JPH0333755B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an adhesive for precision fixing of parts used in a method of precision fixing parts that requires precise positioning. [Prior Art] For example, in various optical devices such as E/O converters, optical switches, and optical attenuators used in optical transmission systems using optical fibers, optical components such as light emitting elements, lenses, prisms, and optical connectors are used. After precisely adjusting the position and aligning the optical axis,
It is necessary to fix those optical components. In coupling these optical devices, the core radius of the optical fiber used is
It is only 20-30 μm, or only a few μm in the case of single mode fibers. Therefore, the coupling spot is extremely small, and even a slight deviation of the optical axis significantly reduces the coupling level, that is, the output level. Therefore, the method of fixing these optical components is as follows.
Precisely positioned parts are required not to fluctuate during fixation, and they also need to be stable against temperature changes and shocks even after fixation.
In addition, the workability of the fixing method itself must also be considered. Generally, these optical devices are fixed by roughly adjusting and installing the optical components, and then finely adjusting the lenses or optical connectors in the coupling system to precisely align the optical axis. In this case, a method is adopted in which an optical component to be finely adjusted, such as an optical connector, is attached to an adjustment plate, the adjustment plate is moved to align the optical axis, and the adjustment plate is fixed with screws. However, although this type of fixing method has the advantage that it is easy to correct optical axis deviation due to changes over time after fixing, it has poor workability and is not suitable for the production of optical devices. , when there are multiple fine adjustment sections, it causes difficulties in the design of the optical device. Therefore, this method is only partially utilized in combination with the following adhesive methods. When fixing components by adhesive, the optical component to be positioned is finely adjusted within the adhesive clearance provided between it and the base to be adhesively fixed, and after optical axis alignment is performed, the optical component is positioned between the base and the base. The adhesive placed in the adhesive clearance between the parts is cured and fixed. For example, in aligning the optical axis in the coupling between a light emitting diode and an optical fiber as shown in FIG. . In this case, laser diode 1
The optical connector 3 is fixed in advance, and the rod lens 2, which is temporarily fixed to the suspension rod 5 with a temporary adhesive 6 such as pine tar, is inserted into the receiving groove 8 provided in the base 7.
The receiving groove 8 and the rod lens 2 are installed so as to have adhesive clearance necessary for position adjustment, and the rod lens 2 is moved by the suspension rod 5 so that the emitted light from the laser diode 1 reaches the optical connector 3 with maximum output. The rod lens 2 is positioned so that the beam is emitted, and the adhesive 9 placed in the receiving groove 8 is cured to fix the rod lens 2. When the adhesive 9 has sufficiently hardened, the temporary adhesive 6 of the suspension rod 5 is removed to complete fixing of the rod lens 2. Conventionally, epoxy resin adhesives have been used as adhesives for such fixing, and epoxy resin adhesives have been used to reduce viscosity increase and curing shrinkage to prevent leakage from the relatively large adhesive clearance for optical axis alignment. Approximately 50% by weight of alumina powder was blended as an additive. [Problems to be Solved by the Invention] However, this epoxy adhesive called Tall Seal takes a long time to cure, and it takes a long time to cure the suspension rod that has been temporarily attached for optical axis alignment. The time required was more than 8 hours at room temperature, and more than 24 hours was required to complete curing. Therefore, the fine movement table used for aligning and fixing the optical axis has a long locking time and is easily affected by external vibrations and shocks during the long curing time, resulting in a disadvantage that the working efficiency is low. In order to improve this workability, patent application No. 55-168707
In this issue, a method was proposed in which a metal sleeve is fixed to a rod lens, the optical axis is aligned, and then the metal sleeve is soldered to the base. This method has the advantage that the working time is short, the optical axis of the fixed optical component is stable against temperature changes, and the change over time is small, but it is necessary to protect the component from high temperatures during soldering. Furthermore, since the shape of the parts is limited due to the attachment of the metal sleeve, the objects for which they can be used are limited. In addition, when using cyanoacrylate instant adhesives to shorten work time, the curing time is extremely short, making it difficult to align the optical axis accurately, and the adhesives are stable against temperature changes and changes over time after curing. It is difficult to mix fillers to improve properties, improve viscosity, and prevent run-off during bonding, which poses a practical problem. Another method is to use an optical axis type adhesive and mix small glass beads with a diameter of 7 to 50 μm, but because the diameter of the glass beads is small, there is a lot of light scattering and the light reaches deep parts. The intensity of the light is attenuated by then, and curing takes a relatively long time. As a result, differences in curing speed occur locally in the adhesive, internal stress occurs, and dimensional accuracy deteriorates. [Means for Solving the Problems] The present invention provides an adhesion method that has appropriate fluidity, fast curing, and less movement of parts due to changes in time and temperature after curing during alignment. The present invention provides adhesives that can be used. That is, the present invention provides an adhesive for precision fixing of components that is mainly composed of a photocurable adhesive and inorganic transparent particles, in which most of the inorganic transparent particles have a
This is an adhesive for precision fixing of parts, which is in the range of 400 μm and is blended in an amount exceeding 0.8 parts by weight and not more than 2.5 parts by weight per 1 part by weight of the photocurable adhesive. [Specific Description of the Invention] As the photocurable adhesive used in the adhesive for precision fixing of parts of the present invention, any photocurable adhesive can be used, but curing progresses slowly under visible light. It is preferable to use an ultraviolet curable, quick-drying photocurable adhesive that is cured by irradiation with ultraviolet rays. Modified acrylate adhesives are commercially available as such photocurable adhesives, such as Loctite 350, 352, and 358 manufactured by Nippon Loctite Co., Ltd.
