Abstract:
An anchoring member and related method are disclosed for substantially parallel assembly of two additional daughter printed circuit boards (PCB) and heat sink on each side of main of mother PCB, and to retain a predetermined mating distance thereto to retain a predetermined mating distance thereto. The anchoring member comprises an elongated body extending in a longitudinal direction and having a first coupling member on one end for coupling the first daughter board in a substantially perpendicular orientation to the longitudinal direction on a first side of the mother board. The elongated body also comprises a second coupling member at the opposite end from the elongated body from the first coupling member for coupling the second daughter board in a substantially perpendicular orientation to the longitudinal direction on a second side of the mother board. The elongated body also has a positioning flange for positioning the elongated body in an aperture of the mother board at an inserted position and a friction fit surface for interacting with the aperture of the mother board to secure the elongated body in the inserted position.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority to and the benefit of Canadian Application No. 2.552,620, filed on Jul. 20, 2006. 
   FIELD OF THE INVENTION 
   The present invention relates to the field of printed circuit boards (“PCB”). More particularly, the present invention relates to devices and methods for fastening daughter boards in parallel relation to mother boards a predetermined distance apart. 
   BACKGROUND OF THE INVENTION 
   In the past, there have been many different types of PCBs. Furthermore, the PCBs can be arranged and connected together in arrangements, sometimes referred to as mother board and daughter board arrangements. Typically, a mother board is a main PCB and a daughter board is a peripheral or secondary PCB, usually smaller in size than the mother board and physically and electrically connected thereto. 
   Typically, a daughter board is arranged in a perpendicular fashion to the mother board. However, a daughter board can also be arranged in a parallel fashion to a mother board. In general, a structural device is used to facilitate fastening of the daughter board to the mother board. The daughter board may be electrically connected to the mother board in any known manner. 
   Typically, daughter boards are oriented on one side of the mother board, whether the daughter boards are arranged in parallel, or, perpendicular to the mother board. Because of this, many devices used to facilitate fastening of the daughter board to the mother board have a single active side which can be coupled to the daughter board. However, in some cases, it is necessary to have daughter boards present on both sides of a mother board. 
   The prior art has suffered from several disadvantages. In particular, prior art devices have generally been one sided, meaning that each structural device can only secure a daughter board to one side of a mother board. This means that if daughter boards are to be arranged on both sides of a mother board, several individual structural devices must be used, each facing in different directions. Clearly, this can increase the cost because of the number of structural elements required to secure the daughter boards to the mother boards. Furthermore, this can greatly increase the amount of area, also referred to as “real estate”, used on the mother board because, whether or not a structural element is used to secure a mother board to one side or the other side of the mother board, the area or real estate on the mother board used by the structural element is gone and cannot be used for other elements or purposes. Furthermore, the additional elements present on a mother board increase the complexity of the wiring circuit printed on the mother board thereby increasing the overall cost to design and build a mother board. 
   In addition, in some cases, daughter boards are designed to have holes which mate with the structural element. In such cases, where the daughter boards are to be designed for more than one use, or more than one orientation, several holes must be present on the daughter board in order to accommodate the different possible locations and orientations of the structural elements on the mother board. This also decreases the available area or real estate available for use on the daughter board. This also increases the complexity of the wiring circuit printed on the daughter board. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of this invention to at least partially overcome some of the disadvantages of the prior art. Also, it is an object of this invention to provide an improved type of structural element for securing daughter boards on both sides of a mother board and in parallel thereto. 
   Accordingly, in one of its aspects, this invention resides in an anchoring member for facilitating fastening a first daughter board, said first daughter board having at least one circuit element thereon, to a first side of a mother board, said mother board having at least one circuit element thereon, and for facilitating fastening of a second daughter board, said second daughter board having at least one circuit thereon, to a second side of the mother board, said second side of the mother board being opposed from said first side of the mother board, said anchor member comprising: an elongated body extending in a longitudinal direction; a first coupling member for coupling the first daughter board to the elongated body substantially perpendicularly to the longitudinal direction; a second coupling member for coupling the second daughter board to the elongated body substantially perpendicularly to the longitudinal direction; a friction fit surface for securing the elongated body to the mother board; a positioning flange for positioning the elongated body in an inserted position in the mother board; wherein the elongated body can be inserted into an aperture of the mother board in the longitudinal direction to the inserted position where the positioning flange abuts the first side of the mother board and the friction fit surface interacts with the aperture to secure the elongated body in the inserted position; wherein, when the elongated body is in the inserted position, the first coupling member can couple the first daughter board to the elongated body on the first side of the mother board, and the second coupling member can couple the second daughter board to the elongated body on the second side of the mother board, with the first daughter board, mother board and second daughter board being arranged in substantially parallel arrangement. 
   In a further aspect, the present invention resides in a method of fastening a first daughter board having at least one circuit element thereon to a first side of a mother board, said mother board having at least one circuit element thereon, and for fastening a second daughter board having at least one circuit thereon, to a second side of the mother board, said second side of the mother board being opposed from said first side of the mother board, said method comprising: inserting an elongated body into the aperture until a friction fit surface on the elongated body interacts with the aperture at an inserted position, said elongated body extending in a longitudinal direction; coupling the first daughter board to a first coupling member substantially perpendicularly to the longitudinal direction at a first end of the elongated body; coupling the second daughter board to a second coupling member substantially perpendicularly to the longitudinal direction at the second end of the elongated body, said first end being positionally opposed from said second end; wherein the elongated body is inserted into the aperture in the longitudinal direction with the second end first; wherein the first daughter board, mother board and second daughter board are arranged in substantially parallel arrangement. 
   In a still further aspect, the present invention resides in a printed circuit board assembly comprising: a mother board having a first side and second side and at least one aperture; an elongated body extending in a longitudinal direction and secured in said aperture, said elongated body having a first coupling member at a first end and a second coupling member at a second end, said second end positionally opposed from said first end in the longitudinal direction; a first daughter board having at least one electric circuit, said first daughter board coupled to the elongated body substantially perpendicularly to the longitudinal direction with the first coupling member; a second daughter board having at least one electric circuit thereon, said second daughter board coupled to the elongated body substantially perpendicularly to the longitudinal direction with the second coupling member; wherein the first daughter board and second daughter board are fastened to the mother board in a substantially parallel arrangement with the first daughter board on the first side of the mother board and the second daughter board on the second side of the mother board. 
   Accordingly, one advantage of at least one aspect of the present invention is that the a single anchoring member can be used to secure daughter boards to either side of a mother board and in parallel arrangement thereto. This can decrease the real estate used on the mother board because a single structural element can be used to secure two different daughter boards to the same mother board. This can also decrease the complexity of the overall circuit on the mother board by decreasing the number of apertures that must be incorporated into the mother board for securing the daughter boards thereto. 
   A further advantage of at least one aspect of the present invention is that the cost of manufacture can be decreased in that a single structural element can be used to secure two daughter boards, thereby decreasing the assembly costs as well as the material costs. 
   A further advantage of at least one aspect of the present invention is that the design of the daughter boards can be made more symmetrical, particularly where the daughter boards perform the same function. In this way, a single aperture, or other fastening device, can be used on a daughter board rather than having separate apertures or fastening devices in different locations on the daughter board corresponding to the different possible locations a corresponding structural element on a mother board could fasten to a daughter board depending on the orientation of the daughter board. Similarly, if the same structural element is also to be used for a heat sink, such as an aluminium plate, a single offsetting hole or other fastening element can be used to fasten the heat sink to the structural element on the mother board regardless of the orientation of the aluminium board with respect to the mother board during manufacture. 
   Further aspects of the invention will become apparent upon reading the following detailed description and drawings, which illustrate the invention and preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, which illustrate embodiments of the invention: 
       FIG. 1  is a diagram illustrating the anchoring member according to one aspect of the present invention; 
       FIG. 2  is a diagram illustrating in cross section the anchoring member according to one aspect of the present invention fitted onto a main PCB; 
       FIG. 3  is a diagram illustrating the assembly of two daughter PCBs with RJ45 connectors placed on the top and bottom of the main PCB; 
       FIG. 4  is a diagram illustrating the assembly of two daughter PCBs with fiber optic transceivers placed on the top and bottom of the main PCB; 
       FIG. 5  is a diagram illustrating the assembly of two daughter PCBs placed on the top and bottom of the main PCB; 
       FIG. 6  is a diagram illustrating the assembly of two daughter PCBs and a heat sink on top of each PCB and secured using blind threaded standoffs; 
       FIG. 7  is a diagram illustrating the side view of the assembly shown in  FIG. 6 ; and 
       FIG. 8  is a diagram illustrating the assembly of two daughter PCBs with fiber optic transceivers placed on top and bottom of a main PCB installed in an Intelligent Electronic Device (IED). 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the invention and its advantages can be understood by referring to the present drawings. In the present drawings, like numerals are used for like and corresponding parts of the accompanying drawings. 
   As shown in  FIG. 1 , one embodiment of the present invention relates to a structural element and, in particular, an anchoring member, shown generally by reference numeral  100 , for facilitating fastening a first daughter board  1  and a second daughter board  2  in parallel arrangement on either side of a mother board  3 . The anchoring member  100  comprises, in one preferred embodiment, an elongated body  102  extending in a longitudinal direction, indicated generally by the arrow identified with the symbol Ld. 
   Preferably, the anchoring member  100  comprises a friction fit surface, as shown generally by reference numeral  103 , for securing the elongated body  102  to the mother board  3 . The friction fit surface  103  can be any type of surface which can secure the elongated body  102  to the mother board  3  and may include a screw bore arrangement, an adhesive surface, a chemical reaction, such as a thermosetting resin or epoxy, or heat shrinking. In a preferred embodiment, as illustrated in  FIG. 1 , the friction fit surface  103  comprises serrated edges  104 . 
   Preferably, the friction fit surface  103  extends along the longitudinal direction Ld of the elongated body  102  a distance comparable to the thickness t of the mother board  3 . In a further preferred embodiment, the elongated body  102  is cylindrical in shape, as illustrated in  FIG. 1 , but it is understood that the elongated body  102  may have any other elongated shape including oval, triangular, rectangular or square. In the preferred embodiment, where the elongated body  102  is cylindrical in shape, the serrated surface  104  will extend along at least a portion, and preferably all, of the circumference C. 
   As also illustrated in  FIG. 1 , the elongated body  102  preferably has a positioning flange  108 . In a preferred embodiment, the positioning flange  108  is adjacent the friction fit surface  103  and abuts against the first side  31  of the mother board  3  when the elongated body  102  is in the inserted position. Preferably, the positioning flange  108  extends radially out for at least a portion of the circumference C, and more preferably all of the circumference C, of the elongated body  102 . In this way, the positioning flange  108  can abut against the first surface  31  of the mother board  3  along a larger surface area to better ensure that the elongated body  102  has been inserted into the inserted position and to avoid potential damage to the mother board  3  during this insertion. 
     FIG. 2  illustrates the elongated body  102  in the inserted position. As illustrated in  FIG. 2 , the elongated body has been inserted into an aperture  33  in the mother board  3 . This can be accomplished, for instance, by the elongated body  102  being inserted, such as by press fitting, in the longitudinal direction Ld into the aperture  33  of the mother board  3  until the position flange  108  abuts the first surface  31  of the mother board  3 . In this inserted position, the friction fit surface  103 , in this case being the serrated edges  104 , interact with the aperture  33  to secure the elongated body  102  in the inserted position. 
   The anchoring member  100  also preferably comprises a first coupling member  111  for coupling the first daughter board  1  to the elongated body  102  substantially perpendicularly to the longitudinal direction Ld. The anchoring member  100  also preferably comprises a second coupling member  112  for coupling the second daughter board  2  to the elongated body  102  substantially perpendicularly to the longitudinal direction Ld. By substantially perpendicularly is meant substantially perpendicular or normal to a plane defined by the first daughter board  1  or second daughter board  2 , as the case may be. In a preferred embodiment, the first coupling member  111  is located at a first end  131  of the elongated body  102  and the second coupling member  112  is located at a second end  132  of the elongated body  102 . The first end  131  is preferably positionally opposed in the longitudinal direction Ld from the second end  132 . 
   As also illustrated in  FIGS. 1 and 2 , the first coupling member  111  and the second coupling member  112  may comprise a first fastening member  121  and a second fastening member  122 , respectively. In one preferred embodiment, the first fastening member  121  and the second fastening member  122  can comprise a first threaded bore  123  and a second threaded bore  124  illustrated in  FIG. 1 . The first threaded bore  123  and the second threaded bore  124  may have a set depth, or, may be part of a threaded bore extending within the elongated body  102  in the longitudinal direction Ld. In either case, the first threaded bore  123  and the second threaded bore  124  may receive a first threaded screw  125  and a second threaded screw  126 , respectively, as illustrated, for instance, in  FIG. 3 . The first threaded screw  125  and the second threaded screw  126  may pass through a first coupling member  111  in the first daughter board  1  and a second coupling member  112  in the second daughter board  2 , respectively. 
   In this preferred embodiment, the fastening members  121 ,  122  will fasten the daughter boards  1 ,  2  as illustrated, for instance, in  FIG. 3 . However, it is understood that any other type of coupling members  111 ,  112  could be used and the present invention is not restricted to fastening members  121 ,  122  comprising threaded bores  123 ,  124  and corresponding threaded screws  125 ,  126 . For example, the coupling members  111 ,  112  could include serrated surfaces (not shown), a heat shrink arrangement, an adhesive, a chemical reaction including thermosetting resins such as epoxy, and any other type of device or means for coupling the daughter boards  1 ,  2  to the elongated body  102 . 
   As also illustrated in  FIG. 3 , when the elongated body  102  has been inserted in the inserted position, the first coupling member  111  can couple the first daughter board  1  to the elongated body  102  at a first distance D 1  from the first surface  31  of the mother board  3 . The second coupling member  112  can couple the second daughter board  2  to the elongated body  102  at the second distance D 2  from the second side  32  of the mother board  3 . As also illustrated in  FIG. 3 , the first daughter board  1 , the mother board  3  and the second daughter board  2  will be arranged in substantially parallel arrangement. As also illustrated in  FIG. 3 , the daughter boards  1 ,  2  may have at least one circuit element thereon, shown generally by reference numbers  12  and  22 , respectively. The at least one circuit elements  12 ,  22  in  FIG. 3  are shown to be RJ-45 connectors  250 , but any type of circuit elements  12 ,  22  could be used. The mother board  3  may also comprise at least one circuit elements, shown generally by reference numeral  34  in  FIG. 2 , but the mother board  3  need not necessarily have a circuit element  34  and could just act as a member to which the anchoring member  10  facilitates fastening by the daughter boards  1 , 2 . 
   It is understood that the first distance D 1  and the second distance D 2  may be substantially equal. Alternatively, the first distance D 1  and the second distance D 2  may be different. In either case, the length of the elongated body  102  in the longitudinal direction Ld can be adjusted to accommodate any distance D 1 , D 2 , whether they are the same or different. 
   As also illustrated in  FIG. 2 , and discussed above, in a preferred embodiment, the positioning flange  108  is adjacent to the friction fit surface  103 . In this way, assembly of the anchoring member  100  into the mother board  3  is facilitated by simply press fitting the elongated body  102  into the aperture  33  of the mother board  3  by pushing the elongated body  102  in the longitudinal direction Ld into the aperture  33  until the positioning flange  108  abuts the first side  31  of the mother board  3 . Preferably, the second end  132  is inserted into the aperture  33  first. Because the positioning flange  108  is preferably adjacent the friction fit surface  103 , the friction fit surface  103  will interact with the edges of the aperture  33  in the mother board  3  to secure the elongated body in the inserted position when the positioning flange  108  abuts the first side  3  of the mother board  3 . 
   In this inserted position, the distance from the positioning flange  108  that is abutting the first side  33  of the mother board  3  to the first coupling member  111  will correspond to a first length L 1  which will be related to the first distance D 1 . Similarly, when in the inserted position, the distance from the positioning flange  108  to the second coupling member  112  in the longitudinal direction Ld will correspond to the second length L 2  and be related to the second distance D 2  plus the thickness t of the mother board  3 . This is the case because the positioning flange  108  abuts the first side  31  of the mother board  3  while the second daughter board  2  is to be placed a distance D 2  from the second side  32  of the mother board  3 . 
     FIG. 4  illustrates a further preferred embodiment where heat sinks, shown generally by reference numeral  50 , are attached to the coupling members  111 ,  112 . This can be accomplished in a preferred embodiment as illustrated in cross-section in  FIG. 6  by having a first standoff pin  127  and a second standoff pin  128  inserted into the first threaded bore  123  and the second threaded bore  124  instead of threaded screws  125 ,  126 . The standoff pins  127 ,  128  in this embodiment comprise modified first and second fastening members  121 ,  122  in that they replace the threaded screws  125 ,  126  referred to above. Similarly, the standoff pins  127 ,  128  may receive counter sink screws  57  to connect heat sinks  50  to the standoff pins  127 ,  128  which, in turn, are connected to the anchoring member  100 . This can be used, for example, to structurally secure a heat sink  50  to the at least one circuit elements  12 ,  22  on the daughter boards  1 ,  2 . 
   Preferably, if the daughter boards  1 ,  2  have at least one circuit element  12 ,  22 , which comprise fiber optic transceivers  40 , then a heat sink  50  is preferred to assist in dissipating the heat generated by the fiber optic transceivers  40 , and any other of the circuit thermally conductive plates, such as aluminium, which conducts heat away from a heat source. 
     FIG. 8  illustrates daughter boards  1 ,  2  assembled to a mother board  3  and inserted in an IED  200 . For convenience, the front cover of the IED  200  has been removed from  FIG. 8 . As illustrated in  FIG. 8 , the heat sink  50  are preferably in thermal contact with the casing  202  of the IED  200  in order to facilitate dissipation of the heat generated. 
   The heat sink  50  is also arranged in parallel arrangement to the mother board  3  as well as the daughter boards  1 ,  2 . This is understood because the heat sinks  50  can best operate to dissipate heat when they are in contact with a large surface area of the heat generating elements, in this embodiment the fiber optic transceivers  40 . Furthermore, as illustrated in  FIG. 8 , in order to dissipate energy away from the heat generating components, the heat sinks  50  must also be in contact with the large surface area of the outer case  220  of the IED  200 . 
     FIG. 8  also illustrates how an IED  200  can have a large port density per area, which means that there are a large number of ports  210 , in a small area and all on one side of the IED  200  using the anchor member  100  according to one embodiment of the present invention. The IED  200  can be designed to have a larger number of ports  210  per area because the anchor member  100  facilitates fastening the daughter boards  1 ,  2  in parallel arrangement on either side  31 ,  32  of the mother board  3  to increase the number of ports  210  per area. Furthermore, as also illustrated in  FIG. 8 , the heat sinks  50  can also be arranged in a more efficient arrangement. This can give the IED  200  a more sleek design and also a more efficient use of space. It is also understood that the daughter boards  1 ,  2  could be separated from the first side  31  and the second side  32  of the mother board  3  by different distances D 1 , D 2  which could permit customization of the ports  210  in the IED  200 . 
