CN111573614A

CN111573614A - High-resonant-frequency large-aperture galvanometer and preparation method thereof

Info

Publication number: CN111573614A
Application number: CN202010466898.7A
Authority: CN
Inventors: 左辉; 贺思源
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-05-28
Filing date: 2020-05-28
Publication date: 2020-08-25
Anticipated expiration: 2040-05-28
Also published as: CN111573614B

Abstract

The invention discloses a high-resonant-frequency large-aperture galvanometer and a preparation method thereof, wherein the preparation method comprises the following steps: the FPCB comprises an FPCB, a silicon layer adhered to the front surface of the FPCB and external magnets arranged at two sides of the FPCB; the FPCB comprises a middle seat, a polyimide torsion beam and an external polyimide reinforcing frame, wherein the front side and the back side of the middle seat are provided with copper coils; the preparation method comprises the following steps: attaching the silicon wafer to a carrier wafer with the metal plating layer side facing down; sticking the FPCB with the front side facing downwards on the non-metal plating layer side of the silicon wafer; and etching the silicon wafer in one step by using the FPCB as a mask and the metal coating as a stop layer to obtain the high-resonant-frequency large-aperture galvanometer. The simple manufacturing process and the 0.1mm resolution FPCB lithography of the present invention result in very low cost of several dollars; the copper coil embedded in the FPCB structure generates a large driving force at the back of the large aperture mirror plate, and a relatively high resonance frequency is obtained in consideration of the large aperture and the high thickness.

Description

High-resonant-frequency large-aperture galvanometer and preparation method thereof

Technical Field

The invention relates to the technical field of galvanometers, in particular to a high-resonant-frequency large-aperture galvanometer and a preparation method thereof.

Background

Many micro-electro-mechanical systems (MEMS) devices have been successfully developed, such as micro-accelerometers, micro-pressure sensors, microphones, and Digital Micromirror Devices (DMDs); due to its small size, high performance and low cost. MEMS fabrication is a micron-resolution lithography process that involves the steps of creating a photomask, mask alignment, deposition and etching, which is both complex and expensive. But low unit cost can be achieved by mass production, i.e. hundreds or thousands of devices are manufactured simultaneously by performing the same series of processing steps on the same silicon wafer. MEMS micromirrors typically have apertures of 10s μm to 1mm for lower unit cost. When the pore size becomes large, e.g. >10mm, the low unit cost advantage disappears since the unit cost is inversely proportional to the square of the pore size. Another limiting factor of the MEMS micro-mirror having a large aperture is that the mirror thickness is thin (1 s-10 s μm), which deteriorates the surface flatness of the large aperture mirror. An outer thick mirror plate can be bonded over the released MEMS actuator to obtain a large aperture micromirror with good flatness. However, it is very challenging to bond the lens to the fragile MEMS actuator, which results in high cost.

Large aperture galvanometers have gained increased attention in scanning LiDAR applications in recent years, primarily for the autonomous automobile market. MEMS galvanometers may replace conventional rotating motor based scanning mechanisms in LiDAR, thereby achieving higher scanning frequencies, lighter, more compact structures, higher reliability, and significantly lower cost. Recently some large aperture MEMS galvanometers (aperture 3-5 mm) have been used in LiDAR, showing promising results. Scanning LiDAR requires very large aperture galvanometers, e.g., >10mm, because: 1) in-line LiDAR, a larger aperture mirror can withstand higher power lasers and collect more diffuse reflected light power, resulting in higher power signal-to-noise ratio (SNR) and longer measurement distances; 2) in dual-axis LiDAR, a large aperture mirror is required to cover the transmit and receive lenses. The largest MEMS mirror aperture pitch used to date in commercial LiDAR development was 10X 10mm of Blickfeld, the detailed design of which was not disclosed.

Mirrocle Technologies Inc. shows that some large aperture MEMS micromirrors are expanded in size to 6.4mm or even 7.5mm in diameter by bonding individual mirrors on released microactuators, which results in high cost, furthermore the mechanical rotation angle is reduced to + -2.5 and + -1.0, respectively, an electro-thermal MEMS micromirror for free-space optical communication, up to 10mm × 10mm aperture size and 10 optical scan angle, both MEMS mirrors have larger aperture size but limited rotation angle²Aperture size and an optical scanning range of 60 deg.. But all 14 micromirrors must be synchronized to have the same phase and amplitude.

Flexible Printed Circuit Board (FPCB) micromirror technology can be used to manufacture low cost and large aperture galvanometers, and has been used for single-line scanning LiDAR for low speed Automated Guided Vehicles (AGV). However, the FPCB galvanometers cannot achieve higher frequencies, such as 200Hz to 1kHz, which is necessary for LiDAR used in high speed and high vibration environments (e.g., road vehicles) to have vibration resistance and to obtain more scanlines in the 3D LiDAR of an autonomous vehicle. An electromagnetic galvanometer based on a flame retardant material (FR4) PCB uses FR4 material as a substrate of a low-cost large-aperture mirror. It is also a soft material with a low young's modulus of about 20Mpa and is therefore not suitable for use in high resonant frequency mirrors.

The document "L.Ye, G.Zhang, and Z.you," Large-aperture kHz operating frequency-based optical micro-scanning mirror for laser Application, "Micromachines, vol.8, No.4,2017, doi:10.3390/mi 8040120" proposes a Large-aperture galvanometer using a titanium alloy as a substrate and an additional bonded coil and SiO₂A lens. Since the density of the Ti alloy material is twice that of silicon, and the Young's modulus is 30% lower, 3 to 4 times of current is needed to generate large Lorentz force to reach the same frequency and rotation angle as the silicon-based mirror. In addition, the design of (a) is more expensive because it must be manufactured one by one using an electric discharge manufacturing method.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a high-resonant-frequency large-aperture galvanometer and a preparation method thereof.

The invention discloses a high-resonant-frequency large-aperture galvanometer, which comprises: the FPCB comprises an FPCB, a silicon layer adhered to the front surface of the FPCB and external magnets arranged at two sides of the FPCB;

the FPCB includes middle seat and outside polyimide rib, middle seat passes through the polyimide torsion beam with the polyimide rib and links to each other, the front and the back of middle seat are equipped with top layer copper coil and bottom layer copper coil.

As a further improvement of the invention, the middle seat, the polyimide reinforcing frame and the polyimide torsion beam are of an integrated flexible structure, and the flexible structure consists of a polyimide reinforcing layer and a polyimide base layer which are adhered up and down.

As a further improvement of the invention, a polyimide covering layer is arranged outside the top layer copper coil or the bottom layer copper coil.

As a further improvement of the invention, the thickness of the silicon layer is 50-200 μm, one side of the silicon layer is adhered to the FPCB, and the other side of the silicon layer is provided with a metal coating.

As a further improvement of the invention, the copper coil of the FPCB is electrified to generate Lorentz force for driving the vibrating mirror to vibrate under the action of the external magnet magnetic field.

The invention also discloses a preparation method of the high-resonant-frequency large-aperture galvanometer, which comprises the following steps:

a metal coating is arranged on the front surface of the silicon wafer;

attaching the silicon wafer to a carrier wafer with the metal plating layer side facing down;

sticking the FPCB with the front side facing downwards on the non-metal plating layer side of the silicon wafer;

and etching the silicon wafer in one step by using the FPCB as a mask and the metal coating as a stop layer to obtain the high-resonant-frequency large-aperture galvanometer.

As a further improvement of the invention, the thickness of the carrier wafer is 500 μm, and the adhesive oil is arranged between the silicon wafer and the carrier wafer.

As a further improvement of the invention, the etching method is DRIE etching.

Compared with the prior art, the invention has the beneficial effects that:

the present invention attaches the FPCB structure to the thin silicon wafer having the metal plating film, and etches the silicon wafer by one step using the FPCB structure as a mask and the metal plating film as a stop layer. The simple fabrication process and FPCB lithography with 0.1mm (rather than <1 μm required for micro-fabrication) resolution results in very low cost, which is a few dollars. Copper coils embedded in the FPCB structure on the back of the large aperture mirror plate, rather than mounted beside the mirror plate as in MEMS galvanometers, produce a large driving force, allowing for a relatively high resonant frequency in view of the large aperture and high thickness.