TB3066 manufactured by ThreeBond, UV- manufactured by Amicon
990-30 and Somers UV-74 are used. In the adhesive for precision fixing of components of the present invention, an inorganic transparent material is used as the particles mixed in the photocurable adhesive. In general, the crosslinking reaction of photocurable adhesives is initiated by light stimulation, so if the adhesive layer is thick or if an opaque material is placed between the light source and the light cannot reach, the curing reaction will not occur. It's hard to get up. Some types of photocurable adhesives have the properties of anaerobic adhesives, and the crosslinking reaction progresses when a portion of the adhesive is photocured, but even in such cases, the amount of light irradiation is small. and curing progresses slowly. In the adhesive for precision fixing parts of the present invention, the inorganic transparent particles mixed in the adhesive diffuse the irradiated light, so the light can be transmitted to the inside where light normally cannot reach, and the inorganic transparent particles Due to the lens effect of the adhesive layer, there is little attenuation of light to the inside of the adhesive layer. Therefore, it is possible to precisely bond areas where light cannot reach where conventional photocurable adhesives could not be used, and because the curing reaction starts quickly inside the adhesive, there is less uneven curing and shrinkage. As a result, the fixing accuracy can be improved. The inorganic transparent particles mixed into the photocurable adhesive include, for example, quartz or glass particles, and their shape can be arbitrary, but they can be used depending on the fluidity and light transmission when mixed into the adhesive. Spherical particles are preferable from the viewpoint of the lens effect and the like, and glass beads are most preferable from these points and from the viewpoint of easy availability. The diameter of the inorganic transparent particles mixed into the photocurable adhesive is 20~
80% of the size, preferably around 50% of the average diameter. If the diameter of the inorganic transparent granules is too large compared to the adhesive clearance, alignment of the optical components will be hindered during adhesion, and if the diameter of the inorganic transparent granules is too small, the photocurable adhesive will When blended with the adhesive, it increases the viscosity of the adhesive more than necessary, impairing the flow of the adhesive, and there is a risk that the adhesive will not reach the areas where adhesive clearance is required. The amount of inorganic transparent particles mixed is 1 part of the photocurable adhesive.
