SOLDER BEARING TERMINAL PIN

Abstract: In order to provide a solderable terminal pin that can be used with automated machinery, capable of inserting the terminal in a substrate, a terminal pin (10) is provided with fingers (16) which are crimped around a mass of solder (17).

Description: SOLDER BEARING TERMINAL PIN BACKGROUND OF THE INVENTION This invention relates to a solder bearing terminal pin for attachment to a receptacle in a substrate wherein a discreet mass of solder is mechanically held by the ter¬ minal in position to be melted for connecting the terminal to the receptacle with both an electrical and mechanical bond. The terminal is of a type which is capable of being continuously stamped from a thin sheet of metal at high speed, and because each terminal pin mechanically holds its own discrete mass of solder, the pins may be produced in¬ dividually or, preferably, attached to a common carrier strip for automated, machine insertion into the receptacle in the substrate. Various means have been provided wherein a quantity of solder is associated with a terminal pin so that when the terminal is inserted into a receptacle in a substrate (usually a hole drilled through the substrate with a metal surface plated on its interior and on the surface of the substrate around the periphery of the hole) and the assem- bly is heated, the molten solder covers the adjacent sur¬ faces of the terminal and receptacle to form, when cool, a soldered metallurgical joint between the terminal and receptacle. In the prior art individual terminal pins were pressed into the receptacle in the substrate and soldering was accomplished by either passing the entire substrate O PI > Λ over a solder wave machine or by applying solder to each individual terminal pin using a conventional soldering iron and solder. An alternative method used in the prior art has as- sociated the solder with each terminal pin by means of metallurgical bond between the solder and the pin wherein the solder was positioned in a location which was far re¬ moved from the receptacle in the substrate. This method suffered from the poor solder bond because the solder was required to migrate down the terminal pin before it could reach the junction between the terminal and the recept¬ acle which was to be soldered. SUMMARY The present invention provides a means for securely holding a discrete mass of solder adjacent to a terminal pin by means of mechanical attachment. At least one fin¬ ger from the terminal pin wraps securely around the mass of solder holding it firmly in position, and in the pre¬ ferred method of manufacture, stamping, the finger is wrapped so securely that it indents slightly into the surface of the softer solder mass thereby making it im¬ possible for the solder to become detached during handling prior to the application of heat and the completion of the soldering operation. OMPI - ύ - It is an object of the present invention to provide means for attaching securely a discrete solder mass to a terminal pin in a purely mechanical manner. It is a further object of the invention to provide a solder bearing terminal pin wherein each terminal has its own supply of solder in a convenient location for melting to form bonds with a receptacle. It is another object of the invention to provide a solder and terminal pin assembly which can be made by very simple and efficient stamping steps. It is a still further object of the invention to pro¬ vide certain improvements in the form, construction and arrangement of the parts whereby the above-named and other objects may effectively be attained. The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described,. and the scope of the in¬ vention will be indicated in the claims. BRIEF DESCRIPTION OF THE DRAWINGS Practical embodiments of the invention are shown in the accompanying drawings wherein; Figure 1 represents the front elevationnl view of two terminal pins according to the invention attached to a common carrier strip; Figure 2 represents a side view of the terminals shown in Figure 1; Figure 3 represents a partial front elevational view of the terminal according to Figure 1 inserted into a receptacle prior to the application of heat; Figure 4 shows the same partial front elevational view as Figure 3 after sufficient heat has been applied to cause the solder to flow and form a metallurgical joint; Figure 5 represents a partial front elevational view of a first modified form of the terminal shown in Figure 3; Figure 6 represents a partial front elevational view of a second modified form of the terminal in Figure 1; Figure 7 represents a partial side view of the odi- fied form shown in Figure 6; Figure 8 represents the front elevational view of two terminal pins of a third modified form attached to two common carrier strips; and' Figure 9 represents a side view of the terminals shown in Figure 8. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, Figure 1 shows two indi¬ vidual solder bearing terminal pins 10 connected to a common carrier strip 11. The carrier strip may be pro¬ vided with pilot holes 12 at regular intervals, as is customary, and the terminal pins may be connected to the carrier strip via break-away notches 13 for removal of the carrier strip after the terminal pins have been soldered into position. Each terminal pin includes an upper body portion 14, and a lower body portion 15, two fingers 16, a discrete solder mass 17, an upper contact arm 18, and a lower contact arm 19. The carrier strip 11 can be any length desired, car¬ rying a great number of terminal pins. The terminal pins and carrier strip are preferably made by continuously stamping them from a thin sheet of metal, and during the stamping operation, the fingers 16 are bent out of the plane of the body of the terminal pin and are wrapped at least partially around the discrete mass of solder 17. During the stamping operation, the fingers are preferably stamped to a thickness which is less than that of the body of the terminal pin. This allows the fingers 16 to be wrapped more readily around the discrete mass of solder 17. During the stamping operation, when the free ends of the fingers 16 are wrapped around the softer metal of the solder, the wrapping can be done with sufficient force to indent the fingers into the surface of the solder to provide a firm mechanical attachment between the solder and the terminal pin which prevents the solder from be¬ coming dislodged during shipping and handling, prior to the completion of the soldering operation. Referring to Figure 2, which is a side view of Figure 1, it can be seen that the fingers 16 are of a thickness which is less than the thickness of the body of the terminal pin. The thickness of the body portions 14 and 15 are, for convenience, usually but not necessarily, chosen to be of the same thickness as that of the upper and lower contact arms 18 and 19 respectively. This thickness may be adjusted during the stamping operation. In use, the contact arms may be soldered to an ad¬ jacent printed circuit board, may have wires or other electrical components soldered to them, may serve as pin or blade connectors for an electrical plug, may have a wire or wires conventionally wire wrapped onto them, may function as spring contacts, or may have other elec¬ trical and mechanical connections where appropriate. The fingers 16 are preferably stamped from the same thin sheet material as the remainder of the pin, and the thickness of the fingers is reduced during the stamping operation, allowing them to be more easily formed into the appropriate shape. Upper contact arm 18 may be of any suitable shape. If required, it may have a square cross section suitable for a wire wrapped connection, or a round cross section for a solder connection, and it may be straight or bent out of the plane of the terminal pin as indicated in the dashed lines 26 of Figure 2 to form a spring-like side contact arm. Lower contact arm 19 must be of a size such as to permit it to pass through the receptacle in the substrate which requires that its largest cross sectional dimension be no larger than the largest cross section di¬ mension of the lower body portion 15. Lower contact arm 19 may be eliminated entirely where desired, as may upper contact arm 18. In the latter case, carrier strip 11 would be attached directly to the upper body portion 14. Figure 1 illustrates the terminal pins connected to a carrier strip 11. While this is the preferred embodi¬ ment suitable for automated machine insertion into the substrate, it is also possible, due to the fact that each individual pin is firmly attached to its own solder mass, to use the pins individually as might be desired by the user of small quantities of pins. It is also possi¬ ble to remove individual pins from the carrier strip without disturbing the remainder of the pins which allows a customized template of pins to be inserted as a unit into a corresponding template of receptacles in a sub¬ strate. Figure 3 shows a detailed, front view of the terminal pin in Figure 1 inserted into a receptacle 20 in a sub- strate 21 which has been coated with a contact material 22 in the vicinity of the receptacle and on its interior surface. It can be seen that the lower body portion 15 has been sized to closely fit the receptacle in the substrate, which provides a good electrical contact after soldering. The receptacle in Figure 3 consists of a hole drilled through the substrate 21 and plated through with a contact material 22. Figure 3 also illustrates how the fingers 16 hold the solder in close proximity to the lower body portion 15 and the receptacle 20 prior to the application of heat and the completion of the soldering operation. Figure 4 is a detailed view of the metallurgical joint formed between the terminal pin and the receptacle in the substrate after the pin and substrate have been heated sufficiently to melt the solder. It can be seen that the solder flows completely around the lower body portion 15, bonding the lower portion of the contact ma¬ terial on the substrate, the interior of the receptacle, and the fingers 16 to the terminal pin. Figure 5 shows a modified form of the terminal pin wherein a longitudinal slot 23 has been cut through the lower body portion 15. The longitudinal slot 23 and lower body portion 15 are correctly sized with respect to the thickness of the substrate 21 and the diameter of the receptacle 20 so that the lower body portion is slightly over-sized with respect to the receptacle 20 prior to in- sertion, and a tight compressive fit is achieved after insertion. A pin which produces such a tight compressive fit is commonly known as a compliant pin. A compliant pin produces a temporary bond between the terminal pin and the receptacle which allows additional handling of the elec- trical assembly such as the insertion of other electrical components prior to soldering, without fear that the previously inserted terminal pins will become dis¬ lodged during the additional handling. The use of a longitudinal slot 23 to produce a compliant pin has an additional advantage of allowing the use of individual pins, not attached to a carrier strip which are extremely susceptible to dislodgement when disconnected from their carrier strip. A further advantage associated with the use of longitudinal slot 23 to provide a compliant pin is that the slot forms a flow channel for the molten solder to reach the underside of the substrate 21. This is especially important where the cross sectional shape of the lower contact pin 15 and the receptacle 20 are approximately identical, in which case the solder is prevented in the absence of a longitudinal slot 23 from reaching the lower surface. Longitudinal slot 23 also provides additional surface area to allow for a better mechanical and electrical bond between the lower body portion 15 and the receptacle 20. Referring to Figure 6, the second modified form of the terminal pin is shown as having a single central finger 24 formed from a U-shaped longitudinal cut 25 along the axis of the body. The U-shaped longitudinal cut 25 can be extended down the axis of the lower body portion 15 to perform the same function as longitudinal slot 23 to provide a compliant pin. Figure 7 is a side view of the second modified form shown in Figure 6. It can be seen in both Figures 2 and 7 that the engaging fingers . 16 and 24 wrap partially a- round the mass of solder 17 holding it in the gap formed between the finger or fingers and the body of the termi¬ nal pin. The fingers can wrap partially or completely around the solder mass as desired, and the solder mass may be of any suitable shape. It is of particular value to have the finger indent into the surface of the softer solder mass when only a single finger is used for attach¬ ment to prevent the solder from becoming disengaged from the terminal pin prior to the application of heat. Figure 8 is a front elevational view of two terminal pins of a third modified form connected to two common carrier strips, an upper carrier strip 27 and a lower carrier strip 28, both of which are provided with the customary pilot holes 12. In this modified form the upper contact arm 29 is a cantilever spring blade contact with a central longitudinal slot 30 which provides ad¬ ditional spring action to the upper contact arm 29. The two common carrier strips, 27 and 28, provide additional rigidity for the attached terminal pins, which keeps them in accurate alignment during shipping and handling prior to their insertion into the receptacle. Figure 9 is a side view of the third modified form shown in Figure 8. It can be seen in this view that the upper contact arm 29 has been stamped to a thickness which is less than that of the body of the terminal pin which provides additional spring action. An upper break-away notch 31 and lower break-away notch 32 can also be clearly seen in this figure. In each of the terminal pins described above, the mass of solder is in mechanical engagement with the terminal fingers in position to be melted for the forma¬ tion of a bond between the terminal fingers 16, the ter- minal body 14 and 15 and the receptacle 20 in the sub¬ strate 21. The solder mass may, if desired, have a cross section of circular, square or other geometrical form, or be made from spherical pellets. Although Figure 8 has been drawn with two fingers 16, it is apparent that it can be constructed with a single central finger 24 as shown in Figures 6 and 7. It also can be constructed with or without a central longitudinal slot 30 or a longitudinal slot 23 as de¬ sired. Furthermore, a lower carrier strip 28 may be used in conjunction with any of the terminal pins shown and where such a lower carrier strip is used, the upper carrier strip is optional. Each terminal can also be made by simple stamping and assembling steps, with mini¬ mal waste of material. It will thus be seen that the objects set forth above, among those made apparent from the preceeding description, are efficiently attained and, since certain changes may be made in the above article without de¬ parting from the spirit and scope of the invention, it is intended that all matter contained in the above descrip¬ tion and shown in the accompanying drawings shall be in¬ terpreted as illustrative and not in a limiting sense.

Claims: What I Claim Is : 1. A terminal pin adapted to be soldered into a re¬ ceptacle in a substrate comprising, an elongated body portion having an upper body portion and a lower body portion, said lower body portion being sized to fit into the receptacle in the substrate, and at least one contact arm attached to the body portion, said body portion being cut longitudinally to define at least one finger having a fixed end attached to the body portion and a free end, said finger or fingers being bent out of the plane of the body portion the free end of said finger or fingers being wrapped at least partially around a discrete mass of solder, whereby the mass of solder is held in close pro¬ ximity to both the lower body portion and the receptacle in the substrate when the lower body portion is inserted into the receptacle. 2. A terminal pin according to Claim 1 wherein the body portion is cut longitudinally along two lines to de¬ fine two fingers separated by the upper body portion, both of said fingers being wrapped at least partially around the mass of solder. 3. A terminal pin according to Claim 1 the cut in the body portion is substantially U-shaped to de¬ fine a central finger between spaced portions of the body portion, said central finger being wrapped at least partially around the mass of solder. - 1.5 - 4. A terminal pin according to Claim 1 wherein the lower body portion has a longitudinal slot along its axis, the width of said slot and said lower body portion being chosen to provide a compressive fit between the lower body portion and the receptacle in the substrate. 5. A terminal pin according to Claim 1 wherein the finger or fingers and the contact arm or arms are of a thickness which is less than the thickness of the body portion. 6. A terminal pin according to Claim 1 wherein the finger or fingers are indented into the surface of the mass of solder for holding the mass securely in position. 7. A terminal pin according to Claim 1 wherein the terminal pin has one upper contact arm attached to and axially aligned with the upper body portion, and one lower contact arm attached to and axially aligned with the lower body portion, said lower contact arm being at least as small in its thickness and width as the lower body portion to allow the lower contact arm to pass through the receptacle in the substrate. 8. A terminal pin according to Claim 7 wherein the upper contact arm is bent out of the plane of the body portion at approximately the point of attachment to the upper body portion, and bent reflexively back towards the plane of the body portion near the tip of the upper con¬ tact arm providing a spring-like contact arm. 9. A terminal pin according to Claim 1 wherein the mass of solder is secured in a gap formed between the finger or fingers on one side, the body portion on the opposite side, and the wrapped free end of the finger or fingers below. 10. A terminal pin according to Claim 1 wherein the finger or fingers are bent out of the plane of the body portion at a point approximately adjacent to the point of attachment of said finger or fingers to the body por- tion. 11. A terminal pin according to Claim 1 wherein the upper contact arm comprises a spring-like blade contact with a central longitudinal slot. 12. A plurality of terminal pins according to Claim 1 wherein at least one of the contact arms of each terminal pin is connected to a common carrier strip. 13. A plurality of terminal pins according to Claim 12 wherein each terminal pin has two contact arms, an up¬ per contact arm and a lower contact arm, and the upper contact arm of each terminal pin is connected to an upper carrier strip, and the lower contact arm is connected to a lower carrier strip.

Inventors: SEIDLER JACK, SEIDLER, JACK
Applicants: NORTH AMERICAN SPECIALITIES, NORTH AMERICAN SPECIALTIES CORPORATION
Application year: 1983
Main classification: H01R4
IPC codes: H01R4, H05K3