Drawings

FIG. 1 is a schematic structural diagram of a high-resonant-frequency large-aperture galvanometer according to an embodiment of the present invention;

FIG. 2 is an exploded view of a high resonant frequency large aperture galvanometer according to one embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a front structure of a high-resonant-frequency large-aperture galvanometer according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a reverse structure of a high-resonant-frequency large-aperture galvanometer according to an embodiment of the present invention;

FIG. 5 is a flow chart of a method for manufacturing a high resonant frequency large aperture galvanometer according to one embodiment of the present invention;

fig. 6 is a diagram of a simulation result of the resonant modes of Mirror _ a and Mirror _ B according to an embodiment of the present invention;

in the figure:

10. FPCB; 11. a polyimide reinforcing layer; 12. a top layer copper coil; 13. a polyimide base layer; 14. a bottom layer copper coil; 15. a double-sided adhesive layer; 16. a middle seat; 17. a polyimide torsion beam; 20. a silicon layer; 21. a silicon mirror surface; 30. a silicon wafer; 40. carrying a wafer; 50. an external magnet.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention is described in further detail below with reference to the attached drawing figures:

as shown in fig. 1 to 4, the present invention provides a high-aperture galvanometer with high resonant frequency, including: an FPCB10, a silicon layer 20 attached on a front surface of the FPCB10, and external magnets 50 disposed at both sides of the FPCB 10; wherein,

as shown in fig. 3 and 4, the FPCB10 of the present invention includes a middle base 16 and an outer polyimide stiffener frame in a horizontal plane, the middle base 16 is connected to the polyimide stiffener frame by a polyimide torsion beam 17, and the front and back surfaces of the middle base 16 are provided with a top copper coil 12 and a bottom copper coil 14. Furthermore, the middle seat 16, the polyimide reinforcing frame and the polyimide torsion beam 17 are of an integrated flexible structure.

As shown in fig. 2, the FPCB10 of the present invention includes a polyimide reinforcing layer 11 and a polyimide base layer 13 in a vertical direction, where the polyimide reinforcing layer 11 and the polyimide base layer 13 have the same structure, and include three parts, namely a middle seat, a polyimide reinforcing frame, and a polyimide torsion beam; the polyimide reinforcing layer 11 and the polyimide base layer 13 are adhered through a double-sided adhesive layer 15; the front and back sides of the middle seat 16 are embedded in the top layer copper coil 12 and the bottom layer copper coil 14, and at least two copper layers are required to form a loop of the current path. The number of copper coil layers may be up to 8, where only two copper coil layers are used. The mounting holes are additionally formed in the support, and the support is only used in multiple installations for conveniently carrying out experimental tests. The dimensional tolerance of the laser cut FPCB profile is ± 25 μm, which results in a fabrication error of the torsion beam width of 50 μm. This results in a change of about 3.2% in the resonant frequency of the torsion beam having a width of 0.8 mm. The FPCB structure is fabricated using standard commercial FPCB processes.

The present invention has a polyimide coating, not shown, outside the top layer copper coil 12 or the bottom layer copper coil 14.

The thickness of the silicon layer 20 is 50-200 μm, preferably 100 μm; one side of the silicon layer is adhered to the FPCB10, and the other side is provided with a metal plating layer, i.e., the silicon mirror 21, and the thickness of the metal plating layer may be 100 nm.

The present invention can simply etch a thin (e.g., 50-200 μm) silicon wafer, one side of which has an FPCB structure as an etching mask and the other side of which has a metal film as an etching stop layer and a reflective surface. Meanwhile, the multi-turn copper coil embedded in the FPCB structure generates a Lorentz force when current passes through the coil and is combined with two magnets to be positioned beside the mirror plate to generate a magnetic field, and the mirror plate is vibrated. Since the flexural material of the galvanometer is silicon having a Young's modulus of 150GPa, a higher frequency can be obtained than that of an FPCB galvanometer in which polyimide having a Young's modulus of 2.5 to 4GPa is a flexural material. Since the thickness of the silicon wafer can be 50 to 200 μm, a good flatness can be obtained, for example, a radius of curvature (ROC) >10 m. In addition, the mirror does not use expensive photoetching process based on micrometer resolution, but uses photoetching process based on 0.1 millimeter resolution to manufacture FPCB structure, so the cost is very low. For example, a two-layer FPCB used to make a 12x12mm mirror requires only 10 cents. Considering the cost of DRIE for magnets and 6 inch silicon wafers, 34 pieces of 12X12mm mirrors can be etched per wafer, with a number greater than 1,000, at a cost of $ 2 to $ 3 per mirror.

As shown in fig. 5, the present invention provides a method for preparing a large aperture galvanometer with high resonant frequency, comprising:

step 1, selecting FPCB10 and a silicon wafer 20 provided with a metal coating;

wherein,

starting from an FPCB structure and a 100 μm thin silicon mirror wafer coated with a metal (e.g. aluminum); the thickness of the silicon wafer is not limited by the manufacturing process, and may be 50-200 μm according to practical design. The FPCB structure is composed of a middle pedestal which determines the aperture size of the mirror plate (e.g., 12x12mm or 24x24 mm), two torsion beams (e.g., 0.8mm wide and 3mm long per each) and a polyimide reinforced frame. The middle seat and the torsion beam are made of multi-layer polyimide and are embedded with copper coils. A transparent polyimide cover layer covers the copper coil.

Step 2, the metal coating side of the silicon wafer 20 faces downwards and is attached to a bearing wafer; sticking the FPCB with the front side facing downwards on the non-metal plating layer side of the silicon wafer;

wherein,

the silicon wafer 20 was turned upside down and attached to a 500 μm thick carrier wafer by a layer of oil; then, bonding the FPCB structure on the back surface (the surface without the metal coating) of the silicon mirror wafer;

the carrier wafer has the following functions: 1) as a substrate when etching is performed through the silicon mirror wafer; 2) a protective metal coating; 3) damage to the thin silicon wafer is avoided when manually bonding the FPCB structure and moving between different devices.

Step 3, etching the silicon wafer in one step by taking the FPCB as a mask and the metal coating as a stop layer to obtain a high-resonant-frequency large-aperture galvanometer;

wherein,

a one-step DRIE etch is performed using the DRIE system using the FPCB structure as an etch mask and the coated metal layer as an etch stop. After DRIE treatment, the metal film is exposed no matter where the FPCB structure is not covered; the mirrors were released from the carrier silicon wafer using isopropyl alcohol (IPA).

As shown in fig. 1, the galvanometer of the present invention is driven by lorentz forces generated by current flowing through a copper coil embedded in polyimide below the galvanometer face, the coil being in the magnetic field generated by two external magnets. The mirror is fabricated in only one etching step without the need for lithographic techniques based on MEMS μm resolution. The FPCB structure is fabricated using only lithography based on 0.1mm resolution, which is standard and commercially available at very low cost. For example, a mirror with an aperture of 12x12mm uses a two-layer FPCB structure with an overall size of 22mmx16mm, which costs only 5 cents for a 100K number. The total cost of the mirror is mainly from the step etching and silicon wafer, plus two external magnets, with a mass production estimated to require $ 2 to $ 3. However, the price of a conventional MEMS mirror with a diameter of 7mm is $ 100, let alone that it is very challenging to manufacture a MEMS mirror with an aperture >10mm or >20mm using this technique.

Thus, the FPCB masked one-step etched mirror technique provides a simple and low cost method for fabricating large aperture galvanometers. In addition, it can generate enough Lorentz force to drive the large aperture galvanometer, which needs high rigidity to realize high frequency due to large inertia, and the copper coil is installed on the back of the mirror surface instead of the side of the mirror plate like the MEMS magnetic mirror. Since the mirror is large, a large number of coils can be accommodated to generate a large lorentz force, and even due to the limited resolution determined by the FPCB process, the width of the coils is large, e.g., 0.1 mm. This dictates that the novel galvanometer technique is only suitable for large aperture galvanometers (e.g., >10mm) and is a good complement to conventional MEMS micro-mirror techniques, which are more suitable for small aperture micro-mirrors (e.g., μm to several millimeters).

The invention provides two modeling and prototype designs for designing Mirror _ A and Mirror _ B to verify a novel galvanometer processing technology. The application of the novel galvanometer technology in LiDAR is demonstrated and tested. The performance achieved is: mirror _ a, aperture 12x12mm, oscillation frequency 510Hz, field of view (FOV) 30 °, radius of curvature (ROC) 10 m; the Mirror _ B aperture was 24x24mm, the oscillation frequency was 160Hz, the FOV was 20 °, and the ROC was 10 m.

Specifically, the method comprises the following steps:

A. prototype size

The present invention developed two prototypes, namely Mirror _ a and Mirror _ B. The only difference between them is the aperture size and the turning beam size, as shown in table I. Both galvanometers are manufactured by the same FPCB manufacturing and FPCB mask one-step etching process. The aperture size of Mirror _ a is 24x24mm, which is smaller (12x12mm), higher resonant frequency and larger rotation angle than Mirror _ B. The thickness of the silicon layers of the two galvanometers is 100 μm. The thicknesses of all layers of the FPCB structure can be found in table II. A 12um thick copper layer is made of 1/3oz copper, which is the thinnest copper that is widely available without additional cost.

TABLE I sizes Mirror _ A and Mirror _ B

Table II:

the model is simplified in the simulation as follows: all the polyimides, the cover layer and the adhesive layer were combined to one polyimide layer 80 μm thick. This is because the cover layer is also a polyimide material and is bonded on top of the copper layer with an acrylic or epoxy adhesive. The two copper coil layers below the mirror are combined into a 12 μm thick solid planar film equal to the total mass of the copper coils, since the coils occupy only half the area, with a width of 0.1mm and a gap of 0.1 mm. The following material properties were used in the simulation: the copper density is 8300Kg/m3, the Young modulus is 110GPa, and the Poisson ratio is 0.34; polyimide-density 1420Kg/m³Young's modulus 2.5GPa, Poisson's ratio 0.34; the silicon density is 2330Kg/m³Young's modulus was 169GPa, and Poisson's ratio was 0.28.

B. Resonant frequency

The resonance modes of Mirror _ a and Mirror _ B were simulated using ANSYS, and the results are shown in fig. 6. The first order mode vibration of Mirror _ a is rotation around the torsion beam with a frequency of 598Hz, as shown in a of fig. 6; the second order mode oscillation is a planar up-down translation with frequency 1118Hz, as shown in b in fig. 6; the third order mode oscillation is the rotation of the vertical torsion beam with a frequency of 2810Hz, as shown in c in fig. 6. The first order mode vibration of Mirror _ B is a rotation around the torsion beam with a frequency of 193.8Hz, as shown by d in fig. 6; second order mode oscillation is a planar up-down translation with frequency 505Hz, as shown by e in fig. 6; the frequency of the third order mode is 2810Hz, as shown by f in FIG. 6.

C. Maximum stress

The maximum stress in Mirror _ a and Mirror _ B was simulated. For Mirror _ a, when the maximum mechanical angle in one direction is 7.5 °, this results in a total optical rotation angle of 30 °, with the maximum stress on the silicon beam, i.e. 447MPa, being below 500-700MPa (fracture strength of 100 μm thick silicon wafer). For mirrorb, the maximum total optical rotation angle can reach 20 °, while the maximum stress on silicon is 389.5 MPa. Meanwhile, the maximum stress on the polyimide and the copper of the Mirror _ A is 20MPa and 95MPa respectively, and the maximum stress on the Mirror _ B is 15MPa and 95MPa respectively. They are much less than the yield stress of 60MPa for polyimide and 206MPa for thin film copper. The maximum rotation angle of the one-step etching galvanometer of the FPCB mask can be increased by optimizing parameters of the galvanometer (e.g., thickness of the silicon wafer, width and length of the rotating beam).

The stress of the galvanometer at 50g acceleration is also simulated by using ANSYS to verify that the galvanometer meets the requirements of the automobile use impact test. 50g of acceleration was applied in all three directions in the simulation, and the maximum stresses of Mirror _ A and Mirror _ B were 22.8MPa and 64.6MPa, respectively, which were much smaller than the breaking strength of the silicon wafer.

D. Influence of surface deformation of large-aperture mirror

One major application of the galvanometer proposed by the present invention is for scanning LiDAR, for example, integrating galvanometers with single-point LiDAR to construct 2D (single line) scanning LiDAR. The galvanometer oscillates to scan the emitted infrared laser light (emanating from the single point LiDAR) while collecting and reflecting the scattered reflected light back to the receiving lens of the single point LiDAR.

2D LiDAR may be further developed as 3D (multiline) LiDAR by adding a galvanometer "T.Tai, H.Zuo, and S.He," 3D LIDAR Based on FPCBMirror, "limited for publication, 2020". In 3D LiDAR, the galvanometer of the FPCB mask is scanned vertically (fast axis) and horizontally (slow axis) to obtain a 3D map. The mirror is a lorentz force based FPCB mirror with polyimide as the torsion beam, so it can rotate at a large angle under the action of low frequency drive signals.

One key issue with large aperture galvanometers is the effect of specular distortion (static and dynamic distortion or flatness) on the performance of scanning LiDAR. The static deformation is mainly caused by the metal film coating on silicon, and the dynamic deformation is caused by high acceleration induced inertial force when vibrating. The following simulation was performed to examine the influence of mirror surface deformation.

Step 1) A scanning LiDAR optical system was built in Zemax that included a laser beam, a one-step etched Mirror (Mirror A or Mirror B) for the FPCB mask, a receiving lens and object surface, and a universal biaxial LiDAR with the parameters as follows.

Laser: the size of the laser beam of the Mirror _ A is 2mmx2mm, the size of the laser beam of the Mirror _ B is 5mmx5mm, the divergence angle is 0.3 degrees, the peak power is 20W, and the wavelength is 905 nm;

a receiving lens:

Mirror_A，

Mirror_B；

photoelectric sensor with light sensing window area 1mmx1 mm;

the distance (D) from the surface of the object to the photoelectric sensor is 30-200 m.

And 2) using a perfect mirror with the surface deformation of 0 as a scanning mirror. When the object distance (D) is 150m and the reflectivity is 90%, the light power received by the simulated photoelectric sensor is 104 μ W.

Step 3) replace the perfect Mirror with Mirror _ A, whose static and dynamic deformations are superimposed. The static deformation is bowl-shaped, and the dynamic deformation is sine-shaped on the oscillation axis and can be calculated according to a formula. A static deformation of 1.8 μm and a dynamic deformation of 2.435 μm were used.

The light power received by the photosensor at each object distance (D) was simulated until the received light power equals 104 μ W when D is 135 m.

The above steps 2) and 3) were repeated, the object distance D was 50m, and the reflectance was 10%. When a perfect mirror is used, the received optical power is 103 μ W. When the object distance is adjusted to 46m using the Mirror _ a, the received power reaches 103 μ W.

Similar simulations were performed for mirrorb. The results are shown in tables III-IV.

Verifying the simulation result:

1) if a LiDAR system with an ideal Mirror (0 surface deformation) can measure a distance of 150m and an object surface reflectivity of 90%, a LiDAR system that replaces the same ideal Mirror with Mirror _ A can measure 135m due to its surface deformation.

2) If a LiDAR system with an ideal Mirror (0 surface deformation) can measure a distance of 50m and an object surface reflectivity of 10%, then the same LiDAR with a Miror _ A replacing the same ideal Mirror can measure 46m due to its surface deformation.

3) If a LiDAR system with a perfect Mirror (0 surface deformation) can measure a distance of 180m and an object surface reflectivity of 90%, a LiDAR system that replaces the same Mirror with a Mirror _ B can measure 144m due to its surface deformation.

4) If a LiDAR system with a perfect Mirror surface (0 surface deformation) can measure a distance of 70m and an object surface reflectivity of 10%, then the same LiDAR with a Mirror _ B replacing the same Mirror surface can measure 58m due to its surface deformation.

In summary, the surface deformation measurement distance of Mirror _ a was reduced by-10%, i.e., 90% for 135/150 and 92% for 46/50. The surface deformation measurement distance of Mirror _ B was reduced by about 20%, i.e., 80% for 144/180 and 82.8% for 58/70.

Table III: measuring distance Mirror _ A

TABLE IV measurement of distance Mirror _ B

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A high resonant frequency large aperture galvanometer, comprising: the FPCB comprises an FPCB, a silicon layer adhered to the front surface of the FPCB and external magnets arranged at two sides of the FPCB;

2. The large aperture galvanometer of claim 1, wherein the intermediate mount, the polyimide reinforcing frame and the polyimide torsion beam are of an integrated flexible structure, and the flexible structure is composed of a polyimide reinforcing layer and a polyimide base layer which are adhered up and down.

3. The large aperture galvanometer of claim 2, wherein a polyimide coating is disposed over the top or bottom copper coils.

4. The large aperture galvanometer of claim 1, wherein the silicon layer has a thickness of 50-200 μm, and one side of the silicon layer is bonded to the FPCB and the other side is provided with a metal plating layer.

5. The large aperture galvanometer of claim 1, wherein the copper coil of the FPCB is energized to produce a lorentz force that drives the galvanometer to vibrate under the influence of the external magnetic field of the magnet.

6. A method for preparing a high-resonant-frequency large-aperture galvanometer according to any one of claims 1 to 5, comprising:

a metal coating is arranged on the front surface of the silicon wafer;

7. The method according to claim 6, wherein the carrier wafer has a thickness of 500 μm, and an adhesive oil is provided between the silicon wafer and the carrier wafer.

8. The method of claim 6, wherein the etching method is DRIE etching.