阅读说明：本技术 一种精密金属反射光栅的制造方法 (Method for manufacturing precise metal reflection grating ) 是由 魏晓蓉 朱俊涛 林树靖 张笛 王洁 于 2019-10-16 设计创作，主要内容包括：本发明涉及反射光栅的制造领域,公开了一种精密金属反射光栅的制造方法,包括以下步骤：基板研磨；基底发黑；制作光栅微结构；微电铸；脱模、超声波清洗；检测组装。本发明通过将微电铸与UV-LIGA技术、电解抛光、电镀发黑等工艺融合,制造出反射效果好、表面光洁度高、反射线条精度高、可批量化生产、成本相对较低的精密金属反射光栅。(The invention relates to the field of manufacturing of reflection gratings, and discloses a method for manufacturing a precise metal reflection grating, which comprises the following steps: grinding the substrate; blackening the substrate; manufacturing a grating microstructure; micro electroforming; demolding and ultrasonic cleaning; and (6) detecting and assembling. The invention combines the processes of micro electroforming and UV-LIGA technology, electrolytic polishing, electroplating blackening and the like to manufacture the precise metal reflection grating which has good reflection effect, high surface smoothness, high reflection line precision, batch production and relatively low cost.)

1. A method for manufacturing a precise metal reflection grating is characterized by comprising the following steps: grinding the substrate: removing surface impurities, scratches and concave-convex points of the selected planar metal substrate by electrolytic polishing, then cleaning and grinding, and placing the substrate in an oven for baking to form a ground substrate;

blackening the substrate: processing the ground substrate by adopting an electroplating blackening method to manufacture a metal blackening base;

manufacturing a grating microstructure: carrying out grating microstructure manufacturing treatment on the metal blackening base to form a developed substrate;

micro electroforming: processing the developed substrate by using micro-alloy deposition equipment to finish alloy deposition;

demolding and ultrasonic cleaning: after the substrate deposited by the alloy is demoulded by a demoulding groove, the detached metal sheet is cleaned by acetone and ultrasonic waves, and the cleaning is finished after the photoresist is observed to be completely removed under a microscope;

detecting and assembling: and (4) sequentially checking the relevant dimensional precision, the graphic accuracy, the surface finish and the metal sheet thickness of the cleaned and dried reflection grating, and then packaging the reflection grating.

2. The method of claim 1, wherein the steps of fabricating the grating microstructure and forming the developed substrate comprise:

manufacturing a chromium mask: scanning the metal blackening substrate line by adopting laser beams or electron beams; spin coating a photoresist: uniformly coating a layer of photoresist on the manufactured chrome mask plate;

pre-baking: evaporating the organic solvent in the photoresist by heating and curing the organic solvent;

exposure: adopting an ultraviolet exposure machine to make the glue film region photosensitive so as to generate photoacid;

post-baking: post-baking after exposure, and then naturally cooling to room temperature;

and (3) developing: and developing the post-baked substrate by using a developing machine.

3. The method as claimed in claim 2, wherein a spin coater is used to spin the photoresist, the spin coater is operated for 90 seconds, and the thickness of the photoresist is 0.2-5 μm.

4. The method according to claim 2, wherein the pre-baking step is performed at 85 ℃ for 1 h.

5. The method according to claim 2, wherein the exposure step uses an exposure machine operating condition that is:

the power is 100 KW;

the exposure amount was 4000C;

the UV lamp tube in the exposure machine is a high-pressure mercury lamp;

the exposure time was 20 s.

6. The method of claim 2, wherein the post-baking is performed at 85 ℃ for 2 h.

7. The method for manufacturing a precision metal reflection grating as claimed in claim 2, wherein in the developing step, the operating conditions of the developing machine are as follows:

the weight percentage of the sodium carbonate or potassium carbonate solution is 0.3-0.4%;

speed: 0.2-2.0 mm/s;

pressure: 0.2-2.0 kg;

PH of weak base solution: 7.5-9.0;

temperature: 22.0-40.0 ℃.

8. The method of claim 1, wherein the micro-electroforming step comprises the steps of:

fixing the developed substrate on a cathode copper fixture, and placing the substrate into an alloy deposition tank, wherein the substrate is immersed in an alloy deposition solution in the alloy deposition tank;

connecting a power supply, and starting the swinging equipment of the microalloy deposition equipment;

setting the current and the alloy deposition time, and finishing the alloy deposition after the micro alloy deposition equipment stops operating.

9. The method of claim 8, wherein the alloy deposition solution is a mixed solution of nickel sulfamate with sodium hypophosphite added.

10. The method according to claim 1, wherein in the step of releasing the mold and cleaning with ultrasonic waves, the solution in the cavity comprises the following components and operation setting parameters:

the weight percentage of the sodium hydroxide or potassium hydroxide solution is 1-10%;

PH：8.0─9.0；

temperature: 80 ℃;

ultrasonic frequency: 22000 HZ.

11. The method as claimed in claim 1, wherein in the step of detecting and assembling, silk floss and antistatic plastic box are used to package the product.

12. The method of any one of claims 1 to 11, wherein the metal substrate comprises a stainless steel substrate, a nickel substrate, a copper substrate and an aluminum substrate.

Technical Field

The invention relates to the field of manufacturing of reflection gratings, in particular to a manufacturing method of a precise metal reflection grating.

Background

With the rapid development of the technology and the continuous expansion of the application field, the photoelectric encoder has smaller and smaller line width and higher precision required by the grating, under the condition, the transmission type grating based on the moire fringe principle can not meet the requirement, and the reading mode of the reflection type photoelectric signal becomes mainstream. This is because: when the line width of the reticle of the transmission type grating is small (less than 15 μm), the requirements on the parallelism, the shafting end jump and the diameter adjustment of the light source are strict, the transmission type grating can only be applied in a laboratory, and the photoelectric signal can not be basically obtained when the reticle width is less than 10 um.

On the other hand, most of the common reflective gratings are glass or film reflective gratings, and the reflective gratings made of these materials cannot work under high and low temperature conditions and do not have shock resistance and aging resistance, so the high-quality gratings must be made of metal materials.

In conclusion, the high-precision metal reflection grating is more suitable for the application in the fields of high-precision reflection type encoder manufacturing, multi-axis cantilever robots, inductors and the like.

At present, there are generally four processing methods for metal reflective gratings, which are as follows:

(1) laser direct writing method. Laser direct writing is essentially a maskless lithography process, typically by direct ablation of a metal surface using a femtosecond laser. The method has the advantages of high precision and good consistency. However, the femtosecond laser is expensive and the gratings can be scribed only one by one, so that the efficiency of manufacturing large-size and large-batch gratings is low, and the laser itself is greatly lost, so that the method is mainly used in laboratory research and is rarely used in industrial production.

(2) A nanoimprint method. Nanoimprint is a technique in which a template is first fabricated, and then a template microstructure is transferred to a material to be processed with the aid of photoresist. The accuracy of the nanoimprint technology is extremely high and can reach below 5 nanometers. The template can be repeatedly used, so that the template is suitable for batch production, and when the number is large, the cost of a single product can be obviously reduced. The nanoimprint technology has significant advantages, but the admission cost of this technology is extremely high: the template is only fabricated and a complete micro-machining laboratory is needed to be built. Therefore, the technology is mainly still in the laboratory exploration stage, and the application to the industrial production needs time. Meanwhile, for the encoder and the multi-axis cantilever robot equipment, the tolerance is controlled within +/-1 um, and the nano-scale precision grating is not necessary and the cost is raised.

(3) Chemical etching method. The chemical etching method is to make a very thin transmission metal grating (the thickness can be 0.05mm when the precision requirement is high), and then to stick the transmission grating on the substrate by a special way. Since the transmission grating is thin, a reflection effect can also be formed. The chemical etching method is limited by the aspect ratio, and the grating pitch is difficult to be less than 35 μm, so that the chemical etching method is not a real reflection grating and is only used as a substitute when the precision requirement is low.

(4) UV-LIGA combines micro electroforming technology. The UV-LIGA technique is generally an ideal technique for fabricating metal high aspect ratio structures, and thus has natural advantages in metal materials. Secondly, when the metal reflection grating is manufactured, the thickness of the photoresist is reasonably controlled, and accurate metal deposition is realized by combining a micro electroforming process, so that the ideal effect required by the reflection grating can be realized.

Disclosure of Invention

The invention aims to provide a method for manufacturing a precise metal reflection grating, which is used for manufacturing the precise metal reflection grating with good reflection effect, high surface smoothness, high reflection line precision, batch production and relatively low cost by combining processes of micro electroforming with a UV-LIGA technology, electrolytic polishing, electroplating blackening and the like.

In order to achieve the above object, the present invention provides a method for manufacturing a precise metal reflective grating, which is applied to manufacture the metal reflective grating, and comprises the following steps:

grinding the substrate: removing surface impurities, scratches and concave-convex points of the selected planar metal substrate by electrolytic polishing, then cleaning and grinding, and placing the substrate in an oven for baking to form a ground substrate;

blackening the substrate: processing the ground substrate by adopting an electroplating blackening method to manufacture a metal blackening base;

manufacturing a grating microstructure: carrying out grating microstructure manufacturing treatment on the metal blackening base to form a developed substrate;

micro electroforming: processing the developed substrate by using micro-alloy deposition equipment to finish alloy deposition;

demolding and ultrasonic cleaning: after the substrate deposited by the alloy is demoulded by a demoulding groove, the detached metal sheet is cleaned by acetone and ultrasonic waves, and the cleaning is finished after the photoresist is observed to be completely removed under a microscope;

detecting and assembling: and (4) sequentially checking the relevant dimensional precision, the graphic accuracy, the surface finish and the metal sheet thickness of the cleaned and dried reflection grating, and then packaging the reflection grating.

Wherein, the step of making the grating microstructure to form the developed substrate comprises:

manufacturing a chrome mask: scanning the metal blackening substrate line by adopting laser beams or electron beams;

spin coating a photoresist: uniformly coating a layer of photoresist on the manufactured chrome mask plate;

pre-baking: evaporating the organic solvent in the photoresist by heating and curing the organic solvent;

exposure: adopting an ultraviolet exposure machine to make the glue film region photosensitive so as to generate photoacid;

post-baking: post-baking after exposure, and then naturally cooling to room temperature;

and (3) developing: and developing the post-baked substrate by using a developing machine.

Wherein the step of completing the alloy deposition by micro electroforming comprises:

fixing the developed substrate on a cathode copper fixture, placing the substrate in an alloy deposition tank, and immersing the substrate in an alloy deposition solution of the alloy deposition tank, wherein the alloy deposition solution is a nickel sulfamate solution mixed solution added with sodium hypophosphite;

connecting a power supply, and starting the swinging equipment of the microalloy deposition equipment;

setting the current and the alloy deposition time, and finishing the alloy deposition after the micro alloy deposition equipment stops operating.

Preferably, in the step of manufacturing the grating microstructure, when a photoresist is spin-coated by a spin coater, the operating condition of the spin coater is that the spin coating is carried out for 90 seconds, and the thickness of the photoresist is 0.2-5 mu m; the operation condition of the pre-drying step is pre-drying for 1h at 85 ℃; the exposure machine operating conditions adopted in the exposure step are as follows: the power is 100KW, the exposure is 4000C, a UV lamp tube in the exposure machine is a high-pressure mercury lamp, and the exposure time is 20 s; the operation condition of the post-baking is pre-baking for 2 hours at 85 ℃; in the developing step, the operating conditions of the developing machine are as follows: the weight percentage of the sodium carbonate or potassium carbonate solution is 0.3-0.4%, the speed is: 0.2-2.0 mm/s, pressure: 0.2-2.0 kg, pH of weak base solution: 7.5-9.0, temperature: 22.0-40.0 ℃.

Preferably, in the step of demoulding and ultrasonic cleaning, the solution in the demoulding groove comprises the following components and operation setting parameters: 1-10% sodium hydroxide or potassium hydroxide solution, pH 8.0-9.0, temperature: 80 ℃, ultrasonic frequency: 22000 HZ.

Preferably, in the detecting and assembling step, silk floss and antistatic plastic box packaging is adopted.

Preferably, the metal substrate includes a stainless steel substrate, a nickel substrate, a copper substrate, and an aluminum substrate.

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

1. the manufacturing raw materials adopted by the invention are metal materials, and compared with glass or film reflection gratings, the grating has the advantages of antifouling, shock resistance and high and low temperature resistance (can work under the condition of-20-85 ℃).

2. Compared with a transmission grating, the reflection grating manufactured by the invention has the obvious precision advantage that the grating distance of the transmission light is below 10um, the reflection grating can not work in principle, the grating distance of the common transmission grating is designed to be 30um to keep the working stability, and the reflection grating can work well under the condition of 10um-25 um.

3. The invention adopts electrolytic polishing and electroplating blackening technology to the metal substrate, so that the finish Ra of the substrate is less than or equal to 0.02; the UV-LIGA technology is adopted to manufacture the grating structure, so that the reflectivity of the grating reaches 95%, and the grating has an excellent reflection effect.

4. The invention combines the UV-LIGA technology and the micro-electroforming technology, and the metal reflection grating has the characteristics of high precision and good consistency.

5. The invention adopts the chemical additive manufacturing technology of micro-electroforming, the complexity of the surface of the graph does not influence the precision of the product, and compared with a nano-imprinting method and a laser direct writing method, the invention can realize rapid proofing test, is beneficial to rapid verification of the product of a designer and effective putting of the mature product on the market.

6. The silk floss and the antistatic plastic box are adopted for packaging, so that mutual extrusion in the product transportation process and scraping and abrasion in the dismounting process are effectively avoided, and the effective utilization rate of the product is improved.

Drawings

FIG. 1 is a flow chart of the process for fabricating a precision metal reflective grating according to the present invention;

fig. 2 is a schematic flow chart of the process for fabricating the grating microstructure shown in fig. 1.

The specific implementation mode is as follows:

the invention is further described with reference to the following figures and specific examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Referring to fig. 1 and 2, an overall process flow for manufacturing a precision metal reflective grating is shown, which includes the following steps:

step 1, grinding a substrate:

selecting a planar metal substrate which can be stainless steel, nickel, copper, aluminum and the like, cleaning and grinding the surface of the substrate by an electrolytic polishing method to remove surface impurities, scratches and concave-convex points, cleaning and grinding, and then placing the substrate in an oven for baking at the baking temperature of 150-180 ℃.

Step 2, blackening the substrate:

electroplating blackening method is adopted for the grinded metal substrate, and the Ra of the manufactured metal blackening base is less than or equal to 0.02, and the surface smoothness is high.

Step 3, manufacturing the grating microstructure, which comprises the following steps:

(1) manufacture of chrome mask

Manufacturing a high-precision chromium mask plate in a laser beam or electron beam progressive scanning mode;

(2) spin-on photoresist

And uniformly coating a layer of photoresist on the blackened substrate. The photoresist spinner selects an SC100 photoresist homogenizing and developing all-in-one machine, spin-coating is carried out for 90s, the selected photoresist is negative SU8 photoresist, and the thickness of the photoresist is 0.2-5 mu m;

(3) prebaking

The pre-bake is mainly to evaporate the organic solvent in the photoresist and to cure it. The operating conditions were: prebaking for 1 hour at 85 ℃;

(4) exposure method

The exposure is to make the film area needing cross-linking reaction sensitive to generate photo-acid. In the embodiment, a Germany ABM contact type mask ultraviolet exposure machine is adopted, the power of the exposure machine is 100KW, the exposure amount is 4000C, and the exposure time is 20 s;

(5) after-baking

The post-baking is to further promote the cross-linking reaction of the photoresist. After exposure, post-baking is carried out, the mixture is kept at 85 ℃ for 2h, and then the mixture is naturally cooled to room temperature;

(6) development

And developing the exposed substrate by adopting a developing machine, wherein the developing parameters are adjusted during developing: the weight percentage of the sodium carbonate or potassium carbonate solution is 0.3-0.4%, the speed: 0.2-2.0 mm/s, pressure: 0.2-2.0 kg, pH of weak base solution: 7.5-9.0, temperature: 22.0 to 40.0 ℃;

step 4, micro electroforming:

the microalloy deposition equipment consists of an alloy deposition tank, a cathode and an anode, a high-frequency direct current or pulse power supply, an alloy deposition solution, a temperature control instrument, circulating filtration equipment and swing equipment, wherein the alloy deposition solution is a mixed solution of a nickel sulfamate solution added with sodium hypophosphite.

Step 5, demolding and ultrasonic cleaning:

and (3) placing the substrate after alloy deposition is finished into a demoulding groove, taking out the substrate after demoulding is finished, picking up the metal sheet on the substrate by using tweezers, placing the metal sheet into an ultrasonic groove for cleaning, cleaning by using acetone and ultrasonic, and removing the photoresist for about 5 hours, wherein the condition that the photoresist is completely removed by observing under a microscope is qualified.

Step 6, detection and assembly:

and (4) sequentially checking the cleaned and dried reflection gratings, checking the related dimensional precision, the graphic accuracy, the surface finish and the sheet metal thickness of the complex precise graphic, and packaging the precise metal parts according to the specification after the detection meets the requirements. In order to avoid the mutual extrusion of the parts and products in the transportation process and the scraping and abrasion in the dismounting process, silk floss and antistatic plastic box packaging is adopted in the embodiment.

In this embodiment, a metal reflective grating is required to be manufactured, and the required parameters are as follows:

the length is 120 m;

the thickness is 0.1 mm;

the width is 20 mm;

the length of the reflection gold wire is 8 mm;

each gold reflection line width on the surface of the workpiece is 20 um;

reflection line and non-reflection line 1: 1, uniformly distributing;

the error is within +/-5 um.

Selecting a metal substrate with the thickness of 0.1mm, and operating according to the flow of the processing technology to manufacture the metal reflection grating with the following parameters:

the length is 120 mm;

the thickness is 0.1 mm;

the width is 20 mm;

the length of the reflection gold wire is 8 mm;

each gold reflection line width on the surface of the workpiece is 20 um;

reflection line and non-reflection line 1: 1, uniformly distributing;

the error is +/-1 mu m;

the grating flatness is 0.03 mm;

the thickness of the micro-electroformed gold is 5 mu m;

the position deviation precision is controlled to be +/-0.010 mm.

In conclusion, the manufacturing method of the precise metal reflection grating provided by the invention has the advantages of good reflection effect, high surface smoothness, high precision of reflection lines and relatively low cost.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.