Abstract:
A power feed device for an electrical component which improves the quality of transmission and reduces the mounting density of a printed circuit board in the power feed device or reduces the thickness of the printed circuit board and thereby realizes smaller size, provided with a power supply for supplying power, a printed circuit board having built-in signal line patterns, and a power bar having conductive projections provided in shapes and at positions corresponding to the shapes and positions of electrodes of the electrical component and provided outside of the printed circuit board, power from the power supply being supplied through the conductive projections of the power bar to electrodes of the electrical component.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims a priority of Japanese Patent Application No. 2005-286715 filed on Sep. 30, 2005, the contents of which being incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a power feed device to power pins of an electrical component, more particularly relates to a power feed device designed to feed power to various types of power pins of a ball gate array (BGA) or other electrical component from an on board power (OBP) or other power supply without going through patterns included in a printed circuit board but by instead arranging a power bar outside of the printed circuit board and going through that power bar.  
         [0004]     2. Description of the Related Art  
         [0005]     In recent years, the reduction in the noise margin of the power supply system accompanying the lower drive voltages of electrical components such as BGAs and the noise between the power and ground accompanying simultaneous switching waveforms are becoming major problems.  
         [0006]      FIG. 1A  is a plan view, seen from below, of a BGA fed with power by a conventional power feed device. In the figure,  10  indicates a BGA at the back side of which power pins  1  to  6  are arranged at predetermined positions in the row direction and column direction by solder balls. Each power pin  1  is an electrode supplied with for example a 3.3V power voltage V 1 . Each power pin  2  is an electrode supplied with for example a 3.3V reference voltage V 2 . Each power pin  3  is an electrode supplied with for example a 3.3V auxiliary power voltage V 3 . Each power pin  4  is an electrode supplied with for example a 5V power voltage V 4 . Each power pin  5  is an electrode supplied with for example a 5V reference voltage V 5 . Each power pin  6  is an electrode supplied with for example a 5V auxiliary power voltage V 6 .  
         [0007]      FIG. 1B  is a cross-sectional view showing one example of a conventional power feed device. In the figure,  12  indicates a printed circuit board arranged below the BGA  10 ,  13  indicates an OBP arranged on the printed circuit board  12  and generating a 3.3V voltage,  14  indicates an OBP arranged on the printed circuit board  12  and generating a 5V voltage,  15  indicates a copper foil power layer included in the printed circuit board  12  and forming a 3.3V power layer,  16  indicates a copper foil power layer included in the printed circuit board  12  and forming a 5V power layer,  17  indicates a via passing through the printed circuit board  12  for supplying the OBP  13  output voltage 3.3V to the power layer  15 ,  18  indicates a via passing through the printed circuit board  12  for supplying the OBP  14  output voltage 5V to the power layer  16 , and  19  to  24  are vias passing through the printed circuit board  12  corresponding to the power pins  1  to  6 . The bottom of the BGA  10  is shown by a cross-section along the dot-chain line of  FIG. 1A . The 3.3V power layer  15  is connected through the vias  19  to  21  to the power pins  1  to  3 , while the 5V power layer  16  is connected through the vias  22  to  24  to the power pins  4  to  6 .  
         [0008]     Instead of preparing the reference voltage V 2  inside the OBP  13 , a voltage output from the other OBP  14  generating the 5V voltage is divided by a voltage division circuit (formed on the printed circuit board  12 , but not shown) to prepare a 3.3V reference voltage V 2 .  
         [0009]     The BGA  10  is actually supplied with a plurality of types of power voltage and signals. For this reason, the printed circuit board  12  includes, though not shown, a plurality of other power layers and signal patterns.  
         [0010]      FIG. 2  shows one example of a circuit included in the BGA. In the figure,  22  indicates a driver and  24  a receiver. The BGA has inside it a driver circuit and a receiver circuit. The driver and the receiver are connected by connecting different BGAs. A single BGA never has the driver and receiver connected inside it. If considering this by  FIG. 2, 22  and  24  show the case of a different BGA driver circuit and receiver circuit connected by patterns on a printed circuit board. The driver  22  is supplied with the 3.3V power voltage V 1  and auxiliary power voltage V 3 , while the receiver  24  is supplied with the 3.3V power voltage V 1 . These power voltages are output from the OBP  13  and are supplied through the power layer  15  to the power pins  1  to  3 .  
