Patent Publication Number: US-2007099513-A1

Title: Plug-in device and method of making the same

Description:
BACKGROUND OF THE INVENTION  
      The present invention is directed toward plug-in devices and, more particularly, toward plug-in control devices and their manufacture.  
      Conventionally, a plug-in device, such as an industrial timer, has a case or housing for enclosing internal circuitry. The housing is secured to a base having pin conductors that are adapted for insertion into a socket to form an electrical connection therewith. Typically, the base is formed of plastic and has a plurality of outwardly-extending conductor pins arranged in a circular configuration. The conductor pins are composed of metal, or are metal plated, and are typically hollow. Usually, the conductor pins are swaged into the plastic base. Sometimes they are insert-molded into the base. The conductor pins are electrically connected to the internal circuitry so as to maintain a minimum spacing (for both creepage and clearance) required by UL508, CSA C22.2 No. 14-M91 and the CE Low Voltage Directive 73/23/EEC. In order to attain such spacing, the conductor pins are usually connected to terminals of the internal circuitry by discrete wires, which have different colors to help ensure that proper connections are made. The wires are connected to the terminals and the conductor pins by soldering, with inner ends of the wires being soldered to the terminals of the internal circuitry first. More specifically, the inner ends of the wires are wave soldered to the terminals before the housing is secured to the base. Once the inner ends of the wires are soldered to the terminals, outer ends of the wires are inserted into the conductor pins and the housing is attached to the base. The base with the conductor pins is then dipped into a solder pot to solder the outer ends of the wires to the pin connectors. Since the base is subjected to a high temperature when it is dipped into the solder pot, the base must be formed from a high temperature plastic, such as a polyphenylene sulfide, which is commercially available from Phillips Petroleum under the tradename RYTON R-4.  
      As can be appreciated, the foregoing conventional method of manufacturing a plug-in device is complicated, labor intensive and susceptible to human error. In addition, the method requires the base to be formed from a high temperature plastic. High temperature plastics are typically expensive and brittle, which can cause yield and reliability problems.  
      U.S. Pat. No. 5,246,386 to Nanjo discloses a method of forming a base for a plug-in device that avoids some of the foregoing problems. In the method of the Nanjo patent, a base is formed from high temperature plastic in an injection molding process. The base includes an outer surface with a plurality of shafts extending outwardly therefrom. The shafts are arranged in a circular configuration and are disposed adjacent to through-holes, respectively. A circuit is formed on an interior surface of the base by chemical plating. The shafts are chemically plated with metal so as to form conductor pins, and the through-holes are chemically plated with metal so as to form electrical conductors that connect the conductor pins to the circuit.  
      The method of the Nanjo patent eliminates the problems associated with using discrete wires, but still requires the base to be made from high temperature plastic. In addition, an extensive amount of plating must be performed.  
      Based on the foregoing, there exists a need in the art for an improved plug-in device and method of making the same. The present invention is directed to such a device and method.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, a plug-in device is provided and includes a circuit board having a first side with conductive tracks and a second side. A plastic base is secured to the circuit board and is disposed on the second side thereof. The plastic base is configured for at least partial insertion into a socket and a portion of the plastic base extends through the circuit board. A plurality of conductor pins are secured to the circuit board and extend through the plastic base. The conductor pins each have a first portion disposed in the plastic base and a second portion extending outwardly from the plastic base. Electrical circuitry is disposed on the first side of the circuit board and is electrically connected to the conductive tracks and the conductor pins.  
      Also provided in accordance with the present invention is a plug-in device having a circuit board with conductive tracks and at least one dielectric layer. A plastic base is secured to the circuit board. The plastic base has a key shaft adapted for insertion into a socket. A plurality of conductor pins are secured to the circuit board and extend through the plastic base. The conductor pins are disposed around the key shaft.  
      A method of forming a plug-in device is also provided in accordance with the present invention. In accordance with the method, conductor pins and a circuit board with conductive tracks are provided. The conductor pins are soldered to the circuit board so as to be connected to the conductive tracks. A base is molded from a plastic resin with the circuit board as an insert such that the base has a key shaft adapted for insertion into a socket and such that the conductor pins extend through the base.  
      Another method of forming a plug-in device is provided in accordance with the present invention. In accordance with the method, conductor pins, a circuit board and plastic base are provided. The circuit board has conductive tracks and a plurality of through-holes. The plastic base has a first side with a key shaft extending therefrom and a second side with a plurality of studs extending therefrom. A plurality of pin passages extend between the first and second sides of the plastic base. The conductor pins are soldered to the circuit board so as to be connected to the conductive tracks. The plastic base is disposed over the circuit board such that the conductor pins extend through the pin passages and the studs extend through the through-holes. The studs are heat staked to secure the plastic base to the circuit board. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
       FIG. 1  is an elevational view of a first plug-in device embodied in accordance with the present invention;  
       FIG. 2  is an elevational view of the first plug-in device with an outer housing removed;  
       FIG. 3  is a side view of a conductor pin of the first plug-in device;  
       FIG. 4  is a partial sectional view of the first plug-in device, showing the conductor pin mounted to a circuit board;  
       FIG. 5  is a sectional view of a portion of a second plug-in device embodied in accordance with the present invention, showing a conductor pin mounted to a circuit board;  
       FIG. 6  is a partial sectional view of a mold with the circuit board of the first plug-in device disposed therein;  
       FIG. 7  is a bottom plan view of the first plug-in device;  
       FIG. 8  is a top plan view of a socket;  
       FIG. 9  is a schematic view of circuitry of the first plug-in device connecting a power source to a load;  
       FIG. 10  is a top plan view of a base of a third plug-in device; and  
       FIG. 11  is a side cross-sectional view of a portion of the third plug-in device, including the base. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      It should be noted that in the detailed description that follows, identical components have the same reference numerals, regardless of whether they are shown in different embodiments of the present invention. It should also be noted that in order to clearly and concisely disclose the present invention, the drawings may not necessarily be to scale and certain features of the invention may be shown in somewhat schematic form.  
      As used herein, the acronym “PCB” shall mean “printed circuit board”.  
      Referring now to  FIGS. 1 and 2 , there is shown a plug-in device  12  embodied in accordance with the present invention. The plug-in device  12  is a control device, such as an industrial timer; however, the present invention is not limited to control devices or industrial timers. The plug-in device  12  includes an outer housing  13 , which has been removed in  FIG. 2  to better show the interior of the switching device. In addition to the housing  12 , the plug-in device  12  generally includes a base PCB  14 , one or more electrical components  18  and a plug-in base assembly  22  that includes a base  24  with a plurality of conductor pins  26  secured thereto and extending therefrom. The plug-in device  12  may further include a control PCB  16 . The manufacture of the plug-in device  12  includes securing the conductor pins  26  to the base PCB  14  and then forming the base  24  over the base PCB  14 , as will be described more fully below.  
      Referring now to  FIG. 3 , one of the conductor pins  26  is shown. Each conductor pin  26  is composed of an electrically conductive metal, such as copper or alloys of copper, iron, cobalt, silver, gold, nickel and other conductive metals. An example of such an alloy is Kovar® alloy, which is an iron-nickel-cobalt alloy that is commercially available from Carpenter Technology Corporation. Each conductor pin  26  is elongated and includes a body portion  28  joined to an anchor portion  30 . The body portion  28  is adapted for smooth insertion into a contact  31  of a socket  32  (shown in  FIG. 8 ). Since the contacts  31  of the socket  32  are cylindrical (as is conventional), the body portion  28  has a smooth cylindrical surface and a rounded end  28   a  to facilitate insertion into the contacts  31  of the socket  32 . In contrast to the body portion  28 , the anchor portion  30  has a foot  36  and at least one protrusion  34 . The protrusion  34  is adapted to promote the mechanical anchoring of the conductor pin  26  to the base  24  and to facilitate the shedding of axial forces that are applied to the conductor pin  26  during the insertion and retraction of the base  24  into and from the socket  32 , respectively. In the embodiment shown in  FIG. 3 , the protrusion  34  is annular or ring-shaped. In other embodiments, the protrusion(s)  34  may have different shapes. For example, the protrusion(s)  34  may be frusto-conical, triangular, barbed, etc.  
      The conductor pins  26  are fixedly mounted to the base PCB  14  so as to extend from a bottom side thereof. In an embodiment shown in  FIG. 4 , the conductor pins  26  are secured to pads  42 , respectively, on the bottom side of the base PCB  14 . The pads  42  are arranged in a pattern corresponding to isolation areas  44  (shown in  FIG. 7 ) that are formed in the base  24 , as will be described further below. The pads  42  are composed of copper and may be coated with thinner layers of nickel and gold. Typically, the pads  42  are greater than 20 μm thick. The conductor pins  26  are secured to the pads  42  using a suitable surface mounting technique known in the art. For example, in one such known mounting technique, a solder paste is deposited on the pads  42 , respectively, such as through a stencil patterned with openings corresponding to the locations of the pads  42 . The solder paste includes flux and a solder, which may be an alloy of tin and one or more other metals, such as silver, gold, lead, zinc, bismuth and/or copper. The conductor pins  26  are placed in a jig and pressed against the pads  42 . With the jig and the base PCB  14  so positioned, the jig and the base PCB  14  are placed into an infrared reflow furnace and are heated to an elevated temperature, which causes the solder to reflow around and over the feet  36 . The jig and the base PCB  14  are then removed from the reflow furnace and allowed to cool, which causes the solder to harden, thereby forming solder joints  46  that secure the conductor pins  26  to the pads  42 .  
      Surface mounting of the conductor pins  26  permits the electrical components  18  to be mounted directly over the conductor pins  26  (as shown in  FIG. 4 ), which provides flexibility in the arrangement of the components of the plug-in device  12 . It should be appreciated, however, that the present invention is not limited to the surface mounting of the conductor pins  26 . For example,  FIG. 5  shows a portion of a plug-in device  47  constructed in accordance with another embodiment of the present invention, wherein conductor pins  48  are secured to a base PCB  50  using a through-hole mounting technique. The plug-in device  47  has the same construction as the plug-in device  12 , except for the differences described below. Conductor pins  48  have the same construction as the conductor pins  26 , except the anchor portions  30  of the conductor pins  48  each additionally have a bulbous portion  52  joined to a top plate portion  54 . Base PCB  50  has the same construction as the base PCB  14 , except for the differences described more fully below  
      In a through-hole technique, pin holes  56  are formed in the base PCB  50  in a pattern corresponding to the isolation areas  44  in the base  24 . The pin holes  56  are conductive, i.e., are defined by conductive interior walls, and extend completely through the base PCB  50 . Each of the pin holes  56  has a width or diameter that is slightly larger than the width or diameter of the bulbous portions  52  of the conductor pins  48  so as to accommodate the bulbous portions  52  of the conductor pins  48 , respectively. The top plate portions  54  of the conductor pins  48  are disposed above the pin holes  56  and are soldered to top conductor tracks  60  of the base PCB  50  by a solder wave in which molten solder flows across the top side of the base PCB  50 . The molten solder fills the voids between the conductor pins  48  and the pin holes  56  and forms solder joints  62  between the conductor pins  48  and the conducting pin holes  56  and the top conductor tracks  60  in the base PCB  50 . The solder used to bond the conductor pins  48  to the pin holes  56  and the top conductor tracks  60  may be the same as that used in the surface mounting technique described above.  
      In the paragraphs that follow, various aspects of the invention are described that apply both to the plug-in device  12  and the plug-in device  47 . Accordingly, where applicable, components of the invention are provided with reference numerals for both embodiments, notwithstanding the fact that only one embodiment may be shown in a referenced drawing.  
