JP4099135B2 - Manufacturing method of reflection mirror - Google Patents

Description

The present invention relates to a method of manufacturing a reflecting mirror that is used by being attached to a rocking device that can be preferably used, for example, when a large number of pores are formed at predetermined positions on a printed circuit board.

  In a reflection mirror such as a scan mirror used in an optical system of a conventional laser processing machine, for example, it has a center of gravity on the same axis as the swing axis, swings around the swing axis, and reflects the incident laser beam on the reflection surface. Reflective mirrors are known. In this reflecting mirror, the outer contour of the reflecting surface viewed from the front is parallel to the elliptical contour portion and the elliptical contour portion along the contour of the elliptical reflection spot for the incident beam incident at a predetermined incident angle and parallel to the swing axis. By removing the mirror material in the area that is not necessary for the reflection of the laser beam by having a straight line outline, the moment of inertia around the oscillation axis is reduced, and the response speed of the movement of the reflecting mirror is increased. It avoids interference with other parts, and contributes to miniaturization of the optical system (see, for example, Patent Document 1).

  On the other hand, similarly, in a reflection mirror having a center of gravity coaxially with the swing axis, swinging around the swing axis and reflecting the incident laser beam on the reflection surface, the material of the reflection mirror is made of beryllium, and the mirror The back side of the tube has a rib structure to reduce weight and rigidity, and to achieve higher-speed rocking motion, and by cutting out part of the rib structure and part of the ribs around the back structure, An invention that prevents the distortion due to the tightening force of the attachment part to the scanner), ensures the flatness of the reflecting surface, and maintains the shape of the reflected laser beam (machined hole shape, roundness). It is disclosed (see, for example, Patent Document 2).

JP 2000-347113 A (page 3 to page 4, FIG. 1) JP 2001-116911 A (page 4, FIG. 1)

  In the conventional reflecting mirror described in Patent Document 1, the material is made of a lightweight material such as silicon or beryllium, and is designed to follow the high-speed operation of the scanner. The short axis is 20 to 25 mm and the major axis side is 30 to 35 mm. If the reflecting mirror is enlarged, the mirror will bend and vibrate due to the acceleration of rotation around the oscillation axis. However, there is a problem that the roundness distortion of the reflected beam is not generated. Moreover, since beryllium metal has toxicity, there is a concern about the influence on the global environment. In addition, the development of scan mirrors using materials that replace beryllium is desired because of the preciousness of materials and the difficulty in obtaining them because they only rely on imports from overseas.

  On the other hand, since the material of the reflecting mirror described in Patent Document 2 is beryllium, there are environmental problems and availability problems as in Patent Document 1. In addition, cutting out the rib near the mounting part causes insufficient rigidity of the mounting part, resulting in deterioration of responsiveness due to an increase in rocking speed (deterioration of the roundness of the reflected beam due to distortion of the reflecting surface). There was a problem.

The present invention has been made to solve the above-described problems of the prior art, and is formed by integrally forming a reinforcing structure portion by processing and molding ceramics mainly composed of boron carbide (B ₄ C). An object of the present invention is to provide a method of manufacturing a reflection mirror that can be used in a high-speed rocking system easily and at low cost, can be made larger than before, and can be manufactured by electric discharge machining .

The method of manufacturing a reflecting mirror according to the present invention includes a reflecting mirror in which a base portion having a reflecting surface formed on the surface and a reinforcing structure portion provided on the back surface of the base portion to prevent distortion of the base portion are integrally formed. In the above, the constituent material of the base portion and the reinforcing structure portion is a composite of boron carbide (B ₄ C) and chromium boride (CrB ₂ ), or a composite of boron carbide (B ₄ C) and titanium boride (TiB ₂ ). A method of manufacturing a reflecting mirror, characterized in that a composite of boron carbide (B ₄ C) and chromium boride (CrB ₂ ), or boron carbide (B ₄ C) and titanium boride ( A step of forming a reinforcing structure part constituting the reflecting mirror from a composite of TiB ₂ ) by electric discharge machining, and a step of optically polishing a surface to be a reflecting surface on the opposite side of the reinforcing structure part to a required surface roughness. Is included.