The amount is within the range of more than 0.8 parts by weight to less than 2.5 parts by weight, and if the amount mixed is small, it will be greatly affected by the characteristics of the photocurable adhesive itself, and the change over time after curing will be affected. Also, the temperature change is large, and the shrinkage rate during curing is also large. On the other hand, if more granules are mixed, the flowability of the adhesive will deteriorate,
In addition, there is a risk that coarse particles may hinder fine adjustment during positioning. Figure 9 shows photocurable resin (Amicon UV990/30)
This is a graph showing the relationship between the glass bead content of a mixture of and glass beads (#80) and the thermal expansion coefficient of the cured product. Expansion coefficient decreases rapidly. Note that 0.8 parts by weight of glass beads per 1 part by weight of resin corresponds to 44% by weight in FIG. The higher the bead blending ratio, the smaller the thermal expansion coefficient of the cured product, but if it exceeds 2.5 parts by weight (71% by weight), the blend loses its fluidity and flows into the adhesive clearance poorly, making it impractical. . The photocurable adhesive and the inorganic transparent particles may be mixed when used for adhesion, but they may also be mixed in advance and prepared as an adhesive composition. Other additives may be added to the adhesive for precision fixing of parts of the present invention as long as they do not significantly impair the effects of the present invention. In general, a clearance of 0.2 to 0.5 mm is sufficient for adjusting the position of the bonded parts, so the diameter of the inorganic transparent particles mixed in the above precision fixing adhesive that is applied to this clearance is 40 to 40, depending on the adhesive clearance
Particles with a particle size in the range of 400 μm are used, and those with an average particle size of about 200 μm are generally versatile. The adhesive may be applied to the adhesive clearance before the parts are aligned or after the parts are precisely aligned. If the adhesive is distributed evenly within the adhesive clearance and it is necessary to avoid uneven distribution of the mixed transparent particles, the adhesive area on the base, for example, in the receiving groove 8, should be prepared before positioning the parts. Place the required amount of adhesive on the surface, place the parts on top of it, and align the parts. Alternatively, adhesive may be placed on both edges of the receiving groove 8 after the components are aligned in the receiving groove 8 without adhesive. In this case, the shrinkage due to photocuring occurs evenly on both sides of the bonded part and is balanced, and there is no shrinkage fluctuation in the vertical direction, so it is possible to minimize the variation in the fixing position of the part due to the curing of the adhesive. It is convenient to use a fine movement table for precise positioning of parts. FIG. 2 is an explanatory diagram of a situation in which the rod lens is finely adjusted in the coupling between the laser diode and the optical fiber shown in FIG. The output light emitted from the laser diode 1 by the input from the drive circuit 11 is focused on the optical connector 3 by the rod lens 2, and the coupling efficiency is determined by converting the light incident on the optical fiber 4 of the optical connector 3 to the optical sensor 12. The light is detected by the optical power meter 13 and read by the optical power meter 13. As shown in Fig. 1, a base 7 is fixed at the position of the rod lens 2, and in its receiving groove 8, 1 part by weight of ultraviolet curable adhesive and 2 glass beads #80 (particle size 177 to 250 μm) are placed. The necessary amount of adhesive containing the weight part is placed, and on top of that, a suspension rod 5 temporarily attached to the side of the rod lens 2 with instant adhesive leaves the rod lens 2 with an adhesion clearance of about 0.25 mm. It is placed in the receiving groove 8 with its optical axis aligned (FIG. 1). The suspension rod 5 which is temporarily attached to the rod lens 2 is supported by the arm jig 16 of the fine movement table 15 which is fixed at a suitable place with a magnetic stand 14, and the manipulators 17, 18 and 1 of the fine movement table
Operate 9 to move the rod lens left and right (X direction),
Finely adjust up and down (Y direction) and front and back (Z direction),
The position where the incident light from the optical connector 3 becomes maximum is determined by reading the optical power meter 13. The operation using the fine movement table 15 can also be performed by applying rotational motion to the suspension rod 5 or the arm jig 16, or by attaching a rotation stage to adjust the inclination of the component. It is also possible to automate these fine adjustments using a step motor that is linked to the output of the optical power meter 13. When the positioning of the rod lens 2 is completed so that the maximum output can be obtained from the optical power meter 13, the adhesive 9 placed in the receiving groove 8 is irradiated with curing ultraviolet rays to harden the adhesive 9. In this case, if the fixed position of the rod lens sinks due to curing and shrinkage of the adhesive, please use the fine movement table 15 in advance before irradiation.
Operate Rod Lens 2 and set the correction amount to 1.5.
It is necessary to lift it in the Y-axis direction by about 2.5 μm. Since this correction amount varies depending on the adhesive 9 used and the width of the adhesive clearance, it is desirable to measure it in advance. The curing ultraviolet rays are irradiated as shown in Figure 3.
Ultraviolet lamps 21 and 22 from diagonally above the adhesive 9
This is done by Although it is desirable to irradiate from both sides of the bonded portion, sufficient curing can be achieved even from only one side. It is usually irradiated for 5 to 10 minutes, left for a few minutes, and then reirradiated for 3 to 5 minutes to ensure hardening.
Irradiation can also be performed using a fiber optic bundle. After the adhesive 9 has completely hardened, remove the rod lens 2.
Remove the temporary adhesive 6 of the hanging rod 5 that was temporarily attached. The adhesive used for temporary bonding 6 is one that easily loses adhesive strength when heated, such as pine tar or wax.
Adhesion using cyanoacrylate instant adhesive
This method is advantageous because it is quick and reliable, and the adhesive can be easily released by heating the hanging rod 5. When removing the suspension rod 5, if you move the suspension rod 5 before the adhesive is sufficiently released, there is a risk of impacting the fixed optical components and causing fluctuations in the adjusted position. A spring-equipped arm jig 16 as shown in FIG. 4 is used. That is,
The base of the arm jig 16 is rotatably locked to the fine movement table 15 by a pin 23, and the middle part of the arm jig 16 is pushed upward by a spring 25, and is pushed down by a knob 24. It is fixed. When heating the hanging rod 5 after the adhesive 9 has hardened, if the knob 24 is loosened, when the adhesive force of the temporary adhesive 6 is sufficiently weakened, the temporary adhesive 6 will come off due to the force of the spring, as shown by the dotted line in the figure. , the hanging rod 5 fixed to the tip of the arm jig 16 escapes upward. By appropriately selecting the force of the spring 23, the suspension rod 5 can be removed with almost no effect on the optical axis of the fixed rod lens 2. A cross-sectional view of the rod lens 2 fixed by the above-mentioned fixing method taken at right angles to the optical axis is shown in FIG.
Moreover, the micrograph is shown in FIG. 5, 2. In FIG. 5, the clearance between the rod lens 2 and the receiving groove 8 of the base 7 is about 0.25 mm, and the glass beads 10 are evenly dispersed in the hardened adhesive 9. In FIG. 5, the glass beads appear as a black shadow against the transmitted light, and only the cut surfaces are shown as white circles. The blending ratio of glass beads in this photo is 2. As is clear from this photomicrograph, the clearance is well packed with glass beads, forming a block similar to a stone wall. Therefore,
Even if the resin component shrinks when the adhesive hardens, the stone wall-like block of glass beads is not affected, and the rod lens 2 is supported without changing its position until the adhesive hardens. This stone wall structure reduces the expansion and contraction of the adhesive layer even when the temperature changes after curing. As the content of glass beads decreases, the number of individual glass beads suspended in the resin component increases, and the stone wall structure decreases, resulting in shrinkage during curing and movement of support positions due to temperature changes after curing. becomes larger. In addition, as the particle size of glass beads becomes smaller, it is necessary to increase the number of points of contact between the beads in order to create a strong stone wall structure.As a result, the fluidity of the blended resin deteriorates, and If the glass beads are held at a higher temperature, mutual contact between the glass beads will be reduced, and the influence of expansion and contraction of the resin itself will be greater. The effect of using the adhesive for precision fixing of parts of the present invention, which is a photocurable adhesive mixed with inorganic transparent particles, for precision fixing of parts can be confirmed by the following experiment. Experiment 1 Figure 6 shows that when a cylindrical part is fixed in a receiving groove, 5 g of photocurable adhesive (UV-990-30 manufactured by Amicon) placed in the adhesive clearance is
7.5g of ~240μm glass beads (weight ratio 1:1.5),
7.5 g of silicic anhydride (SiO ₂ ) powder of 3 to 20 μm and 3 to 20 μm
7.5 g of 20 μm alumina (Al ₂ O ₃ ) powder were mixed together and cured by ultraviolet irradiation. When a transparent object such as a rod lens was used as the part to be bonded, all three types of adhesive showed sufficient curing, but when an opaque object such as a copper rod was used as the part, Only the adhesive containing glass beads was sufficiently cured, whereas in the other two cases uncured portions remained at the bottom of the parts. Experiment 2 In addition, as shown in Figure 7, three types of mixed adhesives similar to those used in the above test were filled into an opaque cup, and ultraviolet rays were irradiated with an intensity of 400 μW/cm ² .
The curing depth A of the adhesive after irradiation for 60 minutes was 4 mm in the case of the glass bead mixture, whereas curing was observed only up to 0.5 mm from the surface with the other two types. Experiment 3 The amount of glass beads used in Experiment 1 was adjusted to 0.5 and 2.7 by weight to the photocurable adhesive.
As a result of using the method described in Experiment 1, when using at a weight ratio of 0.5,
The thermal expansion of the adhesive after curing is large, making it impractical as an optical component, for example in the case of a rod lens.
Also, when used at a weight ratio of 2.7, the adhesive becomes putty-like and has poor flow when applied.
It was impractical. FIG. 8 shows an outline of an apparatus for measuring the change in coupling efficiency due to the precision fixing method of optical components by coupling between optical fibers.
2 leads to the optical connector 34 fixed on the case 33. An optical connector 35 is fixed to the case 33 facing the optical connector 34, and the two are coupled by a self-cleaning lens 36, and the coupling efficiency is calculated by measuring the coupling efficiency of the optical connector 35.
The measurement was performed using an optical sensor 38 and an optical power meter 9 using an optical fiber 37 from the source. Selhotsu Cleanse 3
6 is temporarily attached to the suspension rod of a spring-loaded arm jig as shown in Fig. 4 using Aron α253, the optical axis is aligned, and the coupling efficiency before bonding with various adhesives and the fine movement table are removed after bonding. The amount of change between the binding efficiency and the binding efficiency was measured. In addition, the amount of variation due to temperature change in the coupling efficiency between the obtained fibers was measured from 5℃ to 40℃.
The temperature was determined by changing the temperature in 6-hour cycles. These results are shown in Table 1. We also measured similar coupling efficiency changes for the LED module shown in Figure 2, but Table 1
When using the same photo-curing adhesive used in Nos. 1 and 2 and fixing with 10 minutes of irradiation and 1.5 minutes of re-irradiation, the change in coupling efficiency was 0.08 dB, which was 5 to 40 dB.
The amount of variation due to the temperature test in °C was 0.2 dB. The adhesive for precisely fixing components of the present invention is particularly suitable for precisely positioning and fixing optical components, but is also extremely effective for adhesively fixing not only optical components but also components that require precise positioning.

[Table] Two-component chemical curing type: Tall Seal [Effects of the invention] The adhesive for precision fixing of parts of the present invention has appropriate viscosity due to the combination of inorganic particles, and does not harden until it is irradiated with light, so It is easy to align, and moreover, it is quickly cured by light irradiation after alignment. In addition, since the blended particles are transparent, light can reach the inside of the adhesive, and curing progresses uniformly and quickly, eliminating the risk of positioning fluctuations during curing due to external vibrations and other influences. few. In addition, the ability of light to reach the adhesive is excellent, and it is possible to cure the entire part by irradiating a part of the adhesive, so it is possible to bond inside a device, which was previously difficult to do, by irradiating it with optical fiber, etc. This is possible by using Since the amount of inorganic transparent particles blended is approximately equal or more in weight to the amount of photocurable adhesive, the volume change during curing or temperature change is close to that of the bonded parts. There are very few changes in positioning. Fixing of parts using the adhesive for precision fixing of parts of the present invention takes approximately 30 minutes, including positioning using a fine movement table, etc.
The process can be completed within minutes, and the bonding efficiency is as good as that of the conventional method using Tall Seal adhesive, which requires 8 hours or more for bonding. Furthermore, it exhibits extremely excellent stability against temperature changes after fixation.

[Brief explanation of drawings]

Fig. 1 shows the connection using the rod lens in the LED module, and Fig. 2 is an explanatory diagram of the optical axis alignment using the fine movement table. FIG. 3 is an explanatory diagram of ultraviolet irradiation, and FIG. 4 is a longitudinal sectional view illustrating the operation of the spring-equipped arm jig. FIG. 5 1 is an enlarged sectional view of a rod lens fixed with the adhesive for precision fixing of parts of the present invention, and FIG. 5 2 is an enlarged photograph showing the particle structure of the adhesive in that part. FIGS. 6 and 7 are diagrams illustrating a method for testing photocurability of formulations. FIG. 8 shows an apparatus for measuring coupling efficiency between optical fibers. FIG. 9 is a graph showing the relationship between the thermal expansion coefficient of the cured adhesive and the glass bead content. The correspondence between the main parts illustrated and the symbols is as follows. 1... Light emitting diode, 2... Rod lens,
3... Optical connector, 4... Optical fiber, 5... Hanging rod, 6... Temporary adhesion, 7... Base, 8... Receiving groove, 9... Adhesive, 10... Optical sensor, 11... …
Drive circuit, 12... Optical sensor, 13... Optical power meter, 14... Magnetic stand, 15...
Fine movement table, 16...Arm jig, 17, 18, 19
... Manipulator, 21, 22 ... Ultraviolet lamp, 23 ... Pin, 24 ... Knob, 25 ... Spring, 31 ... Light source, 32, 37 ... Optical fiber,
33... Case, 34, 35... Optical connector, 3
6... Self-cleaning lens, 38... Optical sensor, 3
9...Optical power meter.

Claims (1)

[Scope of Claims] 1. An adhesive for precision fixing of components that is mainly composed of a photocurable adhesive and inorganic transparent particles, in which most of the inorganic transparent particles are in the range of 40 to 400 μm, and the photocurable Exceeding 0.8 parts by weight per 1 part by weight of mold adhesive,
An adhesive for precision fixing of parts, characterized in that the adhesive is blended in an amount of 2.5 parts by weight or less. 2. The adhesive for precision fixing of parts according to claim 1, wherein the photocurable adhesive is UV curable. 3. The adhesive for precision fixing of parts according to claim 1 or 2, wherein the inorganic transparent particles are glass beads.