CN101222057A - A manufacturing process for preparing a metal flow field plate for a micro fuel cell - Google Patents

Abstract

The invention discloses a manufacturing process for preparing a metal flow field plate of a micro fuel cell, which belongs to the research on the technology of a micro fuel cell, and in particular relates to a method for manufacturing a metal flow field plate of a micro fuel cell. The manufacturing process is to make a masking layer on the surface of the metal sheet by photolithography, process a microstructure by chemical etching or electrochemical etching, and make a conductive corrosion-resistant layer on the metal surface. The materials used are metal plates, including stainless steel, titanium and its alloys, aluminum alloys, or copper and its alloys. It can process micro-holes, micro-channels, and micro-protrusion structures, and produce metal flow field plates with three-dimensional fine structures through multiple photolithography and etching processes. The flow field plate produced by this process has low resistance, corrosion resistance, wear resistance, no processing deterioration layer, no cutting residual stress, and good consistency. The minimum line width of the microstructure can reach 50 μm, combined with large-scale photolithography and etching technology, low-cost, mass production can be achieved.

Description

A manufacturing process for preparing a metal flow field plate for a micro fuel cell

technical field

The invention belongs to the research on micro-fuel cell technology, and in particular relates to a manufacturing method of a metal flow field plate of a micro-fuel cell.

Background technique

With the rapid development of electronic technology, portable electronic devices such as notebook computers, mobile phones, and MP3 players emerge in an endless stream. However, portable power supply technology has lagged far behind the development speed of microelectronics. With the progress in key materials of Micro Fuel Cell (MFC), it has attracted more and more attention as a new generation of portable power source. This type of battery generally uses a polymer membrane as a proton-conducting medium, alcohol or hydrogen as a fuel, oxygen as an oxidant, and the reaction products are water and carbon dioxide. Micro fuel cells have the advantages of high specific energy, high efficiency, convenient use, clean and environmental protection, etc., and are ideal substitutes for current lithium batteries, nickel metal hydride batteries, nickel cadmium batteries, etc.

One of the characteristics that distinguishes micro fuel cells from general fuel cells is the miniaturization of their flow field plates. The flow field plate is an important part of the fuel cell, which plays the role of distributing the flow field, collecting current, and supporting the cell structure in the fuel cell. As shown in Figure 1, fuel (such as methanol, hydrogen, etc.) and oxidant (such as oxygen, air, etc.) enter the fuel cell through the flow field on the anode flow field plate [1] and the cathode flow field plate [4] respectively; The electrons generated after the decomposition of the catalyst also need the conduction effect of the flow field plate to flow to the external load. At the same time, the flow field plate also needs to ensure the firmness of the battery structure and protect the internal membrane electrodes. The shape of the flow field in the flow field plate is generally divided into three categories: one is a hole array that penetrates up and down, as shown in Figure 2; the other is a continuous channel with an inlet [1] and an outlet [2], such as Shown in accompanying drawing 3; Also have a kind of compound that is groove and aperture, as shown in accompanying drawing 4. With the miniaturization of the flow field plate, the size of the channel in the flow field has dropped from the millimeter level to the micron level, and the original materials (such as graphite) and the original processing methods (such as milling, stamping, etc.) can no longer meet the needs , it is necessary to explore the manufacturing method of the flow field plate in terms of materials and technology.

In addition, the fuel cell system is a complex electrochemical system. As a current collector, the flow field plate needs to work in an electrolyte with an electric field, so it is extremely prone to corrosion, and surface modification treatment also needs to be considered. In order to reduce the resistance, the surface modification should not only improve the corrosion resistance of the metal but also ensure a higher electrical conductivity. Therefore, it is also necessary to modify the surface of the material for different materials and applications.

The patent application description with application number 200510086751.0 introduces a fuel cell flow field plate based on single crystal silicon microfabrication technology and sputtering collector layer method. The microfabrication of monocrystalline silicon is relatively mature at present, and microstructures with high aspect ratios can be produced. However, monocrystalline silicon is a brittle material, and sufficient packaging pressure cannot be applied. On the other hand, the collector layer sputtered on the surface of the silicon flow field plate is limited by the process, and the thickness is generally less than 1 μm. Therefore, the internal resistance of the battery is very large, and the output performance of the battery is difficult to improve, and there is still a long way to go before practical use.