According to the present invention, ceramics mainly composed of boron carbide (B ₄ C) are processed and molded to integrally form the reinforcing structure, and can be used for a high-speed oscillation system that is environmentally friendly and low-cost. In the production of a reflective mirror that can be manufactured by electric discharge machining, the reinforcement structure can be easily formed by electric discharge machining, and the reflection mirror can be manufactured to ensure the required flatness by polishing. You can get the method.

Embodiment 1 FIG.
A first embodiment of the present invention will be described below with reference to FIGS. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.
As shown in FIG. 1, in a laser processing machine for drilling a printed circuit board 2 that is a workpiece, a processing laser beam (optical path) 6 emitted from a laser oscillator 1 is moved to a processing position. Axis reflecting mirror 100 and Y axis reflecting mirror 200, a condenser lens (described as an f-θ lens or referred to as an “F-theta lens”) 5, and other reflecting optics for guiding light, although not shown. Has a system. The X-axis reflection mirror 100 is fixed to the X-axis scanner 3, and the Y-axis reflection mirror 200 is fixed to the Y-axis scanner 4. In this optical system, it is the rocking speed around the rotation axes (X axis and Y axis) of the reflection mirrors 100 and 200 that determines the drilling processing speed (the number of processing holes per unit time).

  The swing angle around the rotation axis is generally in a narrow range of about plus or minus 7 to 8 degrees, but in a printed circuit board (for example, a build-up board used for a circuit board such as a mobile phone) that realizes a multilayer structure by a lamination method. The number of holes to be processed is extremely large, and the X-axis and Y-axis reflecting mirrors 100 and 200 are oscillating synchronously at a frequency of about 1000 Hz. That is, about 1000 holes are processed per second. The reflection mirror 30 is deformed in the direction shown by the arrow 36 or 37 in FIG. 2 in the eigenvalue analysis result measured for the reflection mirror using beryllium, for example.

  The primary mode with the lowest natural vibration (arrow 36 in FIG. 2) is a deformation mode in which the reflecting mirror 30 bows in a direction perpendicular to the oscillating rotation shaft 35, and is the secondary mode that is the next higher mode. (Arrow 37 in FIG. 2) is a mode in which the entire reflection mirror 30 is twisted and deformed with respect to the swinging rotation shaft 35. Reference numeral 32 denotes a reflection surface (mirror surface) formed on the lower surface side in the figure. In order to suppress such deformation of the reflecting mirror, it is necessary to improve the dynamic rigidity of the mirror structure and increase the natural frequency. The simplest method is to select and use a material having a small density and a high Young's modulus. That is, since the higher the ratio of density and Young's modulus (specific rigidity), the more advantageous it becomes, so far, silicon has been mainly used in the past as a material for the reflection mirror, and recently beryllium.

The density (ρ) of beryllium is 1.85 g / cm ³ and the Young's modulus (E) is 275 GPa. If the specific rigidity is defined as E / ρ, the specific rigidity is 148.6. If the material has rigidity, a scanner mirror having a resonance frequency (eigenvalue) equivalent to that of a beryllium mirror should be able to be configured. However, there was no metal material having the same specific rigidity as the background that the reflecting mirror for the scanner could not be manufactured with materials other than beryllium. In order to realize high-speed oscillation at 1000 Hz even with the beryllium material, as shown in FIG. 2, a plurality of ribs 33 extending left and right from the central axis 31 of the back structure, which is the backbone of the mirror, on the side opposite to the reflecting surface 32 It is necessary to further increase the rigidity as a structure in which the peripheral ribs 34 are integrally provided, and in order to make this rib structure, it is essential that the metal material is easy to process.

However, due to the environmental problems associated with the toxicity of beryllium as described above and the problems of availability, it is desired to develop a high-rigidity reflective mirror that is composed of materials other than beryllium and is friendly to the global environment and can swing at high speed. It was. Although the present inventors have found that the ceramic material is very hard and free processing is difficult, for example, silicon carbide SiC (specific rigidity 131.3) or boron carbide B ₄ C (specific rigidity 172.0) is preferable in terms of specific rigidity. ) And other carbide-based ceramic materials are relatively close to beryllium materials, and if they can overcome the difficulty of processing, they will be able to use them in high-speed motion optical systems, and earnestly research them. As a result, the present invention has been completed.

  FIG. 3 is a perspective view schematically showing a reflecting mirror using the carbide-based ceramics according to the first embodiment of the present invention as a base material. The reflection mirror 200 according to the first embodiment is an integral structure made of a carbide-based ceramic material, and has a plate-like base portion 210 in which a reflection surface 211 that reflects laser light is formed on the front surface side (lower surface portion side in the figure). In addition, a reinforcing structure portion 220 that is formed on the back surface portion of the base portion 210 and prevents the base portion 210 from being bent or distorted is integrally formed. The reinforcing structure portion 220 includes a back structure central shaft portion 221 integrally provided on the back side of the base portion 210 along a swinging rotation axis (not shown), and the back structure central shaft portion 221 to the back side of the base portion 210. It is comprised from the rib 222 extended symmetrically along the surface right and left.

  As shown in FIG. 3, the reflection mirror 200 is smooth over almost the entire circumference except for the rear structure central shaft portion 221 and the small concave R-curved portion of the scanner and mirror attachment side root portion (near the arrow C portion). It consists of an outward bulge curve. A longitudinal dimension B1 shown by a double-headed arrow means a distance between adjacent ribs, B2 is a distance from the apex of the central axis to the first rib, and B3 is a generally smooth curve constituting the base portion 210. This means the distance from the portion (near arrow C) to the first rib.

  In the first embodiment, silicon carbide (SiC) is used as the base material of the constituent members of the reflection mirror 200. For example, about 50 mm in the rotation axis direction (the direction of arrow L in FIG. 3) and the width direction ( When a reflection mirror having a reflection area of about 40 mm in the direction of arrow W in FIG. 3 is formed, the base portion 210 forming the reflection surface 211 has a thickness (in order to reduce weight and increase the natural frequency). t) is set to about 0.5 mm or less, and about two ribs 222 having a thickness of about 1.0 mm and a height (h) of about 3.0 mm are provided symmetrically on the back surface as shown in the drawing. This shape is very simple compared to a conventional beryllium mirror, with a significantly smaller number of ribs, but this back structure has an important point of the present invention.

  When carbide-based ceramics is used as the material for the reflective mirror, the specific rigidity is almost the same as or slightly higher than that of beryllium. By adopting the back structure similar to beryllium, a natural frequency almost equivalent to beryllium should be obtained. . However, as a result of intensively promoting the trial production of a series of reflection mirrors and laser processing experiments, the present inventors have found that the performance of a reflection mirror using carbide ceramics is lower than that of a reflection mirror using beryllium. .

  For example, the beryllium mirror shown in FIG. 2 is a reflecting mirror having a reflecting surface length of 40 mm and a reflecting surface width of 30 mm in the direction of the oscillating rotation axis. When the eigenvalue analysis of this reflecting mirror is performed, the mirror bows. It can be seen that the primary mode is 2.24 KHz, and the eigenvalue of the primary mode has a margin of about twice the operating frequency of 1 KHz.

Therefore, as a test, a reflection mirror was made by making the material as carbide-based ceramics with the shape shown in FIG. 2 as it is, but the hole position processed by the laser is the design drilling position 300 indicated by the broken line as shown in FIG. On the other hand, for example, it was found that the machining hole 301 indicated by the solid line is shifted by Δp as schematically shown in the A column of FIG. Considerably larger than the SiC density of the ceramic ρ is 3.2 g / cm ³ or _{B 4} C density of the ceramic is 2.85 g / cm ³ and beryllium 1.85 g / cm ^3, which was used in the prototype as the cause, this Since this has some influence on the movement of the reflecting mirror, it was estimated that the deformation of the first mode of natural vibration occurred and the machining hole position was shifted.

