BACKGROUND OF THE INVENTION

The present invention relates to connector devices for surface mounting an electrical component having multiple terminal leads (such as an integrated circuit chip or the like) to a printed circuit board or other substrate. It also relates to methods for fabricating such devices, and for mounting components by use of such devices.

SUMMARY OF THE INVENTION

On computers or the like it is frequently desirable to surface- mount an integrated circuit, microprocessor chip or other multi-legged electrical component, on a printed circuit board or other substrate for connection to circuits on the substrate. Such components usually have a plurality of terminal leads extending in one or more-parallel rows perpendicular to the component, the leads of each row being spaced correspondingly to conductive areas or pads on the substrate, which lead to circuits or other components on the substrate.

To facilitate removably mounting all these legs on the substrate, it has been known to secure to each conductive pad a connector receptacle to engage a lead inserted therein, to form an electrical connection between the lead and the conductive pad, and also to serve to retain the leads (and thereby the component) on the substrate.

This procedure offers practical difficulties because of the very close spacing of the leads, conventionally spaced .100 inch or .050 inch.

One method previously in use has involved providing the required number of connector receptacles in the form of tiny metallic housings, formed by machining or cold heading. A separate spring contact member is inserted in each housing. The housings are inserted into a plastic supporting sheet to hold the housings in position. Solder paste is applied to the bottom of each housing, and the assembly is placed on the corresponding array of substrate conductive pads. Heat is applied to the solder to melt it (without affecting the supporting sheet) so that on cooling each housing is joined to a respective conductive pad. Thereafter the plastic support sheet is removed by peeling off from the housings.

The present invention provides a more economical and more highly automatable method and device for securing the requisite receptacle contacts to the substrate. In accordance with the invention, the contacts and their internal spring contacts are formed in one piece by progressive stamping a continuous strip of conductive material to form a single or double array of properly spaced contacts held in proper relative position by a carrier strip integral with the contacts. These may be hundreds or thousands of contacts joined to the strip. A section of this strip has its contacts applied to and soldered to respective substrate conductive pads. Thereafter the carrier strip is severed from the receptacles by a simple cutting stroke, leaving the contacts secured to respective conductive pads, in the proper location to receive the leads of the leads of the multi- legged component.

Additional objects and advantages of the present invention will become apparent from the following description of the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a perspective view of an electrical component to

3 be surface mounted on a substrate.

Fig. 2 is an end view of the device of Fig. 1 .

Fig. 3 is a diagrammatic plan view of a representative substrate on which the component of Figs. 1 and 2 is to be mounted. Fig. 4 is a plan view of a blank of electrically conductive material used in the present invention, at an intermediate stage of its fabrication.

Fig. 5 is a similar plan view of a fully formed strip of contact joined to a carrier strip according to the invention. Fig. 6 is a perspective view of a single fully formed contact.

Fig. 7 is an elevation cross-sectional view of a contact of Fig. 6.

Fig. 8 is an exploded perspective view of an electrical component and a substrate having contacts in accordance with the invention, to which the component may be connected.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, Figure 1 shows in perspective view a representative electronic component to be surface-mounted on a substrate. The component has a body 1 1 and a plurality of terminal leads or legs 13 extending perpendicularly downward from the body 1 1 . The leads 13 are commonly spaced .050 inch or .100 inch apart. The leads 13 may be on one or both of the sides of the component 1 1 , and are here shown extending along both sides of the component 1 1 . The component 1 1 is desired to be mounted on a substrate 15 illustrated in Figure 3. This substrate 15 has a plurality of spaced conductive areas or pads 17 which in some instances are the terminal areas for wiring on the substrate. The spacing of the conductive pads is matched to that of the terminal leads 1 1 as schematically illustrated in Figure 3.

The present invention provides a connection arrangement between the component 1 1 and the substrate 15. This connection arrangement is made from an elongated strip 17 of conductive material (such a beryllium copper) which is slightly resilient, by a process of progressive stamping. Figure 4 shows a fragment of the strip 17 at an intermediate stage of the stamping of the strip 17. At this stage, the strip 17 has a central region 19, having spaced indexing or sprocket holes 21 along its center line. Extending laterally outward from both sides of the center area 19 are a plurality of arms 23, which are spaced along the strip 17 in correspondence with the spacing of the leads 13 of the electrical component 1 1 . Each arm 23, 23a has a generally circular center region 25 joined drawn to the center region 19 by an inner or proximal straight section 27 and also has an outer or distal straight section 29 extending outwardly from center region 9. Each distal section 29 has a U-shaped cut 30 formed on it to provide a tongue 31 joined to section 29 at the outer end of tongue 31 . Inner section 27 is joined to the carrier strip 19 by a narrow connecting neck 33 so that the carrier strip 19 carries the entire array of arms 23. The array may have any desired number of arms, up to the thousands of arms. In subsequent stages of the progressive stamping operation, each arm 23 is formed into a receptacle contact 39 shown in Figures 5, 6 and 7. The central area 25 is deep drawn by conventional means into a seamless cup 31 having a closed bottom or end, shown more clearly in Figures 6 and 7. To facilitate the drawing operation, such as openings 41 may be formed in the strip at appropriate position 1 . Similar openings may be provided on the proximal section 27 of each arm preferably close to the carrier strip 19 so as to be spaced away from the seamless bottom of the cups 35. The inner and outer sections 27, 29 of arms 23 are bent and curved to form an essentially cylindrical upper extension 39 of the cup 35, with a seam 37 where the two semi-cylindrical sections are juxtaposed.

Concurrently, the finger 31 is bent inwardly of the cup 35 and cylinder 39, so that on insertion of a terminal lead 13 into the receptacle contact formed by cup 35 and its extension cylinder 39, as shown in Figure 7, the finger 31 will make electrical contact with the lead 13 and also will aid in 5 retaining the component by frictional engagement with the leads of the component. Illustratively for leads spaced 0.100 inch, the receptacle contact may have a diameter of about .053 inch, and a depth of about .090 inch.

In use, a section of the strip of Figure 5, carrying the requisite 10 number of receptacle contacts 35 is severed from the remaining strip and is positioned on the substrate 43 with the lower surfaces of the cups 35 juxtaposed to the respective conductive pads 17 of the substrate 15. Solder paste is applied either to the conductive pads 17 or to the lower surface of the cups 35, to be interposed between each cup 35 and a 15 respective conductive pad 17. The solder is reflowed and then solidified to solder each cup 35 to a respective conductive pad 17.

Thereafter, the receptacle contacts 39 are severed from the carrier strip 19 at the narrow neck 33, leaving each receptacle contact 39 individually soldered to a respective conductive pad, as shown in Figure 20 8.

This arrangement has the advantage that the cup 35 (which may extend for approximately 30-50% along the height of the entire receptacle 39) is seamless, so that any tendency of the solder during reflow to migrate upwardly along the receptacle 39 is ineffective to cause 25 solder to enter the interior of the receptacle contact 39, as otherwise might occur where the receptacle is made simply by rolling the material into a cylindrical form.

It will be seen at the present method leads itself readily both to automated fabrication and assembly to a substrate. The progressive

_30 stamping operation starts with an ordinary flat strip and provides the

required array of receptacle contacts. The requisite number of contacts may be cut from the longer strip automatically and positioned automatically on the substrate by conventional means. The severing of the cups from the carrier strip section after soldering is also readily accomplished automatically.

Accordingly, the present invention has provided a superior arrangement for receiving a multi-legged component on the surface of a substrate, which may be automated for rapid and economical production.