Abstract:
A probe retention kit may include a plurality of probe retention devices, each having: (i) a base; (ii) a retention mechanism, coupled to the base, for mechanically coupling a probe substrate with the plurality of probe retention devices; and (iii) solder legs to be inserted into a printed circuit board, the solder legs having opposite ends that extend through the base and provide an alignment mechanism for receiving the probe substrate. Alternative probe retention devices, and systems and methods using same, are also disclosed.

Description:
BACKGROUND 
   Connector-less probing has emerged as an attractive form of probing for logic analyzers and other test equipment. In connector-less probing, a customer may design their printed circuit board (PCB) to incorporate a “landing pattern” of test points. The customer then attaches a connector-less probe to their test equipment, and mounts the connector-less probe to their PCB so that a plurality of spring-pins on the probe engage the plurality of test points in their PCB&#39;s landing pattern. 
   One embodiment of a connector-less probe is disclosed in the United States Patent Application of Brent A. Holcombe, et al. entitled “Connector-Less Probe” (Ser. No. 10/373,820, filed Feb. 25, 2003). An alignment/retention device for mounting a connector-less probe to a PCB is disclosed in the United States Patent Application of Brent A. Holcombe, et al. entitled “Alignment/Retention Device For Connector-Less Probe” (Ser. No. 10/644,365, filed Aug. 20, 2003). 
   Connector-less probes for probing a plurality of breakout vias on the backside of a printed circuit board to which a grid array package is attached are disclosed in the United States Patent Application of Brock J. LaMeres, et al. entitled “Backside Attach Probe, Components Thereof, and Methods for Making and Using Same” (Attorney Docket Numer 10030947-1, filed on Jul. 28, 2004). 
   Agilent Technologies, Inc. (headquartered in Palo Alto, Calif.) markets a number of connector-less probing solutions under the name “Soft Touch”. 
   SUMMARY 
   One aspect of the invention is embodied in a system comprising a printed circuit board (PCB) and a plurality of probe retention devices. The PCB has a pattern of points to be probed. The plurality of probe retention devices are mounted on the PCB adjacent the pattern of points to be probed. Each probe retention device has a retention mechanism and an alignment mechanism. 
   Another aspect of the invention is embodied in a method for probing a pattern of points on a PCB. The method comprises mechanically coupling a plurality of probe retention devices, each having a retention mechanism and an alignment mechanism, to positions adjacent the pattern of points on the PCB. A probe substrate, having a plurality of compression interconnects therein, is then aligned with the alignment mechanisms. The probe substrate is then mechanically engaged with the retention mechanisms, thereby causing the compression interconnects to seat against the pattern of points. 
   Yet another aspect of the invention is embodied in a probe retention kit. The kit comprises a plurality of probe retention devices. Each probe retention device has a base, a retention mechanism, and solder legs. The retention mechanism is coupled to the base for mechanically coupling a probe substrate with the plurality of probe retention devices. The solder legs are provided for insertion into a PCB. Opposite ends of the solder legs extend through the base and provide an alignment mechanism for receiving the probe substrate. 
   Other embodiments of the invention are also disclosed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Illustrative and presently preferred embodiments of the invention are illustrated in the drawings, in which: 
       FIGS. 1 &amp; 2  illustrate the assembly of an exemplary system for probing a pattern of points on a PCB; 
       FIGS. 3 &amp; 4  also illustrate the assembly of the system shown in  FIGS. 1 &amp; 2 , but from an elevation perspective; 
       FIG. 5  illustrates a method for probing a pattern of points on a PCB; 
       FIG. 6  illustrates an exemplary probe retention device mounted on a PCB and mechanically retaining a probe substrate; 
       FIG. 7  illustrates a plan view of an the probe retention device shown in  FIG. 6 ; 
       FIG. 8  illustrates a cross-sectional view of the probe retention device shown in  FIG. 6 ; 
       FIG. 9  illustrates a plan view of the probe substrate shown in  FIG. 6 ; and 
       FIG. 10  illustrates an exemplary probe retention device having a unitary retention and alignment mechanism. 
   

   DESCRIPTION OF THE INVENTION 
   After loading a printed circuit board (PCB  100 ) with a number of components  102 , the loaded board must be tested. At times, an engineer may conduct tests by probing a pattern of points  104  on the PCB  100 . 
   An exemplary pattern of points  104  is variously shown in each of  FIGS. 1-4 . As shown in  FIGS. 3 &amp; 4 , the pattern of points  104  may be positioned on a PCB  100  opposite the side to which a component  102  such as an integrated circuit (IC) is attached. Alternately, the pattern of points  104  could be 1) positioned on the same side of the PCB  100  as the component  102 , or 2) coupled to other and/or different components. 
   By way of example, the pattern of points  104  shown in  FIGS. 3 &amp; 4  is coupled to the IC  102  by means of breakout vias (e.g.,  106 ) in the PCB  100 . For purposes of illustration, each of the breakout vias  106  is shown to be bounded above and below by a somewhat thick pad (e.g.,  108 ,  110 ). Typically, however, these pads  108 ,  110  will be very thin. 
   One way to probe a pattern of points  104  on a PCB  100  is via a probe  112  having a plurality of compression interconnects (e.g.,  114 ) therein. As shown in  FIG. 1-4 , such a probe  112  may generally comprise a substrate  116  formed of an insulating material (e.g., plastic or FR4). The probe&#39;s compression interconnects  114  may then be molded, press fitted, snapped, clipped, screwed, soldered or otherwise secured in its substrate  116  so that they are maintained in a pattern that corresponds to the pattern of points  104  to be probed. 
   The compression interconnects  114  of a probe  112  may take the form of any of a number of different electrically conductive and compressible devices (or materials). In  FIGS. 1-4 , the compression interconnects  114  take the form of spring pins with crowned tips. However, the compression interconnects could also take the form of c-springs or conductive elastomers. 
   Coupled to (or extending from) each compression interconnect  114  is a tail (e.g.,  118 ) or extension that protrudes from the surface of the probe substrate  116  opposite the compression interconnects  114 . In some cases, the tails  118  may comprise rigid fixed pins, as shown in  FIGS. 1-4 . In other cases, the tails  118  may comprise flexible extensions, such as wires. The tails or extensions  118  of the compression interconnects  114  provide a means for coupling leads or cables of a test instrument to the compression interconnects  114 . 
   By way of example, a number of additional probes containing compression interconnects are disclosed in the United States Patent Application of Brock J. LaMeres, et al. entitled “Backside Attach Probe, Components Thereof, and Methods for Making and Using Same” (Attorney Docket Number 10030947-1, filled on Jul. 28, 2004). 
   In use, the compression interconnects  114  of a probe  112  are aligned with a pattern of points  104  to be probed, and pressure is applied to the probe  112  to seat the compression interconnects  114  against the pattern of points  104  (see  FIGS. 2 &amp; 4 ). 
   Depending on the pattern of points  104  to be probed, the required number and placement of compression interconnects  114  in a probe  112  will vary. Different applications therefore require the development of different sizes and shapes of probes. 
   To maintain compression on its compression interconnects  114 , thereby assuring that its compression interconnects  114  remain firmly seated against a pattern of points  104  to be probed, a probe  112  typically needs to be secured to a PCB  100 . Usually, this is accomplished via a connector or bracket of fixed size that is attached to the PCB  100 . Given that it is expensive to design a corresponding connector or bracket for each possible size or shape of probe, the sizes and shapes of probes are typically limited by available connector sizes. It would be preferable, however, if this limitation on probe shapes and sizes did not exist.  FIG. 5  therefore provides a new method  500  for probing a pattern of points  104  on a PCB  100 . 
   In accordance with the method  500 , a plurality of probe retention devices  120 ,  122 ,  124 ,  126 , each having a retention mechanism (e.g.,  128 ) and an alignment mechanism (e.g.,  130 ), are mechanically coupled  502  to positions adjacent a pattern of points  104  on a PCB  100 . The probe retention devices  120 - 126  may be coupled to the PCB  100  by, for example, clipping, snapping, soldering, screwing, or press fitting them into the PCB  100 . 
   After coupling the probe retention devices  120 - 126  to the PCB  100 , a probe substrate  116  having a plurality of compression interconnects  114  therein may be aligned  504  with the retention devices&#39; alignment mechanisms  130 . The probe substrate  116  may then be mechanically engaged  506  with the retention mechanisms  128 , thereby causing the compression interconnects  114  to seat against the pattern of points  104 . The probe substrate  116  may be engaged with the retention mechanisms  128  by, for example, clipping it to (or press fitting it with) the retention mechanisms  128 . 
     FIGS. 1-4  show one exemplary way of implementing the method  500 . 
   As shown in  FIGS. 1 &amp; 2 , probe retention devices  120 - 126  may be mounted to the PCB  100  in a square or rectangular configuration around a pattern of points  104  to be probed (although other mounting configurations are possible). Note that, as a result of the retention devices  120 - 126  being modular, the retention devices  120 - 126  may be mounted to encompass larger or smaller surface areas of the PCB  100 , and more or fewer points to be probed. The retention devices  120 - 126  therefore provide a scalable probe retention solution. 
   As shown in  FIGS. 6-8 , each probe retention device  120  may generally comprise an L-shaped base  132  of rigid plastic material. The thicknesses of the bases  132  are sized to impart a desired compression to the compression interconnects  114  of a probe  112 . Each base  132  has at least one solder leg  134  molded therein (and preferably two  134 ,  136 ) which extend(s) perpendicularly from the base  132  toward the PCB  100 . Each probe retention device  120  also comprises an alignment mechanism  130  and a retention mechanism  128 , both of which extend from the base  132  of the probe retention device  120  opposite its solder legs  134 ,  136  (i.e. away from the PCB  100 ). In one embodiment, a retention device  120  is manufactured by injection molding its base  132  around its solder legs  134 ,  136 , retention mechanism  128 , and alignment mechanism  130 . 
   As shown in  FIGS. 6-8 , the alignment mechanism  130  of a retention device  120  may comprise a pair of rigid pins  138 ,  140  extending from the base  132 . However, the alignment mechanism  130  could comprise any number of pins (even one). In one embodiment, the pins  138 ,  140  may comprise extensions of a retention device&#39;s solder legs  134 ,  136 . 
   The pins  138 ,  140  of each alignment mechanism  130  mate with corresponding holes  142 ,  144  ( FIG. 9 ) in the corners of the probe substrate  116 . The pins  138 ,  140  provide a fine alignment of the probe  112 , prior to the compression interconnects  114  of the probe  112  coming in contact with the points  104  they are to probe. To first provide a gross alignment of the probe  112  with a pattern of points  104 , the perimeter of the probe substrate  116  may be notched  146 ,  148 ,  150 ,  152  (see  FIG. 9 ). If the retention mechanisms  128  extend farther from the probe substrate  116  than the alignment mechanisms  130 , the notches  146 - 152  in the probe substrate  116  can be configured such that they mate with the surfaces of the retention mechanisms  128  to grossly align the pins  138 ,  140  of the alignment mechanisms  130  with the holes  142 ,  144  in the probe substrate  116 . 
   As illustrated in  FIGS. 6 &amp; 8 , for example, the retention mechanisms  128  may comprise biased clips  154 . Alternatively, other embodiments of the retention mechanisms are possible, such as threaded pins, snap rivets, or any other mechanism suitable for retaining the probe substrate. The retention mechanisms  128  are preferably metallic, but may also be formed of other materials, such as plastic. As best seen in  FIG. 6 , each retention mechanism  128  may comprise a foot  156  that rests against the PCB  100 . The foot  156  is useful in providing support for the retention mechanism  128  so that the retention mechanism does not bend or snap as a result of the forces placed upon it by the compressed interconnects  114  of the probe  112 . 
     FIG. 10  illustrates an alternate probe retention device  158 , wherein the retention and alignment mechanisms of the device  158  are provided by a unitary structure such as a threaded pin  160 . In this manner, the pin aids in aligning a probe  112 , and the threads provide a means for securing the probe  112  (e.g., via a nut). However, although the device  158  provides a reduced part count, it fails to provide a predetermined compression to a probe&#39;s compression interconnects  114  (i.e., because compression is determined by nut tightness). 
   Although the probe retention devices  120 - 126 ,  158  disclosed herein may be provided to a user pre-assembled to a PCB  100 , they are preferably provided to a user in kit form.