface of the molded product.
A hole 18 for inserting an optical fiber having a diameter of 125 μm was drilled using a drill. Similarly, after drilling 100 ferrule optical fiber insertion holes 18 using the same drill, the drill blade was observed under a microscope, and almost no wear was observed on the drill blade. In addition,
Mohs hardness less than 2, e.g. talc (Mohs hardness 1)
No significant wear was observed in the drilling force when an epoxy resin containing 30 parts by weight of 30 parts by weight was used as the sealing resin.

The resin ferrule for non-adjustable optical connectors produced by this method has a gap (0.1 mm) between the pore-forming core pin 11 and the pore-forming core pin receiving hole 19.
Since sufficient gas can be vented from the
It was 1.8 μm. Therefore, when drilling the optical fiber insertion hole 18 by drilling, it is possible to accurately center the hole 18, and as a result, the eccentricity 2
μm was obtained. In addition, demolding could be easily performed because the tip of the ferrule molded product was in communication with the outside air.

Next, an optical fiber was inserted and fixed into the ferrule produced by this method, and the connection loss was measured to be 0.45 dB. In addition, heat cycle test (-20℃-2h, -20℃→80℃ heating time 1h, 80℃
-2h, 80℃ → -20℃ cooling time 1h, 10 cycles)
We carried out the test and measured the connection characteristics before and after the test as well as the ingress and egress of the optical fiber, and found that the fluctuations in the connection characteristics were
0.1 dB (10 samples), the amount of change in the entrance and exit from the end of the optical fiber ferrule is 0.3 μm (10 samples)
It was hot.

Comparative Example Using the mold shown in FIG. 3, transfer molding was performed using the same material as in Example 1. Then, when a hole for inserting the optical fiber of one ferrule was drilled in the center of the end face of the molded product using a drill in the same manner as in Example 1, significant wear of the drill blade was observed by microscopic observation.

In this method, if the drill blade is replaced, Example 1
A ferrule with almost the same initial characteristics was obtained, but when a heat cycle test similar to that in Example 1 was conducted, the average variation in connection characteristics was 0.18 dB.
(Number of samples: 10), the average amount of change in the ingress and egress of the optical fiber is
It was 1.5 μm.

As is clear from the above description, according to the present invention, degassing, which has conventionally been a problem in molding resin ferrules for non-adjustable optical connectors, can be solved by connecting the pore-forming core pin 11 and the pore-forming ferrule. Since the gap between the core pin receiving hole 19 can be made large, the process can be carried out sufficiently, and since the gap between the pore forming core pin 11 and the pore forming core pin receiving hole 19 communicates with the outside air, the forming process can be easily carried out. We were able to demold the product.

In addition, to solve the problem of severe wear on the tip of the drill when drilling the hole for inserting the optical fiber wire with a drill, the part where the hole for inserting the optical fiber wire is drilled is made of a softer resin than the ferrule body. As a result, the life of the drill bit has been increased by 30 times compared to conventional models.

Furthermore, unlike conventional ferrule molding, there is no need to add a mold release agent to the resin in which the optical fiber insertion hole of the ferrule obtained according to the present invention is formed. It was also possible to obtain advantages in terms of adhesiveness between the ferrule and the optical fiber.

[Brief explanation of the drawing]

1, 2, and 3 are schematic cross-sectional structural diagrams of conventional ferrule molding molds, FIG. 4 is a sectional view showing an example of the ferrule of the present invention, and FIG. 5 is a cross-sectional view showing an example of the ferrule of the present invention. FIG. Explanation of symbols, 1...upper mold, 2...lower mold, 3...
Cavity, 4...Pipe, 5...Sprue, 6
...Gate Runner, 7...Link Gate, 8...
... Core pin, 9 ... Core pin receiving hole, 10 ... Stopper, 11 ... Core pin for pore formation, 12 ...
... Core pin for outside air communication, 13 ... Core pin insertion part for outside air communication, 14 ... Ferrule body, 15 ...
Pore, 16... Hole for introducing optical fiber core, 17...
...Occluded portion, 18...Optical fiber wire insertion hole, 1
9... Core pin receiving hole for pore formation.

Claims (1)

[Scope of Claims] 1. A ferrule for a non-adjustable optical connector made of resin, in which the ferrule main body is made of a resin containing an inorganic filler with a Mohs hardness of 2 or more, and the portion including the hole for inserting the optical fiber wire is A ferrule for an optical connector, characterized in that it is made of a resin that is softer than the ferrule main body. 2. A ferrule body having a hole in the center with a diameter larger than that of the optical fiber strand was molded from a resin containing an inorganic filler with a Mohs hardness of 2 or more, and the hole was closed with a resin softer than the ferrule body. A method for producing a ferrule for an optical connector, comprising: thereafter, drilling a through hole for inserting an optical fiber into the closed portion.