Patent Publication Number: US-2017361395-A1

Title: Method for plugging orifice

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-119584, filed on Jun. 16, 2016; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments relate to a method for plugging orifice. 
     BACKGROUND 
     When friction stir welding (FSW) is used, it may be problematic that an exit hole of the friction stir welding tool (the tool) remains at the weld end. Therefore, hole-filling methods such as a method of inserting a metal plug into the hole and performing friction stir welding of the surface, a method of performing friction welding of a metal plug into the interior of the hole, a method of inserting a filling material into the hole, etc., have been proposed. 
     Here, due to the function or application of the member, etc., there are cases where it is necessary to plug the surface while ensuring a space inside the hole provided in the member. However, a space cannot remain in the interior of the member in conventional methods that use a member such as a metal plug, a filling material, etc., because the bottom portion of the hole has the function of receiving these members. 
     Therefore, it is desirable to develop technology to plug only the orifice of the recess or hole provided in the member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view for illustrating a friction stir welding tool; 
         FIG. 2  is a schematic perspective view for illustrating another friction stir welding tool according to the embodiment; 
         FIG. 3  is a schematic view for illustrating the friction stir welding apparatus; 
         FIGS. 4A to 4C  are schematic cross-sectional views for illustrating the method for plugging the orifice according to the embodiment; 
         FIGS. 5A and 5B  are photographs for illustrating the plug portion formed by the method for plugging the orifice according to the embodiment; 
         FIG. 6  is a photograph for illustrating a plug portion formed by laser welding; 
         FIG. 7  is a schematic perspective view for illustrating a liquid cooling jacket; 
         FIGS. 8A to 8C  are schematic views for illustrating a method for manufacturing a liquid cooling jacket according to a comparative example; 
         FIGS. 9A to 9C  are schematic views for illustrating a method for manufacturing the liquid cooling jacket using the method for plugging the orifice according to the embodiment; and 
         FIGS. 10A to 10E  are schematic views for illustrating the method for manufacturing the liquid cooling jacket using the method for plugging the orifice according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a method is disclosed for plugging an orifice. The method can include rotating a tool including a shoulder portion and a probe pin, and inserting the probe pin into a member having an orifice. The probe pin is provided at an end portion of the shoulder portion. The method can include forming a plug portion by moving the rotating tool to traverse the orifice. The plug portion plugs the orifice. 
     Embodiments will be described below as an example with reference to the drawings. In the respective drawings, the same components are denoted by the same reference numerals, and the detailed description thereof will be omitted appropriately. 
     The method for plugging orifice according to the present embodiment can be performed by using the friction stir welding method. Therefore, first, the friction stir welding tool and a friction stir welding device used for the method for plugging orifice according to the present embodiment will be exemplified. 
     Friction Stir Welding Tool 
       FIG. 1  is a schematic perspective view for illustrating a friction stir welding tool. 
     As shown in  FIG. 1 , the friction stir welding tool  1  (hereinbelow, called simply the tool  1 ) includes a shoulder portion  2 , a probe pin  3 , and a shank  4 . 
     The shoulder portion  2 , the probe pin  3 , and the shank  4  are formed as one body. 
     Although the material of the shoulder portion  2 , the probe pin  3 , and the shank  4  is not particularly limited, it is favorable to use a material that is harder than the material of the member to be processed. The material of the shoulder portion  2 , the probe pin  3 , and the shank  4  may be, for example, tool steel, a tungsten alloy, a ceramic, etc. 
     Although the form of the shoulder portion  2  is not particularly limited, considering the anti-wear properties, the manufacturability, etc., it is desirable for the form of the shoulder portion  2  to have a cylindrical column configuration (a circular columnar configuration). 
     The shank  4  is the mounting portion of the tool  1  for a friction stir welding apparatus  100 . 
     The shank  4  may have a cylindrical column configuration. 
     The probe pin  3  is provided at substantially the center of the shoulder portion  2 . 
