Patent Publication Number: US-2022225507-A1

Title: Chip resistor, method of producing chip resisitor and chip resistor packaging structure

Description:
TECHNICAL FIELD 
     The present invention relates to a chip resistor, a method for manufacturing a chip resistor, and a mount structure of a chip resistor. 
     BACKGROUND ART 
     A conventionally known chip resistor (surface mount resistor) includes two leads and a central resistor portion. The central resistor portion is sandwiched between the two leads and bonded to the leads. This type of chip resistor is manufactured by using a plurality of reels. Specifically, a strip of a resistive material is wound around one of the reels, whereas a strip of an electrically conductive material is wound around each of other two reels. The strips are paid out from the reels while rotating the reels, and bonded together in such a manner that the strip of the resistive material is sandwiched between the two strips of an electrically conductive material. The strips bonded together are cut successively. 
     TECHNICAL REFERENCE 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent No. 3321724 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The present invention has been conceived under the above-described circumstances. It is therefore an object of the present invention to provide a method for efficiently manufacturing a chip resistor. 
     Means for Solving the Problems 
     According to a first aspect of the present invention, there is provided a chip resistor manufacturing method comprising the steps of: preparing at least three conductive elongated boards made of an electrically conductive material and a resistive member made of a resistive material; arranging the at least three conductive elongated boards apart from each other along a width direction crossing a longitudinal direction in which one of the at least three conductive elongated boards is elongated; forming a resistor aggregate by bonding the resistive member to the at least three conductive elongated boards; and collectively dividing the resistor aggregate into a plurality of chip resistors by punching so that each of the chip resistors includes two electrodes and a resistor portion bonded to the two electrodes. 
     Preferably, the step of forming a resistor aggregate uses welding. 
     Preferably, the step of forming a resistor aggregate uses high energy beam welding. 
     Preferably, the step of forming a resistor aggregate uses electron beam welding or laser beam welding as the high energy beam welding. 
     Preferably, the method further comprises the step of bending one of the at least three conductive elongated boards. 
     Preferably, the bending step is performed at the same time as the collectively dividing step. 
     Preferably, one of the at least three conductive elongated boards has a thickness smaller than the thickness of the resistive member. 
     Preferably, the resistive member includes a plurality of resistive elongated boards, and the step of forming a resistor aggregate comprises bonding each of the resistive elongated boards to two of the at least three conductive elongated boards. 
     Preferably, the step of forming a resistor aggregate comprises arranging each of the resistive elongated boards between adjacent two of the at least three conductive elongated boards. 
     Preferably, the step of forming a resistor aggregate comprises arranging each of the resistive elongated boards at a position overlapping adjacent two of the at least three conductive elongated boards as viewed in the thickness direction perpendicular to both of the longitudinal direction and the width direction. 
     According to a second aspect of the present invention, there is provided a chip resistor comprising: a first electrode; a second electrode spaced apart from the first electrode in a first direction; and a resistor portion bonded to the first electrode and the second electrode. The resistor portion extends along a plane spreading in the first direction and a second direction crossing the first direction. The first electrode includes a first side surface facing in the first direction, a second side surface facing in the second direction, and a curved surface connected to both the first side surface and the second side surface. 
     Preferably, the chip resistor further comprises a first intermediate layer connected to the first electrode and the resistor portion, and a second intermediate layer connected to the second electrode and the resistor portion. The first intermediate layer and the second intermediate layer are made of a same material. 
     Preferably, the resistor portion is sandwiched between the first electrode and the second electrode. 
     Preferably, the first intermediate layer includes a wide portion and a narrow portion. The wide portion is exposed to a third direction crossing both of the first direction and the second direction. The dimension of the narrow portion in the first direction is smaller than the dimension of the wide portion in the first direction. 
     Preferably, the first electrode and the second electrode are on a same side of the resistor portion. 
     Preferably, the first side surface includes a linear trace formed surface formed with a linear trace, and a breakage trace formed surface connected to the linear trace formed surface and formed with a breakage trace. 
     Preferably, the first electrode includes a plate-like portion extending along the first direction and the second direction and an inclined portion inclined with respect to the plate-like portion and closer to the resistor portion than the plate-like portion is. 
     Preferably, the resistor portion has a thickness smaller than the thickness of the first electrode. 
     According to a third aspect of the present invention, there is provided a chip resistor manufacturing method comprising the steps of: preparing two conductive elongated boards made of an electrically conductive material and a resistive elongated board made of a resistive material; arranging the resistive elongated board between the two conductive elongated boards; bonding each of the two conductive elongated boards to the resistive elongated board; and cutting, by shearing, the two conductive elongated boards and the resistive elongated board along a width direction crossing a longitudinal direction in which one of the two conductive elongated boards is elongated. 
     Preferably, the method further comprises the step of bending each of the conductive elongated boards. 
     Preferably, the bending step is performed at the same time as the cutting step. 
     Preferably, the bonding step uses welding. 
     Preferably, the bonding step uses high energy beam welding. 
     Preferably, the bonding step uses electron beam welding or laser beam welding as the high energy beam welding. 
     Preferably, the method further comprises the step of fixing each of the two conductive elongated boards to the resistive elongated board before the bonding step. The bonding step comprises performing welding, with each of the two conductive elongated boards fixed to the resistive elongated board. 
     Preferably, the fixing step comprises sandwiching the two conductive elongated boards and the resistive elongated board by a first clamping tool and a second clamping tool. The sandwiching step comprises pressing one of the two conductive elongated boards against the resistive elongated board by the first clamping tool and pressing the other one of the two conductive elongated boards against the resistive elongated board by the second clamping tool. 
     Preferably, the arranging step comprises placing the two conductive elongated boards and the resistive elongated board on a base. The fixing step comprises pressing the two conductive elongated boards and the resistive elongated board placed on the base against the base by a pressing tool. The pressing tool is formed with two elongated holes extending in one direction. The step of pressing against the base comprises arranging one of the two elongated holes to overlap a portion where one of the two conductive elongated boards and the resistive elongated board are in contact with each other and arranging the other one of the two elongated holes to overlap a portion where the other one of the two conductive elongated boards and the resistive elongated board are in contact with each other. The bonding step comprises directing high energy beam so as to pass through each of elongated holes. 
     According to a fourth aspect of the present invention, there is provided a chip resistor comprising: a first electrode; a second electrode spaced apart from the first electrode in a first direction; and a resistor portion bonded to the first electrode and the second electrode. The first electrode includes a front surface and a reverse surface which face away from each other. The resistor portion extends along a plane spreading in the first direction and a second direction crossing the first direction. The first electrode includes a first electrode side surface facing to a first side in the second direction and a second electrode side surface facing to a second side in the second direction. The first electrode side surface includes a first electrode linear trace formed surface formed with a linear trace, and a first electrode breakage trace formed surface connected to the first electrode linear trace formed surface and formed with a breakage trace. The first electrode linear trace formed surface is closer to the front surface than the first electrode breakage trace formed surface is. 
     Preferably, the second electrode side surface includes a second electrode linear trace formed surface formed with a linear trace, and a second electrode breakage trace formed surface connected to the second electrode linear trace formed surface and formed with a breakage trace. The second electrode linear trace formed surface is closer to the reverse surface than the second electrode breakage trace formed surface is. 
     Preferably, the resistor portion includes a resistor portion front surface and a resistor portion reverse surface which face away from each other, a first resistor portion side surface facing to a first side in the second direction, and a second resistor portion side surface facing to a second side in the second direction. The resistor portion front surface faces to the same direction as the front surface. The first resistor portion linear trace formed surface is closer to the resistor portion front surface than the first resistor portion breakage trace formed surface is. 
     Preferably, the second resistor portion side surface includes a second resistor portion linear trace formed surface formed with a linear trace, and a second resistor portion breakage trace formed surface connected to the second resistor portion linear trace formed surface and formed with a breakage trace. The second resistor portion linear trace formed surface is closer to the resistor portion reverse surface than the second resistor portion breakage trace formed surface is. 
     Preferably, the first resistor portion breakage trace formed surface has a width larger than the width of the first electrode breakage trace formed surface. 
     Preferably, the first electrode linear trace formed surface has a width that increases as proceeding further away from the resistor portion. 
     Preferably, the chip resistor further comprises a first intermediate layer connected to the first electrode and the resistor portion, and a second intermediate layer connected to the second electrode and the resistor portion. The first intermediate layer and the second intermediate layer are made of a same material. 
     Preferably, the resistor portion is sandwiched between the first electrode and the second electrode. 
     Preferably, the first intermediate layer includes a wide portion and a narrow portion. The wide portion is exposed to a third direction crossing both of the first direction and the second direction. The dimension of the narrow portion in the first direction is smaller than the dimension of the wide portion in the first direction. 
     Preferably, the first electrode includes a plate-like portion extending along the first direction and the second direction and an inclined portion inclined with respect to the plate-like portion and closer to the resistor portion than the plate-like portion is. 
     According to a fifth aspect of the present invention, there is provided a chip resistor mount structure comprising a chip resistor provided according to the second or the fourth aspect of the present invention, a mount board, and a solder layer between the mount board and the chip resistor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a mount structure of a chip resistor according to a first embodiment of the present invention; 
         FIG. 2  is a sectional view taken along lines II-II in  FIG. 1 ; 
         FIG. 3  is a sectional view taken along lines in  FIG. 1 ; 
         FIG. 4  is a plan view of amount structure of the chip resistor shown in  FIG. 1 ; 
         FIG. 5  is a view (partially omitted) along lines V-V in  FIG. 1 ; 
         FIG. 6  is a front view of the chip resistor shown in  FIG. 1 ; 
         FIG. 7  is a partially enlarged sectional view taken along lines VII-VII in  FIG. 6 ; 
         FIG. 8  is a plan view showing a step of a method for manufacturing the chip resistor according to the first embodiment of the present invention; 
         FIG. 9  is a partial sectional view taken along lines IX-IX in  FIG. 8 ; 
         FIG. 10  is a plan view showing a step of a method for manufacturing the chip resistor according to the first embodiment of the present invention; 
         FIG. 11  is a partial sectional view taken along lines XI-XI in  FIG. 10 ; 
         FIG. 12  is a plan view showing a step of a method for manufacturing the chip resistor according to the first embodiment of the present invention; 
         FIG. 13  is a partial sectional view taken along lines XIII-XIII in  FIG. 12 ; 
         FIG. 14  is a plan view showing the step subsequent to the step of  FIG. 12 ; 
         FIG. 15  is a partial sectional view taken along lines XV-XV in  FIG. 14 ; 
         FIG. 16  is a partial sectional view showing the step subsequent to the step of  FIG. 15 ; 
         FIG. 17  is a plan view of a step of a variation of a method for manufacturing the chip resistor according to the first embodiment of the present invention; 
         FIG. 18  is a sectional view taken along lines XVIII-XVIII in  FIG. 17 ; 
         FIG. 19  is a sectional view of a mount structure of a chip resistor according to a second embodiment of the present invention; 
         FIG. 20  is a sectional view taken along lines XX-XX in  FIG. 19 ; 
         FIG. 21  is a sectional view taken along lines XXI-XXI in  FIG. 19 ; 
         FIG. 22  is a plan view of the chip resistor mount structure shown in  FIG. 19 ; 
         FIG. 23  is a view (partially omitted) along lines XXIII-XXIII in  FIG. 19 ; 
         FIG. 24  is a sectional view of a mount structure of a chip resistor according to a third embodiment of the present invention; 
         FIG. 25  is a plan view of the chip resistor mount structure shown in  FIG. 24 ; 
         FIG. 26  is a view (partially omitted) along lines XXVI-XXVI in  FIG. 24 ; 
         FIG. 27  is a plan view showing a step of a method for manufacturing the chip resistor according to the third embodiment of the present invention; 
         FIG. 28  is a partial sectional view taken along lines XXVIII-XXVIII in  FIG. 27 ; 
         FIG. 29  is a sectional view of a mount structure of a chip resistor according to a fourth embodiment of the present invention; 
         FIG. 30  is a sectional view taken along lines XXX-XXX in  FIG. 29 ; 
         FIG. 31  is a sectional view taken along lines XXXI-XXXI in  FIG. 29 ; 
         FIG. 32  is a plan view of the chip resistor mount structure shown in  FIG. 29 ; 
         FIG. 33  is a view (partially omitted) along lines XXXIII-XXXIII in  FIG. 29 ; 
         FIG. 34  is a front view of the chip resistor shown in  FIG. 29 ; 
         FIG. 35  is a rear view of the chip resistor shown in  FIG. 29 ; 
         FIG. 36  is a perspective view showing a step of a method for manufacturing the chip resistor according to the fourth embodiment of the present invention; 
         FIG. 37  is a plan view of  FIG. 36 ; 
         FIG. 38  is a sectional view taken along lines XXXVIII-XXXVIII in  FIG. 37 ; 
         FIG. 39  is a perspective view showing the step subsequent to the step of  FIG. 36 ; 
         FIG. 40  is a plan view showing the step subsequent to the step of  FIG. 39 ; 
         FIG. 41  is a sectional view taken along lines XLI-XLI in  FIG. 40 ; 
         FIG. 42  is a sectional view showing the step subsequent to the step of  FIGS. 40 and 41 ; 
         FIG. 43  is a sectional view showing the step subsequent to the step of  FIG. 42 ; 
         FIG. 44  is a sectional view taken along lines XLIV-XLIV in  FIG. 43 ; 
         FIG. 45  is a sectional view showing the step subsequent to the step of  FIG. 44 ; 
         FIG. 46  is a sectional view of a mount structure of a chip resistor according to a fifth embodiment of the present invention; 
         FIG. 47  is a perspective view showing a step of a method for manufacturing the chip resistor according to the fifth embodiment of the present invention; 
         FIG. 48  is a plan view showing the step subsequent to the step of  FIG. 47 ; and 
         FIG. 49  is a sectional view taken along lines XLIX-XLIX in  FIG. 48 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     A first embodiment of the present invention is described below with reference to  FIGS. 1-18 . 
       FIG. 1  is a sectional view of a mount structure of a chip resistor according to this embodiment.  FIG. 2  is a sectional view taken along lines II-II in  FIG. 1 .  FIG. 3  is a sectional view taken along lines III-III in  FIG. 1 .  FIG. 4  is a plan view of a mount structure of the chip resistor shown in  FIG. 1 .  FIG. 5  is a view (partially omitted) along lines V-V in  FIG. 1 . 
     The chip resistor mount structure  800  shown in these figures includes a chip resistor  101 , a mount board  801  and a solder layer  802 . 
     For instance, the mount board  801  is a printed circuit board. For instance, the mount board  801  includes an insulating substrate and a pattern electrode (not shown) formed on the insulating substrate. The chip resistor  101  is mounted on the mount board  801 . The solder layer  802  is between the chip resistor  101  and the mount board  801 . The solder layer  802  bonds the chip resistor  101  and the mount board  801  to each other. 
       FIG. 6  is a front view of the chip resistor shown in  FIG. 1 . 
     The chip resistor  101  includes a first electrode  1 , a second electrode  2 , a resistor portion  3 , a first intermediate layer  4  and a second intermediate layer  5 . 
     The first electrode  1  is made of an electrically conductive material. Examples of the electrically conductive material include Cu, Ni and Fe. When the chip resistor  101  is mounted on the mount board  801 , the first electrode  1  is bonded to the solder layer  802 . The first electrode  1  is electrically connected to the pattern electrode (not shown) of the mount board  801  via the solder layer  802 . In this embodiment, the first electrode  1  includes a plate-like portion  181  and an inclined portion  182 . 
     The plate-like portion  181  extends along the X-Y plane. The plate-like portion  181  constitutes the most part of the first electrode  1 . The inclined portion  182  is inclined with respect to the X-Y plane. Specifically, the inclined portion  182  is inclined to be deviated toward the direction Z 1  as proceeding further away from the plate-like portion  181 . The inclined portion  182  is in the form of a strip extending along the direction Y. The inclined portion  182  is connected to the plate-like portion  181 . 
     The first electrode  1  includes a front surface  11 , a reverse surface  12 , two side surfaces  13  (first side surfaces), a side surface  14  (second side surface), and two curved surfaces  15 . 
     The front surface  11  faces to the direction Z 1 , whereas the reverse surface  12  faces to the direction Z 2 . Each of the side surfaces  13 ,  14  and the curved surfaces  15  face to a direction perpendicular to the direction Z. Specifically, the side surfaces  13  face to the direction Y and the side surface  14  faces to the direction X. The curved surfaces  15  are connected to the side surfaces  13  and the side surface  14 . 
       FIG. 7  is a partially enlarged sectional view taken along lines VII-VII in  FIG. 6 . 
     The side surface  13  includes a linear trace formed surface  131  and a breakage trace formed surface  132 . The linear trace formed surface  131  is formed with a linear trace. The linear trace comprises a plurality of thin linear grooves extending in the direction Z. The breakage trace formed surface  132  is connected to the linear trace formed surface  131 . The breakage trace formed surface  132  is formed with a breakage trace. The breakage trace is an irregular trace formed when a metal is torn off. As shown in  FIG. 6 , in this embodiment, the linear trace formed surface  131  is closer to the reverse surface  12  than the breakage trace formed surface  132  is. When the chip resistor  101  is mounted on a mount board  801 , the linear trace formed surface  131  is covered by the solder layer  802 . According to this arrangement, solder moves along the thin grooves of the linear trace formed surface  131 , whereby a relatively large area of the side surface  13  is covered by the solder layer  802 . Unlike this embodiment, the breakage trace formed surface  132  may be closer to the reverse surface  12  than the linear trace formed surface  131  is. 
     As shown in  FIG. 6 , similarly to the side surfaces  13 , the side surface  14  has a linear trace formed surface  141  and a breakage trace formed surface  142 . Since the linear trace formed surface  141  and the breakage trace formed surface  142  of the side surface  14  are similar to the linear trace formed surface  131  and the breakage trace formed surface  132  of the side surfaces  13 , the explanation is omitted. 
     The structure of the second electrode  2  is similar to that of the first electrode  1 , which is as follows. 
     The second electrode  2  is made of an electrically conductive material. Examples of the electrically conductive material include Cu, Ni and Fe. When the chip resistor  101  is mounted on the mount board  801 , the second electrode  2  is bonded to the solder layer  802 . The second electrode  2  is electrically connected to the pattern electrode (not shown) of the mount board  801  via the solder layer  802 . In this embodiment, the second electrode  2  includes a plate-like portion  281  and an inclined portion  282 . 
     The plate-like portion  281  extends along the X-Y plane. The plate-like portion  281  constitutes the most part of the second electrode  2 . The inclined portion  282  is inclined with respect to the X-Y plane. Specifically, the inclined portion  282  is inclined to be deviated toward the direction Z 1  as proceeding further away from the plate-like portion  281 . The inclined portion  282  is in the form of a strip extending along the direction Y. The inclined portion  282  is connected to the plate-like portion  281 . 
     The second electrode  2  includes a front surface  21 , a reverse surface  22 , two side surfaces  23 , a side surface  24  and two curved surfaces  25 . 
     The front surface  21  faces to the direction Z 1 , whereas the reverse surface  22  faces to the direction Z 2 . Each of the side surfaces  23 ,  24  and the curved surfaces  25  face to a direction perpendicular to the direction Z. Specifically, the side surfaces  23  face to the direction Y and the side surface  24  faces to the direction X. The curved surfaces  25  are connected to the side surfaces  23  and the side surface  24 . 
     As shown in  FIG. 6 , the side surface  23  includes a linear trace formed surface  231  and a breakage trace formed surface  232 . Since the linear trace formed surface  231  and the breakage trace formed surface  232  of the side surface  23  are similar to the linear trace formed surface  131  and the breakage trace formed surface  132  of the side surface  13 , the explanation is omitted. 
     As shown in  FIG. 6 , similarly to the side surfaces  23 , the side surface  24  has a linear trace formed surface  241  and a breakage trace formed surface  242 . Since the linear trace formed surface  241  and the breakage trace formed surface  242  of the side surface  24  are similar to the linear trace formed surface  231  and the breakage trace formed surface  232  of the side surfaces  23 , the explanation is omitted. 
     The resistor portion  3  is made of a resistive material. Examples of the resistive material include an alloy of Cu and Mn, an alloy of Ni and Cr, an alloy of Ni and Cu, and an alloy of Fe and Cr. An alloy of Cu and Mn is relatively soft, whereas an alloy of Ni and Cr, an alloy of Ni and Cu, and an alloy of Fe and Cr are relatively hard. The resistance of the resistive material forming the resistor portion  3  is higher than the resistance of the electrically conductive material forming the first electrode  1  or the second electrode  2 . The resistor portion  3  is connected to first electrode  1  and the second electrode  2 . In this embodiment, the resistor portion  3  is sandwiched between the first electrode  1  and the second electrode  2 . 
     In this embodiment, the inclined portion  182  is closer to the resistor portion  3  than the plate-like portion  181  is. Similarly, the inclined portion  282  is closer to the resistor portion  3  than the plate-like portion  281  is. 
     The resistor portion  3  includes a resistor portion front surface  31 , a resistor portion reverse surface  32  and two resistor portion side surfaces  33 . 
     The resistor portion front surface  31  faces to the same direction as the front surface  11  or the front surface  21  (i.e., the direction Z 1 ). The resistor portion reverse surface  32  faces to the opposite direction from the resistor portion front surface  31 . The resistor portion reverse surface  32  faces to the same direction as the reverse surface  12  or the reverse surface  22  (i.e., the direction Z 2 ). At least part of the reverse surface  12  and at least part of the reverse surface  22  are deviated from the resistor portion reverse surface  32  toward the side to which the resistor portion reverse surface  32  faces (i.e., the direction Z 2 ). 
     Each of the resistor portion side surfaces  33 , which are shown in e.g.  FIGS. 4 and 6 , faces to the direction (direction Y) that crosses the direction in which the first electrode  1  and the second electrode  2  are spaced apart from each other. As shown in  FIG. 6 , each resistor portion side surface  33  includes a linear trace formed surface  331  and a breakage trace formed surface  332 . Since the linear trace formed surface  331  and the breakage trace formed surface  332  are similar to the linear trace formed surface  131  and the breakage trace formed surface  132 , respectively, the explanation is omitted. 
     As shown in  FIG. 1 , the first intermediate layer  4  is between the first electrode  1  and the resistor portion  3 . The first intermediate layer  4  is connected to the first electrode  1  and the resistor portion  3 . In this embodiment, the first intermediate layer  4  is formed when a high energy beam is directed to the first electrode  1  or the resistor portion  3  to bond the first electrode  1  and the resistor portion  3 . Thus, the first intermediate layer  4  is made of a mixture of the material forming the first electrode  1  and the material forming the resistor portion  3 . 
     The first intermediate layer  4  includes a wide portion  43  and a narrow portion  44 . The wide portion  43  is exposed to the direction Z 2 . The narrow portion  44  is on the direction Z 1  side of the wide portion  43 . The dimension of the narrow portion  44  in the direction X is smaller than the dimension of the wide portion  43  in the direction X. For instance, the dimension of the wide portion  43  in the direction X is 1-1.5 mm, whereas the dimension of the narrow portion  44  in the direction X is 0.5-1 mm. The wide portion  43  may have burr (not shown) on the surface. 
     Similarly to the first intermediate layer  4 , the second intermediate layer  5  is between the second electrode  2  and the resistor portion  3 . The second intermediate layer  5  is connected to the second electrode  2  and the resistor portion  3 . In this embodiment, the second intermediate layer  5  is formed when a high energy beam is directed to the second electrode  2  or the resistor portion  3  to bond the second electrode  2  and the resistor portion  3 . Thus, the second intermediate layer  5  is made of a mixture of the material forming the second electrode  2  and the material forming the resistor portion  3 . Thus, the second intermediate layer  5  and the first intermediate layer  4  are made of the same material. 
     The second intermediate layer  5  includes a wide portion  53  and a narrow portion  54 . The wide portion  53  is exposed to the direction Z 2 . The narrow portion  54  is on the direction Z 1  side of the wide portion  53 . The dimension of the narrow portion  54  in the direction X is smaller than the dimension of the wide portion  53  in the direction X. For instance, the dimension of the wide portion  53  in the direction X is 1-1.5 mm, whereas the dimension of the narrow portion  54  in the direction X is 0.5-1 mm. The wide portion  53  may have burr (not shown) on the surface. 
     A method for manufacturing the chip resistor  101  is described below. 
     First, as shown in  FIGS. 8 and 9 , an electrically conductive member  701  is prepared. The electrically conductive member  701  is a lead frame in this embodiment and includes at least three conductive elongated boards  711 . In the illustrated example, the electrically conductive member  701  includes six conductive elongated boards  711 . The conductive elongated boards  711  are elongated in one direction. In the electrically conductive member  701 , the conductive elongated boards  711  are spaced apart from each other in the width direction crossing the longitudinal direction of one of the conductive elongated boards  711 . As shown in  FIG. 9 , each conductive elongated board  711  is in the form of an elongated rectangle in cross section. In this embodiment, at least three conductive elongated boards  711  spaced apart from each other are provided by forming the electrically conductive member  701 . 
     Similarly, as shown in  FIGS. 10 and 11 , a resistive member  702  is prepared. In this embodiment, the resistive member  702  is a resistive frame and includes a plurality of resistive elongated boards  721 . In this embodiment, the resistive member  702  includes five resistive elongated boards  721 . The resistive elongated boards  721  are elongated in one direction. In the resistive member  702 , the resistive elongated boards  721  are spaced apart from each other in the width direction crossing the longitudinal direction of the resistive elongated boards  721 . As shown in  FIG. 11 , each resistive elongated board  721  is in the form of an elongated rectangle in cross section. In  FIG. 10 , the resistive member  702  is hatched for easier understanding. This holds true for the subsequent plan views. Unlike this embodiment, the resistive member  702  may be a single flat plate large enough to cover collectively all the conductive elongated boards  711  as viewed in plan. 
     Then, as shown in  FIGS. 12 and 13 , a resistor aggregate  703  is formed. To form a resistor aggregate  703 , the resistive member  702  is bonded to at least three conductive elongated boards  711  of the electrically conductive member  701 . In this embodiment, each of the resistive elongated boards  721  is bonded to adjacent two of at least three conductive elongated boards  711 . In this process, each of the resistive elongated boards  721  is arranged between adjacent two of at least three conductive elongated boards  711 . 
     As a technique for bonding the resistive member  702  to the conductive elongated boards  711 , welding may be employed. Preferably, as the welding technique, high energy beam welding may be employed. Examples of the high energy beam welding include electron beam welding and laser beam welding. In the case where high energy beam welding is employed, as shown in  FIG. 13 , high energy beam  881  (electron beam or laser beam) is directed to the conductive elongated boards  711  or the resistive elongated boards  721  along the direction Z 1 , for example. By receiving energy of the high energy beam  881 , the conductive elongated boards  711  or the resistive elongated boards  721  melt, whereby the conductive elongated boards  711  and the resistive elongated boards  721  are bonded to each other. Unlike this embodiment, the conductive elongated boards  711  and the resistive member  702  may be bonded by brazing or soldering using solder or silver paste. Alternatively, the conductive elongated boards  711  and the resistive member  702  may be bonded by ultrasonic joining. 
     Then, as shown in  FIGS. 14-16 , the resistor aggregate  703  is collectively divided into a plurality of chip resistors  101 . In  FIG. 14 , each of the regions of the resistor aggregate  703  which are to become chip resistors  101  is indicated by a double-dashed line. For instance, about 40 chip resistors  101  are obtained from a single resistor aggregate  703 . To divide the resistor aggregate  703  into a plurality of chip resistors  101 , two punching dies  831 ,  832  (see  FIG. 15 ) of a size corresponding to the plurality of chip resistors as viewed in plan are used. By pressing the resistor aggregate  703  between the punching die  831  and the punching die  832 , the resistor aggregate  703  is punched. By punching the resistor aggregate  703 , the curved surfaces  15  of the first electrode  1  or the curved surfaces  25  of the second electrode  2  may be formed. 
     As shown in  FIG. 16 , at the same time as the step of punching the resistor aggregate  703  is performed, the step of bending the conductive elongated boards  711  is performed. In this embodiment, each conductive elongated board  711  is bent so that portions of the first electrode  1  and the second electrode  2  which are relatively close to the resistor portion  3  are shifted toward the direction Z 1 , or the direction in which the high energy beam  881  travels, from a portion of the first electrode  1  or the second electrode  2  which is relatively far from the resistor portion  3 . In this way, a plurality of chip resistors  101  are manufactured. 
     The advantages of the above-noted embodiment are described below. 
     According to the embodiment, the resistor aggregate  703  is formed by bonding the resistive member  702  to at least three conductive elongated boards  711 . With this arrangement, the number of chip resistors  101  obtained per unit length in the direction Y shown in  FIG. 14  increases. In this embodiment, the resistor aggregate  703  is collectively divided by punching into a plurality of chip resistor  101 . Thus, it is not necessary to successively cut chip resistors  101 . This enhances the manufacturing efficiency of the chip resistors  101 . Thus, the method according to this embodiment is suitable for efficiently manufacturing the chip resistor  101 . 
     Since the chip resistor  101  is manufactured by punching, the dimensional accuracy of the chip resistor  101  as viewed in plan is determined by the dimensional accuracy of the punching dies  831 ,  832 . Accordingly, the dimensional accuracy of the resistor portion  3  of the chip resistor  101  in the direction Y is also determined by the dimensional accuracy of the punching dies  831 ,  832 . Thus, according to the method of this embodiment, by selecting punching dies  831 ,  832  of a desired dimensional accuracy before punching the resistor aggregate  703 , the dimensional error in the direction Y of the resistor portions is reduced as compared with the conventional method of successively cutting the strips. When the dimensional error in the direction Y of the resistor portions  3  is reduced, a larger number of resistor portions  3  having a desired resistance are obtained, whereby a larger number of chip resistors  101  having a desired resistance are obtained. When the chip resistor  101  has a desired resistance, the trimming process for adjusting the resistance of the chip resistor  101  does not need to be performed. In this way, the number of chip resistors  101  which require trimming process reduces. This leads to enhancement of the manufacturing efficiency of the chip resistor  101 . 
     In this embodiment, a lead frame is used as the electrically conductive member  701 , and a resistive frame is used as the resistive member  702 . Thus, it is not necessary to individually hold a plurality of conductive elongated boards  711  or a plurality of resistive elongated boards  721 , which facilitates handling. 
     Unlike the conventional method for manufacturing a chip resistor, this embodiment does not use a reel. Thus, the work of winding a strip of a resistive material or electrically conductive material around a reel is not necessary. Thus, the use of a large apparatus for winding a strip around a reel is also unnecessary. Since pulling the strip out of the reel is not necessary, the use of a large apparatus for pulling the strip out of the reel is also unnecessary. 
     When a reel is used to manufacture a chip resistor, the entire production line is stopped if a trouble happens at some point of a strip. Since this embodiment does not use a reel, such a problem does not occur. 
     When electron beam is used as high energy beam  881  to bond the conductive elongated boards  711  and the resistive elongated boards  721  to each other, the conductive elongated boards  711  and the resistive elongated boards  721  need to be placed in a vacuum chamber. In this embodiment, the dimension of each conductive elongated board  711  or resistive elongated board  721  in the direction Y is about 100 mm. Thus, such a work as cutting the conductive elongated boards  711  or resistive elongated boards  721  for housing in a vacuum chamber is not necessary. Thus, the method of this embodiment is suitable for efficiently manufacturing the chip resistors  101 . 
     In this embodiment, the high energy beam  881  is directed along the direction Z 1 . According to this arrangement, the energy of the high energy beam is absorbed relatively easily by portions on the direction Z 2  side of the conductive elongated board  711  and the resistive elongated board  721 , so that these portions melt relatively easily. As a result, the wide portion  43  exposed to the direction Z 2  is formed in the first intermediate layer  4  of the chip resistor  101 . Burrs may be formed on the surface of the wide portion  43 . In this embodiment, each of the conductive elongated board  711  is bent so that the portion of the first electrode  1  or the second electrode  2  which is close to the resistor portion  3  is deviated toward the direction Z 1  side from the portion of the first electrode  1  or the second electrode  2  which is distant from the resistor portion  3 . According to this arrangement, even when burrs are formed on the surface of the wide portion  43 , the burrs are in the recessed portion of the chip resistor  101  and not on the direction z 1  side of the chip resistor  101 . Thus, when the chip resistor  101  is held by a holder (not shown) for movement, the holder does not come into contact with the burrs. This allows the chip resistor  101  to be moved stably. 
     Unlike this embodiment, the lead frame may not be used. As shown in  FIGS. 17 and 18 , as the electrically conductive member  701 , a plurality of conductive elongated boards  711  separate from each other may be placed on a pallet  882 . Similarly, as the resistive member  702 , the resistive frame may not be used. As shown in  FIGS. 17 and 18 , resistive elongated boards  721  may be placed between the conductive elongated boards  711  on the pallet  882 . Then, after the conductive elongated boards  711  and the resistive elongated boards  721  are placed on the pallet  882 , the conductive elongated boards  711  and the resistive elongated boards  721  are bonded to each other. 
     Other embodiments of the present invention are described below. In the figures referred to in these embodiments, the elements that are identical or similar to those of the foregoing embodiment are designated by the same reference signs as those used for the foregoing embodiment. 
     The second embodiment of the present invention is described below. 
       FIG. 19  is a sectional view of a chip resistor mount structure of this embodiment.  FIG. 20  is a sectional view taken along lines XX-XX in  FIG. 19 .  FIG. 21  is a sectional view taken along lines XXI-XXI in  FIG. 19 .  FIG. 22  is a plan view of the chip resistor mount structure shown in  FIG. 19 .  FIG. 23  is a view (partially omitted) along the XXIII-XXIII in  FIG. 19 . 
     The chip resistor  102  shown in these figures differs from the chip resistor  101  mainly in that the thicknesses (dimension in the direction Z) of the first electrode  1  and the second electrode  2  are larger than the thickness (dimension in the direction Z) of the resistor portion  3 . The first electrode  1  and the second electrode  2  of the chip resistor  102  are in the form of a plane extending along X-Y plane. Neither the first electrode  1  nor the second electrode  2  includes an inclined portion. 
     The method for manufacturing the chip resistor  102  is the same as the method for manufacturing the chip resistor  101  except that the thickness of the conductive elongated boards  711  (see  FIG. 9 ) of the electrically conductive member  701  is larger than the thickness of the resistive elongated boards  721  (see FIG.  11 ) of the resistive member  702 . Thus, the explanation is omitted. In the method for manufacturing the chip resistor  102 , the step of bending the conductive elongated boards  711  is not performed. 
     For the same reasons as those described in the first embodiment, the chip resistor  102  of this embodiment is also suitable for enhancing the manufacturing efficiency. 
     In manufacturing the chip resistor  102  of this embodiment, a lead frame is used as the electrically conductive member  701 , and a resistive frame is used as the resistive member  702 . Thus, it is not necessary to individually hold a plurality of conductive elongated boards  711  or a plurality of resistive elongated boards  721 , which facilitates handling. 
     Unlike the conventional method for manufacturing a chip resistor, this embodiment does not use a reel. Thus, the work of winding a strip of a resistive material or electrically conductive material around a reel is not necessary. Thus, the use of a large apparatus for winding a strip around a reel is also unnecessary. Since pulling the strip out of the reel is not necessary, the use of a large apparatus for pulling the strip out of the reel is also unnecessary. 
     When a reel is used to manufacture a chip resistor, the entire production line is stopped if a trouble happens at some point of a strip. Since this embodiment does not use a reel, such a problem does not occur. 
     In manufacturing the chip resistor  102  of this embodiment, such a work as cutting the conductive elongated boards  711  or resistive elongated boards  721  for housing in a vacuum chamber is not necessary. Thus, the method of this embodiment is suitable for efficiently manufacturing the chip resistors  102 . 
     The third embodiment of the present invention is described below. 
       FIG. 24  is a sectional view of a mount structure of the chip resistor according to this embodiment.  FIG. 25  is a plan view of the chip resistor mount structure shown in  FIG. 24 .  FIG. 26  is a view (partially omitted) along lines XXVI-XXVI in  FIG. 24 . 
     The chip resistor  103  shown in these figures differs from the chip resistor  102  of the second embodiment in that the first electrode  1  and the second electrode  2  are on the same side of the resistor portion  3 . Since other structures are the same, the description is omitted. 
     A method for manufacturing the chip resistor  103  is described below. 
     First, an electrically conductive member  701  and a resistive member  702  are prepared, in the same manner as that described with reference to  FIGS. 8-11 . 
     Then, as shown in  FIGS. 27 and 28 , a resistor aggregate  703  is formed. To form a resistor aggregate  703 , the resistive member  702  is bonded to at least three conductive elongated boards  711  of the electrically conductive member  701 . In this embodiment, each of a plurality of resistive elongated boards  721  is bonded to adjacent two of at least three conductive elongated boards  711 . In this process, each of the resistive elongated boards  721  is arranged to overlap both of the adjacent two of the at least three conductive elongated boards  711  as viewed in the direction Z. 
     After the resistor aggregate  703  is formed, the above-described step of punching the resistor aggregate  703  is performed, whereby the chip resistor  103  is obtained. In the method for manufacturing the chip resistor  103  as well, the step of bending the conductive elongated boards  711  is not performed. 
     For the same reasons as those described in the first embodiment, the chip resistor  102  of this embodiment is also suitable for enhancing the manufacturing efficiency. 
     In manufacturing the chip resistor  103  of this embodiment, a lead frame is used as the electrically conductive member  701 , and a resistive frame is used as the resistive member  702 . Thus, it is not necessary to individually hold a plurality of conductive elongated boards  711  or a plurality of resistive elongated boards  721 , which facilitates handling. 
     Unlike the conventional method for manufacturing a chip resistor, this embodiment does not use a reel. Thus, the work of winding a strip of a resistive material or electrically conductive material around a reel is not necessary. Thus, the use of a large apparatus for winding a strip around a reel is also unnecessary. Since pulling the strip out of the reel is not necessary, the use of a large apparatus for pulling the strip out of the reel is also unnecessary. 
     When a reel is used to manufacture a chip resistor, the entire production line is stopped if a trouble happens at some point of a strip. Since this embodiment does not use a reel, such a problem does not occur. 
     In manufacturing the chip resistor  103  of this embodiment, such a work as cutting the conductive elongated boards  711  or resistive elongated boards  721  for housing in a vacuum chamber is not necessary. Thus, the method of this embodiment is suitable for efficiently manufacturing the chip resistors  103 . 
     When current flows through the chip resistor  103 , the portion of the resistor portion  3  which overlaps the gap between the first electrode  1  and the second electrode  2  as viewed in plan (viewed in the direction Z) functions as a resistor. Thus, the resistance of the chip resistor  103  is determined by the distance between the first electrode  1  and the second electrode  2 . Thus, by adjusting the distance between the first electrode  1  and the second electrode  2  in the state of the resistor aggregate  703 , the resistance of the chip resistor  103  is finely adjusted to a desired value. Fine adjustment of the resistance of the chip resistor  103  leads to reduction of the number of chip resistors  101  that require the trimming process. This is suitable for enhancing the manufacturing efficiency of the chip resistor  103 . 
     A fourth embodiment of the present invention is described below. 
       FIG. 29  is a sectional view of a mount structure of the chip resistor according to the fourth embodiment of the present invention.  FIG. 30  is a sectional view taken along lines XXX-XXX in  FIG. 29 .  FIG. 31  is a sectional view taken along lines XXXI-XXXI in  FIG. 29 .  FIG. 32  is a plan view of the chip resistor mount structure shown in  FIG. 29 .  FIG. 33  is a view (partially omitted) along lines XXXIII-XXXIII in  FIG. 29 . 
     The chip resistor mount structure  805  shown in these figures includes a chip resistor  201 , a mount board  801  and a solder layer  802 . 
     For instance, the mount board  801  is a printed circuit board. For instance, the mount board  801  includes an insulating substrate and a pattern electrode (not shown) formed on the insulating substrate. The chip resistor  301  is mounted on the mount board  801 . The solder layer  802  is between the chip resistor  201  and the mount board  801 . The solder layer  802  bonds the chip resistor  201  and the mount board  801  to each other. 
     The chip resistor  201  includes a first electrode  1 , a second electrode  2 , a resistor portion  3 , a first intermediate layer  4  and a second intermediate layer  5 . 
     As shown in  FIGS. 32 and 33 , the first electrode  1  includes a front surface  11 , a reverse surface  12 , a side surface  13   a  (first electrode side surface), a side surface  13   b  (second electrode side surface) and a side surfaces  14 . 
     The front surface  11  and the reverse surface  12  face away from each other. Specifically, the front surface  11  faces to the direction Z 1 , whereas the reverse surface  12  faces to the direction Z 2 . The side surface  13   a  faces to one side in the direction Y, whereas the side surface  13   b  faces to the other side in the direction Y. The side surface  14  faces to the direction X. Unlike the chip resistor  101 , the first electrode  1  of this embodiment does not have a curved surface  15 . Thus, the side surface  14  is directly connected to the side surface  13   a  and the side surface  13   b.    
       FIG. 34  is a front view of the chip resistor shown in  FIG. 29 .  FIG. 35  is a rear view of the chip resistor shown in  FIG. 29 . 
     As shown in  FIG. 34 , the side surface  13   a  includes a linear trace formed surface  131   a  (first electrode linear trace formed surface) and a breakage trace formed surface  132   a  (first electrode breakage trace formed surface). The breakage trace formed surface  132   a  is connected to the linear trace formed surface  131   a . Since the shapes of the linear trace formed surface  131   a  and the breakage trace formed surface  132   a  are the same as those of the linear trace formed surface  131  and the breakage trace formed surface  132  of the chip resistor  101 , the description of these is omitted. 
     In this embodiment, the linear trace formed surface  131   a  is closer to the front surface  11  than the breakage trace formed surface  132   a  is. In this embodiment, the width (dimension in the direction Z) of the linear trace formed surface  131   a  increases as proceeding further away from the resistor portion  3 . The linear trace formed surface  131   a  is connected to the front surface  11 . The breakage trace formed surface  132   a  is connected to the reverse surface  12 . 
     As shown in  FIG. 35 , the side surface  13   b  includes a linear trace formed surface  131   b  (second electrode linear trace formed surface) and a breakage trace formed surface  132   b  (second electrode breakage trace formed surface). The breakage trace formed surface  132   b  is connected to the linear trace formed surface  131   b . Since the shapes of the linear trace formed surface  131   b  and the breakage trace formed surface  132   b  are the same as those of the linear trace formed surface  131  and the breakage trace formed surface  132  of the chip resistor  101 , description of these is omitted. 
     In this embodiment, the linear trace formed surface  131   b  is closer to the reverse surface  12  than the breakage trace formed surface  132   b  is. That is, the vertical positional relationship between the breakage trace formed surface and the linear trace formed surface in the side surface  13   a  is opposite from that in the side surface  13   b . The linear trace formed surface  131   b  is connected to the reverse surface  12 . The breakage trace formed surface  132   b  is connected to the front surface  11 . In this embodiment, the width (dimension in the direction Z) of the linear trace formed surface  131   b  increases as proceeding further away from the resistor portion  3 . 
     The side surface  14  may include the linear trace formed surface  141  and the breakage trace formed surface  142  similarly to the chip resistor  101  or may be a flat surface. The shape or structure of the side surface  14  is determined by how the conductive elongated boards  711 , which is described later, are made. 
     Except the points described above, the first electrode  1  has the same structure as that of the first electrode  1  of the chip resistor  101 . Description of the same points is omitted. 
     As shown in  FIGS. 32 and 33 , the second electrode  2  includes a front surface  21 , a reverse surface  22  and side surfaces  23   a ,  23   b ,  24   b.    
     The front surface  21  and the reverse surface  22  face away from each other. Specifically, the front surface  21  faces to the direction Z 1 , whereas the reverse surface  22  faces to the direction Z 2 . The side surface  23   a  faces to one side in the direction Y, whereas the side surface  23   b  faces to the other side in the direction Y. The side surface  24  faces to the direction X. Unlike the chip resistor  101 , the second electrode  2  of this embodiment does not have a curved surface  25 . Thus, the side surface  24  is directly connected to the side surface  23   a  and the side surface  23   b.    
     As shown in  FIG. 34 , the side surface  23   a  includes a linear trace formed surface  231   a  and a breakage trace formed surface  232   a . The breakage trace formed surface  232   a  is connected to the linear trace formed surface  231   a . Since the shapes of the linear trace formed surface  231   a  and the breakage trace formed surface  232   a  are the same as those of the linear trace formed surface  131  and the breakage trace formed surface  132  of the chip resistor  101 , description of these is omitted. 
     In this embodiment, the linear trace formed surface  231   a  is closer to the front surface  21  than the breakage trace formed surface  232   a  is. In this embodiment, the width (dimension in the direction Z) of the linear trace formed surface  231   a  increases as proceeding further away from the resistor portion  3 . The linear trace formed surface  231   a  is connected to the front surface  21 . The breakage trace formed surface  232   a  is connected to the reverse surface  22 . 
     As shown in  FIG. 35 , the side surface  23   b  includes a linear trace formed surface  231   b  and a breakage trace formed surface  232   b . The breakage trace formed surface  232   b  is connected to the linear trace formed surface  231   b . Since the shapes of the linear trace formed surface  231   b  and the breakage trace formed surface  232   b  are the same as those of the linear trace formed surface  131  and the breakage trace formed surface  132  of the chip resistor  101 , description of these is omitted. 
     In this embodiment, the linear trace formed surface  231   b  is closer to the reverse surface  22  than the breakage trace formed surface  232   b  is. That is, the vertical positional relationship between the breakage trace formed surface and the linear trace formed surface in the side surface  23   a  is opposite from that in the side surface  23   b . The linear trace formed surface  231   b  is connected to the reverse surface  22 . The breakage trace formed surface  232   b  is connected to the front surface  21 . In this embodiment, the width (dimension in the direction Z) of the linear trace formed surface  231   b  increases as proceeding further away from the resistor portion  3 . 
     The side surface  24  may include the linear trace formed surface  241  and the breakage trace formed surface  242  similarly to the chip resistor  101  or may be a flat surface. The shape or structure of the side surface  24  is determined by how the conductive elongated boards  711  are made. 
     Except the points described above, the second electrode  2  has the same structure as that of the second electrode  2  of the chip resistor  101 . Description of the same points is omitted. 
     As shown in  FIGS. 32 and 33 , the resistor portion  3  includes a resistor portion front surface  31 , a resistor portion reverse surface  32 , a resistor portion side surface  33   a  (first resistor portion side surface) and a resistor portion side surface  33   b  (second resistor portion side surface). 
     The resistor portion front surface  31  faces to the same direction as the front surface  11  or the front surface  21  (i.e., the direction Z 1 ). The resistor portion reverse surface  32  faces to the opposite direction from the resistor portion front surface  31 . The resistor portion reverse surface  32  faces to the same direction as the reverse surface  12  or the reverse surface  22  (i.e., the direction Z 2 ). At least part of the reverse surface  12  and at least part of the reverse surface  22  are deviated from the resistor portion reverse surface  32  toward the side to which the resistor portion reverse surface  32  faces (i.e., the direction Z 2 ). 
     The resistor portion side surface  33   a  shown in e.g.  FIG. 32  faces to a first side in the direction Y. As shown in  FIG. 34 , the resistor portion side surface  33   a  includes a linear trace formed surface  331   a  (first resistor portion linear trace formed surface) and a breakage trace formed surface  332   a  (first resistor portion breakage trace formed surface). The breakage trace formed surface  332   a  is connected to the linear trace formed surface  331   a . Since the shapes of the linear trace formed surface  331   a  and the breakage trace formed surface  332   a  are the same as those of the linear trace formed surface  131  and the breakage trace formed surface  132  of the chip resistor  101 , description of these is omitted. 
     As shown in  FIG. 34 , in this embodiment again, the linear trace formed surface  331   a  is closer to the resistor portion front surface  31  than the breakage trace formed surface  332   a  is. The linear trace formed surface  331   a  is connected to the resistor portion front surface  31 . The breakage trace formed surface  332   a  is connected to the resistor portion reverse surface  32 . When the material forming the first electrode  1  or the second electrode  2  is harder than the material forming the resistor portion  3 , the width of the breakage trace formed surface  332   a  may become larger than the width of the breakage trace formed surface  132   a  and the width of the breakage trace formed surface  232   a , as shown in  FIG. 34 . 
     The resistor portion side surface  33   b  shown in e.g.  FIG. 32  faces to a second side in the direction Y. The resistor portion side surface  33   b  is connected to the side surface  13   b  of the first electrode  1  and the side surface  23   b  of the second electrode  2 . As shown in  FIG. 35 , the resistor portion side surface  33   b  includes a linear trace formed surface  331   b  (second resistor portion linear trace formed surface) and a breakage trace formed surface  332   b  (second resistor portion breakage trace formed surface). The breakage trace formed surface  332   b  is connected to the linear trace formed surface  331   b . Since the shapes of the linear trace formed surface  331   b  and the breakage trace formed surface  332   b  are the same as those of the linear trace formed surface  131  and the breakage trace formed surface  132  of the chip resistor  101 , description of these is omitted. 
     In this embodiment, the linear trace formed surface  331   b  is closer to the resistor portion reverse surface  32  than the breakage trace formed surface  332   b  is. That is, the vertical positional relationship of the breakage trace formed surface and the linear trace formed surface in the resistor portion side surface  33   a  is opposite from that in the resistor portion side surface  33   b . The linear trace formed surface  331   b  is connected to the resistor portion reverse surface  32 . The breakage trace formed surface  332   b  is connected to the resistor portion front surface  31 . 
     Except the points described above, the resistor portion  3  has the same structure as that of the resistor portion  3  of the chip resistor  101 . Description of the same points is omitted. 
     A method for manufacturing the chip resistor  201  is described below. 
     First, as shown in  FIGS. 0.36 and 38 , two conductive elongated boards  711  and a resistive elongated board  721  are prepared. The conductive elongated boards  711  are made of an electrically conductive material. The resistive elongated board  721  is made of a resistive material. In this embodiment, the two conductive elongated boards  711  have the same width (dimension in the width direction). 
     Then, the resistive elongated board  721  is to be placed between the two conductive elongated boards  711 . In this embodiment, the resistive elongated board  721  is arranged between the two conductive elongated boards  711  as these boards are placed on a base  870  (see  FIG. 38 ). 
     Then, the two conductive elongated boards  711  are fixed to the resistive elongated board  721 . In this embodiment, a first clamping tool  871  and a second clamping tool  872  are used to fix the two conductive elongated boards  711  to the resistive elongated board  721 . Specifically, the two conductive elongated boards  711  and the resistive elongated board  721  are sandwiched by the first clamping tool  871  and the second clamping tool  872 . One of the two conductive elongated boards  711  is pressed against the resistive elongated board  721  by the first clamping tool  871 , and the other one of the two conductive elongated boards  711  is pressed against the resistive elongated board  721  by the second clamping tool  872 . 
     As shown in  FIGS. 39-41 , in this embodiment, the two conductive elongated boards  711  and the resistive elongated board  721  placed on the base  870  are pressed against the base  870  by a pressing tool  875 . This prevents the two conductive elongated boards  711  and the resistive elongated board  721  from rising from the base  870 . In  FIG. 40 , the pressing tool  875  is hatched for easier understanding. The pressing tool  875  has two elongated holes  875   a  and  875   b . Each of the elongated holes  875   a  and  875   b  is elongated in one direction. In this embodiment, the elongated holes  875   a  and  875   b  are rectangular as viewed in plan. As shown in  FIG. 40 , in pressing the two conductive elongated boards  711  and the resistive elongated board  721  against the base  870  by the pressing tool  875 , the elongated hole  875   a  is arranged to overlap the portion  891  where one of the two conductive elongated boards  711  and the resistive elongated board  721  are in contact with each other. Similarly, in pressing the two conductive elongated boards  711  and the resistive elongated board  721  against the base  870  by the pressing tool  875 , the elongated hole  875   b  is arranged to overlap the portion  892  where the other one of the two conductive elongated boards  711  and the resistive elongated board  721  are in contact with each other. 
     Then, as shown in  FIGS. 40 and 41 , a resistor aggregate  703  is formed. To form the resistor aggregate  703 , the two conductive elongated boards  711  are bonded to the resistive elongated board  721 . As a technique for bonding the conductive elongated boards  711  to the resistive member  721 , welding may be employed. Preferably, as the welding technique, high energy beam welding may be employed. Examples of the high energy beam welding include electron beam welding and laser beam welding. In the case where high energy beam welding is employed, as shown in  FIG. 41 , high energy beam  881  (electron beam or laser beam) is directed to the conductive elongated boards  711  or the resistive elongated boards  721  along the direction Z 1 , for example. In this embodiment, the high energy beam  881  is directed in such a manner as to pass through the elongated holes  875   a ,  875   b . By receiving energy of the high energy beam  881 , the conductive elongated boards  711  or the resistive elongated board  721  melt, whereby the conductive elongated boards  711  and the resistive elongated boards  721  are bonded together. 
     Unlike this embodiment, the conductive elongated boards  711  and the resistive members  721  may be bonded together by brazing or soldering using solder or silver paste. Alternatively, the conductive elongated boards  711  and the resistive member  721  may be bonded together by ultrasonic joining. 
     Then, as shown in  FIGS. 42 and 43 , the resistor aggregate  703  is cut by shearing. The resistor aggregate  703  is cut along the double-dashed lines shown in  FIG. 40 . That is, the two conductive elongated boards  711  and the resistive elongated board  721  are cut by shearing along the width direction crossing the longitudinal direction of one of the two conductive elongated boards  711 . In this embodiment, the resistor aggregate  703  is successively cut from an end. 
     To cut the resistor aggregate  703 , a die member  841  and a die member  843  are used. As shown in  FIG. 42 , when the die member  841  is moved down, the die member  841  and the die member  843  cut into the conductive elongated boards  711  and the resistive elongated board  721 . (Although only the resistive elongated board  721  is shown in  FIG. 42 , the same happens to the conductive elongated board  711  as well). In this process, the die member  841  and the die member  843  form linear traces in the conductive elongated boards  711  and the resistive elongated board  721 . The formation of linear traces in the conductive elongated board  711  by the die member  843  provides the above-described linear trace formed surfaces  131   a ,  231   a . The formation of linear traces in the resistive elongated board  721  by the die member  843  provides the above-described linear trace formed surface  331   a . The formation of linear traces in the conductive elongated board  711  by the die member  841  provides the above-described linear trace formed surfaces  131   b ,  231   b . The formation of linear traces in the resistive elongated board  721  by the die member  841  provides the above-described linear trace formed surface  331   b.    
     When the die member  841  is further moved down as shown in  FIG. 43 , the shear load exerted on the conductive elongated board  711  and the resistive elongated board  721  increases. Thus, breakage occurs in the conductive elongated board  711  and the resistive elongated board  721 , whereby the conductive elongated board  711  and the resistive elongated board  721  are cut off. In this process, breakage traces are formed in the conductive elongated board  711  and the resistive elongated board  721 . The formation of breakage traces in the conductive elongated board  711  or the resistive elongated board  721  provides the above-described breakage trace formed surfaces. 
     In this embodiment, at the same time as the step of cutting the resistor aggregate  703  (the step of cutting the conductive elongated board  711  and the resistive elongated board  721  by shearing), the step of bending each conductive elongated board  711  is performed. That is, as shown in  FIGS. 42-45 , in performing shearing by the die member  841  and the die member  843 , the conductive elongated board  711  and the resistive elongated board  721  are sandwiched by the die member  841  and the die member  842 . As shown in  FIG. 44 , the die member  841  is formed with a projection  841   a , whereas the die member  842  is formed with a recess  842   a . Thus, when the conductive elongated boards  711  and the resistive elongated board  721  are sandwiched by the die member  841  and the die member  842 , the conductive elongated boards  711  are bent so that a part of the chip resistor  201  projects downward in FIG.  44 . Since the projection  841   a  is pressed against the resistive elongated board  721 , the resistive elongated board  721  may be sheared prior to the conductive elongated boards  711 . In this way, a single chip resistor  201  shown in  FIG. 29  is obtained. 
     By repeating the process steps similar to those described with reference to  FIGS. 42-45 , a plurality of chip resistors  201  are obtained from the resistor aggregate  703 . 
     Unlike this embodiment, the step of cutting the resistor aggregate  703  (the step of cutting the conductive elongated boards  711  and the resistive elongated board  721  by shearing) and the step of bending the conductive elongated boards  711  may not be performed at the same time. For instance, the conductive elongated boards  711  may be bent before the step of cutting the resistor aggregate  703  (the step of cutting the conductive elongated boards  711  and the resistive elongated board  721  by shearing). 
     The advantages of this embodiment are described below. 
     In this embodiment, two conductive elongated boards  711  and the resistive elongated board  721  are cut by shearing. Unlike the case where the conductive elongated board  711  and the resistive elongated board  721  are cut by dicing, the method of this embodiment does not leave shavings. Thus, relatively large portions of the conductive elongated board  711  and resistive elongated board  721  are used for the chip resistor  201 . In other words, the portions of the conductive elongated board  711  and resistive elongated board  721  which are wasted, i.e., not used for the chip resistor  201 , are reduced. The conductive elongated board  711  and the resistive elongated board  721  are efficiently used for making chip resistors  201 . 
     In this embodiment, the step of bending the conductive elongated boards  711  is performed at the same time as the step of cutting the conductive elongated boards  711  and the resistive elongated board  721 . This shortens the time required for manufacturing the chip resistor  201 . 
     In this embodiment, the two conductive elongated boards  711  are fixed to the resistive elongated board  721  before the two conductive elongated boards  711  and the resistive elongated board  721  are bonded to each other. In the step of bonding the two conductive elongated boards  711  and the resistive elongated board  721 , welding is performed, with the conductive elongated boards  711  fixed to the resistive elongated board  721 . With this arrangement, in bonding the conductive elongated boards  711  and the resistive elongated board  721 , the conductive elongated boards  711  and the resistive elongated board  721  are prevented from moving. Thus, the conductive elongated boards  711  and the resistive elongated board  721  are reliably bonded to each other. 
     According to this embodiment, the elongated hole  875   a  is arranged to overlap the portion  891  where one of the two conductive elongated boards  711  and the resistive elongated board  721  are in contact with each other, and the elongated hole  875   b  is arranged to overlap the portion  892  where the other one of the two conductive elongated boards  711  and the resistive elongated board  721  are in contact with each other. The high energy beam  881  is directed so as to pass through the elongated holes  875   a  and  875   b . With this arrangement, the high energy beam  881  is reliably directed to the portion  891  and the portion  892 , with the conductive elongated boards  711  and the resistive elongated board  721  prevented from rising from the base  870 . Thus, the high energy beam  881  is reliably directed to desired portions. 
     A fifth embodiment of the present invention is described below. 
       FIG. 46  a sectional view of a mount structure of a chip resistor according to the fifth embodiment of the present invention. 
     The chip resistor  202  shown in this figure differs from the chip resistor  201  in that the thickness of the resistor portion  3  is different from the thickness of the first electrode  1  or the second electrode  2 . In this embodiment, the thickness of the resistor portion  3  is larger than that of the first electrode  1  or the second electrode  2 . The thickness of the resistor portion  3  may be smaller than that of the first electrode  1  or the second electrode  2 . 
     To manufacture the chip resistor  202 , a pressing tool having a structure different from that of the pressing tool  875  is used to press the two conductive elongated boards  711  and the resistive elongated board  721  against the base  870 . Except this point, the chip resistor  202  is manufactured in the same way as the chip resistor  201 . However, the thickness of the resistive elongated board  721  is larger than that of the conductive elongated boards  711 . 
     As shown in  FIGS. 47-49 , the pressing tool  875  includes a resistor pressing member  876  and conductor pressing members  877  and  878 . In  FIG. 48 , the pressing tool  875  is hatched for easier understanding. The resistor pressing member  876  and the conductor pressing members  877  and  878  are separately prepared. The resistor pressing member  876  presses the resistive elongated board  721  against the base  870 . The conductor pressing member  877  presses one of the two conductive elongated boards  711  against the base  870 . The conductor pressing member  878  presses the other one of the two conductive elongated boards  711  against the base  870 . In this embodiment, an elongated hole  875   a  is defined between the conductor pressing member  877  and the resistor pressing member  876 , and an elongated hole  875   b  is defined between the conductor pressing member  878  and the resistor pressing member  876 . In this embodiment again, high energy beam  881  is directed to pass through the elongated holes  875   a  and  875   b.    
     By using the resistor pressing member  876  and the conductor pressing members  877 ,  878  which are separately prepared, both of the resistive elongated board  721  and the two conductive elongated boards  711  are reliably pressed against the base  870  by the resistor pressing member  876  and the conductor pressing members  877 ,  878  even when the resistive elongated board  721  and the conductive elongated boards  711  have different thicknesses. Thus, high energy beam  881  is directed to the portion  891  and the portion  892 , with the conductive elongated boards  711  and the resistive elongated board  721  prevented from rising from the base  870 . This assures that high energy beam  881  is directed to desired portions. 
     According to this embodiment, the same advantages as those of the fourth embodiment are obtained. 
     The present invention is not limited to the foregoing embodiments. The specific structure of each part of the present invention may be varied in design in many ways.