Connector having staggered contact architecture for enhanced working range

An architecture for increasing the normalized working range of connectors having arrays of small contacts. One configuration includes a plurality of pairs of opposed contacts that are arranged in a staggered fashion. The opposed contacts are configured to engage an external contact array in a staggered fashion. The contact arm length of elastic contacts can be substantially greater than the effective array pitch of the plurality of pairs of opposed contacts. Accordingly, the vertical displacement range of three dimensional contacts formed in the connector can be much greater than for in-line contact arrangements.

BACKGROUND

1. Field of the Invention

This invention relates to electrical connectors, and in particular to components having arrays of elastic contacts.

2. Background of the Invention

As the need for device performance enhancement in electronic components drives packaging technology to shrink the spacing (or “pitch”) between electrical connections (also referred to as “leads”), a need exists to shrink the size of individual connector elements. In particular, packaging that involves advanced interconnect systems, such as interposers, can have large arrays of contacts, where individual electrical contacts in the array of contacts are designed to elastically engage individual electrical contacts located in a separate external device, such as a PCB board, IC chip, or other electrical component.

Although interposers, IC chips, PCB boards and other components are typically fabricated in a substantially planar configuration, often the contacts within a given component do not lie within a common plane. For example, an interposer with contacts arranged in substantially the same plane may be coupled to a PCB that has contacts at various locations on the PCB that have varying height (vertical) with respect to a horizontal plane of the PCB. In order to accommodate the height variation, the interposer contacts can be fabricated with elastic portions that are deformable in a vertical direction over a range of distances that accounts for the anticipated height variation.

As device size shrinks and the amount of components per unit area on electrical components increases, the pitch of contact arrays in interconnect systems such as interposers must be reduced. As used herein, the terms “pitch” or “array pitch” refer to the center-to-center distance of nearest neighbor contacts in an array of contacts, where the distance is typically measured in a direction within a horizontal plane of the contact array. Concomitant with reduction of array pitch is a reduction in average size of the contacts within the array (also termed “array contacts”). This results in a reduction in the dimensions of elastic portions of the contacts, which are typically configured as arms or beams that extend from a base contact in a three dimensional manner above a surface defined by the contact base. This reduction in contact arm length in turn leads to an undesirable reduction in the height variation through which the contact arm can be displaced, and therefore a reduction in height variation of an external component that can be accommodated by the interposer contact array.

DETAILED DESCRIPTION

FIG. 1ais a reference architecture used to describe the present invention and illustrates an array100of contacts101, each arranged within a contact cell102, according to an “in-line” architecture. Elastic contact arm104extends above a base106at an angle α, as shown inFIGS. 1band1c. Contacts101are arranged in an X-Y square grid indicated by dashed lines, where the region between adjacent X-gridlines and adjacent Y-gridlines defines a cell. The grid spacing W, that is, the distance between centers (C) of neighboring cells102, is also termed the array pitch. In this example the grid spacing along the X and Y directions, Wx and Wy, respectively, is represented as equal, but can in general differ. The arrangement, or “architecture,” of contacts101is a simple design layout in which each contact occupies the same relative position within its respective cell. In the reference arrangement shown in plan view inFIG. 1a, contact arms104of contacts in adjacent cells project their long axis in the X direction along a common line, which, for convenience, can be chosen at the cell center line CL. Each cell102thus has contacts101that are symmetrically positioned on both sides of CL. A slight variation on the arrangement ofFIG. 1ais shown inFIG. 1din which adjacent contacts101of array110are arranged along a common center line in the X-direction but are flipped in orientation.

In the reference contact arrangements depicted inFIGS. 1aand1d, when the array pitch W is reduced in size, for example, at least in the X direction, so that the separation of center points C in adjacent cells becomes smaller, the overall contact length L must be reduced. This entails a reduction in the length La of contact arms104. In other words, given the “in-line” arrangement of adjacent contacts, where successive contacts along the X-direction are centered on a common line, the contact arm length La must always be substantially smaller than W to allow space for a base portion of the contacts.

In the arrangement shown inFIGS. 1a-1d, for a given value of α that defines the angle between the elastic arm direction and the plane of base portion106, the top portion of elastic contact101is located at height H1above substrate108. H1represents the approximate distance over which an elastic contact arm104can be vertically displaced when it comes into contact with an external contact, such as a signal pin or pad, and is subsequently pushed until it comes to rest aligned with the plane of base portion106. In cases where an elastic contact arm extends over a hollow via, it would be possible in principle for the arm to be deformed below the plane of the base portion and into the via. But for the purposes of simplification, it will be assumed hereinafter, unless otherwise noted, that the maximum displacement distance for an elastic contact arm is defined by the plane of the contact base portion. Accordingly, when array pitch W is reduced, the concomitant decrease in contact arm length La entails a proportional decrease in this maximum vertical distance H1.

In an extreme case where contact array100is designed to contact an external component having contacts at an uneven height, if the height variation between contacts of the external component exceeds H1, this can result in electrical failure. In other words, a connector having contacts with a limited range of vertical displacement H1cannot electrically engage all the electrical contacts of an external component that lie at different heights, if the variation in heights of external contacts exceeds the ability of different contacts101to displace vertically to accommodate the variation. Thus, some contacts101will be prevented from coming into contact with an intended external connection. This could result in electrical failure of the system containing contact array100and the external component.

Short of electrical failure, the reduction in contact arm length La that occurs with reduced array pitch can lead to an undesirable reduction of working range for the electrical connector containing the array of contacts. As used herein, the term “working range” denotes a range over which a property or group of properties conforms to predetermined criteria. The working range is a range of distance (displacement) through which the deformable contact portion(s) can be mechanically displaced while meeting predetermined performance criteria including, without limitation, physical characteristics such as elasticity and spatial memory, and electrical characteristics such as resistance, impedance, inductance, capacitance and/or elastic behavior. Thus, for example, the vertical range of distance over which all contacts in a connector form low resistance electrical contact with an external component may be reduced to an unacceptable level. In the example ofFIG. 1b, H1would generally correspond to an upper limit of working range, assuming that a contact arm104that engages an external component at height H1is not free to travel below a plane of base106.

Thus, when reducing overall device pitch, a user employing a contact design like that depicted inFIGS. 1a-1dis presented with a tradeoff between the increased device and circuit densities achieved by scaling down contact pitch W, and the known advantages that adhere thereto, and a reduced ability to accommodate height variations between contact positions when coupling to contacts of external electrical components.

FIG. 2aillustrates an arrangement (or “architecture”) of a contact array200according to one configuration of the invention. As further depicted inFIG. 2b, which shows a portion of array200, the contact architecture can be characterized by an array of rectangular cells201, each having a separation distance between cell centers (pitch) C1equal to T in the X-direction and W in the Y-direction. In one configuration of the invention, T=2W. In configurations of the invention, array200may contain hundreds or thousands of cells. It will be understood by those of ordinary skill in the art that each cell201represents a convenient reference unit of contact array200that is repeated along an X-Y grid of the array, and need not have any physical borders that would demarcate one cell from another.

The arrangement ofFIG. 2bcan also be characterized by use of a cell having larger dimensions. For example, the four cells201illustrated inFIG. 2bcould form a larger cell that is repeated over a larger X-Y contact array. However, in the configuration of the invention depicted inFIGS. 2aand2b, cells201represent the smallest unit for a contact array architecture that is repeated throughout array200.

