Abstract:
A cantilever probe has an elbow for bonding to a dual plane fixture plate for a highly stiff and precise angled fixture of the bonded cantilever probe with minimal real estate consumption. The cantilever probe may feature a tip positioning pin and an elbow positioning pin fitting into corresponding holes of the fixture plate and a sacrificial assembly plate. Separate fan-out beams may be attached to the fixture plate and conductively connected to respective elbows once the cantilever probes are fixed. The fan-out beams in turn may be conductively connected with their respective peripheral ends to large pitch apparatus terminals of a circuit board. A probe apparatus may be easily customized by providing varying drill patterns of the positioning holes for fan-out beams and cantilever probes to match pitch requirements of the tested circuit chips.

Description:
CROSS REFERENCE 
   The present invention cross references the U.S. Patent Application of the same inventor January Kister, titled “Freely Deflecting Knee Probe With Controlled Scrub Motion” filed May 21, 2004, application Ser. No. 10/850,921, which is hereby incorporated by reference. 
   FIELD OF INVENTION 
   The present invention relates to cantilever probes. In particular, the present invention relates to a cantilever probe with angle fixture and a probe apparatus therewith. 
   BACKGROUND OF INVENTION 
   Continuing miniaturization of cantilever probes imposes new challenges for their positioning and fixing within a probe apparatus. Cantilever probes are commonly fixed with their peripheral ends having their cantilever portion with the contacting tip free suspended to provide the required flexibility. To provide sufficient positioning accuracy, the fixture portion of the cantilever probe is commonly extensively dimensioned, which in turn consumes extensive real estate forcing multilayer cantilever probe assemblies with varying cantilever geometries. Such varying cantilever geometries result in different deflection behavior and limited average positioning accuracy of all cantilever probes of a probe apparatus. In addition, cantilever probes of the prior art are commonly fixed in a surrounding fashion along a linear fixture element, which requires additional surrounding referencing and/or positioning structures, which in turn consume additional space between the cantilever probes. 
   Prior art cantilever probes are commonly fabricated with lengthy peripheral structures for a sufficient fanning out between the ever decreasing test contact pitches and circuit board contacts of the probe apparatus. Peripheral fan-out structures may be a multitude of the cantilever portion, which reduces the positioning accuracy of the ever decreasing cantilevers and contacting tips. 
   For the reasons stated above, there exists a need for a cantilever probe and probe assembly that provides maximum contacting tip accuracy together with homogeneous deflection behavior within a minimum footprint. In addition, cantilever probes may be simple and highly consistent in geometry for inexpensive mass production. Other affiliated structures of the probe apparatus may be inexpensively fabricated to accommodate for highly individualized probe apparatus configurations. The present invention addresses these needs. 
   SUMMARY 
   A cantilever probe has an elbow for bonding to a dual plane fixture plate having two substantially non parallel fixture surfaces in an angle corresponding to the elbow. The dual plane angled fixture between elbow and fixture plate provides for a highly stiff and precise hold of the bonded cantilever probe with minimal real estate consumption. The cantilever probe may feature at least two positioning pins one of which may be placed at the contacting tip and the other one may extend from at least one of two contacting faces of the elbow. The elbow positioning pin may fit into a corresponding elbow pin hole on one of the fixture surfaces. The tip positioning pin may fit into a corresponding tip pin hole of a sacrificial assembly plate temporarily combined with the fixture plate for a precise positioning of the cantilever probes during curing, setting or hardening of a bonding agent between the fixture plate an the elbow. After assembly of a number of cantilever probes, the sacrificial plate may be removed and the tip pins eventually sanded to a common plane. 
   Separate fan-out beams may be aligned with beam positioning pins on and attached to the fixture plate. The fan-out beams are aligned and conductively connected with their probe connect ends to respective probe elbows once the cantilever probes are fixed. The fan-out beams in turn may be conductively connected with their respective peripheral connect ends to well known large pitch apparatus terminals of a circuit board. Cantilever probes and fan-out beams may have geometries suitable for inexpensive mass fabrication by well known masked electro deposition fabrication techniques. A probe apparatus may be easily customized by providing varying drill patterns of the positioning holes for fan-out beams and cantilever probes to match pitch requirements of the tested circuit chips. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1A  is a front view of an exemplary cantilever probe of the preferred embodiment parallel a symmetry plane of the cantilever probe. 
       FIG. 1B  is a perspective view of the cantilever probe of  FIG. 1A . 
       FIG. 2  is the perspective view of a first portion of a fixture plate including two fixture surfaces and elbow alignment holes. 
       FIG. 3  is the perspective view of the fixture plate of  FIG. 2  together with a sacrificial spacing structure and sacrificial assembly plate. 
       FIG. 4  is the perspective view of the plates of  FIG. 3  with a number of assembled cantilever probes of  FIGS. 1A ,  1 B. 
       FIG. 5  is the perspective view of assembled probes and fixture plate of  FIG. 4  with removed sacrificial spacing structure and sacrificial assembly plate. 
       FIG. 6  is the perspective view of a second portion of a fixture plate including the first portion of  FIG. 2  and alignment holes for fan-out beams. 
       FIG. 7  is the perspective view of an exemplary fan-out beam. 
       FIG. 8  is the perspective view of the assembled cantilever probes and fixture plate of  FIG. 5 , the fixture plate of  FIG. 6  and a number of assembled fan-out beams of  FIG. 7  conductively connected with respective cantilever probes. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1A ,  1 B, a cantilever probe  1  for test contacting a well known test contact of a tested electronic circuitry along a contacting axis CA may have a tip positioning pin  14  configured for the test contacting. The tip positioning pin  14  may also be configured for an aligning insertion in a respective one of tip pin holes  43 A– 43 N (see  FIG. 3 ) also along the contacting axis CA. The cantilever probe  1  may further feature a cantilever  13  for resiliently holding the tip positioning pin  14  with respect to the contacting axis CA with a predetermined deflection behavior including a well known scrub motion along the symmetry plane SP. 
   A base arm  11  may rigidly extend from said cantilever probe  13  such that operational deflection of the cantilever  13  leaves a base arm assembly face  111  substantially free of deformation. An offset arm  12  extends substantially rigid from the base arm  11  in a substantially non parallel elbow angle AE defining together with the base arm  11  a fixture elbow  10  for rigidly fixing the cantilever probe  1  preferably via base arm assembly face  111  and offset arm assembly face  122 . An elbow positioning pin  15  extends from one of the base arm  11  and the offset arm  12  along an elbow pin axis PA, which is substantially parallel to the contacting axis CA. The elbow positioning pin  15  is configured for an aligning insertion in a respective one of elbow pin holes  23 A– 23 N (see  FIGS. 2 ,  6 ) together with aligning insertion of the tip positioning pin  14 . The base arm assembly face  111  has a length  111 L and the offset arm assembly face  121  has length  121 L. The contacting axis CA is in a probe pin distance AP to the elbow pin axis PA. 
   The cantilever  13  may preferably have a bend  131  terminating at the base arm  11 , which in turn may preferably extend substantially parallel to the contacting axis CA. In that case, the elbow positioning pin  14  may extend from the offset arm  12 . 
   The cantilever  13 , the base arm  11  and the offset arm  12  may have a continuously protruding profile perpendicular with respect to the symmetry plane SP and the contacting axis CA. In such case, the cantilever probe  1  may be fabricated by a masked electro deposition process in which a central layer including the position pins  14 ,  15  is interposed between profile layers. As a result, the positioning tips  14 ,  15  may have at least rectangular but preferably square cross section. The cantilever probe  1  may consequently be also substantially symmetric with respect to the symmetry plane SP that coincides with the contacting axis CA and the elbow pin axis PA. 
   Deflection behavior of the cantilever  13  may be tuned by adjusting the cantilever length  13 L, cantilever height  13 H, profile width  1 W as well as shape and material composition of the cantilever  13  as may be well appreciated by anyone skilled in the art. Furthermore, instead of the cantilever  13  another suspension structure may be employed such as a suspension knee disclosed in the cross referenced U.S. Application, titled “Freely Deflecting Knee Probe With Controlled Scrub Motion”. Thereby, the tip positioning pin may be combined with the suspension knee at the contacting face. 
   Referring to  FIG. 2 , a probe fixture plate  2  for fixedly holding a number of cantilever probes  1  may have a first fixture surface  22  featuring a number of primary positioning holes  23 A– 23 N for the aligned insertion of a number of elbow positioning pins  15 . The probe fixture plate  2  may additionally feature a second fixture surface  21  in a substantially non parallel fixture surface angle SA to said first fixture surface  22 . The fixture surface angle SA corresponds to the elbow angle AE. The second fixture surface  22  preferably extends in substantially constant offset  23 O to an array direction of the positioning holes  23 A– 23 N arrayed with positioning hole pitch  23 P. 
   In case the primary elbow positioning holes  23 A– 23 N are linearly arrayed, the second fixture surface  21  may be planar. The fixture surface angle SA may be perpendicular. Referring to  FIG. 3 , a temporary plate assembly  100  may include a sacrificial assembly plate  4  separable attached to an attachment face  24  of the probe fixture plate  2 . The sacrificial assembly plate  4  has a third surface  42  with secondary tip positioning holes  43 A– 43 N in a probe positioning hole offset AL that corresponds to the probe pin distance AP. A secondary hole pitch  43 P may be preferably equal or less than the primary hole pitch  23 P. The attachment face  24  may be opposite the first fixture surface  22 . 
   The third surface  42  may be in a surface offset  40 H to the first fixture surface  22  in direction of the primary holes  23 A– 23 N and secondary holes  43 A– 43 N. In the case where the surface offset  40 H is substantially larger than a fixture plate height  20 H, a sacrificial spacing structure  3  may be interposed between the probe fixture plate  2  and the sacrificial assembly plate  2 . Sacrificial assembly plate  4  and sacrificial spacing structure  3  may be separable by use of a selectively dissolvable solder or other bonding agent as may be well appreciated by anyone skilled in the art. 
   Referring to  FIG. 4 , a probe bonding assembly  101  may include the temporary plate assembly  100  and a number of cantilever probes  1 A– 1 N aligned inserted with their elbow positioning pins  15  in a respective one of the elbow positioning holes  23 A– 23 N and their tip positioning pins  14  concurrently aligned inserted in a respective one of the tip positioning holes  43 A– 43 N. As a result, the base arm assembly face  111  may be brought into a combining proximity with the second fixture surface  21  and the offset arm assembly face  121  may be brought into a combining proximity with the first fixture surface  22 . For that purpose, the elbow pin axis PA may be in an assembly face offset PO to the adjacent assembly face that is equal or slightly larger the constant offset  23 O between the center of the elbow positioning holes  23 A– 23 N and the second fixture surface  21 . In case of the cantilever probe  1  the assembly face offset PO is between offset arm assembly face  121  and the elbow positioning pin  15 . 
   A robotic probe assembling may be accomplished in combination with a vacuum fixture holding a cantilever probe  1  and moving it towards assembly position in direction along the contacting axis CA and elbow pin axis PA. In cases where the scale of the positioning pins  14 ,  15  is close to the positioning accuracy of the robotic assembly system, a sequential aligned insertion may be accomplished by varying the elbow pin height  15 H from the tip pin height  14 H. Once a first aligned insertion is accomplished, the second aligned insertion may be attempted without risk of again misaligning the other of the positioning pins  14 ,  15 . 
   Referring to  FIG. 5 , a fixed probe assembly  102  features a number of cantilever probes  1 A– 1 N fixed with their respective fixture elbows  10 A– 10 N to the fixture plate  2  preferably by applying a combining or bonding agent in the combining proximity between the assembly faces  111 ,  121  and their respective fixture surfaces  21 ,  22 . A combining or bonding agent may be for example an epoxy or a solder. In case a solder is used, an electrically conductive connection may be simultaneously established between the fixture elbows  10 A– 10 N and eventual conductive traces on one or both of the fixture surfaces  21 ,  22 . Sacrificial assembly plate  4  and eventual sacrificial spacing structure  3  are removed. The tip positioning pins  14 A– 14 N are configured to operate additionally for test contacting along their respective contacting axis CAA-CAN with an eventual scrub motion. For that purpose, the tip positioning pins  14 A– 14 N may be adjusted to a common tip clearance  1 H by a sanding operation. 
   The contacting axes CAA-CAN are in a contacting pitch  1 P that corresponds to the secondary hole pitch  43 P. In case of linear arrayed elbow positioning holes  23 A– 23 N and planar second fixture surface  21 , the cantilever probes  1  may be parallel assembled with constant gap  1 G and constant profile width  1 W. 
   The elbow positioning holes  23 A– 23 N may also be arrayed with curvature and the second fixture surface  21  may be concentric as well as the secondary positioning holes  43 A– 43 N being concentrically arrayed with proportionally reduced secondary hole pitch  43 P. In that case, the cantilever probes  1  may be arrayed with minimal contacting pitch  1 . Furthermore, the probes  1  may have a proportionally decreasing profile width  1  resulting again in a constant probe spacing  1 G. Another advantage may be a favorably balanced stress distribution as a result of the profile width  1  increasing proportionally with the distance from the contacting axes CAA-CAN, which corresponds to the bending stress increasing in the cantilever  13  away from the contacting axes CAA-CAN as may be well appreciated by anyone skilled in the art. 
   The angled fixture is particularly advantageous in minimizing an overall real estate of the fixed probe assembly in perpendicular extension to the contacting axes CAA-CAN. This results on one hand from utilizing the second fixture surface  21  preferably parallel to the contacting axes CAA-CAN, which consumes only a minimal real estate independently of the fixture plate height  20 H. The minimized overall real estate results on the other hand from an increased stiffness and thermal stability of the angled fixture due to the three dimensional configuration of the bonding interface between fixture surfaces  22 ,  21  and the assembly faces  121 ,  111  together with a reduced combining proximity and minimal use of combining agent. Further more, the bonding interface is free of lateral structures in between adjacent cantilever probes  1 , resulting in a maximum profile width  1 , which in turn assists in designing suspension structures highly resistant against inadvertent deviating torsion bending. 
   Referring to  FIG. 6 , the first fixture surface  22  may further feature alignment holes  25 A– 25 N and orienting holes  26 A– 26 N. Each of the alignment holes  25 A– 25 N defines with a respective one of the orienting holes  26 A– 26 N one of the positioning axes  27 A– 27 N. The positioning axes  27 A– 27 N may be oriented in a fan-out angle AF with respect to an adjacent one of the positioning axes  27 A– 27 N. Consequently, an alignment hole distance DA between adjacent ones of the alignment holes  25 A– 25 N is substantially smaller than an orienting hole distance DO between adjacent ones of the orienting holes  26 A– 26 N. The alignment hole distance DA is about the same as the positioning hole pitch  23 P. The distance of the positioning axes  27 A– 27 N corresponds to a beam pin distance  57  (see  FIG. 7 ). 
   Particular advantageous is a fabrication step of concurrently drilling all holes  23 A– 23 N,  43 A– 43 N,  25 A– 25 N and  26 A– 26 N without need of intermediate repositioning of the temporary plate assembly  100 , which provides for highest hole position accuracies with minimal machining effort. In that way highly individualized probe assemblies may be fabricated in combination with standardized cantilever probes  1  and fan-out beams  5  (see  FIG. 7 ). 
   Referring to  FIG. 7 , a fan-out beam  5  may be fabricated from electrically conductive material with a beam length  51 L. The fan-out beam  5  may have a probe connect end  52  and a peripheral connect end  53  on a connect surface  51 . Opposite the connect surface  51  may be a beam attachment face  56  featuring an elbow alignment pin in the proximity of the probe connect end  52 . A fan-out orienting pin  55  may be with its orienting pin axis  55 C in a beam pin distance  57  to alignment pin axis  54 C. The fan-out beam  5  may be fabricated similarly like the cantilever probe  1  with a masked electro deposition process in a multi layer fashion. 
   Referring to  FIG. 8 , a probe and fan-out beam assembly  103  features a fixed probe assembly  102  with the fixture plate  2  of  FIG. 6  with respect to which a number of fan-out beams  5 A– 5 C are positioned via their elbow alignment pins  54  in respective ones of the alignment pin holes  25 A– 25 N and oriented with their orienting pins  55  in respective ones of the orienting pin holes  26 A– 26 N such that their probe connect ends  52 A– 52 N are in close proximity to respective ones of elbow fixtures  10 A– 10 N. The fan-out beams  5  may be bonded or combined with its attachment face  56  with the first fixture surface  22 . Conductive bridges  6 A– 6 N electrically conductive connect fixture elbows  10 A– 10 N with respective ones of the probe connect ends  52 A– 52 N such that a solid conductive path is established between the tip positioning pins  14 A– 14 N and respective ones of the peripheral connect ends  53 A– 53 N. The conductive bridges  6 A– 6 N may be fabricated by well known wire bonding and/or wedge bonding techniques. 
   The fan-out beams  5  may be alternately lengthened for a zigzag connect end pattern for increased spacing between adjacent ones of the peripheral connect ends  53 A– 53 N, which may be conductively connected to well known assembly contacts of a probe apparatus. 
   Fixed probe assembly  102  and/or probe and fan-out beam assembly  103  may be part of a probe apparatus for testing electronic circuitry. Fan-out beams  5  and probes  1  may be economically fabricated in large number in a common configuration and combined with individually fabricated fixture plates  2 . 
   Accordingly, the scope of the invention described in the specification above is set forth in the following claims and their legal equivalent: