Patent Publication Number: US-7594319-B2

Title: Electronic-component alignment method

Description:
RELATED APPLICATION DATA 
   This application is divisional of U.S. patent application Ser. No. 10/495,905, filed May 19, 2004, issued as U.S. Pat. No. 7,251,883 which is incorporated herein by reference to the extent permitted by law. This application claims the benefit of priority to PCT International Application No. PCT/JP03/12520, filed Sep. 30, 2003, and Japanese Patent Application Nos. JP2002-285992, filed Sep. 30, 2002 and JP2002-290369, filed Oct. 2, 2002. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to an electronic-component alignment method for aligning two electronic components with each other by using marking means formed in these electronic components and also to an apparatus therefor. 
   As shown in  FIGS. 14 and 15 , a known bonding apparatus for aligning a chip member with a plate-like or sheet-like board and then assembling therewith is formed by head-moving means  5  for driving a pressure head  4  disposed so as to be vertically movable along a guide  3  disposed on a side surface of a supporting member  2  disposed on a stand  1  in a standing manner; a pressing means  6  fixed to the head-moving means  5 , for applying a predetermined load on the pressure head  4 ; a stage  7  disposed on the stand  1  so as to face the pressure head  4 ; and a mark-recognition apparatus  8  insertably disposed between the pressure head  4  and the stage  7 . 
   The stage  7  is movable in the X and Y directions and rotatable in the θ direction by an X-axis driving source  12 , a Y-axis driving source  13 , and a θ-rotation driving source (not shown), respectively, and the head-moving means  5  is movable in the Z direction by a Z-axis driving source  14 . Also, as shown in  FIG. 16 , the mark-recognition apparatus  8  has a structure in which a camera unit  8   a  has two cameras  8   b  and  8   c  horizontally juxtaposed therein in a state in which the optical axes of pickup lenses thereof agree with each other, and a double-face reflective mirror  8   d  whose both surfaces are parallel to each other and reflective is disposed at an angle of 45 degrees and between the cameras  8   b  and  8   c  (see, for example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2000-94232 (page 4, FIG. 2))). 
   When a chip member  10  is aligned and assembled with a plate-like or sheet-like board  9  by the known bonding apparatus having the above-mentioned structure, in a state in which the head-moving means  5  and the pressure head  4  lie at the uppermost position, first the board  9  is placed on a placing portion  11  of the stage  7 , and the chip member  10  is held on the lower surface of the pressure head  4 . 
   Next, the mark-recognition apparatus  8  moves in the arrow A-direction indicated in  FIG. 15  and is inserted between the board  9  and the chip member  10 . With this arrangement, the mark-recognition apparatus  8  is ready to recognize alignment marks of the underlying board  9  and the overlying chip member  10  at the same time. 
   Then, the head-moving means  5  is lowered by driving the Z-axis driving source  14  in the above-described state and is stopped at a position where the alignment mark of the chip member  10  is clearly recognized by the mark-recognition apparatus  8 . When the two alignment marks of the board  9  and the chip member  10  are recognized by the mark-recognition apparatus  8 , control means  15  shown in  FIGS. 14 and 15  moves the stage  7  by driving the X-axis driving source  12 , the Y-axis driving source  13 , and the θ-rotation driving source (not shown) so as to bring the two alignment marks of the board  9  and the chip member  10  in agreement with each other. 
   When the two alignment marks of the board  9  and the chip member  10  are brought into agreement with each other as mentioned above, and alignment of the board  9  and the chip member  10  with each other is completed, the mark-recognition apparatus  8  is retracted in the arrow B-direction indicated in  FIG. 15 , the pressing means  6  is activated for extending a pressing shaft  6   a  so as to press the pressure head  4  down, and the chip member  10  is closely attached on, assembled with, and bonded to the board  9 . 
   However, in such a known bonding apparatus, since the alignment of the board  9  and the chip member  10  with each other is performed by the mark-recognition apparatus  8  inserted therebetween, the mark-recognition apparatus  8  requires a sufficient distance between the board  9  and the chip member  10  so as to be inserted therebetween. 
   As a result, as shown in  FIGS. 17A and 17B , even when an alignment mark  9   a  of the board  9  and an alignment mark  10   a  of the chip member  10  are accurately aligned with each other as shown in  FIG. 17A , after the alignment, the chip member  10  must be lowered a long distance in the arrow C-direction until coming into close contact with the board  9  as shown in  FIG. 17B . 
   This causes a moving error due to unsatisfactorily accuracy of a mechanism for lowering the chip member  10 , and, as shown in  FIG. 17B , sometimes causes a misalignment δ of the alignment marks  9   a  and  10   a  of the board  9  and the chip member  10  with each other. Accordingly, sometimes the board  9  and the chip member  10  are not accurately aligned with each other. 
   Also, as shown in  FIG. 16 , a recognition error Δ and so forth between two images exist due to a difference in inclinations of the optical axes of the two cameras  8   b  and  8   c  and to a non-uniform thickness of the double-face reflective mirror  8   d . Accordingly, sometimes the board  9  and the chip member  10  are not accurately aligned with each other. In order to achieve accurate alignment of, for example, 1 μm or less by correcting all these errors, an accurate correction-mechanism and a complicated mechanism-control are needed, thereby causing a risk that the apparatus becomes expensive. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an electronic-component alignment method and an apparatus therefor with which the above problems can be solved and two electronic components can be accurately aligned with each other such that a mark-recognition apparatus captures mutually corresponding alignment marking-means of the two components in the same fields of view thereof and measures the positions of the two components. 
   In order to achieve the above object, an electronic-component alignment method according to the present invention includes the steps of: holding a first electronic component with a receiving table, having two alignment holes perforated at predetermined positions thereof so as to be spaced away from each other by a predetermined interval, and holding a second electronic component with a position-adjusting mechanism, having two alignment marks formed at predetermined positions thereon so as to have an interval therebetween in agreement with that between the two aligning holes; capturing the alignment marks and the corresponding alignment holes in the same fields of view of a mark-recognition apparatus in a state in which the alignment marks of the second electronic component are introduced in the corresponding alignment holes of the first electronic component and measuring the positions of the two components; and adjusting the position of the second electronic component with the position-adjusting mechanism such that the alignment marks of the second electronic component lie at predetermined positions in the corresponding alignment holes of the first electronic component, whereby the two components are aligned with each other by performing the above steps. 
   With such a configuration, the first electronic component having the two alignment holes perforated at predetermined positions thereof so as to be spaced away from each other by a predetermined interval is held with the receiving table, and also the second electronic component having the two alignment marks formed at predetermined positions thereon so as to have an interval therebetween in agreement with that between the two alignment holes is held with the position-adjusting mechanism. Thus, in a state in which the alignment marks of the second electronic component are introduced in the corresponding alignment holes of the first electronic component, the mark-recognition apparatus captures the alignment marks and the alignment holes in the same fields of view thereof and measures the positions of the two components, and the position-adjusting mechanism adjusts the position of the second electronic component such that the alignment marks of the second electronic component lie at predetermined positions in the alignment holes of the first electronic component. 
