JP2008037947A - Bonding method and optical head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bonding method improving a step of bonding components or the like and thereby efficiently progressing the step. <P>SOLUTION: In a bonding method comprising bonding one adherend 13 to another adherend 21, those parts of the adherends 13 and 21 at which they are bonded are bonded with a thermosetting adhesive 23 which can cure at 75°C or lower. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bonding method and an optical head, for example, a bonding method used in a bonding process of components necessary for performing data recording and reproduction on an optical disk, and an optical head including components bonded by the bonding method.

Conventionally, a technique using a UV adhesive that can be cured in a short time using ultraviolet irradiation (ultraviolet curable adhesive: UV [Ultra Violet]) has been proposed. In the ultraviolet irradiation device described in Patent Document 1, the temperature of the work table surface is controlled by a Peltier element, UV adhesive is applied to a member heated on the surface, and ultraviolet rays that pass through a heat ray cut filter are irradiated on the surface. To cure the adhesive. In the bonding method described in Patent Document 2, the conductive silicone rubber composition is self-heated by energizing the conductive silicone rubber composition, and the conductive silicone rubber composition is cured by this heat to adhere the adherends to each other. It is to be glued. Patent Document 3 describes a method for bonding an optical component to an optical head resin member in which an optical component is irradiated with ultraviolet rays and then the optical component is bonded to the bonded surface using a UV adhesive. .
JP 2005-169624 A JP-A-6-157996 JP-A-8-147755

  However, when parts are bonded using conventional techniques, the thermosetting adhesive cannot be used as the main adhesive in the process. There are two main reasons for this.

  (1) When the adhesive is to be cured by external hot air or the like in a state where the component is positioned in the adjustment step, heat escapes to the metal component, and the cured state of the interface is not stable.

  (2) Similar to (1), in order to create a stable part, it is necessary to put the part in the oven together with the device or jig, and the thermal expansion and contraction of the jig and the thermal expansion between the part and the jig. Due to the difference in shrinkage, the positional accuracy of the parts deteriorates and the durability of the jig also deteriorates. In addition, since the overall temperature rises, the positional accuracy of the adjusted parts that have been assembled previously is displaced by the heat of the oven.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a bonding method and an optical head capable of improving work efficiency in a bonding process of components and the like, and allowing the process to proceed efficiently.

  According to one aspect of the present invention, in the bonding method for bonding one adherend and the other adherend, the portion where the one adherend and the other adherend are bonded is 75. There is provided an adhesion method characterized by being adhered by a thermosetting adhesive that cures at a temperature of 0 ° C. or lower.

  According to another aspect of the present invention, a light source that emits laser light, an objective lens that condenses the laser light emitted from the light source on the optical disc, and the objective lens is attached to the optical disc by Lorentz force. Objective lens drive provided with a plurality of coils driven in a radial direction and a normal direction, a lens holder holding the plurality of coils and the objective lens, and a wire support member connected to the lens holder via a wire And an optical head that includes an optical system that guides the laser light to the objective lens, and a base member for fixing the light source, the objective lens driving device, and the optical system, An optical head is provided in which a portion to which the base member is bonded is bonded by a thermosetting adhesive that is cured at 75 ° C. or lower.

  According to the present invention, by using a thermosetting adhesive, it is possible to reduce a gap between components constituting the optical head, and it is possible to hold an adhesive with high positional accuracy and to improve the efficiency of the bonding process. Can be achieved.

  Hereinafter, an adhesion method and an optical head according to embodiments of the present invention will be described with reference to the drawings. In the drawings, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  The bonding method according to the present embodiment uses a thermosetting adhesive as a component adhesive, and is used, for example, in a bonding process of components constituting an optical head.

  As shown in FIG. 1, the optical head according to the embodiment of the present invention is disposed so as to face the recording surface of the optical disk 12, and is arranged in the radial direction of the optical disk 12, that is, with arrows A and B by a movable support mechanism not shown. It is supported so as to be movable in each direction.

  The optical head 11 includes a semiconductor laser 13, an objective lens driving device 17 provided with at least an objective lens 15 and a lens holder 24, an optical system 14, a photoelectric converter 16, a flexible printed wiring board 18, and a printed wiring board 19. And a flexible printed wiring board 20.

  The semiconductor laser 13 is a light source that emits laser light. The objective lens 15 focuses the laser light emitted from the semiconductor laser 13 on the optical disk 12. The lens holder 24 and the objective lens driving device 17 will be described later. The optical system 14 guides laser light to the objective lens 15. The photoelectric converter 16 is a light receiving element. The flexible printed wiring board 18, the printed wiring board 19, and the flexible printed wiring board 20 are all connected to an external circuit or the like that performs modulation / demodulation processing of information data.

  The lens holder 24 holds a focus coil (focusing coil), a tracking coil (track coil), a tilt coil, and an objective lens 15 (not shown) that drive the objective lens 15 in the radial direction and the normal direction of the optical disc 12 by Lorentz force. To do.

  The lens holder 24 is connected to a wire holder (wire support member) that supports a wire or the like via a wire. The lens holder 24, the wire, the wire holder, the objective lens 15, and each coil for magnetic driving use the objective lens. A driving device 17 is configured. The optical head 11 is further provided with a base (base member) for relatively fixing the semiconductor laser 13, the objective lens driving device 17 and the optical system 14. This base will be described later.

  As a result, the optical head 11 irradiates the laser light modulated according to the recording information from the semiconductor laser 13 which is a light source, and condenses the laser light on the optical disk 12 via the optical system 14 and the objective lens 15. Information on the optical disk 12 is recorded.

  Further, the optical head 11 condenses a certain level of laser light emitted from the semiconductor laser 13 onto the optical disc 12 via the optical system 14 and the objective lens 15. Then, the optical head 11 causes the objective lens 15 to reverse (transmit) the laser light reflected on the optical disk 12, refracts the reverse laser light by the optical system 14, and photoelectrically converts the refracted light. The light is received by the device 16, thereby reproducing information from the optical disk 12.

  The objective lens 15 is supported by an objective lens driving device 17 so that focus control, tracking control, and tilt control can be performed. Each coil is connected to the printed wiring board 19 via the flexible printed wiring board 18 and performs focus control, tracking control, or tilt control for the objective lens 15.

  The semiconductor laser 13 is connected to a printed wiring board 19 through a flexible printed wiring board 20. Further, the photoelectric converter 16 is electrically and mechanically connected to the printed wiring board 19.

  The optical head 11 is electrically connected to an external circuit or the like via a printed wiring board 19, and controls the semiconductor laser 13 and the objective lens driving device 17 and signals generated by the photoelectric converter 16. Take out.

  Further, the lens holder 24 is housed in a base fixed to the objective lens driving device 17. The semiconductor laser 13 is bonded to this base. Made.

  In the bonding method according to the present embodiment, for example, one adherend such as the semiconductor laser 13 is bonded to the other adherend such as the base, and one adherend and the other adherend are bonded to each other. The part to be bonded is bonded by a thermosetting adhesive that is cured at 75 ° C. or lower. This thermosetting adhesive contains an epoxy resin as a main component.

  A thermosetting adhesive is applied in advance between a base made of metal and the semiconductor laser 13 which is a heating element. After application of the thermosetting adhesive, an LD (laser) for the semiconductor laser 13 is applied. Diode) adjustment is performed.

  In the LD adjustment process, a minute current is supplied from the power source to the semiconductor laser 13, the semiconductor laser 13 emits light, and the position and angle of the semiconductor laser 13 are adjusted using the emitted light.

  When the current close to the maximum rating is input to the semiconductor laser 13 after the adjustment is completed, the semiconductor laser 13 generates heat due to heat corresponding to the heat of loss in EO conversion (electrical-optical conversion). The adhesive is cured. As a result, as shown in FIG. 2, the semiconductor laser 13 is bonded and fixed to the base 21 as a structure of the objective lens driving device 17.

  An example of the voltage value and the current value will be described. When the semiconductor laser 13 is, for example, CW (continuous oscillation) and can output a maximum rating of 100 mW, the semiconductor laser 13 has a maximum considering some safety. In order to output 80 mW of light, which is 80% of the rating, a voltage of approximately 2.5 V and a current of 150 mA are required.

  At this time, the semiconductor laser 13 generates heat by heat corresponding to the heat loss of EO conversion. For the sake of rough estimation, if the power other than the light output is converted into the heat generation, 2.5V * 150 mA = 360 mW, and therefore 360 mW-80 mW = 240 mW of power is applied to the thermosetting adhesive 23. Contributes to the temperature rise. As an example, the temperature of the semiconductor laser 13 increases by about Δ50 ° C., although it varies depending on the state of heat radiation to the jig for adjusting the semiconductor laser 13.

  As described above, in the bonding method according to the present embodiment, the adhesive resin is cured using the heating element, whereby the components constituting the optical head 11 such as the objective lens driving device 17 are bonded.

  Further, 90% or more of the total area of the parts to be bonded is bonded by the thermosetting adhesive 23. In the step of temporary bonding using a UV adhesive, 10% or more of the total bonding area is necessary. For this reason, by using the bonding method according to the present embodiment, the bonding process can be advanced without using a thermosetting adhesive for a part of the total bonding area.

  In addition, in the bonding method according to the present embodiment, the thermosetting adhesive 23 achieves (a) a portion where the degree of curing progress is 5% or more at (a) 75 ° C. (c) within 10 minutes. Is.

  (A) It demonstrates further that the thermosetting adhesive 23 shall be 75 degreeC. In general, the temperature of the laser diode is guaranteed up to 75 ° C., and if the laser diode outputs a large light output at a high temperature, the internal temperature of the laser diode itself rises and LD light emission cannot be performed due to deterioration. On the other hand, since the thermosetting adhesive cures faster when the temperature is higher, it is desirable to cure the adhesive at a higher temperature from the viewpoint of shortening the working time in the process. In addition, when the curing temperature of the adhesive is 40 ° C. or 50 ° C., there is a problem that the curing starts even under conditions of about room temperature. Therefore, an adhesive having a curing temperature of 40 ° C. or 50 ° C. is used. Sometimes it is necessary to control the temperature of the adhesive. For this reason, the thermosetting adhesive 23 according to this embodiment is set to 75 ° C.

  (B) The reason why the thermosetting adhesive 23 having a degree of curing progress of 5% is used in the bonding method according to this embodiment will be described. In order to shorten the occupation time for the operation of the adjusting device (adjusting machine), the adhesive is preferably cured within, for example, 1 minute after heat generation, but an adhesive that is completely cured in a short time of 1 minute is used. If temperature control is very difficult.

  For this reason, the bonding method according to the present embodiment uses an adhesive that is completely cured at 75 ° C. in 30 minutes, the progress of curing proceeds to some extent, and the position of the adherend such as the semiconductor laser 13 is maintained. Even if the jig of the adjusting device is removed, the adherend is cured until it does not move.

  That is, in the bonding method according to the present embodiment, the thermosetting adhesive 23 is injected between the semiconductor laser 13 and the base 21, and the thermosetting bonding is performed until these two adherends do not move. The adhesive 23 is cured, and the cured thermosetting adhesive 23 is further heated together with the semiconductor laser 13 and the base 21 to bond the two adherends. When the two adherends are in a state where they do not move, as another process, the adherends that have not been moved are placed in an oven or the like to be completely cured.

Next, an estimate of the degree of progress of curing necessary to maintain the position of the semiconductor laser 13 as the adherend is estimated. The Young's modulus of the epoxy resin is about 300 kg / mm ² . When the mass of the heating element is 5 g, the external force applied to the heating element is 0.5 kg considering the weight of the heating element and the point that the external force 10G applied to the heating element is generated during work.

The bonding area is 2 mm * 5 mm = 10 mm ² on one side based on the component sizes of the two adherends. Since the two adherends have a strength corresponding to a 5% cured region, the adhesion area contributing to the adhesion strength at the time of 5% curing is 10 mm ² * 0.05 = 0.5 mm ² . .

Therefore, since stress = external force / area, stress is obtained as 0.5 kg / 0.5 mm ² = 1.0 kg / mm ^2, and since strain = stress / Young's modulus, strain is 1.0 / 300 = 0.003.

  On the other hand, when the distance between the two adherends is 2 mm, it is required as accuracy to suppress the magnitude of the change in the position of the adherend to 10 μm or less. For this reason, the strain needs to be 0.01 / 2 = 0.005 or less. From the above, in the bonding method according to the present embodiment, the adjusting device can hold the component including the adherend by using the thermosetting adhesive 23 having a degree of curing of approximately 5%. In addition, the adhesion method according to the present embodiment may use a thermosetting adhesive having a degree of progress of about 3% from the above estimation. In addition, when the adjusting device can hold the adherend according to the weight of the component, etc., the bonding method according to this embodiment uses a thermosetting adhesive having a degree of progress of approximately 1%. You can also. For this reason, the bonding method according to this embodiment uses a thermosetting adhesive 23 having a degree of curing progress of 5%.

  (C) In the bonding method according to the present embodiment, the reason that the progress of curing of 5% or more is achieved within 10 minutes at 75 ° C. is that the occupation time of the adjusting device is better as it is smaller. This is because, for example, an occupation time of 10 minutes is sufficient in consideration of work efficiency and convenience in the bonding process.

  As described above, according to the present invention, at 75 ° C., the curing of 5% or more of the thermosetting adhesive 23 proceeds, and the progress of the curing is achieved within 10 minutes. A highly reliable optical pickup using the agent 23 can be configured.

  Further, as shown in FIG. 2, the optical head 11 according to the present embodiment includes one or both of the two semiconductor lasers 13 and the base 21, or the semiconductor laser 13 and the base 21. All or a part of the heater is composed of a heating element. In the bonding method according to this embodiment, first, either one or both of one adherend and the other adherend are heated, or one adherend and the other adherend are All or a part of them is heated, and the two heated adherends are bonded by the thermosetting adhesive 23.

  Further, the semiconductor laser 13 is self-heated by energizing the semiconductor laser 13. When the semiconductor laser 13 itself, which is an adherend, is energized and generates heat, the thermosetting adhesive 23 is cured, so that the temperature can be increased only in the area of the adherend, In the process, the adherend or the thermosetting adhesive can be raised to a preset temperature in a short time.

  The present invention has the following two effects.

  (1) The UV bonding method, which is a bonding method using a UV adhesive, is good in terms of work, but in order to irradiate the UV adhesive with UV light, irradiation of the UV adhesive 24 as shown in FIG. It is necessary to provide a gap between the components for curing the portion that becomes the shadow of the film. Since the Young's modulus of the adhesive resin is lower than the Young's modulus of the structure, when the UV adhesive 24 is used, the adhesion reliability is lowered.

  When a conventional method of curing a thermosetting adhesive in an oven is used, curing of the adhesive in the jig is required while the adhesive is cured in the oven. Moreover, it is not reliable to place such members and adherends in an oven after attaching the members affected by heat and dust such as optical components to the adherends.

  According to the present invention, a gap between components constituting the optical head 11 can be reduced, and a thermosetting adhesive, particularly an epoxy resin functioning as a thermosetting three-dimensional cross-link is used. Adhesive holding with high positional accuracy is possible.

  (2) It is necessary to fill a space between the heating element and the structure that transfers the heating element with a material having high thermal conductivity. If this material having high thermal conductivity is not used, heat is diffused. I can't. Therefore, in the adhesion method using a cured gel or the like, the position of the gel itself cannot be maintained, and reliability is poor.

  Further, when a UV curable adhesive is used, it becomes a shadow of UV light irradiated by the adhesive, so that the adhesive between the objects that are adherends cannot be cured. When a thermosetting adhesive is used and a normal bonding method is used, the above-mentioned problem (1) is caused. When a curing method using an RTV-based adhesive such as moisture curing is used, it takes about one day to cure the adhesive, and the reliability is still poor.

  On the other hand, the bonding method according to the present embodiment contains a filler having a heat dissipation property or high thermal conductivity, for example, a thermosetting containing a filler having a good thermal conductivity such as a metal oxide such as alumina or a ceramic. A mold adhesive is used. A general value can be used for the thermal conductivity of the filler. The thermal conductivity of a resin containing a filler having a good thermal conductivity varies according to the mixing ratio of the resin and the filler. In addition, since this mixing ratio is a ratio between the resin and the filler as an adhesive, the bonding method according to the present embodiment is based on the policy of which of adhesiveness or heat dissipation predominates, The mixing ratio can be changed. Thus, the thermosetting adhesive contains a filler having a heat dissipation property or a predetermined thermal conductivity, and the thermal conductivity of the thermosetting adhesive can be adjusted according to the content ratio of the filler. .

  In addition, the bonding method according to the present embodiment can also include a heat-dissipating resin that is cured at a low temperature by the thermosetting adhesive, and the curing of the adhesive is prevented when using an adhesive that cures at a low temperature. Therefore, it is desirable to employ a dispenser equipped with a temperature controller (temperature control device). This dispenser supplies an appropriate amount of thermosetting adhesive. Thus, the thermosetting adhesive can also contain a filler and a resin that can be cured at a low temperature.

  Therefore, according to the present invention, the heat dissipation filler and the low-temperature-curing heat-dissipating resin contained therein can be used and cured by the self-heating of the heating element, so that the heat conduction can be increased. Become.

  As described above, according to the present invention, since the adherend itself is energized and cured by generating heat, the temperature can be increased only in the non-attached portion, and the set temperature can be reached in a short time. be able to. It can be said that the bonding method of this embodiment is to cure a thermosetting adhesive by using heat generation.

  Furthermore, according to the present invention, the adherend can be energized by a simple method, and a thermosetting adhesive can be used regardless of the ratio of the filler contained. In the bonding method of the present invention, the effect of heat dissipation can be enhanced by adding a filler having good thermal conductivity to the thermosetting adhesive.