FIGS. 2cand2dillustrate in plan view and side view, respectively, details of a single cell201of the arrangement ofFIG. 2a. Cell201includes two contacts204,204,′ each having a length L1and each containing base portions206and elastic arm portions208. In the contact cell architecture of array200, each contact pair204,204′ exhibits a stagger between the contacts in the positioning of elastic arms208, such that the long axis of the elastic arms do not lie along a common line and do not lie along center line CL. The staggered contact architecture depicted inFIGS. 2aand2b, and in further configurations described below, facilitates an increase in the long dimension of contact arms for any given array pitch of an external array of contacts to be engaged. The terms “staggered contacts” or “staggered contact architecture” as used herein, refer to an arrangement in which a line connecting distal portions of the contact arms of successive contacts forms a staggered pattern (see, for example, line Z ofFIG. 2e).

In the configuration depicted inFIGS. 2cand2d, contacts204and204′ each have a contact arm length L2and are essentially identical except that their mutual orientation is substantially opposite to each other. This opposed pair architecture is characterized by the following features:

A) a common axis defining a long direction of the contacts, in this case along the X-direction;

B) base portions206of respective contacts204,204′ are located towards outer regions at mutually opposite ends of cell201as viewed along the X-direction; and

C) distal end portions209of beams (elastic arms)208of respective contacts204,204′ extend above substrate210away from base portions206and towards mutually opposite ends of cell201as viewed along the X-direction.

Thus, elastic contact arm208of contact204extends in a substantially opposite direction from its base206in comparison to its counterpart contact arm of contact204′.

It is to be understood that the actual physical contact arm length L2, as depicted inFIG. 2dexceeds the projected contact arm length, that is, the apparent contact arm length of contacts204,204′ as it appears in plan view. However, for purposes of simplicity, the label L2is used to denote the true physical contact arm length both in side view and plan view representations.

In comparison to the in-line contact design ofFIG. 1, in the staggered contact architecture exhibited by the pairs of opposed contacts204,204′ depicted inFIGS. 2cand2d, over, the contact arm length L2can exceed WEthe contact array pitch of an external component to be contacted, as illustrated inFIG. 2e. In the staggered architecture, when viewed along the X direction, contact204overlaps its opposed partner contact204′ along nearly the entire length. However, physical overlap is prevented by the stagger in positions of the contacts with respect to centerline CL shown inFIG. 2c. This allows the contact working distance for contacts204,204′ to be increased, as discussed further below.

As depicted inFIG. 2d, contacts204,204′ are attached at base portions206to insulating substrate210. Substrate210and contacts204,204′ can form part of an interposer, a land grid array, a ball grid array, or other electrical connectors that include arrays of contacts. Referring again toFIG. 2b, the cell width along the X-direction (T) is equivalent to the separation of cell centers. In the case where T=2W, the length L2of elastic arms208can be much longer than a corresponding length of the contact arms of contacts101illustrated inFIG. 1a. Accordingly, for a given angle α, the height Hd (FIG. 2d), is also much larger than the corresponding height H1for the shorter contact arms104of the reference, non-staggered, contact architecture shown inFIGS. 1a-c. Height Hd, in turn, represents an upper limit on working distance WD for contact arms204,204′. Thus, working distance of contacts arranged according to the architecture ofFIGS. 2a-2dis substantially greater than that of in-line contacts101. Any connector containing a contact array fabricated according to the architecture ofFIG. 2acan thus have a larger working distance than a connector made having the reference contact arrangement depicted inFIG. 1a.

FIGS. 2eand2ffurther compare details of the contact architecture of the configuration depicted inFIG. 2c, and the reference contact architecture depicted inFIG. 1a. In each case, an array of external device contacts220, having a pitch W, is shown projected over the respective contacts. In particular,FIG. 2edepicts details of one possibility for aligning an external device contact array with the contact arrangement ofFIG. 2a.FIG. 2fdepicts one manner of aligning the same array of external device contacts220ofFIG. 2ewith the reference contact array structure ofFIG. 1a. In this case, only a portion of a row of external contacts220positioned in a line along the X-direction is shown.

As a comparison ofFIGS. 2eand2fillustrates, for both architectures, every external device contact220is engaged by a single contact arm from a respective elastic contact. Thus, the architecture of array200of this invention, as well as reference contact arrangement100, provides contact arrays capable of contacting every contact of an external device having an array pitch of W. However, in the architecture of array200of the present invention, the contacts are capable of much greater vertical displacement (Hd) than that of their counterparts in arrangement100(H1). In configurations of the invention, as suggested by comparison ofFIGS. 1cand2c, displacement Hd may be more than twice displacement H1. This is because the staggered contact architecture provides the ability of the contact arm length L2to exceed WE.

The staggered contact architecture allows adjacent contacts220positioned along the X-direction to be contacted by the pair of staggered contacts204,204′ that are arranged side-by-side with respect to the X-direction. This, in turn, results in a staggered pattern of coupling between contacts204,204′ and220, where a path drawn between the areas of contact D in successive contacts220traces out a zigzag pattern Z (FIG. 2e) instead of a straight line in the reference contact arrangement (FIG. 2f). Thus, although the contact cell pitch T of array200along the X-direction is twice the pitch (W) of the external contact array of contacts220, and the contact arm length L2exceeds W, by staggering contacts204,204′ in array200, the array of external contacts220is completely accessible, that is, each external contact220can be contacted by a contact of array200along the X-direction. In this manner, the effective array pitch in the X-direction for contacts206is WEwhich is the same as array pitch W of in-line contacts104. The term “effective array pitch” refers to a spacing along the long direction of elastic contacts equal to the distance between neighboring contacts in an external contact array that is completely accessible to the elastic contacts.

In general, the stagger architecture of contacts204,204′ along the X-direction permits contact to be made at successive external contacts along the X-direction, where the external contact pitch W is much smaller than the contact arm length L, a result not possible in the in-line architecture ofFIG. 1a. Thus, as illustrated inFIG. 2e, the contact arm length L2can substantially exceed the effective array pitch WE(which is equivalent to W). For example, inFIG. 2e, L2is about 60% greater than WE, and in other configurations could be extended over nearly the entire region R, such that the upper limit on contact length L2is about two times WEminus the base width WBor L2=2WE−WB. Thus, if WBis reduced, L2can approach 2WE. This contrasts to the in-line contact arrangement ofFIG. 2fin which the contact arm length Lcc of contacts104is limited to being less than the value of W (WE) by an amount at least equal to the contact base width, or LCC=WE−WB. Thus, since WBmust have finite dimensions, L2can be more than double Lcc. In other words, it is always true that 2WE−WB>2(WE−WB).

Thus, in comparison to the in-line arrangement depicted inFIGS. 1a-candFIG. 2f, the configuration illustrated inFIG. 2eprovides a manner of increasing the elastic contact displacement range H (and therefore working distance) for a given pitch W of an external device to be contacted. This can be expressed as a normalized working range N, where N=H/W (where H is initial contact height above a substrate for a given arrangement). In the invention configuration illustrated above, N may be more than double that of contacts arranged according to the in-line contact arm arrangement ofFIG. 2f.

FIGS. 2gand2hdepict a connector250with contacts280arranged according to one configuration of the present invention and a conventional connector260, respectively. Connector250includes a plurality of rows285, where each row includes a plurality of contact pairs that make up a cell201, as depicted inFIG. 2c. Connector250also includes a plurality of columns290, where each column also includes a plurality of cells201. Each connector250,260(shown in contact with a 6×6 array270of external contacts) is capable of contacting a 16×8 X-Y array of contacts placed on a square grid. The contact array of connector250is only 8 contacts “wide” when viewed along the X-direction, while it is 16 contacts wide when viewed along the Y-direction.

In one configuration of the invention, contacts204are fabricated using a lithographic process to define and pattern contact elements from a metallic layer (not shown). The contacts are “formed” into three dimensions, such that contact arms208extend above the plane of base portion206, by means of pressing the metallic layer over a set of configurable die. In one configuration, the forming process takes place after metallic contact structures are defined in two dimensions. Details of the contact fabrication process are disclosed in U.S. patent application Ser. No. 11/083,031, filed Mar. 18, 2005, which is incorporated in its entirety herein.

FIG. 3illustrates a side view of a portion of component system300arranged in accordance with another configuration of the present invention. As illustrated, two sets of opposed contacts204,204′ that mirror each other are disposed on opposite sides of insulating substrate304of connector302. The distal portion of elastic arm208of each contact engages a contact pad310or312of respective electrical components306and308, which are disposed on opposite sides of connector302. In one configuration, a pair of contact base portions206a(and206b) associated with contacts disposed on opposite sides of substrate304, are electrically interconnected by conductive vias314formed through substrate304. In this manner, pads310aand312aare electrically connected to each other, and pad310bis electrically connected to pad312b. Thus, for components306and308, contacts that have the same relative position (as determined within an X-Y grid within the plane of a respective component) can be electrically coupled using connector302.

FIG. 4adepicts another contact architecture associated with array400, according to a further configuration of the present invention. In one example, cells402can have substantially the same dimensions as cells201ofFIG. 2b. Cells402each contain a full contact404and portions of two other contacts404. In this case, distal portions of an elastic contact arms406of each contact are located on the same side of the respective base portion408of the contact. Each cell402contains two contact base portions408that are staggered with respect to a cell center line drawn in the X-direction (not shown). Because of this, the overall length projected contact length L3and contact arm length L4of contacts404can be about the same as that of contact arms208ofFIG. 2b. The difference between arrays200and400is that array200includes staggered contacts in which pairs of contacts204,204′ have opposing orientations, whereas contacts404of array400exhibit an “aligned” architecture, that is, all contacts have the same relative positions of base and elastic arm. The contact architecture ofFIG. 4acan be further characterized as a double aligned architecture, meaning that every second contact along the Y-direction occupies the same position within a cell.

FIG. 4billustrates details of contacting geometry when connector410, containing the contact arrangement400, is brought into contact with a square array of contacts420located in an external device (not shown for clarity of viewing). Distal portions of contact arms406, which extend above a plane that contains base portions408, make contact with contacts420at positions marked D. The pattern of D positions inFIG. 4bis substantially the same as that for contact array200illustrated inFIG. 2e.

FIG. 4cillustrates how a device component270having a square array of contacts can be placed on connector410. As in the configuration of the invention depicted inFIG. 2g, contacts from connector410are provided for contacting every contact420. Connector410can be characterized as a connector capable of contacting a 16×8 X-Y array of contacts placed on a square grid such as that contained by 6×6 component270.

In another configuration of the present invention shown inFIGS. 5aand5b, connector500has a triple stagger arrangement of contacts that facilitates contacting every contact of device component270, while providing a much longer elastic contact arm portion502for contacts504. The architecture of connector500can be characterized as a triple aligned architecture, denoting that all contacts have the same relative position of their base and elastic arm, and every third contact in the Y-direction occupies the same relative position in the X-direction. As compared to the double stagger contact architecture discussed above, the triple stagger architecture facilitates a further increase in contact arm length relative to effective array pitch. As illustrated inFIG. 5b, contact arm length L5can approach a value of 3WEminus base width WB. For the same reasons noted above in reference to the double stagger architecture, this means that for any given effective array pitch WE, the contact arm length L5can exceed an in-line contact arm length by a factor of more than three. In other words, it is always true that 3WE−WB>3(WE−WB). Normalized working range can be increased similarly in comparison to in-line contact architecture.

FIG. 6aillustrates a component system600arranged in accordance with another configuration of the present invention. In this case, the region of connector602depicted includes a pair of opposing elastic contacts204a,204bdisposed on one side of connector602, and a pair of ball type connectors606a,606bdisposed on the opposite side of connector602. Contacts204a,204bare electrically connected to respective contacts606a,606bthrough vias314. Base portions206aand206blie directly above respective contacts606aand606b. Accordingly, when connector602engages external components606,608disposed on opposite sides of the connector, an electrical path is established between contact pads610aand612b, and also between610band612a. Ball contacts606a,606bare localized to their respective vias314, that is, they do not extend laterally away from vias314, as do contacts204a,204b, but rather, the ball contacts engage external contacts that lie directly below the respective via. From a plan view perspective, this means that ball contacts606a,606b, respective external contacts612a,612b, and vias314all have a common overlap region O, as illustrated inFIG. 6b. Thus, an electrical connection is established between contact pads in the external components606,608whose lateral position is offset with respect to each other, equivalent to the spacing or pitch (WE) Of the contact arrays of the devices in question.

In the configurations of the invention disclosed above, an enhanced elastic contact arm displacement range Hd is accomplished for connectors used to contact arrays of external components having a separation WEof nearest neighbor contacts in the array. This can be characterized by comparing the ratio of Hd to effective array pitch WE, which represents the minimum array pitch of an external array of contacts that can be fully contacted by the connector contact array. The vertical displacement achievable by an elastic contact, Hd, can also be characterized by a working range, as discussed above. For a given connector having elastic contacts, the normalized working range N will have an upper limit defined by Hd, divided by WE.

According to configurations of the present invention, N for a substantially linearly shaped elastic arm contact can be increased by more than a factor of three for triple stagger arrangements, and more than a factor of two for double stagger arrangements in comparison to that achieved by an in-line contact array arrangement. This is because as discussed above the contact arm length for a given array pitch can be more than double and more than triple in-line contact arm length using double stagger and triple stagger architectures, respectively. As one of ordinary skill in the art would appreciate, other configurations of the invention are possible having arrangements of staggered contacts different from those disclosed above.

FIG. 7illustrates a method for forming a connector with enhanced working range, according to one configuration of the invention. In step702, an insulating substrate is provided to support contacts in the connector.

In step704, a metallic sheet material is provided from which to form metallic contacts to be used in the connector. The metallic sheet preferably is a material that has reasonable elastic properties.

In step706, an array of two dimensional contacts is defined in the metallic sheet. This can be accomplished by lithographic and etching techniques that etch metallic shapes in the sheet such as the general features in contacts204depicted in plan view inFIG. 2c. The relative arrangement of two dimensional contacts in the contact array can be in any of the exemplary architectures of the invention depicted above.

In step708, the contact sheet is bonded to the insulating substrate.

In step710, contacts are formed in three dimensions by deforming contact arm portions of the contact to extend above the plane of contact base portions, as depicted inFIG. 2d.

In step712, interconnections are provided in the substrate to electrically connect base portions of the contacts disposed on one side of the substrate to an opposite side of the substrate. The interconnects can be vias or other traces.

In step714, contacts are formed on the opposite side of the substrate and connected to the interconnects, so that electrical connection can be made from the contacts on the first side of the substrate to the opposite side. At least the contacts disposed on the first side of the substrate exhibit an enhanced normalized working range so that the connector exhibits this property when coupling to one or more external components.

The foregoing disclosure of configurations of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the configurations described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. For example, the scope of this invention includes contacts having contact arms with convex or concave curvature with respect to the plane of the contact base. In other variations, the contact arms may be tapered along their length as viewed from the top or as viewed from the side. Additionally, the invention covers connectors having combinations of different contact arrays, for example, those depicted inFIGS. 4cand5a.

In addition, although embodiments disclosed above are directed toward arrangements where the contact dimensions are uniform between different contacts, other embodiments are possible in which contact size varies between contacts. Moreover, embodiments in which each contact “arm” comprises a plurality of contact arms are contemplated. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents.