Abstract:
Presented is a detachable module connector comprising a main body with a first section, a second section, and a first opening extending through the first section and the second section, wherein the inner dimensions of the opening in the first section are different from the inner dimensions of the opening in the second section and the opening in the first section is sized to fit around a printed circuit board. The detachable connector is used to couple an electronic module that includes a printed circuit board to a host device. Also presented is a method of building a module using this detachable connector. The detachable connector simplifies the module manufacturing process because the module does not involve the costly hand-soldering and pcb-turning steps of the conventional methods.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation, and claims the benefit, of U.S. patent application Ser. No. 10/378,708, entitled MODULE HOUSING FOR IMPROVED ELECTROMAGNETIC RADIATION CONTAINMENT, filed Mar. 3, 2003, and incorporated herein in its entirety by this reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. The Field of the Invention  
         [0003]     The invention relates generally to electronic modules and particularly to optoelectronic transceiver modules.  
         [0004]     Today, communication systems using optical fiber as a means for transmission are widely employed for a variety of purposes ranging from a basic transmission line in public communication channel to a short-distance network such as a LAN (local area network). Since most of the devices connected by these optical fibers are electronic devices rather than optical devices, optical transceivers are commonly placed at the interface between the optical fibers and the electronic devices. An optical transceiver commonly includes an optical transmitter that receives electric signals and converts them into optical signals, and an optical receiver that receives optical signals and converts them into electric signals.  
         [0005]     Electrical/optical transceivers, therefore, are designed to be electrically and/or optically coupled to a host device and to a transmission line (to a network, to another device, etc.). Typically, transceivers are packaged in the form of a module that has a host device end and a transmission end. At the host device end, the transceiver module may be mounted on a motherboard of a host device and/or mechanically plugged into a panel that is coupled to the host device. At the transmission end, the transceiver module is mechanically coupled with a signal transfer medium such as an electrical wire or an optical fiber. There are a number of different mechanical interfaces with the optical transceiver which have been used in the past and have evolved into industry standards.  
         [0006]     Typically, a transceiver module is physically coupled to the host device with a plastic connector that is soldered onto one end of the printed circuit board (pcb) of the transceiver. The plastic connector is dimensioned to fit with a standard-sized mating structure on the host device. When the transceiver module is physically mated to the host device with this connector, electrical leads and signal ground pins on the transceiver pcb become connected to the appropriate electrical portions of the host device.  
         [0007]     While the plastic connector provides a method of electrically coupling the pcb to the host device, it is a source of inconvenience from a manufacturing standpoint. Since the polymeric material that the plastic connector is made of usually cannot withstand the heat that is applied during reflow soldering, the plastic connector has to be hand-soldered onto the board after electronic components are reflow-soldered on to the board. This hand-soldering process, which involves individually hand-soldering each of multiple (e.g., 20) leads to the plastic connector, lengthens the manufacturing process and drives up the cost of a transceiver module. The signal ground pins, which are usually insert molded into the plastic connector, are difficult to work with because they are designed to connect to the pcb from two opposite surfaces of the pcb. Thus, the manufacturing process involves turning the pcb upside down to achieve high-quality soldering on both sides of the pcb. This step of turning the pcb upside down also lengthens and complicates the manufacturing process.  
         [0008]     Furthermore, because the optical signal operates at a high frequency, conversion of the optical signal to an electrical signal results in generation of electromagnetic radiation. Since the plastic connector does not block electromagnetic radiation effectively, a significant fraction of the electromagnetic radiation leakage to the host device. This leak is highly undesirable, as electromagnetic radiation is known to interfere with the performance of the host device. This leak of electromagnetic radiation makes it difficult for the transceiver module to comply with certain FCC regulations that require minimization of electromagnetic radiation.  
         [0009]     A method of connecting the transceiver to a host device without the above-described disadvantages is desirable.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     Presented is a detachable module connector comprising a first section, a second section, and a first opening extending through the first section and the second section, wherein the inner dimensions of the opening in the first section are different from the inner dimensions of the opening in the second section and the opening in the first section is sized to fit around a printed circuit board. The detachable connector is used to build an electronic module that includes a printed circuit board and a housing encapsulating the printed circuit board. The detachable connector allows the module to be coupled to another device. Also presented is a method of building a module using the detachable connector. The detachable connector eliminates the need for the expensive and time-consuming hand-soldering and pcb-turning steps of the conventional methods.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a side view of an exemplary pin in accordance to the invention;  
         [0012]      FIG. 2A ,  FIG. 2B , and  FIG. 2C  are a perspective view, a top view, and a side view, respectively, of the pin of  FIG. 1  coupled to a printed circuit board;  
         [0013]      FIG. 3A  and  FIG. 3B  are perspective views of a detachable connector in accordance with the invention from different angles;  
         [0014]      FIG. 4  depicts the printed circuit board of  FIG. 2A  coupled with the detachable connector of  FIG. 3A ;  
         [0015]      FIG. 5A  and  FIG. 5B  are a perspective view and an end view, respectively, of a module housing that may be used with the invention;  
         [0016]      FIG. 6A  and  FIG. 6B  are perspective views of a partially housed transceiver module in accordance with the invention shown from different angles;  
         [0017]      FIG. 7A  and  FIG. 7B  are a top exploded perspective view and a bottom exploded perspective view, respectively, of a transceiver module in accordance with the invention; and  
         [0018]      FIG. 8  provides a perspective view of a completely assembled transceiver module in accordance with the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     The present invention is directed to an optoelectronic transceiver module, and it will be described in that context. However, it will be appreciated that the teachings of the present invention are applicable to any electrical device including a printed circuit board that is coupled to another device.  
         [0020]      FIG. 1  depicts an exemplary pin  40  in accordance with the invention. The pin  40 , which has protrusions  41   a  and an extension  41   b , is made of any electrically conductive material, such as metal, using a conventional method. Since the protrusions  41   a  extend in only one direction, coupling the pin  40  with a printed circuit board (pcb) does not require working on both sides of the printed circuit board. The protrusions  41   a  may simply be inserted into openings in the printed circuit board and soldered. Preferably, the pin  40  is reflow-soldered onto the pcb during an automatic soldering process for process efficiency.  
         [0021]      FIG. 2A  depicts the pin  40  coupled to a pcb  20  that may be used to implement the invention. The pcb  20  has a transmission end  22  and a host device end  24 . At or near the host device end  24  is a subsection  26  and pins  40 . A set of leads  28  are arranged on the subsection  26  in the manner that will make them contact the appropriate electrical portions of a host device (not shown) when the board  20  is coupled to the host device. The leads  28  may be placed on the pcb  20  by any of the conventional methods (e.g., electroplating) and be connected to select parts of the circuit on the pcb  20 . Likewise, the pins  40  are shaped and arranged to ensure a formation of an appropriate electrical contact with the host device. At or near the transmission end  22  are transmission leads  29 , which may be coupled to electrical/optical components such as modular transmitter/receiver subassemblies (e.g., TOSA and ROSA).  
         [0022]     If the pin  40  is used as a signal ground pin, the extension  41   b  is designed to connect with the signal ground portion of the host device before the leads  28  connect with the host device, in order to prevent any device damage from electrostatic discharge. Further, if the pins  40  are signal ground pins, they must be selectively isolated from other electrical components on the board. In the embodiment of  FIG. 1 , the electrically conductive pad  44  that contacts the pin  40  is surrounded by a nonconductive portion  43 . The conductive pad  44  is electrically coupled to selective parts (not shown) of the circuit in/on the pcb  20 , which is a multi-layer board. As shown, the conductive pad  44  preferably has holes  42  therein into which protrusions  41  a of the pin  40  is inserted before being soldered.  
         [0023]     The board  20  preferably includes a chassis ground section on both the top and bottom surfaces, such as the chassis ground ring  50  that is shown. The chassis ground ring  50  is positioned near one or more edges of the pcb. A chassis-ground hole  52  may be formed on the chassis ground ring  50 . Although  FIG. 2  depicts only one chassis-ground hole  52  positioned near the subsection  26 , the invention is not limited to any particular size, location, or number of chassis-ground hole  52 . In addition to the chassis-ground hole  52 , via holes  54  are formed on the chassis ground ring  50 , connecting the chassis ground sections on the top and bottom surfaces of the pcb  20 . The inner walls of the via holes  54  are coated with conductive material, which become chassis-ground when placed in contact with the chassis ground sections. Any number of chassis-ground hole  52  may be positioned along the chassis-ground section of the pcb  20 , some of which may be via holes that are much smaller than the chassis-ground hole  52  that is shown. The chassis ground ring  50  and the hole  52  help contain the electromagnetic radiation emitted by the electrical components within the module, as will be described below in more detail.  
         [0024]      FIG. 2B  depicts a top view of the pcb  20 . The top view shows that the two pins  40  are positioned apart approximately by the width of the pcb  20 . Optionally, the pins  40  may extend farther out than the leads  28  to ensure that they will contact the host device before the leads  28 , thus preventing an occurrence of electrostatic discharge that might damage the host device and/or the pcb  20 .  
         [0025]      FIG. 2C  depicts a side view of the pcb  20 . The side view shows that a part of the extension  41   b  is flush with the bottom surface of the pcb  20 . “Bottom,” as used herein, refers to the side opposite the side on the pcb  20  through which the pin  40  is inserted. This configuration facilitates the manufacturing process because the pin  40  can be coupled to the board  20  while the board  20  is laid on a surface, and the board  20  does not need to be turned over to insert a pin from the bottom surface. The extension  41   b  of the pin  40  may have approximately the same thickness as the pcb  20  as shown, although the invention is not so limited.  
         [0026]      FIGS. 3A and 3B  depict a detachable connector  30  in accordance with the invention.  FIG. 3A  depicts the detachable connector from the pcb-side, while  FIG. 3B  depicts the detachable connector from the host-device end  24  (see  FIG. 2A ). The detachable connector  30 , which may be made of any rigid material such as plastic, is preferably an integrated unit including a main portion  32  and a pin supporter  34  on each side of the connecting portion  32 , although the invention is not so limited. The main portion  32  includes a first section  32   a , a second section  32   b , and an opening  33  extending through both sections  32   a ,  32   b . The first section  32   a  includes an opening  33  formed by thick walls  36 . The opening  33  is dimensioned so that when the subsection  26  (see  FIG. 2A ) extends through the opening  33 , there will be only a minimal gap between the subsection  26  and the inner surfaces of the first section  32   a . Since the subsection  26  of the pcb fits substantially tightly into the opening  33 , the first section  32   a  couples the connector  30  to the pcb  20  (not shown). The second section  32   b  has walls that are thinner than the thick walls  36 . The difference between the sizes of the opening  33  in the first section  32   a  and the second section  32   b  can be seen by comparing  FIG. 3A  and  FIG. 3B , as each view shows the opening  33  from a different angle. When the outer dimensions of the second section  32   b  are approximately the same as the outer dimensions of the second section  32   a , as shown, the gap between the subsection  26  and the inner surfaces of the second section  32   b  will be significantly larger than the gap between the subsection  26  and the inner surfaces of the first section  32   a . The thickness of the walls that form the opening  33  can be adjusted to a particular pcb and a particular mating structure at the host device.  
         [0027]     The pin supporter  34  includes a reinforcement  34   a , an open section  34   b , and a channel  37  that runs continuously through both sections. The section of the channel  37  in the reinforcement  34   a  is designed to accommodate a comer of the pcb  20  that is closest to the pin  40  and the portion of the pin  40  that is adjacent to the pcb  20 . By encapsulating the junction of the pin  40  and the pcb  20 , the reinforcement  34   a  provides extra security to the pin-pcb coupling. The open section  34   b  supports the portion of the pin  40  that contacts the host device. Thus, the open section  34   b  is shaped to partially encapsulate the pin  40  and provide stability while keeping the critical parts of the pin  40  exposed. Overall, the pin supporter  34  ensures secure attachment of the pin  40  to the pcb  20  and prevents the pin  40  from bending or breaking, thereby ensuring a solid electrical connection between the host device and the pcb  20 .  
         [0028]     On the outer surface of the detachable connector  30  is a flat area  35 . The flat area  35 , which may be a sidewall formed by a dip, lies in a plane that is substantially orthogonal to the plane of the pcb  20 . In the preferred embodiment, the flat area  35  is located around the intersection of the main portion  32  and the pin supporter  34 , on both the top and the bottom. The flat area  35  provides an extra way to secure the coupling of the detachable connector  30  to the pcb  20  by allowing a portion of the module to latch onto the flat area, as described below in more detail.  
         [0029]      FIG. 4  depicts the printed circuit board  20  of  FIG. 2A  coupled with the detachable connector  30  of  FIG. 3A  and  FIG. 3B .  FIG. 4  shows that the subsection  26  extends through the opening  33  of the first section  32   a  and into the second section  32   b . Since the opening  33  and the channel  37  are dimensioned to fit tightly around the pcb  20 , the detachable connector  30  remains coupled to the pcb  20  without soldering. Thus, the costly hand-soldering step that is part of the current module manufacturing process is not necessary. When using the detachable connector  30 , the leads  28  (see  FIG. 2A ) and the pins  40  (see  FIG. 1 ) do not have to be individually soldered-on for the pcb  20  to be mated to a host device.  
         [0030]      FIG. 5A  depicts a module housing  120  that is combined with the pcb  20  and the detachable connector  30  to contain electromagnetic radiation. The module housing  120  is made of a material that blocks electromagnetic radiation, such as metal. As is well known, it is desirable to prevent any electromagnetic radiation emitted by the electrical components on the pcb  20  from escaping the module. Although not clearly shown in  FIG. 5A , the module housing  120  is a combination of two partial housings (see  FIG. 6A ). When the two partial housings are fitted together, a slot  122  forms near the interface of the two partial housings. When the module is assembled, the subsection  26  (see  FIG. 2A ) of the pcb  20  extends through this slot  122  before extending into the opening  33  (see  FIG. 3A ) of the detachable connector  30 . The slot  122  must provide a minimum clearance so as not to interfere with the electrical signals present on the high speed traces/leads of the pcb  20 . As the amount of radiation that can escape through the slot  122  is a function of the frequency of the radiation, the dimensions of the slot  122  may be adjusted according to the expected frequency distribution of the radiation that will be emitted. As data speed increases and the frequency of the emitted radiation rises, the slot  122  needs to be made smaller because higher frequency radiation can escape through smaller openings.  
         [0031]     A pole  124  that is positioned on an inner wall of the slot  122  extends into and contacts the chassis-ground hole  52  (see  FIG. 2A ), minimizing the effective size of the slot  122 . The pole  124  is made of an electrically conductive material, preferably the same material as the housing  120 , and is chassis-ground like the housing  120 . The inner wall of the chassis-ground hole  52  is coated with electrically conductive material. Thus, when the pole  124  is inserted into the hole  52 , the length of the longest dimension of the slot  122  is reduced for the purpose of radiation leakage. As stated above, chassis-ground via holes  54  (see  FIG. 2A ) may be formed anywhere along the chassis-ground section of the pcb  20 . The inside wall of each via hole is coated with a conductive material, effectively forming a small, hollow “pole” that connects two chassis-ground sections and reduces the dimension of a nearby opening in the housing. The via holes  54  on the chassis ground ring  50  do not have to extend through the pcb  20 . Since each via hole reduces the longest dimension of a nearby opening through which radiation can escape, the via holes provide an effective way of minimizing radiation leakage. More details about via holes are provided in Patent Application No. ______ [which claims priority from Provisional Application No. 60/419,444].  
         [0032]      FIG. 5A  and  FIG. 5B  depict a fastening mechanism that includes hooks  95  that protrude substantially orthogonal to the cover and the base on the host device end  24 . These hooks  95  help attach the connector  30  to the pcb  20 , which are not soldered together. More details on the hooks  95  are provided below.  
         [0033]      FIG. 5B  depicts the module housing  120  from the host end  24  (see  FIG. 5A ).  FIG. 5B  clearly shows an upper wall  92  and an inner wall  76  contacting each other to form the slot  122  and the pole  124  disposed approximately halfway between the longest side of the slot  122 . More details about the upper wall  92  and the inner wall  76  will be provided below.  
         [0034]      FIG. 6A  depicts a partially housed transceiver module  88  from the host device end  24 . The partially housed transceiver module  88  includes the assembled pcb  20  secured to the bottom housing  70  with the screw  82 .  FIG. 6B  depicts the partially housed transceiver module  88  of  FIG. 6A  from the transmission end  22 .  
         [0035]      FIG. 7A  and  FIG. 7B  depict an exploded perspective view of an optoelectronic transceiver module  60  in accordance with the invention. The optoelectronic transceiver module  60  includes the pcb  20  and the detachable connector  30  (see  FIG. 3A ) enclosed in the module housing  120  (see  FIG. 5B ). In the particular embodiment shown, the pcb  20  is coupled to the pins  40  and modular optical subassemblies  62 . The modular optical subassemblies  62 , which typically contain a laser, a photodiode, and various other optical elements, are connected to the transmission leads  29  (see  FIG. 2A ) via ribbon connectors  64 . The pcb  20  is then attached to the detachable connector  30  in the manner described above, in reference to  FIG. 4 . The module housing  120  of  FIG. 5A  is shown as a bottom housing  70  and a top housing  90 . The pcb  20  and the connector  30  are first placed into a bottom housing  70  as indicated by an arrow A, and then the top housing  90  is added as shown by an arrow B. The modular optical subassemblies  62  are positioned in their respective compartments  72  and fixed with a clip  74 , which holds detachable fiber optic cables (not shown) into place. The clip  74  is shaped to fit tightly within the compartments  72  and has an opening  75  that is sized to fit the optical subassemblies  62 .  
         [0036]      FIG. 7A , which is a top exploded perspective view, shows the positions of the inner wall  76  and the outer wall  77  on the bottom housing  70 . The inner wall  76  surrounds a region (also referred to as a “second region” herein) of the a base  80  while the outer wall is discontinuous. The base  80  with an external surface and an internal surface, an inner wall  76  positioned along the edge(s) on the internal surface, and an outer wall  77  positioned adjacent to the inner wall  76 . An “external surface,” as used herein, is the surface that would lie on the outside of the module  60  when the module  60  is completely assembled. An “internal surface” is the surface that would lie on the inside of the module  60  upon complete assembly. Preferably, the bottom inner wall  76  extends continuously along three edges and turns into a lower curved support structure  78   a  for supporting the modular optical subassemblies  62 . As shown, the lower curved support structure  78   a  separates the compartments  72  that house the optical subassemblies from the rest of the housing  70  that houses the pcb  20 . The bottom inner wall  76  is designed so that when the pcb  20  rests on it, the inner wall  76  comes in contact with the chassis ground section (not shown) at the bottom surface of the pcb  20 . A screw  82  may extend through a hole  84  on the pcb  20  and be threaded into an opening  86  in the bottom housing  70 .  
         [0037]      FIG. 7B , which is a bottom exploded perspective view, shows the position of the upper wall  92  on the upper housing  90 . The upper wall  92 , which is formed on the internal surface of a planar cover  93 , surrounds a region of the upper wall. (This region is also referred to as the “first region”). The upper wall  92  extends along the edges and turns into the upper curved support structure  78   b  that, when combined with the lower curved support structure  78   a , is designed to hold the modular assemblies  62  in place. The upper wall  92 , which forms a pattern that is substantially a mirror image of the pattern formed by the inner wall  76 , contacts the chassis ground ring  50  when the top housing  90  is combined with the partially housed transceiver module  88  (see  FIG. 6A ). The dimensions of the upper wall  92 , the inner wall  76 , and the bottom outer wall  77  are determined according to the thickness of the pcb  20 , to ensure that electromagnetic radiation will be contained as much as possible.  
         [0038]     In accordance with the invention, the upper wall  92 , the inner wall  76 , and the bottom outer wall  77  are dimensioned to tolerate some variance in the thickness of the pcb  20  without compromising the effectiveness of electromagnetic radiation containment. When the pcb  20  has a thickness above a certain threshold thickness, electromagnetic radiation is contained by two layers of sidewalls: a first layer including the upper wall  92  and the inner wall  76  sandwiching the pcb  20 , and a second layer that includes the outer wall  77 . The upper wall  92  and the inner wall  76  press on opposite surfaces of the pcb  20  and are fixed in position with screws  94 . Preferably, the parts of the upper wall  92  and the inner wall  76  that contact each other are lined with an electrically conductive material (not shown) that is softer than the metal that the module housing is made of (e.g., conductive rubber) to achieve a better seal at the interface. The height of the upper wall  92  is such that when the upper wall  92  is coupled to the chassis ground ring  50  of the pcb  20 , electrical components on the upper surface of the pcb  20  will not touch the cover  93 . Likewise, the bottom inner wall  76  provides sufficient clearance for the electrical components on the lower surface of the pcb  20  (if any) when the pcb  20  rests on the bottom inner wall  76 . The top housing  90  and the bottom housing  70  contact only the chassis ground sections of the pcb  20  so that they do not affect the circuitry on the pcb  20 . Thus, when the pcb  20  is thick enough to contact the upper wall  92 , radiation is contained within the space defined by the inner wall  76 , the upper wall  92 , the cover  93 , and the base  80 . Any radiation that escapes this first layer of radiation shield is blocked by the outer wall  77 , which contacts the cover  93  to form a second layer of radiation shield.  
         [0039]     When the thickness of the pcb  20  is below the threshold thickness, the upper wall  92  does not contact the chassis ground ring  50  because the cover  93  lodges on the bottom outer wall  77  of the bottom housing  70 . Thus, the upper wall  92  and the inner wall  76  do not form the first layer of radiation shield when the pcb  20  is thin. However, the outer wall  77  still acts as the radiation shield. The cover  93  makes firm contact with the outer wall  77  and are fixed in place by screws  94 . The area of the cover  93  that is near the edges or the outer wall  77  may be partially lined with conductive rubber to achieve a better seal at the interface. Thus, for a thin pcb  20 , radiation is contained within the space defined by the cover  93 , the base  80 , and the outer wall  77 .  
         [0040]     Near the host device end  24 , the upper wall  92  and the inner wall  76  form a layer of radiation shield. This radiation shield being positioned between the electrical components of the pcb  20  and the detachable connector  30 , not much radiation reaches the detachable connector  30 . Thus, even if the detachable connector is made of plastic, radiation is unlikely to reach the host device that is coupled with the subsection  26 . The electrically isolated pins  40  are positioned outside of the radiation shield, since they will be connected to the host device.  10401  The upper housing  90  has a hook  95  that is positioned and shaped to latch onto the sidewall formed by the flat area  35  (see  FIG. 3A ) of the detachable connector  30 . As mentioned above, the detachable connector  30  is not soldered onto the pcb  20 . The hook  95  securely fastens the detachable connector  30  to the rest of the module  60  to provide an extra layer of security that the connector  30  will not separate itself from the pcb  20  during operation. The hook  95  may be substituted or supplemented with any conventional fastening mechanism that a person of ordinary skill in the art would deem suitable.  
         [0041]      FIG. 8  depicts a completely assembled transceiver module  60 . When completely assembled, the transceiver module  60  is completely enshrouded in a radiation-shielding housing with the exception of the parts that need to be exposed to connect to the host device: the leads  28  on the subsection  26  and the extension  41   b  of the pins  40 .  
         [0042]     A person of ordinary skill in the art would understand that various modifications may be made to the module connector described herein without straying from the scope of the invention.