CA2002166A1 - Zero insertion force electrical connector - Google Patents

Abstract

ZERO INSERTION FORCE ELECTRICAL CONNECTOR A zero insertion force electrical connector for electrically connecting two electrical members. A plurality of first electrical contacts on a first member engage a plurality of second electrical on a second member. An isostatic medium is retained against the second member and a pressure generator acts on the isostatic medium for providing a uniform force forcing the first and second contacts into engagement. One of the first and second contacts may be positioned in recesses and the other of the first and second contacts are outwardly extending for providing self alignment between the first and second members. The second member may be a three-layer tape having a first metal signal layer, a middle dielectric layer and a second ground layer for interconnection to a third electrical member.

Description

ZERO ,IN~E~TION FOR~ EI~c~NEc~oR
Ba~kground Qf thç Inv~atio~
The present invention is directed to a zero insertion for~e electrical connector for electrically connecting first an~ second electrical members, each of which includes first and second electrical contacts, respectively, wh;ch are placed in engagement. An isostatic medium is positioned against one of the members and is retained there by r~taining means an~ a pressure generating means acts on the isostatic medium for providing a uniform force forcing the irst and second electrical contacts into engagement. This advantageously provides a normal force at all contact locations for making a good contact independent of warpage or non-parallelism between the mating contacts. The present invention is particularly useful for connecting a three layer tape having a irst metal signal layer, a middle dielectric layer, and a third ground plane layer into a rematable connection with another electrical member. The tape ~s particularly useful for connection to a third electrical member, called a minisubstrate, ha~ing various electrical components for electrical connection to the first alectrical member.
Self-alignment between the first and seoond members may be readily ! obtained by raised aontacts on one of the members which seat within corresponding rece~ses containing contacts on th~ other member.

Summary The present invention is directed to a zQro insertion force electrical connector for electrically connecting two electrical members . A firs t member is provided having a plurality of fir~t electrical contacts and a second member ~s 3 6~

positioned against the first member and includes a plurality of second electrical contacts on the first side for being placed in engagement with the first contacts. An isostatic medium is positioned against the second side of the second member and S retaining means are provided for holding the isostatic medium in engagement against the second side of the second member.
Pressure generating means acts on the i~ostatic medium for providing a uniform force forcing the first and second contacts into engagemen~.
Still a further object of the present invention is wherein one of the first and second contacts are positioned in recesses and the other o the first and second contacts are outwardly estending for providing self-alignment between thP
first and second members.
Yet a still further object of the present invention is wherein the second member is a three layer tape having a first metal signal layer, a middle dielectric layer, and a second ground layer.
Yet a still further object of the pre~ent invention is wherein the isostatic medium is a bladder containing a substantially incompressible fluid.
Yet a still further object is the provision of a third electrical member positioned adjacent the side of the isostatic medium remote from the second member and the third member ` 25 includes a plurality of third electrical contacts electrically connected to the second contacts.
Still a further object of the present invention is wherein the retaining means includes a retainer surrounding the sides of the isostatic medium, a support plate engaging the top of the isostatic medium and supporting the third electrical :

member, and a lid secured to the first member and engaging the support pla~eO
Other and further objects, features and advantaqes will be apparent from the following description of presently preferred embodiments of the invention, given for the purpose of disclosure, and taken in conjunction with the accompanying drawings.

Brief Description Q~-~hQL~s~-w nqs Fig. 1 is a fragmentary elevational view of the bottom side of one of the electrical members to be connected, Fig. 2 is a fragmentary eievational view of the top side of the member of Fig. 1, Fig. 3 is an enlarged fragmentary cross-sectional view of the member of Figs. 1 and 2, Fig. 4 is an exploded plan view of the connector of the present invention, Fig. 5 is an elevational plan view of a portion of the assembly of the connector of Fig. 4 with the hinge lia removed, Fig. 6 is a cross-sectional view taken along the line 6-6 of Fig. 5 showing the lid, attached and raised, with attachment screws ready to be inserted, Fig. 7 is a cross-sectional view similar to Fig. 6 with the lid in a downward position and locked, 2S Fig. 8 is an elevational plan view of the apparatus of Fig. 7, Fig. 9 is a cross-sectional view taken along the line 9-9 of Fig. 8, Fig. 10 is a cross-sectional view taken along ~he llne ~O 10-10 of Fig. 8, Fig. 11 is an enlarged detailed view of the detail 11 of FigO 10, Fig. 12 is an elevational view of a portion of the connector in its activated position, Fig. 13 is a fra~mentary elevational view o the bottom of another embodiment of an electical member to be connected, Fig. 14 is a fragm2ntary elevational view o the top of the member of Fig, 13, Fiq. 15 is an enlarged fragmentary cross~sectional view of the member of Yigs. 13 and 14, and Fig. 16 is an enlarged fragmentary cross-sectional view of the use of the members 13, 14 and 15 in an electrical connection, Description of the Prefer~ed Embodim~nt While the present invention will be described in connection with providing a key zero insertion force connection between a three layer tape to a printed circuit board, such as a microwave substrate, in which a uniform contact force betwqen contacts on the tape and the substrate is provided by an isostatic medium for purpose of illustration, it is to be , understood that the present zero insertion force electrical connector may be used ~or electrically connecting various types of electrical members.
Referring now to the drawing~, the zero insertion force electrical connector 10 (Figs. 4, 5, 6, 7, 8, 9 and 10 is particularly useful in interconnecting a first electrical member 12 ~Fig. 11) such as a microwave substrate or printed circuit board having a plurality of electrical contacts, such 6 ~

as signal contacts 14 and ground contacts 16, to a second electrical tape member generally indicated by the re~erence numeral 20 having a plurality of signal contacts 22 and ground contacts 24 in which the contacts 14 and 16 may be engaged by the contacts 22 and 24, respectively, with a zeso force.
Thereafter the contacts are loaded to a proper uniform normal force by means of an isostatic medium generally indicated by the reference numeral 30. The printed circuit board 12 may be any suitable material with useful high per~ormance ~lectrical as well as mechanical properties such as multilayer microwa~e substrate structures of Teflon-fiberglas mat-copper, mult~ple layer polyimide-copper constructions, and micro-coaxial additive wire boards. The second electrical member 20 may also be adapted to be electrically connected to a third electrical member such as a minisubstrate 26, which could be of glass or ceramic construction for e~am~le, haYing electrical contacts 27 and 28.
Referring now to Figs. 1, 2 and 3, the structure of the second electr;cal tape member 20 is best seen which is preferably a three layer tape ha~ing a first metal signal layer 32, a middle dielectric layer 34 and a third ground layer 36.
Preerably, the layers 32, 34 and 36 are a copper signal layer, polyimide, and a copper ground plane~ respectlYely, alShough other materials may be used. The first layer 32 consist~ of a plurality of microstrip conductor traces 38 each of whlch is connected to one of tha second contacts ~2 which, for e~ample only, are positioned on 30 mil centers or more on a ~quare grid. The second end of the traces 38 are connected to a row of electrical contacts 40, for e~ample, on 10 mil centers or less adjacent the outer edge of the tape connector 20, to ~orm electrical connectors for connecting t~ the contacts 27 on the substrate 26 (Fig. 11) by conventional surface mount techniques, such as soldering or by outer lead bonding, such as thermo sonic bonding~ For e~ample only, if the dielectric layer 34 is two mils in thickness, an estimat~ for the microstrip traces 38 width is 4 mil for a 50 ohm line.
` The ground plate 36 is connected to a plurality o~
ground contacts 24 and is connected to an outer rsw of ground contacts 42 for connection with the contacts 28 of the substrate 26 (Fig. 11) such as by conventional surface mount techniques.
Referring again ~o Fig. 11, it is to be noted that the first electrical connector 12 and th~ second electrical connector 20 achieve self-alignment by havinq raised or outwardly extending contacts in one of the members and corresponding recesses in the other. As shown, the contacts 22 and 24 on the tape member 20 are preferably outwardly extending or raised and coact with recesses in the first member 12 which can be obtained by profiling the surface of the member 12 or preferably, as shown, by providing a dielectric layer 44 having a plurality of windows 46 for receiving the contacts 22 and 24. Alternatively, contacts 14 and 16 could be raised and contacts 22 and 24 provided i~ recesses.
Referring now to Figs. 4, 5, 6, 7, 8 and 9, the connector 10 of the present invention includes a mounting member 50 which is secured to the ~ubstrate 12 such as by bolts 52 and nuts 5~ tFigs. 6 and 7). A retainer member 56 is supported in the mounting member 50 and supports the outer euyes or the isostatic medium 30. A supporting plate 5~ lS
positioned over the retainer 56 and supports the minisubstrate 26. In addition, a hinged lid 60 which is pivotally connected at pivot 62 to the mounting board 50 is provided and includes a releasable lock 66 for loc~ing to the mounting support 50.
Thus, the members 50, 56, 58 and 60 act as retainer mPans for holding the isostatic medium 30 in engagement with the second side of the tape electrical member 200 The isostatic medium 30 advantaqeously provides means for loading the engagement of the first contacts 14 and 16 of the first member 12 against t~e second contacts 22 and 24 of the second member 20 by uniform normal force.
The advantages of the isostatic pressure medium 30 ~Poisson No. substantially = 1/2) includes the ollowing:
1. The medium 30 eshibits isotropy. This means that the same normal force is established at all of the contact locations and as independent of warpage or nonparallèlism between the first member 12 and the second member 20;

2. An isostatic medium behaves as a Pascals Law fluid. By transmission of a uniform pressure throughout the medium such a medium can allow a small initiation force to result in the transmission of a much larger force at a distance according to the ratio of areas. As an isostatic pressure can be initiatad orthogonally to the direction of the normal contact forces of the coacting contacts, there need not be relative motion between the printed circuit board 12 member and .
the tape member 20 as contact is made;

3. The medium 30 can be temperature compensated by, for e~ample, the use of a Hook's law device attached to a piston to allow it to yield as the isostatic medium 30 e~pands as a function of temperature.

~ ~3~ ~6 ~

The isostatic medium 30 is of an incompressible (or slightly compressible~ liquid, gel, was, polymer, rubher or the like and may be retained between the retainer 56 and support plate 58 or within a bladder 31. For e2ampls, a fle~ible bladder containing water may be used. Another type of satisfactory medium would be an elastomer.
Any suitable means for applying a pressure generatin~
force on the isostatic medium 30 may be provided. For e~ample~
~he space in the retainer 56 may ~e such that merely locking th3 lid 60 which eserts a force on the ~upport plate S8 an~
~medium 30 would provide the necessary pressure generation.
However, as shown in the drawings, the retainer S6 includ~ a slot 70 in which a sliding el2ment or piston 72 is moYable for en~aging and compressing the isostatic medium 30. The piston 1~ 72 may be actuated by a cam 74 which moves from a retracted position as ~est seen in Figs. S, 6 and 7 to a past dead center position against pin 76 to pressure generating position, as best seen in Fig. 12, to engage the piston 72 and mov~ it a~ainst the medium 30 to compress the medium. Compression o~
medium 30 will transmit a uniorm isostatic pressure to all surfaces in contact with the medium 30 including the second electrical contacts 22 and 24. Other means of initlation of the isostatic pressure such as a shape memory metalO such as can be fabricated from nickel-titanium alloys, could also be used. The isostatic p~essure in the reqion of the tape member 20 adjacent to the printed circuit board 12, to w~ich contact is made, will insure that all of the contacts will achie~
nearly iden~ical normal forces within the limit o~ s~veral mil variations in planearity over the footprint o~ the medium 30.

~ ~, ~ 66 In use, the mounting support 50 is secured to the first electrical member or printea circuit board 12 and the second electrical member such as the tape member 20 is positioned with the second contacts 22 and 24 in engagement S with the first contacts 14 and 16, respectively, ~o provid~ a self-alîgnment between the members 12 and 20. Thus, the tape member 20, the isostatic medium 30, the retainer 56, support plate 58 and the third electrical member or mini~ubstrate 26 twith its contacts 27 and 28 bonded to the contacts 40 and 42 of the tape connector) are inserted in the mount 50.
Thereater the lid 60 is closed and the pressure generating means such as cam 74 i~ actuated to move the piston 72 into engagement wit~ the isostatic medium 30 for insuring a uniform force contact between the members 12 and 20.
Other and further embodiments may be provided. For example, as best seen in Figs. 13, 14, 15 and 16, a different second electrical connector may be provided wherein l~ke parts to those shown in Figs. 1-3 are similarly numbered with the addition of the suffi~ "a~. In this embodiment, t~e tape connector 20a is again a three layer tape in wh ch the ground layer 36a is on the top and the third layer 32a, which cons~sts of the signal traces 38a, is on the bottom. Again, th~
rematable contacts 22a and 24a of the connector 20a coact wi~h the contacts 14a and 16a, respectively, of the connector 12a and are loaded into contact with each other by the isostatic medium 30a. The contacts 40a and 42a of the connector 20a may be bonded to the contacts 27a and 28a, respectiv01y, on the minisubstrate 26a by conventional outer lead bonding.
The present invention, therefore~ is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While presently preferred emhodiments of the invention have been given for the purpose of disclosure, numerous changes in the detail~ of construction and arrangement of parts will be xeadily apparent to those skilled in the ar~ and which are encompassed within the spiri~ Qf the invention and the scope of the appended claims.

.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A zero insertion force electrical connector comprising, a first electrical substrate having a plurality of first electrical contacts recessed in windows, a flexible three layer tape having a first metal signal layer, a middle dielectric layer, and a third ground layer, said tape including a plurality of second electrical contacts extending outwardly from a first side for engaging said first electrical contacts, each of said second contacts connected to one of the first and third layers, and electrical connections at the outer edges of said tape connected to the first metal signal layer and to the third qround layer, an isostatic medium positioned against the second side of the tape, retaining means holding the isostatic medium in engagement against the second side of the tape, pressure generating means acting on the isostatic medium for providing a uniform force forcing the first and second contacts in engagement, and a second electrical substrate electrically connected to the electrical connections on the tape.

2. The apparatus of claim 1 wherein the retaining means includes, a retainer surrounding the sides of the isostatic medium, a support plate engaging the top of the isostatic medium and supporting the second electrical substrate, and a lid secured to the first substrate and engaging the support plate.

3. The apparatus of claim 1 wherein the electricac connections at the outer edges of the tape are bonded to the outer edges of the second electrical substrate.