JP2002250839A - Ferrule for optical fiber connector and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] Kneading and granulating a metal powder (stainless steel powder and Kovar powder are excellent) and a binder synthetic resin to make a green body as a flowable material for injection molding. A metal ferrule for an optical fiber connector manufactured by degreasing and sintering the same, and a method for manufacturing the same. A ferrule for an optical fiber connector manufactured by the following steps 1-4. Step 1: A metal powder and a binder are kneaded and granulated to obtain a fluid material. Step 2: A green body is formed from the fluid material by injection molding. Step 3: The green body is degreased to remove the binder, and then sintered to form a ferrule prototype. Step 4: Post-process the ferrule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrule for an optical fiber connector and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the development of optical communication technology, it has become possible to introduce various types of communication services by introducing optical fibers to homes. To realize such a subscriber communication network, an economical optical connector is required. Optical fibers include quartz glass, multi-component glass, and plastic fibers.Square glass is used for long-distance transmission for public communication, and multi-component glass is used for medium. It is used for long-distance transmission, and the plastic type is used for short-distance transmission. As shown in FIG. 5, the connection of optical fibers used for optical communication is performed by two ferrules 1a, 1a into which optical fibers 4a, 4b are inserted.
This is performed by aligning and aligning the b in the holder 5, and a configuration for making it detachable based on this basic structure,
An optical connector (not shown) is configured in combination with a configuration for providing optical fiber holding strength and the like.

Normally, the ferrules 1a and 1b have an optical fiber core guide hole 3 and a single optical fiber insertion hole 2 at the tip thereof, as shown in FIG. 1, for example. In order to apply such ferrules 1a and 1b to a silica glass single mode fiber, extremely high dimensional accuracy is required for the eccentricity of the optical fiber insertion hole 2, the outer diameter of the ferrules 1a and 1b, and the outer diameter roundness. Is required. That is, the silica glass single mode fiber has a diameter of 125 μm, while the core diameter is only several tens of μm.
Because there is only a degree. The dimensions of the ferrule used for this purpose are usually about 2.5 mm in outer diameter and about 1 in length.
0.5 mm, inner diameter is about 126 μm.

The characteristics required of such a ferrule for an optical connector are as follows. (1) The optical fiber can be easily passed through the pores. (2) Being able to process accurately. In particular, the inner diameter, outer diameter accuracy, straightness, and concentricity between the pore and the outer peripheral surface of the pore can be accurately obtained. (3) The toughness is not less than a certain level. Should not be broken by accidental dropping or shock during connector assembly or connection work. (4) For a thermal expansion coefficient of 5 × 10 ⁻⁶ ° C. of the optical fiber,
The coefficient of thermal expansion is not very different. Due to the temperature change, the optical fiber retracts into the capillary pores,
Protrusion causes a loss in optical signal transmission. Heretofore, ceramic (zirconia) sintered bodies have been widely used as ferrule materials for optical connectors requiring such characteristics. The reason is that it is excellent in the following points. (A) Since plastic deformation hardly occurs, deformation and burrs during processing do not occur and processing can be performed with high accuracy. Also, when the capillaries are butted against each other, they are not deformed by the pressing force. (B) The fiber has good compatibility with the fiber mainly composed of glass, and the fiber can be easily inserted even if the clearance between the inner diameter of the capillary and the outer diameter of the fiber is 1 μm or less. (C) Since the difference in thermal expansion from the fiber is small and the heat resistance is excellent, it is resistant to changes in the thermal environment. (D) Since the connector has excellent abrasion resistance, contamination of the end face due to abrasion powder does not easily occur when the connector is repeatedly attached and detached, and poor connection hardly occurs.

Heretofore, it has been known that the ferrule is manufactured by cutting and polishing not only ceramics but also metal materials with high precision (Japanese Patent Application Laid-Open No. 2000-502).
No. 817), but nothing is disclosed about specific metal materials or manufacturing conditions. It is also known that a plastic is formed by injection molding and similarly cut and polished with high precision (Japanese Patent Application Laid-open No.
000-121872). However, these known ferrules require advanced processing techniques of cutting and polishing with high precision, have the problem of low manufacturing efficiency and high manufacturing cost, and furthermore, the dimensional change with time in terms of the material. There was also the problem of being large.

[0006]

The inventors of the present invention have conducted various studies on metal materials as constituent materials of ferrules, and as a result, have adopted various metal materials by adopting a specific method for powder metallurgy. They have found that the above-mentioned problems of the prior art can be solved, and have completed the present invention. That is, the present invention has been made in view of the above-described problems of the related art, using a metal material, high dimensional accuracy, mechanical strength,
An object of the present invention is to provide a ferrule for an optical connector used for connecting a small-diameter optical fiber which is excellent in connection reliability, durability (aging resistance) and economy, and a method for manufacturing the same.

[0007]

The present invention has the following features in order to achieve the above object.

[0008] A ferrule for an optical fiber connector, which is manufactured by the following steps 1-4. Step 1: A metal powder and a binder are kneaded and granulated to obtain a fluid material. Step 2: A green body is formed from the fluid material by injection molding. Step 3: The green body is degreased to remove the binder, and then sintered to form a ferrule prototype. Step 4: Post-process the ferrule.

[0009] At this time, as the metal powder, any one selected from steel (iron), stainless steel, Kovar (trade name), brass, phosphor bronze, aluminum, and other metals or alloys is used. Can be.

Further, the ferrule can be manufactured by the following manufacturing method. Step 1 below
4. A method of manufacturing a ferrule for an optical fiber connector, comprising: Step 1: A metal powder and a binder are kneaded and granulated to obtain a fluid material. Step 2: A green body is formed from the fluid material by injection molding. Step 3: The green body is degreased to remove the binder, and then sintered to form a ferrule prototype. Step 4: Post-process the ferrule.

[0011] In this case, as the metal powder, any one selected from steel (stainless steel), stainless steel, Kovar (trade name), brass, phosphor bronze, aluminum, and other metals or alloys is used. Further, at the time of the injection molding, at least the two outer dies of the ferrule, ie, the mold 10 on the fiber insertion hole 2 side and the mold 20 on the fiber core wire guide hole 3 side, and the fiber insertion of the ferrule. Injection molding includes an inner diameter pin 6 for forming the hole 2 and the fiber core guide hole 3, the mold 20 on the fiber core guide hole 3 side is fixed, and the mold 10 on the fiber insertion hole 2 side is movable. The latter green body 1 'can be manufactured by pulling it out from the fiber insertion hole 2 side.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a ferrule for an optical fiber connector according to the present invention;

[0013]

FIG. 1 shows a ferrule 1 made according to the present invention. Assuming that the outer diameter of the optical fiber is 0.125 mm, the outer diameter D of the ferrule 1 is 2.5 to 3.0 mm, the inner diameter d1 of the fiber insertion hole 2 is 0.126 mm, and the inner diameter d2 of the fiber core guide hole 3. Is 0.3-0.8m
m, the ferrule length t1 is 5.0 to 12.0 mm, and the length t2 of the guide hole 3 is about 2/3 of the length of t1. In addition,
The contact surface 8 of the ferrule is required to be flat in order to reduce transmission loss between optical fibers. FIG. 2 schematically shows a manufacturing process of the ferrule according to the present invention.

(1) Step 1: Kneading / granulation The metal powder and the synthetic resin of the binder are heated and kneaded by a kneading machine, and then granulated to obtain a fluid material for injection molding. As the metal powder, steel having an average particle diameter of 1 μm or less is usually used.
Or a metal material such as stainless steel.However, when the optical fiber is made of quartz glass or multi-component glass, the thermal expansion coefficient is almost constant because high precision and low loss coupling can be maintained even if the temperature changes. Equivalent Kovar (KOVA)
R, trade name) is preferred. If high precision is not required, brass, phosphor bronze, aluminum, and other metals or alloys commonly used as electrical connection terminal materials as metal powders can also be used. Can be selected as appropriate according to the type of the object and the required accuracy.

As the binder, polystyrene, acrylic, wax or the like can be used as appropriate. To shorten the time for removing the binder, it is disclosed in Japanese Patent No. 3,100,968. UV-decomposable polyisobutylene, polymethacrylic acid, polymethacrylic acid ester, polymethacrylamide, poly-α-methylstyrene, etc., or a mixture thereof can also be used.

In the present invention, the flowable powder has a volume fraction of 30 to 70% of the metal powder. If the volume fraction of the metal powder is too low (the volume fraction of the binder is too high), pores are likely to be generated in the compact and the sintered body, and it takes time to remove the binder. Further, the stability of the shrinkage ratio is deteriorated, and the dimensional accuracy of the sintered body is deteriorated. Conversely, if the volume fraction of the metal powder is too high (the volume fraction of the binder is too low), the flowable powder becomes difficult to flow smoothly during injection molding, and the molded article becomes rough (that is, the sintered body becomes rough). Occurs. Therefore, the volume fraction of the metal powder is 30
~ 70% is preferable, and 40 ~ 6% for production stability.
0% is more preferable. When selecting the binder,
Injection moldability, heat stability during molding, shape retention, and binder removal properties are taken into consideration, but these properties generally depend on the structure of the polymer. The binder used in the present invention is a solid at room temperature, and a polymer exhibiting plasticity at 150 ° C. to 300 ° C. is used. The molding is performed by utilizing the plasticity of the polymer exhibited at high temperature, and the shape of the formed body is maintained at room temperature. Let it.

(2) Step 2: Injection Molding The principle of injection molding is almost the same as the manufacturing process of a plastic ferrule using an injection mold structure disclosed in Japanese Patent Application Laid-Open No. 2000-121872. FIG. 4 shows a part of the mold structure when the green body 1 ′ of the ferrule is injection-molded. The flowable material kneaded and granulated in step 1 is used as a raw material, and is injected from an injection hole 11 of an injection molding machine to produce a green body 1 'of a ferrule. The mold includes at least the mold 10 on the fiber insertion hole 2 side of the ferrule and the mold 2 on the fiber core wire guide hole 3 side.
0, two outer molds and a ferrule fiber insertion hole 2
And an inner diameter pin 6 for forming the fiber core guide hole 3. The tip 6a of the inner diameter pin 6 protrudes from the end face of the green body 1 '(t3 ≒ 0.55 mm).

In the present invention, after the green body 1 'is injection-molded, only the inner diameter pin can be pulled out independently, thereby preventing the tip 6a of the inner diameter pin 6 from being damaged. In the conventional mold, the mold 10 on the side of the fiber insertion hole 2 is fixed, and the mold 20 on the side of the fiber core guide hole 3 is movable, and the green body 1 'of the ferrule is moved toward the fiber core guide hole 3 side. However, in the present invention,
Conversely, the mold 20 on the side of the fiber core guide hole 3 is fixed, and the mold 10 on the side of the fiber insertion hole 2 is movable, so that the green body 1 ′ after injection molding is removed from the side of the fiber insertion hole 2. There is a feature in the point.

Then, the thickness of the green body 1 'of the ferrule is different between the fiber insertion hole 2 side and the fiber core wire guide hole 3 side, and the degree of shrinkage during cooling is smaller on the thicker side than on the thinner side. Therefore, the degree of contraction on the fiber insertion hole 2 side becomes larger than the degree of contraction on the fiber core wire guide hole 3 side, so that the mold 10 on the fiber layer through hole side can be easily removed, and the ferrule green The body 1 'can be easily pulled out. In addition, it is possible to prevent the tip portion 6a of the extremely thin inner diameter pin 6 from being damaged. By changing the mold structure, it is also possible to integrally mold a ferrule to which the holding portion 7 as shown in FIG. 4 is added in advance.

(3) Step 3: Degreasing and sintering The binder is removed by heating the green body 1 'of the ferrule injection molded in step 2. In the past, measures were taken to prevent shrinkage and deformation by processing over a long time of 48 to 100 hours, but in recent years, in order to secure molding accuracy and to shorten the processing time, A system for performing degreasing and sintering in one furnace has been developed. The heating temperature and time are appropriately selected depending on the type of the binder.
When an ultraviolet-decomposable polymer as described in JP-A-00,968 is used, the time for debinding can be shortened.
Perform at 00 ° C. After that, sintering is performed by increasing the heating temperature, and the shrinkage when the green body is converted into a sintered body greatly depends on the volume fraction of the binder. Shows 30% shrinkage. At the time of production, the dimensions of the molded body are determined from the degree of shrinkage determined experimentally. For example, stainless steel powder is used as the metal powder, the volume fraction of the stainless steel powder in the fluid material is 40%, and the viscosity of the fluid material is 1.
If 1 × 10 ⁵ (poise), the shrinkage ratio from the compact to the sintered body is 27%. Therefore, if the pore inside diameter of the compact (green body) is 172 μm, the sintered body pore inside diameter d1 ( FIG. 1) can be 126 μm.

(4) Step 4: Post-processing The ferrule body after sintering is subjected to grinding to improve the accuracy. The outside of the ferrule 1, the inside of the fiber insertion hole 2, the contact surface 8, and the like are ground using a diamond grindstone. In particular, the roundness of the fiber insertion hole 2 is maintained with an accuracy of ± 0.3 μm.

(5) Step 5: Inspection After the post-processing in step 4, the completed ferrule is inspected. Generally, a flange is attached. The diameter, roundness (± 0.3 μm), etc. of the fiber insertion hole 2 are inspected to reject defective products. Although the inner and outer surface polishing and shape inspection can be mechanized, the final inspection, such as appearance inspection, depends on humans.

[0023]

As described in detail above, according to the present invention, a metal material is used to provide excellent dimensional accuracy, mechanical strength, connection reliability, durability (aging resistance), and economic efficiency. A ferrule having a small diameter can be obtained, and has a characteristic that it has better compatibility with the holder and can be welded as compared with a ceramic ferrule (zirconium oxide, ZrO ₂ ).

[0024]

[Brief description of the drawings]

FIG. 1 is a sectional view of a ferrule of the present invention.

FIG. 2 is a block diagram showing a manufacturing process of the ferrule of the present invention.

FIG. 3 is a view showing an arrangement of a mold and an inner diameter pin when manufacturing the ferrule of the present invention.

FIG. 4 shows a ferrule of the present invention in which injection molding is performed up to a holding portion 7;

FIG. 5 is a diagram showing a basic configuration of an optical connector using the ferrule of the present invention.

[Explanation of symbols]

1: ferrule 1 ': molded ferrule (green body) 2: optical fiber insertion hole 3: optical fiber core wire guide hole 4a, 4b: optical fiber 5: holder 6: inner diameter pin 6a: tip of inner diameter pin 7: Holding part 8: Contact surface of ferrule

Claims (6)

[Claims] 1. A ferrule for an optical fiber connector manufactured by the following steps 1-4. Step 1: A metal powder and a binder are kneaded and granulated to obtain a fluid material. Step 2: A green body is formed from the fluid material by injection molding. Step 3: The green body is degreased to remove the binder, and then sintered to form a ferrule prototype. Step 4: Post-process the ferrule. 2. The method according to claim 1, wherein the metal powder is selected from the group consisting of steel (spot), stainless steel, Kovar (trade name), brass, phosphor bronze, and aluminum. 2. The ferrule for an optical fiber connector according to 1. 3. A method of manufacturing a ferrule for an optical fiber connector, comprising a manufacturing process of the following steps 1 to 4. Step 1: A metal powder and a binder are kneaded and granulated to obtain a fluid material. Step 2: A green body is formed from the fluid material by injection molding. Step 3: The green body is degreased to remove the binder, and then sintered to form a ferrule prototype. Step 4: Post-process the ferrule. 4. The method according to claim 1, wherein the metal powder is selected from the group consisting of steel (iron), stainless steel, Kovar (trade name), brass, phosphor bronze, and aluminum. 4. The method for producing a ferrule for an optical fiber connector according to item 3. 5. The mold for injection molding includes at least two outer molds, a mold on the fiber insertion hole side of the ferrule and a mold on the fiber core guide hole side, and the fiber insertion hole and the fiber core of the ferrule. Consists of an inner diameter pin for forming a wire guide hole, the mold on the fiber core guide hole side is fixed, the mold on the fiber insertion hole side is movable, and the green body after injection molding is pulled out from the fiber insertion hole side. 5. The method of manufacturing a ferrule for an optical fiber connector according to claim 3, wherein the ferrule is configured as described above. 6. The method for manufacturing a ferrule for an optical fiber connector according to claim 5, wherein a tip portion 6a of the inner diameter pin 6 as a mold projects from the green body surface during the injection molding.