Compared with the silicon flow field plate, the metal flow field plate has a small body resistivity and good toughness, and it is easy to obtain an ideal packaging effect, which is conducive to reducing the internal resistance of the battery and reducing the size of the battery. However, it is difficult to realize the processing of the micro flow field on the metal sheet by traditional processing methods.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the above-mentioned technologies, and the microfabrication method of photolithography technology and chemical etching and electrochemical etching can effectively solve this difficult problem. Through this method, not only can the micro-holes, micro-channels, micro-protrusions and other structures that are difficult to achieve in conventional processing be processed on the metal plate, but also the cutting of the workpiece can be realized to ensure the positioning between the flow field and the shape of the flow field plate Precision, and there is no processing deterioration layer and no cutting residual stress after processing.

The technical scheme adopted by the present invention is a manufacturing process for preparing a metal flow field plate of a micro fuel cell, a masking layer is made on the surface of the metal sheet by photolithography, a microstructure is processed by chemical etching or electrochemical etching, and the Make a conductive corrosion-resistant layer on the surface, the specific process steps are as follows:

1) First, blank and polish the metal sheet, soak it in an alkaline solution or an organic solvent or clean it ultrasonically, rinse it with plenty of water after cleaning, and bake it at 110°C-150°C for 30-60 minutes;

2) Then use photolithography to make a masking layer on one side or both sides. The basic steps include: spin coating or empty screen coating of about 20-60 microns of corrosion-resistant photoresist, and pre-baking at 75°C-85°C for 20-30 Minutes, using the mask exposure method, the exposure dose is 20mJ/cm ² -35mJ/cm ² , 1% Na ₂ CO ₃ solution for 30-90 seconds, rinse with deionized water, and then bake at 85°C for 10-30 minutes;

3) The required structure is processed by chemical etching or electrolytic etching. The chemical etching steps include: immersing and activating with 5%-30% concentration of hydrochloric acid or sulfuric acid for 3-10 minutes, using chemical solution spray or static etching to the desired structure. depth, rinse off the residual liquid with plenty of water;

4) Finally, remove the masking layer on the metal sheet, and make a conductive corrosion-resistant layer after polishing or grinding.

The manufacturing process of the metal flow field plate of the micro-fuel cell uses a metal plate with a thickness of 0.05-3 mm, including stainless steel, titanium and its alloys, aluminum alloy or copper and its alloys.

The manufacturing process of metal flow field plates for micro-fuel cells can process micro-holes, micro-channels, and micro-protrusion structures. Through multiple photolithography and etching processes, metal flow field plates with three-dimensional fine structures can be produced.

The manufacturing process of the metal flow field plate of the micro-fuel cell can choose electroplating, diffusion, ion implantation, sputtering or deposition to make the conductive corrosion-resistant layer according to the different materials of the flow field plate. The material of the conductive anti-corrosion layer can be gold, silver, platinum, titanium nitride, or stainless steel nitriding modified layer or conductive polymer.

The beneficial effects of the invention are: the micro-fuel cell flow field plate produced by this process has the characteristics of small resistance, corrosion resistance, wear resistance, no process deterioration layer, no cutting residual stress, good consistency and the like. The minimum line width of the microstructure can reach 50 μm, combined with large-scale photolithography-etching technology, low-cost, mass production can be achieved.

Description of drawings

Figure 1 is the schematic diagram of the fuel cell, in which: 1-anode flow field plate 2-membrane electrode three-in-one assembly 3-load 4-cathode flow field plate. Fig. 2 is a schematic diagram of the structure of a hole array micro-fuel cell flow field plate, and Fig. 3 is a structural schematic diagram of a micro-fuel cell flow field plate with continuous channels, wherein: 1-inlet 2-outlet 3-serpentine flow field. Fig. 4 is a structural schematic diagram of a micro-fuel cell flow field plate with holes and channels combined, Fig. 5 is a photo of a micro-fuel cell flow field plate with small hole arrays, and Fig. 6 is a composite micro-hole and channel flow field plate Microscope photo of the flow field.

Detailed ways

Implementation of the present invention is described in detail in conjunction with accompanying drawing:

Example 1: A self-breathing micro-fuel cell flow field plate is made from a SUS316L stainless steel plate with a thickness of 0.1 mm. The flow field is an array composed of Φ300 μm through holes, and its structure is shown in Figure 2. The specific steps are as follows: Ultrasonic cleaning and degreasing of the blanked and polished stainless steel plate with acetone and ethanol, drying at 110°C, then spin-coating 20-60 micron corrosion-resistant photoresist on one side, and pre-baking at 75°C-85°C 20-30 minutes, using the mask exposure method, the exposure dose is 20mJ/cm ² -35mJ/cm ² , 1% Na ₂ CO ₃ solution for 30-90 seconds, rinse with deionized water, and bake at 85°C for 30 minutes , Spin-coat 20-60 microns of corrosion-resistant photoresist on the other side, bake at 75°C-85°C for 20-30 minutes, use mask exposure method, double-sided pattern alignment, exposure dose is 20mJ/cm ² -35mJ /cm ² , 1% Na ₂ CO ₃ solution, developed for 30-90 seconds, rinsed with deionized water, and then baked at 85°C for 30 minutes; then activated with 17% HCl for 30 seconds, and then loaded into a double-sided spray etching machine , use stainless steel etching solution to process until the micropores are penetrated, rinse the residual liquid with deionized water on the etched stainless steel plate, and remove the photoresist by soaking in 10g/L NaOH at 80°C; nitriding treatment on the surface of the cleaned workpiece to improve the resistance corrosion.

Example 2: Using SUS304 stainless steel plate with a thickness of 0.4mm as the raw material, an active micro fuel cell flow field plate is made. The flow field channel is 300 μm wide and 100 μm deep, with a serpentine layout, as shown in Figure 3. The specific steps are as follows: Ultrasonic cleaning and degreasing of the blanked and polished stainless steel plate with acetone and ethanol, drying at 110°C, then spin-coating 20-60 micron corrosion-resistant photoresist on one side, and pre-baking at 75°C-85°C 20-30 minutes, using the mask exposure method, the exposure dose is 20mJ/cm ² -35mJ/cm ² , 1% Na ₂ CO ₃ solution for 30-90 seconds, rinse with deionized water, and bake at 85°C for 30 minutes , the back is covered with corrosion-resistant tape for protection, loaded into a spray etching machine, and processed to the required depth with stainless steel etching solution. Rinse the etched stainless steel plate with deionized water to remove the residual liquid, remove the tape on the back, then wipe the residual part with alcohol, and remove the photoresist by immersing it in 10g/L NaOH at 80°C; finally, nitriding the surface of the cleaned workpiece , to improve corrosion resistance.

Example 3: An active micro-fuel cell flow field plate is made from a copper plate with a thickness of 0.5 mm. The flow field channel is 300 μm wide and 100 μm deep in a serpentine layout, as shown in Figure 3. The specific steps are as follows: Ultrasonic cleaning and degreasing of the blanked and polished copper plate with acetone and ethanol, drying at 110°C, then spin-coating a 20-60 micron corrosion-resistant photoresist on one side, and pre-baking at 75°C-85°C for 20 -30 minutes, using the mask exposure method, the exposure dose is 20mJ/cm ² -35mJ/cm ² , 1% Na ₂ CO ₃ solution development for 30-90 seconds, rinse with deionized water, and bake at 85°C for 30 minutes, Cover and protect the back with corrosion-resistant tape, put it into a spray etching machine, and use ferric chloride solution to process to the required depth. Rinse the residual liquid on the etched copper plate with deionized water, peel off the tape on the back, then wipe the residual part with alcohol, and remove the photoresist by immersing it in 10g/L NaOH at 80°C; electroplate gold on the surface of the cleaned workpiece to improve Corrosion resistance, lower electrical resistance.

Example 4: An active micro-fuel cell flow field plate is made from a titanium plate with a thickness of 0.5 mm. The field channel is 300 μm wide and 100 μm deep in a serpentine layout, as shown in Figure 3 . The specific steps are as follows: Ultrasonic cleaning and degreasing of the blanked and polished titanium plate with acetone and ethanol, drying at 110°C, and then spin-coating a corrosion-resistant photoresist of about 20-60 microns on one side, and pre-baking at 75°C-85°C 20-30 minutes, using the mask exposure method, the exposure dose is 20mJ/cm ² -35mJ/cm ² , 1% Na ₂ CO ₃ solution for 30-90 seconds, rinse with deionized water, and bake at 85°C for 30 minutes , the back is covered with corrosion-resistant tape for protection, placed in an electrolytic etching device, and electrolytically processed to the required depth. Rinse the etched titanium plate with deionized water to remove the residual liquid, remove the adhesive tape on the back, then wipe the residual part with alcohol, and remove the photoresist by immersing it in 10g/L NaOH at 80°C; nitriding the surface of the cleaned workpiece to form Titanium nitride corrosion resistant layer.

Embodiment 5: Using SUS316L stainless steel plate with a thickness of 0.4mm as raw material to make an active micro fuel cell flow field plate, the flow field is a three-dimensional flow field mixed with small holes and channels, as shown in Figure 4, the small hole size is Φ900μm, channel width 300μm, depth 100μm. The specific steps are as follows: Ultrasonic cleaning and degreasing of the blanked and polished stainless steel plate with acetone and ethanol, drying at 110°C, then spin-coating 20-60 micron corrosion-resistant photoresist on one side, and pre-baking at 75°C-85°C 20-30 minutes, using the mask exposure method, the exposure dose is 20mJ/cm ² -35mJ/cm ² , 1% Na ₂ CO ₃ solution for 30-90 seconds, rinse with deionized water, and bake at 85°C for 30 minutes , Spin-coat 20-60 microns of corrosion-resistant photoresist on the other side, bake at 75°C-85°C for 20-30 minutes, use mask exposure method, double-sided pattern alignment, exposure dose is 20mJ/cm ² -35mJ /cm ² , developed with 1% Na ₂ CO ₃ solution for 30-90 seconds, rinsed with deionized water, and post-baked at 85°C for 30 minutes. Afterwards, the channel surface was protected with adhesive tape, and the small hole surface was activated with 17% HCl for 30 seconds, then installed in a double-sided spray etching machine, etched for 200°, the tape was removed, activated with 17% HCl for 30 seconds, and double-sided etched 100 μm to The small holes are penetrated, the etched stainless steel plate is rinsed with deionized water, and the photoresist is removed by soaking in 10g/L NaOH at 80°C; the surface of the cleaned workpiece is nitriding to improve corrosion resistance.

Claims (4)

1. the present invention relates to a kind of manufacture craft for preparing metallic flow field plate of micro fuel cell, it is characterized in that, make masking layer on the sheet metal surface by photoetching technique, method by chemical etching or chemical etching processes fine structure, and at metal surface making conduction anticorrosion layer, concrete processing step is as follows:

1) at first with sheet metal blanking, polishing, adopt alkaline solution or organic solvent to soak or ultrasonic cleaning, clean the back and wash down with big water gaging, 110 ℃-150 ℃ were dried by the fire 30-60 minute;

2) adopt photoetching process at single face or two-sided making masking layer then, basic step comprises: the anti-corrosion photoresist of the spin coating or the empty silk screen coating 20-60 micron left and right sides, baking is 20-30 minute before 75 ℃-85 ℃, adopts the mask exposure method, and exposure dose is 20mJ/cm-35mJ/cm ², 1%Na ₂CO ₃Solution development 30-90 second, after deionized water rinsing was clean, baking was 10-30 minute after 85 ℃;

3) adopt the method for chemical etching or electrolytic etching to process desired structure, the step of chemical etching comprises: adopt 5%-30% concentration hydrochloric acid or sulfuric acid to soak activation 3-10 minute, adopt chemical solution spray or static state to be etched to desired depth, wash down raffinate with a large amount of clear water;

4) remove masking layer on the sheet metal at last, polishing or polishing back make the conduction anticorrosion layer.

2. the manufacture craft that is used to prepare metallic flow field plate of micro fuel cell as claimed in claim 1 is characterized in that material therefor is the metallic plate of 0.05-3mm thickness, comprises stainless steel, titanium and alloy thereof, aluminium alloy or copper and alloy thereof.

3. the manufacture craft that is used to prepare metallic flow field plate of micro fuel cell as claimed in claim 1 or 2 is characterized in that, can process micropore, little raceway groove, micro-protuberance structure, by photoetching, etch process repeatedly, makes the metal flow field plate of three-dimensional microstructure.

4. the manufacture craft that is used to prepare metallic flow field plate of micro fuel cell as claimed in claim 3 is characterized in that, according to the difference of flow field plate material, selects to adopt plating, diffusion, ion injection, sputter or deposition process to make the conduction anticorrosion layer; The material of conduction anticorrosion layer is gold, silver, platinum, titanium nitride, or stainless steel nitriding modified layer or conducting polymer.

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