Abstract:
This invention is to introduce a manufacturing method of fuel cell with integration of catalytic layer and micro sensors, which comprises following steps: manufacturing multi-hole silicon layer step, generating catalytic layer step, forming insulation layer step, integrating micro sensors step, and finalizing step. With the function of gas-diffusion layer in the multi-hole silicon wafer and multiple catalytic grains evenly spread over the inner walls of flow-way holes of the silicon wafer, a great catalytic layer can be formed effectively. Further, micro sensors properly are integrated. This invention&#39;s merits include simple structure and capabilities of simultaneously detecting temperature and humidity. Plus, it can heat up internally for a fuel cell.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a manufacturing method of fuel cell with integration of catalytic layer and micro sensors. Particularly, this invention relates to a manufacturing method of fuel cell to integrate micro temperature sensors, micro humidity sensors, gas-diffusion layer, catalytic layer, and flow field plates together. The structure is simple after integration. It can detect temperature and humidity simultaneously. And, it can also generate heats internally inside the fuel cell. 
         [0003]    2. Description of the Prior Art 
         [0004]    The temperature and humidity of the electrolyte membrane inside a fuel cell will influence the performance of a fuel cell. If the humidity is too high, too low, or the temperature is too high, it will cause the overall performance down. Thus, it is a very important issue to monitor the internal humidity and temperature of fuel cells. 
         [0005]    Current structure design of fuel cells makes it difficult or impossible to integrate micro sensors, gas-diffusion layer, catalytic layer, and flow field plates (or called bi-polar plates) together. Thus, it causes significant hassles no matter in manufacturing, measuring, or calibrating. Besides, the manufacturing costs are high, and the fuel cell&#39;s volume is hard to be decreased. 
         [0006]    Next, if micro sensors are disposed (or embedded) in the flow ways of fuel cells, it is very difficult to lay out their connecting lines (or wires). And, its original flow field will be disturbed without doubt. Moreover, due to the short circuit problem easily caused by high humidity, the micro sensors cannot precisely detect the condition in the wet flow ways. Furthermore, unless both the micro temperature sensors and micro humidity sensors are disposed inside the fuel cell, the temperature and humidity cannot be detect simultaneously. 
         [0007]    Thus, a new manufacturing technique is needed to solve aforementioned problems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The primary object of the invention is to provide a manufacturing method of fuel cell with integration of catalytic layer and micro sensors. Its structure is simple after integration. 
         [0009]    The next object of the invention is to provide a manufacturing method of fuel cell with integration of catalytic layer and micro sensors. In which, it can detect temperature and humidity simultaneously. 
         [0010]    Another object of the invention is to provide a manufacturing method of fuel cell with integration of catalytic layer and micro sensors. It not only can detect temperature but also can heat up the fuel cell internally. 
         [0011]    In order to achieve the above-mentioned object, a technical solution is provided. A manufacturing method of fuel cell with integration of catalytic layer and micro sensors comprises following steps: 
         [0012]    [a] manufacturing multi-hole silicon layer step: preparing a plain, no-hole silicon wafer that has two main surfaces: a first surface and a second surface; a designated etching solution being employed on the first surface to make multiple flow ways and then further by photolithographic techniques, making a plurality associated holes on the second surface, forming a multi-hole silicon layer functional as gas-diffusion layer; 
         [0013]    [b] generating catalytic layer step: preparing multiple catalytic grains, and then spreading them evenly on inner walls of the associated holes of the multi-hole silicon layer, enabling it work as a catalytic layer; 
         [0014]    [c] forming insulation layer step: an insulation layer being formed on the second surface; 
         [0015]    [d] integrating micro sensors step: attaching a micro sensor layer, which comprises at least one micro temperature or humidity sensor, on the insulation layer; and 
         [0016]    [e] finalizing step: making a fuel cell with integrations of micro sensor layer, gas-diffusion layer, catalytic layer, and flow field plates. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  shows the manufacturing flow chart of the invention. 
           [0018]      FIG. 2  is a partially enlarged perspective view of the multi-hole silicon layer. 
           [0019]      FIG. 3  is a partial sectional view of  FIG. 2 . 
           [0020]      FIG. 4  shows the first half manufacturing processing processes of the invention. 
           [0021]      FIG. 5  shows the second half manufacturing processing processes of the invention. 
           [0022]      FIG. 6  is a partial sectional view of the finished product. 
           [0023]      FIG. 7  is a view illustrating the micro temperature sensor. 
           [0024]      FIG. 8  is a view illustrating the micro humidity sensor. 
           [0025]      FIG. 9  illustrates a structure with the micro sensors separated horizontally. 
           [0026]      FIG. 10  illustrates another structure with micro sensors separated vertically. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    First, referring to the  FIGS. 1 ,  2  and  3 , this invention is a manufacturing method of fuel cell with integration of catalytic layer and micro sensors. It comprises the following steps: 
         [0028]    1. Manufacturing multi-hole silicon layer step  11 ; 
         [0029]    2. Generating catalytic layer step  12 ; 
         [0030]    3. Forming insulation layer step  13 ; 
         [0031]    4. Integrating micro sensors step  14 ; and 
         [0032]    5. Finalizing step  15 . 
         [0033]    About the details of all these steps mentioned above, they are described as follows: 
         [0034]    In the Step  1  of “Manufacturing multi-hole silicon layer step  11 ”: First, prepare a plain, no-hole silicon wafer (as shown in  FIG. 4 ) that has two main surfaces: a first surface  20 A and a second surface  20 B. A designated etching solution is employed on the first surface  20 A to make multiple flow ways  21  and then further, by photolithographic techniques, to make their associated holes  22  on the second surface  20 B, forming a multi-hole silicon layer  20 . The flow ways  21  are connected to their associated holes  22  to enable it functional as gas-diffusion layer. 
         [0035]    In real practice of Step  1  “Manufacturing multi-hole silicon layer step  11 ”, first prepare an n-type silicon wafer  20 ′, and then undergo the following detailed processes as shown in  FIG. 4 . 
         [0036]    The 1st Process  501 : Employ a high-temperature furnace to oxidize and grow a approximately 1000 Å thick Si 3 N 4  layer on both sides (first surface  20 A and second surface  20 B) of the silicon wafer  20 ′. The Si 3 N 4  layer will be used as the etching mask when etching with KOH in later stage. 
         [0037]    The 2nd Process  502 : Define rectangular shapes on the first surface  20 A with photolithographic techniques. 
         [0038]    The 3rd Process  503 : Conduct “reactive ion etching” on first surface  20 A with gold as the HF etching mask to prevent defined rectangular shapes from being damaged by etching solution of HF, and speed up etching with back-lighting method. 
         [0039]    The 4th Process  504 : Utilize an etching solution of KOH to etch predetermined widths and depths of the flow ways  21  on the first surface  20 A of silicon wafer  20 ′, and preserve certain proper thickness as the thickness of gas-diffusion layer. 
         [0040]    The 5th Process  505 : On the second surface  20 B of silicon wafer  20 ′, conduct a photolithographic process to define the pattern and size of the holes  22 . 
         [0041]    The 6th Process  506 : Conduct “reactive ion etching” on the second surface  20 B. 
         [0042]    The 7th Process  507 : Again, employ an etching blocking mask  23  to protect the first surface  20 A, and then etch out multi-hole silicon layer  20  with etching solution of HF so as to form the gas-diffusion layer. 
         [0043]    The 8th Process  508 : Remove the etching blocking mask  23 . 
         [0044]    Concerning the Step  2  “Generating catalytic layer step  12 ”, first prepare multiple catalytic grains (or particles)  24  (EX: the designated metal grains as shown in  FIG. 3 ), and then spread them evenly on the inner wall of the holes  22  of the multi-hole silicon layer  20 , enabling it also work as a catalytic layer. 
         [0045]    In real practice, this step is to employ chemical method to transform the inner walls of holes  22  of the multi-hole silicon layer  20  into positive-charged functional groups, enabling it to attract negative-charged Pt precursor (PtCl 6   2− ) by static electricity, then embed nano Pt grains or particles (catalytic grains  24 ) onto the inner walls of holes  22  through ion exchange method, and finally undergo hydrogen reduction processing to not only increase quantity of Pt grains but also make them evenly spread inside the holes  22 . Comparing to the electro-deposition and physical vapor deposition (PVD) methods that just can deposit catalysts on the surface of the holes  22 , the employment of nano grains can enhance the functionality and life of the fuel cell due to better durability and resistance of the catalysts. Therefore, nano Pt grains  24  is used here as the catalyst in the process. 
         [0046]    In the Step  3  “Forming insulation layer step  13 ”, an insulation layer will be formed on the second surface  20 B. Please refer to the embodiment as shown in  FIGS. 5 and 6 , which comprises the following processes: 
         [0047]    The 9th Process  509 : Define insulation areas needed for the temperature and humidity  25  sensors by photolithographic processing including photoresist coating, exposure, and developing processing. 
         [0048]    The 10th Process  510 : Then conduct dry etch on the defined insulation areas by a reactive ion etching machine. 
         [0049]    The 11th Process  511 : Again, employ another photolithographic processing including photoresist coding, exposure, and developing processing to define other areas than the ones for the electrodes of the temperature and humidity sensors. 
         [0050]    With regard to the Step  4  “Integrating micro sensors step  14 ”, at least one micro sensor layer  40  will be facilitated upon the insulation layer  30 , and it has at least one function selecting from temperature detecting and humidity detecting. 
         [0051]    With references to  FIGS. 5 ,  6 ,  7  and  8 , an embodiment with integration of both temperature and humidity sensors are further described as follows. 
         [0052]    The 12th Process  512 : Coat or deposit a film of Ti and Pt with an e-beam evaporator. 
         [0053]    The 13th Process  513 : Conduct a lift-off processing to make patterns of electrodes for micro temperature and/or humidity sensors. This is to generate the temperature sensor  41  and the lower electrode  421  of the humidity sensor  42 . Although it is shown in the figure that the temperature sensor  41  and the lower electrode  421  share the same layer (or even the same one), the layout can be also modified as the following patterns. 
         [0054]    [a] They are separated horizontally as shown in  FIG. 9 . That is, they are set in designated locations of same layer, but do not touch each other; or, 
         [0055]    [b] They are separated vertically as shown in  FIG. 10 . There is a separating layer  411  between the temperature sensor  41  and the lower electrode  421  of the humidity sensor  42 . It might be made by a conventional coating or depositing technique. 
         [0056]    Therefore, aforementioned methods should be all protected under the scope of the patent claims. 
         [0057]    The 14th Process  514 : Coat the detecting membrane  422 , which is either Benzocyclobutene (BCB) or polyimide, of the humidity sensor  42 . 
         [0058]    The 15th Process  515 : Coat a gold layer by vapor-deposition method via a thermal evaporator. 
         [0059]    The 16th Process  516 : Again, employ photolithographic processing including photoresist coating (to form an outer photoresist layer  43 ), exposure, and developing processing to accomplish an upper electrode  423  of the humidity sensor  42  and necessary conducting lines of the temperature and humidity sensors  41 ,  42 . 
         [0060]    The 17th Process  517 : Then further, etch with etching solution of gold. 
         [0061]    In the Step  5  “Finalizing step  15 ”, this step is to finalize and make a fuel cell with integrations of micro sensor layer  40 , gas-diffusion layer (multi-hole silicon layer  20 ), catalytic layer (the multiple catalytic grains  24  evenly spread inside the holes  22 ), and flow field plates. 
         [0062]    Of course, finally a wire bonder can be employed to connect micro temperature and humidity sensors  41 ,  42  with the PCB board by aluminum lines (not shown in the Fig.), So, it can conduct the temperature and/or humidity detection later. Aforementioned is detailed description of this invention. 
         [0063]    The aforementioned temperature sensor  41  means the detecting areas made by thermal resistant materials, which can be the curvy shape as shown in  FIG. 7 . Such shape is simpler and can contain a longer metal membrane in a small area. It mainly has two functions: 
         [0064]    [1] Detecting temperature: Detect the resistance between the both ends of the temperature sensor  41 , and find out its corresponding temperature value. 
         [0065]    [2] Internal heating: Apply certain voltage between both ends of the temperature sensor  41  to make it generate heats. Thus, the applied voltage can be utilized to force the temperature increasing inside the fuel cell. 
         [0066]    On the other hand, the micro humidity sensor  42  means the detecting areas made by polymeric materials, which generally adopts the sandwich structure (namely capacitor structure). That is, the internal humidity can be found out by detecting the capacity between the upper electrode  423  and lower electrode  421 . Although the manufacturing process is more complicated, the sensitivity can be enhanced because the upper electrode  423  and lower electrode  421  have different locations and have larger contact areas. 
         [0067]    Regarding to the detection of capacity, the capacity is proportional to the lapping area of the upper electrode  423  and lower electrode  421 , and is inversely proportional to the thickness of the micro humidity sensor  42 . In order to increase the capacity, either the thickness of the micro humidity sensor  42  needs to be decreased or the lapping area of the upper electrode  423  and lower electrode  421  needs to be increased. Thus, in the consideration of design of the micro humidity sensor  42 , not only the geometric dimension (EX. Increase the size of the area) needs to be changed, but also the area size of the two electrodes should be considered to prevent occurrence of low capacity and performance of the fuel cell. 
         [0068]    Of course, both temperature sensor  41  and humidity sensor  42  can be adjusted or modified in terms of quantity and measuring range/location. For example, temperature sensor  41  and humidity sensor  42  can be respectively set at the five locations: inlet and outlet of the flow way, one-quarter spot of the total length, two-quarter spot of the total length, and three-quarter spot of the total length. Or it can be designed based actual needs. 
         [0069]    With all aforementioned, the merits of the invention can be summarized as follows: 
         [0070]    [1] The structure is simple after integration. The invention integrates temperature and humidity sensors, gas-diffusion layer, catalytic layer, and flow field plates that are all needed for fuel cell, making its structure simpler. 
         [0071]    [2] It can detect both temperature and humidity simultaneously. The invention introduces insulation layer to the fuel cell, and it attaches micro sensor layer for temperature and humidity sensors, making it capable of conveniently detecting both temperature and humidity of the fuel cell. 
         [0072]    [3] Other than detecting temperature and humidity, it can also generate heats internally. The electrical resistance that makes the temperature sensors not only can be used for detecting the temperature, but also for heating up fuel cell internally when the certain voltage is applied on both sides of the temperature sensor. Thus, it can precisely control the fuel cell at a best operational temperature. 
         [0073]    With all aforementioned, the invention deserves grant of a patent based on its capability of industrial application and absolute novelty. The example illustrated above is just an exemplary embodiment for the invention, and shall not be utilized to confine the scope of the patent. Any equivalent modifications within the scope of claims of the patent shall be covered in the protection for this patent.