Abstract:
A contact device having a plurality of nominally coplanar first contact elements makes electrical contact with corresponding nominally coplanar second contact elements of an electronic device when the contact device and the electronic device are positioned so that the plane of the first contact elements is substantially parallel to the plane of the second contact elements and relative displacement of the devices is effected in a direction substantially perpendicular to the plane of the first contact elements and the plane of the second contact elements. The contact device comprises a stiff substrate having a major portion with fingers projecting therefrom in cantilever fashion, each finger having a proximal end at which it is connected to the major portion of the substrate and an opposite distal end and there being one or two contact elements on the distal end of each finger. It is necessary to effect relative displacement of the devices by a distance d from first touchdown to achieve last touchdown. The substrate is dimensioned such that relative displacement of the devices by a distance d from first touchdown generates a reaction force at each contact element of about 0.1*f±0.1*f, and further relative displacement by a distance of about 75 microns or 5*d beyond last touchdown generates a reaction force at each contact element of about 0.9±0.1*f.

Description:
This is a Divisional application of U.S. patent application Ser. No. 08/765,661, filed Mar. 4, 1997, now U.S. Pat. No. 6,046,599 which was filed based on PCT/US96/07359, filed May 20, 1996, which claimed priority based on application Ser. No. 08/446,020, filed May 19, 1995, now U.S. Pat. No. 5,621,333. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a contact device for making connection to an electronic circuit device and to methods of fabricating and using such a contact device, such as in the manufacture of semiconductor or other devices. 
     An important aspect of the manufacture of integrated circuit chips is the testing of the circuit embodied in the chip in order to verify that it operates according to specifications. Although the circuit could be tested after the chip has been packaged, the expense involved in dicing the wafer and packaging the individual chips makes it preferable to test the circuit as early as possible in the fabrication process, so that unnecessary efforts will not be expended on faulty devices. It is therefore desirable that the circuits be tested either immediately after wafer fabrication is completed, and before separation into dice, or after dicing, but before packaging. In either case, it is necessary to make electrical connection to the circuits&#39; external connection points (usually bonding pads) in a non-destructive way, so as not to interfere with subsequent packaging and connection operations. 
     U.S. Pat. No. 5,221,895 discloses a probe for testing integrated circuits. The probe includes a stiff metal substrate made of beryllium copper alloy, for example. The substrate is generally triangular in form and has two edges that converge from a support area toward a generally rectangular tip area. There is a layer of polyimide over one main face of the substrate, and gold conductor runs are formed over the layer of polyimide. The conductor runs and the metal substrate form microstrip transmission lines. The conductor runs extend parallel to one another over the tip area and fan out toward the support area. A contact bump is deposited on the end of each conductor run that is on the tip area. The tip area of the substrate is slit between each two adjacent conductor runs whereby the tip area is divided into multiple separately flexible fingers that project in cantilever fashion from the major portion of the substrate. 
     The probe shown in U.S. Pat. No. 5,221,895, is designed to be used in a test station. Such a test station may include four probes having the configuration shown in U.S. Pat. No. 5,221,895, the probes being arranged in an approximately horizontal orientation with their contact bumps facing downwards, with the four rows of contact bumps along four edges of a rectangle. The DUT is generally rectangular and has connection pads along the edges of one face. The DUT is placed in a vacuum chuck with its connection pads upwards. The vacuum chuck drives the DUT upward into contact with the probe, and overdrives the DUT by a predetermined distance from first contact. According to current industry standards, such a test station is designed to produce a nominal contact force of 10 grams at each connection pad. Therefore, the amount of the overdrive is calculated to be such that if contact is made at all connection pads simultaneously, so that each contact bump is deflected by the same amount, the total contact force will be 10 grams force multiplied by the number of connection pads. 
     If the material of the probe substrate is a beryllium copper alloy and each flexible finger has a length of about 0.75 mm, a width of about 62 microns and a height of about 250 microns, and the probe is supported so that the mechanical ground is at the root of the fingers, the contact force produced at the tip of the finger is about 7.7 grams for each micrometer of deflection of the tip of the finger. Therefore, if the contact bumps at the tips of the fingers are coplanar and the connection pads of the DUT are coplanar, and the plane of the contact bumps is parallel to the plane of the connection pads, an overdrive of about 1.3 microns from first contact will result in the desired contact force of 10 grams at each connection pad. However, if one of the connection pads should be 1.3 microns farther from the plane of the contact bumps than the other connection pads, when the DUT is displaced by 1.3 microns from first contact, there will be no contact force between this connection pad and its contact bump, and all the contact force that is generated will be consumed by the other contacts. If one assumes that the contact force at a connection pad must be at least 50 percent of the nominal contact force in order for there to be a reliable connection, then the maximum variance from the nominal height that this design will accommodate is ±0.7 microns. However, the height variations of contact bumps and connection pads produced by the standard processes currently employed in the semiconductor industry typically exceed 5 microns. 