  Conventionally, a thermosetting adhesive is not used as a main adhesive, but temporary bonding and main bonding using a UV adhesive have been adopted. When a bonding process is advanced using a UV adhesive, Items.

  (A) When a UV adhesive of UV curable resin is used, a portion that does not receive UV irradiation or a portion that becomes a shadow is generated, and these portions are uncured, so that the region that can be bonded is limited.

  (B) When a UV acrylic UV adhesive is used, when the temperature of the UV acrylic UV adhesive becomes high, the adhesive resin becomes flexible, and it is difficult to maintain the posture of the parts and the like during heat generation.

  (C) UV epoxy UV adhesive is accelerated by UV heat, but heat is dissipated when bonding metal parts, and the interface tends to be uncured. In addition, bonding using a UV epoxy UV adhesive has a larger amount of uncured residue compared to heat curing, which becomes an unstable factor.

  (D) Both the UV adhesive and the heat radiation agent are applied to the component, and both the UV adhesive and the heat radiation agent affect the performance of the component depending on the application area to the component. Contrast with heat dissipation.

  On the other hand, according to the present invention, it is possible to produce a highly reliable optical pickup that is free from defects in work or process using a thermosetting adhesive without using a UV adhesive.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, in the above-described embodiment, the semiconductor laser 13 is self-heated, but the present invention can also be configured to self-heat a heat-generating component among the components constituting the optical head 11 by energization or the like.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a figure which shows the structural example of the optical head which concerns on one Embodiment of this invention. It is a figure for demonstrating the adhesion | attachment method which concerns on one Embodiment of this invention. It is a figure for demonstrating the conventional adhesion | attachment method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Optical head, 12 ... Optical disk, 13 ... Semiconductor laser (one adherend, light source), 14 ... Optical system, 15 ... Objective lens, 16 ... Photoelectric converter, 17 ... Objective lens drive device, 18 ... Flexible printing A wiring board, 19 ... a printed wiring board, 20 ... a flexible printed wiring board, 21 ... a base (the other adherend, a base member), 23 ... a thermosetting adhesive, 24 ... a UV adhesive.

Claims (12)

In the bonding method of bonding one adherend and the other adherend,
A bonding method, wherein a portion where the one adherend and the other adherend are bonded is bonded by a thermosetting adhesive that is cured at 75 ° C. or lower.   The bonding method according to claim 1, wherein 90% or more of the total area of the bonded portions is bonded by the thermosetting adhesive.   2. The bonding method according to claim 1, wherein the bonding is bonding using the thermosetting adhesive containing an epoxy resin as a main component.   The curing of 5% or more of the thermosetting adhesive proceeds at 75 ° C., and the curing of the 5% or more of the part is achieved within 10 minutes. Item 2. The bonding method according to Item 1. Either one or both of the one adherend and the other adherend, or all or part of the one adherend and the other adherend are heated,
2. The bonding method according to claim 1, wherein the one adherend that has generated heat and the other adherend are bonded together by the thermosetting adhesive.   6. The bonding method according to claim 5, wherein the one adherend or the other adherend is self-heated by energizing the one adherend or the other adherend. Injecting the thermosetting adhesive between the light source and the base member,
Curing the thermosetting adhesive until the one adherend and the other adherend are in a stationary state;
The one adherend and the other adherend are bonded together by further heating the cured thermosetting adhesive together with the one adherend and the other adherend. The bonding method according to claim 1. A light source that emits laser light, an objective lens that condenses the laser light emitted from the light source on an optical disc, and a plurality of coils that drive the objective lens in a radial direction and a normal direction of the optical disc by Lorentz force An objective lens driving device provided with a lens holder for holding the plurality of coils and the objective lens, and a wire support member connected to the lens holder via a wire, and supplying the laser light to the objective lens An optical head comprising a guiding optical system, and a base member for fixing the light source, the objective lens driving device, and the optical system,
An optical head, wherein a portion where the light source and the base member are bonded is bonded by a thermosetting adhesive that is cured at 75 ° C. or lower.   The optical head according to claim 8, wherein the thermosetting adhesive contains an epoxy resin as a main component.   9. The optical head according to claim 8, wherein any one or both of the light source and the base member, or all or a part of the light source and the base member are heating elements.   The thermosetting adhesive contains a filler having a heat dissipation property or a predetermined thermal conductivity, and the thermal conductivity of the thermosetting adhesive can be adjusted according to the content ratio of the filler. The optical head according to claim 8.   The optical head according to claim 11, wherein the thermosetting adhesive contains the filler and a resin curable at a low temperature.

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