Aligning device and method for producing electronic component using the aligning device

Abstract

In an aligning device, in plan view, a first recess of a first transfer jig allows an entire region of a second recess of the first transfer jig to be situated within the first recess of the first transfer jig by a predetermined interval. When the first transfer jig and the second transfer jig overlap each other, the first recess of the second transfer jig allows the entire region of the second recess of the first transfer jig to be situated within the first recess of the second transfer jig by a predetermined interval. With the alignment object being transferred into a cavity of the first transfer jig, by causing the first transfer jig and the second transfer jig to overlap each other, the alignment object is transferred from the cavity of the first transfer jig to a cavity of the second transfer jig.

Claims

1. A method for producing an electronic component using an aligning device that comprises a first transfer jig including a cavity that includes a first recess and a second recess configured such that an alignment object to be transferred is capable of being transferred into the cavity, the first recess opening towards a principal surface, the second recess being adjacent to the first recess in a depth direction and communicating with the first recess, and a second transfer jig including a cavity that includes a first recess and a second recess configured such that the alignment object is capable of being transferred into the cavity of the second transfer jig, the first recess of the second transfer jig opening towards the principal surface, the second recess of the second transfer jig being adjacent to the first recess of the second transfer jig in the depth direction and communicating with the first recess of the second transfer jig, wherein in plan view, the first recess of the first transfer jig has a shape and dimensions that allow an entire region of the second recess of the first transfer jig to be situated within the first recess of the first transfer jig by a predetermined interval, in plan view, the first recess of the second transfer jig has a shape and dimensions that allow an entire region of the second recess of the second transfer jig to be situated within the first recess of the second transfer jig by a predetermined interval, and when the first transfer jig and the second transfer jig are caused to overlap with each other, in plan view, the first recess of the second transfer jig has the shape and dimensions that allow the entire region of the second recess of the first transfer jig to be situated within the first recess of the second transfer jig by a predetermined interval, the method comprising the steps of: transferring the alignment object into the cavity of the first transfer jig; and transferring the alignment object transferred into the cavity of the first transfer jig into the cavity of the second transfer jig by causing the first transfer jig and the second transfer jig to overlap each other so that the principal surfaces oppose each other.

2. The method for producing an electronic component according to claim 1, further comprising the steps of: holding the alignment object transferred into the cavity of the second transfer jig by an adhesive holding jig by pushing the alignment object transferred into the cavity of the second transfer jig against the adhesive holding jig; and immersing the alignment object held by the adhesive holding jig in a paste.

3. The method for producing an electronic component according to claim 2, wherein the second transfer jig includes a first plate member including a through hole that defines the first recess of the second transfer jig, and a second plate member which is configured to overlap the first plate member, which includes the second recess of the second transfer jig in cooperation with the first recess of the second transfer jig to define the cavity of the second transfer jig, and which is separable from the first plate member; and the method further comprises the step of, prior to holding the alignment object by the adhesive holding jig, causing the alignment object to protrude from the second recess of the second plate member that defines a portion of the cavity of the second transfer jig by separating the first plate member from the second plate member.

4. The method according to claim 1, wherein when dimensions of the alignment object are such that a thickness, a width, and a length are T, W, and L, respectively, a relationship T<W<L is satisfied.

5. The method according to claim 1, wherein the alignment object is a multilayer structure in which a ceramic layer and an internal electrode are disposed on each other.

6. The method according to claim 1, wherein the second transfer jig includes a first plate member including a through hole that defines the first recess of the second transfer jig, and a second plate member which is configured to overlap the first plate member, which includes the second recess of the second transfer jig in cooperation with the first recess of the second transfer jig to define the cavity of the second transfer jig, and which is separate from the first plate member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A and 1B each illustrate a structure of a first transfer jig of an aligning device according to a preferred embodiment of the present invention, with FIG. 1A being a plan view of a structure of, for example, a cavity of the first transfer jig and FIG. 1B being a front sectional view thereof.

(2) FIGS. 2A and 2B each illustrate a structure of a second transfer jig of the aligning device according to a preferred embodiment of the present invention, with FIG. 2A being a plan view of a structure of, for example, a cavity of the second transfer jig and FIG. 2B being a front sectional view thereof.

