Abstract:
Automatic clinging leads of an electric device are provided for an unassisted mounting on thru-holes of a printed circuit board. Each of the leads of the device has three continuous right-angled sections including a longitudinal proximal end section extending from the terminal region of the electric element, a latitudinal distal end section extending at right angle with respect to the proximal end section, and a bent midsection for connecting the proximal and distal end sections at the diametrically opposite right angle to the angle between the proximal and distal end sections to provide a generally laterally extending lead with three alternating bends between the three sections. The device leads can be inserted into the thru-holes of the circuit board through a 90-degree swivel motion that causes a secure flush cling of the leads and in turn a low profile mounting of the device onto the circuit board around thru-holes.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    A. Field of the Invention 
         [0002]    The present invention relates to electric components. More particularly, the present invention relates to shaped connection leads of electric devices for improving the initial positioning of the devices on a circuit board at assembly. 
         [0003]    B. Description of the Prior Art 
         [0004]    Conventionally, an electric component or device such as a transistor  1  shown in  FIGS. 1 and 2  has multiple electrical connections of terminals or leads  2 , usually a set of wires, coming off the transistor  1  in order to make connection to another on a substrate commonly called a printed circuit board (PCB)  3 . The leads  2  function to transfer power, transmit signal in and out of the transistor  1  and are used in probing a circuit implemented on PCB  3 . Upon completion of an insertion at thru-holes  4  of PCB  3  followed by a soldering process, the leads  2  enter electrical i s connections permanently via bodies of solder  5  to their designated circuit terminals on the PCB  3 . The leads  2  are made to extend straight and girthed to be relatively thin so that little or no force is applied for insertion into the hole  4 . Therefore, the device  1  lacks a positive holding means for temporarily setting the correct position of the device  1  with respect to PCB  3  and needs an external assistance for such positioning, which is essential in achieving a prolonged reliable performance of the resulting circuitry in a multitude of harsh environments. Furthermore, the thin extension of leads  2  causes thickening of the bodies of solder  5  and thus the overall circuit unit failing to take advantage of an ample area at the underside of PCB  3 , which is normally void of components. 
         [0005]      FIG. 3  shows pointing pins  6  and its surrounding solder formations  5  in a tightly restricted area of PCB  3  in comparison to the device  1 . 
         [0006]    In order to solve the above or other problems, numerous suggestions have been made. U.S. Pat. No. 4,541,034 to Fanning discloses a special design of thru-hole insertable terminal that has multiple bends as well as a free-ended tab formed internally of the terminal by a blanking or die cut. The Fanning terminals each requires a tab bending after insertion of the terminal for the purpose of a temporary securement as a prerequisite to a permanent soldering process which calls for a dedication of energy and precious machine time. Besides, the formation of a deflection tab through a blanking process limits the choice of material to make such terminals to be flat or in a blade shape although the majority of component leads are cuts of thin wires or rods with round cross sections. It is impractical if not impossible to form a bending tab amid a run of a thin wire. Adding to that difficulty of actual manufacturing is the complex machine dynamics to process the temporary and permanent securements in an automated assembly line. I.e., Fanning terminals need three distinctive movements of vertical insertion of the component and two opposite deflections of the tabs inside the thru-holes. 
         [0007]    U.S. Pat. No. 7,045,720 to Sagayanathan, et al. suggests a component lead system having two opposing leads shaped into a clip to hold a substrate or circuit board area between thru-holes. Each lead is made of different leg sections that are normally under bias rendering downward or upward insertion of the component more difficult which means more energy input is needed just to overcome the excess of bias. 
         [0008]    Other similar patents include U.S. Pat. No. 3,747,045 to Stross; U.S. Pat. No. 5,726,862 to Huynh et al.; U.S. Pat. No. 5,586,008 to Kozel et al. However, none of these component leads take a simple uniform shape that can be applied to different types of lead material to effectuate a single action flipped insertion of components, thereby completing a secure cling of the same to the designated positions on the circuit board. 
         [0009]    In view of these shortcomings of the existing component terminals and leads, an objective of the present invention is to provide auto-cling leads of electric components that allow an unassisted fastening of components onto a circuit board. 
         [0010]    Another objective of the present invention is to provide a standardized shape of components leads regardless of their material type that will result in the same reliable cling of the components until they are permanently soldered to the circuit board, and also be stronger after being soldered to the circuit board. 
         [0011]    Yet another objective of the present invention is to provide leads can be inserted into the thru-holes of the circuit board through a 90-degree swivel motion that causes a secure flush cling of the leads and in turn a low profile mounting of the electric component onto the circuit board around the thru-holes. 
       SUMMARY OF THE INVENTION 
       [0012]    In accordance with the present invention, automatic clinging leads of an electric device are provided for an unassisted mounting on thru-holes of a printed circuit board. The electric device may be either an active or passive electronic component that comprises an electric element extending in a longitudinal direction and having a predetermined conduction function. There are multiple terminal regions formed on the electric element for making electrical connections of the same with another element on the circuit board. The electric device also comprises conductive leads each having three continuous right-angled sections including a longitudinal proximal end section extending from the terminal region of the electric element, a predetermined length of latitudinal distal end section extending at right angle with respect to the proximal end section, and a bent midsection for connecting the proximal and distal end sections at the diametrically opposite right angle to the angle between the proximal and distal end sections meeting at a cross of their imaginary projection lines to provide a generally laterally extending lead with three alternating bends between the three sections. With such electric device, an insertion of the leads through a 90-degree swivel motion into the thru-holes of the circuit board causes a secure flush cling of the leads and in turn a low profile mounting of the electric device onto the circuit board around the thru-holes. 
         [0013]    The auto-cling leads are in a blade shape and have a flat cross section. Alternatively, the leads are in a rod shape and have a round cross section. 
         [0014]    Embodiments of the invention will now be described by way of example with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of a typical electric device having plain terminal leads prior to the present invention. 
           [0016]      FIG. 2  is a partial cross sectional view of a prior art assembly of the electric device of  FIG. 1  on a circuit board. 
           [0017]      FIG. 3  is a bottom view of the circuit board of  FIG. 2 . 
           [0018]      FIG. 4  is a perspective view of an electric component with three auto-cling leads of a flat blade type according to an embodiment of the present invention. 
           [0019]      FIG. 5  is a partial cross sectional view of the auto-cling component of  FIG. 4 , showing the secure hold between the component and circuit board before and after the soldering process. 
           [0020]      FIG. 6  is a top view of the auto-cling component mounted on the circuit board. 
           [0021]      FIG. 7  is a bottom view of the circuit board showing clipping pins completely soldered onto printed circuit portions underside of the board. 
           [0022]      FIG. 8A  is a partially sectional side elevational view of the auto-cling component of  FIG. 4 , showing the component initially aligned to a thru-hole of the board. 
           [0023]      FIG. 8B  is a side elevational view similar to  FIG. 8A , showing a second position of the component in the thru-hole wherein the component is in substantially parallel position to the board. 
           [0024]      FIG. 8C  is a side elevational view showing the component in the thru-hole at a third transitional position. 
           [0025]      FIG. 8D  is a side elevational view showing the component in the thru-hole at a fourth transitional position. 
           [0026]      FIG. 8E  is side elevational view showing the component snugly grasping the board at opposite surfaces as it threads through the hole in a thin mounting position with no bending of the leads involved according to the present invention. 
           [0027]      FIG. 9  is a perspective view of an electric component with two auto-cling leads in a rod type according to an alternative embodiment of the present invention. 
           [0028]      FIG. 10  is a partial cross sectional view of the auto-cling component of  FIG. 10 , showing the secure hold between the component and circuit board before and after the soldering process. 
           [0029]      FIG. 11  is a top view of the auto-cling component mounted on the circuit board. 
           [0030]      FIG. 12  is a bottom view of the circuit board showing clipping pins completely soldered onto printed circuit portions underside of the board. 
           [0031]      FIG. 13A  is a partial cross sectional view of the auto-cling component of  FIG. 10 , showing the component initially aligned to a thru-hole of the board. 
           [0032]      FIG. 13B  is a side elevational view similar to  FIG. 8A , showing a first position of the component in the thru-hole, showing the component is in substantially parallel position to the board. 
           [0033]      FIG. 13C  is a side elevational view showing the component in the thru-hole at a third transitional position. 
           [0034]      FIG. 13D  is side elevational view showing the component in the thru-hole at a fourth transitional position. 
           [0035]      FIG. 13E  is a side elevational view showing the component snugly grasping the board at opposite surfaces as it threads through the hole in a thin mounting position with no subsequent bending of the leads involved according to the present invention. 
       
    
    
       [0036]    Similar reference numbers denote corresponding features throughout the attached drawings.
     1  transistor     2  leads     3  printed circuit board (PCB)     4  hole     5  solder formations     6  pointing pins     10  electronic circuit     50  solder     60  transistor device     70  printed circuit board     72  hole     80  leads     81  longitudinal proximal end section     82  first 90-degree bend     83  shank     84  second 90-degree bend     85  third 90-degree bend     86  pin     87  tip     88  third vertical straight section     90  hole     100  electronic circuit     160  device     180  leads     181  first straight section     182  first 90-degree bend     183  shank     184  second 90-degree bend     185  third 90-degree bend     186  pin     187  tip     188  third straight section   
 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0069]    With reference to  FIGS. 4 and 5  showing an exemplary electric device  60  of the present invention, the device  60  is a transistor with three leads  80  including an emitter E, base B and collector C, which are conductor blades identically formed into a lobster leg according to the present invention and thus will be referenced interchangeably to indicate different features of one of the leads. In  FIG. 5 , the device  60  is secured on PCB  70  to form a part of an electronic circuit  10 . The lead configuration according to the present invention may be applied to manufactured leads of finished electric components or to shaping flat or round leads before a bonding process thereof onto conduction terminals inside an encapsulating package from which the leads  80  will extend. 
         [0070]    Lead  80  has a first straight section  81  extending vertically from a bottom side of device  60  that stands substantially upright from a PCB  70 . PCB  70  has a plurality of thru-holes including a hole  72 . The lower limit in sizing a PCB thru-hole is supposed to be set to slightly exceed the largest girth or diameter of the leads of components mounted to accommodate them with little resistance. Different PCBs have had individually sized thru-holes for specified devices with leads although they are more expensive to make. 
         [0071]    The drawings depict that transistor device  60  may have a stop shaped on each of the leads to show the present invention applied to existing manufactured components although such stops or individual hole sizing may not be necessary thanks to the present invention. Further, according to the present invention, the upper limit of hole  72  also becomes free of a tight tolerance without a concern of displacement of device  60  before and after a subsequent soldering process since the lead of device  60  is adapted to hold device  60  onto PCB  70  without having to engage hole  72 . 
         [0072]    Instead, a second straight section of a flat shank  83  extends from first section  81  via a first 90-degree bend  82  to make a flat engagement with PCB  70  at its dielectric upper surface. A vertical third straight section  88  of the lead penetrating the hole  72  interconnects the shank  83  via a second 90-degree bend  84  and the fourth straight section of a horizontal pin  87  via a third 90-degree bend  85 . The spaced second and third bends  84 ,  85  along with the connecting straight section  88  work in unity as a pivoting means when inserting device  60  into hole  72  during assembly. Pin  86  is terminated by a tip  87 , which is under gravity biased toward a circuit trace (not shown) until a mass of solder  50  is formed to cover the whole pin  86  connecting the same to PCB  70  electrically for good. 
         [0073]    Therefore, each of leads  80  of the electric device constitutes three continuous right-angled sections including longitudinal proximal end section  81  extending from the internal terminal region of the electric device, latitudinal distal end section  86  extending at right angle with respect to the proximal end section  81 , and bent midsection  83 / 88  for connecting the proximal and distal end sections  81 ,  86  at the diametrically opposite right angle to the angle between the proximal and distal end sections  81 ,  86  meeting at a cross of their imaginary projection lines to have the lead  80  extending generally laterally with three alternating bends  82 ,  84  and  85  between the three right-angled sections. 
         [0074]      FIG. 6  clearly shows in plan view the flat shanks  83  after assembly of device  60  while  FIG. 7  shows the same in bottom view. Although the length of shanks  83  is depicted liberally for illustration, it can be shorter to take up less area on the PCB  70  as long as the pivoting unit  84 ,  85  is distanced from the center of gravity of device  60  to effectuate the flip down mounting of the same. Solder  50  conforms to the length of pin  86  and lies flat on the PCB  70  reducing the overall thickness of the electronic circuit  10 . 
         [0075]      FIG. 8A  depicts an alignment of the leads  80  of device  60  to the hole  90  of PCB  70  wherein device  60  is oriented in parallel with PCB  70  facing each other at one upper side so that pin  86  extends in the same direction as the hole  90 . Here, PCB  70  is positioned upright with the components side on top and the circuit traces for soldering facing down. 
         [0076]    In step two of  FIG. 8B , the leads  80  are in the initial position inside the PCB  70  that is defined by a temporary hold of section  88  onto the upper surface of PCB  70  at around the hole  90 . Then, as shown in two split views in step three of  FIG. 8C  and step four of  FIG. 8D , device  60  goes through a smooth flip action taking advantage of the structural resistance of the flexible bend  85  of pin  86  and the penetrating section  88 . As each of the leads  80  slides against the inner wall of the hole  90  about its pivoting unit  84 / 85 , the length and weight of device  60  itself are utilized as a leverage in overcoming the resistance, which is only transitional. Then, in step five of  FIG. 8E  the device  60  ends its 90-degree swivel toward the other upper side of PCB  70  to complete the insertion.  FIG. 8E  shows the mounted position of device  60  on PCB  70  which is ready to undergo a soldering process. 
         [0077]      FIGS. 9 to 12  show a second electronic device  160  of the present invention that is a capacitor with two leads  180 , which are conductor rods similarly shaped to the lobster legs of the device  60  of the first embodiment. Both capacitor leads  180  have a common shape and thus will be referenced interchangeably to indicate different features of one of the leads. In  FIG. 10 , the device  160  is secured on PCB  70  to form a part of an electronic circuit  100 . 
         [0078]    Each of the leads  180  has a first straight section  181  extending vertically from a bottom side of device  160  that stands substantially upright from PCB  70  penetrating a thru-hole  172  of PCB  70 . The lower limit in sizing a PCB thru-hole is supposed to be set to slightly exceed the largest diameter of the round leads of components mounted to accommodate them with little resistance. The upper limit of hole  172  needs not to be within a tight tolerance without a concern of displacement of device  160  before and after a subsequent soldering process since the lead  180  holds device  160  onto PCB  70  without having to engage hole  172 . 
         [0079]    Second straight section of a parallel shank  183  extends from first section  181  via a first 90-degree bend  182  to make a flat engagement with PCB  70  at its dielectric upper surface. A vertical third straight section  188  of the lead running through the hole  172  interconnects the shank  183  via a second 90-degree bend  184  and the fourth straight section of a horizontal pin  187  via a third 90-degree bend  185 . The spaced second and third bends  184 ,  185  along with the connecting straight section  188  work in unity as a pivoting body when inserting device  160  into hole  172  during assembly. 
         [0080]    Pin  186  is terminated by a tip  187 , which is under gravity biased toward a circuit trace (not shown) until a mass of solder  50  is formed to cover the whole pin  186 . 
         [0081]      FIG. 11  clearly shows in plan view the parallel shanks  183  after assembly of device  160  while  FIG. 12  shows the same in bottom view. The length of shanks  183  may be shorter than illustrated to take up less area on the upper surface of PCB  70  as long as the pivoting body  184 / 185  is distanced from the center of gravity of device  160  to contribute to the flip down mounting of the same. Solder  50  may extend along the length of pin  186  and lies flat on the PCB  70  reducing the overall thickness of the electronic circuit  100 . 
         [0082]      FIG. 13A  depicts step one to align the leads  180  of device  160  to the hole  90  of PCB  70  wherein device  160  is oriented in parallel with PCB  70  facing each other at one upper side of PCB  70  so that pin  186  extends in the same direction as the hole  90 . Here, PCB  70  is positioned upright with the components side on top and the circuit traces for soldering facing down. In addition, PCB  70  with a single side circuit trace or one without plated thru-holes is suffice to work perfectly with the inventive auto-cling device  160  thus assembling the circuit  100  becomes more economical as well as uniform. 
         [0083]    In step two of  FIG. 13B , the lead  180  is in its initial position inside PCB  70  that is defined by a temporary hold of section  188  onto the upper surface of PCB  70  at around the hole  90 . Then, as shown sequentially in step three of  FIG. 13C  to step five of  FIG. 13E  the device  160  held is pivoted over 90 degrees about its pivoting body  184 / 185  toward the other upper side of PCB  70 .  FIG. 3E  shows the final position of device  160  on PCB  70  which is ready to be subjected to a soldering process. 
         [0084]    The electric device can be made as a transformer, transistor or capacitor. A wire bending machine can easily wire bend any of the leads of these common electrical devices into the stepped profile as shown in the drawings. The stepped profile provides an easier connection and more durable connection than the connection of the prior art. 
         [0085]    Therefore, while the presently preferred form of the automatic clinging leads of electric devices have been shown and described, and several modifications thereof discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.