A method for manufacturing a reflection grating and a reflection grating

Abstract

The present application relates to a kind of preparation method of reflective grating and reflective grating, wherein the preparation method of reflective grating includes the following steps: after cutting copper-clad plate into sheet material, the copper foil surface of the sheet material is attached with photosensitive dry film;Form grating pattern on the photosensitive dry film by laser imaging or film exposure, obtain first sheet material;The first sheet material is immersed in developing solution, and second sheet material containing the grating pattern is obtained;Chemical etching removes the excess copper foil on the second sheet material to form grating copper foil pattern and peels off residual photosensitive dry film.The preparation method of reflective grating provided by the present application can be produced by using mature printed circuit board production line, with high efficiency, low cost of raw materials, laser imaging or film exposure is used to form grating pattern, and then etching, grating stripe is high in precision and texture is clear, high-precision, low-cost and high-efficiency production of reflective grating is realized.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a method for fabricating a reflective grating and the reflective grating itself. Background Technology

[0002] With the advancement of technology, many applications require the detection of displacement and angle parameters. Traditional magnetic position sensors suffer from low resolution and are easily affected by external magnetic fields, leading to errors. Optical position sensors, however, are unaffected by external magnetic fields, effectively avoiding these drawbacks and are widely used in various electronic instruments and robotics. Optical position sensors generally consist of an encoder and a grating. Based on the method of light reception, optical position sensors can be divided into transmissive and reflective types. The corresponding gratings are also divided into transmissive and reflective gratings. Reflective optical position sensors, due to their characteristics of simultaneous light signal transmission and reception on the same side, compact structure, and high integration, are widely used in consumer electronics and robotics fields such as mobile phone autofocus modules, optical image stabilization components, foldable screen hinge angle detection devices, micro-drive motors, small gimbal mechanisms, and precision displacement detection devices.

[0003] In reflective optical position sensors, the quality of the grating fringes (including grating fringe width, reflectivity, edge sharpness, etc.) of the reflective grating plays a crucial role in the encoder's position detection accuracy. Currently, the traditional manufacturing methods in the industry mostly employ the following approaches: ① Photolithography etching on glass substrate: Periodic grating stripes are formed by sputtering and depositing metal reflective layers such as chromium and aluminum on the surface of a glass substrate, combined with direct laser imaging exposure and etching.

[0004] ② Flexible thin film laser etching: Using a flexible thin film as a substrate, an aluminum / chromium reflective layer is first deposited, and then periodic grating stripes are directly ablated by a laser.

[0005] ③ Laser engraving on metal substrates: Laser engraving is used to create an alternating reflective / absorbent grating structure on thin metal sheets such as stainless steel.

[0006] ④ Screen printing: Light-absorbing stripes are directly screen printed on the reflective film or metal reflective surface to form an alternating grating structure.

[0007] However, the methods mentioned above still cannot adequately meet the new requirements of high efficiency, high precision, and low cost in the production and manufacturing of reflective gratings. Summary of the Invention

[0008] Based on this, in order to solve at least one of the problems mentioned above, the present invention provides a method for preparing a reflective grating and a reflective grating.

[0009] In a first aspect, the present invention provides a method for fabricating a reflective grating, comprising the following steps: After the copper-clad laminate is cut into board materials, a photosensitive dry film is laminated onto the copper foil side of the board materials; A grating pattern is formed on the photosensitive dry film by laser imaging or film exposure to obtain the first substrate. The first plate is immersed in the developing solution to obtain a second plate containing the grating pattern; Chemical etching removes excess copper foil from the second substrate to form a grating copper foil pattern and peels off any remaining photosensitive dry film.

[0010] In some implementations of the first aspect, the step of cutting the copper-clad laminate into boards includes: cutting the whole copper-clad laminate into several boards, and then baking the boards to remove moisture.

[0011] In combination with the first aspect and the above implementation methods, in some implementation methods of the first aspect, the temperature of the baking and dehumidification treatment is 85~120℃.

[0012] In combination with the first aspect and the above implementation methods, in some implementation methods of the first aspect, the developing solution is an alkaline developing solution.

[0013] In combination with the first aspect and the above implementation, in some implementations of the first aspect, after the step of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the method further includes: performing gold plating or immersion gold treatment on the exposed grating copper foil on the second substrate after peeling off the residual photosensitive dry film.

[0014] In combination with the first aspect and the above implementation, in some implementations of the first aspect, after the step of chemically etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the method further includes: hot-pressing a black light-absorbing film onto the back side of the non-grating copper foil pattern area on the second substrate after peeling off the residual photosensitive dry film.

[0015] In combination with the first aspect and the above implementation, in some implementations of the first aspect, after the step of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the method further includes: attaching a reinforcing sheet to the second substrate after peeling off the residual photosensitive dry film.

[0016] In conjunction with the first aspect and the above implementations, in some implementations of the first aspect, the reinforcing sheet is a polyimide reinforcing sheet or an FR-4 reinforcing sheet.

[0017] In a second aspect, the present invention provides a reflective grating, comprising a reflective grating prepared by a method for preparing a reflective grating as described in any of the first aspects of the present invention, wherein a reinforcing sheet is further disposed on the second substrate after the residual photosensitive dry film has been peeled off.

[0018] In some implementations of the second aspect, a black light-absorbing film is adhered to the back of the non-grating copper foil pattern area on the second substrate after the residual photosensitive dry film has been peeled off. The technical solutions provided in the embodiments of the present invention bring the following beneficial technical effects: The method for fabricating reflective gratings provided by this invention can be produced using mature printed circuit board production lines, which is highly efficient and uses inexpensive raw materials. The grating pattern is formed by laser imaging or film exposure and then etched, resulting in high-precision and clear grating stripes. This method achieves high-precision, low-cost and high-efficiency production of reflective gratings.

[0019] Additional aspects and advantages of this application will be set forth in the following sections and will be understood in detail from the following description, or may be learned by specific practice of the invention. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic flowchart of a method for fabricating a reflective grating according to an embodiment of the present invention. Figure 2 This is a schematic flowchart of a method for fabricating a reflective grating according to another embodiment of the present invention. Figure 3 This is a schematic flowchart of a method for fabricating a reflective grating in another embodiment of the present invention. Figure 4 This is a schematic flowchart of a method for fabricating a reflective grating in another embodiment of the present invention. Figure 5 This is a flowchart and structural diagram of a method for fabricating a reflective grating according to an embodiment of the present invention. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0023] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] refer to Figure 1 An embodiment of the first aspect of the present invention discloses a method for fabricating a reflective grating, comprising the following steps: S100: After cutting the copper-clad laminate (CCL) into boards, a photosensitive dry film is laminated onto the copper foil side of the boards. In a specific implementation, the step of cutting the CCL into boards in S100 includes: cutting the entire CCL into several boards, and then subjecting the boards to a baking dehumidification treatment. A large-format CCL, such as a PI CCL, is cut into boards of the required production size, and these boards are then pre-treated. First, high-temperature baking removes moisture from the substrate, preventing defects such as bubbles and delamination during subsequent processing. More specifically, in some implementations, the baking dehumidification temperature is 85~120℃, determined based on the specific material of the CCL.

[0026] S200: A grating pattern is formed on a photosensitive dry film by direct laser imaging or film exposure to obtain the first substrate.

[0027] S300: Immerse the first plate in the developing solution to obtain a second plate containing a raster pattern.

[0028] S400: Chemical etching removes excess copper foil from the second substrate to form a grating copper foil pattern and peels off any remaining photosensitive dry film.

[0029] In the above preparation method, the descriptions of the first and second substrates are for ease of describing the stages of reflective grating production. In S200, Laser Direct Imaging (LDI) is a commonly used technique in PCB manufacturing, replacing traditional film contact exposure. Its core working principle is to generate laser control signals after rasterizing CAD data, driving the platform and laser beam to move in tandem to complete the exposure. This invention applies this to reflective grating manufacturers, using computer-controlled laser beams to directly image on the substrate, achieving high-precision grating pattern generation at the micron level. This technology has advantages such as reduced manual intervention and improved alignment accuracy, and is suitable for curing grating patterns on various substrates, including rigid and flexible boards. Film exposure is also a common PCB manufacturing process, using ultraviolet light to transfer patterns onto the photosensitive dry film of the board. By controlling the illumination area, a chemical reaction occurs in the photosensitive layer of the dry film, thereby accurately replicating the grating pattern on the dry film.

[0030] Because reflective optical position sensors require high clarity of grating stripe edges, blurry edges can easily generate signal noise, leading to inaccurate readings. The reflective grating fabrication method provided in this invention produces grating stripes with clear and sharp edges, avoiding these problems. Specifically, compared to laser engraving / screen printing, laser-engraved grating stripes are prone to scorching marks and burrs, while screen-printed grating stripes are prone to blurring, broken lines, and adhesion. Narrower grating stripe widths result in higher resolution for reflective optical position sensors. The fabrication method provided in this invention produces grating stripes with a maximum width of 0.02 mm, while screen printing can only achieve a maximum width of around 0.1 mm and is extremely difficult to stabilize.

[0031] After passing through S300, the first substrate with the grating pattern is immersed in the developing solution. Specifically, in one implementation, the developing solution is an alkaline developing solution. The alkaline developing solution dissolves and removes the uncured dry film, leaving only the cured dry film protective layer in the grating pattern area, thereby exposing the copper layer to be etched on the copper foil surface. Then, through chemical etching, the grating copper foil pattern is formed on the substrate. After removing the remaining photosensitive dry film from the glass, the reflective grating product is initially obtained.

[0032] The method for fabricating reflective gratings provided by this invention can be produced using mature printed circuit board production lines, which is highly efficient and uses inexpensive raw materials. The grating pattern is formed by laser imaging or film exposure and then etched, resulting in high-precision and clear grating stripes. This method achieves high-precision, low-cost and high-efficiency production of reflective gratings.

[0033] Optionally, in conjunction with the embodiments of the first aspect and the above implementation methods, in some implementation methods of the embodiments of the first aspect, such as Figure 2As shown, after the steps of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the process further includes: S500: A black light-absorbing film is hot-pressed onto the back of the non-grating copper foil pattern area on the second substrate after the residual photosensitive dry film has been peeled off.

[0034] Optionally, in conjunction with the embodiments of the first aspect and the above implementation methods, in some implementation methods of the embodiments of the first aspect, such as Figure 3 As shown, after the steps of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the process further includes: S600: A reinforcing sheet is bonded to the second substrate after the residual photosensitive dry film has been peeled off. Specifically, an FR-4 or PI reinforcing sheet is bonded to the stress area of ​​the reflective grating to improve the product's rigidity. The reinforcing sheet is either a polyimide reinforcing sheet or an FR-4 reinforcing sheet. Materials used for reinforcing reflective gratings generally need to meet properties such as high temperature resistance, acid and alkali corrosion resistance, and high temperature tolerance. The most commonly used materials in the industry are polyimide reinforcing plates, fiberglass reinforcing plates, and 303 stainless steel reinforcing plates. Polyimide reinforcing plates are abbreviated as PI. FR-4 is a flame-retardant material grade. In the circuit board industry, it often refers to epoxy fiberglass cloth laminate with a flame-retardant grade of FR-4. Its mechanical properties, dimensional stability, impact resistance, and moisture resistance are higher than those of paper-based substrates. It also has excellent electrical properties, a higher operating temperature, and its performance is less affected by the environment. As a reinforcing sheet, it can enhance the hardness of the stress area. Of course, for flexible reflective gratings, reinforcing sheets are not required.

[0035] Optionally, in conjunction with the embodiments of the first aspect and the above implementation methods, in some implementation methods of the embodiments of the first aspect, such as Figure 4 As shown, after the steps of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the process further includes: S700: The exposed copper foil of the grating on the second substrate after the residual photosensitive dry film has been peeled off is gold-plated or immersed in gold. Gold has a much higher infrared reflectivity than aluminum, tin, and chromium across the entire near-infrared to mid-infrared band, exhibiting stable and excellent reflectivity. Both gold-plated and immersed gold layers possess extremely strong chemical inertness, outstanding resistance to oxidation and salt spray corrosion, and are less prone to film failure under complex conditions such as humidity, heat, and salt spray. Long-term use shows no significant attenuation in infrared reflectivity. This invention utilizes existing mature FPC gold plating or immersion gold processes, and readily available production equipment can be used. It also features the ability to prepare a gold infrared reflective layer on the surface of a flexible substrate, enabling the fabrication of flexible reflective gratings.

[0036] Among these advantages, immersion gold plating offers a dense and uniform coating with fewer pinholes, resulting in superior resistance to salt spray and environmental stability. The thickness of the gold plating layer is controllable, and the processing efficiency is high; both are well-suited to the flexible bending characteristics of FPCs. Compared to the drawbacks of aluminum plating (easily oxidized, leading to decreased infrared reflection efficiency) and chromium plating (high hardness, brittleness, prone to cracking and peeling during bending, and inferior infrared reflection performance compared to gold), this invention achieves a comprehensive effect of high infrared reflection, high environmental reliability, and flexible deformation by preparing a gold reflective layer through gold plating or immersion gold processes. This solves the problems of insufficient stability, short lifespan, and poor mechanical compatibility of aluminum and chromium plating in flexible infrared reflective devices, expanding the application scenarios of mature gold plating and immersion gold processes for FPCs in the field of flexible infrared optical devices. Of course, tin is far less expensive than gold, and tin plating can improve the reflectivity of reflective gratings. Although it has the disadvantage of poor environmental corrosion resistance, it is still a viable surface treatment option.

[0037] To better understand the fabrication method of the reflective grating of the present invention, an embodiment will be described in detail below with reference to the accompanying drawings: like Figure 5 As shown, the complete process flow for the fabrication of a reflective grating can be summarized as follows: material preparation → baking and dehumidification → surface treatment → laminating photosensitive dry film → laser direct imaging (LDI) / film exposure → development → etching → film removal → applying cover film → reinforcement bonding → surface treatment (gold plating / immersion gold) → laser cutting / die cutting.

[0038] The specific procedures are explained below: 1. Cutting: Cut the large-format PI copper-clad laminate into the required production size.

[0039] 2. Baking for moisture removal: High-temperature baking removes moisture from the substrate, preventing bubbles and delamination during subsequent processing.

[0040] 3. Laminating photosensitive dry film: Laying photosensitive dry film onto the copper foil surface to prepare for the fabrication of the grating pattern.

[0041] 4. Laser Direct Imaging (LDI) / Film Exposure: Solidifies the grating pattern on the photosensitive dry film.

[0042] 5. Development: After exposure by LDI or film, the board is immersed in an alkaline developer to dissolve and remove the uncured photosensitive dry film, leaving only the cured dry film protective layer in the raster pattern area, thus exposing the copper layer to be etched on the copper foil surface.

[0043] 6. Etching and film removal: Chemical etching removes excess copper foil to form a grating copper foil pattern and peels off the remaining photosensitive dry film.

[0044] 7. Cover film lamination: After the residual photosensitive dry film has been peeled off, a black light-absorbing film is hot-pressed onto the back of the non-grating copper foil pattern area of ​​the board to form a light-absorbing area.

[0045] 8. Reinforcement: FR-4 or PI reinforcing sheets are attached to the stress area of ​​the sheet material forming the light-absorbing area to improve rigidity. If flexible reflective gratings are being produced, reinforcement is not required.

[0046] 9. Surface treatment: Immersion gold or gold plating is applied to the exposed copper foil of the grating to improve the reflectivity of the grating and form a reflective area.

[0047] 10. Molding and Testing: The surface-treated sheet material is die-cut or laser-cut to obtain the desired product shape, which is the reflective grating product. After completing the reflectivity test, it is shipped out.

[0048] Based on the same inventive concept, an embodiment of the second aspect of the present invention provides a reflective grating, including a reflective grating prepared by a method for preparing a reflective grating as described in any of the first aspects of the present invention, wherein a reinforcing sheet is further provided on a second substrate after the residual photosensitive dry film has been peeled off.

[0049] Furthermore, in some implementations of the second aspect, such as Figure 5 As shown, a black light-absorbing film is attached to the back of the non-grating copper foil pattern area on the second board after the residual photosensitive dry film is peeled off.

[0050] The reflective grating provided by this invention has the combined advantages of rapid mass production, low cost, and high precision.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for fabricating a reflective grating, characterized in that, Includes the following steps: After the copper-clad laminate is cut into board materials, a photosensitive dry film is laminated onto the copper foil side of the board materials; A grating pattern is formed on the photosensitive dry film by laser imaging or film exposure to obtain the first substrate. The first plate is immersed in the developing solution to obtain a second plate containing the grating pattern; Chemical etching removes excess copper foil from the second substrate to form a grating copper foil pattern and peels off any remaining photosensitive dry film.

2. The method for fabricating a reflective grating according to claim 1, characterized in that, The steps after cutting the copper-clad laminate into boards include: cutting the whole copper-clad laminate into several boards, and then baking the boards to remove moisture.

3. The method for fabricating a reflective grating according to claim 2, characterized in that, The temperature for the baking and dehumidification treatment is 85~120℃.

4. The method for fabricating a reflective grating according to claim 1, characterized in that, The developing solution used is an alkaline developing solution.

5. The method for fabricating a reflective grating according to claim 1, characterized in that, After the steps of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the method further includes: performing gold plating or immersion gold treatment on the exposed grating copper foil on the second substrate after peeling off the residual photosensitive dry film.

6. The method for fabricating a reflective grating according to claim 1, characterized in that, After the steps of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the method further includes: hot-pressing a black light-absorbing film onto the back of the non-grating copper foil pattern area on the second substrate after peeling off the residual photosensitive dry film.

7. The method for fabricating a reflective grating according to claim 1, characterized in that, After the steps of chemical etching to remove excess copper foil on the second substrate to form a grating copper foil pattern and peeling off the residual photosensitive dry film, the method further includes: attaching a reinforcing sheet to the second substrate after peeling off the residual photosensitive dry film.

8. The method for fabricating a reflective grating according to claim 7, characterized in that, The reinforcing sheet is a polyimide reinforcing sheet or an FR-4 reinforcing sheet.

9. A reflective grating, characterized in that, The reflective grating is prepared by the method described in any one of claims 1 to 5, and a reinforcing sheet is further provided on the second substrate after the residual photosensitive dry film is peeled off.

10. The reflective grating according to claim 9, characterized in that, A black light-absorbing film is attached to the back of the area of ​​the non-grating copper foil pattern on the second board after the residual photosensitive dry film is peeled off.

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