      The base PCB  50  is single sided, i.e., has conductors tracks on only one side of the base PCB  50 , namely top conductor tracks  60 , whereas the base PCB  14  is double sided, i.e., has conductor tracks on both sides of the base PCB  14 , namely top conductor tracks  60  and bottom conductor tracks  64 . The base PCB  14  and the base PCB  50  may have conventional laminate constructions, wherein the base PCB  14  is formed from one or more insulating or dielectric sheets and two or more copper sheets or foils, and the base PCB  50  is formed from one or more insulating or dielectric sheets and one or more copper sheets. Each dielectric sheet may be comprised of a fiber web impregnated with a thermoset resin, such as phenol formaldehyde or an epoxy. Top and bottom solder resist layers  68 ,  70  may be deposited on the top and bottom sides of each of the base PCB  14  and the base PCB  50 .  
      A plurality of anchor passages or holes  74  extend through the base PCB  14  and the base PCB  50 . The holes  74  are provided for securing the base PCB ( 14 ,  50 ) to the base  24 , as will be described more fully below. In the base PCB  14 , the anchor holes  74  may also serve as connector holes for electrically connecting the bottom conductor tracks  64  to the top conductor tracks  60 , as is shown in  FIG. 4 . In such a case, the anchor holes  74  are formed before the copper foil(s) are deposited on the dielectric sheet(s)  66 . In this manner, when the copper is deposited on the dielectric sheet(s)  66 , the copper coats the interior walls defining the anchor holes  74 , thereby forming conductive connectors  76 .  
      In the base PCB  50 , the anchor holes  74  may be formed after the copper foil(s) are deposited on the dielectric sheet(s)  66 . In this manner, the interior walls defining the anchor holes  74  are not coated with copper, as is shown in  FIG. 5 . The pin holes  56 , however, are formed in the base PCB  50  before the copper foil(s) are deposited on the dielectric sheet(s)  66  so that when the copper is deposited on the dielectric sheet(s)  66 , the copper coats the interior walls defining the pin holes  56 , thereby making them conductive.  
      In the embodiment of the invention shown in  FIG. 4 , wherein the conductor pins  26  are surface mounted to the base PCB  14 , the bottom conductor tracks  64  electrically connect the pads  42  to the conductive connectors  76  (as shown), or to wiring (not shown). The conductive connectors  76  extend through the base PCB  14  and may be located toward an outer edge of the base PCB  14 , whereas the wiring may extend around an outer edge of the base PCB  14  or through a notch or opening formed in the base PCB  14 , toward an outer edge thereof. The conductive connectors  76  or wiring, are electrically connected to the top conductor tracks  60  and/or to a pin header  78 , or other type of connector, mounted to the top surface of the base PCB  14 .  
      In the embodiment where the conductor pins  48  are through-hole mounted to the base PCB  50 , the pin holes  56  are electrically connected to the top conductor tracks  60 , respectively.  
      In the embodiments where the plug-in device ( 12 ,  47 ) is an industrial timer, the electrical components  18  include relays, such as solid state relays. The electrical components  18  may be surface mounted (as shown in  FIG. 4 ) or through-hole mounted to the base PCB ( 14 ,  50 ) or may be secured to a connector mounted to the base PCB ( 14 ,  50 ). The electrical components  18  are mounted to the base PCB ( 14 ,  50 ) so as to be disposed on a top side of the base PCB ( 14 ,  50 ), proximate to the top surface of the base PCB ( 14 ,  50 ). Terminals of the electrical components  18  are electrically connected to the top conductor tracks  60  of the base PCB ( 14 ,  50 ), which are electrically connected to the pin header  78  and/or the pin holes  56  (for the conductor pins  48 , which are through-hole mounted), or the conductive anchor holes  74  or wiring (for the conductor pins  26 , which are surface mounted).  
      After the base PCB ( 14 ,  50 ) with the conductor pins ( 26 ,  48 ) and the electrical components  18  has been completely populated and soldered, the base PCB ( 14 ,  50 ) is insert molded into the base  24 , which is comprised of a dielectric thermoplastic resin. In one embodiment of the present invention, the thermoplastic resin that is used to form the base  24  is comprised of Noryl® 1250 resin, which is a modified polyphenylene ether polymer commercially available from GE Plastics. Other thermoplastic resins that may be used to form the base include polyethylene terephthalate (PET), polystyrene, polybutylene terephthalate (PBT) and PBT alloys, polypropylene and propylene alloys, thermoplastic polyurethane, polyvinyl chloride (PVC), polyesters, polypropylene and polystyrene alloys, polyethylene, nylon, polyacetal, styrene acrylonitrile (SAN), styrene maleic anhydride (SMA), acrylonitrile-butadiene-styrene copolymer (ABS), acrylics and cellulosics. High temperature thermoplastics, such as polycarbonate and polycarbonate alloys, polyetherimide, polysulfone, polyethersulfone, amorphous polyamides and fluoropolymers may also be used, but may not be as desirable due to higher cost and/or undesirable properties, such as brittleness. The foregoing list is not meant to be exhaustive, but only illustrative of the various thermoplastic resins that can be used to form the base  24  in the practice of the present invention.  
      Referring now to  FIG. 6 , the base PCB ( 14 ,  50 ) is disposed in a mold  82  of an injection molding machine. The mold  82  includes a pair of platens  84  (at least one of which is movable) that cooperate to define a cavity  86 , which is configured to hold the base PCB ( 14 ,  50 ) and to shape the molten thermoplastic so as to form the base  24  thereon. The base PCB ( 14 ,  50 ) is disposed in the cavity  86 , with the anchor holes  74  aligned with recesses  88  in one of the platens  84 . The anchor portions  30  of the conductor pins ( 26 ,  48 ) are disposed in the cavity  86 , however, the body portions  28  of the conductor pins ( 26 ,  48 ) extend out of the cavity  86  through passages  90  in the other one of the platens  84 . The passages  90  cooperate with lowermost ribs  34  of the conductor pins ( 26 ,  48 ) to form shut off points  92  where the flow of molten thermoplastic is pinched off. The shut-off openings  90  are sized to tightly receive the body portions  28  of the conductor pins ( 26 ,  48 ) to prevent the flow of molten thermoplastic resin out of the cavity  86 , but not so tightly so as to damage the conductor pins ( 26 ,  48 ).  
      With the base PCB ( 14 ,  50 ) so disposed in the cavity  86 , molten thermoplastic resin is injected into the cavity  86  under pressure. The molten thermoplastic flows against the bottom surface of the base PCB ( 14 ,  50 ) through the anchor holes  74  and into the recesses  88 , thereby forming anchors  94  for securing the base  24  to the base PCB ( 14 ,  50 ). The molten thermoplastic also flows around and over the anchor portions  30  of the conductor pins ( 26 ,  48 ) and is pinched off at the shut-off points  92 . After a predetermined period of time, the injection of the molten thermoplastic into the cavity  86  is shut-off and the thermoplastic in the cavity  86  is allowed to cool. When the thermoplastic is sufficiently cooled, the mold  82  is opened and the base PCB ( 14 ,  50 ) with the base  24  formed thereon is removed.  
      With reference now to  FIGS. 2 and 7 , the base  24 , as formed in the foregoing injection molding process, includes a mount portion  98  joined to a plug portion  100 . The mount portion  98  has a top side that adjoins a bottom side of the base PCB ( 14 ,  50 ). The mount portion  98  may have a shape corresponding to an open end of the outer housing  13 , which may be rectangular, or more specifically square, as shown in  FIG. 7 . The plug portion  100  may be circular, as shown in  FIG. 7 . A positioning projection or key shaft  102  is joined to a central portion of the plug portion  100  and extends downwardly therefrom. The key shaft  102  has a cylindrical body  102   a  with a key ridge  102   b  extending radially outward therefrom for ensuring that the plug-in device ( 12 ,  47 ) is properly plugged into the socket  32 . A plurality of downwardly-extending isolation ribs  104  are joined to a bottom surface of the plug portion  100  and are disposed around the key shaft  102 . More specifically, the isolation ribs  104  extend radially outward from the key shaft  102  and are spaced apart so as to form a pattern of spokes or rays. With this arrangement, the isolation ribs  104  form the isolation areas  44  from which the conductor pins ( 26 ,  48 ) extend. Since plug-in devices are conventionally provided with eight or eleven conductor pins, eight or eleven isolation ribs  104  are typically provided so as to form eight or eleven isolation areas  44 , respectively. In the shown embodiments, the base  24  is provided with eleven conductor pins ( 26 ,  48 ) and therefore, has eleven isolation areas  44 . The present invention, of course, is not limited to a plug-in device having eight or eleven conductor pins; different numbers of conductor pins, such as six, twelve, or eighteen may be utilized.  
      The base PCB ( 14 ,  50 ) is electrically connected to the control PCB  16  by the pin header  78  on the base PCB ( 14 ,  50 ) and a mating pin connector (not shown) on the control PCB  16 . The control PCB  16  contains control circuitry  110  for controlling the electrical components  18 . In the exemplary embodiment where the plug-in device ( 12 ,  47 ) is an industrial timer, the control circuitry  110  of the control PCB  16  has a microcontroller  112  (shown in  FIG. 9 ) and may include a memory. The microcontroller  112  is operable to perform a plurality of timer control routines, such as delay on make, delay on break, recycle, single shot and interval and combinations of the foregoing, which are stored in the memory  114 . First, second and third sets  116 ,  118 ,  120  of manually actuatable dip switches are mounted to a top end wall  122  of the outer housing  13  and are connected to the microcontroller  112 . The first set  116  of first dip switches are operable to select a desired control routine based on the actuation pattern of the dip switches, whereas the second and third sets  118 ,  120  of dip switches are operable to select desired time periods for the control routines. Of course, other manually actuatable interface devices other than dip switches may be utilized for selecting control routines.  
      It should be appreciated that instead of providing a separate control PCB  16 , the control circuitry  110  may be incorporated into the base PCB ( 14 ,  50 ).  
      Referring now to  FIG. 8 , the plug-in device ( 12 ,  47 ) is utilized by plugging the plug-in device ( 12 ,  47 ) into the socket  32 , i.e., inserting the key shaft  102  into a center opening  123  of the socket  32  and the conductor pins ( 26 ,  48 ) are inserted into the contacts  31  of the socket  32 . The contacts  31  connect the conductor pins ( 26 ,  48 ) to screw terminals  125  of the socket  32 , which are connected to wiring of an external circuit. The socket  32  may be mounted to a DIN rail or to a planar surface.  
      In the embodiment where the plug-in device ( 12 ,  47 ) is an industrial timer, the plug-in device ( 12 ,  47 ) may be used to control the supply of power from a power source  124  (such as a battery) to a load  126 , as is shown in  FIG. 9 . In  FIG. 9 , connections external to the plug-in device ( 12 ,  47 ), i.e., external connections, are shown by filled lines, whereas connections internal to the plug-in device ( 12 ,  47 ), i.e., internal connections, are shown by dashed lines. The external connections comprise the contacts  31  and the screw terminals  125  of the socket  32  and external wiring, whereas internal connections comprise top conductor tracks  60  and bottom conductor tracks  64  (for the conductor pins  26 , which are surface mounted). A positive terminal  128  of the power source  124  is externally connected to conductor pins ( 26 ,  48 ) located at positions  2  and  11 , while a negative terminal  130  of the power source  124  is externally connected to conductor pin ( 26 ,  48 ) located at position  10 . The conductor pin ( 26 ,  48 ) located at position  9  is externally connected to the load  126 . A first contact  132  of the control component  18  is internally connected to the conductor pin ( 26 ,  48 ) located at position  9 , while a second contact  134  of the control component  18  is internally connected to the conductor pin ( 26 ,  48 ) located at position  11  and a third contact  136  of the control component  18  is internally connected to the conductor pin ( 26 ,  48 ) located at position  8 . The conductor pin ( 26 ,  48 ) located at position  2  is internally connected to conductor pin ( 26 ,  48 ) located at position  5 , which is externally connected to a first contact  138  of an initiate switch  140 , such as a momentary pushbutton. A second contact  142  of the initiate switch  140  is externally connected to conductor pin ( 26 ,  48 ) located at position  6 , which is internally connected (not shown) to the microcontroller  112 . The microcontroller  112  is internally connected to a control circuit  144  of the control component  18 . In the embodiment where the control component  18  is a relay, the control circuit  144  is comprised of suitably chosen components for blocking and conducting relay coil current.  
      With the plug-in device ( 12 ,  47 ) connected between the power source  124  and the load  126  as described above, actuation of the initiate switch  140  causes power from the power source  124  to be provided as an enable signal to the microcontroller  112  through conductor pins ( 26 ,  48 ) located at positions  2 ,  5  and  6 . It should be appreciated, however, that an external initiate switch circuit is only required for certain standard timing functions and is not generally required for all timing functions. In response to the receipt of the enable signal, the microcontroller  112  performs a control routine that has been selected through the first set  116  of dip switches, such as a delay on make routine. In accordance with this routine, the microcontroller  112  waits for a selected period of time after the receipt of the enable signal and then sends a signal to the control circuit  144  of the control component  18 , instructing the control component  18  to provide a connection between conductor pins ( 26 ,  48 ) located at positions  9  and  11 , thereby supplying power to the load  126 .  
      Referring now to  FIGS. 10 and 11 , there are shown portions of a plug-in device  150  constructed in accordance with still another embodiment of the present invention. The plug-in device  150  has substantially the same construction and operation as the plug-in device  12 , except for the differences described below. The manufacture of the plug-in device  150  differs from the manufacture of the plug-in device  12 . As in the plug-in device  12 , the conductor pins ( 26 ,  48 ) are first secured to a base PCB ( 14 ,  50 ) and then a base  154  is secured to the base PCB ( 14 ,  50 ) over the conductor pins  152 . The base  154  of the plug-in device  150 , however, is not molded over the base PCB ( 14 ,  50 ). Rather, the base  154  is formed apart from the base PCB ( 14 ,  50 ) and is then secured to the base PCB ( 14 ,  50 ) by heat staking and/or application of an adhesive, as described more fully below.  FIG. 10  shows a top plan view of the base  154 , while  FIG. 11  is a side cross-sectional view of the base PCB ( 14 ,  50 ) disposed over the base  154 , with all but one of the conductor pins ( 26 ,  48 ) removed and the electrical components  18  removed to better show certain features of the plug-in device  150 .  
      The conductor pins ( 26 ,  48 ) do not have the protrusions  34 . The portion of each conductor pin ( 26 ,  48 ) that extends through the base  154  is smooth and adapted for facile insertion through a pin passage  156  formed in the base  154 . The conductor pins ( 26 ,  48 ) are secured to the base PCB ( 14 ,  50 ) as described above with regard to the plug-in devices  14 ,  47 .  
      The base  154  has the same construction as the base  24 , except for the differences described below. As set forth above, the base  154  is pre-formed in a plastic molding process and is then secured to the base PCB ( 14 ,  50 ) over the conductor pins  152 . The base  154  has a plurality of pin passages  156  that are disposed around the key shaft  102  and extend through the mount portion  98  and the plug portion  100  of the base  154 . Each of the pin passages  156  has a substantially cylindrical main section  156   a  with a diameter slightly larger than the diameter of a conductor pin  152  so as to permit the conductor pin  152  to move smoothly therethrough. A vent section  156   b  adjoins the main section  156   a . A key passage  158  extends through the key shaft  102 , the mount portion  98  and the plug portion  100 . A shallow, disc-shaped pocket or recess  160  is formed in a top surface of the mount portion  98 . Openings for the pin passages  156  and an opening for the key passage  158  are disposed in the recess  160 . Outward from the recess  160 , a plurality of studs  162  are joined to the top surface of the mount portion  98  and extend upwardly therefrom. The studs  162  are positioned so as to be aligned with the anchor holes  74  in the base PCB ( 14 ,  50 ) when the top surface of the base  154  is aligned with the base PCB ( 14 ,  50 ).  
      The base  154  is secured to the base PCB ( 14 ,  50 ) by aligning a bottom surface of the base PCB ( 14 ,  50 ) with the top surface of the mount portion  98  such that the conductor pins ( 26 ,  48 ) are aligned with the pin passages  156  and the studs  162  are aligned with the anchor holes  74 . The base  154  is then moved toward the base PCB ( 14 ,  50 ) so that the conductor pins ( 26 ,  48 ) and the studs  162  move into and travel through the pin passages  156  and the anchor holes  74 , respectively. The movement of the base  154  stops when the top surface of the base  154  abuts the base PCB ( 14 ,  50 ), at which point, the studs  162  extend through the anchor holes  74  and project above the top surface of the base PCB ( 14 ,  50 ), while the conductor pins ( 26 ,  48 ) extend through the pin passages  156  and project below the plug portion  100  of the base  154 , as shown in  FIG. 11 . With the base  154  and the base PCB ( 14 ,  50 ) so positioned, the studs  162  are heat staked using a press connected to one or more heated process tips. If one tip is provided, the studs  162  are heat staked serially, whereas if a plurality of tips are provided, the studs  162  may be heat staked at the same time. The press may be manual, electric or pneumatic and each tip is composed of metal and has a cavity. The heat staking is performed by pressing the heated tip(s) against the studs  162  using the press. The pressure and heat applied to the studs  162  causes the studs  162  to melt and take the form of the cavity/cavities in the tip(s). The melted studs  162  are allowed to cool and the tip(s) removed, thereby forming the anchors  94 , which secure the base  154  to the base PCB ( 14 ,  50 ). The studs  162  and the tip(s) may be configured to provide the anchors  94  with a high or low profile dome shape, a high or low profile rosette shape, a knurled shape, or a flush profile.  
      After the studs  162  have been heat staked to form the anchors  94 . A measured amount of an adhesive, such as an epoxy adhesive, is injected into the key passage  158  through a bottom opening  158   a  thereof. The adhesive moves upward through the key passage  158 , into the recess  160  and against the bottom surface of the base PCB ( 14 ,  50 ). As the adhesive is injected into the recess  160 , air in the recess  160  is ejected through the vent sections  156   b  of the pin passages  156 . The adhesive then moves into the vent sections  156   b  so as to be visible from outside the base  154 . In this manner, the adhesive in the vent sections  156   b  provides a visual indication whether the adhesive is flowing properly so as to be evenly distributed around the recess  160  and the conductor pins ( 26 ,  48 ).  
      After the adhesive has been injected into the recess  160  as described above, the adhesive is allowed to cure. The cured adhesive forms a bond between the bottom surface of the base PCB ( 14 ,  50 ) and the top surface of the mount portion  98  within the recess  160 , thereby further securing the base  154  to the base PCB ( 14 ,  50 ).  
      In the description of the invention set forth above, the plug-in device ( 12 ,  47 ,  150 ) is described as being a control device, such as an industrial timer. The present invention, however, is not limited to plug-in control devices. Other plug-in devices, such as plug-in sensors, meters and monitors may be constructed in accordance with the present invention.  
      While the invention has been shown and described with respect to particular embodiments thereof, those embodiments are for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein described will be apparent to those skilled in the art, all within the intended spirit and scope of the invention. Accordingly, the invention is not to be limited in scope and effect to the specific embodiments herein described, nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.