     Furthermore, even if the contact bumps are coplanar and the connection pads are coplanar, tolerances in the probing apparatus make it impossible to ensure that the plane of the connection pads is parallel to the plane of the contact bumps, and, in order to accommodate these tolerances, it is necessary to displace the DUT by 75 microns in order to ensure contact at all connection pads. If the dimensions of the finger were changed to accommodate a displacement of 70-80 microns (75 microns±5 microns), the probe would become much less robust. If the probe were supported at a location further back from the root of the fingers, such that most of the deflection would be carried by the substrate rather than the fingers, the ability of the fingers to conform would be limited to 0.13 microns/gram deflection produced at the fingers themselves. 
     The connection pads of the DUT are not coplanar, nor are the connection bumps on the probe. Assuming that the nominal plane of the connection pads (the plane for which the sum of the squares of the distances of the pads from the plane is a minimum) is parallel with the nominal plane of the contact bumps, the variation in distance between the connection pad and the corresponding contact bump is up to 5 microns if both the DUT and the probe are of good quality. 
     At present, the connection points on an integrated circuit chip are at a pitch of at least 150 microns, but it is expected that it will be feasible for the pitch to be reduced to about 100 microns within a few years. 
     As the need arises to make connection at ever finer pitches, the stress in a probe of the kind shown in U.S. Pat. No. 5,221,895 increases. If the connection pads are at a spacing of 75 microns, this implies that the width of the fingers must be less than about 50 microns, and in order to keep the stress below the yield point, the height of the fingers must be at least 400 microns. 
     The necessary height of the fingers can be reduced by employing a metal of which the yield point is higher than that of beryllium copper. For example, if the substrate is made of stainless steel, having an elastic modulus of 207×10 9  N/m 2 , the maximum height of the fingers can be reduced to about 350 microns. However, it follows that the deflection is reduced below that necessary to comply with typical height variations found in the industry. Additionally, the resistivity of stainless steel is substantially higher than that of beryllium copper, and this limits the frequency of the signals that can be propagated by the microstrip transmission lines without unacceptable degradation. In general, prior techniques found limited application due to difficulties in achieving adequate deflection with the necessary force to achieve reliable connection, while withstanding the generated stresses. 
     In addition, although the microstrip transmission line has adequate characteristics for signals up to a frequency of 5 GHz, and it has been discovered that the so-called stripline configuration is desirable for higher frequencies. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention there is provided a method of making a multilayer composite structure for use in manufacture of a contact device for establishing electrical connection to a circuit device, said method comprising providing a substrate of a metal having a resistivity substantially greater than about 10 micro-ohm cm, adhering a first layer of metal having a resistivity less than about 3 micro-ohm cm to a main face of the substrate, the first layer having a main face that is remote from the substrate, adhering a second layer of dielectric material to the main face of the first layer, the second layer having a main face that is remote from the substrate, and adhering a third layer of metal to the main face of the second layer, the metal of the third layer having a resistivity less than abut 3 micro-ohm cm. 
     In accordance with a second aspect of the present invention there is provided a method of making a contact device for use in establishing electrical connection to a circuit device, said method comprising providing a substrate of a metal having a resistivity substantially greater than about 10 micro-ohm cm, the substrate having a major portion and a tip portion projecting therefrom along an axis, adhering a first layer of metal having a resistivity less than about 3 micro-ohm cm to a main face of the substrate, the first layer having a main face that is remote from the substrate, adhering a second layer of dielectric material to the main face of the first layer, the second layer having a main face that is remote from the substrate, adhering a third layer of metal to the main face of the second layer, the metal of the third layer having a resistivity less than about 3 micro-ohm cm, selectively removing metal of the third layer to form discrete conductor runs extending over the tip portion parallel to said axis, while leaving portions of the second layer exposed between the conductor runs, whereby a multi-layer composite structure is formed, and slitting the tip portion of the composite structure parallel to said axis, whereby fingers are formed that project from the major portion of the composite structure in cantilever fashion and each of which supports at least one conductor run. 
     In accordance with a third aspect of the present invention there is provided a probe apparatus for use in testing an integrated circuit embodied in an integrated circuit chip, said probe apparatus comprising a support member having a generally planar datum surface, a generally planar elastic probe member having a proximal end and a distal end, at least one attachment member attaching the probe member at its proximal end to the support member with the probe member in contact with the datum surface, at least one adjustment member effective between the support member and a location on the probe member that is between the proximal and distal ends thereof for urging the distal end of the probe member away from the support member, whereby the probe member undergoes elastic deflection. 
     In accordance with a fourth aspect of the present invention there is provided a probe apparatus for use in testing an integrated circuit embodied in an integrated circuit chip, said probe apparatus comprising a support member having a bearing surface, a probe member having a proximal end and a distal end and comprising a stiff substrate having first and second opposite main faces and conductor runs extending over the first main face of the substrate from the distal end of the substrate to the proximal end thereof, the conductor runs of the probe member being distributed over a connection region of the first main face of the substrate in a first predetermined pattern, at least one attachment member attaching the probe member to the support member with the second main face of the probe member confronting the bearing surface of the support member, a circuit board comprising a substrate having a main face and conductor runs distributed over a connection region of said main face of the circuit board in a second predetermined pattern, a flexible circuit comprising a flexible substrate having a main face and first and second connection regions, and conductor runs extending between the first and second connection regions of the flexible substrate and distributed over the first connection region in a pattern corresponding to said first pattern and distributed over the second connection region in a pattern corresponding to said second pattern, a first attachment device attaching the flexible circuit to the support member with the first connection region of the flexible circuit confronting the connection region of the probe member and the conductor runs of the flexible circuit in electrically conductive connection with respective conductor runs of the probe member, and a second attachment device attaching the flexible circuit to the circuit board with the second connection region of the flexible circuit confronting the connection region of the circuit board and the conductor runs of the flexible circuit in electrically conductive connection with respective conductor runs of the circuit board. 
     In accordance with a fifth aspect of the present invention there is provided a method of making a multilayer composite structure for use in manufacture of a contact device for establishing electrical connection to a circuit device, said method comprising providing a substrate, adhering a first layer of dielectric material to a main face of the substrate, the first layer having a main face that is remote from the substrate, and adhering a second layer of metal to the main face of the first layer, the metal of the second layer having a resistivity less than about 3 micro-ohm cm. 
     In accordance with a sixth aspect of the present invention there is provided a method of making a contact device for use in establishing electrical connection to a circuit device, said method comprising providing a substrate having a major portion and a tip portion projecting therefrom along an axis, adhering a first layer of dielectric material to the main face of the substrate, the first layer having a main face that is remote from the substrate, adhering a second layer of metal to the main face of the first layer, the metal of the second layer having a resistivity less than about 3 micro-ohm cm, selectively removing metal of the second layer to form discrete conductor runs extending over the tip portion parallel to said axis, while leaving portions of the first layer exposed between the conductor runs, whereby a multilayer composite structure is formed, and slitting the tip portion of the composite structure parallel to said axis, whereby fingers are formed that project from the major portion of the composite structure in cantilever fashion and each of which supports at least one conductor run. 
     In accordance with a seventh aspect of the present invention there is provided a contact device having a plurality of nominally coplanar first contact elements for making electrical contact with corresponding nominally coplanar second contact elements of an electronic device by positioning the contact device and the electronic device so that the plane of the first contact elements is substantially parallel to the plane of the second contact elements and effecting relative displacement of the devices in a direction substantially perpendicular to the plane of the first contact elements and the plane of the second contact elements to generate a contact force of at least f at each pair of corresponding first and second contact elements, wherein it is necessary to effect relative displacement of the devices by a distance d in said direction from first touchdown to last touchdown, said contact device comprising a stiff substrate having a major portion with fingers projecting therefrom in cantilever fashion, each finger having a proximal end at which it is connected to the major portion of the substrate and an opposite distal end and there being at least one, and no more than two, contact elements on the distal end of each finger, a support member to which the substrate is attached in a manner such that on applying force in said direction to the distal ends of the fingers, deflection occurs both in the fingers and in the major portion of the substrate, and means for effecting relative movement of the devices in said direction, and wherein the substrate is dimensioned such that relative displacement of the devices in said direction by a distance d from first touchdown generates a reaction force at each contact element of about 0.1*f±0.1*f, and further relative displacement of the devices in said direction by a distance of about 75 micron or 5*d beyond last touchdown generates a reaction force at each contact element of about 0.9*f±0.1*f. 
     In accordance with an eight aspect of the present invention, there is provided a method for testing/manufacturing devices such as integrated circuits or displays (such as LCD panels), which may include the steps of carrying out a manufacturing process for the DUT, such as a planar-type integrated circuit manufacturing process, positioning the DUT on a positioning device, such as a vacuum chuck (the DUT may be in wafer or die form, in the case of integrated circuits, etc.), effecting alignment of a contact device in accordance with the present invention with the DUT to the extent required for proper placement, effecting relative movement of the DUT with respect to the contact device to establish initial contact thereto (as determined electrically or by a mechanical means), over-driving the relative movement to establish reliable electrical connection, wherein stresses are desirably shared between the extended fingers of the contact device and the substrate of the contact device, applying test signals to the DUT and determining whether the DUT is defective or otherwise within or outside acceptable specifications, recording whether the pass/fail condition of the DUT (which may include mechanical notation, such as inking the DUT if defective, etc., or by data recording), removing the DUT from the positioning device, and packaging and assembling the DUT if acceptable. 
     With the present invention, devices with connection points of fine pitch may be reliably tested and manufactured. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: 
     FIGS. 1-5 illustrate various steps during fabrication of a contact device embodying the present invention, FIGS. 1 and 4 being plan views and FIGS. 2,  3  and  5  being sectional views; 
     FIG. 6 is a partial perspective view of a contact device embodying the invention; 
     FIG. 6A is a sectional view on the line VIA—VIA of FIG. 6; 
     FIG. 7 is a general view, partly in section, of a semiconductor tester; 
     FIG. 8 is a plan view of a circuit board and mounting plate that form part of the test head of the tester shown in FIG. 7; 
     FIG. 9 is an enlarged perspective view of the mounting plate and also illustrates back-up blocks that are attached to the mounting plate; 
     FIGS. 9A,  9 B, and  9 C are sectional view illustrating the manner in which the back-up blocks are attached to the mounting plate; 
     FIG. 10 is an enlarged view of a flexible circuit that is used to connect the circuit board to the contact device; 
     FIGS. 11A and 11B are sectional views illustrating the manner in which the contact device and the flexible circuit are positioned relative to the mounting block; and 
     FIGS. 12A and 12B are sectional views illustrating the manner in which the mounting plate and the flexible circuit are positioned relative to the circuit board. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a substrate  4  of elastic metal having an upper main face  6  and a lower main face. In a preferred embodiment of the invention, the substrate is stainless steel and is about 125 microns thick. The substrate is generally triangular in form, having two edges  8  that converge from a support area  10  toward a generally rectangular tip area  12 . The substrate is substantially mirror-image symmetrical about a central axis  18 . 
     Referring to FIG. 2, a thin film  14  of gold is deposited on the upper main face  6  of the substrate  4  by evaporation or sputtering. The gold film may be augmented by plating if desired. An insulating material such as polyimide is spun or sprayed onto the upper main face of the film  14  in the liquid phase and is then cured to form a layer  16  about 25 microns thick. 
     A layer  20  of gold is deposited over the upper main face  22  of the layer  16  by evaporation or sputtering. The layer  20  is patterned using conventional photolithographic techniques to form strips  26  that extend parallel to the central axis  18  over the tip area  12  of the probe and fan out from the tip area over the triangular part of the substrate  4  toward the support area  10  but which may be connected together at the support area. Each strip has a proximal end and a distal end relative to the support area  10 . Additional metal is then deposited over the strips by plating. After the strips have been built up to the desired thickness, which may be about 12 microns, a layer  30  of photomask material (FIG. 5) is deposited over the upper surface of the structure shown in FIGS. 3 and 4 and holes  32  are formed in that layer over the distal end of each strip  26 , as shown in portion (a) of FIG. 5. A hard contact metal, such as nickel, is deposited into these holes (FIG. 5, portion (b)) by plating, and the photomask material is then removed (FIG. 5, portion (c)). The connections between the strips are removed by etching. In this manner, separate conductor runs are formed over the layer  16 , and each conductor run has a contact bump  34  over its distal end. The conductor runs are 50 microns wide and are at a spacing between centers of about 125 over the tip area. 
     Referring to FIG. 6, a cover layer  40  of polyimide is formed over the conductor runs  26 , over a region of the substrate that is to the rear, i.e. toward the support area  10 , of the rectangular tip area  12  and a layer  44  of gold is deposited over the layer  40  by evaporation or sputtering. The layer  44  may be augmented by plating. The result of the fabrication steps described above is a multilayer structure that comprises the substrate  4 , the gold film  14 , the polyimide layer  16 , the gold conductor runs  26 , the polyimide layer  40 , and the gold layer  44 . 
     The tip area of the multilayer structure is then slit, whereby the tip area is divided into multiple separately flexible fingers  48  that project in cantilever fashion from the major portion of the structure. A given finger of the substrate may carry the distal end portion of a single conductor run, or it may carry the distal end portions of two adjacent conductor runs. The slitting of the tip area may be performed by ablation using a ultraviolet laser. The poor thermal conductivity of stainless steel is a favorable factor with regard to the laser ablation process. The width of the kerf that is removed is about 17 microns, so that the width of a finger is either about 108 microns or about 233 microns. The length of each finger is about 1 mm. 
     The structure shown in FIG. 6 may be used as a contact device for making electrical connection to contact pads of an electrical circuit device, such as an integrated circuit chip or a flat panel display device. The nickel bumps  34  serve as probe elements for contacting the connection pads of the circuit device. When the contact device is in use, each nickel bump contacts a single connection pad of the circuit device. A bump  34   a  that is to contact a ground pad of the circuit device may be connected to the substrate by means of vias  46  formed in holes in the layer  16  before depositing the layer  20 . Multiple vias  46  may be provided along the length of the conductor run  26  that ends at the bump  34   a  in order to ensure that the contact bump  34   a  is firmly grounded. 
     The configuration of the conductor runs and their spacing results in there being a stripline transmission line environment to the rear of the forward boundary of the layer  44 , whereas there is a microstrip transmission line environment forward of the layer  44 . Naturally, the slitting of the tip area results in degradation of the microstrip transmission line environment. In the case of the fingers being about 1 mm long, the microstrip transmission line environment extends to a point that is about 2 mm from the contact bumps. However the degradation is not so severe as to distort signals at frequencies below about 10 GHz to an unacceptable degree. 
     The structure shown in FIG. 6 may be used for probing a circuit device in a semiconductor tester, as will be described with reference to FIGS. 7-11. 
     Referring to FIG. 7, the tester comprises a prober  102  having a frame  102   a  that serves as a mechanical ground. A device positioner  104  having a vacuum chuck  106  is mounted within or as part of the prober  102 . The prober includes stepping motors (not shown) that act on the device positioner for translating the vacuum chuck relative to the frame  102   a  in two perpendicular horizontal directions (X and Y) and vertically (Z), and for rotating the vacuum chuck about a vertical axis. The vacuum chuck holds a device under test, or DUT,  108 . FIG. 7 illustrates the DUT  108  as a die that has previously been separated from other dice of the wafer in which it was fabricated, but it will be appreciated that, with appropriate modifications, the apparatus could be used for testing a semiconductor device at the wafer stage. As shown in FIG. 7, the DUT  108  has contact pads  112 . 
     The tester also comprises a test head  116  that can be docked to the prober so that it is in a reliably reproducible position relative to the prober frame  102   a . The test head  116  includes an essentially rigid circuit board  122  (FIG. 8) that comprises an insulating substrate and conductor runs  126  exposed at the lower main face of the substrate. Vias (not shown) extend through the substrate and terminate at contact pads  128  that are exposed at the upper main face of the substrate. The circuit board  122  is removably held in the test head by screws that pass through holes  130  in the circuit board. When the test head  116  is docked in the prober  102  and the circuit board  122  is installed in the test head, the circuit board  122  is disposed horizontally and the contact pads  128  engage pogo pins  132 , shown schematically in FIG. 7, by which the contact pads of the circuit board are connected to stimulus and response instruments (not shown), for purposes of conducting appropriate tests on the DUT. 
     A mounting plate  136  is secured to the circuit board  122 . The mounting plate is positioned relative to the circuit board by guide pins  134  that project downward from the mounting plate and enter corresponding holes in the circuit board. The manner in which the mounting plate is attached to the circuit board will be described below. 
     The mounting plate has a generally cylindrical exterior surface of which the central axis  138  is considered to be the axis of the plate. The plate  136  is disposed with its axis  138  vertical and defines a cross-shaped through opening (FIG. 9) that is mirror image symmetrical about X-Z and Y-Z planes that intersect at the axis  138 . At the outer end of each limb of the cross, the plate  136  is formed with a notch  140  that extends only part way through the plate and is bounded in the vertically downward direction by a horizontal surface  142 . 
     A backup block  146  having the general shape, when viewed in plan, of a trapezoid seated on a rectangular base is positioned with its rectangular base in one of the notches  140 . Similar backup blocks  148  are mounted in the other notches. The following description of the backup block  146  and associated components applies equally to the backup blocks  148 . 
     The rectangular base of the backup block  146  has a planar mounting surface  150  (FIG. 7) that can be seated against the horizontal surface  142  at the bottom of the notch  140 . For assembling the backup block  146  to the mounting plate  136 , the backup block is formed with a hole  152  extruding through its rectangular base, and the mounting plate is formed with a blind hole  156  that is parallel to the axis of the mounting plate and enters the plate  136  at the horizontal surface  142 . A guide pin  160  is inserted through the hole  152  in the backup block and into the blind hole  156  in the mounting plate, and in this manner the backup block is positioned with a moderate degree of precision relative to the mounting plate. 
     The backup block  146  is then attached to the mounting plate  136  by a vertical locking screw  164  (FIG. 8, FIG. 9A) that passes through a clearance hole  168  in the backup block  146  and enters a threaded bore  172  in the mounting plate  136  and a horizontal locking screw  176  (FIG. 7) that passes through a clearance hole  180  in the mounting plate and enters a threaded bore  184  in the backup block. The backup block  146  is thereby attached to the mounting plate, and the guide pin  160  is then removed. The clearance holes  168  and  180  allow a small degree of horizontal and vertical movement of the backup block relative to the mounting plate. 
     Two horizontal screws  186 , which are horizontally spaced and disposed one on each side of the screw  176 , are inserted through threaded holes in the peripheral wall of the plate  136  and enter blind clearance holes in the backup block. Similarly, two vertical screws  190 , which are horizontally spaced and disposed one on each side of the screw  164 , are inserted through threaded holes in the backup block  146  and engage the surface  142  of the mounting plate  136 . The screws  176  and  186  can be used to adjust the horizontal position of the backup block relative to the mounting plate  136 . By selectively turning the screws  176  and  186 , the backup block can be advanced or retracted linearly and/or rotated about a vertical axis. In similar fashion, using screws  164  and  190 , the backup block can be raised or lowered relative to the mounting plate and/or tilted about a horizontal axis. When the backup block is in the desired position and orientation, the locking screws are tightened. 
     The apparatus shown in FIGS. 7-10 also comprises a contact device  194  associated with the backup block  146 . The contact device  194  is generally triangular and has two edges that converge from a support area toward a generally rectangular tip area. The tip area of the contact device is divided into multiple fingers that extend parallel to an axis of symmetry of the contact device. The contact device includes conductor runs that extend from the support area to the tip area, and one run extends along each finger in the tip area. At its support area, the conductor runs of the contact device are exposed on the underside of the contact device. The contact device may be fabricated by the method that is described above with reference to FIGS. 1-6. 
     Inboard of the rectangular base, the trapezoidal portion of the backup block  146  extends downward toward the central axis  138 . The contact device  194  is disposed below the inclined lower surface of the backup block  146  and is positioned relative to the backup block by guide pins  202  (e.g., FIGS. 11A and 11B) that project from the backup block and pass through alignment holes  204  in the contact device. The manner in which the contact device is attached to the backup block will be described below. 
     The apparatus also comprises a flexible circuit  208  having an inner edge region  208 A and an outer edge region  208 B (e.g., FIG.  10 ). The flexible circuit comprises a substrate of polyimide or similar insulating material, a ground plane (not shown) on the lower side of the substrate, and multiple discrete conductor runs  210  on the upper side of the substrate. Over the inner edge region  208 A, the spacing of the conductor runs  210  corresponds to the spacing of the conductor runs across the support area of the contact device  194 , and over the outer edge region  208 B, the spacing of the conductor runs  210  corresponds to the spacing of the conductor runs  126  along the inner edge of the printed circuit board  122 . 
     The flexible circuit is formed with inner and outer pairs of alignment holes  214 A and  214 B. The inner pair of alignment holes  214 A are threaded by the guide pins  202 , whereby the inner edge region  208 A is positioned relative to the contact device  194 . Similarly, the outer pair of alignment holes  214 B are threaded by the guide pins  134 , whereby the outer edge region  208 B of the flexible circuit is positioned relative to the printed circuit board. The flexible circuit is also formed with two sets of mounting holes  218 A and  218 B. 
     The support area of the contact device  194 , the inner edge region  208 A of the flexible circuit, and a first length  22 A of Shinetsu strip are clamped between the backup block and a clamping plate  226 A by means of screws  230 A. The outer edge region  208 B of the flexible circuit  208 , the inner region of the printed circuit board  122 , and a second length  222 B of Shinetsu strip are clamped between the mounting plate  136  and a second clamping plate  226 B by means of screws  230 B. The positions of the alignment holes  214 A and  214 B relative to the conductor runs of the flexible circuit are such that the conductor runs  210  at the inner edge region  208 A of the flexible circuit are in registration with the conductor runs  26  in the support area of the contact device, and the conductor runs  210  in the outer edge region  208 B of the flexible circuit are in registration with the conductor runs  126  along the inner edge of the printed circuit board. The Shinetsu strip, the thickness of which is exaggerated in FIG. 7, is characterized by anisotropic electrical conductivity when compressed perpendicular to its length: its conductivity is very good in directions perpendicular to its own plate and is very bad in directions parallel to its own plane and to its length. Thus, the Shinetsu strip  222 A connects the conductor runs  26  of the probe member  194  to respective conductor runs  210  of the flexible circuit  208 , and the Shinetsu strip  222 B connects the conductor runs  210  of the flexible circuit  208  to respective conductor runs  126  of the printed circuit board  122 . 
     Tightening of the clamping screws compresses the Shinetsu strips, which then establish a good electrically conductive connection between the conductor runs of the contact device and the conductor runs  126  of the printed circuit board  122 , through the Shinetsu strips and respective conductor runs of the flexible circuit  208 . 
     As described with reference to FIGS. 1-6, the tip area of the contact device  194  is divided into fingers, each of which has a contact run that terminates in a contact bump. Since the tip area is spaced from the support area, at which the contact device is clamped to the backup block, the tip area can be deflected away from the plane of the underside of the backup block. Vertical adjustment screws  234  are fitted in respective threaded holes in the backup block  146 . By appropriate adjustment of the screws  234 , the contact device can be preloaded to a condition in which the contact device  194  is deflected downwards relative to the backup block  146 , and by further adjustment of the screws  234  the tip area can be forced downward, or permitted to rise, or tilted about the axis  18 . It is important to note that the “mechanical ground” therefore extends to a location of the contact device that is beyond the support area but does not extend as far as the lip area. As described more fully below, proper positioning of mechanical ground can enable stress sharing between the fingers of the contact device and the contact device substrate, thereby enabling the contact device to withstand the stresses that result from applying force sufficient to ensure reliable contact between the DUT and the contact device, given the irregularities that can be expected in actual devices/conditions. 
     When all four backup blocks are properly installed in the mounting plate  136 , the tip portions of the four contact devices extend along four edges of a square and are positioned for making electrically conductive contact to the contact pads of the device under test. By observing the DUT through the opening defined between the inner ends of the four backup blocks, the DUT can be positioned for contacting the contact bumps when the DUT is raised by the positioning device. 
     When the DUT is raised relative to the test head, the contact pads of the DUT engage the contact bumps of the contact device. After initial contact has been established (first touchdown), the DUT is raised an initial 10-15 microns, which is sufficient to absorb any expected error in coplanarity of the contact bumps and contact pads and achieve last touchdown (each contact bump is in contact with its respective contact pad). The DUT is then raised by a further 75 microns. The spring rate of the fingers and the spring rate of the base region of the substrate, between the fingers and the support area, are such that the contact force exerted at each contact pad is at least 10 grams. The initial deflection of 10-15 microns is sufficient to provide a contact force of about 2 grams at a single finger, whereas the further deflection of 75 microns provides a contact force of N*10 grams, where N is the number of fingers, or 10 grams per finger. By sharing the deflection between the fingers and the base region of the substrate, a high degree of compliance may be achieved, allowing contact with all the contact bumps, without sacrificing the contact force that is needed to achieve a reliable electrical contact between the contact bumps and the fingers. 
     The elastic nature of the metal of the substrate ensures that when the DUT is brought into contact with the contact bumps, and is slightly over driven, deflection of the fingers provides a desirable scrubbing action and also supplies sufficient contact force for providing a reliable pressure contact between the contact bump and the connection pad of the DUT. 
     The film  14  of gold serves as the ground plane, and the substrate  4 , although conductive, does not contribute to the electrical performance of the device. 
     It is should be particularly emphasized how the present invention achieves desirous stress load sharing between the fingers and the substrate. It has been determined that with available materials, to be of practical size and provide suitable compliance/deflection of the fingers (such as to accommodate deviations from coplanarity, etc.), stress loads induced in the fingers and the substrate should be balanced (i.e., maintained in an acceptable relative range, below the stress limit of the material). Proper positioning of a mechanical ground between the ends of the fingers and the back extremity of the support area can enable controlled balancing of the relative stress loads, while also ensuring an adequate deflection of the fingers to achieve adequate compliance. In preferred embodiments, the relative stress loads of the fingers and substrate are maintained/balanced in a ranges of about 0.7 to 1.3, 0.8 to 1.2 or 0.9 to 1.1. Other ranges may be utilized, provided that a desirable balance is maintained, while of meeting the conditions of adequate deflection/compliance in the fingers, while staying within the stress limits of the constant materials. 
     In combination with the stress load balancing, it also has been discovered that, with available materials, the length of the fingers, controlled by the length of the slit and overall physical geometry, etc., can be chosen to give the desired finger deflection/compliance, such as a desired deflection of greater than about 10 microns, 12, microns or 15 microns, in the case of, for example, 60-80 or 75 microns, etc., of overdrive, while maintaining stress balancing as described above, can produce a probe element that produces reliable connection with the DUT while surviving the resulting stress loads, etc. 
     The present invention may be desirably applied to the testing and manufacture of devices such as integrated circuits or displays (such as LCD panels). Initially, a manufacturing process for the DUT  108  is conducted, such as a planar-type integrated circuit manufacturing process. For display devices, an appropriate LCD or other manufacturing process is conducted. After such manufacturing, the DUT  108  on a positioning device, such as a vacuum chuck  106  of prober  102  (the DUT may be in wafer or die form, in the case of integrated circuits, etc.). The DUT  108  is aligned with contact device  194  to the extent required for proper placement. Thereafter, relative movement is effected of the DUT  108  with respect to the contact device  194  to establish initial contact therebetween (as determined electrically or by a known mechanical means). After initial contact, over-driving of the relative movement to a predetermined degree is conducted (such as described above) to establish reliable electrical connection, wherein stresses are desirably shared between the extended fingers of the contact device and the substrate of the contact device. Positioning of a mechanical ground as in the present invention is particularly desirous in this regards. Thereafter, test signals are applied to the DUT  108  and it is electrically determined whether the DUT is defective or otherwise within or outside acceptable specifications. The pass/fail condition of the DUT may be recorded (which may include mechanical notation, such as inking the DUT if defective, etc., or by data recording). Still thereafter, the DUT  108  may be removed from the positioning device. If the device is acceptable, known packaging and assembling of the DUT may be performed. 
     With the present invention, devices with connection points of fine pitch may be reliably tested and manufactured. 
     It will be appreciated that the invention is not restricted to the particular embodiment that has been described, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims and equivalents thereof. For example, although the invention has been described with reference to the drawings in terms of strip line and microstrip transmission line environments, if the film  14  were omitted and every other conductor run  26  across the contact device were a ground conductor run, a combination of a microstrip and coplanar transmission line environment would be provided. If every other conductor run were not a ground run, a microstrip transmission line environment would be provided as far as the forward edge of the layer  44 , and for some applications, it might be acceptable for the transmission line environment to terminate at this point, provided that it is quite close to the contact bumps. Application of the invention to a semiconductor tester has been described with reference to an implementation in which there is one contact bump on each finger of the contact device, and the use of individual fingers for each contact bump ensures maximum accommodation of non-coplanarity of the contact pads of the DUT. However, it might be advantageous to provide two contact bumps, each connected to its own conductor run, since torsion of the finger accommodates a difference in height of the respective contact pads, and the greater width of the finger provides substantially greater stiffness with respect to deflection. The invention is not limited to testing of devices prior to packaging and may he used for final testing of packaged devices, particularly a device that is packaged for surface mounting, since the terminals are then suitably positioned for engagement by the contact bumps. Further, numerical references, while giving unexpectedly desirable results in the preferred embodiments over prior art techniques, may be adjusted in other embodiments.