Abstract:
Sheet metal radially and axially coiled around a coiling axis forms a resilient band spring with a base arc for interlocking with a base plate and a contacting tip for contacting with test contacts. The spring band coils in a fashion such that at least two adjacent coils overlap in axial direction radially supporting and conductively contacting each other at least in operationally deflected condition of the connector. A number of connectors may be held via their base arcs in correspondingly shaped fits of a base plate. The connectors may have one or two opposing tips and being either conductively connected with their base arc to a PCB or held in through holes thereby operating as interconnectors. The contacting tip may be centered, off centered or circumferentially and multiplicatively positioned for zero, radial or circumferential scrubbing action. Two or more independent connectors may be intertwined around a single coiling axis.

Description:
FIELD OF INVENTION  
       [0001]     The present invention relates to testing connectors. In particular, the present invention relates testing connectors of coiled sheet metal like material.  
       BACKGROUND OF INVENTION  
       [0002]     In the field of electronic circuitry testing, test contact size and array pitch ever decrease. At the same time test signal voltages drop and test signal frequencies increase. Hence there exists a continuous need for testing connectors with improved electrical properties in the conductive path along the testing connector and structural properties including maximum deflection, lateral stiffness, inexpensive fabrication, simple assembly with tight pitch and tunable scrubbing within a minimal footprint. The present invention addresses these needs.  
       SUMMARY  
       [0003]     A connector is fabricated from sheet metal like material radially and axially coiled around a coiling axis such that a resilient coil spring band is formed between a radially resilient base arc for interlocking with a base plate and a contacting tip for temporarily contacting test contacts. The spring band extends and coils from the base arcs in a fashion such that at least two adjacent coils overlap in axial direction with respect to the coiling axis and radially support each other at least in operationally deflected condition. The radial support of adjacent coils provides for a conductive shortcut path across the coils from the contacting tip to the base arc. A number of connectors may be tightly arrayed and held via their base arcs in correspondingly shaped fits of a base plate.  
         [0004]     The connectors may have spring bands extending from the base arc in opposite direction forming interconnects that provide a direct conductive connection between opposing peripheral contacting tips at the opposing peripheral ends of the spring bands. The base fits may be through holes with recess features receiving interlocking structures radially extending from the base arc. The connector may also be conductively connected to a conductive lead of a base plate in an exemplary configuration of a printed circuit board.  
         [0005]     The contacting tip may be centered, off centered or circumferentially and multiplicatively positioned with respect to the coiling axis, which provides for zero, radial or circumferential scrubbing action on the test contact. Two or more independent connectors may be intertwined around the coiling axis.  
         [0006]     The sheet metal coil spring connector provides a minimal conductive path and at the same time a relatively large deflection for a given building height in direction of the coiling axis. In addition, the overlapping spring band coils increase lateral stability opposing off axis forces induced on the contacting tip from scrubbing action. Dependent on the connector&#39;s scale, various well known fabrication techniques may be employed including electroplating for shaping the sheet metal contours and differentiated opposite surface treatment techniques for inducing a controlled coiling of the sheet metal.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0007]      FIG. 1  is a first perspective view of an exemplary interconnect array including sheet metal coil spring connectors in an exemplary configuration with two opposing spring bands, centered contacting tips and clasping interlocking structures.  
         [0008]      FIG. 2  is a top view of a sheet metal coil spring connector of  FIG. 1 .  
         [0009]      FIG. 3A  is a cross section of the sheet metal coil spring connector as indicated in  FIG. 2  by section line A-A.  
         [0010]      FIG. 3B  is a second perspective view of a sheet metal coil spring connector of  FIG. 1 .  
         [0011]      FIG. 4  is a top view of an exemplary sheet metal coil spring connector with off center contacting tip and central interlocking structures.  
         [0012]      FIG. 5  is the second perspective view of the sheet metal coil spring connector of  FIG. 4 .  
         [0013]      FIG. 6  is a third perspective view of the sheet metal coil spring connector of  FIG. 1  in flattened condition during an intermediate fabrication step.  
         [0014]      FIG. 7  is a third perspective view of the sheet metal coil spring connector of  FIG. 4  in flattened condition during an intermediate fabrication step.  
         [0015]      FIG. 8  is the first perspective view of the sheet metal coil spring connector of  FIG. 4  sandwiched with its central interlocking features in between sandwich plates. The sandwich plates are depicted in section view.  
         [0016]      FIG. 9  is a fourth perspective view of an exemplary sheet metal coil spring connector composed of two intertwined sheet metal structures.  
         [0017]      FIG. 10  is the second perspective view of an enlarged spring band end including a centered contacting tip of the sheet metal coil spring connector of  FIG. 1 .  
         [0018]      FIG. 11  is the second perspective view of an enlarged spring band end including an off center contacting tip of the sheet metal coil spring connector of  FIG. 4 .  
         [0019]      FIG. 12  is the second perspective view of an enlarged spring band end including multiple circumferentially arrayed contacting tips of the sheet metal coil spring connector of  FIG. 8 .  
         [0020]      FIG. 13  is a front view of a spectral displacement plot of a spring band under an exemplary analysis condition and a contacting condition in accordance with the centered contacting tip of  FIG. 10 . Transparently superimposed in grey is the same spring band in non deformed condition.  
         [0021]      FIG. 14  is a top view of the spectral displacement plot of  FIG. 13  also with transparently superimposed non deformed grey spring band.  
         [0022]      FIG. 15  is a front view of a spectral displacement plot of a spring band under the exemplary analysis condition of  FIG. 13  and a contacting condition in accordance with the off centered contacting tip of  FIG. 11 . Transparently superimposed in grey is the same spring band in non deformed condition.  
         [0023]      FIG. 16  is a top view of the spectral displacement plot of  FIG. 15  also with transparently superimposed non deformed grey spring band.  
         [0024]      FIG. 17  is a top view of a spectral displacement plot of a spring band under the exemplary analysis condition of  FIGS. 13, 15  and a contacting condition in accordance with the multiple circumferential contacting tips of  FIG. 12 . Transparently superimposed in grey is the same spring band in non deformed condition. 
     
    
     DETAILED DESCRIPTION  
       [0025]     According to  FIGS. 1-5 , a sheet metal coil spring connector  10  may include a radially resilient base arc  103  preferably concentric to a coiling axis CA. The connector  10  may further include a spring band  102  extending from the base arc  103 . The spring band  102  coils radially and axially with respect to the coiling axis CA such that at least two adjacent coils of the spring band  102  overlap in axial direction and radially support each other at least in operationally deflected condition. The operationally deflected condition may occur during operational contacting of the contacting tip(s)  101 A,  101 B,  101 C (see  FIG. 12 ) with a test contact within a probe apparatus as may be well appreciated by anyone skilled in the art.  
         [0026]     As shown in  FIG. 3A , the radial support may occur in conjunction with the contacting of adjacent overlapping coils, which may provide for a shortcutting conductive path CP across the individual coils and approximately in direction parallel to the coiling axis CA. Defining design elements of the connector  10  include a first lengthy cross section  1031  of the base arc  103  with its first long side being substantially parallel to the coiling axis CA and a second lengthy cross section  1021  of the spring band  102 . The second lengthy cross section  1021  may have its second long side preferably parallel to the coiling axis CA.  
         [0027]     In an alternate embodiment, the second long side may alternatively be in a positive angle with respect to the outward pointing coiling axis CA providing a circumferential conical interlocking of adjacent loops during operational deflection as may be well appreciated by anyone skilled in the art. The circumferential interlocking may assist in increasing the connector&#39;s  10  lateral stiffness and/or spring force and may also assist in reducing electrical resistance of the shortcutting conductive path CP.  
         [0028]     Interlocking structures  104 A,  104 B may radially protrude from the base arc  103 . As shown in  FIG. 1 , clasping interlocking structures  104 A may extend beyond the boundaries of a base plate fit  111  and clasp the base plate  11  on its top and bottom faces  112 ,  113 . As shown in  FIG. 8 , central interlocking structures  104 B may protrude centrally from the base arc  103  interlocking with a central recess feature  116  of the base plate  11 .  
         [0029]     Referring to  FIG. 1 , the connector  10  may be assembled in the base plate fit  111  by relying on the base arc&#39;s  103  radial resilience to reduce the clasping interlocking structure&#39;s  104 A radial extension below the extension of the base plate fit  111  such that the base are  103  may be inserted into the base plate fit  111 . This assembly method may be preferably utilized in combination with the clasping interlocking structures  104 A. Referring to  FIG. 8 , the connector  10  may also be assembled by providing two sandwich plates  114 ,  115  separated across the recess feature  116  such that the connector  10  may be placed with its interlocking structure(s)  104 B in the open recess feature  116 . The connector  10  may align itself within the base plate fit  111  via a snuggle contact of the base arc  103  on the side walls of the base plate fit  111  and/or by circumferentially arraying at least three interlocking structures  104 A,  104 B such that the connector  10  is held on the base plate fit  111  in a spatially fully defined position and orientation with respect to the base plate  11 .  
         [0030]     The connector  10  may feature two representations of the spring band  102  extending from the base arc  103  in opposite direction substantially along the coiling axis CA. In that configuration, the connector  10  operates as a well known interconnector establishing conductive contact between two opposing contacts of which one may be the test contact and the other one a contact of the probe apparatus. As illustrated in  FIG. 1 , the base plate fit  111  may be configured as a through hole holding the connector  10  such that the two spring bands  102  extend from opposite top and bottom sides  112 ,  113  of the base plate  11 .  
         [0031]     Referring to  FIG. 8 , the connector  10  may also be conductively connected via its base arc  103  and/or via the interlocking structures  104 A,  104 B to a conductive lead  118 . The conductive connection may be established by contact force and/or a soldered connection as may be well appreciated by anyone skilled in the art. One or both sandwich plates  114 ,  115  may be a well known printed circuit board (PCB).  
         [0032]     Referring to  FIGS. 6, 7 , the connector  10  may be fabricated in flat condition from flat sheet metal like material by sputtering, electroplating, etching, laser cutting, or stamping. The coiling of the base arc  103  may be accomplished by differentiated opposite surface treatment techniques for inducing a controlled coiling of the sheet metal along deformation fronts DF 1  and/or DF 2 . In context with the present invention, differentiated opposite surface treatment includes metal deposition induced stresses, laser scribing, ion implantation, rolling or other heat application techniques that introduce surface tensions at different levels on the opposite top and bottom side of the flattened connector shapes  100 . The deformation fronts DF 1 , DF 2  are thin, linear areas along which a change in the sheet metal structure is induced preferably substantially homogeneous but at least symmetrical in direction along the deformation fronts DF 1 , DF 2  within the lateral boundaries of the shapes  100 . Symmetrical structure modification may be along the deformation fronts DF 1 , DF 2  may be induced for example with a combined cutting and rolling operation during which an angled contour stamp progressively cuts out the shapes  100  as is well known in the field of sheet metal cutting. The cutting stamp may be angled such that the cut progresses in conjunction with the deformation fronts DF 1 , DF 2 .  
         [0033]     During fabrication, the deformation fronts DF 1 , DF 2  may continuously progress as may be the case during rolling and progressive cutting or may be implemented in repetitive steps as for example during laser scribing. The orientation of the deformation fronts DF 1 , DF 2  defines the orientation of the first and second long sides. A deformation front DF 1  parallel to the coiling axis CA results in long sides substantially parallel to the coiling axis CA. A deformation front DF 2  non parallel to the coiling axis CA may result in conical coils with long sides in an angle to the coiling axis CA as may be well appreciated by anyone skilled in the art. Deformation fronts DF 1 , DF 2  may be defined in context with the sheet metals deformation properties and the final coiling configuration of the connector  10  as may be well appreciated by anyone skilled in the art.  
         [0034]     The differentiated opposite surface treatment may also be induced prior to shaping of the flattened connector shapes  100 . For example, a sheet metal stripe of continuous width may be rolled up to a spiral in correspondence to the final connector  10 . The sheet metal may be of a resilience such that the up rolled stripe may be stretched out and adhered to a planar substrate without loosing its previously induced spiral shape. After cutting out the shapes  100 , the work piece may be released from its substrate allowing it to roll up again into its previously induced coiled condition.  
         [0035]     Referring to  FIG. 9 , a connector  10  may be composed of two or more sheet metal structures intertwined around the coiling axis CA. Each of the independent structures has interlocking structures  1041 ,  1042 , a base arc  1031 ,  1032 , spring bands  1021 ,  1022  and contacting tips  1011  and  1012 . The contacting tips  1011 ,  1012  may be configured as edges in a cone angle to the coiling axis CA providing a self centering on a spherical test contact as may be well appreciated by anyone skilled in the art.  
         [0036]     Scrubbing action during test contacting is influenced by the configuration of the contacting tips  101 A,  101 B,  101 C. For a contacting tip  101 A as in  FIG. 10 , which is substantially centered with respect to the coiling axis CA, lateral forces may be neglect able in a first contacting condition with a contacting force applied on the contacting tip  101 A in direction axially along the coiling axis CA and a test contact substantially perpendicular to the coiling axis CA at least at the interface between the centered connecting tip  101 A and the test contact. The spectral displacement plots of  FIGS. 13 and 14  depict the resulting spatial displacement for a given exemplary configuration of a sheet metal coil spring connector  10  and for a given contacting force axially along the coiling axis CA. The scale in the  FIGS. 13-17  illustrate the spectral colors associated with a proportional displacement wherein dark blue represents zero displacement and wherein dark red represents maximum spatial displacement. Also in the  FIGS. 13-17 , a natural non deflected connector  10 N is transparently superimposed in grey onto the same but deflected connector  10 D plotted in spectral colors. The plots are computer generated with a commercially available finite element analysis software.  
         [0037]     The deflected centered contacting tip  101 AD is displaced relative to the natural centered contacting tip  110 AN mainly in direction axially along the coiling axis CA. A marginal off axis displacement may be contributed to the way the two coils  102  are approaching the base arc  103  creating a wedge allowing for local deflection. See  FIG. 5  where the wedge is visible. Also, a bridge  105  may radially connect the centerend contacting tip  101  with the coils  102  introducing a certain torque on the coil  102  close to the tip. The bridge  105  may be needed for fabrication purposes since the minimum coiling radius has to be greater than zero. For example, a connector  10  made of Stainless Steel with a thickness of about 25_m with 5 coils with an average second long side of about 0.3 mm, a base arc  103  outside diameter of 0.5 mm, an overall height between opposing contacting tips  101 A of 2.5 mm, is estimated to resiliently deflect up to 0.8 mm, under a maximum spring force of about 30 grams.  
         [0038]     A contacting tip  101 B of  FIG. 11  with the contacting tip  101 B in a substantial offset OF to the coiling axis CA a radial displacement component may be defined in combination with deflection in direction axially along the coiling axis CA. This is illustrated in the spectral displacement plots of  FIGS. 15 and 16 . The radial displacement component may be utilized for a radial scrubbing action along the surface of the test contact as may be well appreciated by anyone skilled in the art.  
         [0039]     A contacting tip  101 C of  FIG. 12  with multiple contacting tips  101 C circumferentially arrayed with respect to the coiling axis CA may contact a test contact in a second contacting condition in which the scrubbing action results mainly from an angular displacement of the contacting tips  101 C around the coiling axis CA. In a special case, the contacting tips  101 C may be circumferentially arrayed in conjunction with a spherical shape of the test contact such that the second contacting condition includes a self centering of the contacting tips  101 C with respect to the spherical test contact. The top spectral displacement plot of  FIG. 17  illustrates such case.  
         [0040]     Referring back to  FIGS. 6 and 7 , the coil bands  102  may be tapered with its second long side reducing away from the base arc  103  for a balanced maximum stress and consequently maximum deflection. A certain minimal second long side has to remain at the contacting tip  101 A,  101 B,  101 C for their structural support as may be well appreciated by anyone skilled in the art. A pitch of the coils may be adjusted to the reducing second long side such that all coils overlap at least under operational deflection. In case of a substantially equal orientation of the second long sides of each coil with respect to the coiling axis CA, the flattened coiling bands  102  may be curved towards parallel in direction away from the flattened base arc  103 .  
         [0041]     Accordingly, the scope of the invention described in the specification above is set forth by the following claims and their legal equivalent: