US 3848952 A
A zero insertion force electrical connector is disclosed for use in making edge connections with printed circuit boards and the like. The subject connector includes a plurality of connector spring contacts mounted in an associated housing. The housing and a printed circuit board support are fixedly mounted on a base or chassis in spaced relationship. The spring contacts are so arranged as to have a vertical and horizontal cantilever spring components thus providing for contact adjustment in both the X and Y directions while providing a high contact force.
Description (OCR text may contain errors)
United States Patent [191 Tighe, Jr.
[451 Nov. 19, 1974 ZERO INSERTION FORCE EDGE CARD CONNECTOR  Inventor: Charles I. Tighe, Jr., Camp Hill, Pa.  Assignee: AMP Incorporated, Harrisburg, Pa.  Filed: July 27, 1973  Appl No.: 383,365
 US. Cl...... 339/91 R, 339/125 R, 339/176 MP  Int. Cl l-I0lr 13/54  Field of Search 339/64-66,
 1 References Cited UNITED STATES PATENTS 2,935,725 5/1960 Fox 339/176 MP 3,193,791 7/1965 Bock et al 339/176 MP 3,366,919 1/1968 Gammel, Sr. et a1. 339/176 MF 3,533,045 10/1970 Henschen 339/176 MP 3,567,998 3/1971 Ammerman 339/176 MP Bouley 339/176 MP FOREIGN PATENTS OR APPLICATIONS 1,576,555 8/1969 France 339/91 R 1,129,580 5/1962 Germany 339/258 R 1,392,205 2/1965 France 339/176 MP Primary Examiner-Joseph l-I. McGlynn [5 7] ABSTRACT A zero insertion force electrical connector is disclosed for use in making edge connections with printed circuit boards and the like. The subject connector includes a plurality of connector spring contacts mounted in an associated housing. The housing and a printed circuit board support are fixedly mounted on a base or chassis in spaced relationship. The spring contacts are so arranged as to have a vertical and horizontal cantilever spring components thus providing for contact adjustment in both the X and Y directions while providing a high contact force.
13 Claims, 6 Drawing Figures PATENTEL HEW l 9 I974 SHEEI 1 BF 3 PATENTEL, 213V I 9 I974 SHEET 3 BF 3 ZERO INSERTION FORCE EDGE CARD CONNECTOR BACKGROUND OF THE INVENTION I. The Field of the Invention The present invention relates to a zero insertion force electrical connector for making edge connection with printed circuit boards and the like and, in particular, to an electrical connector which may be used with either horizontally or vertically disposed printed circuit boards.
2. Description of the Prior Art It is important for any edge board electrical connector to have the capability of making good electrical contact over a relatively large range of tolerances. For example, the connector must be able to accept printed circuit boards which are either warped or have edge pads which vary in thickness. It is also desirable to have such a connector arranged to accept printed circuit boards with a zero insertion force in order to have low wear of both the contacts and the pads.
Many attempts have been made to provide an electrical connector having the above properties. For example, US. Pat. No. 3,366,919 discloses an electrical connector which requires a low insertion force. The disclosed connector is arranged to accept the male plug of a multi-conductor cable at an angle with respect to the longitudinal axis of the receptacle body. The conductor members of the cable are initially positioned between the parallel arms of the receptacle contacts, with low insertion force, and then rotated into alignment with the axis of the receptacle body after the contact engage. While this arrangement may prove suitable in some cases, this connector has a relatively low toler-. ance range defined by the amount of resiliency of only one of the two parallel arms.
US. Pat. No. 3,732,531 shows an electrical contact which is movable in order to provide proper contact with a mating connector. This connector is intended for use in making contact with printed circuit boards and has U-shaped arms joined to a base by a resilient beam. The arrangement is a modification of a cantilever beam contact and has only limited tolerance for reception of contact cards which are warped or have pads of varying degrees of thickness.
SUMMARY OF THE INVENTION for fixation in the housing, and an electrical interface terminal projecting from the support section. Each housing includes a fulcrum, stop and registration guide for the printed circuit board, a plurality of contact cavities and guides, and connector mounting brackets extending from a structural frame. Each printed circuit board support is formed from a resilient material and includes a support mounting groove, a board mounting groove, a stand-off section, and a pull tab.
It is an object of the present invention to construct an electrical connector for making electrical contact with an edge portion of a printed circuit board or the like which connector will require substantially zero insertion force and provide a high contact force.
It is also an object of the present invention to construct a zero insertion force electrical connector which will have a wide range of tolerance for accepting printed circuit boards and the like which are warped and/or have edge contact pads of varying degrees of thickness. 7
It is a further object of the present invention to construct a zero insertion force electrical connector having a plurality of spring contacts with resiliency in two dimensions thus allowing for making good electrical contact with printed circuit boards having edge pads falling within a wide range of tolerances.
It is yet another object of the present invention to construct a zero insertion force electrical connector which may be used with either horizontally or vertically disposed printed circuit boards and the like.
It is still another object of the present invention to construct a zero insertion force electrical connector which may be readily and economically produced.
The foregoing and other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description taken with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, partially in section, showing a first embodiment of the spring contact for subject zero insertion force electrical connector;
FIG. 2 is a vertical section through the subject zero insertion force electrical connector showing a second embodiment of the spring contact,which embodiment is suitable for use with horizontally disposed printed circuit boards;
FIG. 3 is a vertical section through the subject zero insertion force electrical connector showing a third embodiment of the spring contact, which embodiment suitable for use with vertically disposed printed circuit boards;
FIG. 4 is a schematic representation of a section through a warped printed circuit board showing the ability of the subject connector for making good connections over a wide range of tolerance;
FIG. 5 is a perspective view of an end portion of the housing for the subject zero insertion force electrical connector; and
FIG. 6 is a vertical section through the housing of the subject zero insertion force electrical connector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The subject zero insertion force connector system shown in FIG. 1 includes a housing 10 attached to a support base or chassis 12 and enclosing therein a plurality of first embodiment connector spring contacts 14. A printed circuit board support member 16 is fixedly mounted on the base 12 spaced from the housing 10. A printed circuit board or card 18 is shown mounted in the connector and on the support member 16. Each first embodiment spring contact 14 includes a yoke portion 20 having an electrical contact 22 which is substantially parallel to and spaced from a follower contact 24. The yoke portion 20 is supported by a vertical cantilever spring 26 and a horizontal cantilever spring 28 which extend serially from a contact support section 30. The contact support section 30 has at least one retaining barb 32 projecting therefrom for securing the spring contact in the housing 10. A first electrical interface terminal 34 depends downwardly from the support section 30 while a second terminal 36 projects through a rear wall of the housing 10.
The printed circuit board support member 16 is formed from a unitary piece of resilient material and includes a support mounting groove 38, a board mounting groove 40 a stand-off section 42 and a pull tab 44. Each printed circuit board or card 18 to be mounted in the connector is provided with an opening 46 spaced from the contact edge and adapted to receive the support member therein.
The housing 10, as best seen in FIGS. and 6, in-
cludes a support frame 48 having a printed circuit board fulcrum portion 50 spaced above and to the rear of a printed circuit board stop portion 52 defining an elongated access opening 54 therebetween. A plurality of spring contact guide surfaces 56 and terminal openings 58 are formed in the housing in parallel spaced relation. A printed circuit board registration guide panel 60 is formed at each end of slot 54. The housing is also provided with connector mounting means 62.
The second embodiment of spring contact for the subject connector is shown in FIG. 2 and is used with horizontally disposed printed circuit boards. The same reference numerals have been used to identify like parts of each of the connector. spring contact embodiments. This embodiment includes a yoke 20, an electrical contact point 22, a follower contact 24, a vertical cantilever spring 26, a horizontal cantilever spring 28, contact support section 30, a retaining barb 32 and an electrical interface terminal 34. The printed circuit board 18 is shown in phantom at the angle of approach necessary for effecting a zero forceentry.
The third embodiment of spring contact for the subject connector is shown in FIG. 3 and is used with vertically disposed printed circuit boards. This embodiment also includes a yoke 20, an electrical contact point 22, a follower contact point 24, a vertical cantilever spring 26, a horizontal cantilever spring 28, a contact support 30, a barb 32 and an electrical interface terminal 34.
The components of the subject connector are assembled by inserting the terminal and support portions 34 and 30, respectively, of each spring contact 14 into the associated terminal opening 58 of the housing 10 until the barb 32 engages in the housing. The assembled connector is secured to an appropriate supportbase 12, for example by snapping mounting feet 62 into holes in the support base or by soldering the interface terminals to a parent printed circuit board. The printed circuit board supports 16 are assembled on the support base 12 and the connecting system is ready to receive a printed circuit board or card 18. The edge of the printed circuit board carrying the contact pads is inserted into the connector at such an angle as to clear both contact points of the spring contacts 14 and the housing portions 50 and 52 to effect a zero force entry. Then the printed circuit board 18 is rotated about fulcrum 50 until the opposite end of the board engages and is secured by the support member l6.
The contact support section 30 of each connector spring contact 14 serves to retain the contact in the housing 10 and also serves to mechanically isolate the yoke portion 20 from the interface terminal 34. The horizontal cantilever spring 28 supplies part of the contact force and imparts vertical motion to the yoke when deflected. The vertical cantilever spring 26 supplies the remaining portion of the contact force and imparts horizontal motion to the yoke when deflected. Both springs also serve to support the yoke 20 and each other. The yoke 20 includes the follower contact 24 and the electrical contact 22 which provides both mechanical and electrical interfacing with the printed circuit board 18. Since the yoke 20 is a rigid member compared to the spring portions 26, 28 of the contact, the yoke experiences little or no deflection when a force is applied to the electrical contact point but rather transforms the force into components of vertical and horizontal deflection of the cantilever springs. Therefore, due to this design characteristic, it is possible to move the yoke 20 in either the X or Y direction, a resultant direction of X and Y, and even a rotational motion all but limited to one plane. This motion allows the yoke to assume any position in a region in the plane of motion and the vertical distance between the contact points can vary within this region. Furthermore, as a result of these motions, relative to'displacement of the electrical contact 22 to the printed circuit board pad occurs to effect contact wiping.
The electrical contact 22 and follower contact 24 are displaced from each other both vertically and horizontally. This displacement controls the maximum thickness printed circuit board the yoke will accept without deflection, while the vertical displacement alone controls the minimum thickness of printed circuit board that will take up all of the contact pre-travel. By proper selection of the sizes for vertical and horizontal displacement, the printed circuit board thickness limit can be accomodated, while the yoke will not experience any dimensional change. Additional functions of the yoke will be discussed later with the housing as an assembled connector. The only design limitation on the electrical interface terminal is dependent upon the type of termination specified, i.e., wire wrap, solder inprinted circuit boards, soldered wire, etc.
The function of the housing portions are evident from their nomenclature and need little explanation.
The printed circuit board fulcrum provides one of the reaction forces opposing the contact force and vertically positions the blade end of the printed circuit board assembly relative to the connector mounting plane. When a contact is assembled into a housing, the yoke follower contact is positioned with respect to the fulcrum so as to establish the contact pre-load. When a printed circuit board is inserted and rotated into full contact location, the follower contact will be moved down and coincide with the fulcrum. Any further rotation or downward motion of the printed circuit board will rotate the yoke. thereby increasing the contact pressure.
In the case of a printed circuit board which is warped between contact pads, see F IG. 4, since the yokes capture the board blade upon insertion and each yoke operates independently, the yokes must remain in proper contact with the board by departing from their normal contact position through deflection of the horizontal and vertical cantilever springs.
The subject connector is not limited to interfacing with a printed circuit board or card. A plug with a mating contacts may be used in place of the board and then permanent interface may be made to the printed circuit board or other devices. The present system uses motion of the printed circuit board to develop the contact pressure while the housing in contacts remain fixed. In other design situations motion of the housing or contacts or both could be used for this purpose. The contacts alone can be inserted into a mount surface to make an interface.
FIG. 4 shows a transverse section of a warped printed circuit board to schematically illustrate how the yoke portions of the contact springs may be displaced from their normal positioning and still make full or proper contact with the pads of the printed circuit board. It should also be noted that the pads are shown with at least one pad having a greater thickness and yet still making proper contact with the electrical contact'portion of the yoke.
It should be noted that the pivotal movement of the printed circuit board from the initial entry position to the final fixed position will cause a certain amount of wipe by the electrical contact point against the pad on the printed circuit board. Thus the subject connector will provide a good electrical contact between the board and the connector system.
The spring contacts can be blanked from any desirable metal. The blanked contacts will normally have a somewhat roughened surface and a chisel shape, in transverse section, which will aid with the above mentioned wiping to produce a good electrical interface between the contact and the printed circuit board pad.
The subject connector has many advantages including the fact that there is zero insertion force of the printed circuit board. The connector can accept a wide range of printed circuit board thicknesses. Each contact yoke has an additional vertical float in its cavity which compensates for irregularities in printed circuit board contact pad levels caused by such things as board warp. Since eack yoke is independent so that it can follow the contours of the board while containing proper contact pressure. As much as 0.015 level difference between adjacent contact pads can be compensated for. This feature further eliminates intermittent contact due to mechanical vibration and shock since the yoke is captured by the printed circuit board and must follow the motion of the board. As each contact is actuated, the rotational motion of the contact yoke causes a wiping action.
The printed circuit support member is made of a resilient material, such as neoprene rubber, and provides for vibration and shock insulation as well as holding the board in a relatively fixed position. The location of the support member is not critical and the number and positioning of these members may vary according to size and weight considerations.
It is to be understood that the present connector may be subjected tomany changes and modifications without departing from the spirit or essential characteristics of the present invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive.
What is claimed is:
1. An electrical connector for receiving and contacting a mating electrical connector upon application of substantially no insertion force, comprising:
a housing having a fulcrum portion and a stop portion in parallel spaced relation defining an access opening therebetween; and
plurality of connector spring contacts fixedly mounted in said housing, each said contact including a yoke portion having two interconnected parallel arms with an electrical contact on one of said arms and a follower contact on the other of said arms, a horizontal cantilever spring and a vertical cantilever spring connected in series, a contact support portion connected to one end of said spring series and said yoke connected to the other end of said spring series, and a terminal portion connected to said contact support, said support portion being fixedly mounted in said housing with said terminal portion extending from said housing and said yoke aligned with said access opening, whereby said mating connector is inserted into said access opening without engaging said spring contacts and is rotated about said fulcrum portion to abut said stop portion and engage said spring contacts.
2. An electrical connector according to claim 1 wherein said housing is formed from an electrical insulation material.
3. An electrical connector according to'claim 1 wherein said housing further comprises registration means at least at one end of said access opening adapted to align said mating connector.
4. The electrical connector according to claim 1 wherein said horizontal cantilever spring is connected to said support portion and said yoke portion is connected to said vertical cantilever spring and positioned to open vertically to receive vertically disposed mating connectors.
5. The electrical connector according to claim 1 wherein said vertical cantilever spring is connected to said support portion and said yoke portion is connected to said horizontal cantilever spring and positioned to open horizontally to receive horizontally disposed mating connectors.
6. The electrical connector according to claim 1 wherein said mating connector is a printed circuit board, said electrical contacts on each of said spring contacts engaging with edge contact pads of said board.
7. The electrical connector assembly according to claim 1 wherein said mating connector is a male plug.
8. An electrical connector according to claim 1 wherein said housing further comprises mounting means for attaching said housing to a support base.
9. An electrical connector according to claim 4 wherein said mounting means comprises resilient feet adapted to snap fit within openings in said support base.
10. An electrical connector according to claim 8 wherein said mounting means comprises outwardly diterial and includes a support base mounting groove, a mating connector mounting groove, a stand-off portion between said grooves and a pull tab whereby said support means is stretched to pass through an opening in said mating connector and released to hold said mating connector in a relatively fixed position with respect to said housing and said support base.
13. An electrical connector system requiring substantially zero insertion force for receiving and contacting mating electrical connector, such as a printed circuit board, comprising:
a support base;
a housing having a fulcrum portion and a stop portion in parallel spaced relation defining an access opening therebetween and registration means at least at one end of said opening, said housing fixedly mounted on said support base;
a plurality of connector spring contacts mounted in said housing, each said contact including a U- shaped yoke portion having an electrical contact support means mounted on said support base spaced from said housing and adapted to releasably engage said mating electrical connector, whereby a contact bearing edge portion of said mating connector is inserted into said opening without engaging said contacts and subsequently pivoted about said fulcrum portion until engaging said contacts and abutting said stop portion and is secured in said last mentioned position by engagement with said support means.