     A central axis  2   a  of the shoulder portion  2 , a central axis  3   a  of the probe pin  3 , and a central axis  4   a  of the shank  4  are positioned on the same straight line. The central axis  2   a  of the shoulder portion  2 , the central axis  3   a  of the probe pin  3 , and the central axis  4   a  of the shank  4  match a central axis  1   a  of the tool  1 . In other words, the probe pin  3 , the shoulder portion  2 , and the shank  4  are provided to be concentric. However, there may be decentering that is about the size of the manufacturing fluctuation. 
     The probe pin  3  has a columnar configuration. The probe pin  3  has a form in which the diameter (the cross-sectional dimension) gradually decreases toward the tip. In other words, the probe pin  3  has a frustum of a right circular cone configuration (a truncated circular conical configuration). The loads on the tool  1  and the member to be processed when the tool  1  is inserted into the member can be reduced by providing the probe pin  3  with a frustum of a right circular cone configuration. 
     Here, if a groove having a spiral configuration is provided in a side surface  3   b  of the probe pin  3 , plastic flow of the material can be caused in the central axis  1   a  direction of the tool  1  in addition to the rotation direction of the tool  1 . Therefore, in a butt joining where the side faces of the members are joined together, if the tip of the probe pin  3  is inserted to a depth of 90% to 95% of the thickness of the member to be bonded, the entire region in the thickness direction of the bonding portion can be bonded by the plastic flow in the central axis  1   a  direction. Therefore, a groove that has a spiral configuration is provided in the side surface  3   b  of the probe pin  3  in the case of a general friction stir welding tool. 
     However, if the material is caused to flow plastically in the central axis  1   a  direction of the tool  1  when plugging a hole  200   b  (referring to  FIGS. 4A to 4C ) provided in the member, the material is introduced easily into the interior of the hole  200   b , etc.; and it becomes difficult to obtain the desired plug depth with high precision. The excessively introduced material is not bonded to the wall surface of the hole  200   b . Therefore, the excessively ontroduced material may separate from the bottom of the plugged hole  200   b  and become metal scraps. If the amount of the material introduced to the interior of the hole  200   b , etc., increases, the amount of the material that can be used to plug the orifice decreases by this amount. Therefore, there is a risk that defects may occur in the surface of a plug portion  200   c  (referring to  FIG. 4C ) formed in the orifice. 
     Therefore, in the tool  1  according to the embodiment, a groove having a spiral configuration is not provided in the side surface  3   b  of the probe pin  3 . In other words, the side surface  3   b  of the probe pin  3  is a smooth curved surface. 
     In a direction orthogonal to the central axis  1   a  of the tool  1 , the diameter (the cross-sectional dimension) of the probe pin  3  is smaller than the diameter (the cross-sectional dimension) of the shoulder portion  2 . 
     For example, the diameter (the cross-sectional dimension) of the shoulder portion  2  may be set to be not less than 2 times and not more than 3 times the diameter (the tip diameter) of the front end portion of the probe pin  3 . However, the dimensional relationship between the diameter (the tip diameter) of the front end portion of the probe pin  3  and the diameter (the cross-sectional dimension) of the shoulder portion  2  is not limited to that illustrated and may be modified appropriately according to the material of the member, the processing conditions, etc. 
     Here, if the amount of the material that flows plastically is low, there is a risk that defects such as voids, etc., may occur in the plug portion  200   c  that is formed (referring to  FIG. 4C ). 
     In such a case, the amount of the material that flows plastically has a positive correlation with the volume of the probe pin  3 . Therefore, the occurrence of defects such as voids, etc., in the plug portion  200   c  can be suppressed by correcting the volume of the probe pin  3 . 
     The volume of the probe pin  3  can be controlled by the base diameter, the diameter (the tip diameter) of the front end portion, and the height of the probe pin  3 . 
     In such a case, it is difficult to increase the change amount of the height of the probe pin  3  because the height is set to be about the same as the thickness of the plug portion  200   c.    
     According to knowledge obtained by the inventor, the occurrence of defects such as voids, etc., in the plug portion  200   c  can be suppressed by satisfying the following formula. 
         D 1≧2× D 2
 
     D 1  is the diameter (the tip diameter) of the front end portion of the probe pin  3  in a direction orthogonal to the central axis  1   a  of the tool  1 ; and D 2  is the cross-sectional dimension of the orifice of the hole  200   b , a recess  200   a , etc., provided in a member  200 . 
       FIG. 2  is a schematic perspective view for illustrating another friction stir welding tool according to the embodiment. 
     As shown in  FIG. 2 , the friction stir welding tool  11  (hereinbelow, called simply the tool  11 ) includes the shoulder portion  2 , a probe pin  13 , and the shank  4 . 
     The shoulder portion  2 , the probe pin  13 , and the shank  4  are formed as one body. 
     The probe pin  13  is provided at substantially the center of the shoulder portion  2 . 
     The material of the probe pin  13  may be the same as the material of the probe pin  3  described above. 
     The central axis  2   a  of the shoulder portion  2 , a central axis  13   a  of the probe pin  13 , and the central axis  4   a  of the shank  4  are positioned on the same straight line. The central axis  2   a  of the shoulder portion  2 , the central axis  13   a  of the probe pin  13 , and the central axis  4   a  of the shank  4  match a central axis  11   a  of the tool  11 . In other words, the probe pin  13 , the shoulder portion  2 , and the shank  4  are provided to be concentric. However, there may be decentering that is about the size of the manufacturing fluctuation. 
     Although the probe pin  3  has a frustum of a right circular cone configuration, the probe pin  13  has a cylindrical column configuration. 
     In the tool  11  according to the embodiment as well, a groove having a spiral configuration is not provided in a side surface  13   b  of the probe pin  13 . In other words, the side surface  13   b  of the probe pin  13  is a smooth curved surface. 
     The diameter (the cross-sectional dimension) of the shoulder portion  2  may be set to be about 2 to 3 times the diameter (the tip diameter) of the front end portion of the probe pin  13 . However, the dimensional relationship between the diameter (the tip diameter) of the front end portion of the probe pin  13  and the diameter (the cross-sectional dimension) of the shoulder portion  2  is not limited to that illustrated and may be modified appropriately according to the material of the member, the processing conditions, etc. 
     Similarly to the probe pin  3  described above, the occurrence of defects such as voids, etc., in the plug portion  200   c  can be suppressed by satisfying the following formula. 
         D 11≧2× D 2
 
     D 11  is the diameter (the tip diameter) of the front end portion of the probe pin  13  in a direction orthogonal to the central axis  11   a  of the tool  11 ; and D 2  is the cross-sectional dimension of the orifice of the hole  200   b , the recess  200   a , etc., provided in the member  200 . 
     Friction Stir Welding Apparatus 
     The friction stir welding apparatus  100  will now be illustrated. 
       FIG. 3  is a schematic view for illustrating the friction stir welding apparatus. 
     Arrows X, Y, and Z in  FIG. 3  illustrate three directions orthogonal to each other. For example, arrow Z illustrates a vertical direction; and arrow X and arrow Y illustrate horizontal directions. 
     The friction stir welding apparatus  100  shown in  FIG. 3  plugs the orifice of the hole  200   b , the recess  200   a , etc., provided in the member  200 . 
     The friction stir welding apparatus  100  may be mounted on a floor surface, etc. 
     A processing part  103  of the friction stir welding apparatus  100  may be mounted to the hand of a six-axis vertical articulated robot, etc. 
     As shown in  FIG. 3 , a placement part  101 , a holder  102 , and the processing part  103  are provided in the friction stir welding apparatus  100 . 
     The member  200  is placed on the placement part  101 . 
     The recess  200   a  that has an opening at the surface of the member  200 , the hole  200   b  that pierces the thickness direction of the member  200 , etc., are provided in the member  200 . The recess  200   a  that has the opening at the surface of the member  200  is provided in the member  200  illustrated in  FIG. 3 . 
     The material of the member  200  is not particularly limited as long as plastic flow can be caused by the friction stir welding. For example, the material of the member  200  may be a metal. The metal may be, for example, aluminum, an aluminum alloy, copper, a copper alloy, titanium, a titanium alloy, magnesium, a magnesium alloy, iron, etc. 
     The form of the member  200  is not particularly limited. For example, the member  200  that has a plate configuration such as that illustrated in  FIG. 3  may be used; and the member  200  that has a block configuration may be used. 
     The holder  102  holds the member  200 . The configuration of the holder  102  is not particularly limited as long as the member  200  can be held. For example, the holder  102  may include a hydraulic cylinder, a control motor such as a servo motor, etc., and may hold the member  200  mechanically. The holder  102  may include an electromagnetic chuck, a vacuum chuck, etc. 
     The processing part  103  holds the shank  4  of the tool  1  ( 11 ). 
     The processing part  103  rotates the tool  1  ( 11 ) around the central axis  103   a.    
     The processing part  103  changes the position of the rotating tool  1  ( 11 ). 
     For example, the processing part  103  inserts the probe pin  3  ( 13 ) into the interior of the member  200  and extracts the probe pin  3  ( 13 ) from the member  200  by changing the position in the Z-direction of the rotating tool  1  ( 11 ). 
     Then, the processing part  103  causes the tool  1  ( 11 ) to traverse the orifice provided in the member  200  by changing the position in the Y-direction or the X-direction of the rotating tool  1  ( 11 ). 
     The processing part  103  may include, for example, a control motor such as a servo motor, etc. 
     Method for Plugging Orifice 
     A method for plugging an orifice according to the embodiment will now be illustrated. 
       FIGS. 4A to 4C  are schematic cross-sectional views for illustrating the method for plugging the orifice according to the embodiment. 
     As shown in  FIG. 4A , the hole  200   b  that pierces the member  200  in the thickness direction is provided in the member  200 . In other words, the hole  200   b  that has an opening at the surface of the member  200  is provided in the member  200 . 
     First, the tool  1  ( 11 ) that includes the probe pin  3  ( 13 ) having an appropriate diameter (a tip diameter) D 1  (D 11 ) of the front end portion is selected according to the cross-sectional dimension D 2  of the orifice. 
     Namely, the tool  1  ( 11 ) that includes the probe pin  3  ( 13 ) is selected so that D 1 ≧2×D 2  (D 11 ≧2×D 2 ). 
     Then, the tool  1  ( 11 ) is rotated using the central axis  1   a  ( 11   a ) of the tool  1  ( 11 ) as the center of rotation. 
     The rotation speed of the tool  1  ( 11 ) may be appropriately set according to the diameter (the tip diameter) D 1  (D 11 ) of the front end portion of the probe pin  3  ( 13 ). In such a case, the rotation speed may be set to increase as the diameter (the tip diameter) D 1  (D 11 ) of the front end portion of the probe pin  3  ( 13 ) decreases. The rotation speed of the tool  1  ( 11 ) may be set to, for example, about 500 rpm to 15000 rpm. 
     Continuing as shown in  FIG. 4B , the probe pin  3  ( 13 ) of the rotating tool  1  ( 11 ) is inserted into the interior of the member  200 . 
     The probe pin  3  ( 13 ) is inserted into the vicinity of the orifice. 
     In such a case, it is favorable for an end portion  2   b  on the probe pin side of the shoulder portion  2  to be inserted about 0.1 mm to 0.2 mm into the interior of the member  200 . 
     The angle between the central axis  1   a  ( 11   a ) of the tool  1  ( 11 ) and a line perpendicular to the surface of the member  200  may be set to, for example, not less than 0° and not more than 3°. This angle is set to 00 in  FIG. 4B . 
     Then, as shown in  FIG. 4C , the rotating tool  1  ( 11 ) is moved along the surface of the member  200 . 
     The movement speed may be modified appropriately according to the material of the member  200 , etc. 
     For example, in the case where the material of the member  200  is 6000-series aluminum, the movement speed may be set to about 100 mm/min to 200 mm/min. 
     The material of the member  200  on the front side of the tool  1  ( 11 ) flows plastically due to frictional heat and pressure. The plastically flowing material moves toward the rearward side of the tool  1  ( 11 ) while being stirred and kneaded as the tool  1  ( 11 ) moves. The material that moves toward the rearward side of the tool  1  ( 11 ) loses frictional heat and solidifies rapidly. Therefore, the orifice of the hole  200   b  is plugged by the material of the member  200 . In other words, the plug portion  200   c  is formed by the solidification of the material moving toward the rearward side of the rotating tool  1  ( 11 ). 
     As described above, a groove that has a spiral configuration is not provided in the side surface  3   b  ( 13   b ) of the probe pin  3  ( 13 ). Therefore, the introduction of the material into the interior of the hole  200   b  can be suppressed when the tool  1  ( 11 ) passes through the orifice of the hole  200   b . In other words, by setting the side surface of the probe pin  3  ( 13 ) to be a smooth curved surface, the introduction of the stir and kneaded material to the interior of the orifice when the rotating tool  1  ( 11 ) traverses the orifice is suppressed. 
     As a result, the occurrence of defects such as voids, etc., in the plug portion  200   c  of the orifice can be suppressed. 
     Also, the temperature at which the material of the member  200  flows plastically is much lower than the melting point of the material. Therefore, compared to the case where the orifice of the hole  200   b  is plugged by laser welding, etc., the temperature increase at the plug portion  200   c  vicinity can be suppressed. As a result, the occurrence of deformation and/or cracks due to thermal strain can be suppressed. Changes of the composition of the material also can be suppressed. 
     Then, the rotating tool  1  ( 11 ) is extracted from the member  200  after the plug portion  200   c  is formed. 
     A mark (a recess) where the probe pin  3  ( 13 ) was inserted is formed at the position where the tool  1  ( 11 ) is extracted. Therefore, the position where the tool  1  ( 11 ) is extracted is set to be a position such that the hole  200   b  does not communicate with the mark (the recess) remaining in the member  200 . In other words, the rotating tool  1  ( 11 ) is extracted from the member  200  at a position such that the orifice does not communicate with the recess formed by extracting the rotating tool  1  ( 11 ). 
     Thus, the orifice of the hole  200   b  provided in the member  200  can be plugged. The orifice of the recess  200   a  provided in the member  200  also can be plugged similarly. 
     In such a case, the plug portion  200   c  is formed at the surface vicinity of the member  200 . A space is formed below the plug portion  200   c.    
     As described above, the method for plugging the orifice according to the embodiment may include the following processes:
         a process of rotating the tool  1  ( 11 ) including the shoulder portion  2  and the probe pin  3  ( 13 ), and inserting the probe pin  3  ( 13 ) into the member  200  having the orifice;   a process of forming the plug portion  200   c  that plugs the orifice by moving the tool  1  ( 11 ) to traverse the orifice, wherein the plug portion  200   c  is formed by solidification of the plastically flowing material of the member  200  in the process of forming the plug portion  200   c  that plugs the orifice; and   a process of extracting the rotating tool  1  ( 11 ) from the member  200 .       

       FIGS. 5A and 5B  are photographs for illustrating the plug portion formed by the method for plugging the orifice according to the embodiment. 
       FIG. 5A  is a photograph of the surface of the member  200 .  FIG. 5B  is a photograph of line A-A′ cross section of  FIG. 5A . In other words,  FIG. 5B  is a cross-sectional photograph of the plug portion  200   c.    
       FIG. 6  is a photograph for illustrating a plug portion formed by laser welding. 
     Defects such as cracks  200   d   1 , etc., occur easily in the plug portion  200   d  as shown in  FIG. 6  in the case where the orifice of a member made of aluminum is plugged using laser welding. This is affected by the large thermal expansion coefficient and solidification contraction of aluminum. 
     Conversely, in the case where the orifice is plugged using the method for plugging the orifice according to the embodiment, the temperature of the plug portion  200   c  vicinity can be about 200° C. lower than that of laser welding. Also, solidification contraction does not occur because the material of the member does not melt. Therefore, it can be seen from  FIG. 5B  that the occurrence of defects such as voids, etc., in the plug portion  200   c  can be suppressed. 
     Example 
     The method for plugging the orifice according to the embodiment will now be described further. 
     Here, the method for plugging an orifice in the manufacture of a liquid cooling jacket is described as an example. However, the applications of the method for plugging the orifice according to the embodiment are not limited to the manufacture of liquid cooling jackets. 
       FIG. 7  is a schematic perspective view for illustrating a liquid cooling jacket. 
     The liquid cooling jacket  300  may be used to cool, for example, an IGBT (Insulated Gate Bipolar Transistor) module, etc. 
     As shown in  FIG. 7 , a main body portion  301  and connection portions  303  are provided in the liquid cooling jacket  300 . 
     The main body portion  301  has a plate configuration. The main body portion  301  is formed from a material having a high thermal conductivity. The main body portion  301  may be formed from, for example, an aluminum alloy. 
     A flow channel  302  in which a liquid flows is provided in the interior of the main body portion  301 . The liquid may be, for example, water, etc. The flow channel  302  meanders through the interior of the main body portion  301 . The two ends of the flow channel  302  have openings at a side surface of the main body portion  301 . 
     The connection portions  303  are connected respectively to the two end portions of the flow channel  302 . The connection portions  303  have tubular configurations. One end portion of the connection portion  303  is connected to the end portion of the flow channel  302 . For example, the connection portion  303  may be bonded, welded, or soldered to the end portion of the flow channel  302 . An external-thread screw may be provided in the end portion of the connection portion  303 ; an Internal-thread screw may be provided in the end portion of the flow channel  302 ; and the connection portion  303  may be screwed into the end portion of the flow channel  302 . 
       FIGS. 8A to 8C  are schematic views for illustrating a method for manufacturing a liquid cooling jacket according to a comparative example. 
     First, as shown in  FIG. 8A , a groove  302   b  that is used to form a flow channel  302   a  is formed in a base  301   a  having a plate configuration. In such a case, the groove  302   b  that has an opening at one surface of the base  301   a  is formed. The groove  302   b  meanders. The groove  302   b  may be formed using, for example, end milling, etc. Also, holes, internal-thread screws, etc., for connecting the connection portions  303  are formed in the two ends of the groove  302   b.    
     Then, as shown in  FIG. 8B , a lid  301   b  is connected to the surface of the base  301   a  where the groove  302   b  has the opening. The lid  301   b  may be bonded, welded, or soldered to the base  301   a . Also, the lid  301   b  may be fastened with screws to the base  301   a  with a sealant interposed. The space that is defined by the groove  302   b  and the lid  301   b  becomes the flow channel  302   a . The main body portion is formed by connecting the base  301   a  and the lid  301   b.    
     Continuing as shown in  FIG. 8C , the connection portions  303  are connected respectively to the two end portions of the flow channel  302   a.    
     Thus, a liquid cooling jacket that includes the flow channel  302   a  meandering through the interior of the main body portion can be manufactured. 
     However, according to the method for manufacturing the liquid cooling jacket according to the comparative example, the cross-sectional configuration of the flow channel  302   a  in a direction orthogonal to the direction in which the flow channel  302   a  extends is a quadrilateral. Therefore, the pressure loss is large at the connection portion between the connection portion  303  having the circular cross section and the flow channel  302   a  having the quadrilateral cross section. Also, there is a risk that heat transfer may be obstructed at the interface between the base  301   a  and the lid  301   b . Therefore, there is a risk that the performance of the liquid cooling jacket may be poor. Also, more complex manufacturing processes, higher manufacturing costs, etc., may be caused because the base  301   a  and the lid  301   b  are necessary. 
       FIGS. 9A to 9C  are schematic views for illustrating a method for manufacturing the liquid cooling jacket using the method for plugging the orifice according to the embodiment. 
     In the drawings of  FIGS. 9A to 9C , the drawing on the upper side is a side view; and the drawing on the lower side is a plan view. 
     First, as shown in  FIG. 9A , multiple through-holes  302   c  that are used to form the flow channel  302  are formed in the main body portion  301  having a plate configuration. In such a case, the direction in which some of the through-holes  302   c  extend crosses the direction in which the remaining through-holes  302   c  extend. In  FIG. 9A , the direction in which two through-holes  302   c  extend crosses the direction in which one through-hole  302   c  extends. The through-holes  302   c  may be formed using, for example, drilling, etc. 
     Then, as shown in  FIG. 9B , the orifices of the through-holes  302   c  are plugged using the method for plugging the orifice according to the embodiment. The flow channel  302  is formed by plugging the orifices of the through-holes  302   c . In such a case, the orifices where the connection portions  303  are connected are not plugged. Plug portions  301   c  are formed at the plugged orifices. 
     Continuing as shown in  FIG. 9C , the connection portions  303  are connected respectively to the two end portions of the flow channel  302 . 
     Thus, the liquid cooling jacket  300  that includes the flow channel  302  meandering through the interior of the main body portion  301  can be manufactured. 
     According to the method for manufacturing the liquid cooling jacket illustrated in  FIGS. 9A to 9C , the cross-sectional configuration of the flow channel  302  in a direction orthogonal to the direction in which the flow channel  302  extends is a circle. Therefore, the pressure loss at the connection portion between the connection portion  303  having the circular cross section and the flow channel  302  having the circular cross section can be reduced. The obstruction of the heat transfer can be suppressed because the main body portion  301  in which the flow channel  302  is formed has an integral structure. Therefore, the performance of the liquid cooling jacket can be improved. Also, simpler manufacturing processes, lower manufacturing costs, etc., can be realized. 
       FIGS. 10A to 10E  are schematic views for illustrating the method for manufacturing the liquid cooling jacket using the method for plugging the orifice according to the embodiment. 
       FIGS. 10A to 10E  are plan views. 
     The main body portion  301  has a plate configuration as shown in  FIG. 10A . 
     First, as shown in  FIG. 10B , the multiple through-holes  302   c  that pierce the region between mutually-opposing side surfaces of the main body portion  301  are formed. The multiple through-holes  302   c  may be formed to be parallel to each other. Three through-holes  302   c  are formed in  FIG. 10B . The through-holes  302   c  can be formed using, for example, drilling, etc. 
     Then, as shown in  FIG. 10C , holes  302   d  that extend in a direction crossing the direction in which the through-holes  302   c  extend are formed. In such a case, two through-holes  302   c  are linked by one hole  302   d . The holes  302   d  may be formed using, for example, drilling, etc. 
     Then, as shown in  FIG. 10D , the orifices of the through-holes  302   c  and the orifices of the holes  302   d  are plugged using the method for plugging the orifice according to the embodiment. The flow channel  302  is formed by plugging the orifices of the through-holes  302   c  and the orifices of the holes  302   d . In such a case, the orifices where the connection portions  303  are connected are not plugged. The plug portions  301   c  are formed at the plugged orifices. 
     Then, as shown in  FIG. 10E , the connection portions  303  are connected respectively to the two end portions of the flow channel  302 . 
     Thus, the liquid cooling jacket  300  that includes the flow channel  302  meandering through the interior of the main body portion  301  can be manufactured. 
     According to the method for manufacturing the liquid cooling jacket illustrated in  FIGS. 10A to 10E , effects similar to those of the method for manufacturing the liquid cooling jacket illustrated in  FIGS. 9A to 9C  can be obtained. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. Moreover, above-mentioned embodiments can be combined mutually and can be carried out.