Solderless Electrical Connection System

Abstract

A solderless electrical connection system is shown having a main mounting board with a plurality of plated-through holes therein. A conductive electrical contact including a central section is pressed into the plated-through holes with the central section thereof flexing as it is urged into the hole and yielding to generate retention forces therein without destroying the hole. The flexing central section of the contact provides a gas seal between the plated-through hole and the contact for preventing deterioration of electrical continuity therebetween. Each end of the conductive contact may be provided with a configuration which allows electrical components to be mounted thereby or attached thereto.

Description

The present invention relates to a solderless electrical connection system and, more particularly, to a system for mechanically mounting components upon a main mounting board, for electrically interconnecting the components, and for electrically connecting the interconnected components to external devices without requiring solder or other previously utilized technique.

It is well known in the prior art to utilize a main mounting board or mother board of considerable size to receive or mount a plurality of printed circuit boards or daughter boards through the utilization of electrical connectors. Such an arrangement is shown in patent application Ser. No. 760,499, by James Scaminaci, Jr. et al., filed Sept. 18, 1968, for Method of Packaging Electrical Connectors and Assembling Same Into A Wire Wrap Machine, now U.S. Pat. No. 3,641,666 issued on Feb. 15, 1972. This patent is assigned to the same assignee as the present invention.

The prior art typified by the above-referenced patent utilizes a connector, such as a board-edge connector, to provide the mechanical mounting between the mother board and the daughter board. The board-edge connector mounts connector pins having wiping fingers for contacting conductive strips upon the daughter board inserted into the connector and non-rounded opposite end sections extending from the connector. The connectors, in turn, are bolted upon the mother board while electrical connection from each daughter board is achieved by wrapping wire about the non-round end sections of the contacts within each connector.

Some prior art devices have utilized solderless electrical contacts within a mounting board. However, these devices have relied on the principle of deforming the hole as the contact is inserted therein for generating the retention force. This prior art solderless contact can not be removed and reinstalled in the mounting board due to the destruction of the hole during the original deforming installation. The prior art contacts also have a tendency to become less efficient over a prolonged period of time due to loss of both mechanical holding power and electrical continuity. The loss of mechanical holding power is caused by the initial deformation of the mounting board which tends to continue long after the mounting of the contact, thus allowing the contact to loosened within the hole. The loss of electrical continuity is caused when ambient atmosphere circulates between the contact and the hole opening allowing the development of corrosion therebetween.

Accordingly, it is an object of the present invention to provide an improved solderless electrical connector system.

Another object of the present invention is to provide an electrical connector system which may be assembled and reassembled for ease of service and which utilizes only those connector components necessary for the full circuit design.

Still another object of the invention described herein is to provide an improved solderless electrical contact which may be utilized without destroying the aperture into which the contact is placed.

A further object of this invention is to provide a solderless electrical contact for use within an electrical connector system which may be replaced when required without destroying the contact or the contact mounting board which receives that contact.

Still a further object of the invention described herein is to provide an improved solderless electrical contact which may be inserted in a mounting board by a relatively low insertion force, which cleans the aperture within the mounting board during insertion, which provides a gas tight seal between the aperture and the contact to prevent the deterioration of electrical continuity, and which does not loose its mechanical holding force due to aging.

In accomplishing these and other objects, there is provided an insulated mounting board having a plurality of apertures therein. The mounting board may include single layer conductors or multi-layer conductors connected to selected apertures which are each coated with conductive material along the inner surface. A contact having a wedge locking central section is inserted into the desired apertures wherein the central section yields symmetrically about the longitudinal axis thereof for generating the desired holding force without distorting or destroying the aperture. The contact consists of an end portion for mechanically mounting an electrical component while providing electrical continuity thereto. The connector may further consist of a non-round end portion utilized for attaching wire thereto. The central section and end portions of the contact achieve mechanical and electrical mounting of electrical components without soldering, dip soldering, or other conventional means.

Other objects have many of the attendant advantages of the present invention will become better understood by those skilled in the art after careful review of the following specification when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view showing a solderless electrical contact of the present invention prior to insertion within a mounting board;

FIG. 2 is a side elevational view of the solderless electrical contact;

FIG. 3 is a front elevational view of the solderless electrical contact;

FIG. 4 is a cross-sectional view taken along lines 4--4 of FIG. 3 showing the central section of the electrical contact;

FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 3;

FIG. 6 is a perspective view illustrating the solderless electrical contact embodied within an electrical connection system;

FIG. 7 is a cross-sectional view showing the electrical contacts of the present invention mounted in the mounting board with a protective guide in the desired position;

FIG. 8 is a perspective view, similar to FIG. 6, illustrating the solderless electrical contact of the present invention embodying a second arrangement of the electrical connection system; and

FIGS. 9-14 are cross-sectional views, similar to FIG. 4, illustrating various embodiments of the central section of the solderless electrical contact.

Referring now to the drawings, FIG. 1 shows a solderless electrical contact 10 arranged to be placed within a mounting board or mother board 12 having an aperture 14 therein. The mother board is constructed from an insulating material and provides the mounting member for the solderless electrical connector system of the present invention. Each aperture 14 within the insulating material of the mother board is coated with a suitable conductive material 16, as by electroplating or other process to form plated-through holes. The conductive material may also be formed in strips 18 upon the surface of the insulating mother board for electrically joining selected ones of the apertures 16.

In the preferred embodiment illustrated in FIGS. 1-5, the solderless electrical contact 10 is formed in three sections. That is, a non-round end section 20, a wedge locking central section 22, and an electrical component mounting end section 24. These sections are formed from a flat mill stock of spring material, for example, phosphor bronze, having two cross-sectional thicknesses. The non-round end section 20 is formed by stamping from the thicker cross-section having a thickness, for example, of .025 inches; while the central section 22 and mounting end section 24 are formed by stamping from a cross-section having a thickness of 0.007 inches, for example. From the stamped, mill stock thus described, the solderless electrical contact 10 is formed into the contact shown. Thus, the solderless electrical contact 10 is provided with a non-round end section 20 having a square cross-section, FIG. 5, about which wire conductors may be wrapped by suitable machinery. This arrangement eliminates the utilization of solder and provides adequate electrical connection between the electrical contact 10 and the wire conductors, not shown.

The central section 22 is formed just above the interface between the thick and thin portions of the mill stock. As seen in FIG. 4, the central section 22 is formed as an involuted C-shaped member having opposite ends of the C-shaped section turned inwardly and terminated at the approximate center line thereof to form leg elements 26. These leg elements 26 contact one another as the central section 22 of the contact 10 is inserted into the aperture 14. The closing of the C-shaped section causes each inwardly directed leg 26 to close against the inner surface of the central section in an even tighter loop. Thus, it will be seen that the initial insertion of the electrical contact 10 causes the central section 22 to close about the larger diameter of the cross-section until the leg elements 26 contact one another. At this time, the leg elements 26 become the yielding spring members and yield toward the inner surface of the central section 22. Detent 28 are formed within the central section 22 for locating the electrical contact 10 as it is inserted into the aperture 14. The detents are approximately equally spaced about the periphery of the central section 22 with the center detent opposite the opening of the C-shaped central section. A fourth detent 30 is utilized to retain the daughter board guide, as will be described hereinbelow.

The electrical component mounting end section 24 is formed as a generally flat portion of the mill stock with the lower end thereof or the end closest to the central section 22, curving into a semi-circular portion to join with the generally cylindrical shape of the involuted C-shaped central section 22. Extending upwardly and away from this semi-circular portion 32, the component mounting section is bent away from the longitudinal axis of the electrical contact 10 to form a spring contact section 34. The upper end of this spring section 34 is bifurcated by a slot 36 to form two electrical component contacting fingers 38. These fingers are bent back toward the longitudinal axis of the contact 10, at the point of component contact, and terminate in outwardly extending tab members 40. The purpose of the tab members will be described hereinbelow.

Referring now to FIG. 6 and 7, the solderless electrical contact 10 is shown within a solderless electrical connector system 42 wherein the mother board 12 is provided with plated-through apertures 14 whose conductive coating 16 overlap each end of the aperture and spread over the surface of the mother board for providing improved electrical contact. FIG. 6 illustrates a single conductive strip 18 upon the surface of the mother board 12. Obviously, other strips may be placed upon this board or multi-layer conductive strips may be placed upon the board and connected to selected plated-through holes. This arrangement allows interconnection between various solderless electrical contacts 10 within apertures 14 for eliminating excessive electrical wiring. Further, a properly designed multilayer conductor board 12 could eliminate the need for the nonround end sections 20 of the electrical contacts 10 altogether.

It will be seen in FIG. 6 that the electrical contacts 10 are arranged in parallel rows with the component contacting fingers 38 of opposite contacts 10 facing each other. Between these fingers 38, a daughter board 44 having conductive strips 46 thereon may be inserted. The fingers 38 wipe against the conductive strips 46 as the daughter board is forced between opposite electrical contacts 10. This forced motion causes the spring section 34 to yeild outwardly for generating holding forces which serve to hold the daughter board 44 in place and to establish electrical continuity with the conductive strips 46.

A daughter board guide member 48 is shown between the electrical contacts 10 and the daughter board 44. This guide is constructed from insulating material and fits over the two parallel rows of electrical contacts 10. The daughter board guide 48 is provided with a longitudinally extending slot 50 having shoulders 52 directed inwardly from opposite surfaces thereof and terminating in T-shaped ends 54. The upper surfaces of the T-shaped ends 54 are inwardly and downwardly sloped to provide an initial guide for the daughter board 44. As the board is inserted into the slot 50 it contacts the fingers 38 causing them to yield outwardly. The board is then urged downwardly until it contacts a stop 56 within the slot 50. The stop 56 is provided with relieved portions 58 having a lower shoulder 60 over which the detents 30 snap as the guide 48 is urged downwardly over the contacts 10. Thus, it will be seen that the contacts 10 are retained within the mother board 12 by the wedge locking central section 22 while the guide 48 is retained against the mother board 12 by the detents 30 and the shoulders 60 formed at the lower end of the relieved portions 58. Each contact 10 is located between the shoulders 52 with the tab members 40 between the T-shaped ends 54 and the inner wall of the slot 50. Thus, the tabs 40 prevent the fingers 38 from extending inwardly beyond a point established by the tab 40 and ends 54.

A second solderless electrical connection system 62 is shown in FIG. 8 wherein the solderless electrical contacts 10 are mounted within a plurality of apertures 14 which are provided with plated-through coatings 16. The non-round end sections 20 are illustrated as a square cross-section for wrapping wire thereabout without soldering. The wedge locking central sections 22 and the electrical component mounting end sections 24 have been modified. In this embodiment, each central section 22 has been forshortened while the electrical component mounting end section 24 is expanded from the rolled, involuted C-shaped cylinder of the central section 22 into a box-shaped section 63 for forming the end section. Sidewalls of the box-shaped section 63 adjacent the sidewall formed by the butting end portions of the mill stock are punched with a generally U-shaped cut to provide opposite, inwardly extending contact fingers 64. The box-shaped end sections 63 thus formed are arranged in two parallel rows for receiving a plurality of contact pins 66 of an integrated circuit package 68. It will be seen that this IC package includes fourteen contact pins 66 which are inserted into fourteen associated component mounting end sections 63 and retained by the holding force of 14 pairs of oppositely arranged contact fingers 64. This force is sufficient to provide mechanical mounting and establishes electrical continuity between the solderless electrical contact 10 and the contact pins 66.

The solderless electrical contact 10 has been described hereinabove as having a component mounting end section 24 with either contact fingers 38 or contact fingers 64 within a box-shaped section 63. It will be obvious that other terminations and arrangements are possible. For example, the solderless electrical contacts 10 could be provided with rounded end portions 69 for providing solderless electrical contacts that are mounted into the mother board 12 and form a plurality of pins within a male connector plug. This plug may then receive a typical female connector plug having pin receiving sockets therein. Further, the box-shaped component mounting contacts 10 be used to mount individual electrical components onto the mother board, such as a resistor 70.

Referring now to FIG. 9, a further cross-sectional embodiment of the wedge locking central section 22 is shown. The cross-section is formed as a simple C-shaped cross-section and provides adequate electrical continuity between the solderless electrical contact 10 and the conductive material 16 within the aperture 14. However, the mechanical holding force generated by this cross-section is not as great as the force generated by the involuted C-shaped cross-section shown in FIG. 4. The simple C-shaped cross-section of FIG. 9 may be utilized within a buss bar, for example, where a series of solderless electrical contacts are mounted within a common bar and inserted into a plurality of holes. In this arrangement, the holding force of each solderless electrical contact adds to the force of the others for providing adequate mechanical mounting of the buss bar.

Another embodiment of the wedge locking central section 22 is illustrated in FIG. 10. This cross-section is provided in the form of a pair of C-shaped cross-sections 71 placed one beside the other with the adjacent leg of one joining the adjacent leg of the other. The cross-section illustrated in FIG. 10 along with those illustrated in FIGS. 4 and 9 all provide a tight frictional contact against the inner surface of the conductive material coated over the aperture 14 for more than 180.degree. and in the case of the cross-sections shown in FIGS. 4 and 9 over more than 270.degree.. These configurations prevent the ambient atmospheric from reaching the conductive material and thereby prevent corrosion therebetween.

FIG. 11 illustrates another cross-section of the central section 22 in the form of a V-shaped cross-section having a rounded bottom portion and involuted upper ends. This configuration provides three-point contact with the inner surface of the aperture 14. FIG. 12 shows a further modification wherein a four-leaf clover configuration is shown. Each of the cross-sections shown in FIGS. 11 and 12 yield inwardly toward the longitudinal axis of the contact as the contact is inserted into the aperture 14. These embodiments provide a central section 22 which does not destroy the aperture into which it is mounted.

FIGS. 13 and 14 illustrate a second approach that provides a wedge locking central section for generating holding forces without destroying the aperture. These sections are formed by splitting a relatively thick central section 22 along its longitudinal axis for a limited distance. In FIG. 13, the split cross-section is expanded or bowed to form opposite spring legs 72 which engage the aperture 14 as the contact is inserted therein and yield toward each other. FIG. 14 illustrates a split section wherein legs 74, formed on opposite sides of the split, are vertically offset from each other. The opposing faces of each leg 74 formed by the split are then passed beyond one another such that the two legs 74 contact each other along the inner surfaces 76 thereof. As the contact is inserted into the aperture 14, the two legs 74 yeild inwardly with their inner surfaces 76 frictionally engaging one another.

In the present invention, a typical mother board may vary in size, for example, two sizes presently used include 48 by 24 inches and 19 by 15 1/2 inches. These boards are designed to receive and interconnect the circuitry of several smaller print circuit boards or daughter boards. The present invention enables the assembly, disassembly and reassembly of all components without creating the need for soldering, spot welding, or other forms of electrical connection. Through this arrangement, quick and economical field servicing is achieved. Further, the arrangement allows the assembly process to be simplified through a reduction of the number of pre-assembly and assembly chicks required. Since it is relatively simple to replace a single component, these components may be tested as assembled or assembled and then tested.

A typical mother board is often coated with conductive material by electroplating. These boards may then be reflowed. That is, the board after electroplating is placed in hot oil and the solder is allowed to flow for smoothing and improving the overall appearance and function of the board. During this process, the solder tends to migrate toward the holes and concentrate therein. The solderless electrical contact shown in FIGS, 4, 9 and 10 are especially suited for insertion into a aperture 14 in which solder has been concentrated. As the contact 10 is inserted, it wipes the hole 14 for cleaning out the excessive solder. During insertion, the central section 22 of the contact 10 yields and closes toward the longitudinal axis thereof. The yielding of the spring material forming the contact generates holding forces therein which retain the contact within the aperture without distorting and thereby destroying the aperture. The arrangement of the central section 22 illustrated in FIGS. 4, 9 and 10 further allows the outer walls of the central section to nearly completely contact the inner surfaces of the apertures 14. This large percentage of diameter contact creates a gas seal which prevents the ambient atmosphere from entering between the contact 10 and the aperture 14, thus preventing corrosion therebetween.

A substantial time and cost savings has been realized when the present invention is utilized as an electrical connection system. For example, a printed circuit board or mother board may be fabricated today with multi-layer conductors. However, these fabricated boards will not withstand the heat generated under normal soldering procedures as the heat destroys the multi-layer conductors. Thus, the solderless electrical contact of the present invention must be utilized within this type of system. Further, the system approach of the present invention allows a circuit designer and manufacturer to design and fabricate a circuit or system of circuits that eliminates connectors normally required. That is, the guide 48 is provided only for the purpose of guiding the daughter board. It is not necessary to purchase a plurality of connectors, mount the connectors to a mother board, and then mount daughter boards in each connector, as in the prior art. Here, the system designer may design his system for what is required. He may then insert the number of contacts he needs in the position required. Obviously a predetermined number of contacts will be required to mount each daughter board. However, beyond this number the contacts may be omitted as the connectors are not preassembled. This arrangement results ultimately in a time and cost saving to the system designer.

If a contact, guide, daughter board, electrical component, or other portion of the system needs to be replaced, the change may be accomplished by simply removing the daughter board 44 from between the solderless electrical contacts 10, pulling the guide 48 off the contacts 10 and pulling each contact 10 from its aperture 14. As the apertures are not destroyed by the insertion or removal of the contact 10, the process may be reversed for replacing any of the parts or components previously removed. The non-round end sections 20 of the contacts 10 may be eliminated in some systems where a multi-layer conductor board is utilized.

The preferred embodiment of the solderless electrical contact 10 has been described and several alternate cross-sections of the central section 22 have been set out. However, it will be obvious that other combinations or substitutions are possible. Further, the system in which the electrical contact is embodied may be altered or varied utilizing combinations of the devices disclosed herein without departing from the scope of the present invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

Claims

We claim:

1. A solderless electrical connection system, comprising:

an insulated mounting member having a plurality of apertures therein;

electrical conductive material coated upon the inner surface of said plurality of apertures and in strips upon said mounting member joining selected ones of said coated apertures;

conductive contact means having a central section passing through said coated apertures;

said central section formed from a flat cross-section rolled into a generally cylindrical shape friction engaging said coated apertures for electrically connecting said contact means to said conductive material and for mechanically mounting said contact means in said insulated mounting member;

said central section having extended detent means positioned beyond said insulated mounting member when said conductive contact means are mounted in said coated apertures; and

guide member means having a shouldered recess wherein said recess receives said conductive contact means for positioning said detent means over said shoulder of said recess to removably mount said guide member upon said insulated mounting member.

2. A solderless electrical contact system, comprising:

insulated mounting means having a plurality of apertures therein;

electrical conductive means coated upon the inner surface of said plurality of apertures;

conductive contact means formed about a longitudinal axis having central sections for engaging said coated apertures;

said conductive contact means having end sections at least one of which includes means for making electrical contact;

said central sections of said contact means including first and second deforming means;

said first deforming means of said central sections include oppositing portions each having a semi-circular cross section connected at one end; and

said second deforming means include rolled portions at the other unconnected end of each semi-circular portion, said semi-circular portions yielding and contacting each other at said unconnected ends as said contact means are inserted into said apertures, and said rolled portions at said unconnected ends yielding after contact of said unconnected ends as said contact means are further inserted into said apertures.

3. A solderless electrical connector system, comprising:

an insulated mounting member having a plurality of apertures therein;

electrically conductive material coated upon the inner surface of said plurality of apertures and in strips upon said mounting member joining selected ones of said coated apertures;

conductive contact means each having a longitudinal axis and a central section disposed within said coated apertures;

said central sections of said conductive contact means each including a cylindrical member having a generally C-shaped cross-section, end portions of said C-shaped cross-section directed inwardly for forming opposite rolled end portions, said central sections yielding to allow said rolled end portions to contact each other as said contact means are initially inserted into said apertures and said rolled end portions yielding as said contact means are fully inserted into said apertures;

electrical components including electrical conductive members; and

said conductive contact means each having end sections including wiping means for contacting said conductive members of said electrical components and thereby supportably mounting said electrical components.

4. A solderless electrical connector system as claimed in claim 3, wherein:

said electrical components include printed circuit boards having a plurality of electrically conductive strips thereon terminating at an edge thereof;

said end sections of said conductive contact means include wiping finger means contacting opposite sides of said edge of said printed circuit board at said electrically conductive strips for mechanically mounting said board while providing electric continuity to said conductive strips.

5. A solderless electrical connector system as claimed in claim 3, wherein:

said electrical components include packages having a plurality of electrically conductive pins extending therefrom;

said end sections of said conductive contact means include box-shaped portions having wiping finger means extending inwardly from opposite sides of said box-shaped portions for mechanically engaging said electrically conductive pins and providing electrical continuity thereto.

6. A device for making electrical contact between a plurality of electrical conducting means, comprising:

insulated mounting means having apertures therein;

a first group of said plurality of electrical conducting means including conductive material coated upon the inner surfaces of said apertures and in strips upon said mounting means joining selected ones of said coated apertures;

contact means each including first and second end sections and a central section which engages said apertures;

said first end section having a non-round cross-section about which a second group of said plurality of electrical conductive means may be wrapped;

said second end section having a flattened cross-section for wiping a third group of said electrical conducting means; and

said central section having a flat cross-section rolled into a generally cylindrically C-shape for friction engaging the coated inner surfaces of said aperture through which it passes, the ends of said C-shaped cross-section being rolled into second generally C-shaped portions for mechanically securing each of said contact means within said aperture and forming an electrical contact between said groups of said plurality of electrical conductive means.