Patent Publication Number: US-2019200452-A1

Title: Circuit board assemblies and methods of assembling circuit boards and bus bars

Description:
FIELD 
     The present disclosure relates to circuit board assemblies and methods of assembling circuit boards and bus bars. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Bus bars are often disposed on surfaces of printed circuit boards to conduct current between electrical components disposed on the printed circuit board. Separately, some electrical components have thru-hole electrical leads adapted for insertion through an opening defined by the printed circuit board. Solder is commonly used to create electrical connections between bus bars and electrical components, etc. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     According to one aspect of the present disclosure, a circuit board assembly includes a printed circuit board having a first surface and a second surface opposite the first surface. The printed circuit board defines an opening having at least one side extending from the first surface of the printed circuit board to the second surface of the printed circuit board. The assembly also includes a bus bar having a first surface, a second surface opposite the first surface, and at least one side extending from the first surface of the bus bar to the second surface of the bus bar. The bus bar is secured in the opening of the printed circuit board via a press-fit, such that a slot is defined between the at least one side of the bus bar and the at least one side of the opening defined by the printed circuit board. The assembly further includes an electrical lead positioned in the slot defined between the at least one side of the bus bar and the at least one side of the opening defined by the printed circuit board, and solder disposed between the electrical lead and the bus bar to electrically couple the electrical lead and the bus bar. 
     According to another aspect of the present disclosure, a method of assembling a printed circuit board and a bus bar is disclosed. The printed circuit board includes a first surface and a second surface opposite the first surface, and defines an opening having at least one side extending from the first surface of the printed circuit board to the second surface of the printed circuit board. The method comprises press-fitting a bus bar into the opening defined by a printed circuit board to secure the bus bar in the opening of the printed circuit board, such that a slot is defined between at least one side of the bus bar and at least one side of the opening defined by the printed circuit board. The method also includes positioning an electrical lead in the slot defined between the at least one side of the bus bar and the at least one side of the opening defined by the printed circuit board, and soldering the electrical lead to the bus bar to electrically couple the electrical lead to the bus bar. 
     Further aspects and areas of applicability will become apparent from the description provided herein. It should be understood that various aspects and features of this disclosure may be implemented individually or in combination with one or more other aspects or features. It should also be understood that the description and specific examples herein are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is an exploded perspective view of a circuit board assembly according to one example embodiment of the present disclosure. 
         FIG. 2  is a bottom view of the circuit board assembly of  FIG. 1 , with the bus bars press-fit in the printed circuit board. 
         FIG. 3  is a bottom view of the circuit board assembly of  FIG. 1 , including an electrical lead soldered to the bus bar. 
         FIG. 4  is a section view taken along line  4 - 4  in  FIG. 3 . 
         FIG. 5A  is a top view of a bus bar of the circuit board assembly of  FIG. 1 , illustrating example dimensions of the bus bar. 
         FIG. 5B  is a side view of the bus bar of  FIG. 5A . 
         FIG. 5C  is an end view of the bus bar of  FIG. 5A . 
         FIG. 6  is an exploded perspective view of a circuit board assembly according to another example embodiment of the present disclosure. 
         FIG. 7  is a bottom perspective view of the circuit board assembly of  FIG. 6 . 
         FIG. 8  is a top view of a portion of the circuit board assembly of  FIG. 6 . 
     
    
    
     Corresponding reference numerals indicate corresponding features throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     A circuit board assembly according to one example embodiment of the present disclosure is illustrated in  FIGS. 1-4 , and indicated generally by reference number  100 . As shown in  FIG. 1 , the circuit board assembly  100  includes a printed circuit board  102  having a first surface  104  and a second surface  106  opposite the first surface  104 . The printed circuit board  102  defines an opening  108  having a side  109  extending from the first surface  104  of the printed circuit board  102  to the second surface  106  of the printed circuit board  102 . 
     The assembly  100  also includes a bus bar  110  having a first surface  112 , a second surface  114  opposite the first surface  112 , and at least one side  116  extending from the first surface  112  of the bus bar  110  to the second surface  114  of the bus bar  110 . 
     As shown in  FIG. 2 , the bus bar  110  is secured in the opening  108  of the printed circuit board  102  via a press-fit. A slot  118  is defined between the side  116  of the bus bar and a side  109  of the opening  108  defined by the printed circuit board  102 . 
     Referring now to  FIG. 3 , the assembly  100  includes an electrical lead  120 . The electrical lead  120  is positioned in the slot  118  defined between the side  116  of the bus bar  110  and the side  109  of the opening  108  defined by the printed circuit board  102 . 
     Solder  122  is disposed between the electrical lead  120  and the bus bar  110  to electrically couple the electrical lead  120  and the bus bar  110 . In some embodiments, the electrical lead  120  may include a thru-hole bus bar, and the bus bar  110  may be a surface mount bus bar. 
     The bus bar  110  can be press-fit into the opening  108  of the printed circuit board  102  using any suitable press-fit approach. For example, the bus bar  110  can be press-fit into the opening  108  defined by the printed circuit board  102  using a hand press, fixtures made of aluminum and/or steel, etc. During the press-fit process a large amount of friction may be generated between teeth of the bus bar  110  and the printed circuit board  102 , but the printed circuit board  110  is typically not damaged during the press-fit process. 
     Press-fitting the bus bar  110  into the opening  108  of the printed circuit board  102  secures (e.g., retains, mechanically couples, etc.) the bus bar  110  in the printed circuit board  102 . In some embodiments, the assembly  100  may not include any adhesives coupling the bus bar  110  to the printed circuit board  102 . 
     As shown in  FIG. 4 , the bus bar  110  may be press fit into the opening  108  of the printed circuit board  102  such that the first surface  112  of the bus bar  110  is substantially coplanar with the first surface  104  of the printed circuit board  102 , and the second surface  114  of the bus bar  110  is substantially coplanar with the second surface  106  of the printed circuit board. This may facilitate even placement of an electrical component  124 , even application of the solder  122 , etc. 
     The electrical lead  120  extends beyond the second surface  114  of the bus bar  110 , and beyond the second surface  106  of the printed circuit board  102 . This allows the electrical lead  120  to be wave soldered to the bus bar  110 . For example, the printed circuit board  102  can be passed over molten solder (e.g., in a pan, etc.), and a pump can produce an upwelling of the molten solder to generate a standing wave. As the printed circuit board  102  makes contact with this wave, the electrical lead  120  is soldered to the bus bar  110 . 
     The electrically conductive solder  122  directly connects the press-fit bus bar  110  with the electrical lead  120 . This improves electrical efficiency between the bus bar  110  and the electrical lead  120 , and reduces (e.g., minimizes) interconnection losses. 
     In some embodiments, one or more electrical components may be electrically coupled to the printed circuit board  102 , with the bus bar  110  electrically coupled between the electrical lead  120  and the one or more electrical components. Therefore, the bus bar  110  can conduct current between the electrical lead  120  and the one or more electrical components. 
     As shown in  FIG. 4 , an electrical component  124  is positioned on the first surface  112  of the bus bar  110 . Because the electrical lead  120  is soldered to the second surface  114  of the bus bar  110 , the electrical lead  120  and electrical component  124  are coupled to opposite sides of the bus bar  110 . 
     The electrical component  124  is in thermal contact with the bus bar  110  to dissipate heat from the electrical component  124  to the bus bar  110 . For example, the electrical component  124  may include any suitable electrical component (e.g., electronic component, device, etc.) that generates heat during operation. Placing the electrical component  124  in thermal contact with the bus bar  110  allows the bus bar  110  to dissipate the heat generated by the electrical component  124  while the electrical component  124  is operating. The electrical component  124  may be soldered to the bus bar  110 , to allow heat transfer from the electrical component  124  to the bus bar  110  via the solder. 
     In some embodiments, the electrical component  124  can include a synchronous rectifier field-effect transistor (FET). In those cases, the synchronous rectifier FET may be a surface mount synchronous rectifier FET having a body  126  and at least one lead  128 . 
     As shown in  FIG. 4 , the body  126  of the electrical component  124  is soldered to the first surface  112  of the bus bar  110 , and the lead  128  of the electrical component  124  is soldered to one or more traces (not shown) of the printed circuit board  102 . 
       FIGS. 5A, 5B and 5C  illustrate example dimensions of the bus bar  110 . These example dimensions are for purposes of illustration only, and it should be apparent that other bus bars may include other suitable dimensions without departing from the scope of the present disclosure. 
     As shown in  FIGS. 5A and 5B , the bus bar  110  includes multiple teeth  130  positioned on a portion of the side  116  of the bus bar  110 . The multiple teeth  130  mechanically couple the bus bar  110  to the printed circuit board  102  when the bus bar  110  is press-fit into the opening  108  defined by the printed circuit board  102 . 
     The bus bar  110  may include any suitable electrically conductive material. For example, the bus bar  110  can be a copper sheet metal bus bar. In some embodiments, the bus bar  110  may conform to JIS H3100-Grade C1100 1/2H. 
       FIGS. 6-8  illustrate a circuit board assembly  200  according to another example embodiment of the present disclosure. As shown in  FIG. 6 , the circuit board assembly includes a printed circuit board  202 , and a transformer  232 . 
     The transformer  232  includes electrical leads  220 . The electrical leads  220  are inserted into slots  218  defined between the printed circuit board  202  and press-fit bus bars  210 . The electrical leads  220  of the transformer  232  are then wave soldered to the press-fit bus bars  210 . 
     The circuit board assembly  200  also includes multiple electrical components  224 . Each electrical component  224  is positioned in thermal contact with one of the bus bars to dissipate heat from the electrical component  224  to the bus bar. 
       FIG. 8  illustrates a top view of the circuit board assembly  200  prior to inserting the transformer electrical leads  220  into the slots  218 . As shown in  FIG. 8 , multiple electrical components  224  are positioned on each bus bar  210 . 
     According to another aspect of the present disclosure, a method of assembling a printed circuit board and a bus bar is disclosed. The printed circuit board includes a first surface and a second surface opposite the first surface, and defines an opening having at least one side extending from the first surface of the printed circuit board to the second surface of the printed circuit board. 
     The method includes press-fitting a bus bar into the opening defined by a printed circuit board to secure the bus bar in the opening of the printed circuit board, such that a slot is defined between at least one side of the bus bar and at least one side of the opening defined by the printed circuit board. 
     The method also includes positioning an electrical lead in the slot defined between the at least one side of the bus bar and the at least one side of the opening defined by the printed circuit board, and soldering the electrical lead to the bus bar to electrically couple the electrical lead to the bus bar. 
     In some embodiments, the electrical lead extends beyond one of the surfaces of the bus bar. In those cases, soldering the electrical lead to the bus bar includes wave soldering the electrical lead to the bus bar. 
     The bus bar may include multiple teeth positioned along at least a portion of the at least one side of the bus bar. In those situations, press-fitting the bus bar includes positioning the bus bar such that the multiple teeth mechanically couple the bus bar to the opening defined by the printed circuit board. 
     In some embodiments, the method includes electrically coupling an electrical component to the bus bar to conduct current between the electrical lead and the electrical component. The method may include positioning an electrical component in thermal contact with a surface of the bus bar to dissipate heat from the electrical component to the bus bar. 
     When the surface of the bus bar is a first surface, positioning the electrical component can include coupling the electrical component to the first surface of the bus bar, and soldering the electrical lead can include wave soldering the electrical lead to a second surface of the bus bar opposite the first surface of the bus bar. Coupling the electrical component to the first surface of the bus bar may include reflow soldering the electrical component to the first surface of the bus bar. 
     In some embodiments, the electrical component is a synchronous rectifier field-effect transistor (FET) having a body and at least one lead. In those cases, coupling the synchronous rectifier FET to the surface of the bus bar includes soldering the body of the synchronous rectifier FET to the first surface of the bus bar, and soldering at least one lead of the synchronous rectifier FET to one or more traces of the printed circuit board. 
     Press-fitting the bus bar can include press-fitting the printed circuit board without any adhesives. In some embodiments, press-fitting the bus bar can include press-fitting the bus bar such that a first surface of the bus bar is substantially coplanar with the first surface of the printed circuit board, and a second surface of the bus bar is substantially coplanar with the second surface of the printed circuit board. 
     Any of the example embodiments and aspects disclosed herein may be used in any suitable combination with any other example embodiments and aspects disclosed herein without departing from the scope of the present disclosure. For example, circuit board assemblies described herein may be assembled using other methods, methods for assembling printed circuit boards and bus bars may be used with other circuit board assemblies, etc., without departing from the scope of the present disclosure. 
     In some applications, example embodiments described herein may be used in PCB assemblies requiring interconnection between a thru-hole bus bar and a surface mount bus bar. Example electrical components can include surface mount FETs (e.g., DPAK, DPAK2, Thinpak and SOT669 devices). The example printed circuit board assemblies may include synchronous rectification circuits, bridge assist circuits, power factor correction (PFC) circuits, O-ring printed circuit board assemblies, etc. 
     Example embodiments and aspects of the present disclosure may provide any one or more (or none) of the following advantages: increased electrical efficiently via direct solder of an electrical lead to a press-fit bus bar, reduced electrical interconnection losses, reduction of space allocated to interconnection of the electrical lead and the bus bar, use of standard factory equipment and processes, etc. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.