JPS596206B2 - Manufacturing method of receptacle for optical fiber connector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a receptacle for an optical fiber connector.

Optical communication has features such as low loss, wide bandwidth, and light weight, and research into its practical application has been actively progressing recently.

This is largely due to improvements in the performance of optical communication devices5, such as lower loss in fiber cables and longer lifespans of semiconductor lasers. However, when it comes to practical application of optical communication,
In addition to improving the performance of basic elements such as optical fibers, light emitting elements, and light receiving elements, in order to make effective use of the system,
The most important peripheral technology 10, for which establishment of peripheral technology is an important issue, is connection technology for connecting each element. Examples include optical coupling technology for effectively introducing and extracting optical signals emitted from light emitting elements into and from optical fibers, and optical fiber connection technology for maintaining low loss between optical fibers. 15 Optical fiber connection technology includes permanent connections and removable connectors, but connectors are more complex than permanent connections due to operational issues such as high-precision alignment, removability, and compatibility. is required.

20 There are many proposals for the structure of optical fiber connectors, but
Usually, it consists of a plug and a receptacle, and has a structure in which the two plugs meet inside the receptacle.

In order to connect with low loss, it is necessary to coaxially butt two fibers together.25 For this purpose, the accuracy of the outer diameter of the plug, setting the fiber in the center of the plug, and the accuracy of the inner diameter of the receptacle are important. . This accuracy is required to be at the 1 μm level because the diameter of the optical fiber is small. Currently, it is made with precision metal processing and is very expensive30.
It is becoming. If this can be molded from plastic, it can be manufactured at a very low cost. The present invention relates to plastic receptacles in connectors, and provides a plastic receptacle with excellent inner diameter accuracy.

Optical communication connectors have a plug with an accurate outer diameter that is aligned coaxially within the receptacle, so the accuracy of the plug is 1 μm.
Even if it is specified by the level, the loss level will vary greatly depending on the accuracy of the receptacle inner diameter dimension. In order to stabilize the inner diameter dimension in plastic molding, it is important to suppress variations in the shrinkage rate of the material and the precision of the mold core pin.
It is not very difficult to specify the precision of the core pin of a mold to the 1 μm level, but the variation in the shrinkage rate of plastic is usually about 0.1%, so it is extremely difficult to suppress the variation in the shrinkage rate of the material to the 1 μm level. be. Even if the desired dimensional accuracy can be obtained, the probability of achieving it is low, and the advantages of mass production and cost reduction due to plastics cannot be maintained. The present invention has been made in view of the above points, and when molding a receptacle for an optical fiber connector using plastic, the outer diameter dimension is used as a core pin of a mold for molding the receptacle, and the outer diameter dimension is determined by the shrinkage rate of the plastic. After the plastic is press-fitted into the mold and removed from the mold using the specified minimum shrinkage rate within the variation of This method stabilizes the inner diameter dimension by inserting and holding the receptacle into the receptacle. The characteristic of this is that the molding shrinkage rate of the material fluctuates around a certain center value, so the outer diameter of the core pin of the mold is not the center of the shrinkage rate, but rather the mold shrinkage rate of the plastic varies. It is created by specifying the minimum shrinkage rate within the range. Another object of the present invention is to eliminate variations in the inner diameter of the receptacle by inserting a monitor core pin having a specified outer diameter into the receptacle immediately after molding and before contraction begins, and correcting the inner diameter with the monitor core pin. The precision of the monitor core pin can be achieved with a precision of 1 μm through mold processing, so there is no problem. According to the above method, the inner diameter of the plastic receptacle can always be maintained at a constant value. The present invention will be described in further detail below.

FIG. 1 shows a flow chart of the present invention. The mold core pin has a larger shrinkage rate than the monitor core pin, so there is no problem when inserting it. To explain briefly according to the flowchart, select several suitable materials,
Measure the shrinkage rate and understand its distribution.

In this case, the influence of factors such as molding conditions, such as temperature, pressure, time, etc., is checked, and the material with the smallest change, including variations, is selected. The criteria for initially selecting the material will be described later, but basically a material with a small shrinkage rate is selected.

In this way, the outer diameter of the mold core pin is calculated and prescribed by calculating backwards from the smallest value of the shrinkage rate of the selected material. For example, the specified dimensions are 11. The smallest shrinkage rate of the material is α%.
Then, the outer diameter of the mold core pin monitor The outer diameter of the core pin is l, and both are made with an accuracy of 1 μm. Because the molded receptacle's immediate dimensions are dominated by the mold core pin, compared to the monitor pα core pin? Since it is large by 100-α, it can be easily inserted.

The receptacle into which the monitor core pin is inserted will shrink over time and reach the specified dimensions (outer diameter of the monitor core pin).
Even if the shrinkage rate becomes larger than α% due to fluctuations in the molding conditions etc., the monitor core pin can ensure the specified dimension l. In addition, the monitor core pin does not need to be inserted immediately after molding, and the receptacle should be heated to 100 to 130°C.
It may be inserted after being heated and expanded. The smaller the variation in shrinkage rate of the material used in the present invention, the better.
Therefore, the yield and stability of the product can be ensured by using a material that contains a large amount of filler that does not affect the shrinkage rate within the moldable range. The fillers used here are inorganic, such as silica, calcium carbonate, alumina, silicon, aluminum hydroxide, magnesite, clay, kaolin, talc, silica sand, glass, fused silica glass, mica, graphite, and carbon black. Good fillers such as wood flour, vinylon, cloth chips,
Organic fillers such as pulp and cotton waste may also be used in some cases, and both inorganic and organic fillers can be used in combination.
The present invention will be explained below with reference to Examples, but the present invention is not limited to the present invention in any way.

[Actual example]

A cross-sectional view of the mold used is shown in FIG. 2, and a plan view of the lower mold is shown in FIG. 3.

In FIGS. 2 and 3, the mold core pin 4 is set in the mold upper mold 1 and the mold lower mold 2.

Molding material is fed into the cavity 3 through the runner 6 and gate 7 to obtain a product 9. 5 is a mold parting surface, and 8 is a mold core pin positioning groove.

The molding material used was an epoxy resin molding material (trade name: CEL-MU3, manufactured by Hitachi Chemical Co., Ltd.). CEL-M
Table 1 shows the distribution of shrinkage rates of U3. In this case, the shrinkage rate was measured according to JIS K69ll with n=50.

Among the variations in shrinkage percentage measured in Table 1, 1 of the shrinkage percentage
The outer diameter of the mold core pin was determined based on the smallest value of 0.59%. The specified dimensions of the receptacle are 3,000
0m71L, and the mold core pin defined from the minimum shrinkage rate is 3,018m7! It becomes L.

Mold core pin and monitor core pin each 3,018
71A7! L, 3, OOOmm, and a receptacle was created according to the flowchart in FIG. The molding conditions were a temperature of 160° C., a pressure of 70 kg/Cdl, and a time of 6 minutes to perform transfer molding. Of the 40 optical connector receptacles manufactured in this way, 38 had a length of 3,000 m.
111 pieces were broken when removed from the monitor core pin, and the other one took 3,002 pieces.

When we measured the connection loss by inserting plugs into 38 non-defective receptacles, 76% of them were 0.7dB or less, and the maximum connection loss was not over 1.0dB, which is required for normal optical fiber connectors. The level was sufficiently satisfactory. [Comparative example] The minimum shrinkage rate measured under the same conditions as in Table 1 was 0.9%.
Using epoxy resin molding material trade name CEL-X-50 manufactured by Hitachi Chemical Co., Ltd., which has a maximum shrinkage rate of 1.1%,
A receptacle was molded using the above mold.

It was not very difficult to take them out of the mold, but 8 out of 10 pieces broke during removal after correction by inserting a monitor core pin, and the remaining 2 pieces had linear scratches on the inside. The reasons for this are, firstly, that the mold core pin is not specified to a minimum shrinkage rate, and secondly, because the shrinkage rate is large, the tightening force to the monitor core pin becomes large. In view of the above points, the present invention is highly effective in stabilizing the inner diameter dimension of the receptacle, preventing the effects of variations in molding conditions, and improving product yield.

[Brief explanation of drawings]

FIG. 1 is a flow chart of receptacle molding, FIG. 2 is a sectional view of a mold used in an embodiment of the present invention, and FIG. 3 is a plan view of a mold used in an embodiment of the present invention.

Claims (1)

[Claims] 1. When molding a receptacle for an optical fiber connector with plastic, the core pin of the mold for molding the receptacle is created by specifying the outer diameter dimension at the minimum shrinkage rate among the variations in the shrinkage rate of the plastic. After the plastic is press-fitted into the mold and removed from the mold, a monitor core pin precisely machined to the required dimensions is inserted and held in the receptacle before the molded product begins to shrink. A method for manufacturing receptacles for optical fiber connectors.