(3) FIG. 2C illustrates a modification of the second transfer jig of the aligning device according to the preferred embodiment of the present invention.

(4) FIG. 3 is a perspective view of a structure of an alignment object that is transferred and aligned using an aligning device according to a preferred embodiment of the present invention.

(5) FIG. 4 illustrates a method for aligning alignment objects using the aligning device according to a preferred embodiment of the present invention, in which the alignment objects are transferred in the cavities of the first transfer jig.

(6) FIG. 5 illustrates a state in which the second transfer jig is caused to overlap the first transfer jig in the state shown in FIG. 4.

(7) FIG. 6 illustrates operation effects according to a preferred embodiment of the present invention in the state shown in FIG. 5 in which the second transfer jig is caused to overlap the first transfer jig.

(8) FIG. 7 illustrates a structure of a comparative example used to describe the operation effects according to various preferred embodiments of the present invention (that is, an aligning device according to a comparative example that does not include the features according to the present invention).

(9) FIG. 8A illustrates a method for producing an electronic component using the aligning device according to a preferred embodiment of the present invention, in which the first transfer jig is removed after being reversed.

(10) FIG. 8B illustrates a state in which, when the second transfer jig according to the modification (FIG. 2C) is used, top end portions of the alignment objects are exposed (protrude) from second recesses of second plate members.

(11) FIG. 9A illustrates the method for producing an electronic component using the aligning device according to a preferred embodiment of the present invention, in which an adhesive holding jig including an adhesive material is pushed against the alignment objects and the alignment objects are held by the adhesive material of the adhesive holding jig.

(12) FIG. 9B illustrates a state in which the alignment objects are held by the adhesive material of the adhesive holding jig when the second transfer jig according to the modification (FIG. 2C) is used.

(13) FIG. 10 illustrates the method for producing an electronic component using the aligning device according to a preferred embodiment of the present invention, in which the alignment objects are transferred to the adhesive holding jig by separating the adhesive holding jig and the second transfer jig from each other.

(14) FIG. 11 illustrates the method for producing an electronic component using the aligning device according to a preferred embodiment of the present invention, in which end portions of the alignment objects are immersed in a conductive paste layer.

(15) FIG. 12 illustrates the method for producing an electronic component using the aligning device according to a preferred embodiment of the present invention, in which the conductive paste is adhered to the end portions of the alignment objects.

(16) FIG. 13 illustrates a problem in an existing aligning device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(17) Preferred embodiments according to the present invention are described by describing in further detail the features of the present invention.

(18) FIGS. 1A and 1B each illustrate a structure of a first transfer jig 10 of an aligning device according to a preferred embodiment of the present invention. FIGS. 2A and 2B each illustrate a structure of a second transfer jig 20.

(19) FIG. 3 is a perspective view of an alignment object (chip) 1 that is transferred and aligned using an aligning device according to a preferred embodiment of the present invention.

(20) In this preferred embodiment, when, as shown in FIG. 3, the thickness, the width, and the length of the alignment object (chip) 1 that is transferred and aligned are T, W, and L, respectively, the alignment object 1 preferably has a rectangular or substantially rectangular parallelepiped shape in which T is approximately 0.15 to approximately 0.10 mm, W is approximately 0.5 mm, and L is approximately 1.0 mm, and the relationship T<W<L is satisfied, for example.

(21) In this preferred embodiment, the alignment object (chip) 1 that is transferred and aligned preferably is a ceramic multilayer structure (multilayer ceramic capacitor element) that is formed by performing a process of producing a multilayer ceramic capacitor. The alignment object 1 has a structure in which internal electrodes 2 that are adjacent to each other in a stacking direction are alternately drawn out at opposing end surfaces (WT surfaces) 1a.sub.1 and 1a.sub.2.

(22) The chip (multilayer ceramic capacitor element) 1 is one in which, after the transfer and alignment steps performed using the aligning device according to a preferred embodiment, a pair of external electrodes are arranged at the end surfaces 1a.sub.1 and 1a.sub.2 so as to be brought into conduction with the internal electrodes 2 drawn out from the opposing end surfaces 1a.sub.1 and 1a.sub.2. The chip 1 is used so that, in an unfired state, the multilayer ceramic capacitor in which conductive paste for forming the external electrodes applied to the end surfaces is fired is formed.

(23) The aligning device according to this preferred embodiment used to transfer and align such an alignment object 1 includes 1) the first transfer jig 10 shown in FIGS. 1A and 1B including a cavity (accommodation recess) X into which the alignment object 1 to be transferred is transferred, and 2) the second transfer jig 20 shown in FIGS. 2A and 2B including a cavity (accommodation recess) Y into which the alignment object 1 is transferred.

(24) In this preferred embodiment, the first transfer jig 10 is preferably made of a resinous material, and the second transfer jig 20 is preferably made of a metallic material, for example. However, materials used to form the jigs are not limited thereto, so that other materials may also be used.

(25) The cavity (accommodation recess) X of the first transfer jig 10 preferably is configured in a matrix over the entire surface of the first transfer jig 10. In addition, the cavity (accommodation recess) Y of the second transfer jig 20 is preferably configured in a matrix over the entire surface of the second transfer jig 20.

(26) A pin (not shown) that engages with an engagement recess in a peripheral portion of the second transfer jig 20 is provided at a peripheral portion of the first transfer jig 10, so that positioning of the first transfer jig 10 with the second transfer jig 20 is facilitated.

(27) As shown in FIGS. 1A and 1B, the cavity X of the first transfer jig 10 includes a first recess X1 and a second recess X2. The first recess X1 opens towards a principal surface. The second recess X2 is adjacent to the first recess X1 in a depth direction and communicates with the first recess X1.

(28) The first recess X1 of the cavity X is configured preferably so as to have a substantially tapering inclined configuration and a substantially mortar-shaped configuration so as to facilitate the transfer of the alignment object 1, for example.

(29) The planar shape of the second recess X2 preferably has a substantially strip-shaped configuration whose both ends are rounded, for example. In the present preferred embodiment, the second recess X2 is configured so as to transfer a thin alignment object 1, which is to be transferred, in a predetermined orientation into the second recess X2.

(30) A through hole 11 that allows foreign material that has entered the first transfer jig 10 to drop therein is provided in a bottom of the second recess X2 of the first transfer jig 10. Foreign material that does not easily pass through the through hole 11 may be easily removed by, for example, blowing in air or inserting a thin wire or the like and scraping out the foreign material. In the present preferred embodiment, foreign material is easily removed by inserting a thin wire.

(31) The first recess X1 of the first transfer jig 10 has, in plan view, a shape and dimensions that allow the entire region of the second recess X2 to be situated within the first recess X1 by a predetermined interval (margin).

(32) In this preferred embodiment, a depth Dx of the cavity X of the first transfer jig 10 is a depth that allows a top end portion of the alignment object 1 to be exposed (to protrude) when the alignment object 1 is transferred with a WT surface being a top surface. That is, the depth Dx is a dimension that is less than a length L of the alignment object. It is desirable that the depth Dx of the cavity X of the first transfer jig 10 be a depth that allows the entire alignment object 1 to be accommodated when the alignment object 1 is transferred with a WT surface being a top surface. That is, it is desirable that the depth Dx be greater than or equal to the length L of the alignment object.

(33) In this case, when the alignment object 1 satisfies the relationship T<W<L, in particular, when the alignment object 1 is a thin object whose thickness T is less than or equal to half of W and L, it is possible to efficiently transfer the alignment object 1 to the first transfer jig 10 while suppressing and preventing cracking and chipping of the alignment object 1.

(34) However, when the alignment object 1 is accommodated in a depth that allows the entire alignment object 1 to be accommodated, it becomes difficult to push the alignment object 1 against an adhesive holding jig 40 (described below) and hold the alignment object by the adhesive holding jig 40. Therefore, in the present preferred embodiment of the present invention, the alignment object 1 is transferred to the second transfer jig 20.

(35) As shown in FIGS. 2A and 2B, the cavity Y of the second transfer jig 20 includes a first recess Y1 and a second recess Y2. The first recess Y1 opens towards a principal surface. The second recess Y2 is adjacent to the first recess Y1 in a depth direction and communicates with the first recess Y1. That is, in the second transfer jig 20, a member that defines the first recess Y1 and a member that defines the second recess Y2 are integrated with each other.

(36) However, as shown in FIG. 2C, the second transfer jig 20 may include a first plate member 20a and a second plate member 20b. The first plate member 20a includes a through hole that defines the first recess Y1. The second plate member 20b is used so as to overlap the first plate member 20a, includes the second recess Y2, and is separable from the first plate member 20a. The recess Y2 forms the cavity Y in cooperation with the recess Y1. In FIG. 2A, portions that are labelled with the same reference numerals as those in FIGS. 2A and 2B are the same or corresponding portions.

(37) As described below, in order to allow the alignment object 1 to be adhesively held by the adhesive holding jig, a depth D.sub.Y of the cavity Y of the second transfer jig is a depth that allows the top end portion of the alignment object 1 that cannot be completely accommodated to be exposed (to protrude) when the alignment object 1 is accommodated with its WT surface being a top surface. That is, the depth D.sub.Y is a dimension that is less than the length L of the alignment object.

(38) As described above, when the second transfer jig 20 is one including the first plate member 20a and the second plate member 20b that is separable from the first plate member 20a, the depth of the second recess Y2 is a depth that allows the top end portion of the alignment object 1 to be exposed (to protrude) from a top surface of the second plate member 20b when the first plate member 20a is separated from the second plate member 20b. That is, the depth of the second recess Y2 is less than the length L of the alignment object 1.

(39) The first recess Y1 of the cavity (accommodation recess) Y has a diameter that is greater than the maximum dimension of the second recess Y2 defined by a disc-shaped or substantially disc-shaped space (that is, a circular or substantially circular cylindrical space having a low height). That is, in plan view, the first recess Y1 of the second transfer jig 20 has a shape and dimensions that allow the entire region of the second recess Y2 to be situated within the first recess Y1 by a predetermined interval.

(40) The second recess Y2 preferably has a strip-shaped or substantially strip-shaped configuration with both ends rounded in plan view, for example. In the present preferred embodiment, the second recess Y2 is configured so as to allow the thin alignment object 1, which is transferred, to be held in a predetermined orientation.

(41) A through hole 21 is provided in a bottom of the second recess Y2 of the second transfer jig 20. Accordingly, even if foreign material enters the second recess Y2, the foreign material is easily removed by, for example, blowing gas from the through hole 21 or inserting a thin wire or the like and scraping out the foreign material.

(42) In plan view, the first recess Y1 of the second transfer jig 20 has a shape and dimensions that allow the entire region of the second recess Y2 to be situated within the first recess Y1 by a predetermined interval.

(43) A depth D.sub.Y1 of the first recess Y1 of the second transfer jig 20 is greater than the thickness T (which preferably is approximately 0.15 mm, for example, in the present preferred embodiment) of the alignment object 1.

(44) Here, the depth D.sub.Y1 of the first recess Y1 of the second transfer jig 20 is greater than the thickness of the alignment object 1 in order to prevent the alignment object 1 and the second transfer jig 20 from interfering with each other when the alignment object 1 is transferred.

(45) In the aligning device according to the present preferred embodiment, the first transfer jig 10 and the second transfer jig 20 are caused to overlap each other so that the principal surfaces oppose each other (desirably, contact each other), and are in a predetermined positional relationship. When, in this state, for example, vibration is applied, it is possible to transfer the alignment object 1 that has been transferred to the cavity X of the first transfer jig 10 into the cavity Y of the second transfer jig 20.

(46) Next, a non-limiting example of a method for transferring and aligning chips using the transferring device and a method for applying a conductive paste for forming external electrodes at the aligned chips are described with reference to FIGS. 4 to 12, which are schematic views.

(47) (1) First, by setting the first transfer jig 10 at a vibratory device that is capable of applying a predetermined rotation and vibration, and by applying the rotation and vibration, alignment objects 1 are transferred into cavities X of the first transfer jig 10 as shown in FIG. 4.

(48) (2) As shown in FIG. 5, the second transfer jig 20 is caused to overlap the first transfer jig 10 so that the cavities X and cavities Y oppose each other. At this time, the first transfer jig 10 and the second transfer jig 20 are positioned by engaging the pin (not shown) of the first transfer jig 10 with the engagement recess (not shown) of the second transfer jig 20.

(49) At this time, the cavities Y of the second transfer jig 20 are provided with first recesses Y1. As described above, the diameters of the first recesses Y1 are greater than maximum dimensions of the second recesses Y2 at disc-shaped or substantially disc-shaped spaces (that is, circular or substantially circular cylindrical spaces having low heights). (That is, in plan view, the first recesses Y1 have shapes and dimensions that allow the entire regions of the second recesses Y2 to be situated within the first recesses Y1.) In addition, at this time, in plan view, the first recesses Y1 of the second transfer jig 20 have shapes and dimensions that allow the entire regions of the second recesses X2 of the first transfer jig 10 to be situated within the first recesses Y1 by predetermined intervals. Therefore, as shown in FIG. 6, even if foreign material (such as broken pieces of the alignment objects 1 or the like) enter bottom portions of the cavities X of the first transfer jig 1 and top end portions of the alignment objects 1 protrude (are exposed) from the cavities X, it is possible to reliably prevent, for example, cracking and chipping of the alignment objects 1 caused by collision of the top end portions of the alignment objects 1 with inner peripheral surfaces of the cavities Y of the second transfer jig 20. That is, the diameters of the first recesses Y1 of the cavities Y of the second transfer jig 20 are greater than the maximum dimensions of the second recesses Y2 in a plane. Therefore, it is possible to efficiently align the alignment objects 1 by preventing collision of the top end portions of the alignment objects 1 with the inner peripheral surfaces of the cavities Y and cracking, chipping, and the like of the alignment objects 1. For example, such collision, cracking, chipping, and the like may occur in the case shown in FIG. 7 in which the first recesses Y1 do not exist.

(50) (3) Then, in order to reverse the positional relationship between the first transfer jig 10 and the second transfer jig 20 in the vertical direction, the first transfer jig 10 and the second transfer jig 20 are reversed through an angle of 180 degrees. In the reversed state, vibration is applied to transfer the alignment objects 1 from the cavities X of the first transfer jig 10 to the cavities Y of the second transfer jig 20. Then, the first transfer jig 10 is removed, and, as shown in FIG. 8A, the alignment objects 1 are transferred into the cavities Y of the second transfer jig with their top end portions being exposed from the cavities Y.

(51) When, as described above, the second transfer jig 20 is one including first plate members 20a and second plate members 20b that are separable from the first plate members 20a (see FIG. 2C), it is assumed that the first plate members 20a are separated from the second plate members 20b, so that, as shown in FIG. 8B, the top end portions of the alignment objects 1 are exposed (protrude) from the second recesses Y2 of the second plate members 20b.

(52) In FIG. 8B, portions that are labelled with the same reference numerals as those in FIGS. 2A and 2B are the same or corresponding portions.

(53) Then, from the bottom of the first transfer jig 10 that has been removed, thin wires or the like are inserted into the through holes formed at the bottom portions of the cavities X, to remove foreign material that has entered the cavities X. Then, preparation is made for the next transfer step. Instead of inserting thin wires into the through holes, it is possible to blow air to remove the foreign material from the cavities X.

(54) (4) Next, as shown in FIG. 9A, an adhesive holding jig 40 including an adhesive material 41 (which preferably is a sheet material having viscosity, for example) is pushed against the alignment objects 1, and one of the WT surfaces 1a.sub.1 of each alignment object 1 is held by the adhesive material 41 of the adhesive holding jig 40. Then, as shown in FIG. 10, the adhesive holding jig 40 and the second transfer jig 20 are separated from each other to transfer the alignment objects 1 to the adhesive holding jig 40.

(55) When the second transfer jig 20 is one including first plate members 20a and second plate members 20b that are separable from the first plate members 20a (see FIG. 2C), as shown in FIG. 9B, it is possible to similarly transfer the alignment objects 1 to the adhesive holding jig 40 by pushing the adhesive holding jig against the alignment objects 1 exposed from the second recesses Y2 of the second plate member 20b. In FIG. 9B, portions that are labelled with the same reference numerals as those in FIGS. 2A and 2B are the same or corresponding portions.

(56) The adhesive material 41 is a sheet adhesive material having adhesive strength and elasticity that allow the alignment objects 1 to be held. Various other materials that allow the alignment objects 1 to be adhesively held may be used as the adhesive material 41.

(57) (5) Next, as shown in FIG. 11, after immersing the other WT surface 1a2 of each alignment object 1 held by the adhesive holding jig 40 in a conductive paste layer 42, the alignment objects 1 are raised to cause the conductive paste 42a to adhere to the other WT surface 1a2 of each alignment object 1 and side surfaces near the other WT surface 1a2 as shown in FIG. 12.

(58) (6) Then, as shown in FIG. 12, with the alignment objects 1 being held by the adhesive holding jig 40, the adhered conductive paste is dried.

(59) (7) Thereafter, although not particularly illustrated, the other WT surface 1a2 of each alignment object 1 to which the conductive paste 42a has been applied is adhesively held by an adhesive holding jig using an adhesive material having an adhesive force that is higher than that of the adhesive material 41 of the adhesive holding jig 40 used in (4) above, and the alignment objects 1 are transferred. By performing the steps according to (5) and (6) above, conductive paste is adhered to the WT surface 1a1 of each alignment object 1 and the side surfaces near the WT surface 1a1.

(60) (8) Then, the chips are removed from the adhesive holding jig. Thereafter, a co-firing step in which, under a predetermined condition, firing of an unfired ceramic multilayer structures (alignment objects) and sintering of the conductive paste (external electrodes) are performed at the same time is performed. This causes, for example, the ceramic to be fired and the external electrodes to be formed at the same time.

(61) Then, by plating the external electrodes, a multilayer ceramic capacitor having a structure in which the external electrodes that are brought into conduction with internal electrodes are formed at opposing end surfaces of the chips.

(62) As described above, the frequency of occurrences of cracking, chipping, and the like were checked when alignment objects were transferred and aligned using the aligning device according to the above-described preferred embodiments of the present invention shown in FIG. 6 and the aligning device not including the first recesses Y1 shown in FIG. 7 (that is, the aligning device according to the comparative example not including the features of the present invention).

(63) The results show that, when the aligning device according to the comparative example not including the features of various preferred embodiments of the present invention (FIG. 7) was used, cracking, chipping, and the like occurred in a few alignment objects per 100,000 alignment objects that were aligned. In contrast, when the aligning device according to preferred embodiments of the present invention (FIG. 6) was used, no cracking, chipping, and the like were observed in 100,000 alignment objects that were transferred and aligned.

(64) From these results, it was confirmed that the aligning devices having the structure according to preferred embodiments of the present invention efficiently align the alignment objects while preventing cracking, chipping, and the like of the alignment objects.

(65) In the above-described preferred embodiments, the case in which the planar shapes of the second recesses X2 of the first transfer jig 10 and the second recesses Y2 of the second transfer jig 20 preferably are strip-shaped or substantially strip-shaped configurations whose both ends are rounded is described. However, the planar shapes of the second recesses X2 and Y2 are not particularly limited. They may be various shapes, such as a square or substantially square shape, a circular or substantially circular shape, or an elliptical or substantially elliptical shape.

(66) Preferred embodiments of the present invention are also applicable to the case in which alignment objects whose WT surfaces are prismatic or substantially prismatic shapes, which are square or substantially square shapes, or shapes that approximate thereto are transferred and aligned. These cases also provide the same advantages.

(67) In the above-described preferred embodiments, the case in which an alignment object is an unfired ceramic multilayer structure (multilayer ceramic capacitor element) formed by performing a process for producing a multilayer ceramic capacitor is described. However, according to various preferred embodiments of the present invention, the type of alignment object is not particularly limited. Preferred embodiments of the present invention are widely applicable to cases in which chip members and various other members formed by performing a process for producing other electronic components, such as chip inductors and chip resistors, are aligned.

(68) In the above-described preferred embodiments, the case in which an alignment object preferably is an unfired ceramic multilayer structure is described. However, the alignment object may be a fired ceramic multilayer structure.

(69) In the above-described preferred embodiments, the case in which alignment objects preferably are aligned in a step prior to applying a conductive paste is described. However, the aligning device according to the present invention is applicable to various other steps, such as a step prior to examining characteristics and a packaging step.

(70) The present invention is not limited to the above-described preferred embodiment regarding other points. Various applications and modifications may be made within the scope of the present invention regarding specific structures of the first and second transfer jigs (such as the arrangement and specific shapes, structures, dimensions, and the like of the cavities X and Y).

(71) While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.