   It is also understood that in cases where the daughter boards  1 ,  2  have a circuit element  12 ,  22  that does not generate a great deal of heat, then a heat sink  50  may not be necessary. For instance,  FIG. 3  illustrates an embodiment of the present invention where RJ-45 connectors  250  are used. Typically, the RJ-45 connectors  250  do not generate a large amount of heat. If the assembly shown in  FIG. 3  is inserted in an IED  200 , then heat sinks  50  would generally not be necessary. This would also decrease the area of the IED  200  and increase the port density per area because the thickness associated with the heat sinks  50  would be avoided. 
   It is understood that while a preferred embodiment would relate to use of this invention to improve the orientation of daughter boards  1 ,  2  with respect to a mother board  3  where the daughter boards  1 ,  2  comprise RJ-45 connectors  250  and/or fiber optic transceivers  40 , the invention is not so limited. As illustrated in  FIG. 5 , the daughter boards  1 ,  2  may have any type of circuit element  12 ,  22  associated therewith. 
   It is also understood that while the description above has been made with respect to an anchor member  100 , it is understood that the daughter boards  1 ,  2  may be secured to the mother board  3  with more than one anchor member  100 . In particular,  FIG. 7 , which is a side view of the assembly shown in  FIG. 6 , better illustrates that the daughter boards  1 ,  2  are, in fact, coupled to separate anchor devices, identified by reference numerals  100   a ,  100   b , for ease of reference. In this way, the daughter boards  1 ,  2  as well as the heat sinks  50  can be more securely fastened to the mother board  3 . In a further preferred embodiment, the first side  31  of the mother board  3  faces upwards, against gravity, when the mother board  3  has been installed in an IED  250 . In this way, the positioning flange  108  can provide additional support for the first and second daughter boards  1 , 2 . This is also true when heat sinks  50  are also coupled to the elongated body  102 . 
   Accordingly the anchoring member  100  of the present invention facilitates fastening of a first daughter board  1 , a mother board  3  and a second daughter board  2  in substantially parallel arrangement. The anchoring member  100  may also be used to facilitate fastening of the heat sinks  50 , also in parallel arrangement with the mother board  3  and daughter boards  1 ,  2 . Moreover, the present anchoring member  100  facilitates fastening of the heat sinks  50  on the outer surface of the daughter boards  1 ,  2 . In this way, the daughter boards  1 ,  2  are sandwiched between the heat sinks  50 . The mother board  3  is then sandwiched between the daughter boards  1 ,  2  as illustrated at least in  FIGS. 6 ,  7  and  8 , to form a printed circuit board assembly, shown generally by reference numeral  190 . 
   To the extent that a patentee may act as its own lexicographer under applicable law, it is hereby further directed that all words appearing in the claims section, except for the above defined words, shall take on their ordinary, plain and accustomed meanings (as generally evidenced, inter alia, by dictionaries and/or technical lexicons), and shall not be considered to be specially defined in this specification. Notwithstanding this limitation on the inference of “special definitions,” the specification may be used to evidence the appropriate ordinary, plain and accustomed meanings (as generally evidenced, inter alia, by dictionaries and/or technical lexicons), in the situation where a word or term used in the claims has more than one pre-established meaning and the specification is helpful in choosing between the alternatives. 
   It will be understood that, although various features of the invention have been described with respect to one or another of the embodiments of the invention, the various features and embodiments of the invention may be combined or used in conjunction with other features and embodiments of the invention as described and illustrated herein. Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. Rather, the invention includes all embodiments, which are functional, electrical or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein.