Abstract:
The object of the invention is to provide a method of forming an external electrode of an electronic component whereby the external electrode can be formed in a stable fashion. In order to achieve this object, a method of fonning an external electrode according to the present invention includes: a step of forming an electrode portion  301   a  on a side face  30   a  of a chip  30  constituting an electronic component by applying a conductive paste  20  from a direction facing this side face  30   a ; a step of forming an electrode portion  301   b  on a side face  30   b  of the chip  30  facing the side face  30   a  by applying the conductive paste  20  from a direction facing this side face  30   b ; a step of forming an electrode portion  301   c  so as to connect the electrode portion  301   a  and electrode portion  301   b  on the bottom face of the chip  30  respectively adjacent to the side face  30   a  and the side face  30   b ; and a step of forming an external electrode  301  comprising the electrode portion  301   a , electrode portion  301   b  and electrode portion 301c by drying this chip  30.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method of forming an external electrode of an electronic component.  
         [0003]     2. Related Background Art  
         [0004]     One method of forming an external electrode of an electronic component is the method set out in U.S. Pat. No. 5,753,299. This method is a method of forming an external electrode on the end face of a chip which is an element constituting an electronic component and on the side face adjacent to this end face. More specifically, continuous projecting portions called fingers of a comb-shaped plate are arranged in a position facing the side face of the chip and conductive paste for forming an external electrode is applied to the tips of these fingers. An external electrode is then formed by rubbing conductive paste onto the chip by bringing the fingers into contact with the chip and sliding the fingers in a direction intersecting the direction of extension of the chip.  
       SUMMARY OF THE INVENTION  
       [0005]     As described above, when an external electrode is formed by rubbing conductive paste onto the end face of the chip, the external electrode that is formed on the side face is formed by hanging down of conductive paste. More specifically, the conductive paste sliced off and falling from the edge defined by the end face and side face flows along the side face of the chip, thereby forming an external electrode on the side face. Consequently, the shape of the external electrode formed on the side face of the chip is controlled by the viscosity and other properties of the conductive paste. However, since it is difficult to freely control the viscosity of the conductive paste, it is difficult to control the length of the external electrode on the side face of the chip in the direction departing from the edge by adjusting the viscosity of the conductive paste.  
         [0006]     The present inventors therefore studied from various aspects the possibility of controlling the length of the external electrode by a method that should not depend on adjustment of the viscosity of the conductive paste. As an initial step in these studies, the present inventors studied whether it might be possible to control the length of the external electrode by adjusting the quantity of conductive paste sliced off and falling from the edge defined by the end face and side face of the chip. However, the present inventors discovered that, if the amount of conductive paste is increased, although the extension of the external electrode on the side face of the chip in the direction departing from the edge along the end face is increased, the extension thereof in the direction along the edge is also inevitably increased. As a result of this discovery, they realized that the separation between adjacent external electrodes would be insufficient, with a risk of inter-electrode shorting.  
         [0007]     In the next step in their studies, the present inventors discovered that, if the amount of conductive paste was decreased in order to ensure an adequate distance between the adjacent external electrodes, decrease in the amount of conductive paste hanging down from the edge gave rise to the risk that extension of the external electrodes in the direction departing from the edge might be restricted and that sufficient area of the external electrode might not be ensured. As a result of further study, the present inventors also discovered that, when external electrodes were formed in this way by conductive paste being sliced off and falling from the edge, the condition of the external electrodes on the side face was governed by the way in which the conductive paste hung down; thus the shape of the external electrodes was sometimes unstable. This was a factor giving rise to the Manhattan phenomenon when mounted on a substrate.  
         [0008]     Accordingly, an object of the present invention is to provide a method of forming an external electrode of an electronic component wherein the external electrode can be formed in stable fashion.  
         [0009]     In order to achieve the above object, a method of forming an external electrode of an electronic component according to the present invention comprises: a first forming step of forming a first electrode portion on a first face of an element constituting an electronic component by applying a conductive paste from a direction facing this first face; a second forming step of forming a second electrode portion on a second face of the element facing the first face by the applying conductive paste from a direction facing this second face; a third forming step of forming a third electrode portion so as to connect the first electrode portion and second electrode portion on a third face of the element respectively adjacent to the first face and the second face; and an electrode forming step of forming an external electrode comprising the first electrode portion, second electrode portion and third electrode portion by drying this element.  
         [0010]     Since, according to the present invention, conductive paste is applied from directions facing the respective faces respectively to the first face and second face of the element, a first electrode portion and second electrode portion can be stably formed in the intended shape on the respective faces. Also, since the third electrode portion is formed so as to connect these after formation of the first electrode portion and second electrode portion, an external electrode can be formed in stable fashion.  
         [0011]     A method of forming an external electrode of an electronic component according to the present invention comprises: a first forming step of forming a first electrode portion on a first face of an element constituting an electronic component by applying a conductive paste from a direction facing this first face; a second forming step of forming a second electrode portion on a second face of the element facing the first face by applying the conductive paste from a direction facing this second face; an intermediate processing step of decreasing the fluidity of the conductive paste in the first electrode portion and second electrode portion by drying the element; a third forming step of forming a third electrode portion so as to connect the first electrode portion and second electrode portion on a third face of the element respectively adjacent to the first face and the second face; and an electrode forming step of forming an external electrode comprising the first electrode portion, second electrode portion and third electrode portion by drying this element.  
         [0012]     Since, according to the present invention, conductive paste is applied from directions facing the respective faces respectively to the first face and second face of the element, a first electrode portion and second electrode portion can be stably formed in the intended shape on the respective faces. Also, since the third electrode portion is formed after decreasing the fluidity of the conductive paste in the first electrode portion and second electrode portion, reduction in thickness of the portions that connect the third electrode portion respectively with the first electrode portion and second electrode portion can be suppressed.  
         [0013]     Also, preferably, a method of forming an external electrode according to the present invention further comprises a preparatory step of preparing a jig having a groove capable of insertion of the element and filling the interior of the groove of the jig with conductive paste, and a removal step of causing the conductive paste with which filling is performed to remain along at least the wall face of the groove and removing the residue; wherein, in the first forming step, the element is inserted in the groove and a first electrode portion is formed by moving the element such that the first face thereof approaches one wall face of the groove and, in the second forming step, a second electrode portion is formed by moving the element such that a second face thereof approaches the other wall face of the groove.  
         [0014]     With this preferred method, the first electrode portion and second electrode portion can be formed in a more convenient and stable fashion by depositing on the element the conductive paste remaining along the wall face of the groove capable of insertion of an element.  
         [0015]     Also, in a method of forming an external electrode according to the present invention, preferably, in the first forming step, first electrode portions are formed juxtaposed in a plurality of locations on the first face and, in the second forming step, second electrode portions are formed in positions respectively corresponding to the first electrode portions formed juxtaposed in the plurality of locations and, in the third forming step, third electrode portions are formed so as to connect with the respective first electrode portions formed juxtaposed in the plurality of locations and so as to connect with the respective second electrode portions formed in the corresponding positions.  
         [0016]     With this preferred method, since the first electrode portions and second electrode portions are formed in juxtaposed fashion in a plurality of locations in correspondence and the third electrode portions are formed so as to connect with the corresponding first electrode portions and second electrode portions, the external electrodes can be formed in an efficient and stable fashion.  
         [0017]     Also, preferably, a method of forming an external electrode according to the present invention further comprises a preparatory step of preparing a jig in which a plurality of plate-shaped members formed with grooves capable of insertion of an element are arranged alongside each other and filling the interior of the respective grooves with conductive paste so as to span and cover the respective grooves of the plurality of plate-shaped members; and a removal step of removing the conductive paste introduced between the respective plurality of plate-shaped members, to cause the conductive paste that is introduced into the respective grooves to remain along at least the wall face of the respective grooves; wherein, in the first forming step, the element is inserted across the respective grooves and the first electrode portions are formed by moving the element such that the first face thereof approaches one wall face of the respective grooves; and, in the second forming step, the second electrode portions are formed by moving the element such that the second face thereof approaches the other wall face of the respective grooves.  
         [0018]     With this preferred method, excess conductive paste with which the respective grooves are filled is allowed to flow out by filling the grooves of the plurality of plate-shaped members arranged alongside each other with conductive paste and then removing the conductive paste between the plurality of plate-shaped members. Consequently, conductive paste can remain along the wall faces of the respective grooves of the plurality of plate-shaped members.  
         [0019]     With the present invention as described above, external electrodes can be formed in stable fashion since the first electrode portions, second electrode portions and third electrode portions can be formed in stable fashion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The present invention may be more readily described with reference to the accompanying drawings, in which:  
         [0021]      FIG. 1  is a perspective view showing an outline of a method of forming an external electrode according to a first embodiment of the present invention;  
         [0022]      FIG. 2  is a view showing a method of forming an external electrode according to a first embodiment of the present invention;  
         [0023]      FIG. 3  is a view given in explanation of a method of forming an external electrode according to a first embodiment of the present invention;  
         [0024]      FIG. 4  is a view given in explanation of a method of forming an external electrode according to a first embodiment of the present invention;  
         [0025]      FIG. 5  is a view given in explanation of a method of forming an external electrode according to a first embodiment of the present invention;  
         [0026]      FIG. 6  is a view given in explanation of a method of forming an external electrode according to a second embodiment of the present invention;  
         [0027]      FIG. 7  is a view given in explanation of a method of forming an external electrode according to a second embodiment of the present invention; and  
         [0028]      FIG. 8  is a view given in explanation of a method of forming an external electrode according to a second embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     The discovery of the present invention can easily be understood by considering the following detailed description with reference to the appended drawings, which are given solely by way of example. Embodiments of the present invention will now be descnbed with reference to the appended drawings. Where possible, identical portions are given the same reference symbols and duplication of description is dispensed with.  
         [0030]     (First embodiment) A method of forming an external electrode constituting a first embodiment of the present invention will now be described. As shown in  FIG. 1 , an outline of the method of forming an external electrode according to this embodiment is that a conductive paste application bed  10  (jig) is prepared that is formed with a groove  101  and conductive paste  20  is deposited thereon along the wall faces and bottom faces of this groove  101 . After this, a chip  30  (element) is inserted into the groove  101  and external electrodes  301  are formed on both side faces of the chip  30  by moving the chip  30  along the direction of the arrow in the Figure (direction orthogonal to the direction of extension of the groove). Next, a method of forming external electrodes will be descnbed in detail.  
         [0031]      FIG. 2  is a view given in explanation of the sequence of the method of forming an external electrode according to the present embodiment.  FIG. 3  to  FIG. 5  are views of the chip  30  and application bed  10  seen from the direction looking through the groove  101 , being views showing the condition in the various steps of the method of forming an external electrode. The flow shown in  FIG. 2  will now be described referring as appropriate to  FIG. 3  to  FIG. 5 .  
         [0032]     The groove  101  of the application bed  10  is filled with conductive paste  20  (step S 01  in  FIG. 2 ,  FIG. 3 (A), preparatory step). As shown in  FIG. 3 (A), the groove  101  is filled with conductive paste  20  and filling is performed to such a degree that the conductive paste rises above the main face  102  of the application bed  10 .  
         [0033]     Next, the conductive paste in the groove  101  is scraped out using a blade  40  (step S 02  in  FIG. 2 ,  FIG. 3 (B), removal step). As shown in  FIG. 3 (B), the blade  40  is of convex shape so as to enter the groove  101 , so that a gap is formed between the blade  40  and the groove  101  corresponding to the portion thereof that enters the groove  101 . Consequently, as shown in  FIG. 3 (C), conductive paste  20  remains along the side walls  101   a ,  101   b  and bottom face  101   c  of the groove  101 , while the residue is removed.  
         [0034]     Next, the tip of the chip  30  is arranged in a position inserted into the groove  101  in a position in which the chip  30  faces the groove  101  (step S 03  in  FIG. 2 ,  FIG. 3 (D)). The length of the chip  30  that enters the groove  101  is a length corresponding to the electrode portion that is formed in the subsequent steps. The chip  30  is held by being stuck to tacky adhesive tape  51  provided on a holding plate  50 .  
         [0035]     From the condition of  FIG. 3 (D), the holding plate  50  and the application bed  10  are relatively moved (step S 04  in  FIG. 2  and  FIG. 4 (A)) such that the side face (first face)  30   a  of the chip  30  approaches the side wall  101   a  of the groove  101 . When the holding plate  50  and application bed  10  are relatively moved in this way, the side face  30   a  of the chip comes into abutment with the side face  101   a  of the groove  101  ( FIG. 4 (A)).  
         [0036]     When the holding plate  50  and the application bed  10  are further relatively moved, as shown in  FIG. 4 (B), a condition is produced in which the chip  30  is stuck in the groove  101  and the chip  30  is in fact. tilted. In this way, even in the case of an operation to juxtapose a plurality of chips  30  along the groove  101 , the chips  30  can be precisely brought into contact with the side wall  101   a  of the groove  101 .  
         [0037]     By producing the conditions as shown in  FIG. 4 (A) and (B), an electrode portion  301   a  (first electrode portion) is formed (first forming step) on the side face  30   a  of the chip  30 .  
         [0038]     Next, the holding plate  50  and the application bed  10  are relatively moved (step S 05  in  FIG. 2 ,  FIG. 4 (C)) such that the side face (second face)  30   b  of the chip  30  approaches the side  101   b  of the groove  101 . When the holding plate  50  and the application bed  10  are relatively moved in this way, the side face  30   b  of the chip abuts the side wall  101   b  of the groove  101  ( FIG. 4 (C)).  
         [0039]     When the holding plate  50  and the application bed  10  are further relatively moved, as shown in  FIG. 4 (D), the chip  30  assumes a condition in which it is stuck in the groove  101  and the chip  30  thus assumes a tilted condition.  
         [0040]     By putting the chip in the conditions of  FIG. 4 (C) and (D), an electrode portion  301   b  (second electrode portion) is formed on the side face  30   b  of the chip  30  (second forming step).  
         [0041]     Next, the holding plate  50  and the application bed  10  are relatively moved ( FIG. 5 (A)) such that the chip  30  is positioned in the vicinity of the center of the groove  101 . From this position, the holding plate  50  and the application bed  10  are brought together ( FIG. 5 (B)) such that the tip of the chip  30  abuts the bottom face  101   c  (third face) of the groove  101 . When the tip of the chip  30  abuts the bottom face  101   c  of the groove  101 , an electrode portion  301   c  (third electrode portion) connecting the electrode portion  301 a and the electrode portion  301   b  is formed (step S 06  of  FIG. 2 , third forming step).  
         [0042]     Next, when the holding plate  50  and the application bed  10  are separated and the chip  30  is dried, an external electrode  301  is formed ( FIG. 5 (C), electrode forming step) connecting the electrode portion  301   a,  electrode portion  301   b  and electrode portion  301   c . It should be noted that, although, in this embodiment, the chip  30  is dried after formation of the electrode portion  301   c , it would also be possible to perform drying (intermediate processing step) after the formation of the electrode portion  301   b  but prior to the formation of the electrode portion  301   c . In this way, since the electrode portion  301   c  is formed after lowering the fluidity of the electrode portions  301   a  and  301   b,  it is possible to suppress thinning of the angle whereby the electrode portion  301   a  and electrode portion  301   c  are connected and/or thinning of the angle whereby the electrode portion  301   b  and electrode portion  301   c  are connected.  
         [0043]     Next, the conductive paste in the groove  101  is scraped out using the blade  45  (step S 07  in  FIG. 2 ,  FIG. 5 (D)). As shown in  FIG. 5 (D), the blade  45  is of convex shape so as to enter the groove  101 . The difference with respect to the blade  40  shown in  FIG. 3 ( d ) is that the blade  45  is formed so that no gap is produced between the groove  101  and the portion of this blade  45  that enters the groove  101 . Consequently, as shown in  FIG. 5 (E), all of the conductive paste within the groove  101  is scraped out.  
         [0044]     As described above, in this embodiment, since conductive paste  20  is applied to the respective side faces  30   a ,  30   b  of the chip  30  from the direction facing these respective faces, the electrode portion  301   a  and electrode portion  301   b  can be formed in the desired shape in stable fashion on these respective faces. Also, since the electrode portion  301   c  is formed after formation of the electrode portion  301   a  and electrode portion  301   b  so as to connect these, the external electrode  301  can be formed in stable fashion.  
         [0045]     Also, in this embodiment, by depositing the conductive paste  20  that remains along the wall faces of the groove  101  that is capable of insertion of the chip  30  on the chip  30  the electrode portion  301   a  and electrode portion  301   b  can be formed in a more convenient and stable fashion.  
         [0046]     (Second embodiment) A method of forming an external electrode according to a second embodiment of the present invention will now be described. The method of forming an external electrode according to this embodiment is a method wherein a plurality of external electrodes are simultaneously formed on a chip. The differences with respect to the first embodiment lie chiefly in the form of the application bed, constituting a jig, that is used and/or the blade.  FIG. 6  to  FIG. 8  are views given in explanation of the sequence of this method of forming an external electrode according to this embodiment. The method of forming an external electrode according to this embodiment will now be described with reference to  FIG. 6  to  FIG. 8 .  
         [0047]     First of all, an application bed  6  and blade  7  are prepared ( FIG. 6 (A)). The application bed  6  comprises a base  60  and four plate-shaped members  61 . The plate-shaped members  61  are mounted on the base  60  so as to be mutually parallel, with a separation therebetween. Grooves  611  are formed in the same position in the respective plate-shaped members  61 .  
         [0048]     The blade  7  comprises a base  70  and a scraping section  71 . The scraping section  71  is formed with teeth  711 . The teeth  711  are formed so as to enter between the plate-shaped members  61  of the application bed  6 .  
         [0049]     Next, conductive paste  8  is piled up ( FIG. 6 (B)) so as to span and cover the respective grooves  611  of the plate-shaped members  61  of the application bed  6 . The grooves  611  of the plate-shaped members  61  are thereby filled with conductive paste  8  (preparatory step).  
         [0050]     Next, the blade  7  and application bed  6  are relatively moved ( FIG. 7 (A)) such that the blade  7  and application bed come into abutment. When movement is carried out in this way, the respective teeth  711  of the blade  7  are inserted between the respective plate-shaped members  61  of the application bed  6 . The tips of the teeth  711  are formed such that, in a condition in which they abut the base  60  of the application bed  6 , gaps are formed between the top ends of the plate-shaped members  61  and the roots between the teeth  711 . The conductive paste  8  is therefore extruded onto the plate-shaped members  61  from these gaps.  
         [0051]     Next, the conductive paste  8  that was introduced between the plate-shaped members  61  is scraped out ( FIG. 7 (B), removal step) by moving the blade  7  along the plate-shaped members  61 . Since the conductive paste  8  is fluid, the conductive paste  8  remaining in the grooves  611  of the plate-shaped members  61  flows out ( FIG. 7 (C)) between the plate-shaped members  61 . Consequently, conductive paste  8  remains along the grooves  61  l.of the plate-shaped members  61 .  
         [0052]     Next, the chip  90  is arranged across the grooves  611  of the respective plate-shaped members  61 . At this point, the tips of the chip  90  are arranged in positions inserted into the grooves  611 . The length of insertion of the chip  90  into the grooves  611  is the length of the electrode portions. Just as in the case of the first embodiment, the chip  90  is held by being stuck onto tacky adhesive tape (not shown) provided on a holding plate (not shown).  
         [0053]     Next the chip  90  and the application plate  60  are relatively moved ( FIG. 8 (A)) such that the side faces  90   a  of the chip  90  come into abutment with the grooves  611  of the plate-shaped members  61 . The four electrode portions  901   a  (first electrode portions) are formed (first forming step) by bringing the side faces  90   a  of the chip  90  into abutment with the respective grooves  611  of the four plate-shaped members  61 .  
         [0054]     Next the chip  90  and the application bed  60  are relatively moved ( FIG. 8 (B)) such that the side faces  90   b  of the chip  90  come into abutment with the grooves  611  of the plate-shaped members  61 . The four electrode portions  901   b  (second electrode portions) are formed (second forming step) by bringing the side faces  90   b  of the chip  90  into abutment with the respective grooves  611  of the four plate-shaped members  61 .  
         [0055]     Next, the chip  90  and the application bed  6  are relatively moved (vertical direction in the Figure) so as to be mutually separated. In addition, the chip  90  and the application bed are relatively moved such that the chip  90  is positioned above the portion of the plate-shaped members  61  that is not provided with grooves  611 . After this, the chip  90  and the application bed  6  are relatively moved ( FIG. 8 (C)) such that the chip  90  abuts the portion of the plate-shaped members  61  that is not provided with grooves  611 . When the tips of the chip  90  come into abutment with the portion of the plate-shaped members  61  that is not provided with grooves  611 , the electrode portions (third electrode portions, not explicitly shown in  FIG. 8 ) that connect the electrode portions  901   a  and, electrode portions  901   b  are formed (third forming step).  
         [0056]     Next, when the chip  90  and the application bed  6  are moved away from each other and the chip  90  is dried, the external electrodes are formed (electrode forming step) by connection of the electrode portion  901   a , electrode portion  901   b  and the electrode portions that connect the electrode portion  901   a  and electrode portion  901   b.    
         [0057]     As described above, in this embodiment, the electrode portions  901   a  and electrode portions  901   b  can be formed in a stable fashion in the intended shape on the respective faces by the application of conductive paste  8  from a direction facing the respective faces to the respective side faces  90   a ,  90   b  of the chip  90 . Also, the external electrode can be formed in stable fashion, after formation of the electrode portion  901   a  and electrode portion  901   b , by formation of the electrode portion so as to connect these.  
         [0058]     Also, in this embodiment, thanks to the formation of the corresponding electrode portions  901   a  and electrode portions  901   b  in correspondence, juxtaposed in a plurality of locations, the external electrodes can be formed in efficient and stable fashion by the formation of electrode portions so as to connect these corresponding electrode portions  901   a  and electrode portions  901   b.    
         [0059]     Also, in this embodiment, by filling the grooves  611  of the plurality of plate-shaped members  61  that are arranged alongside each other with conductive paste  8  and then removing the conductive paste  8  between the plurality of plate-shaped members  61 , the excess conductive paste  8  with which the respective grooves  611  are filled flows out of the grooves. Consequently, conductive paste  8  can remain along the side walls of the respective grooves  611  of the plurality of plate-shaped members  61 .