Patent Publication Number: US-6659334-B2

Title: Method for forming end-face electrode

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for forming end-face electrodes, and in particular relates to a method for forming end-face electrodes with solder on an end-face of a substrate having electronic components such as module components mounted thereon. 
     2. Description of the Related Art 
     FIG. 18 is a plan view of a master substrate used in a conventional forming method of end-face electrodes. A master substrate  1  has plural linear gaps  2  formed thereon. With these gaps  2 , plural rectangular module substrates  3  are formed on the master substrate  1  and a waste substrate  4  is formed therearound. On an end face of the module substrate  3 , which opposes the waste substrate  4  interposing the gap  2  therebetween, plural side electrodes  5  are formed with spacing between adjacent electrodes  5 . On the module substrate  3 , electrode patterns (not shown) are formed. Then, electronic components (not shown) are mounted on the module substrate  3 , so that the electronic components and the electrode patterns are connected together so as to form circuits. In order to connect the circuits formed in such a manner to an external circuit, the electrode patterns are connected to the side electrodes  5  formed at ends of the module substrate  3 . 
     To the side electrode  5  of the module substrate  3 , an end-face electrode being convex relative to the master substrate  1  is formed with solder. For that purpose, as is shown in FIG. 19, a jig for fixation  6  is placed for fixing a solder solid on the master substrate  1 . In addition, the master substrate  1  is coated with flux in advance. In the jig for fixation  6 , a through-hole  7  is formed at a position corresponding to the side electrode  5 , and a spherical solder solid  8  is inserted into the through-hole  7 . By heating the solder solid  8  in this state, it is melted so as to hang down from the side electrode  5 . Then, by cooling the master substrate  1 , an end-face electrode  9  is formed to the side electrode  5  with solder, as shown in FIG.  20 . 
     By cutting the master substrate  1  after forming the end-face electrodes  9 , plural module components are obtained. At this time, the waste substrate  4  is removed. When mounting the module component obtained in such a manner on a motherboard, the end-face electrode  9  is placed on an electrode formed on the motherboard, to which the module component is connected by reflow. 
     In the conventional method for forming end-face electrodes, however, because the jig for fixation is used for arranging a solder solid in a position at which the side electrode is formed, a positional shift of the solder solid or non-contact between the side electrode and the solder solid occur if a position of the side electrode and a through-hole of the jig for fixation do not correspond completely to each other. Therefore, there may be cases where an end-face electrode of solder is not formed to the side electrode. 
     The solder solid is heated for melting in a state in which the jig for fixation overlaps with the master substrate, so that a number of jigs are required in mass production of module components. At this time, thermal deformation of the jig for fixation may occur. During heat treatment, flux may stick to the jig for fixation. When the jig for fixation is thermally deformed or the flux sticks to the jig, end-face electrodes may not be formed properly. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a principal object of the present invention to provide a method for forming end-face electrodes in which the end-face electrode of solder can be securely formed at a location in which a side electrode is formed and it can be formed without being affected by a jig for fixing solder solids. Moreover, the present invention provides a method for forming end-face electrodes in which a substrate having solder solids held at precise positions without using a jig for fixing solder solids can be heat-treated. 
     A method for forming end-face electrodes according to the present invention comprises the steps of preparing a substrate having gaps with side electrodes, each side electrode being formed at one of side ends opposing each other via the gap, pressing a solder solid into the gap of the substrate in order to hold the solder solid in the area where the side electrode is provided within the gap, and forming an end-face electrode on the side electrode by heating the substrate to melt the solder solid such that the end-face electrode protrudes from the substrate surface. 
     In the method for forming end-face electrodes, a part of the solder solid or the whole of the solder solid may be pressed into the gap. 
     It is preferable that hollows be formed at least at the end of the substrate in which the side electrode is formed. 
     It is also preferable that flux or solder paste be applied in the area into which the solder solid is pressed after the solder solid is pressed into the gap. 
     By pressing the solder solid into the gap of the substrate, the solder solid can be securely held to the part in which the side electrode is formed. Therefore, by melting the solder solid held in the gap, the end-face electrode made from solder protruding from the substrate surface can be formed in the side electrode with certainty. 
     When pressing the solder solid into the gap, a part of the solder solid or the whole of the solder solid may be pressed into the gap as long as the solder solid is held in contact with the side electrode. At this time, the solder solid may be deformed or may be held in a substantially non-deformed state. 
     By forming the hollow at the end of the substrate in which the side electrode is formed, the solder solid can be positioned by the hollow. At this time, the hollow may be formed in the part opposing the side electrode via the gap. 
     After the solder solid is pressed into the gap, the solderability of the solder solid to the side electrode is improved by coating it with flux when melting the solder solid, enabling the end-face electrode to be securely formed in the side electrode. Furthermore, when using solder paste instead of the flux, while electronic components are mounted on the substrate so as to be connected to the side electrode, the end-face electrode can be formed in the side electrode. After pressing the solder solids into hollows, the end-face electrodes may be formed by applying a solder paste. Electronic components to be mounted on the substrate can be soldered to electrode patterns by the solder paste. By using the solder paste, two steps of forming the end-face electrodes and mounting the electronic components can be performed at the same time. This enables reduction of the number of manufacturing processes and cost. 
     According to the present invention, a method for forming end-face electrodes may further comprise the steps of preparing a distribution plate in which holes for distributing solder solids are provided at locations corresponding to portions where the side electrodes are formed, placing the distribution plate onto the substrate, distributing solder solids into the gaps through the holes for distributing of the distributing plate, and pressing the solder solids into the gaps from above the distributing plate. 
     In such a method for forming end-face electrodes, the pressing the solder solids into the gaps may be performed with a roller from above the distribution plate after placing the distribution plate onto the substrate. 
     Also, the pressing the solder solids into the gaps may be performed with a planar plate from above the distribution plate after placing the distribution plate onto the substrate. 
     Also, the pressing the solder solids into the gaps may be performed with a pressing plate having projections corresponding to the holes for distributing by inserting the projections into the holes for distributing after placing the distribution plate onto the substrate. 
     It is preferable that when pressing solder solids into the substrate by using the roller or the planar plate, the distribution plate be removed after the solder solids are pressed into the gaps of the substrate, and the pressing be performed again from above the solder solids as principal pressing. 
     By using the distribution plate having holes for distributing solder solids, solder solids can be distributed into the gaps of the substrate at positions where the side electrodes are formed. In this state, by pressing the solder solids into the gaps from above the distribution plate, the solder solids can be held at precise positions. Thereafter, the solder solids are melted by the heat-treatment of the substrate, so that the end-face electrodes protruding with respect to the substrate are formed. Since the solder solids are pressed at the precise positions of the substrate, a jig for fixing solder solids is not required during the heat-treatment of the substrate. This eliminates the effect due to a warp of the jig for fixation, etc., resulting in reduction of defects in forming the end-face electrodes. 
     The pressing of the solder solids into the gaps may be performed with the roller from above the distribution plate or with the planar plate. Also, the solder solids may be pressed into the gaps by using the pressing plate having projections formed by corresponding to the holes for distributing so as to insert the projections into the holes for distributing. 
     When only the pressing from above the distribution plate is insufficient, the principal pressing may be performed so as to completely press the solder solids into the gaps after removing the distribution plate. 
     According to the present invention, by pressing solder solids into recesses formed on a module substrate, the solder solids can be held in contact with side electrodes formed on the module substrate securely. Therefore, end-face electrodes can be formed on the side electrodes with certainty by melting the solder solids. Also, because a jig for positioning solder solids is not required, flux cannot adhere to the jig, so that a defect for forming end-face electrodes due to the jig is not produced, resulting in improving yield in forming end-face electrodes. 
     Furthermore, when end-face electrodes are formed by printing solder paste after pressing solder solids into the recesses, electronic components mounted on the substrate with solder paste can be soldered to electrode patterns. In such a manner, by using the solder paste, the forming of the end-face electrodes and the mounting of the electronic components can be simultaneously performed, enabling reduction in the number of manufacturing processes and cost down of module components to be achieved. 
     According to the present invention, during forming end-face electrodes on a substrate, solder solids can be pressed at precise positions of the substrate in gaps formed on the substrate. Therefore, when melting solder solids by the heat-treatment of the substrate, a jig for fixing solder solids is not required. Thereby, the effect due to a warp of the jig for fixation produced during the heat-treatment is eliminated, preventing defects in forming end-face electrodes. 
     These and other objects, features, and effects of the present invention will become more apparent from the following embodiments of the present invention described in detail with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a master substrate used in a forming method of end-face electrodes according to the present invention; 
     FIG. 2 is a schematic representation showing a state of a solder solid distributed into a hollow of the master substrate shown in FIG. 1 by using a jig for distribution; 
     FIG. 3 is a schematic representation showing a state that the solder solid is pressed into the hollow of the master substrate and a reflow jig is placed thereon; 
     FIG. 4 is a schematic representation showing a state of an end-face electrode formed by solder in a side electrode; 
     FIG. 5 is a schematic representation showing an example of the pressed state of the solder solid; 
     FIG. 6 is a schematic representation showing an another example of the pressed state of the solder solid; 
     FIG. 7 is a schematic representation showing a still another example of the pressed state of the solder solid; 
     FIG. 8 is a schematic representation showing a state that the solder solid pressed into the hollow is printed with solder paste thereon; 
     FIG. 9 is a schematic representation showing another example of the hollow formed on a module substrate; 
     FIG. 10 is a schematic representation showing still another example of the hollow formed on the module substrate; 
     FIG. 11 is a schematic representation showing an example of the module substrate not having the hollow formed thereon; 
     FIG. 12 is a schematic representation showing an example of the hollow formed on a waste substrate; 
     FIG. 13 is a schematic representation showing another example of the hollow formed on a waste substrate; 
     FIG. 14 is a schematic representation showing still another example of the hollow formed on a waste substrate; 
     FIG. 15 is a schematic representation showing an example of the gap formed by the hollow of the module substrate and the hollow of the waste substrate; 
     FIG. 16 is a schematic representation showing another example of the gap formed by the hollow of the module substrate and the hollow of the waste substrate; 
     FIG. 17 is a schematic representation showing still another example of the gap formed by the hollow of the module substrate and the hollow of the waste substrate; 
     FIG. 18 is a plan view showing an example of the master substrate used in a conventional forming method of end-face electrodes; 
     FIG. 19 is a schematic representation showing a state that the solder solid is held on the master electrode by a conventional method; 
     FIG. 20 is a schematic representation showing a state that the end-face electrode is formed by solder in the side electrode by a conventional method; 
     FIG. 21 is a plan view of an example of a master substrate to which a forming method of end-face electrodes according to the present invention is applied; 
     FIG. 22 is a schematic sectional representation showing a state that solder solids are placed by putting a jig for distribution onto the master substrate shown in FIG. 21; 
     FIG. 23 is a schematic sectional representation showing a state that tops of the solder solids shown in FIG. 22 are pressurized with a roller; 
     FIG. 24 is a schematic sectional representation showing a state that principal pressing is performed with a planar upper plate for pressing after pressing solder solids into the master substrate with a roller; 
     FIG. 25 is a schematic sectional representation showing a state that tops of solder solids are coated with flux after the principal pressing shown in FIG. 24; 
     FIG. 26 is a schematic sectional representation showing a state that end-face electrodes are formed by heat-treating the master substrate having solder solids pressed thereinto; 
     FIG. 27 is a schematic sectional representation showing a state that tops of the solder solids shown in FIG. 22 are pressed with the planar upper plate for pressing; and 
     FIG. 28 is a schematic sectional representation showing a state that tops of the solder solids shown in FIG. 22 are pressed with an upper plate for pressing having projections. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a plan view illustrating a master substrate used in a forming method of end-face electrodes according to the present invention. A master substrate  10  is provided with plural linear gaps  12  formed thereon. With these gaps  12 , plural rectangular module substrates  14  are formed and a waste substrate  16  is formed therearound. At an end of the module substrate  14  in the side of the gap  12 , plural semi-spherical hollows  18  are formed with spacing between adjacent hollows  18 . In the hollow  18 , a side electrode  20  is formed so as to come on one principal plane or on both the principal planes of the hollow  18  from an end face thereof. On one plane of the module substrate  14 , electrode patterns (not shown) are formed, to which electronic components (not shown) are fitted so as to form plural circuits. In order to connect the circuits formed in such a manner to an external circuit, the electrode patterns are connected to the side electrodes  20 . By cutting these plural circuits, plural module components are formed. 
     In order to mount the module components, which are finally obtained, on a motherboard, etc., end-face electrodes are formed with solder to the side electrodes  20 . In that purpose, as shown in FIG. 2, a spherical solder solid  22  is placed on a part of the side electrode  20 . At this time, a jig for distribution  24  is used, which has a through-hole formed at a position corresponding to the side electrode  20 . By distributing the solder solid  22  into the through-hole  24   a  of the jig for distribution  24 , the solder solid  22  is placed on a part of the side electrode  20 . In addition, because the hollows  18  are formed in a part on which the side electrode  20  of the module substrate  14  is formed, the solder solid  18  is positioned into the hollow  18 . The through-hole  24   a  formed on the jig for distribution  24 , therefore, is not for fixing the solder solid  22 , so that it is sufficient to have an enough size for distributing the solder solid  22  in the vicinity of the side electrode  20 . 