         [0011]      FIG. 3  shows another example of a circuit included in the BGA. In the figure,  32  indicates a driver and  34  a receiver. The driver  32  is supplied with the 5V power voltage V 4  and the auxiliary power voltage V 6 , while the receiver  34  is supplied with the 5V power voltage V 5 . These power voltages are output from the OBP  14  and supplied through the power layer  16  to the power pins  4  to  6 .  
         [0012]     The reference voltage V 2  shown in  FIG. 2  is used as the criteria for judgment as to if the output voltage of the driver  32  of the circuit shown in for example  FIG. 3  is the high level or low level. For example, when the output voltage of the driver  32  is higher than 3.3V, it is judged that the voltage is the high level, while when it is 3.3V or less, it is judged as the low level.  
         [0013]     For reference to this related art, see Japanese Patent Publication (A) No. 2-003957, Japanese Patent Publication (B) No. 7-120227, and Japanese Patent Publication (A) No. 6-223632.  
         [0014]     In the case of a component like a BGA where a plurality of voltage power supplies are required, as shown in  FIGS. 1A and 1B , the situation where the V 1 , V 2 , and V 3  are the same voltages, but the applications differ frequently occurs in practice. In this example, the driver-receiver power voltage V 1  of  FIG. 2  is a voltage the same as the receiver reference voltage V 2  of  FIG. 3 . Further, physically, for example when using a 1 mm pitch BGA, since the distances between pins is in the narrow region of 1 mm, the pins are easily affected by each other in structure. In the circuit of  FIG. 2 , when a current I flows through the driver  22 , a noise in accordance with that current, that is, V n =LdI/dt, occurs at the power layer  15  and as a result the power layer  15  fluctuates in voltage and the reference voltage V 2  fluctuates. This being the case, the reference voltage for judging if the output voltage of the driver  32  of the circuit shown in  FIG. 3  is the high level or low level will fluctuate. For example, if the reference voltage V 2  changes to 3.5V and the output voltage of the driver  32  is 3.4V, while originally speaking the output of the driver  32  should be the high level, the change of this reference voltage causes it to be misjudged as the low level and therefore has a detrimental effect on the quality of transmission. Further, depending on the component, the component may also contain pins requiring an analog system power supply (PLL: phase-locked loop). In general, an analog system power supply is sensitive to noise, so for example even if the same voltage as the digital system power supply, physical separation is necessary. This is also one example where the voltages are the same, but the applications differ, so separation would be better.  
         [0015]     Further, there were the problem that a printed circuit board included a large number of power layers and signal layers and therefore the number of conductor layers provided in the printed circuit board was large and the dimensions became larger and the problem that if trying to make the printed circuit board smaller in thickness, the conductor layers became greater in mounting density and production became difficult. For example, when the BGA  10  is a 1152-pin field programmable gate array (FPGA), there are 3.3V Vccaux pins (eight pins), but specification-wise, these Vccaux pins have to be activated before all of the other power supplies (Vcc and Vref). For this reason, in the past, two separate layers, that is, a Vccaux power layer and a Vcco and Vref power layer, were necessary.  
       SUMMARY OF THE INVENTION  
       [0016]     An object of the present invention is to improve the quality of transmission of an electrical component.  
         [0017]     Another object of the present invention is to reduce the mounting density of conductor layers included in a printed circuit board in a power feed device so as to facilitate the production of the printed circuit board or to reduce the number of conductor layers included in a printed circuit board so as to realize a smaller size of the printed circuit board.  
         [0018]     To achieve the above object, the first aspect of the present invention provides a power feed device for an electrical component, comprising a power bar having conductive projections provided in shapes and at positions corresponding to the shapes and positions of the electrodes of the electrical component and provided at the outside of a printed circuit board and by feeding power from a power supply from the conductive projections of the power bar to electrodes of the electrical component.  
         [0019]     According to the first aspect of the present invention, since the power bar is provided at the outside of the printed circuit board, it is possible to reduce the mounting density of the printed circuit board and to simplify the production of the printed circuit board.  
         [0020]     According to a second aspect of the present invention, the printed circuit board is provided between the power bar and the electrical component, and power fed to the power bar is fed from the conductive projections through vias passing through the printed circuit board to the electrodes of the electrical component.  
         [0021]     According to the second aspect of the present invention, since the power bar is connected to the electrical component through vias of the printed circuit board, the power bar is not affected by voltage fluctuations of a power layer in the printed circuit board, therefore the quality of transmission of signals in the electrical component can be improved.  
         [0022]     According to a third aspect of the present invention, the power bar is provided between the printed circuit board and the electrical component, and power fed to the power bar is directly fed from the conductive projections to the electrodes of the electrical component without going through vias.  
         [0023]     According to the third aspect of the present invention, since the power bar is directly connected to the electrical component without going through vias of the printed circuit board, compared with the case of connection through vias, it is possible to reduce the effects of high frequency noise.  
         [0024]     According to a fourth aspect of the present invention, the power supply is at least one power supply generating at least two types of voltage, the printed circuit board includes at least one power layer for supplying part of the voltage generated by the power supply to part of the electrodes of the electrical component, and the power bar feeds one of the remaining voltages generated by the power supply to the other electrodes of the electrical component through vias passing through the printed circuit board by being electrically connected to the other electrodes and being insulated from the at least one power layer included in the printed circuit board.  
         [0025]     According to the fourth aspect of the present invention, since the power bar is insulated from the power layer in the printed circuit board, the power bar is not affected by voltage fluctuations of the power layer in the printed circuit board, therefore the quality of transmission of signals in the electrical component can be improved.  
         [0026]     According to a fifth aspect of the present invention, there are a plurality of power supplies, and there are a plurality of power bars corresponding to the electrodes of the plurality of power supplies.  
         [0027]     According to the fifth aspect of the present invention, even when there are a plurality of power supplies, since power bars corresponding to these plurality of power supplies are provided outside of the printed circuit board, it is possible to further reduce the mounting density of the printed circuit board and realize further simplification of the production of the printed circuit board.  
         [0028]     According to a still further aspect of the present invention, one power source generating one type of voltage and the electrical component are connected by a power bar, no power layer is formed in the inner layers, and the power bar alone is used to feed power, whereby it is possible to reduce the number of layers of the printed circuit board.  
         [0029]     According to a still further aspect of the present invention, one power source generating one type of voltage and the electrical component are connected by a power bar, a power layer is also formed in the inner layers, and the power bar and inner layer power layer are used to feed power in parallel, whereby it is possible to reduce any voltage drop. At that time, the vias connecting the,power bar and the electrical component are connected to the inner layer power layer. In this example, the power bar and the power layer are connected in parallel to certain power pins of the electrical component.  
         [0030]     According to a still further aspect of the present invention, one power source generating one type of voltage and the electrical component are connected by a power bar, a power layer is also formed in the inner layers, but when the voltage fed from the power bar and the voltage fed from the inner layer power layer are equal, but differ in nature (method of use, in one example, when Vref and Vcco, which are differ in nature, happen to be the same voltage 3.3V etc.), the vias connecting the power bar and the electrical component are insulated from the inner layer power layer, whereby it is possible to reduce the effect of noise. In this example, it is assumed that the electrical component has a plurality of types of power pins, one of which is fed with power from the power bar and the others of which are fed with power from the inner layer power layer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein:  
         [0032]      FIG. 1A  is a plan view, as seen from below, of a BGA fed with power by a conventional power feed device, while  FIG. 1B  is a cross-sectional view showing an example of a conventional power feed device;  
         [0033]      FIG. 2  shows an example of a circuit included in the BGA;  
         [0034]      FIG. 3  shows another example of a circuit included in the BGA;  
         [0035]      FIGS. 4A  to  4 C are views for explaining the basic configuration of a power feed device according to Example 1 of the present invention;  
         [0036]      FIG. 5  is a cross-sectional view of a power feed device according to Example 2 of the present invention.  
         [0037]      FIG. 6  is a cross-sectional view of a power feed device according to Example 3 of the present invention;  
         [0038]      FIG. 7  is a cross-sectional view of a power feed device according to Example 4 of the present invention;  
         [0039]      FIG. 8  is a cross-sectional view of a power feed device according to Example 5 of the present invention;  
         [0040]      FIG. 9  is an enlarged view showing part of  FIG. 8 ;  
         [0041]      FIG. 10A  is a plan view of a power feed device according to Example 6 of the present invention, while  FIG. 10B  is a cross-sectional view of a power feed device according to Example 6 of the present invention;  
         [0042]      FIG. 11  is a plan view of a power feed device showing an example of application of Example 6 of the present invention;  
         [0043]      FIGS. 12A  to  12 D are plan views of a power feed device according to Example 7 of the present invention, wherein  FIG. 12A  is a plan view of a BGA  10 ,  FIG. 12B  is a plan view of a power supply A side power bar,  FIG. 12C  is a plan view of a ground side power bar, and  FIG. 12D  is a power supply B side power bar; and  
         [0044]      FIG. 13A  is a plan view of a multi-power supply power bar shown in  FIGS. 12A  to  12 D, while  FIG. 13B  is a cross-sectional view of a multi-power supply power bar. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     Below, preferred embodiments of the invention will be explained in detail with reference to the attached drawings.  
       EXAMPLE 1  
       [0046]      FIGS. 4A  to  4 C are views for explaining the basic configuration of a power feed device according to Example 1 of the present invention.  FIG. 4A  is the same as the conventional view shown in  FIG. 1A  of the BGA  10  as seen from the back.  FIG. 4A  shows only the power pins  2  comprised of solder balls. Reference numeral  45  shown at the right of the BGA  10  is an OBP, while reference numeral  44  shown by the dotted lines indicates a conductive pattern formed on the back surface of the printed circuit board  49  (see  FIG. 4C ) for electrically contacting the power bar  41 .  
         [0047]      FIG. 4B  is a plan view of the power bar  40 . As illustrated, the power bar  40  is comprised of a main body part  41  of substantially the same shape as the BGA  10  and a bar part  42 . The width of the bar part  42  is shown as being narrower than the width of the main body part  41 , but does not necessarily have to be narrower. It may also be made wider when there is a reason such as keeping the voltage drop low. The main body part  41  is provided with cylindrical conductive projections  43  at positions corresponding to the power pins  2  of the BGA  10 . For simplification, the explanation will be given by an arrangement of conductive projections  43  in chip on hole (COH) mounting forming vias  48  at the same positions as the power pins  2 . When not COH mounting, the vias are not at the same positions as the footprints (not shown) of the power pins  2 , so the conductive projections  43  are formed at the same positions as not the power pins  2 , but the vias guiding patterns led out from the power pins  2  to the inner layers. The conductive projections  43  are not limited in shapes to cylinders.  
         [0048]      FIG. 4C  is a cross-sectional view of a power feed device according to Example 1. As illustrated, the output power pin  46  of the OBP  45  arranged at the right side of the printed circuit board  49  in the illustration is electrically connected to the conductive projection  44  at the end of the bar part  42  of the power bar  40  via the via  47 . At the left side of the printed circuit board  49  in the illustration, the BGA  10  is mounted. The power pins  2  of the BGA  10  are electrically connected through vias  48  passing through the printed circuit board  49  with conductive projections  43  of the main body part  41  of the power bar  40  mounted at the bottom side of the printed circuit board  49 . The main body part  41  of the power bar  40  is connected through the bar part  42  to the pattern  44  formed at the bottom side of the printed circuit board  49 . The pattern  44  is connected through the via  47  and the output power pin  46  of the OBP  45  to the OBP  45 . The BGA  10  and OBP  45  are mounted by an ordinary reflow process on the printed circuit board  49 . The power bar  40  can also be similarly mounted, but if the power bar is thick or when large in volume, it will become larger in heat capacity and may conceivably be hard to raise in temperature by the reflow heat. In this case, the power bar  40  may be fastened to the printed circuit board  49  by screws etc. The parts of the printed circuit board  49  other than the not shown signal layers and power layers are insulators.  
         [0049]     According to the basic configuration of the power feed device shown in  FIGS. 4A  to  4 C, since the power bar  40  is provided outside of the printed circuit board  49 , it becomes possible to reduce the number of the power layers inside the printed circuit board  49 .  
       EXAMPLE 2  
       [0050]      FIG. 5  is a cross-sectional view of a power feed device according to Example 2 of the present invention. In the figure, parts the same as in  FIG. 1B  are assigned the same reference numerals, and explanations are omitted. Reference numeral  51  indicates a printed circuit board,  52  a power layer of conductive patterns included in the printed circuit board,  53  to  55  vias passing through the printed circuit board  51 ,  56  a power bar provided outside of the printed circuit board  51  according to the present invention,  45  an OBP,  57  an output power pin of the OBP  45 ,  58  a conductive pattern arranged on the printed circuit board  51  and electrically connected with the output power pin  57 ,  59  a planar pattern electrically connected with the conductive pattern  58 ,  60  a via electrically connecting the planar pattern  59  and the power bar  56 , and  561  conductive projections provided at the power bar  56  and connecting to the vias  53 . The via  60  passes through the printed circuit board  51  and is insulated from the power layer  52  included in the printed circuit board  51 . The parts of the printed circuit board  51  other than the power layer  52  and not shown signal layers and other power layers are insulators.  
         [0051]     Each power pin  2  is fed with power from the OBP  45  through the output power pin  57 , conductive pattern  58 , planar pattern  59 , via  60 , power bar  56 , a conductive projection  561 , and a via  53 . Each of the power pins  1  and  3  is fed with power from the OBP  45  through a not shown conductive path, the power layer  52  in the printed circuit board  51 , and vias  54  and  55 . In this example, the power pin  2  and power pins  1  and  3  are in the end fed with power from the same OBP  45 , so are not completely electrically insulated from each other, but are connected at an electrically distant location, so for example for noise occurring at a power pin  1  to reach a power pin  2 , it would have to make a considerable detour of the via  55 →power layer  52 →OBP  45 →via  60 →power bar  56 →projection  561 →via  53 →power pin  2 . This route includes inductance components, so high frequency noise would find it hard to follow along this route and the noise would not be a substantive problem in level.  
         [0052]     According to this configuration, the voltage applied to each power pin  2  becomes completely free of the effect of any fluctuation in the voltage applied to the power pins  1  and  3 . Therefore, even if utilizing the voltage applied to a power pin  2  as the reference voltage for judging if the output of a driver of a circuit in the BGA  10  is the high level or low level, it is possible to avoid the misjudgment like in the past.  
       EXAMPLE 3  
       [0053]      FIG. 6  is a cross-sectional view of a power feed device according to Example 3 of the present invention. In the figure, parts the same as in  FIG. 5  are assigned the same reference numerals, and explanations are omitted. In Example 3, a power layer  62  inside the printed circuit board  61  and a power bar  63  provided outside the printed circuit board  61  are connected in parallel by vias  64  and  65 . That is, at the right side of the power bar  63  in the illustration, the surface  59  connected with the lead  57  of the OBP  45  by the pattern  58  and the footprint  631  of the power bar  63  are connected by the via  65  passing through the printed circuit board  61 , and this via  65  is connected to the power layer  62  included in the printed circuit board  61 . At the left side of the power bar  63  in the illustration, conductive projections  632  of the power bar  63  and power pins  2  of the BGA  10  are electrically connected through the vias  64 . Due to this parallel connection, it becomes possible to reduce the apparent electrical resistance of the power layer  62 . For example, when the power layer  62  and the power bar  63  are the same in lengths and the power layer  62  has a thickness in cross-section of 35 μm and a width of 285 mm, if using a power bar  63  with a width in cross-section of 5 mm and a thickness of 2 mm, the cross-sectional area becomes the same, so the power layer  62  and the power bar  63  become the same in resistance value. If connecting these in parallel, the electrical resistance becomes half that of the case of the power layer  62  alone. Due to this, the voltage drop of the power layer  62  is halved. The power bar may be freely selected in width and thickness.  
       EXAMPLE 4  
       [0054]      FIG. 7  is a cross-sectional view of a power feed device according to Example 4 of the present invention. In the figure, parts the same as in  FIG. 5  are assigned the same reference numerals, and explanations are omitted. In Example 4, a power bar  71  and ground bar  72  are provided between the BGA  10  and the printed circuit board  70 . The power bar  71  and the ground bar  72  are electrically separated by an insulating layer  73 . The BGA  10  is provided with not only reference voltage power pins  2 , but also ground use power pins  74  and signal transmission use signal pins  75 . Reference numeral  76  shows connection pins for connecting the signal pins  75  to a signal layer (not shown) included in the printed circuit board  70 , while  77  shows insulators for electrically insulating the signal pins  75  from the power bar  71  and ground bar  72 . The connection pins  76  are cylindrically shaped, while the insulators  77  are shaped as hollow tubes able to surround them. The signal pins  75  of the BGA  10  are connected through connection pins  76  passing through the power bar  71  and insulation layer  73  and ground bar  72  to the vias  78 . The power bar  71 , ground bar  72 , and insulating layer  73  are formed with holes of passage of the signal pins  76 . The vias  78  are connected with a signal layer (not shown) in the printed circuit board  70 . The connection pins  76  are connected to the vias  78  by reflow soldering, or the power bar  71  and ground bar  72  themselves are fastened by screws (not shown) to the printed circuit board  70  for connection to the signal layer included in the printed circuit board  70 .  
         [0055]     Due to this configuration, the power bar and ground bar also are directly connected to the BGA  10  without going through vias of the printed circuit board, so there is an effect of reduction of the high frequency noise. In general, vias in a printed circuit board have large inductances in the high frequency region and pose major problems even when the printed circuit board is at most 2 mm or so in thickness. Since the power bar is directed connected to the BGA  10  without going through the printed circuit board (that is, the vias), this is extremely effective as a measure against high frequency noise.  
       EXAMPLE 5  
       [0056]      FIG. 8  is a cross-sectional view of a power feed device according to Example 5 of the present invention. In the figure, parts the same as in  FIG. 7  are assigned the same reference numerals, and explanations are omitted. A power bar  71  is made from copper or another metal originally having a high electric conductivity, so by providing part of the power bar  71  with at least one of plate type heat radiating fins  81  and disk type heat radiating fins  82 , it is possible to obtain a heat radiating structure. Further, if providing part of the plate type heat radiating fins  81  with slits  83  to enable part of the disk type heat radiating fins  82  to slide, a further larger heat radiating effect is obtained.  
         [0057]      FIG. 9  is an enlarged view showing an example of providing part of the plate type heat radiating fins  81  explained in  FIG. 8  with slits  83  to enable part of the disk type heat radiating fins  82  to slide.  
       EXAMPLE 6  
       [0058]      FIG. 10A  is a plan view of a power feed device according to Example 6 of the present invention, while  FIG. 10B  is a cross-sectional view of a power feed device according to Example 6 of the present invention. In  FIGS. 10A and 10B , reference numerals  101  and  102  indicate main body parts of a power bar,  103  an arm part of the power bar,  104  a conductive projection provided at a position corresponding to the, for example, Vref power pin of a BGA on the main body part  101  of the power bar,  105  a conductive projection provided at a position corresponding to the for example Vref power pin of the BGA on the main body part  102  of the power bar,  106  a screw hole for connecting an end of the arm part  103  and the main body part  101  of the power bar and forming a female screw structure,  107  a screw for connecting the end of the arm part  103  and the main body part  102  of the power bar,  108  a conductive pattern connected to the end of the arm part  103 ,  109  a printed circuit board,  110  a via connecting an output power pin  111  of the OBP  45  and the conductive pattern  108 ,  112  an electrical component as constituted by the BGA,  113  a for example Vref power pin of the BGA, and  114  a via for electrically connecting a power pin  113  and conductive projection.  
         [0059]     As shown in  FIGS. 10A and 10B , according to Example 6, the main body parts and the arm parts of the power bar are produced separately and the arm parts  103  can be screwed to the desired main body parts in accordance with need. Conversely speaking, in the power feed devices from Examples 1 to 5, it was necessary to prepare a different shaped power bar each time the positions of the BGA and the OBP changed, but in Example 6, by separately preparing the main body parts and arm parts of the power bar, no matter what the positional relationship between the BGA and OBP, it becomes possible to use the same main body parts.  
         [0060]      FIG. 11  is a plan view of a power feed device showing an example of application of Example 6. In the figures,  115  to  117  indicate three main body parts of the power bar, while  118  to  120  indicate three arm parts. In this way, even when the main body parts  115  to  117  of the power bar are arranged at positions different in direction and distance with respect to the OBP  45 , by making the arm parts of the power bar lengths matching the positions of these main body parts, it becomes possible to connect the OBP  45  and the main body parts of the power bar arranged at any positions.  