  In order to increase the rigidity of the mirror, the height of the ribs was increased or the number of ribs was increased to construct a reflecting mirror. However, the roundness and irradiation position accuracy of the laser beam reflected by high-speed movement were completely different. It turned out that it could not be secured. For example, from a series of experiments in which the number of ribs was changed, it was found that the number of ribs and the positional deviation amount Δp had the relationship shown in FIG. In the reflection mirror made of SiC material having the same size as the 30 × 40 mm size of the beryllium material, when the back rib structure is arranged so that the reflection surface is divided at equal intervals, the positional deviation Δp is large when the number of ribs exceeds four. Thus, it was found that in the case of five ribs, the amount of Δp increases as the measurement range is exceeded.

  Originally, the increase in the number of ribs is considered to work in the direction of increasing the natural vibration in order to improve the structural strength, and it is considered that another factor is related to the deterioration of the positioning accuracy of the reflected light in the experimental results. For example, in order for the reflecting mirror to stably oscillate, its dynamic balance needs to be taken. As one of the conditions for obtaining the dynamic balance, the oscillating rotation axis needs to pass through the center of gravity of the reflecting mirror.

  In other words, the first condition for obtaining a stable oscillating motion is that the rotation center of the rotation axis of the scanner that drives the reflection mirror passes through the center of gravity of the reflection mirror. Due to the strict asymmetry of the right and left of the mirror, it can be said that the mirror cannot be perfectly balanced. In other words, the dimensional accuracy obtained by cutting is difficult to obtain with carbide ceramic mirrors compared to beryllium materials, and its specific gravity is large, so there is a slight asymmetry of the outer shape and the center of oscillation and rotation axis and the center of gravity of the reflecting mirror. It was thought that the centrifugal force generated by the rotation caused the reflecting mirror to be deformed because the shift greatly lost the dynamic balance.

  Therefore, although the rigidity of the reflecting mirror is reduced, the overall mass is reduced, and the number of ribs is reduced for the purpose of reducing the excitation force caused by the deviation between the swing rotation axis and the center of gravity of the reflecting mirror. As a result of the experiment, it was confirmed that the irradiation position accuracy of the reflected light was improved (for example, rows B and C in FIG. 4). Therefore, when the number of back ribs was changed to 2 to 3 and the gap between the ribs was changed to perform a laser drilling experiment, when the gap between the ribs was increased too much, for example, as shown in row D of FIG. The phenomenon that the shape of the material deteriorates has been recognized.

  This is because the natural vibration of the flat plate portion between the ribs has been lowered, so that the flat plate portion is slightly bent by the acceleration of the swinging rotation, or the vibration at the time of bending is not attenuated and remains. Presumed to be the cause. Actually, when the rib interval is widened, the roundness Δd of the processed hole is deteriorated, and in the reflection mirror having a reflection area of about 40 mm × 50 mm, the relationship between the rib interval and the roundness tends to be as shown in FIG. I found out that

As shown in FIG. 4, the roundness Δd is the difference between the diameter ΦMAX and the minimum inscribed circle ΦMIN of the maximum circumscribed circle of the processed circle, that is,
Δd = ΦMAX−ΦMIN.
Furthermore, from the above-described series of experimental results including the added experimental results, the rib is the reflective surface when a reflecting mirror is used to make a high-speed rocking motion of about 1000 Hz or more (approximately 800 to 1000 Hz or more) using carbide ceramics. It has been found that there is an appropriate range in the aspect ratio of the shape of the flat portion formed by partitioning the entire back surface of the plate.

  That is, the ratio of the dimension A to the dimension B (A / B) with respect to the distance B in the swing axis direction between the two adjacent ribs 222 shown in FIG. ) Is in the range of 0.5 to 2.0, the positional deviation of the machining hole is small and the roundness of the machining hole is maintained. Furthermore, in order to obtain a highly accurate machining hole position and the roundness of the machining hole, the ratio (A / B) of the dimensions A and B is desirably about 0.7 to 1.4. Incidentally, in the conventional beryllium mirror, the ratio of the dimensions A and B is approximately 2.0 or more.

