Patent Publication Number: US-2023163412-A1

Title: Manufacturing method of separator for fuel cell, and manufacturing method of unit cell for fuel cell

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-189175 filed on Nov. 22, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a manufacturing method of a separator for a fuel cell, and a manufacturing method of a unit cell for a fuel cell. 
     2. Description of Related Art 
     A fuel cell is made up by stacking a plurality of fuel-cell cells (unit cells) that each have a membrane electrode assembly (MEA) and two separators between which the MEA is interposed. The separator and another adjacent separator are joined to each other. 
     For example, in the technology described in Japanese Unexamined Patent Application Publication No. 2016-15310 (JP 2016-15310 A), separators adjacent to each other when unit cells are stacked are joined by laser welding. Prior to laser welding, a joining site and the surroundings thereof are irradiated by laser light (hereinafter referred to as “laser light for cleaning”), in order to remove adhering substances that are adhered to the joining site and the surroundings thereof. The reason is that when there are adhering substances that are adhered to the surface of the separators during joining by laser welding or the like, the quality of joining may deteriorate. 
     SUMMARY 
     However, depending on the form of irradiation of the laser light for cleaning, the amount of heat input to the separator becomes excessively great, and the separators, which are thin plate-shaped members, are warped. 
     The present disclosure can be realized in the following aspects. 
     (1) According to an aspect of the present disclosure, a manufacturing method of a separator for a fuel cell is provided. This manufacturing method includes a cleaning step of irradiating by laser light a joining site of a first separator to which a second separator is to be joined, without joining the first separator and the second separator, and in the cleaning step, at least a part of the joining site is irradiated by the laser light such that a plurality of irradiation marks created by the laser light make up a separated irradiation mark pattern in which the irradiation marks are disposed separated from each other. According to this aspect, at least a part of the joining site is irradiated by laser light so as to make up a separated irradiation mark pattern, and accordingly sites that are irradiated by laser light and are affected by heat (heat-affected sites) can be reduced in comparison with when irradiation is performed such that a pattern is made up in which the irradiation marks are laid out without being separated from each other. That is to say, the amount of heat input to the separators due to laser irradiation can be reduced, and warpage of the separators due to the irradiation by the laser light can be suppressed. 
     (2) In the above aspect, the separated irradiation mark pattern may include a dotted pattern in which all the irradiation marks are disposed separated from each other. According to this form, in the dotted pattern, all the irradiation marks are disposed separated from each other, and accordingly the amount of heat input due to the laser irradiation to the separator can be suitably reduced. 
     (3) In the above aspect, in the separated irradiation mark pattern, the irradiation marks may be disposed equidistantly. According to this form, in the separated irradiation mark pattern, the irradiation marks are disposed equidistantly, and accordingly the cleaning by irradiation can be made uniform. 
     (4) In the above aspect, the separated irradiation mark pattern may include a row pattern containing a plurality of irradiation mark groups in which part of the irradiation marks that are adjacent are disposed overlapping each other, and the irradiation mark groups are disposed in row arrangements separated from each other. According to this form, the cleaning capability can be enhanced in the site of the irradiation mark group in which part of adjacent irradiation marks are disposed overlapping. The irradiation mark groups are separated from each other in rows, and accordingly the amount of heat input by laser irradiation to the separator can be reduced. 
     (5) In the above aspect, in the cleaning step, a first part of the joining site of the first separator may be irradiated by the laser light such that the row pattern is made up, the first separator making up a pair of separators included in a unit cell. The joining site may be a site at which the first separator and the second separator making up the pair of separators are to be joined. The first part of the joining site may be a part on which a force that separates the first separator and the second separator away from each other due to pressure of gas flowing through the unit cell acts more greatly than on other parts of the joining site. According to this form, a first part of the joining site on the separator surface on which a force that separates the separators making up a unit cell from each other due to effects of pressure of gas flowing through the unit cell acts more greatly than on other parts, may be irradiated by the cleaning laser such that the row pattern that is cleaned by a higher cleaning force than the dotted pattern is made up thereat. Accordingly, warpage of the separator can be reduced while maintaining the cleaning capability at sites where the peeling force exerts a large force on the separator, and thus maintaining joining strength. 
     (6) In the above aspect, in the cleaning step, irradiation by the laser light may be performed such that a direction in which the pressure of the gas acts and an array direction of the irradiation mark groups match each other in the row pattern. According to this form, separations between rows where the joining strength is lower than at the sites where the irradiation marks are created are not continuous in the direction in which the gas pressure acts, and thus the joining strength can be enhanced with respect to the input of gas pressure, in comparison with when the direction in which the gas pressure acts and the array direction of the irradiation mark group of the row pattern are orthogonal, for example. 
     (7) In the above aspect, the separator may have a refrigerant outlet hole passing through the separator, and in the cleaning step, a second part of the joining site of the first separator may be irradiated by the laser light such that the row pattern is made up. The joining site may be a site at which the first separator and the second separator making up a unit cell along with the first separator are to be joined. The second part of the joining site may be a part situated at a perimeter of the refrigerant outlet hole. 
     According to this form, when the separator makes up a unit cell, the cleaning site situated on the perimeter of the refrigerant outlet hole which is a second part of the joining site on which a force that peels the two separators away from each other due to effects of pressure of gas is greater than at other parts on the separator surface, may be irradiated by the cleaning laser such that the row pattern that is cleaned by a higher cleaning force than the dotted pattern is made up thereat. Accordingly, at the cleaning site situated on the perimeter of the refrigerant outlet hole, warpage of the separator can be reduced while maintaining the cleaning capability, and thus maintain the joining strength. 
     (8) In the above aspect, the separator may further include a refrigerant inlet hole passing through the separator, and a channel groove fashioned extending from the refrigerant inlet hole toward a side of the refrigerant outlet hole, and in the cleaning step, irradiation by the laser light may be performed such that a direction in which the channel groove extends and the array direction of the irradiation mark groups match each other in the row pattern. 
     The direction in which the channel groove extends substantially matches with the direction in which the pressure of the gas flowing inside the unit cell acts when the separator makes up a unit cell. According to this form, separations between rows where the joining strength is lower than at the sites where the irradiation marks are created are not continuous in the direction in which the gas pressure acts, and thus the joining strength can be enhanced with respect to the input of gas pressure, in comparison with when the direction in which the gas pressure acts and the array direction of the irradiation mark group of the row pattern are orthogonal, for example. 
     (9) According to another aspect of the present disclosure, a manufacturing method of a unit cell for a fuel cell is provided. The manufacturing method of a separator for a fuel cell includes a separator manufacturing step of manufacturing a separator by the manufacturing method according to the above aspect, a separator preparing step of preparing a plurality of the separators manufactured by the separator manufacturing step, an adhesive sheet member installing step of interposing a thermoplastic adhesive sheet member between the separators prepared in the separator preparing step, and a thermocompression bonding step of joining the separators stacked by interposing the thermoplastic adhesive sheet member between the separators in the adhesive sheet member installing step, by thermocompression bonding. According to this aspect, in the manufacturing, a separator can be manufactured in which warpage of the separator due to irradiation of laser light is suppressed. Further, by going through the preparing of the separator, the installing of the adhesive sheet member, and the thermocompression bonding, a unit cell for a fuel cell that uses the thermoplastic adhesive sheet member can be suitably manufactured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG.  1    is a perspective view illustrating a schematic configuration of a fuel cell to which separators, manufactured by a manufacturing method of a fuel cell separator according to a first embodiment of the present disclosure, are applied; 
         FIG.  2    is a plan view illustrating a separator manufactured by the manufacturing method of a separator according to the first embodiment; 
         FIG.  3    is a flowchart showing procedures of the manufacturing method of a separator for a fuel cell; 
         FIG.  4    is a diagram schematically illustrating a dotted pattern; 
         FIG.  5    is a diagram schematically illustrating a row pattern; 
         FIG.  6    is a diagram illustrating a heat-affected range due to being subjected to laser irradiation processing; 
         FIG.  7    is a diagram illustrating an example of an irradiation mark pattern in a comparative form; and 
         FIG.  8    is a flowchart showing procedures in a manufacturing method of a unit cell for a fuel cell. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A. First Embodiment 
     A1. Overall Configuration of Fuel Cell 
       FIG.  1    is a perspective view illustrating a schematic configuration of a fuel cell  500  to which separators  10  and  20 , manufactured by a manufacturing method of a fuel cell separator according to a first embodiment of the present disclosure, are applied. Note that in  FIG.  1   , surfaces of the separators  10  and  20  are illustrated partially simplified. The fuel cell  500  is formed by stacking a plurality of fuel cell unit cells  300  (hereinafter, also simply referred to as “unit cell  300 ”) in a stacking direction SD. Hereinafter, an X-axis and a Y-axis are parallel to a lateral plane, and a Z-axis is parallel to a vertical direction. A+Z direction indicates vertically upward, and a −Z direction indicates vertically downward. In the present embodiment, the stacking direction SD is a direction parallel to the Y-axis. In the present embodiment, the unit cell  300  is a solid polymer fuel cell. Six manifolds  2  to  7  are formed inside the fuel cell  500 . 
     An oxidant gas supply manifold  2  supplies air, which is an oxidant gas, to each unit cell  300 . A cooling medium supply manifold  3  supplies a cooling medium to each unit cell  300 . A fuel gas discharge manifold  4  discharges the fuel gas discharged from each unit cell  300  to the outside of the fuel cell  500 . A fuel gas supply manifold  5  supplies hydrogen gas, which is a fuel gas, to each unit cell  300 . A cooling medium discharge manifold  6  discharges the cooling medium discharged from each unit cell  300  to outside of the fuel cell  500 . An oxidant gas discharge manifold  7  discharges the oxidant gas discharged from each unit cell  300  to the outside of the fuel cell  500 . All six of the manifolds  2  to  7  extend in parallel with the stacking direction SD. 
     Each unit cell  300  includes a Membrane Electrode and Gas diffusion layer Assembly (MEGA) plate  280  and a pair of separators, which are a first separator  10  and a second separator  20 , and which are disposed so as to interpose the MEGA plate  280  therebetween in the stacking direction. Hereinafter, the first separator  10  and the second separator  20  may be referred to simply as “separators  10  and  20 ”, when not distinguished in particular. 
     The MEGA plate  280  includes a MEGA  200  and a support frame  250 . The MEGA  200  has a configuration in which a solid polymer electrolyte membrane, an anode-side catalyst electrode layer, a cathode-side catalyst electrode layer, an anode-side gas diffusion layer, and a cathode-side gas diffusion layer are stacked in the stacking direction SD. A through hole is provided in a middle portion of the support frame  250  in a thickness direction (Y-axis direction), and the MEGA  200  is disposed in the through hole. Note that the support frame  250  is made of a thermoplastic adhesive sheet, and the MEGA plate  280  corresponds to a “thermoplastic adhesive sheet member”. 
     A2. Configuration of Separator 
     Next, the configurations of the separators  10  and  20  will be described. The separators  10  and  20  are thin plate members each having a substantially rectangular shape, and protruding and recessed shapes are formed on both sides thereof in the stacking direction SD. These protruding and recessed shapes form in-cell gas flow channels through which reactive gas (fuel gas or oxidant gas) flows.  FIG.  2    is a plan view illustrating the first separator  10  manufactured by the manufacturing method of the separator according to the first embodiment.  FIG.  2    illustrates, of both faces of the first separator  10 , the face facing the MEGA plate  280 . The shape of the second separator  20  and the shape of the first separator  10  are in a plane-symmetrical relation. Accordingly, the first separator  10  will be described representatively. 
     As illustrated in  FIG.  2   , the first separator  10  has a power generation reaction portion  11 , a first manifold portion  12 , a second manifold portion  13 , an inlet buffer portion  14 , and an outlet buffer portion  15 . The power generation reaction portion  11  is situated at a substantially middle position in an X direction, and is situated between the first manifold portion  12  and the second manifold portion  13 . The power generation reaction portion  11  has a plurality of channel grooves  21  extending linearly in the X direction. 
     The first manifold portion  12  is situated at an edge portion in a −X direction. The first manifold portion  12  has an oxidant gas inlet hole  22 , a refrigerant inlet hole  23 , and a fuel gas outlet hole  24 . These holes  22 ,  23 , and  24  each pass through the separator  10  in a Y direction, and are formed in this order in the −Z direction. 
     The second manifold portion  13  is situated at an edge portion in a +X direction. The second manifold portion  13  has a fuel gas inlet hole  25 , a refrigerant outlet hole  26 , and an oxidant gas outlet hole  27 . These holes  25 ,  26 , and  27  each pass through the separator  10  in the Y direction, and are formed in this order in the −Z direction. When the fuel cell  500  is assembled by stacking the unit cells  300 , the holes  22  to  27  are overlaid in the stacking direction SD to form the above-described six manifolds  2  to  7 . 
     The inlet buffer portion  14  has a plurality of embossed portions  28 , and is provided between the first manifold portion  12  and the power generation reaction portion  11 . The outlet buffer portion  15  has a plurality of embossed portions  29 , and is provided between the second manifold portion  13  and the power generation reaction portion  11 . 
     The channel grooves  21  of the first separator  10  function as a channels through which the oxidant gas flows from the oxidant gas inlet hole  22  to the oxidant gas outlet hole  27 . Channel grooves that are omitted from illustration are similarly formed on a rear face of the first separator  10 , and the channel grooves function as a refrigerant channels through which the refrigerant flows from the refrigerant inlet hole  23  to the refrigerant outlet hole  26 . Similar to the first separator  10 , the second separator  20  is formed with channel grooves on both the front and rear faces, and one of the channel grooves functions as refrigerant channels, as with the channel grooves  21 . The other of the channel grooves function as fuel gas channels for fuel gas to flow from the fuel gas inlet hole  25  to the fuel gas outlet hole  24 . 
     A3. Separator Manufacturing Method 
     Next, a manufacturing method of the separators  10  and  20  will be described.  FIG.  3    is a flowchart showing procedures of the manufacturing method of the fuel cell separators  10  and  20  according to the first embodiment. As shown in  FIG.  3   , in the manufacturing method of the fuel cell separators  10  and  20 , first, a press molding process is executed in step S 101  (hereinafter, “step” will be abbreviated to “S”), and subsequently, a cleaning process is performed in S 102 . In the press molding process (S 101 ), outer shapes of the separators  10  and  20  having the holes  22  to  27  and the channel grooves  21 , described above, are formed by press molding. 
     In the cleaning process (S 102 ), joining surfaces of the separators  10  and  20  to be joined to each other to form the unit cell  300 , i.e., the surfaces on the sides where the separators  10  and  20  face the MEGA plate  280 , are irradiated by laser light for cleaning. In  FIG.  2   , a cleaning site A, which is a portion to be laser-cleaned in the cleaning process (S 102 ), is indicated by dashed lines. Further, the cleaning site A corresponds to a joining site for joining the first separator  10  and the second separator  20 , the “joining site” and the “cleaning site” being substantially the same site. 
     In the cleaning process (S 102 ), a separator (first separator  10  making up a certain unit cell  300 ) is irradiated by laser light without being joined to the joining site of another separator (second separator  20  making up the certain unit cell  300 ) which is to be paired with the separator to make up the certain unit cell  300  together. 
     As illustrated in  FIG.  2   , the cleaning site A includes an outer peripheral cleaning site A1 along the vicinity of an outer peripheral edge of the separator  10 , and hole peripheral cleaning sites A2 that surround around the oxidant gas inlet hole  22 , around the refrigerant inlet hole  23 , around the refrigerant outlet hole  26 , and around the oxidant gas outlet hole  27 . A hole peripheral cleaning site A2 situated at a perimeter of the refrigerant outlet hole  26  and a second part of the joining site are substantially the same site. 
     As a method of joining the separators  10  and  20 , in the present embodiment, a method of interposing the MEGA plate  280  between the separators  10  and  20 , and performing hot pressing on the joining sites to perform thermoplastic joining is employed. When adhering substance are adhering to the surfaces of the separators  10  and  20  at the time of this joining, the joining quality may deteriorate. Accordingly, prior to the joining process, a cleaning process of irradiating the joining site by cleaning laser light is performed in order to remove the adhering substances that are adhered to the joining site. Details of the manufacturing method of the unit cell  300 , including the process of joining the separators  10  and  20  using the above MEGA plate  280  serving as a thermoplastic adhesive sheet member, will be described later. 
     In the cleaning process (S 102 ) according to the present embodiment, the cleaning site A is subjected to irradiation by the cleaning laser light, such that a plurality of irradiation marks  31  (see  FIGS.  4  and  5   ) formed by the cleaning laser light are disposed separated from each other, making up a separated irradiation mark pattern. The separated irradiation mark pattern has two patterns, a dotted pattern DP and a row pattern LP. The dotted pattern DP and the row pattern LP differ in the forms in which the irradiation marks  31  are formed. 
       FIG.  4    is a diagram schematically illustrating the dotted pattern DP. As illustrated in  FIG.  4   , in the dotted pattern DP, all the irradiation marks  31  having circular shapes are separated from each other and disposed equidistantly. Predetermined gaps  32  are formed between the adjacent irradiation marks  31 .  FIG.  5    is a diagram schematically illustrating the row pattern LP. As illustrated in  FIG.  5   , the row pattern LP has a plurality of irradiation mark groups  33  in which adjacent irradiation marks  31  having circular shapes are disposed partially overlapping each other, and the irradiation mark groups  33  are disposed as rows separated from each other. Predetermined gaps  34  are formed between the adjacent irradiation mark groups  33 . Note that while the irradiation marks  31  are schematically illustrated as being precise circles in  FIGS.  4  and  5   , the shape is not a precise circle but actually is rather a shape close to an ellipse, for example, depending on the specifications of the laser beam that is used. Also, the diameter of each of the irradiation marks  31  is, for example, about 100 μm to 150 μm. 
       FIG.  6    is a diagram illustrating a heat-affected range  41  when subjected to laser irradiation processing, and is a photograph showing the surface of a black-stained experimental separator  30  following laser cleaning processing thereof. In  FIG.  6   , an irradiation mark  31  is illustrated surrounded by a thin continuous line, and a heat-affected range  41 , which is affected by heat by the laser irradiation, is illustrated surrounded by a dashed line. As shown in  FIG.  6   , black staining is not removed in the portion outside the heat-affected range  41 , but the heat-affected range  41  is larger than the irradiation mark  31  and extends beyond the outside of the irradiation mark  31 , and accordingly impurities can be removed within the heat-affected range  41 . 
       FIG.  7    is a diagram illustrating an example of an irradiation mark pattern CP in a comparative form. As illustrated in  FIG.  7   , in the comparative form, the irradiation mark pattern CP is formed in which the irradiation marks  31  are laid out without gaps. Adhering substances can still be removed even if the irradiation marks  31  are separated by a predetermined distance and formed at intervals as in the separated irradiation mark pattern according to the present embodiment, even without using such an irradiation mark pattern CP. 
     In the above-described dotted pattern DP and row pattern LP, gaps  32  and  34  are formed between the irradiation marks  31  or between the irradiation mark groups  33 , with the gaps  32  and  34  being set so as to be within the heat-affected range  41  and accordingly adhering substances can be removed from the gaps  32  and  34  as well. While the diameter and spacing of the irradiation marks  31  can be changed as appropriate, the diameter and the spacing are identified and set in advance by experimentation and so forth, as values of a level that satisfy predetermined threshold values regarding the range covered by the heat-affected range  41 . Further, the row pattern LP is formed by the irradiation marks  31  partially overlapping in one direction (the up-down direction as illustrated in  FIG.  5   ), and due to the area irradiated by the laser being greater than that of the dotted pattern DP, cleaning capability by laser irradiation is higher. 
     In the cleaning process (S 102 ) in the manufacturing method of the separator according to the first embodiment, cleaning is performed regarding, out of the hole peripheral cleaning sites A2, a cleaning site around the refrigerant outlet hole  26  that is situated on the −X direction side and extends in the Z direction (hereinafter, referred to as “high input site A3” (see  FIG.  2   )), so as to make up a row pattern LP. The high input site A3 is a site being cleaned and situated in a high input region HA in  FIG.  2   , and the high input site A3 and a first part of the joining site are substantially the same site. The other joining sites (sites illustrated as joining portions DA, for example, in  FIG.  2   ) are cleaned so as to make up a dotted pattern DP. 
     In the configuration in which the separators  10  and  20  are stacked to form the unit cells  300  and the unit cells  300  are further stacked to form the fuel cell  500 , the high input region HA is a site at which force acting to peel the two separators  10  and  20  away from each other is greater than at other sites of the joining surfaces of the separators  10  and  20 , due to the pressure of the reactive gas flowing through the unit cells  300  thereat. Accordingly, the high input site A3, which is a cleaning site situated in the high input region HA, is subjected to laser cleaning to make up the row pattern LP, of which cleaning capability is high, so that joining strength can be increased by removing the adhering substance more reliably. 
     Further, in the first embodiment, as illustrated in  FIG.  5   , irradiation by laser is performed so that a direction D 1  in which the gas pressure acts and an array direction D 2  of the irradiation mark groups  33  of the row pattern LP match each other. The array direction D 2  is a direction that intersects (orthogonally in the present embodiment) the direction in which the irradiation mark groups  33  extend linearly. By matching the direction D 1  in which the gas pressure acts with the array direction D 2  of the irradiation mark groups  33 , the irradiation marks  31  and the gaps  34  between the rows of the irradiation mark groups  33  are alternatingly formed in the direction D 1  in which the gas pressure acts. 
     Note that the “direction D 1  in which the gas pressure acts” and the “direction in which the channel grooves  21  extend” are substantially the same. The irradiation marks  31  are disposed in rows without gaps in the direction orthogonal to the direction D 1  in which the gas pressure acts, and accordingly resistance to the gas pressure can be improved. 
     Adjustment of irradiation mark patterns is performed by a known laser welding device. A laser light emitting unit that the laser welding device is provided with moves over lines in the cleaning site A, while emitting the laser light. A light emitting unit actuator moves the laser light emitting unit so as to make up the irradiation mark patterns based on instructions of a control unit. 
     In the dotted pattern DP, the irradiation is turned off every other irradiation in the scanning direction and the feed direction of the laser light emitting unit. In the row pattern LP, when forming one irradiation mark group  33 , the laser light emitting unit is scanned so that the irradiation marks  31  overlap in the scanning direction of the laser light emitting unit, and then the irradiation mark group  33  of the next row is formed in the same manner as described above, after turning off the irradiation in the feed direction of the laser emitting unit such that the gap  34  is formed therebetween. The irradiation mark patterns may be adjusted by a laser device provided with a galvanometer scanner capable of scanning the laser in two-dimensional directions by changing the reflection direction of the laser. 
     A4. Manufacturing Method of Unit Cell 
     Next, a manufacturing method of the unit cell  300  will be described with reference to  FIG.  8   .  FIG.  8    is a flowchart showing procedures in the manufacturing method of the unit cell  300 . As shown in  FIG.  8   , the manufacturing method of the unit cell  300  includes a separator manufacturing process (S 100 ), a separator preparation process (S 200 ), an adhesive sheet member installation process (S 300 ), and a thermocompression bonding process (S 400 ), in the order of execution. 
     In the separator manufacturing process (S 100 ), the first separator  10  and the second separator  20  are manufactured by the above-described separator manufacturing method. In the separator preparation process (S 200 ), the first separator  10  and the second separator  20  manufactured in the separator manufacturing process (S 100 ) are prepared. In the adhesive seal member installation process (S 300 ), the MEGA plate  280  (thermoplastic adhesive sheet member) is interposed between the first separator  10  and the second separator  20 , and installed. In the thermocompression bonding process (S 400 ), the separators  10  and  20  stacked with the MEGA plate  280  (thermoplastic adhesive sheet member) interposed therebetween are joined by thermocompression bonding. Thus, the unit cell  300  is manufactured. 
     (1) 
     In the manufacturing method of the separators  10  and  20  according to the first embodiment, in the cleaning process (S 102 ), irradiation by cleaning laser light is performed for the cleaning site A such that the irradiation marks  31  are disposed separated from each other, so as to make up a separated irradiation mark pattern. Accordingly, regions affected by heat by being irradiated by the laser light can be reduced in comparison with when irradiating with the irradiation mark pattern CP (see  FIG.  7   ) in which the irradiation marks  31  are laid out without being separated from each other. 
     That is to say, the amount of heat input to the separators  10  and  20  due to laser irradiation can be reduced, and warpage of the separators  10  and  20  due to the irradiation by the cleaning laser light can be suppressed. In a situation in which the separators  10  and  20  are warped, there is a risk that the separators  10  and  20  may be improperly transported such as interfering with a jig or the like in a transporting process, and joining defects or the like may occur, but such trouble can be avoided. 
     (2) 
     In the manufacturing method of the separators  10  and  20  according to the first embodiment, irradiation by the cleaning laser is performed so as to make up the row pattern LP that is cleaned with a higher cleaning power than the dotted pattern DP at the high input site A3, which is where the force acting to peel the joining of the separators  10  and  20  away from each other is great when configured as the unit cell  300  for a fuel cell. Accordingly, adhering substances in the high input site A3 can be removed more reliably, and the joining strength in the subsequent joining process can be enhanced. 
     (3) 
     Also, in the manufacturing method of the separators  10  and  20  according to the first embodiment, the outer peripheral cleaning site A1 regarding which relatively low strength is allowable is irradiated by a cleaning laser so as to make up the dotted pattern DP. That is to say, by appropriately using a plurality of separated irradiation mark patterns having different cleaning capabilities (and thus different bonding strengths) in accordance with the strength respectively required for a plurality of the cleaning sites, warpage of the separators  10  and  20  can be suitably reduced, while maintaining joining strength at sites requiring strength. 
     (4) 
     Further, the high input site A3 is subjected to irradiation by laser so that the direction D 1  in which the gas pressure acts and the array direction D 2  of the irradiation mark groups  33  of the row pattern LP match each other. Accordingly, the gaps  34  between the rows having a lower bonding strength than the sites where the irradiation marks  31  are formed are not continuous in the direction D 1  in which the gas pressure acts, and thus the joining strength can be enhanced with respect to the input of gas pressure, in comparison with when the direction D 1  in which the gas pressure acts and the array direction D 2  of the irradiation mark groups  33  of the row pattern LP are orthogonal, for example. 
     B. Other Embodiments 
     (B1) 
     In the first embodiment above, the irradiation marks  31  in the dotted pattern DP are disposed at equal intervals, but the irradiation marks  31  do not have to be equidistantly spaced, as long as the heat-affected range  41  can be achieved as desired. Also, the intervals of the irradiation mark groups  33  in the row pattern LP do not have to be equidistantly spaced, either. 
     (B2) 
     In the first embodiment above, the cleaning site A includes the outer peripheral cleaning site A1 and the hole peripheral cleaning sites A2, but the cleaning site A (joining site) is not limited to this form, and can be changed as appropriate, in accordance with the product specifications of the separators  10  and  20 . 
     (B3) 
     In the first embodiment above, the separated irradiation mark patterns include the dotted pattern DP and the row pattern LP, but may include just one of these, or other patterns in which the irradiation marks  31  are disposed separated from each other may be used. 
     (B4) 
     In the first embodiment above, the irradiation by laser is performed on the entirety of the cleaning site A so as to make up separated irradiation mark patterns, but at least a part of the cleaning site A may be provided with separated irradiation mark patterns. For example, an arrangement may be made in which the high input site A3 where strength is required is irradiated so as to make up the irradiation mark pattern CP, in which the irradiation marks  31  are laid out as illustrated in  FIG.  7    as a comparative form, and the other cleaning sites A1 and A2 are irradiated so that separated irradiation mark patterns are formed. Further, the way in which the dotted pattern DP and the row pattern LP are used for the cleaning sites may be changed as appropriate. For example, an arrangement may be made in which all hole peripheral cleaning sites A2 including the high input site A3 are irradiated so as to make up the row patterns LP, and the outer peripheral cleaning site A1 is irradiated so as to make up dotted patterns DP. 
     (B5) 
     In the manufacturing method of the separator according to the first embodiment, a manufacturing method has been described in which the cleaning process (S 102 ) is carried out as preprocessing for joining the joining faces of the separators  10  and  20  that are thermoplastically joined using the MEGA plate  280  as a thermoplastic adhesive sheet member, i.e., for joining the inner face sides of the unit cell  300  of the separators  10  and  20  making up one unit cell  300 . Alternatively, a manufacturing method may be used in which, for example, a cleaning process is performed as preprocessing when outer face sides of unit cells  300  are joined by welding. 
     The present disclosure is not limited to the embodiments above, and can be realized by various configurations without departing from the essence thereof. For example, the technical features of the embodiments corresponding to the technical features in each aspect described in the section of the summary of the disclosure may be replaced or combined appropriately to solve part or all of the above issues or to achieve part or all of the above effects. When the technical features are not described as essential in this specification, such technical features can be omitted as appropriate.