       EXAMPLE 7  
       [0061]      FIGS. 12A  to  12 D are plan views of a power feed device according to Example 7 of the present invention. In the figures,  FIG. 12A  is a plan view of a BGA  10 ,  FIG. 12B  is a plan view of a power supply A side power bar,  FIG. 12C  is a plan view of a ground side power bar, and  FIG. 12D  is a plan view of a power supply B side power bar. In this way, in the present example, a single BGA has two power supplies  122  (A) and  123  (B) connected to it.  
         [0062]     The BGA  10  shown in  FIG. 12A  is the same as that shown in  FIGS. 1A and 1B  and is provided with ground pins  1 , power pins  2 , and power pins  3 .  
         [0063]     In  FIG. 12B, 124  indicates a power bar connected to a power supply A side  122  and provided at its main body part with cylindrical conductive projections  125  corresponding to the power pins  3 , holes  126  corresponding to the ground pins  1 , and holes  127  corresponding to the power pins  2 .  
         [0064]     In  FIG. 12C, 128  indicates a ground side power bar connected to the power supply A side  122  and provided at its main body part with cylindrical conductive projections  129  corresponding to the ground pins  1  and holes  130  corresponding to the power pins  2 .  
         [0065]     In  FIG. 12D, 131  indicates a power bar connected to the power supply B side  123  and provided at its main body part with cylindrical conductive projections  132  corresponding to the power pins  2 . By superposing these three power bars  124 ,  128 , and  131 , a multi-power supply power bar can be realized.  
         [0066]      FIG. 13A  is a plan view of the multi-power supply power bar shown in  FIGS. 12A  to  12 D, while  FIG. 13B  is a cross-sectional view of a multi-power supply power bar as seen from the arrow A direction in  FIG. 13A . As will be understood from  FIG. 13A , the bar parts of the power bars are arranged offset in the lateral direction. In  FIG. 13B, 133  indicates an insulating layer between the power bar  124  and the main body part of the power bar  128 ,  134  indicates an insulating layer between the power bar  128  and the main body part of the power bar  131 , and  135  indicates a printed circuit board. The conductive projections  125  are connected through vias  136  of the printed circuit board  135  to the power pins  3 , the conductive projections  129  are fit into the holes  126  and connected through the vias  136  to the ground pins  1 , and the conductive projections  132  are fit into the holes  127  and connected through the vias  136  to the power pins  2 . The cylindrical shaped surroundings of the holes  126  corresponding to the ground pins  1  are electrically insulated from the power bar  124  by air insulation or insulating layers. Similarly, the cylindrical shaped surroundings of the holes  130  corresponding to the power pins  2  are electrically insulated from the power bar  124  and ground side power bar  128  by air insulation or insulating layers. In the example shown in  FIGS. 12A  to  12 D and  FIGS. 13A and 13B , the case of two power supplies is shown, but even if the number of power supplies is three or more, this can be similarly dealt with by adding power bars under the printed circuit board  132  and holes in the power bars superposed with the same.  
         [0067]     As clear from the above explanation, according to the present invention, by arranging a power bar at the outside of a printed circuit board, it is possible to reduce the number of power layers included in the printed circuit board and thereby possible to reduce the mounting density of the printed circuit board and simplify the production of the printed circuit board. Further, the power bar is free from the effects of any voltage fluctuations of a power layer in the printed circuit board and therefore the quality of transmission of the signals in the electrical component can be improved. Further, by having the power bar directly connected to the electrical component without going through vias of the printed circuit board, compared with the case of connection through vias, it is possible to reduce the effect due to high frequency noise. Further, since the power bar is insulated from the power layer in the printed circuit board, the power bar is free from the effects of any voltage fluctuations in the power layer in the printed circuit board and therefore the quality of transmission of the signals in the electrical component can be improved. Further, even if there are a plurality of power supplies, since power bars corresponding to the plurality of power supplies are provided outside of the printed circuit board, the mounting density of the printed circuit board can be further reduced and the production of the printed circuit board can be further simplified.  
         [0068]     While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.