Electrical pin tips

Abstract: An electrical terminal pin (104) for use in interconnecting electrical leads, plated through holes in printed circuit boards and/or connector contacts has a terminal pin tip (102) on an insertion end (103), which has a conductive core (108) and a conductive outer layer (110). A non-plated flat end (116) of the core (108) has one or more curved sides (112) plated with the layer (110) and at least one edge (118).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention. This invention relates to electrical terminal pins for use in interconnecting electrical leads, plated through holes in printed circuit boards and/or connector contacts and, in particular, to electrical terminal pin tips on insertion ends of the pins. 2. Description of Related Art. It is well known in the connector art to use electrical pins to interconnect electrical leads, plated through holes in printed circuit boards and/or connector contacts. Such pins typically have square or round cross sections perpendicular to their longitudinal axes. The pins are made from an electrically conductive material, such as copper, brass, phosphor bronze, beryllium copper or the like. It is further known to plate or coat the pins with a conductive layer, such as tin, nickel, pladium, gold, silver or a suitable alloy. Pins are plated in order to apply a layer on a pin core that does not oxidize as much as the material of the core. Less oxidation at an electrical connection improves electrical performance. Pins are made with a core material different than the plating material in order to reduce the cost of the pin and/or to make the pin more rigid than if the pin was entirely made out of the plating material. It is well known in the art to make pin tips with flat tapered sides to facilitate alignment with and/or insertion into a plated through hole or a mating contact. For instance, Figure 1 shows an enlarged perspective view of an electrical terminal pin tip 2 of a prior art electrical terminal pin 4 with a portion broken away to show a cross section 6 of the pin 4. The pin 4 comprises an electrically conductive inner core 8 plated with an electrically conductive outer layer 10. Figure 2 is an end view of the prior art electrical pin tip 2 of Figure 1. Referring to Figures 1 and 2, the pin tip 2 has a pair of opposed flat swaged plated sides 12 that taper or slope towards a longitudinal axis of the pin 4 as the pin 4 approaches its longitundinal end. The pin tip 2 further has a pair of opposed flat trimmed non-plated sides 14 that taper or slope towards the longitudinal axis of the pin 4 as the pin 4 approaches its longitundinal end. The opposed flat trimmed non-plated sides 14 are jointed at the longitudinal end by a trimmed non-plated curved or cylindrical surface 16. When this tip 2 is inserted into a plated through hole or a female contact, the plated through hole or the female contact can slide against the non-plated tapered sides 14 causing some of the core material to be transferred onto the plated through hole or the female contact. Multiple insertions and withdrawals of the pin 4 into plated through holes or mating female contacts increase the probability of rubbing some of the core material off the non-plated sides 14 onto the plated through holes or mating female contacts. This transferred core material can ultimately be dragged or positioned between the pin plating 10 and the plated through hole or the female contact. Depending on the materials used for the core 8 and the plating or layer 10, this may increase the oxidation rate of the connection between the pin 4 and the plated through hole or the female contact, compared to a connection directly between pin plating 10 and the plated through hole or the female contact. Other pin tips are shaped by trimming which removes plating material from trimmed flat sides. Then one or more additional process step is performed to plate the trimmed sides. Although this ensures that all exterior sides and surfaces of the pin tip are plated, it adds time and cost to the manufacturing process. It is typical to simultaneously insert a plurality of pins, such as, mounted in a connector housing, into a mating set of plated through holes or female terminals. The insertion force required increases with the number of pins being inserted and can be significant. Tapered flat sides on pin tips reduce the insertion force required. However, it is desirable to further reduce the longitudinal insertion force without reducing the lateral retention force applied on the pin by the plated through holes or female terminals. It is desirable to provide a pin tip that satisfies the above described needs and overcomes the above described disadvantages of the prior art. EP-A-0232103 describes an electrical plug pin and an associated receptacle. The pin has a substantially rectangular cross-section with arcuate side comers or outer faces. The pin has a tapered tip to guide the pin into the receptacle and the pin may be plated with a coating layer. EP-A-0338938 describes a male contact element designed to require a low insertion force. The contact element has a cylindrical pin portion prolonged by a tapered portion terminating in a curved nose or a curved nose with a planar end surface. As is known from EP-A-0232103, the present invention provides an electrical terminal pin tip for inserting into an electrical female terminal or into a plated - through hole of a printed circuit board; the pin tip having an exposed flat end surface, a longitudinal axis of symmetry extending through the centre of the flat end surface, the pin tip being composed of an inner core made of electrically conductive material and a plating layer on the outside of the core. In contrast to EP-A-0232103 and in accordance with the invention there is at least one outer curved transition surface extending in an arc from the flat end surface towards a region of the tip having a greater cross-sectional area than the flat end surface and the plating layer extends over said curved surface but not over the flat end surface. BRIEF DESCRIPTION OF THE DRAWINGS The invention can be more fully understood from the following detailed description thereof in connection with the accompanying drawings described as follows. Figure 1 is an enlarged perspective view of an electrical terminal pin tip of a prior art electrical terminal pin with a portion broken away to show a cross section of the pin. Figure 2 is an end view of the prior art electrical pin tip of Figure 1. Figure 3 is an enlarged perspective view of a first embodiment of an electrical terminal pin tip on an end portion of an electrical terminal pin with a portion broken away to show a cross section of the pin in accordance with the present invention. Figure 4 is a end view of the electrical terminal pin tip of Figure 3. Figure 5 is a side view of the electrical terminal pin having a pair of the electrical pin tips of Figures 3 and 4. Figure 6 is an enlarged perspective view of a second embodiment of an electrical terminal pin tip on an end portion of an electrical terminal pin with a portion broken away to show a cross section of the pin in accordance with the present invention. Figure 7 is an end view of the electrical terminal pin tip of Figure 6. Figure 8 is a side view of an electrical terminal pin having a pair of the electrical pin tips of Figures 6 and 7. Figure 9 is an enlarged perspective view of a third embodiment of an electrical terminal pin tip on an end portion of an electrical terminal pin with a portion broken away to show a cross section of the pin in accordance with the present invention. Figure 10 is an end view of the electrical terminal pin tip of Figure 9. Figure 11 is a side view of an electrical terminal pin having a pair of the electrical pin tips of Figures 9 and 10. DESCRIPTION OF THE PREFERRED EMBODIMENT (S) Throughout the following detailed description, similar reference characters refer to similar elements in all figures of the drawings. Referring to Figure 3, there is illustrated an enlarged perspective view of a first embodiment of an electrical terminal pin tip 102 in accordance with the present invention. The pin tip 102 is on an end portion 103 of an electrical terminal pin 104 with a portion broken away to show a cross section 106 of the pin 104. The electrical terminal pin 104 is for inserting tip first into and electrically connecting to an electrical female terminal or a plated-through hole of a printed circuit board. Figure 4 is a end view of the electrical terminal pin tip 102 of Figure 3. Figure 5 is a side view of the electrical terminal pin 104 having a pair of the electrical pin tips 102,102' of Figures 3 and 4. Referring to Figures 3-5, the electrical terminal pin 104 comprises an electrically conductive core 108 and a conductive layer 110. The conductive layer 110 is plated on a perimeter of the core 108 at least near or immediately adjacent an end of the pin 104. The pin 104, the core 108 and the plating or layer 110 are symmetric about a longitudinal axis 107 of symmetry. The pin tip 102 comprises a non-plated substantially flat end or end surface 116 of the core 108 and at least one curved side or outer curved transition surface 112 substantially plated with the conductive layer 110. Preferably, the non-plated substantially flat end 116 is substantially perpendicular to the axis 107 of symmetry. Further, the non-plated substantially flat end 116 has at least one edge 118. In the embodiment illustrated in Figures 3-5, the non-plated substantially flat end 116 is substantially square with four edges 118. Since there is one curved side 112 corresponding to each edge 118, there are four curved sides 112. Each one of the curved sides 112 extends from a corresponding one of the substantially flat end edges 118 away from the longitudinal axis 107 to a perimeter 105 of the pin 104 near or immediately adjacent the pin tip 102. Preferably, the curved sides 112 are shaped substantially alike. The conductive layer 110 entirely covers each one of the curved sides 112 at least from the pin perimeter 107 to half way along the side 112 to the non-plated flat end 116. Preferably, each one of the curved sides 112 is a convex portion of a corresponding cylinder. It is also preferred that the plated curved sides 112 intersect the pin perimeter 107 at an angle tangent to the corresponding cylinder. The pin 104 may further comprise a second pin tip 102' on another end of the pin 104 distal to the first tip 102. The second tip 102′ can be a mirror image of the first tip 102. In other words, the second tip 102′ can have the same shape as the first tip 102 but it can be rotated 180 degrees. Alternatively, the second pin tip 102′ can be configured like any other tip described herein or elsewhere. Figure 6 is an enlarged perspective view of a second embodiment of an electrical terminal pin tip 202 on an end portion 203 of an electrical terminal pin 204 with a portion broken away to shown a circular cross section 206 of the pin 204 in accordance with the present invention. Figure 7 is an end view of the electrical terminal pin tip 202 of Figure 6. Figure 8 is a side view of an electrical terminal pin 204 having a pair of the electrical pin tips 202,202′ of Figures 6 and 7. The second electrical terminal pin tip 202 is the same as the first electrical terminal pin tip 102, except the second electrical terminal pin tip 202 has a non-plated substantially flat end 216 which is substantially circular with only one circular edge 218. Further, it has only one curved side 212. The side 212 is convex and comprises a truncated sphere or ellipsoid. The second electrical terminal pin end portion 203 has a pin perimeter 205 near or immediately adjacent the pin tip 202 that is substantially circular. Figure 9 is an enlarged perspective view of a third embodiment of an electrical terminal pin tip 302 on an end portion 303 of an electrical terminal pin 304 with a portion broken away to show a cross section 306 of the pin 304 in accordance with the present invention. Figure 10 is an end view of the electrical terminal pin tip 302 of Figure 9. Figure 11 is a side view of the electrical terminal pin 304 having a pair of the electrical pin tips 302,302′ of Figures 9 and 10. The third electrical terminal pin 304 has a first pin tip 302 connected to an electrical terminal pin end portion 303. The first pin tip 302 is the same as the first pin tip 102 illustrated in Figures 3-5, except where the first pin tip 302 joins the end portion 303. The pin end portion 303 is the same as the pin end portion 203 illustrated in Figures 6 and 8, except where the pin end portion 303 joins the pin tip 302. The electrical terminal pin tip 302 has a non-plated substantially flat end 316 which is substantially square. The electrical terminal pin tip 302 has four convex sides 312. The electrical terminal pin portion 303 has a pin perimeter 305 near or immediately adjacent the pin tip 302 that is substantially circular. The plated four convex sides 312 intersect the circular pin perimeter 305 at arced edges 320. Each end of the arced edges 320 intersects with an end of an adjacent one of the arced edges 320. The electrical terminal pins 104,204,304 of the present invention can be made from any suitable metal used for electrical terminals, such as brass, phosphor bronze, beryllium copper and the like. The electrical terminal pins 104,204,304 may be plated or coated with any conductive layer 110,210,310, such as tin, nickel, pladium, gold, silver or a suitable alloy. The electrical terminal pins 104,204,304 of the present invention can be made from a plated wire. The wire can be swaged around its perimeter forming a pair of the pin tips 102,202,302 at the same time connected together at their flat ends 116,216,316. Adjacent pins can be separated by applying opposing lateral forces on the pins or by twisting one with respect to the other. The first, second and third electrical terminal pin tips 102,202,302, respectively, of the present invention have a greater mechanical advantage than the prior art tip 2 illustrated in Figures 1 and 2. This is the case because the slope of the sides 112,212,312 progressively decreases from the flat end 116,216,316 to the ends or arcs 320 of the sides 112,212,312 intersecting the perimeter 105,205,305. Thus, when the tip 102,202,302 is almost entirely inserted in the plated through hole or the mating female terminal, the slope of the side(s) 112,212,312 is providing a reduced longitudinal opposing force than the prior art pin 4 when the prior art pin 4 is inserted the same distance in the plated through hole or the mating female terminal. In other words, the longitudinal insertion force required to insert a pin with the first pin tip 102, the second pin tip 202 or the third pin tip 302, tip first into, for instance, a plated through hole or a mating female terminal, is less than the longitudinal insertion force required to insert the pin 4 illustrated in Figures 1 and 2 tip first. Further, the lateral retention force applied on the first pin 104, the second pin 204 or the third pin 304 by a plated through hole or a mating female terminal is the same or substantially the same as the lateral retention force applied on the pin 4 illustrated in Figures 1 and 2. Those skilled in the art, having the benefit of the teachings of the present invention as hereinabove set forth, can effect numerous modifications thereto. These modifications are to be construed as being encompassed within the scope of the present invention as set forth in the appended claims.

Claims: An electrical terminal pin tip (102,102',202,202',302,302') for inserting into an electrical female terminal or into a plated - through hole of a printed circuit board; the pin tip having an exposed flat end surface (116,216,316), a longitudinal axis (107,207,307) of symmetry extending through the centre of the flat end surface, the pin tip being composed of an inner core (108,208,308) made of electrically conductive material and a plating layer (110,210,310) on the outside of the core characterised in that there is at least one outer curved transition surface (112,212,312) extending from the flat end surface in an arc towards a region of the tip having a greater cross-sectional area than the flat end surface and the plating layer (110,210,310) extends over said curved surface (112,212,312) but not over the flat end surface (116,216,316). The electrical terminal pin tip of claim 1, wherein the flat end surface (116) is square with four edges (118). The electrical terminal pin tip of claim 1, wherein the flat end surface (216) is circular with only one circular edge (218). The electrical terminal pin tip of claim 1 or 2, wherein there are several curved surfaces (112,312) which are all shaped substantially alike. The electrical terminal pin tip of claim 1 or 2, wherein there are several curved surfaces and the conductive layer (110) entirely covers each one of the curved surfaces (112) at least from a perimeter near the pin tip to half way along the surface towards the flat end surface. The electrical terminal pin tip of claim 1, wherein there is only one curved surface (212) and this surface comprises a truncated sphere or truncated ellipsoid. The electrical terminal pin tip of claim 1, wherein there are several curved surfaces (312) and each one of the curved surfaces is a convex portion of a cylinder. The electrical terminal pin tip of any one of claims 1 to 7, wherein the flat end surface (116,216,316) is perpendicular to the axis of symmetry. An electrical terminal pin end portion (103,203,303) for inserting in and electrically connecting to an electrical female terminal or a plated through hole of a printed circuit board, the pin end portion comprising: an electrical terminal pin tip (102,102',202,202',302,302') for inserting into an electrical female terminal or into a plated - through hole of a printed circuit board; the pin tip having an exposed flat end surface (116,216,316), a longitudinal axis (107,207,307) of symmetry extending through the centre of the flat end surface and a perimeter (105,205,305) extending about the longitudinal axis at a region of the end portion having a greater cross-sectional area than the flat end surface (116,216,316), the pin tip being composed of an inner core (108,208,308) made of electrically conductive material and a plating layer (110,210,310) on the outside of the core; characterised in that there is at least one outer curved transition surface (112,212,312) extending in an arc from the flat end surface towards the perimeter (105,205,305) and the plating layer (110,210,310) extends over said curved surface (112,212,312) but not over the flat end surface (116,216,316). The electrical terminal pin end portion of claim 9, wherein the perimeter (105) is square and the non-plated flat end surface (116) is square. The electrical terminal pin end portion of claim 9, wherein the perimeter (205) is circular and the flat end surface (216) is circular. The electrical terminal pin end portion of claim 9, wherein the perimeter (305) is circular and the flat end surface (316) is square. The electrical terminal pin end portion of claim 9, wherein there are several curved surfaces (312) and each one of the curved surfaces is a convex portion of a cylinder and the curved surfaces intersect the perimeter (315) at an angle tangential to the cylinder. The electrical terminal pin tip end portion of claim 9, wherein there is only one curved surface (212) and the surface comprises a truncated sphere or truncated ellipsoid. The electrical terminal pin end portion of any one of claims 9 to 14, wherein the flat end surface (116,216,316) is perpendicular to the longitudinal axis (107,207,307). An electrical terminal pin incorporating the tip end portion of any one of claims 9 to 15. The electrical terminal pin of claim 16 and further comprising a second pin tip (102',202',302') having: a further non-plated exposed flat end surface with the longitudinal axis extending through the centre of the further end surface and at least one further curved transition surface plated with the conductive layer, extending in an arc from the further flat end surfaces to the perimeter.

Inventors: AIKENS PAUL WAYNE, LYONS THOMAS BARRY, AIKENS, PAUL WAYNE, LYONS, THOMAS BARRY
Applicants: CONNECTOR SYSTEMS TECH NV, CONNECTOR SYSTEMS TECHNOLOGY N.V.
Application year: 1992
Main classification: H01R9
IPC codes: H01R12, H01R13, H01H1, H01R43