  The ratio (A / B) tends to be slightly expanded when a boron carbide-based ceramic material having a slightly lower density than silicon carbide is used. It is equivalent. On the other hand, when using a normal scanner (oscillating motor) that drives the reflecting mirror, the weight of the reflecting mirror using carbide ceramics, which has a higher specific gravity than beryllium or silicon, is reduced due to the drive torque (reduced moment of inertia). ) Is essential, and it is desirable that the thickness (t) of the base portion 210 forming the reflecting surface 211 of the mirror be approximately 0.5 mm or less. More preferably, if it is 0.4 mm or less, it can be designed within an inertial mass that can secure a processing speed of 1000 to 1200 Hz or more with the driving torque of a currently used scanner. Needless to say, when the scanner drive torque is increased or a high-torque drive system is used, the reflective surface can be designed with a thickness exceeding 0.5 mm.

  From the above, the reflection mirror using the carbide-based ceramics according to the first embodiment has a representative shape as shown in FIG. 3 having a length (L) in the swing axis direction of 30 to 100 mm, and the swing axis direction. In the mirror having various combinations of lengths in the width direction (W) of the mirror perpendicular to the height of 30 to 100 mm, the rib 222 having a height of 2.0 to 4.0 mm and a width of 0.3 to 1.0 mm And the ratio of the rib interval B to the rib length A (A / B) is in the range of 0.5 to 2.0, so that the allowable range is obtained at a rocking speed of 800 to 1000 Hz. And the roundness of the machining hole within an allowable range can be obtained.

  Further, in the case of constructing a reflection mirror close to a rectangle with a width of about 30 mm and a length in the swing axis direction of 100 mm, three ribs 222 are provided, and the rib spacing to length ratio (A / B) is 0.5. By setting the value within the range of -2.0, it is possible to obtain a reflecting mirror having the most stable processing position accuracy and processing hole shape accuracy. As described above, in the present invention in which the reflecting mirror is composed of carbide-based ceramics, in order to overcome the difficulty of setting the scanner rotation axis and the reflecting mirror due to its higher density than the beryllium material, a reinforcing structure As the back rib structure of the portion 220, the number of ribs should be reduced as much as possible, and it is important to select the above-mentioned ratio between the rib interval and the rib length.

  Further, in a reflection mirror having a width (W) of 40 to 50 mm, which is the most commonly used size of the reflection mirror, and a length (L) in the swing axis direction of 40 to 60 mm, the thickness of the rear structure central shaft portion 221 is 3 to 3. 4 mm, width is 8 to 12 mm, the thickness of the base portion 210 is 0.5 mm or less, and the distance between the ribs of the back structure is the length in the longitudinal direction (B1) that divides the longitudinal direction slightly into three from the equal distance. 1.1 to 1.3 times longer than (B2, B3) (approximately A / B = 1.2 to 1.5), the thickness of the rib 222 is 1 mm or less, and the height (h) of the rib 222 is 4 mm. By setting it as the following, the reflective mirror which has the process position accuracy and the process hole shape precision substantially equivalent to the case where a beryllium mirror is used in the range of 1000-1200 Hz can be obtained.

  Next, a manufacturing method of the reflecting mirror according to the first embodiment will be described. When the reflecting surface 211 of the reflecting mirror having a thin three-dimensional structure as shown in FIG. 3 is polished by a conventional general method, the polishing rate of the rib 222 portion is increased, and the thin plate portion without the rib is subjected to the polishing pressure. On the other hand, since it escapes, the image of the finished surface is as shown in FIG. 7, and it cannot be finished to a flatness of about 1/20 of the used laser wavelength.

  Since the wavelength of the target laser here is about 9.3 microns, a flatness of about 0.47 microns or less corresponding to 1/20 of the wavelength is required. In the first embodiment, as shown in FIG. 8, a polishing jig 230 having a shape that fits into the back side of the reflecting surface by avoiding the rib structure is manufactured, and is fitted to the rib 222 on the back surface of the reflecting mirror 200. Then, an adhesive material 231 made of wax that melts at a low temperature of approximately 80 ° C. or less is poured into the fitted gap, and apparently polished as a single plate.

  When the reflecting surface was polished without using a polishing jig, the flatness was poor, such as 1 to 4 microns. On the other hand, the polishing jig 230 shown in FIG. In this case, the flatness is about 0.1 to 0.3 μm, and should be 0.465 μm or less, which is 1/20 of the wavelength 9.3 μm of the laser processing machine used for drilling the printed circuit board. did it.

Further, the surface roughness of the polished surface of the reflection mirror made of SiC manufactured as described above is finished to about 0.02 to 0.05 μm RMS, and for example, gold (Au) is vapor-deposited on the SiC polished surface, Furthermore, the reflective coating having a reflectivity of 99% or more was able to be secured with respect to the laser of the 9.3 μm wavelength band by applying an increased reflection coating for increasing the reflectivity.
When gold is deposited on the SiC reflecting surface, it is also effective to deposit gold after depositing chromium on the SiC surface in order to secure adhesion to the SiC substrate.

  The reflecting mirror of the present invention composed of the above-mentioned carbide-based ceramics is not only effective for laser light having a wavelength of about 10 microns, but also used in, for example, other optical systems that require high accuracy in a wide wavelength region. In addition, it can be used particularly favorably in a reflection optical system for light guides that constitutes an optical system by oscillating a reflection mirror at high speed, such as a laser processing machine, and can also be used widely and preferably in applications in which the reflection mirror is stationary. Needless to say. Further, as the oscillating device, not only the rotational motion as shown in FIG. 1, but also the linear motion that requires high-speed reciprocating motion and step motion where the reflecting mirror 200 is driven by a linear motor, for example, due to the high dynamic rigidity. The same effect can be expected even when used as a reflection mirror attached to a rocking device such as a motion system.

As described above, the reflecting mirror according to the first embodiment uses carbide ceramics such as silicon carbide (SiC) ceramics having a high Young's modulus that is not found in metal as a material. It is possible to suppress the deformation of the mirror, to ensure the flatness of the mirror when acceleration is generated during high-speed oscillation, and to improve the quality of the reflected light such as the roundness of the laser reflected light. As the carbide ceramics, silicon carbide (SiC) based other ceramics, the same effect also in, for example, boron carbide (B 4 _C) ceramic can be expected.

  In addition, in order to prevent deterioration of the flatness of the reflecting surface due to processing reaction force during polishing, a flatness that has been difficult in processing technology is secured by using a polishing jig for reinforcement that covers the ribs on the back surface. be able to. In addition, by using a ceramic material, it is easy to obtain, the environmental problems are cleared, and it is easy to increase the size.

Embodiment 2. FIG.
As a reflecting mirror according to Embodiment 2 of the present invention, boron carbide ceramics, for example, a composite of boron carbide (B ₄ C) and chromium boride (CrB ₂ ), boron carbide (B ₄ C) and titanium boride (TiB) ₂ ) or a composite material boron carbide ceramic material composed of a composite of boron carbide (B ₄ C) and aluminum nitride (AlN), etc. A reflection mirror (not shown) was obtained by the same method. This reflection mirror had a performance equal to or higher than that of the reflection mirror obtained by using the SiC ceramic material shown in the first embodiment.

Boron carbide (B ₄ C) has been used as a particulate material in abrasive grains and grinding tools. In addition, since the sintered body has many voids (voids), it has been used only for wear-resistant parts such as a sandblast nozzle head. Boron carbide exhibits very high performance as a wear-resistant component, but its void defects have led to a decrease in material strength. As a wear-resistant component, the original performance of boron carbide (hardness and other material properties) ) Had to eliminate void defects. As a matter of course, this vacancy defect becomes an obstacle as a mirror material. When a laser beam having a high energy density is irradiated, thermal energy absorption from the vacancy defect occurs, and heat generation and temperature rise make it impossible to use as a mirror.

The inventors have found that the tissue was observed by SEM for various materials recent boron carbide-based, composite of boron carbide _(B 4 C) and chromium boride (CrB _2), and boron carbide _(B 4 C) boride It has been found that there are composites of titanium (TiB ₂ ) or boron carbide (B ₄ C) and aluminum nitride (AlN) material-based ceramics that have a complex structure and a dense structure. As a result, the present invention has been completed as described above.

Embodiment 3 FIG.
FIG. 9 is a perspective view showing a back surface portion of a reflecting mirror according to Embodiment 3 of the present invention. The reflecting mirror 200 is made of a boron carbide ceramic such as a composite material of boron carbide (B ₄ C) and chromium boride (CrB ₂ ), or a composite material of boron carbide (B ₄ C) and titanium boride (TiB ₂ ). In particular, since these boron carbide based ceramic materials have some electrical conductivity, a part or all of the reinforcing structure portion 220 on the back surface having a curved surface shown in FIG. 9 is processed by electric discharge machining. Is.

  In the case of ceramic materials that do not have conductivity, such as SiC-based ceramics, it is necessary to preliminarily shape the reflective mirror including the reinforcing structure when firing, and the reflective surface is polished after finishing the rib structure Or, it was necessary to finish machining by cutting, but in the case of the above-mentioned boron carbide composite material, since electric discharge machining is possible, the surface of the reinforcing structure on the back side is sculpted by electric discharge machining in the state of a flat plate material, By polishing and polishing the entire surface of the base portion 210 serving as the reflective surface on the side, and then cutting out the outer shape to be the mirror by wire cutting, it was possible to obtain a highly accurate reflective mirror while maintaining the flatness. The reflecting mirror 200 made of a boron carbide composite material obtained by this method was sufficiently excellent in practical use with a flatness of the reflecting surface of 0.1 to 0.3 μm.

  The processing process of the reflecting mirror using the electric discharge machining in the third embodiment is advantageous in that the manufacturing cost is reduced because a jig for polishing is not required as compared with the case of SiC. In addition, since even an uneven surface can be processed freely with a die-sinking electric discharge machine, it becomes possible to easily obtain a target object even with a curved surface or an uneven back surface structure as shown in FIG. Since the thick part which becomes the mass is thinned and the thin rib of the back structure is made high so as to form a shell structure as a whole, a higher performance reflecting mirror can be obtained.

  As described above, according to the third embodiment, by using the composite material boron carbide ceramics having conductivity and using the electric discharge machining for the mirror manufacturing process, the rear structure central shaft portion 221 is formed. For example, it is possible to polish the reflective surface in the state of the plate material by the process of forming the reinforcing structure on the back side by electric discharge machining, even if it is a part of hollow structure such as cylindrical or square tube cross section or honeycomb structure etc. The effect that the reflective mirror which ensured the flatness of this can be obtained easily is acquired.

Embodiment 4 FIG.
Next, a method for manufacturing a reflection mirror used as a scan mirror according to Embodiment 4 of the present invention will be described. In Embodiment 1 described above, it has also been described that the processing method of the reflecting surface by polishing has a large processing reaction force, so that it is difficult to obtain the flatness of the polishing surface, but this Embodiment 4 ensures the flatness of the reflecting mirror. As a means to do this, there is provided a method of manufacturing a reflecting mirror by processing a reflecting surface using a cutting process with a small processing reaction force.

  After making the shape of the carbide-based ceramics-based reflecting mirror shown in FIG. 3, the flatness of the reflecting surface is processed to about 10 μm or less by grinding, and then the electroless nickel plating is applied to the reflecting surface by several tens to 100 μm thick film The thick film part is diamond-finished by a front lathe to obtain a mirror surface, gold plating is applied on the nickel layer, and the reflective surface obtained by applying an increased reflection coating has a flatness of about 0.1 μm. Good flatness could be obtained, and the surface roughness was as good as about 0.02 μm RMS.

  In addition, the reflection mirror of the present invention obtained by using the above plating method and diamond turning (cutting finish using a single crystal diamond tool) has a reflectivity of 99.2% or more and very good optical characteristics. It was what had. The structure of the reflective surface using diamond cutting is very convenient for obtaining a ceramic-based scanner mirror. In addition to nickel, a metal layer that can be diamond-cut is mainly composed of an aluminum deposited film, copper, gold, silver, or the above metal. A soft metal plating film such as an alloy as a component is also effective. As long as a metal thick film capable of diamond cutting can be obtained as a method of forming the metal layer on the reflecting surface, the method of film formation is not particularly limited by plating or vapor deposition.

  As described above, according to the fourth embodiment of the present invention, since the reflecting surface can be configured by cutting using a diamond tool, the carbide ceramic material that is a difficult-to-work material is polished with high accuracy. It became possible to omit the process. In addition, it is possible to provide a reflection mirror that achieves high-precision machining of the reflecting surface by cutting and has improved reflectivity.

  By the way, in the description of each of the above embodiments, for convenience, the present invention has been described with respect to the Y-axis reflection mirror 200 used as a scan mirror of a laser beam machine or a light guide optical system of the laser beam machine. Needless to say, the X-axis reflection mirror 100 can be configured in the same manner, but is not limited to a laser processing machine. Further, although the case where the reflecting mirror is a plane mirror has been described, the reflecting surface 211 or the base portion 210 does not necessarily have to be a plane. For example, a similar effect can be expected even when a reflecting mirror or a convex mirror is used.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows typically the laser beam machine by Embodiment 1 of this invention. It is a perspective view explaining the deformation | transformation mode at the time of the rocking | fluctuation motion in a general reflective mirror. It is a perspective view which shows the back surface part of the reflective mirror which used the carbide type ceramics for laser processing machines by Embodiment 1 of this invention as a base material. It is explanatory drawing which shows typically the shift | offset | difference of the drilling position by the laser processing machine using the prototyped reflective mirror, and a design drilling position. It is a characteristic view which shows the relationship of the positional deviation amount ((DELTA) p) of the processing hole with respect to the rib number of the reflective mirror measured about the reflective mirror which used the carbide type ceramics as the base material. It is a characteristic view which shows the relationship of the roundness ((DELTA) d) of the processing hole with respect to the number of ribs of the reflective mirror measured about the reflective mirror which used the carbide system ceramics as the base material. It is sectional drawing which shows typically the relationship between the rib position when the reflective surface of the reflective mirror which used the carbide-type ceramics as the base material is grind | polished, and the unevenness | corrugation of a grinding | polishing surface. It is sectional drawing explaining the usage method of the polishing jig used at the time of manufacture of the reflective mirror by Embodiment 1 of this invention. It is a perspective view which shows the back part of the reflective mirror which used as a base material the carbide type ceramics of the laser beam machine by Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser oscillator, 2 Workpiece (printed circuit board), 3 Scanner (X axis), 4 Scanner (Y axis), 5 Condensing lens (f-theta lens), 6 Laser beam (optical path), 100 Reflection mirror (X Axis), 200 reflecting mirror (Y axis), 210 base part, 211 reflecting surface, 220 reinforcing structure part, 221 rear structure central axis part, 222 rib, 205 swinging rotation axis, 206 tilting direction (primary mode), 207 Twist direction (secondary mode), 230 polishing jig, 231 adhesive, 300 design hole position, 301 processing hole.

Claims (1)

In a reflecting mirror in which a base part having a reflecting surface formed on the surface and a reinforcing structure part provided on the back surface of the base part to prevent distortion of the base part are integrally formed, the structure of the base part and the reinforcing structure part A reflecting mirror characterized in that the material is a composite of boron carbide (B ₄ C) and chromium boride (CrB ₂ ), or a composite of boron carbide (B ₄ C) and titanium boride (TiB ₂ ). a method of manufacturing a composite of boron carbide _(B 4 C) and the complex of chromium boride (CrB _2), or boron carbide _(B 4 C) and titanium boride (TiB _2), the reflection mirror And a step of optically polishing a surface to be a reflection surface opposite to the reinforcement structure portion to a required surface roughness. .

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