Abstract:
A signal probe includes a tip assembly having a first tip for contacting a first signal node, a second tip for contacting a second signal node, and a tip body for positioning the first tip a distance away from the second tip, the distance corresponding to the spacing between the first and second signal nodes. With the tip body, a technician no longer has to couple a wire between one of the signal nodes and a respective tip to probe the electronic device. Thus, the length of the path that a signal travels from the first signal node to the second signal node may be reduced to increase the accuracy of the signal&#39;s measurement.

Description:
BACKGROUND  
         [0001]    Many electronic devices, such as computers, include a circuit board that contains the device&#39;s circuitry and/or components for operating the device. The circuit board typically includes many electrical circuits and at least one component such as a processor, power supply or memory chip mounted to it. When electronic devices malfunction or when the design or manufacture of the device is not complete, a technician typically tests/diagnosis the device by probing the nodes of the device&#39;s circuit board with a probe coupled to a measuring device, such as an oscilloscope.  
           [0002]    Many of the tests/diagnosis require a technician to measure high-frequency signals generated in a circuit and/or component of the device. To probe a device&#39;s circuit board to measure high-frequency signals, a technician typically contacts a short signal lead of an active probe, i.e., a probe having circuitry within the probe body, to a pad or other accessible contact of the signal node. In addition, the technician typically contacts a second conductive lead of the probe to a ground of the circuit board, which may be located anywhere on the circuit board, to ground the probe. Furthermore, to accurately measure high-frequency signals, the leads of the probe must typically remain in contact with the signal nodes. Thus, probing an electronic device typically requires the technician to use one of his/her hands to support the probe and keep the probe still.  
           [0003]    For example, FIG. 1 shows a conventional active probe  10  for probing a component (omitted for clarity) of a circuit board  12 . The probe  10  includes a body  14  having circuitry (omitted for clarity) to measure or condition a high-frequency signal, a signal tip  16  to convey the high-frequency signal to the circuitry, and a ground tip  18  for grounding the probe  12  and providing a return path for the measured signal. The circuit board  12  includes an array of pads  20 , the array including a signal pad  22  and a ground pad  24 . For example, the array  20  is a conventional ball-grid array (BGA) with spacing between adjacent pads in the X and Y directions equal to 0.040 inches. The signal tip  16  may be soldered to the signal pad  22  to maintain contact between the signal tip and the pad  22 . Because the spacing between the signal tip  16  and the ground tip  18  is typically greater than the spacing between the pads  22  and  24 , a wire  30  is typically soldered to the tip  18  and the ground pad  24  to couple the ground tip to the pad  24 . While measuring a high-frequency signal, the signal travels from the pad  22 , through the signal tip  16 , and through the ground tip  18  and wire  30  to the ground pad  24 .  
           [0004]    To accurately measure a high-frequency signal, the tip  16  should remain in contact with the pad  22 , and the length of the path that the signal travels from the signal pad  22 , through the tips  16  and  18  and wire to the ground pad  24  should be minimized. If contact is not maintained, the signal sensed by the probe may be degraded or lost. Reducing the path length of the signal reduces noise in the signal that can be picked up from other components and/or circuits in the circuit board  12  or elsewhere, and that can adversely affect the fidelity of the high-frequency signal received by the probe.  
           [0005]    Unfortunately, accurate high-frequency measurements are sometimes difficult to make with the probe  10 . The length of the path that the high-frequency signal travels from the signal node  22  to the ground node  24  includes the length of the wire  30 . Frequently, this additional length is enough to corrupt the high-frequency signal being measured.  
           [0006]    Furthermore, soldering the point  26  of the signal tip  16  to the pad  22  often does not effectively support the probe  10 . For example the probe body  14  can easily tip and break the solder joint if a technician does not hold the probe  10  still. Thus, the technician often has to hold the probe  10  still with his/her hand to probe the circuit board  12 , even though the tip  16  may be soldered to the pad  22 .  
           [0007]    Holding the probe with a hand while testing/diagnosing an electronic device is often clumsy and awkward. Frequently, testing/diagnosing requires a technician to probe a circuit and/or component for long periods of time, and thus often requires the technician to hold the probe for a long period of time to complete the test/diagnosis. Holding the probe for a long period frequently tires the technician&#39;s hand, wrist and/or arm, which can cause the technician to allow the probe body to move and thus break the connection between the probe&#39;s lead and the signal node. In addition, testing/diagnosing an electronic device frequently requires a technician to operate the controls of the measuring device (oscilloscope) while probing the circuit and/or component. This often causes the technician to lose his/her concentration on maintaining contact between the probe and the signal node of the component.  
         SUMMARY  
         [0008]    In one aspect of the invention, a signal probe includes a tip assembly having a first tip for contacting a first signal node, a second tip for contacting a second signal node, and a tip body for positioning the first tip a distance away from the second tip, the distance corresponding to the spacing between the first and second signal nodes. With the tip body, a technician no longer has to couple a wire between one of the signal nodes and a respective tip to probe the electronic device. Thus, the length of the path that a signal travels from the first signal node to the second signal node may be reduced to increase the accuracy of the signal&#39;s measurement.  
           [0009]    In addition, one or both of the tips may include a base that may be attached to a signal node to secure the tip to the signal node. With the base, a technician can support the signal probe while probing an electronic device without having to hold the probe still to maintain contact between the tip and the signal node. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0010]    [0010]FIG. 1 is a perspective view of a conventional probe-tip assembly having signal and ground tips coupled to two signal nodes of a circuit board.  
         [0011]    [0011]FIG. 2 is a perspective view of a probe-tip assembly having signal and ground tips attached to respective pads of a circuit board according to an embodiment of the invention.  
         [0012]    [0012]FIG. 3 is a perspective, partial view of a tip of FIG. 2 coupled to a pad of the circuit board in FIG. 2, according to an embodiment of the invention.  
         [0013]    [0013]FIG. 4 is a view of a probe having a probe-tip assembly according to another embodiment of the invention.  
         [0014]    [0014]FIG. 5 is a perspective view of a probe having a probe-tip assembly according to yet another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0015]    The following discussion is presented to enable one skilled in the art to make and use the invention. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.  
         [0016]    [0016]FIG. 2 is a perspective view of a circuit board  40  incorporated in an electronic device (omitted for clarity), and a probe  42  having a probe-tip assembly  44 , according to an embodiment of the invention. As discussed below, the probe  42  is secured to two pads  46  and  48  of a pad array  50 , which allows a technician to probe one or more signal nodes of a circuit (not shown) and/or component (not shown) of the circuit board  40  without holding the probe. The probe  42  receives an electrical signal, which is typically a high-frequency signal but may be another type of signal, via the pads  46  and  48 , and the cable  52  couples the probe  42  to an oscilloscope (not shown) or other electronic device that receives the probed signal. The probe  42  may be an active probe, that includes circuitry (not shown) within the probe body  54  for measuring high-frequency signals, or may also be a passive probe. With the probe-tip assembly  44 , a technician can secure the probe  42  to two signal nodes while reducing the length of the path the probed signal travels to and from the probe body  54 , and thus reduce noise that may corrupt the measurement of the probed signal.  
         [0017]    The probe-tip assembly  44  includes a signal tip  56  for contacting the pad  48 , and a ground tip  58  for contacting the pad  46 . The signal tip  56  may include a resistor  57  to reduce noise caused by signal ringing if the probe  42  is an active probe, or to increase the impedance of the probe  42  if the probe  42  is a passive probe. In other embodiments, another component such as a capacitor (not shown) may take the place of the resistor  57 , or the resistor  57  and component may be omitted. The probe-tip assembly  44  also includes a tip body  60  to fixedly or adjustably position the tip  56  a distance away from the tip  58 , the distance corresponding to the spacing between the pads  46  and  48 . The pad array  50  includes the pads  46 ,  48 , and  62  that are each spaced a distance apart from adjacent pads in the array  50  in the X and Y directions. The distance that each pad  46 ,  48  and  62  is spaced apart from an adjacent pad in the X and Y directions can vary within an array or relative to different arrays. For example, the pad array  50  may be a ball grid array (BGA) of pads or a land grid array (LGA) of pads having each pad spaced approximately 0.040 inches apart in the X and/or Y direction, or approximately 0.050 inches apart in the X and/or Y directions. Thus, in one embodiment of the probe-tip assembly  44 , the tip body  60  may position the tip  56  approximately 0.040 inches away from the tip  58  to provide a relatively short path for the probed signal to travel. And, in another embodiment of the probe-tip assembly  44 , the tip body  60  may position the tip  56  approximately 0.050 inches away from the tip  58 . And, if the probed pads in a pad array  50  with 0.040 or 0.050 spacing are located diagonally adjacent each other the tip body  60  may fixedly or adjustably position the tip  56  0.040{square root}{square root over (2)} inches or 0.050{square root}{square root over (2)} inches away from the tip  58 .  
         [0018]    The tip body  60  may be made of any desirable material and the tips  56  and  58  may be anchored to the body  60  using any desirable technique. For example, the tip body  60  may be made of any non-conductive plastic material to insulate both tips  56  and  58  from each other. Furthermore, the tip body  60  may be formed around the tips  56  and  58  using conventional injection molding techniques. In other embodiments, the tip body  60  may be made of conventional rubber and the tips  56  and  58  may be mounted to the outside of the tip body  60  using conventional fastening techniques.  
         [0019]    Other embodiments of the tip body  60  are contemplated. For example, the tip body  60  may include an adjustment mechanism that allows a technician to change the distance between the tips  56  and  58 , respectively. This may be desirable when the technician is browsing, i.e., probing a circuit and/or component for a short period of time and then probing another, and the different circuits and/or components being browsed have different pad spacings or, this may be desireable when probing pads that are laterally and distinctly spaced.  
         [0020]    Still referring to FIG. 2, the tips  56  and  58  each include a respective extension  63  and  65  to which a respective flat base  64  and  66  are attached, and may be made of any desirable conductive material such as steel according to an embodiment of the invention. Each base  64  and  66  may be fastened to the respective one of the pads  48  and  46  using any desired fastening technique to secure the tip of  56  and  58  to the circuit board  40 . As shown in FIG. 2, the base  66  of the tip  58  is similar to the base  64  of the tip  56 , and thus the following discussion of the base  66  also applies to the base  64 . As shown in FIGS. 2 and 3, in one embodiment, the base  66  is a substantially circular disc  68  having a perimeter  70  and a substantially flat surface (not shown) that forms an interface with the pad  46  when the base  66  is fastened to the pad  46 . In one embodiment, to fasten the base  66  to the pad  46 , a bead of solder  72  (shown in FIG. 3 only) may be melted and then allowed to harden in contact with the perimeter  70  and pad  46 . By fastening the base  66  to the pad  46  at the perimeter  70  and not beneath where the extension  65  is attached to the base  66 , the attachment of the ground tip  58  to the pad  46  can better resist movement of the probe  42  relative to the pad  46  that would normally cause the tip  58  to separate from the pad  46 . And thus, a technician does not have to hold the probe to maintain electrical contact between the tip  58  and the pad  46 .  
         [0021]    Other embodiments of the base  66  and different techniques for fastening the base  66  to the pad  46  are contemplated. For example, the base may have another shape, such as that of a square disc or shaped like a tear drop, and the base may be fastened to the pad  46  using any conductive adhesive.  
         [0022]    Still referring to FIG. 2, the probe-tip assembly  44  may be attached to the probe body  54  using any desired technique. Furthermore, the probe-tip assembly  44  may be removable and replaceable from the probe body  54 . This may be desirable when probing different circuits and/or components of a circuit board that have corresponding pads spaced different distances apart. In one embodiment, the probe body  54  includes a clamp (not shown) that frictionally holds the tips  56  and  58  to the probe body  54 . To attach the tips  56  and  58 , an end (not shown) of each lead  56  and  58  is inserted through one of the two openings  74  and  76  of the probe body  54  and into a jaw (not shown) of the clamp. The clamp may include a spring (not shown) to bias the jaws in a closed position such that, when the ends of the leads  56  and  58  are inserted into the jaw, the jaw exerts pressure against the ends to hold the leads  56  and  58 .  
         [0023]    Other fastening techniques are contemplated. For example, the probe-tip assembly  44  may be attached to a coaxial cable with a subminiature version A connector (SMA connector). This may be desirable when other electronic devices that include coaxial cable to receive a probed signal are used. Or, the probe-tip assembly  44  may be attached to a coaxial cable with a Bayonet Neill Concelman connector (BNC connector). This may be desirable to quickly connect and disconnect the tip assembly  44  from the coaxial cable.  
         [0024]    [0024]FIG. 4 is a view of a probe  78  that includes a probe-tip assembly  80  according to another embodiment of the invention. The probe-tip assembly  80  includes tips  82  and  84 , each having a respective point  86  and  88 , that have approximately the pad spacing shown and discussed in conjunction with FIG. 2 and that may be retracted toward the probe body  89  relative to the respective one of the tips  82  and  84 . Furthermore, each of the points  86  and  88  may be biased away from the probe body  89  of the probe  78 . The probe-tip assembly  80  may be desirable for browsing different circuits and/or components of an electronic device, because attaching the bases  64  and  66  of the tips  56  and  58  in FIGS. 2 and 3 to many different pads might require significant time and effort, and thus may be inefficient for browsing.  
         [0025]    In one embodiment, the tip  84  includes a resistor  85  to reduce noise caused by signal ringing if the probe  78  is an active probe, or to increase the impedance of the probe  78  if the probe  78  is a passive probe. Furthermore, the tips  82  and  84  each include a tip body  90  and  92 , respectively, and a spring (not shown) disposed in each of the lead bodies  90  and  92  to bias the points  86  and  88  away from the probe body  89 . Each spring may be fastened to the respective one of the lead bodies  90  and  92  and fastened to the respective one of the points  86  and  88  such that each spring is disposed between the respective one of the bodies  90  and  92  and the respective one of the points  86  and  88 . When a technician exerts pressure on the probe  78  after contacting the pads  46  and  48  (FIG. 3) with the points  86  and  88 , the points  86  and  88  slide within the respective one of the bodies  90  and  92 .  
         [0026]    Other embodiments of the probe  78  are contemplated. For example, the tips  82  and  84  may be retractable relative to the probe body  89 .  
         [0027]    [0027]FIG. 5 is a perspective view of a probe  98  that includes a probe-tip assembly  100  according to yet another embodiment of the invention. The probe-tip assembly  100  is similar to the probe-tip assembly  44  in FIG. 2 except that the tips  102  and  104  are configured to angularly position the probe-tip assembly  100  relative to the probe body  106 .  
         [0028]    In one embodiment, the signal tip  104  includes a resistor  108  to reduce noise caused by signal ringing if the probe  98  is an active probe, or to increase the impedance of the probe  98  if the probe  98  is a passive probe. In addition, the signal and ground tips  102  and  104  are rigid and bent substantially 90° to allow a technician to probe a circuit and/or component of an electronic device that may be difficult to access and probe with the probe  42  (FIG. 2). Furthermore, a technician can probe a circuit and/or component of an electronic device without having to hold the probe body  106  to support the probe  98 . The probe-tip assembly  100  may be fastened to respective pads  46  and  48  as discussed above in conjunction with FIGS. 2 and 3, and the probe body  106  may be supported by blocks (not shown) resting on the circuit board  40  (FIG. 2).  
         [0029]    Other embodiments of the probe-tip assembly  100  are contemplated. For example, the bent angle of the probe-tip assembly  100  may be positionable tip as discussed in U.S. patent application Ser. No. ______ (attorney docket No. 1964-28-3) titled ELECTRONIC PROBE WITH POSITIONABLE TIP and filed 16 Apr. 2003, which is incorporated by reference.