     The solder solid  22  placed on the side electrode  20 , as shown in FIG. 3, is pressed into the gap  12  by press working. The press working is performed by sandwiching the master substrate  10  and the solder solid  22  between flat plates under a pressure of 10 kg/point, for example. By pressing the solder solid  22  into the gap  12  in such a manner, the solder solid  22  is held in contact with the side electrode  20 . Then, the surface of the master substrate  10  is coated with flux and the solder solid  22  is melted by reflow at a temperature between 220 and 240° C. in an atmosphere of N 2 . At this time, in order to prevent the master substrate  10  from deforming, a plate-like reflow jig  26  may be placed along the master substrate  10  except the gap  12  and the side electrode  20 , as shown in FIG.  3 . 
     When the solder solid  22  is melted, solderability of the side electrode  20  is promoted due to the function of the flux, so that melted solder sticks to the side electrode  20 . By cooling the solder in this state, as shown in FIG. 4, an end-face electrode  28  being convex relative to the surface of the master substrate  10  is formed with solder in the side electrode. The module substrates having circuits formed thereon are separated by cutting the master substrate  10  having the end-face electrodes  28  formed thereon so as to obtain plural module components  14 . At this time, the waste substrate  16  is removed. When mounting the module component obtained in such a manner on a motherboard, the end-face electrode  28  is placed on an electrode pattern formed on the motherboard, and the side electrode  20  of the module component and the electrode pattern of the motherboard are soldered together by reflow. 
     When such a method for forming end-face electrodes is adopted, the solder solid  22  can be securely brought into contact with the side electrode  20  by pressing the solder solid  22 , thereby forming the end-face electrode  28  in the side electrode  20  with certainty. The non-defective rate in formation of the end-face electrodes  28  can be therefore improved. Also, because the jig for positioning the solder solid  22  is not required, reduction in cost can be promoted. Furthermore, because the jig for positioning the solder solid  22  is not used when melting the solder solid  22 , such defectives as produced due to flux sticking to the jig can be avoided. 
     In addition, when pressing the solder solid  22  into the gap  12 , as shown in FIG. 5, it may be pressed to an intermediate portion of the master substrate  10  in the thickness direction; or it may be pressed to the bottom surface of the master substrate  10 , as shown in FIG.  6 . When pressing the solder solid  22  to the bottom surface of the master substrate  10 , the solder solid  22  may not be deformed much, as shown in FIG. 6; or the solder solid  22  may be deformed so as to plug the most part of the hollow  18 , as shown in FIG.  7 . In such a manner, regardless of the pressing extent and the deformation existence of the solder solid  22 , the end-face electrode  28  can be certainly formed as long as the solder solid  22  is held in contact with the side electrode  20 . 
     Also, as shown in FIG. 8, the end-face electrode  28  may be formed by printing solder paste  30  on one surface of the master substrate  10  so as to melt the solder solid  22  after pressing the solder solid  22  into the gap  12  of the master substrate  10 . In this case, while the solderability between the side electrode  20  and the melted solder solid  22  is improved by the solder paste  30 , electronic components mounted on the module substrate  14  can be soldered to the electrode pattern. In such a manner, by using the solder paste  30  instead of the flux, the forming of the end-face electrode  28  and the mounting of electronic components can be simultaneously carried out. In addition, it is preferable that the solder solid  22  be deformed so as to plug the hollow  18 . 
     The shape of the hollow  18  formed in the module substrate  14  is not only semi-circular as shown in FIG. 2 but also it may be rectangular shown in FIG. 9 or triangular as shown in FIG.  10 . In such a manner, the shape of the hollow  18  formed in the module substrate  14  may be arbitrarily changeable as long as the solder solid  22  can be positioned in a part of the side electrode  20 . Also, as shown in FIG. 11, the hollow  18  may not be formed. In this case, although it is needed to prevent the positional shift of the solder solid  22 , the end-face electrode  28  can be securely formed when pressing the solder solid  22  into the gap  12  just like in the case of the master substrate  10  having the hollows  18 . 
     In order to improve the accuracy in positioning the solder solid  22  furthermore, as shown in FIG. 12, a semi-circular hollow  32  may be formed in the waste substrate  16  opposing the hollow  18 . By forming the hollow  32  also in the waste substrate  16  in such a manner, the accuracy in positioning the solder solid  22  can be improved in collaboration with the hollow  18  in the module substrate  14 . In the waste substrate  16 , the hollow  32  may of course be rectangular as shown in FIG. 13 or triangular as shown in FIG.  14 . 
     Furthermore, the gap is not limited to be linear; it may be formed by the hollow  18  of the module substrate  14  and the hollow  32  of the waste substrate  16 . That is, as shown in FIG. 15, the two hollows  18  and  32  may be formed between the module substrate  14  and the waste substrate  16 , and the module substrate  14  may be closely stuck to the waste substrate  16  except the part of the hollows  18  and  32 . In this case, the solder solid  22  can be also pressed in contact with the side electrode  20  formed in the part of the hollow  18 . The shape of the hollow  32  in the waste substrate  16  may also be semi-circular as shown in FIG. 15, and it may be rectangular shown in FIG. 16, or triangular as shown in FIG.  17 . In FIGS. 15 to  17 , the rift between the module substrate  14  and the waste substrate  16  may not be formed. In this case, by finally cutting the master substrate  10  between the two hollows  18  and  32 , module parts can be obtained. 
     In addition, the solder solid  22  may have not only a spherical shape but also any one of shapes such as columnar, conical, hemispherical, prismatic, pyramidal, and T-shaped shapes as long as it can be pressed into the hollow  18 . The material of the solder solid  22  may be any metallic composition such as SnPb, SnAg, SnCu, SnSb, SnBi, SnZn, and SnAgCu, and it may be a material coated thereon. 
     FIG. 21 is a plan view of an example of a master substrate used in a method for forming end-face electrodes according to the present invention. On a master substrate  110 , plural straight gaps  112  are formed along the external shapes of required module substrates. By these gaps  112 , plural rectangular module substrates  114  are formed, and waste substrates  116  are formed at the periphery of the module substrates  114 . The master substrate  110  may have a thickness of 0.7 mm, and the gap  112  may have a size of 0.85 mm, for example. 
     At one end of the module substrate  114  in the side of the gap  112 , plural semicircular recesses  118  are formed separated with the gap  112  therebetween. The recess  118  may have a diameter of 0.7 mm, for example. The recess  118  is provided with a side electrode  120  formed so as to come on one principal surface or both principal surfaces from the end-face. On one surface of the module substrate  114 , electrode patterns (not shown) are formed, so that plural electronic components (not shown) are mounted on the electrode patterns so as to form plural circuits. In order to connect the circuits formed in such a manner to an external circuit, the electrode patterns are connected to the side electrodes  120 . By cutting these plural circuits, plural module components are formed. 
     In order to mount the finally obtained module component on a motherboard, etc., an end-face electrode is formed on the side electrode  120  with solder. To this end, as shown in FIG. 22, a spherical solder solid  122  having a diameter of 1.1 mm, for example is placed on part of the side electrode  120 . At this time, a distribution plate  124  having holes  124   a  for distribution formed at positions corresponding to the side electrodes  120  is put on the master substrate  110 . The hole  124   a  for distribution is formed to have a diameter of 1.5 mm, for example. By distributing solder solids  122  into the holes  124   a  for distribution of the distribution plate  124 , the solder solid  122  is placed on part of the side electrode  120 . 
     In a state that the distribution plate  124  is put on the master substrate  110 , as shown in FIG. 23, a roller  126  is moved in one direction or moved back and forth thereon, so that the solder solids  122  are pressed into the gaps  112  of the master substrate  110 . In order to press the solder solids  122  into the gaps  112  by the roller  126 , it is necessary that the solder solid  122  protrude through the top of the distribution plate  124 . Therefore, the distribution plate  124  having a thickness of 0.3 mm is used, for example. 
     As the roller  126 , a hand roller having a diameter of 40 mm, for example, and made of stainless steel is used and moved by an operator. In order to prevent damage of the master substrate  110  at this time, an under plate  128  for pressing is arranged on the bottom surface of the master substrate  110 . In addition, when the number of the solder solids  122  is large, a force applied to one solder solid  122  becomes smaller so that the solder solids  122  cannot be completely pressed into the master substrate  110 ; however, they can be pressed thereinto to an extent that the solder solid  122  cannot move within the gap  112  of the master substrate  110 . The extent of pressing the solder solid  122  can be adjusted by setting the number of movements of the roller  126 . 
     Next, as shown in FIG. 24, after removing the distribution plate  124 , principal pressing is performed on the solder solids  122  by using a planar upper plate  130  for pressing to which mechanical pressure is applied. The principal pressing is performed by applying a pressure of 98 N per one solder solid, for example. The gap  112  is filled with the solder solid  122  by the principal pressing so as to plug the gap  112  of the master substrate  110 . 
     After the gaps  112  of the master substrate  110  are filled with the solder solids  122 , as shown in FIG. 25, the solder solids  122  are coated with flux  132  and are melted by heating so as to adhere to the side electrodes  120 . It is preferable that a jig for preventing warping  134  be arranged on the bottom surface of the master substrate  110  so as not to produce a warp on the master substrate  110  at this time. In the jig for preventing warping  134 , recesses  136  are formed at positions corresponding to the gaps  112  of the master substrate  110 , so that melted solder cannot adhere to the jig for preventing warping  134 . As shown in FIG. 26, by cooling the solder when the melted solder adheres to the side electrode  120 , an end-face electrode  138  is formed to protrude from the bottom surface of the master electrode  110 . 
     On the master substrate  110  having the end-face electrodes  138  formed thereon, electronic components such as ICs are mounted, which in turn is cut so as to divide it into the module substrates  114  and the waste substrates  116 , thereby obtaining plural module components. At this time, the waste substrates  116  are removed. When the module component is mounted on a motherboard, etc., the end-face electrode  138  is placed on an electrode pattern of the motherboard, and the side electrode  120  of the module component and the electrode pattern of the motherboard are soldered by reflow process. 
     When such a forming method of end-face electrodes is adopted, because the solder solids  122  are pressed into the gaps  112  from above the distribution plate  124  with the roller  126 , the solder solid  122  can be securely pressed within at a predetermined position. Therefore, when forming the end-face electrodes  138  by heat-treating, a jig for fixing the solder solids  122  is not required. Moreover, because the solder solid  122  is pressed within at a predetermined position, the end-face electrode  138  can be securely formed to part of the side electrode  120  without a positional shift. 
     When pressing the solder solids  122  thereinto from above the distribution plate  124 , as shown in FIG. 27, pressure may also be mechanically applied thereto by using the planar upper plate  130  for pressing. In this case, the force can be equally applied to the entire solder solids  122 , so that the operation can be performed within a short period of time. Since the solder solid  122  is protruding above the master substrate  110  by the thickness of the distributing plate  124  also in this case, the principal pressing is performed after removing the distributing plate  124 . When using the above-mentioned roller  126  or upper plate  130  for pressing, the principal pressing is not necessarily performed as long as the melted solder adheres to the side substrate  120  during the heat-treating. 
     Furthermore, as shown in FIG. 28, the upper plate  130  for pressing having projections  140  formed thereon may be used. The projections  140  are formed at positions corresponding to the holes  124   a  for distribution of the distribution plate  124 . The solder solids  122  can be pressed into the gaps  112  by pressing so as to insert the projections  140  into the holes  124   a  for distribution of the distribution plate  124 . The solder solids  122  can be completely pressed into the gaps  112  without performing the principal pressing for this case. At this time, the pressing is performed under a pressure of 98 N per one solder solid  122 , for example. 
     When using the upper plate  130  for pressing having the projections  140  formed thereon, it is not necessary that the solder solids  122  protrude above the distribution plate  124 , so that limits associated with the thickness of the master substrate  110 , the diameter of the solder solid  122 , and the thickness of the distribution plate  124  can be relaxed. 
     By pressing the solder solids  122  from above the distribution plate  124  in such a manner, the solder solids  122  can be pressed into the master substrate  110  at precise positions. Accordingly, the end-face electrodes  138  can be formed at precise positions in the master substrate  110 . Therefore, a positional shift of the end-face electrode  138  may be prevented, thereby improving yield. Also, because the heat-treatment is performed in a state that the solder solids  122  are pressed into the gaps  112 , a jig for fixing solder solids is not required, so that the affect due to the thermal deformation of the jig for fixation is eliminated, enabling defects in forming the end-face electrodes  138  to be reduced. 
     In addition, the semicircular recesses  118  are formed on the master substrate  110 ; however, such recesses are not necessarily required. That is, even to the side substrates  120  formed at regular intervals to the straight gaps  112  formed on the master substrate  110 , the solder solids  122  may be distributed at precise positions with the distribution plate. Moreover, the recesses  118  may be formed in the side of the waste substrate  116 . As described above, by forming the recesses in the side of the module substrate  114  or the waste substrate  116 , the stability of the solder solid  122  can be increased. The shape of the recess is not limited to a semicircle; another shape such as a triangle and a rectangle may be adopted.