   With this arrangement, the mark-recognition apparatus does not lie between the two electronic components to be aligned with each other, a moving distance of the second electronic component along which its position is adjusted is small, and no recognition errors of the images and the like occur since the mark-recognition apparatus captures images of the two electronic components in the same fields of view thereof and measures the positions of the two components, whereby the two components are accurately aligned with each other. 
   Also, the first and second electronic components are held such that the alignment holes and the alignment marks, respectively, of the first and second electronic components lie within the focal depth of lenses of the mark-recognition apparatus, whereby the mark-recognition apparatus focuses on both the alignment hole of the first electronic component and the corresponding alignment mark of the second electronic component so as to pick up them at the same time. 
   In addition, the position-adjusting mechanism allows the second electronic component to move and rotate in the X and Y directions and in the θ direction, respectively, on a horizontal plane, and also the entire position-adjusting mechanism is movable in the Z direction on a vertical plane, whereby the first and second electronic components are aligned with each other and are also bonded to each other. 
   Furthermore, the mark-recognition apparatus is equipped with two cameras having an interval therebetween in agreement with that between the two alignment holes of the first electronic component, whereby the positions of the two electronic components are measured at once with respect to the two alignment holes and are thus quickly aligned with each other. 
   Also, the mark-recognition apparatus is equipped with a camera laterally movable along the same distance as the interval between the two alignment holes of the first electronic component, thereby achieving a simple and compact mark-recognition apparatus. 
   In addition, the mark-recognition apparatus is equipped with two identical lenses disposed so as to have an interval therebetween in agreement with that between the two alignment holes of the first electronic component; and a camera disposed at the common position on the optical paths of the two lenses, whereby no mechanism for laterally moving the camera is needed, resulting in a simpler and more compact mark-recognition apparatus. 
   Also, an electronic-component alignment apparatus according to the present invention is equipped with a receiving table holding a first electronic component having two alignment holes perforated at predetermined positions thereof so as to be spaced away from each other by a predetermined interval; a position-adjusting mechanism holding a second electronic component which is disposed so as to face the receiving table and which has two alignment marks formed at predetermined positions thereon so as to have an interval therebetween in agreement with that between the two aligning holes; a mark-recognition apparatus which is disposed rearward of the receiving table and which, in a state in which the alignment marks of the second electronic component are introduced in the alignment holes of the first electronic component, captures the alignment marks and the corresponding alignment holes in the same fields of view thereof and measures the positions of the two components, whereby, by using images whose positions are measured by the mark-recognition apparatus, the two components are aligned with each other by adjusting the position of the second electronic component with the position-adjusting mechanism such that the alignment marks of the second electronic component lie at predetermined positions in the two alignment holes of the first electronic component. 
   With such a structure, the mark-recognition apparatus does not lie between the two electronic components to be aligned with each other, a moving distance of the second electronic component along which its position is adjusted is small, and, since images of the two electronic components are captured in the same fields of view of the mark-recognition apparatus and the positions of the two components are measured, no recognition errors of the images and the like occur, whereby the two components are accurately aligned with each other. 
   Also, the first and second electronic components are held such that the alignment holes and the alignment marks, respectively, of the first and second electronic components lie within the focal depth of lenses of the mark-recognition apparatus, whereby the mark-recognition apparatus focuses on both the alignment hole of the first electronic component and the corresponding alignment mark of the second electronic component as to pick up them at the same time. 
   Also, the position-adjusting mechanism allows the second electronic component to move and rotate in the X and Y directions and in the θ direction, respectively, on a horizontal plane, and also the entire position-adjusting mechanism is movable in the Z direction on a vertical plane, whereby the first and second electronic components are aligned with each other and are also bonded to each other. 
   Also, the mark-recognition apparatus is equipped with two cameras having an interval therebetween in agreement with that between the two alignment holes of the first electronic component, whereby the positions of the two electronic components are measured at once with respect to the two alignment holes and are thus quickly aligned with each other. 
   Also, the mark-recognition apparatus is equipped with a camera laterally movable along the same distance as the interval between the two alignment holes of the first electronic component, thereby achieving a simple and compact mark-recognition apparatus. 
   Also, the mark-recognition apparatus is equipped with two identical lenses disposed so as to have an interval therebetween in agreement with that between the two alignment holes of the first electronic component; and a camera disposed at the common position on the optical paths of the two lenses, whereby no mechanism for laterally moving the camera is needed, resulting in a simpler and more compact mark-recognition apparatus. 
   Also, in order to achieve an object of the present invention, an electronic-component alignment method according to the present invention includes the steps of: arranging a first electronic component and a second electronic component so as to face each other, the first component having a pair of alignment holes formed at predetermined positions thereof so as to be spaced away from each other by a predetermined interval, and the second component having round or polygonal alignment marks, each formed by a plurality of alignment markings having different sizes and concentrically arranged, formed so as to have an interval therebetween in agreement with that between the alignment holes; roughly adjusting the first and second electronic components by capturing the overall image of a small alignment marking of each alignment mark in the corresponding alignment hole so as to capture the overall image of a large alignment marking of the alignment mark in the corresponding alignment hole by using the small alignment marking; measuring an amount of position correction for aligning the alignment mark with the center of the corresponding alignment hole by using the large alignment marking or the large and small alignment markings; and finely adjusting the first and second electronic components so as to be aligned with each other by relatively moving the second electronic component by the amounts of position correction. 
   With such a method, of the plurality of alignment markings concentrically arranged so as to form each alignment mark of the second electronic component disposed so as to face the first electronic component, the overall image of the small alignment marking is captured in the corresponding alignment hole of the first electronic component, and the first and second electronic components are roughly aligned with each other by using the small alignment marking. Then, when the overall image of the large alignment marking of the alignment mark is captured in the corresponding alignment hole, an amount of position correction for aligning the alignment mark with the center of the corresponding alignment hole is measured by using the large alignment marking or the large and small alignment markings, and the first and second electronic components are finely adjusted so as to be aligned with each other by relatively moving the second electronic component by the amounts of position correction. Thus, lenient preliminary-alignment accuracy is allowed, and also the first and second electronic components are accurately aligned with each other. 
   Also, since the alignment mark is a concentrically formed round, edge noise of a digital image picked up by the mark-recognition apparatus is uniform regardless of the orientation of the alignment mark, thereby improving image-recognition accuracy. 
   Also, when the first electronic component is a nozzle member of a print head of an image-forming apparatus, and the second electronic component is a chip of the print head, the print head can be accurately aligned by aligning the alignment marks formed on the chip with the corresponding alignment holes formed in the nozzle members. 
   Also, when the chip is fabricated by forming a circuit on a substrate, the alignment marks are formed outside the region of the chip where the circuit is formed. Accordingly, the alignment marks can be accurately formed by using a semiconductor process. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view illustrating a method for aligning electronic components according to an embodiment of the present invention. 
       FIGS. 2A and 2B  are plan views illustrating states in which alignment holes of a first electronic component and alignment marks of a second electronic component are formed. 
       FIG. 3  is a sectional view illustrating a state in which, in a state in which the alignment marks of the second electronic component are introduced in the corresponding alignment holes of the first electronic component, a mark-recognition apparatus captures the alignment holes and the corresponding alignment marks in the same fields of view thereof and measures the positions of the two components. 
       FIG. 4  is an illustration of position-measuring pictures of marking means captured by cameras of the mark-recognition apparatus in the same fields of view thereof. 
       FIGS. 5A and 5B  are illustrations of states in which the position of the second electronic component is adjusted by using the position-measuring pictures captured by the cameras of the mark-recognition apparatus. 
       FIG. 6  is a side view of an electronic-component alignment apparatus according to an embodiment of the present embodiment. 
       FIG. 7  is a perspective view illustrating the specific structure of a position-adjusting mechanism. 
       FIG. 8  is a magnified illustration of major parts of a receiving table for receiving the first electronic component, the mark-recognition apparatus, and so forth. 
       FIG. 9  is a magnified sectional view of a major part of a mark-recognition apparatus according to another embodiment. 
       FIG. 10  is a plan view illustrating the shape of each alignment mark of the second electronic component according to another embodiment. 
       FIG. 11  is a schematic sectional view of a chip, illustrating the position where each alignment mark is formed. 
       FIG. 12  is a flowchart illustrating the process of aligning the alignment marks with the corresponding alignment holes. 
       FIGS. 13A to 13C  are illustrations of images of each alignment hole and the corresponding alignment mark recognized by the mark-recognition apparatus in the process illustrated in  FIG. 11 . 
       FIG. 14  is a side view of a known bonding apparatus. 
       FIG. 15  is an elevational view of  FIG. 14 . 
       FIG. 16  is an illustration of a mark-recognition apparatus of the known bonding apparatus. 
       FIGS. 17A and 17B  are illustrations of example misalignment between alignment marks of a board and a chip member of the known bonding apparatus. 
   

   DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be described below with reference to the attached drawings. 
     FIG. 1  is a schematic view illustrating a method for aligning electronic components according to an embodiment of the present invention. With this electronic-component alignment method, two electronic components can be accurately aligned with each other such that a mark-recognition apparatus captures mutually corresponding alignment marking-means of the two components in the same fields of view thereof and measures the positions of the two components. As shown in  FIG. 1 , the method is performed by using an apparatus having a receiving table  21  of the one electronic component, a position-adjusting mechanism  22  of the other electronic component, and a mark-recognition apparatus  23 . Meanwhile, the reference numeral  24  denotes a bonding tool for bonding the two electronic components to each other. 
   In  FIG. 1 , in the first step, a first electronic component  25  is held with the receiving table  21 , and also a second electronic component  26  is held with a position-adjusting mechanism  22 . The first electronic component  25  is, for example, a board such as a printed circuit board or a glass board, or a nozzle member used for a print head of an image-forming apparatus such as an inkjet printer, and, as shown in  FIG. 2A , is formed of a sheet-like member having two alignment holes  27   a  and  27   b  perforated at predetermined positions thereof so as to be spaced away from each other by a predetermined interval p. 
   Also, the second electronic component  26  is, for example, an individual bare chip cut out from a semiconductor wafer, an IC (hereinafter, simply referred to as chip) used for a print head of an image-forming apparatus such as an inkjet printer, or the like, and, as shown in  FIG. 2B , the chip has two alignment marks  28   a  and  28   b  formed at predetermined positions thereof so as to have a predetermined interval q therebetween in agreement with the interval p between the two alignment holes  27   a  and  27   b.    
   In  FIG. 2A , each of the alignment holes  27   a  and  27   b  is formed of a round hole having a diameter of about 50 to 60 μm. The reference numeral  29  denotes nozzles, each having a diameter of about 17 μm perforated in, for example, a nozzle member serving as the first electronic component  25 , and the nozzles  29  are formed with an example pitch of about 42 μm. Also, in  FIG. 2B , each of the alignment marks  28   a  and  28   b  is formed of a round mark having a diameter of about 20 μm. In addition, the reference numeral  30  denotes heaters, each about 20 μm in square size, formed in a printer-head chip serving as the second electronic component  26 , for example, and the heaters  30  are formed with a pitch of an about 42 μm, the same as that of the nozzles  29 . 
   The first electronic component  25  formed of the above-mentioned sheet-like member is adhered to, for example, a frame and is held with air suction through an air suction hole (not shown) formed in the receiving table  21 . In this case, as shown in  FIG. 3 , portions of the receiving table  21  for placing the first electronic component  25  thereon and holding it therewith have two see-through holes  31   a  and  31   b  formed therein so as to correspond to the two alignment holes  27   a  and  27   b  of the first electronic component  25 . 
   The see-through holes  31   a  and  31   b  are round holes having a diameter of, for example, about 400 μm so as to see through the alignment holes  27   a  and  27   b  clearly. Also, the receiving table  21  has heating means (not shown) such as a heater built therein so as to heat a portion of the first electronic component  25  coming into contact with the receiving table  21 . 
   The second electronic component  26  is held with the position-adjusting mechanism  22  having the bonding tool  24  interposed therebetween. In this case, as shown in  FIG. 3 , it is held with air-suction through an air suction hole (not shown) formed in the bonding tool  24 . 
   Thus, the bonding tool  24  moves up and down in the Z direction together with the position-adjusting mechanism  22  so as to form a chip-transfer gap r below the lower surface of the bonding tool  24 . The bonding tool  24  has heating means (not shown) such as a heater built therein so as to heat the second electronic component  26  coming into contact with the bonding tool  24 . 
   Also, the second electronic component  26  held with the bonding tool  24  has a dry-film resist  32  formed below the lower surface thereof, serving as an adhesive. Thus, portions of the dry-film resist  32  corresponding to the two alignment marks  28   a  and  28   b  of the second electronic component  26  have two see-through holes  33   a  and  33   b  formed therein. 
   As shown in  FIG. 1 , the position-adjusting mechanism  22  holding the second electronic component  26  having the bonding tool  24  interposed therebetween is designed so as to move and rotate the second electronic component  26  in the X and Y directions and in the θ direction, respectively, on a horizontal plane, and in addition, to be movable as a whole in the Z direction on a vertical plane in order to bond the first electronic component  25  and the second electronic component  26  to each other. 
   In this case, as shown in  FIG. 3 , an alignment gap s (for example, about 70 to 130 μm thick) for aligning the two electronic components is set between the upper surface of the receiving table  21  and the lower surface of the second electronic component  26 . 
   In such a state and in the subsequent step, in a state in which the alignment marks  28   a  and  28   b  of the second electronic component  26  are introduced in the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25 , the mark-recognition apparatus  23  captures the two alignment marks and the corresponding alignment holes in the same fields of view thereof and measures the positions of the two components. 
   As shown in  FIG. 3 , the mark-recognition apparatus  23  has two cameras  23   a  and  23   b  having an interval therebetween in agreement with that between the two alignment holes  27   a  and  27   b  of the first electronic component  25 . In other words, the cameras  23   a  and  23   b  are respectively disposed so as to correspond to the positions of the two see-through holes  31   a  and  31   b  formed in the receiving table  21 . Each of these cameras  23   a  and  23   b  is formed by a lens used for a coaxial incident-light illumination and having a predetermined magnification (for example, of about 9) and a video camera or a CCD camera having a predetermined pixel density (for example, of about 400,000 pixels per a quarter inch). 
   The lenses of the cameras  23   a  and  23   b  have a predetermined focal depth, and the first and second electronic components  25  and  26  are held so that the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  lie within the above focal depth. 
   With this arrangement, in a state in which the cameras  23   a  and  23   b  are placed closer to the first electronic component  25  by adjusting their heights as shown by the arrows D and E, the alignment holes  27   a  and  27   b  of the first electronic component  25  and the alignment marks  28   a  and  28   b  of the second electronic component  26  can be picked up at the same time. 
   As shown in  FIG. 4 , in this state, for example, an image lying in a state in which the one alignment mark  28   a  of the second electronic component  26  is introduced in the one alignment hole  27   a  of the first electronic component  25  is obtained in the field of view of the left camera  23   a  so as to serve as a picture  34   a  picked up by the left camera  23   a , and an image lying in a state in which the other alignment mark  28   b  of the second electronic component  26  is introduced in the other alignment hole  27   b  of the first electronic component  25  is obtained in the field of view of the right camera  23   b  so as to serve as a picture  34   b  picked up by the right camera  23   b.    
   When such pickup images are obtained, these images are subjected to image processing by an image-processing apparatus (not shown) or the like, the center positions of the alignment holes  27   a  and  27   b  and those of the alignment marks  28   a  and  28   b  are respectively recognized in the two pictures  34   a  and  34   b , and the center distance Ra between the one alignment hole  27   a  and alignment mark  28   a  and the center distance Rb between the other alignment hole  27   b  and alignment mark  28   b  are computed.  FIG. 4  illustrates a position-measuring state in which the center positions of the alignment holes  27   a  and  27   b  are misaligned with the corresponding center positions of the alignment marks  28   a  and  28   b.    
   In this state and in the following step, as shown in  FIG. 4 , the position-adjusting mechanism  22  adjusts the position of the second electronic component  26  such that the alignment marks  28   a  and  28   b  of the second electronic component  26  lie at predetermined positions in the two alignment holes  27   a  and  27   b  of the first electronic component  25 . 
   In other words, the position-adjusting mechanism  22  shown in  FIGS. 6 and 7  is activated so as to align the two components with each other by moving and rotating the second electronic component  26  held with the position-adjusting mechanism  22  having the bonding tool  24  interposed therebetween, respectively, in the X and Y directions and in the θ direction in accordance with the center distances Ra and Rb if necessary, and ideally by bringing the centers of the one alignment hole  27   a  and alignment mark  28   a  in agreement with each other and also the centers of the other alignment hole  27   b  and alignment mark  28   b  in agreement with each other. 
   Although the predetermined interval p between the two alignment holes  27   a  and  27   b  of the first electronic component  25  and the predetermined interval q between the alignment marks  28   a  and  28   b  of the second electronic component  26  are formed so as to equal to each other in  FIGS. 2A and 2B , dimensional errors take place actually in these components due to machining errors, temperature conditions, and so forth, whereby the centers of the mutually corresponding alignment holes and alignment marks are sometimes not brought into agreement with each other. In such a case, as shown in  FIG. 4 , the position of the second electronic component  26  can be adjusted such that the two alignment marks  28   a  and  28   b  are placed on a center line  35  connecting the centers between the two alignment holes  27   a  and  27   b  so as to be symmetrical with respect to each other. 
   For example,  FIG. 5A  illustrates the case where the relationship p&gt;q exists due to the above-mentioned dimensional errors. In this case, the two components can be adjusted with each other by moving the second electronic component  26  in the Y direction, rotating it in the θ direction, and also moving it in the X direction so as to make misalignments c and d lying on the center line  35  equal to each other, respectively, between the centers of the alignment hole  27   a  and the alignment mark  28   a  in the picture  34   a  picked up by the left camera  23   a  and between the centers of the alignment hole  27   b  and the alignment mark  28   b  in the picture  34   b  picked up by the right camera  23   b , and thus by adjusting the position of the second electronic component  26  such that the two alignment marks  28   a  and  28   b  are placed so as to be symmetrical with respect to each other. 
   Meanwhile,  FIG. 5B  illustrates a state in which the relationship p&lt;q exists due to the above-mentioned dimensional errors. In this case, the two components can be aligned with each other by moving the second electronic component  26  in the Y direction, rotating it in the θ direction, and also moving it in the X direction so as to make misalignments e and f lying on the center line  35  equal to each other, respectively, between the centers of the alignment hole  27   a  and the alignment mark  28   a  in the picture  34   a  picked up by the left camera  23   a  and between the centers of the alignment hole  27   b  and the alignment mark  28   b  in the picture  34   b  picked up by the right camera  23   b , and by adjusting the position of the second electronic component  26  such that the two alignment marks  28   a  and  28   b  are placed so be symmetrical with respect to each other. 
   As described above, the two electronic components  25  and  26  can be aligned with each other such that, in a state in which the alignment marks  28   a  and  28   b  of the second electronic component  26  are introduced in the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25 , the mark-recognition apparatus  23  captures the two alignment marks and the corresponding alignment holes in the same fields of view thereof and measures the positions of the two components and also such that the position-adjusting mechanism  22  adjusts the position of the second electronic component  26  so as to place the alignment marks  28   a  and  28   b  of the second electronic component  26  at predetermined positions in the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25 . 
   With this arrangement, the mark-recognition apparatus  23  does not lie between the two electronic components  25  and  26  to be aligned with each other, a moving distance of the second electronic component  26  along which its position is adjusted is small, and no recognition errors of the images and the like occur since the mark-recognition apparatus  23  captures images of the two electronic components  25  and  26  in the same fields of view thereof and measures the positions of the two components, whereby the two components are accurately aligned with each other, for example, within an accuracy of 1 μm. 
   In the meantime, the present invention is not limited to a configuration in which the position of the second electronic component is adjusted so that the two alignment marks  28   a  and  28   b  are placed so as to be symmetrical with respect to each other on the center line  35  connecting the two alignment holes  27   a  and  27   b  as shown in  FIGS. 5A and 5B , and it is also applicable to another configuration in which the two components are aligned with each other by adjusting the second component so as to be placed at another predetermined position. 
   Next, an electronic-component alignment apparatus according to the present invention related to the above-described electronic-component alignment method will be described with reference to  FIGS. 6 to 8 . With this electronic-component alignment apparatus, the two electronic components can be accurately aligned with each other such that the mark-recognition apparatus captures mutually corresponding alignment marking-means of the two components in the same fields of view thereof and measures the positions of the two components. As shown in  FIG. 6 , the alignment apparatus is formed by the receiving table  21 , the position-adjusting mechanism  22 , the mark-recognition apparatus  23 , and a stand  40 . The reference numerals  25  and  26  respectively denote first and second electronic components. 
   The stand  40  serves as a base for fixing and supporting a major part of the electronic-component alignment apparatus according to the present invention thereto and thereby and is formed by a horizontal stand member  40   a  and a vertical supporting member  40   b . The vertical supporting member  40   b  has a guide member  41  formed on one side surface thereof and extending in the vertical direction, and the guide member  41  has two moving blocks  42   a  and  42   b  disposed thereon so as to be vertically movable. The upper moving block  42   a  has an overhanging arm  43  fixed thereto and protruding horizontally. Also, the lower moving block  42   b  has a clamp press-bonding mechanism  44  fixed thereto, for bonding the two electronic components to each other. 
   As shown in  FIG. 8 , the horizontal stand member  40   a  has two longitudinal supporting beams  45  disposed at both lateral sides of the mark-recognition apparatus  23  in a standing manner; a lateral supporting beam  46  stretched over the tops of the two longitudinal supporting beams  45 ; and the receiving table  21  supported on the upper surface of the lateral supporting beam  46  having an insulating material  47  interposed therebetween. The receiving table  21  is intended to hold the first electronic component  25 , having the same structure as that shown in  FIG. 3 . Accordingly, each of the lateral supporting beam  46  and the insulating material  47  has through-holes  48   a  and  48   b  perforated therein at positions in agreement with those of the two see-through holes  31   a  and  31   b  formed in the receiving table  21 . 
   The first electronic component  25  held with the receiving table  21  is, for example, a board such as a printed circuit board or a glass board, or a nozzle member used for a print head of an image-forming apparatus such as an inkjet printer and, as shown in  FIG. 2A , is formed of a sheet-like member having the two alignment holes  27   a  and  27   b  perforated at predetermined positions thereof so as to be spaced away from each other by the predetermined interval p. 
   As shown in  FIG. 6 , the overhanging arm  43  disposed on the one side of the vertical supporting member  40   b  so as to be vertically movable, having the moving block  42   a  interposed therebetween, has the position-adjusting mechanism  22  supported below the lower surface thereof. The position-adjusting mechanism  22  is intended to hold the second electronic component  26  and disposed so as to face the receiving table  21 . 
   The second electronic component  26  is, for example, an individual bare chip cut out from a semiconductor wafer or an IC used for a print head of an image-forming apparatus such as an inkjet printer, and, as shown in  FIG. 2B , the chip has the two alignment marks  28   a  and  28   b  formed at predetermined positions thereof so as to have the predetermined interval q therebetween in agreement with the interval p between the two alignment holes  27   a  and  27   b  of the first component  25 . 
   The position-adjusting mechanism  22  is designed so as to move and rotate the second electronic component  26  in the X and Y directions and in the θ direction, respectively, on a horizontal plane, and, as shown in  FIG. 7 , has a structure in which a first plate  49   1 , a second plate  49   2 , and a third plate  49   3  are fixed every other plate so as to have a first slider  50   1  movable in the X direction, a second slider  50   2  movable in the Y direction, and a third slider  50   3  rotatable in the θ direction inserted therebetween, thereby allowing the mechanism to be movable in the X and Y directions and rotatable in the θ direction as a whole. 
   Also, since the position-adjusting mechanism  22  is supported below the lower surface of the overhanging arm  43  disposed so as to be vertically movable on the one side surface of the vertical supporting member  40   b  having the moving block  42   a  interposed therebetween, it is movable as a whole in the Z direction on a vertical plane, thereby bonding the first and second electronic components  25  and  26  to each other. 
   In this case, as shown in  FIG. 6 , the position-adjusting mechanism  22  has a tool-parallelism-adjusting mechanism  51  and the bonding tool  24  disposed below the under surface thereof, and the second electronic component  26  is held with air suction through an air suction hole (not shown) formed in the bonding tool  24 . 
   The receiving table  21  has the mark-recognition apparatus  23  disposed rearward thereof. In a state in which the alignment marks  28   a  and  28   b  of the second electronic component  26  are introduced in the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25 , this mark-recognition apparatus  23  captures the two alignment marks and the corresponding alignment holes in the same fields of view thereof and measures the positions of the components. As shown in  FIG. 8 , the two cameras  23   a  and  23   b  are disposed below the receiving table  21  and on the horizontal stand member  40   a  so as to have an interval therebetween in agreement with that between the two alignment holes  27   a  and  27   b  of the first electronic component  25 . 
   In other words, the cameras  23   a  and  23   b  are respectively disposed so as to correspond to the positions of the two see-through holes  31   a  and  31   b  formed in the receiving table  21 . Each of these cameras  23   a  and  23   b  is formed by a lens used for a coaxial incident-light illumination and having a predetermined magnification (for example, of about 9) and a video camera or a CCD camera having a predetermined pixel density (for example, of about 400,000 pixels). 
   The lenses of the cameras  23   a  and  23   b  have a predetermined focal depth and the first and second electronic components  25  and  26  are held so that the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  lie within the above focal depth. With this arrangement, in a state in which the cameras  23   a  and  23   b  are placed closer to the first electronic component  25  by adjusting their heights as shown by the arrows D and E, the alignment holes  27   a  and  27   b  of the first electronic component  25  and the alignment marks  28   a  and  28   b  of the second electronic component  26  can be picked up at the same time. 
   In the meantime, as shown in  FIG. 8 , the horizontal stand member  40   a  has position-adjusting tables disposed thereon for having the two cameras  23   a  and  23   b  mounted thereon, each formed of a combination of an X-direction slider  52   1 , a Y-direction slider  52   2 , and a Z-direction slider  52   3 . Thus, the position-adjusting tables are intended to set the initial positions of the respective cameras  23   a  and  23   b  by moving them in the X, Y and Z directions so as to capture the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25  within the fields of view thereof. Once the initial positions of the cameras  23   a  and  23   b  are set, the positions may be fixed thereafter. 
   Also, as shown in  FIG. 8 , the front surfaces of the two cameras  23   a  and  23   b  and the lateral supporting beam  46  have a predetermined gap formed therebetween and have an air duct  53  fixed in the gap and extending in the horizontal direction. The air duct  53  is intended to suck air around the cameras  23   a  and  23   b  in order to prevent fluctuation of pickup images caused by air convection due to heat around the cameras  23   a  and  23   b . The air suction of the air duct  53  allows the cameras  23   a  and  23   b  to be cooled at the same time. Meanwhile, under certain circumstances around the cameras  23   a  and  23   b , cold air may be blown from the air duct  53 . 
   Next, the way of use and an operation of the electronic-component alignment apparatus having the above-described structure will be described. Basically the electronic-component alignment apparatus operates in the same process as that of the electronic-component alignment method described with reference to  FIGS. 1 to 5B . 
   Firstly, in  FIGS. 1 and 6 , the first electronic component  25  is held with the receiving table  21 , and also the second electronic component  26  is held with the position-adjusting mechanism  22 . In this state, as shown in  FIG. 3 , it is desirable that the axial lines of the two alignment holes  27   a  and  27   b  of the first electronic component  25  extend substantially in line with those of the two alignment marks  28   a  and  28   b  of the second electronic component  26 , and the alignment marks  28   a  and  28   b  of the second electronic component  26  are introduced in the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25  so as to be seen therethrough. 
   Then, in a state in which the alignment marks  28   a  and  28   b  of the second electronic component  26  are introduced in the corresponding alignment holes  27   a  and  27   b  of the first electronic component  25 , the mark-recognition apparatus  23  captures the two alignment marks and the corresponding alignment holes in the same fields of view thereof and measures the positions of the two components. In this state, the lenses of the cameras  23   a  and  23   b  have a predetermined focal depth, and the first and second electronic components  25  and  26  are held so that the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  lie within the above focal depth. 
   As shown in  FIG. 4 , in this state, for example, an image in a state in which the one alignment mark  28   a  of the second electronic component  26  is introduced in the one alignment hole  27   a  of the first electronic component  25  is obtained in the field of view of the left camera  23   a  so as to serve as the picture  34   a  picked up by the left camera  23   a , and an image in a state in which the other alignment mark  28   b  of the second electronic component  26  is introduced in the other alignment hole  27   b  of the first electronic component  25  is obtained in the field of view of the right camera  23   b  so as to serve as the picture  34   b  picked up by the right camera  23   b.    
   When such pickup images are obtained, these images are subjected to image processing by an image-processing apparatus (not shown) or the like, the center positions of the alignment holes  27   a  and  27   b  and those of the alignment marks  28   a  and  28   b  are respectively recognized in the two pictures  34   a  and  34   b , and the center distance Ra between the one alignment hole  27   a  and alignment mark  28   a  and the center distance Rb between the other alignment hole  27   b  and alignment mark  28   b  are computed. 
     FIG. 4  illustrates the position-measuring state in which the center positions of the alignment holes  27   a  and  27   b  are misaligned with the corresponding center positions of the alignment marks  28   a  and  28   b.    
   Then, as shown in  FIG. 4 , the position-adjusting mechanism  22  adjusts the position of the second electronic component  26  such that the alignment marks  28   a  and  28   b  of the second electronic component  26  lie at predetermined positions in the two alignment holes  27   a  and  27   b  of the first electronic component  25 . 
   In other words, the position-adjusting mechanism  22  shown in  FIGS. 6 and 7  is activated so as to align the two components by moving and rotating the second electronic component  26  held with the position-adjusting mechanism  22  having the bonding tool  24  interposed therebetween in the X and Y directions and in the θ direction, respectively, in accordance with the center distances Ra and Rb if necessary, and ideally by bringing the centers of the one alignment hole  27   a  and alignment mark  28   a  in agreement with each other and also the centers of the other alignment hole  27   b  and alignment mark  28   b  in agreement with each other. 
   The remaining part of the process is the same as that of the foregoing adjustment method and will be therefore omitted. 
   In the above description, although the mark-recognition apparatus  23  is equipped with the two cameras  23   a  and  23   b  as shown in  FIGS. 1 ,  3 , and  8 , the present invention is not limited to this structure, and it may be equipped with a camera laterally movable along the same distance as the interval p between the two alignment holes  27   a  and  27   b  of the first electronic component  25 . 
   Also, as shown in  FIG. 9 , the mark-recognition apparatus  23  may have two identical lenses  54   a  and  54   b  disposed so as to have an interval therebetween in agreement with that between the two alignment holes  27   a  and  27   b  of the first electronic component  25  and a camera  55  disposed at the common position on the optical paths of the two lenses  54   a  and  54   b.    
   The two lenses  54   a  and  54   b  serve as objective lenses for capturing the two alignment holes  27   a  and  27   b  and the two alignment marks  28   a  and  28   b  (not shown) therethrough, respectively, and have the same depth of focus as each other. The camera  55  has another lens  56  serving as an image-forming lens disposed right in front thereof, and the two lenses  54   a  and  54   b  and the other lens  56  are fixed inside a bifurcated lens barrel  57  having a common root for the two lenses. 
   The first lens  54   a  and the camera  55  have a first half-mirror  58   a , a total reflection mirror  59 , and a second half-mirror  58   b  disposed on the optical path extending therebetween, the second lens  54   b  and the camera  55  have a third half-mirror  58   c  and the second half-mirror  58   b  (commonly used for both lenses  54   a  and  54   b ) disposed on the optical path extending therebetween, and the optical path between the first lens  54   a  and the camera  55  has the same length as that between the second lens  54   b  and the camera  55 . 
   Meanwhile, of the bifurcated lens barrel  57 , a lens barrel  57   a  close to the first lens  54   a  has a first illumination lamp  60   a  disposed at the bottom thereof, and a lens barrel  57   b  close to the second lens  54   b  has a second illumination lamp  60   b  disposed at the bottom thereof. Thus, the two alignment holes  27   a  and  27   b  as well as the two alignment marks  28   a  and  28   b  (not shown) can be illuminated by turning on the illumination lamps  60   a  and  60   b , respectively. 
   With this structure, the mark-recognition apparatus  23  having the above structure may be used such that when either one of the first and second illumination lamps  60   a  and  60   b  is turned on by switching over therebetween, only the first lens  54   a  captures the one alignment hole  27   a  and alignment mark  28   a  in the same field of view thereof so as to measure the positions of these hole and mark, or only the second lens  54   b  captures the other alignment hole  27   b  and alignment mark  28   b  in the same field of view so as to measure the positions of these hole and mark. 
   Alternatively, the mark-recognition apparatus may be used such that the first and second illumination lamps  60   a  and  60   b  are turned on at the same time and such that, by using an image in which left and right pictures respectively picked up through the first and second lenses  54   a  and  54   b  overlap with each other, the right and left pictures are separated from each other and are then subjected to image processing so as to measure the positions of the two alignment holes  27   a  and  27   b  and the two alignment marks  28   a  and  28   b.    
   Still alternatively, the mark-recognition apparatus may be used such that the first and second illumination lamps  60   a  and  60   b  are turned on at the same time, and left and right pictures are picked up while half the fields of view of the first and second lenses  54   a  and  54   b  are masked and such that, by using an image in which the left and right picked-up pictures overlap with each other, the right and left pictures are separated from each other and are then subjected to image processing so as to measure the positions of the two alignment holes  27   a  and  27   b  and the two alignment marks  28   a  and  28   b.    
   Although each of the two alignment holes  27   a  and  27   b  of the first electronic component  25  and the alignment marks  28   a  and  28   b  of the second electronic component  26  is two-dimensionally round in the above description as shown in  FIGS. 2B and 4 , it may have another shape as long as its position is easily measured and its center is easily detected. In addition, the first electronic component  25  and the second electronic component  26  are not limited to a board and a chip, and they may be other appropriate electronic components. 
     FIG. 10  is a plan view illustrating the shape of each alignment mark according to another embodiment. The same parts as in the above-described embodiment are denoted by the same reference numerals, and the description thereof will be omitted. 
   As shown in  FIG. 3 , each of the alignment marks  28   a  and  28   b  is formed such that two large and small circles are concentrically arranged so as to provide an outside diameter of about 30 μm and an inside diameter of about 15 μm. For example, it is provided by forming a small circle S by etching a central part of a large circle L formed of an aluminum thin film. In the meantime, of a plurality of alignment markings having different sizes and concentrically arranged so as to form a polygonal alignment mark, the large circle L represents a large alignment marking and the small circle S represents a small alignment marking. 
   To be more specific, as shown in  FIG. 11 , when a power-source wiring pattern  76 , a ground-wiring pattern  77 , and a second-layer wiring pattern of a wiring pattern  78  connecting a MOS driver-transistor  73  to the corresponding heater  30  are formed on the surface layer of a chip formed by sequentially laminating MOS (metal oxide semiconductor) transistors  72  and  73 , a first-layer wiring pattern  74 , and the heaters  30 , having an interlayer insulating film  75  interposed thereamong, on a silicon substrate  71 , each of the alignment marks  28   a  and  28   b  is formed at the same time by etching an aluminum thin film, outside the region of the chip where a circuit of the transistors and the like is formed. 
   As described above, each of the alignment marks  28   a  and  28   b  is formed so as to have a double circle having the large and small circles L and S because of the following reasons. A resolution of image processing generally has a positive correlation with the peripheral length of a recognized image. Accordingly, the large circle L having a large peripheral length has an advantage in high alignment accuracy. However, the larger the large circle L, the overall images of the large circles L of the alignment marks  28   a  and  28   b  are less likely to be captured in the corresponding alignment holes  27   a  and  27   b  at a preliminary alignment stage where the first and second electronic components  25  and  26  are placed at respectively predetermined positions, thereby leading to a disadvantage in requirement of higher accuracy for the preliminary alignment. On the other hand, although the small circle S having a small peripheral length leads to low alignment accuracy because of a low resolution of image processing, its small size leads to an advantage that the overall images of the small circles S are more likely to be captured in the corresponding alignment holes  27   a  and  27   b  at the preliminary alignment stage. Hence, the double circle is employed, taking the advantages of the large and small circles L and S into account. 
   To be more specific, for example, when each of the alignment holes  27   a  and  27   b  has a diameter of 60 μm, and each alignment mark is formed so as to have a single circle having a diameter of 20 μm, an accuracy required for the preliminary alignment is within ±20 μm with respect to each of the center distances between the alignment holes  27   a  and  27   b  and the corresponding alignment marks. Also, it is expected that an image-processing accuracy in this case is proportional to the square root of the peripheral length of each marking means, thus it is estimated that the ratio of image-processing accuracies in the above example case is 13.7 to 7.9. 
   On the other hand, when each of the alignment marks  28   a  and  28   b  according to the present invention is formed so as to have a concentric double circle with the large and small circles L and S having diameters of 30 μm and 15 μm, respectively, a preliminary-alignment accuracy is within ±22.5 μm with respect to each of the center distances between the small circles S of the alignment marks  28   a  and  28   b  and the corresponding alignment holes  27   a  and  27   b , thereby leading to a more lenient requirement for the accuracy than in the case where each of the above-mentioned alignment marks is formed so as to have a single circle. Also, since the image-processing accuracy is determined by the ratio of the square root of the peripheral length of the large circle L of each of the alignment marks  28   a  and  28   b  to that of each of the alignment holes  27   a  and  27   b , the ratio of the image-processing accuracies becomes 13.7 to 11.9, whereby the alignment accuracy between the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  is considerably improved. 
   Accordingly, by forming the alignment marks  28   a  and  28   b  so as to have a double circle, the overall images of the small circles S of the alignment marks  28   a  and  28   b  are highly likely to be captured in the corresponding alignment holes  27   a  and  27   b . Also, when the electronic components  25  and  25  are roughly adjusted by using the small circles S so that the overall images of the large circles L are captured in the alignment holes  27   a  and  27   b , and the overall images of the large circles L are resultantly captured, the alignment marks  28   a  and  28   b  are accurately aligned with the alignment holes  27   a  and  27   b  by finely adjusting the above electronic components by using the large circles L or both large and small circles L and S. 
   When both images of one of the alignment holes  27   a  and  27   b  of the first electronic component  25  and the corresponding one of the alignment marks  28   a  and  28   b  of the second electronic component  26  are recognized by the mark-recognition apparatus  23  as described above, the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  are aligned with each other in accordance with a processing procedure shown in  FIG. 12 . 
   First, in Step S 1 , images of the alignment holes  27   a  and  27   b  and the alignment marks  28   a  and  28   b  are captured by the mark-recognition apparatus  23 . Then, in Step S 2 , the small circles S of the alignment marks  28   a  and  28   b  are searched in the corresponding alignment holes  27   a  and  27   b . When the overall images of the small circles S are not found in the alignment holes  27   a  and  27   b  due to insufficient fixing accuracy of the second electronic component  26  with respect to the bonding tool  24 , fractures of the alignment marks  28   a  and  28   b , or the like, the process ends up wrong processing (in Step S 3 ) and the alignment stage ends. 
   Then, the position-adjusting mechanism  22  shown in  FIG. 1  moves up and, as shown in  FIG. 3 , forms the chip-transfer gap r below the lower surface of the bonding tool  24  so as to replace the second electronic component  26  with a new one. In the meantime, in Step S 2 , instead of being automatically searched as described above, the small circles S may be manually searched while the images thereof being visually observed in the corresponding alignment holes  27   a  and  27   b.    
   Meanwhile, when the overall images of the small circles S are recognized in Step S 2  as shown in  FIG. 13A , the process moves to Step S 4 , and amounts of position correction of the small circles S with respect to the center positions of the alignment holes  27   a  and  27   b  are measured by using the image of the small circles S. 
   Then, the second electronic component  26  is driven to move in the X or Y direction or to rotate in the θ- 0  direction by the position-adjusting mechanism  22  shown in  FIG. 1 , so that the small circles S of the alignment marks  28   a  and  28   b  are drawn in the arrow A-direction (see  FIG. 13A ) toward the centers O of the alignment holes  27   a  and  27   b . With this arrangement, the first and second electronic components  25  and  26  are roughly adjusted (see  FIG. 13B ). 
   Next, the large circles L of the alignment marks  28   a  and  28   b  are searched in Step S 5 . When the overall images of the large circles L are not recognized in this step, for example, when the images of the corresponding small circles S are recognized in Step S 2  based on false recognition of foreign particles, when misalignment between the center positions of the large and small circles L and S due to forming errors of the alignment marks  28   a  and  28   b  causes parts of the large circles L to lie behind the alignment holes  27   a  and  27   b  and to be invisible despite of the drawing operation of the small circles S in Step S 4 , and resultantly the large circles L not to be recognized as circles, or when system noise or the like causes the large circles L not to be recognized as circles, the process ends up wrong processing (in Step S 6 ), and the alignment stage ends. 
   Then, the position-adjusting mechanism  22  shown in  FIG. 1  moves up and, as shown in  FIG. 3 , forms the chip-transfer gap r below the lower surface of the bonding tool  24  so as to replace the second electronic component  26  with a new one. 
   Also, as shown in  FIG. 13B , when the overall images of the large circles L of the alignment marks  28   a  and  28   b  are recognized in Step S 5 , the process moves to Step S 7 , and it is determined whether or not each of the recognized alignment marks  28   a  and  28   b  forms a double circle. The criterion of determination about the double circle is based on whether or not the centers of the large and small circles L and S lie substantially in agreement with each other and these circles substantially form a concentric circle. When it is determined in Step S 7  that each of the recognized alignment marks does not form a double circle, in other words, when the center positions of the large and small circles L and S are misaligned with each other due to forming errors of the alignment marks  28   a  and  28   b  as described above, the process ends up wrong processing (in Step S 8 ), the alignment stage ends, and the second electronic component  26  is replaced with a new one in the same fashion as described previously. 
   On the other hand, when it is determined in Step S 7  that each of the recognized alignment marks  28   a  and  28   b  forms a double circle, the process moves to Step S 9 , and the center distances between the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  are measured so as to compute amounts of position correction. For example, the amounts of position correction are measured on the basis of the large circles L of the alignment marks  28   a  and  28   b  or are provided as the mean values of respective amounts of correction measured on the basis of the large and small circles L and S of the alignment marks or as amounts of correction obtained by computing the ratio of the size of the large circle L to that of the small circle S and by weighting the respective amounts of correction in accordance with the computed ratio. 
   When the amounts of position correction are measured, the second electronic component  26  is driven to move in the X or Y direction or to rotate in the θ direction by the position-adjusting mechanism  22 , so that the alignment marks  28   a  and  28   b  are respectively drawn in the arrow B-direction (see  FIG. 13B ) toward the centers O of the alignment holes  27   a  and  27   b.    
   With this arrangement, the first and second electronic components  25  and  26  are finely adjusted such that the center positions of the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  are aligned with each other (see  FIG. 13C ). Meanwhile, when the intervals p and q, respectively, between the alignment holes  27   a  and  27   b  and between the alignment marks  28   a  and  28   b  shown in  FIGS. 2A and 2B  are not equal to each other due to a forming error of each marking means, a difference in thermal expansion of the two electronic components, or the like, the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  are aligned with each other so as to be symmetrical with respect to each other on the center line connecting the alignment holes  27   a  and  27   b.    
   When fine adjustment for aligning the first and second electronic components  25  and  26  with each other is finished as described above, the process moves to Step S 10 , and it is determined whether or not misalignments of the center positions between the alignment holes  27   a  and  27   b  and the corresponding alignment marks  28   a  and  28   b  are within a specified value. When the misalignment between the alignment hole and the corresponding mark is within the specified value, the alignment is finished (in Step S 11 ). When, the misalignment between the alignment hole and the alignment mark is out of the specified value, the alignment is performed by repeating Steps S 1  to S 10 . 
   When the alignment is finished in accordance with the above-described processing procedure, the position-adjusting mechanism  22  shown in  FIG. 1  moves down slowly, and the first and second electronic components  25  and  26  are assembled with each other. Then, heating means formed in the receiving table  21  and the bonding tool  24  are heated so as to bond the first and second electronic components  25  and  26  to each other, having the dry-film resist  32  disposed on the bonding surface of the second electronic component  26  interposed therebetween. 
   In accordance with the above-described electronic-component alignment method, since each of the alignment marks  28   a  and  28   b  is formed so as to have a double circle with large and small circles, at the preliminary alignment stage of the first and second electronic components  25  and  26 , the overall images of the small circles S of the alignment marks  28   a  and  28   b  are easily captured in the alignment holes  27   a  and  27   b , respectively, thereby leading to lenient preliminary-alignment accuracy. Accordingly, when amounts of position correction are measured by using the small circles S captured in the alignment holes  27   a  and  27   b , and the alignment marks  28   a  and  28   b  are roughly adjusted with respect to the corresponding alignment holes  27   a  and  27   b , the overall images of the large circles L of the alignment marks  28   a  and  28   b  can be easily drawn in the alignment holes  27   a  and  27   b , respectively. With this arrangement, when the amounts of position correction for aligning the alignment marks  28   a  and  28   b  with the centers of the alignment holes  27   a  and  27   b  are measured by using the large circles L or both large and small circles L and S, and the alignment marks  28   a  and  28   b  are finely adjusted with respect to the alignment holes  27   a  and  27   b , the first and second electronic components  25  and  26  can be accurately aligned with each other. 
   Also, since each of the alignment marks  28   a  and  28   b  is formed so as to have a double circle, even when foreign particles are falsely recognized as the small circles S, the false recognition can be corrected as long as the corresponding large circles L are not found outside the corresponding small circles S, thereby improving the recognition accuracy of each alignment mark. 
   In the meantime, each of the alignment marks  28   a  and  28   b  is not limited to a double circle, and it may be formed of three or more concentrically arranged circles. Also, each of the alignment holes  27   a  and  27   b  and the alignment marks  28   a  and  28   b  are not limited to a round shape, and it may have a rectangular shape, a triangular shape, or the like. Nevertheless, it is preferable that each marking means have a round shape since edge noise of a digital image picked up by the mark-recognition apparatus  23  is uniform regardless of its orientation. 
   INDUSTRIAL APPLICABILITY 
   The present invention is applicable to, for example, a bonding apparatus for aligning and assembling a chip member with a plate-like or sheet-like board.