Abstract:
A probe for measuring signals with a narrow contact pitch comprises an end section having a main tip member and a sub-tip member, each of which passes through one of two holes in a housing. The sub-tip member is electrically connected to the housing and the main-tip member is insulated from the housing by an insulation member. The sub-tip member is pivotally connected to the housing. The subtip member is asymmetric with respect to the pivot and therefore, its sharpened end can trace a circular orbit when the sub-tip member turns on its pivot. The distance between the two end sections of these tip members (that is, the contact pitch) can be set to a desired length by positioning sub-tip sharpened end section to any point on this orbit.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a probe that is connected to electronic measurement instruments for measuring the signals from each lead of an electronic circuit package and other electronic components mounted on a substrate. More particularly it pertains to a probe for measuring the signals of high-density mounted electronic circuit packages with narrow pitch between their leads with one hand. 
     BACKGROUND OF THE INVENTION 
     FIG. 1 is a conventional one hand held probe for measuring the signals on each lead of electronic circuit packages and other electronic components mounted on a substrate (these are collectively referred to as “DUT” below). Probe  10  has alligator clip  12 , which is coupled to a portion adjacent to a tip section  11  of the probe via cable  13 . By means of this type of probe, one of the leads (for instance, the ground terminal) is clasped and anchored by alligator clip  12  and tip section  11  is brought into contact with another lead. This type of probe is advantageous in that it is possible to keep one lead electrically connected to alligator clip  12 , and therefore the user can quickly introduce tip section  11  to several leads in succession, using one hand. 
     However, it is often impossible to use such a probe to clasp narrow-pitch leads of an electronic circuit package as well as the leads of electronic components mounted on a substrate at high density, therefor such probes can not perform their function in this case. 
     FIG. 2 shows another conventional probe  20 . This probe  20  has sub-tip section  22  next to main tip section  21 . This sub-tip section  22  is attached to the side near the main tip section  21  pivotally on its pivot so that it moves within a plane that includes the axis of the main tip section and the axis of the sub-tip section. Thus, the pointed end of this sub-tip section  22  can move up to and away from the pointed tip of main tip section  21 . This structure is suitable for probing leads with a relatively narrow pitch using one hand. 
     When a probe is used to measure RF signals, coaxial structure must be typically maintained in its axial position that is as close to the measuring point as possible. Therefore, the length of exposed main tip section  21  must be as short as possible in order to maintain this coaxial structure. With a design of short main chip section  21 , however, when trying to move sub-tip section  22  closer to main tip section  21 , sub-chip section  22  bumps against outer surface  23  of the probe before it gets close to main tip section  21 , resulting in that they cannot get close proximity each other. On the other hand, if the main tip section  21  is made longer to prevent the sub-tip section  22  from bumping against the outside surface  23 , in turn, a problem with the coaxial structure will occur. That is, this type of probe is designed taking into consideration whether it is more important to maintain a coaxial structure or to have a pitch that makes narrower pitch probing possible, and the designer must inevitably choose between these two alternatives. The pitch which enables this type of probe to be used for probing is limited to approximately 5 mm, therefor this type of probe is not suitable for probing leads that have a narrower pitch than that. 
     Furthermore, the position of the sub-tip section often changes slightly as the force applied by the user changes during probing, because the end section of the type of probe shown in FIG. 2 is not rigid. Consequently, it is often the case that the measurements are unstable and do not have good reproducibility when this probe is used for measuring microcurrent and high-frequency signals. 
     Consequently, the purpose of the present invention is to present a one hand held probe for probing electronic circuit packages and various electronic components with a pitch that is narrower than the minimum pitch of leads with which the probes of prior art can cover. 
     Another purpose of the present invention is to present a probe for measuring signals that is flexible so that it can be adjusted by the user to any pitch as needed. 
     Yet another purpose of the present invention is to present a probe for measuring signals with high measurement stability and reproducibility. 
     SUMMARY OF THE INVENTION 
     The probe for measuring signals of the present invention comprises a end section that having a housing with a first and a second portions defining holes, a first tip member penetrating the first hole of the housing, and a second tip member, which is placed pivotally in the second hole of the housing so that it can turn on its pivot and is electrically insulated from the first tip member, where one end of the second tip member has a shape that is asymmetric to its pivot. The distance between the pointed end of the first tip member and the pointed end of the second tip member is determined by moving the second tip member to a desired position. 
     The housing of the probe is preferably electrically conductive, where an insulation member is wrapped around the first tip member so that the first tip member is electrically insulated from the housing, and the second tip member is electrically connected to the housing. 
     Furthermore, The probe for signal measurement according to the present invention preferably further comprises a fixation means for fixating the second tip member at a desired rotational position. For example, the fixation means preferably comprises at least one threaded third hole piercing the housing from its outer surface of the housing to the second hole, and at least one fastening knob with a thread engaging the third hole which pushes the second tip member in the second hole when rotated in one direction and moves away from the second tip member when rotated in the other direction. 
     Further, the end section is preferably detachable from the body of the probe. By using a coaxial connector such as an SMA connector as this detachment means, calibration is achieved using a conventional calibration standard. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram of a prior art probe for measuring signals. 
     FIG. 2 is a diagram of a prior art probe for measuring signals. 
     FIG. 3 is a side view showing an embodiment of the end section of the probe of the present invention. 
     FIG. 4 is a top view of the end section of the probe of the present invention, as seen from the direction of arrow A in FIG.  3 . 
     FIG. 5 is a cross-sectional of the end section of the probe of the present invention, as seen from the direction of arrow B in FIG.  3 . 
     FIG. 6 is a diagram for explaining an embodiment of the probe of the present invention. 
     FIG. 7 is a side view of another embodiment of the end section of the probe of the present invention. 
     FIG. 8 is a projection of the end section of a probe of the present invention as seen from the direction of arrow F in FIG.  7 . 
     FIG. 9 is a perspective view showing an embodiment of the end section of the probe of the present invention. 
     FIG. 10 is a perspective view of another embodiment of the end section of the probe of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention considered to be optimal at the present time will be described referring to the figures. The structural elements with the same reference number in the figures have the same function throughout the text. 
     FIG. 3 is a side view of a first embodiment of an end section  30  of the probe of the present invention. FIG. 9 is a perspective view. FIG. 4 is a top view as seen from the direction of arrow A in FIG.  3 . FIG. 5 is a cross-sectional view as seen from the direction of arrow B cutting by a plane including axis  38  perpendicular to the figure plane of FIG.  3 . As shown in FIG. 3, the end section of the probe includes main tip member  31 , sub-tip member  32 , and housing  33 . As shown in FIG. 4, there are two portions defining cylindrical holes  41  and  42  which pass through the housing  33 . The main tip member  31  is inserted into hole  41  and the sub-tip member  32  is inserted into hole  42 . 
     Sub-tip member  32  is electrically conductive and its sharpened end section  34  is sharpened so that it can easily make contact with the leads of the object to be measured. Moreover, the part of sub-tip member  32  that passes through housing  33  has a cylindrical shape that matches hole  42 , therefore it can turn round 360 degrees, as shown in FIG.  4 . This sharpened end section  34  can be positioned at any point on the turning trace ( 45 ), as shown in FIG.  4 . 
     A spring-loaded pin, such as a pogo pin, etc., may be used for sharpened end section  35  of the main tip member  31 . By using the spring-loaded pin, the sharpened end section  35  becomes telescopic in the direction of the arrow C in FIG.  3  and therefore, can be reliably brought into contact with the leads of a DUT during probing. Further, part  37  of sub-tip member  32  next to the main tip member  31  may also be chamfered to be aligned with the shape of the sharpened end section of the main tip member when it is closest to the main tip member, as shown in FIG.  3 . Thus, the distance between the sharpened end section  34  of the sub-tip member and sharpened end section  35  of the main tip member can be reduced to almost the tolerance limit while the rigidity of the sub-tip member is maintained at its maximum limit. Chamfering may be done according to the shape of the main tip member. For example, as shown in FIG. 3, when the size of tip portion  30  is designed so that the distance between center axis  38  of the main tip member  31  and the pivoting axis  39  of the sus-tip member  32  is 7 mm, the shape of the sub-tip member can be designed so that the distance between the sharpened end section  35  of main tip member  31  and the sharpened end section  34  of the sub-tip member  32  can be set to the maximum of 13.5 mm and to the minimum of 0.5 mm. 
     Furthermore, by making housing  33  from an electrical conductor and connecting it to the guard line of the probe body, a probe can be achieved where a coaxial structure is maintained maximally close to the sharpened end of the main tip member, that is, a probing point. In this case, the main tip member  31  must be wrapped with insulation member  36  and electrically insulated from housing  33 , as shown in FIG.  5 . The shape of the part of sub-tip member  32  that is not encapsulated by housing  33  may be a plate-like shape with a predetermined thickness to make the impedance of this part lower than that of a pin shape one. This type of construction is suitable for measurement of high-frequency signals. 
     A variety of connections between end section  30  and the probe body may be considered. The end section  30  may be assembled as one unit with the probe body. The end section may be also detachable from user grip  61 , as shown in FIG.  6 . 
     The end section  30  and the user grip  61  are preferably connected detachably employing a connector structure in order to make the end section  30  detachable. A coaxial connector that meets IEC standard 169-23, such as an SMA connector, etc., may be employed as this connector structure, so that the probe can be used for measuring RF signals. It is also possible to perform the open/short/load calibrations using conventional calibration standards when the coaxial connectors are employed for the connection. Further, since the end section  30  can be easily detached from the probe body, it can be quickly replaced when the end section  30  has been damaged, etc. 
     The cross section shown in FIG. 5 is an embodiment of the aforementioned connector structure employed for the detachable connector between the end section  30  and the probe body. In short, the housing  33 , conductive cylinder  51 , insulation member  36 , and one end  52  of tip member  31  form a typically male SMA connector. The end of user grip  61  forms a typically female SMA connector. An electrical connection is formed by engaging these connectors together. The details of male SMA connectors and method for attaching the female SMA connector to the user grip  61  are well-known to those skilled in the art, therefore will not be discussed here. 
     In order to improve measurement stability and reproducibility, the end section  30  may further comprise a fastening knob  44  to fasten sub-tip member  32  to surface of the hole  42 , as shown in FIG.  4 . In a preferred embodiment of the present invention, the knob  44 , which is threaded to engage with threaded hole  43 , is screwed into the hole  43  that passes from the outside surface of housing  33  to hole  42 . Thus, when the tip member  32  has been turned to be at desired rotational position, the tip member  32  is pressed onto surface of the hole  42  in the forward direction of the knob  44  by screwing the knob  44  into the threaded hole  43 . This arrangement suppresses the fluctuation of the status of electrical contact between the tip member  32  and hole  42 , resulting in stable measurement values, since the tip member  32  is pressed toward the direction of the advance of the fastening knob  44  in the hole  42  and fixated by screwing the fastening knob  44  into the threaded hole  43  after rotating the tip member  32  and positioning it to a desired position. When repeated probing at a certain constant pitch is performed, the above described open/short/load calibration with the sub tip member  32  fixated at a desired position allows measurement of higher repeatability. 
     The fastening knob  44  is inserted into the threaded hole  43  from one direction in FIG. 4, but the number of the knobs is not limited to one. For instance, the fastening knob may be inserted from the directions shown by arrow D and/or arrow E in FIG. 4, and any other direction as long as required rigidity is achieved. Furthermore, a wedge member made from a flexible material may be used to be inserted into a gap between the hole  42  and the sub-tip member  32  used in place of the fastening knob  44 . 
     Next, the present invention will be described with reference to a second embodiment. FIG. 7 is a side view of a second embodiment of an end section  70  of probe of the present invention, FIG. 10 is its perspective view, and FIG. 8 is a projection as seen from the direction of arrow F in FIG.  7 . As shown in FIG. 7, housing  73  has a projection  71 . The projection  71  has a hole  81  by which a sub-tip member  72  is supported slidably thereon. As is clear from FIG. 7, it is possible to set the pitch as needed by sliding the sub-tip member  72  to the right or left. 
     As well as in the first embodiment, threaded hole  43  passes from a side of the projection  71  to hole  81 . A fastening knob  44  which is threaded to engage with the hole  43  is screwed into the hole  43  so that the sub-tip member  72  is pressed onto the inside of the hole  43  and fixed thereon. The same effect as in the first embodiment is obtained by this arrangement, therefore the measurement stability and reproducibility are improved. The advantage of the structure of this embodiment is that since the contact surface between the sub-tip member  72  and the hole  81  is flat, it is larger than the curved surface in the first embodiment. Therefore, the positioning stability of the sub-tip member is improved. Consequently, the end section  70  of this embodiment is more functional as long as there is no problem with its large size. 
     The same structure as in the first embodiment may be used for main tip member  31  in FIG.  7 . In addition, the same chamfering as in the first embodiment is preferably performed on the part of sub-tip member  72  that is next to the main tip member  31 . It goes without saying that the coaxial structure and method for connecting of the probe body and the end section may be the same as in the first embodiment. 
     However, in order to make the range of the possible pitch setting of the second embodiment to be the same as the form of the above mentioned first embodiment, it is needed to design the thickness and the width of sub-tip member  72  of the second embodiment to be slightly larger than those of sub-tip member  32  of the first embodiment. This is because the amount of the distortion at sharpened end  74  of the sub-tip member  72  when the pitch is set to be the shortest is larger than that of the first embodiment due to the nature of a plate member that its distortion is generally proportional to the cube of the distance from its supporting point, and the amount of the distance between tip  74  and the fulcrum (projection  71 ) is, different from the first embodiment, varies according to the pitch setting. As is understood from this, when maximum stiffness and stability are required as well as small dimensions that allow easy probing, the end section  30  of the first embodiment may be considered to have the optimal shape. 
     The present invention has been explained in detail with preferred embodiments, but it is clear that the embodiments can be changed and modified as long as they do not deviate from the spirit of the present invention. Consequently, the scope of the present invention is limited only by the claims hereof.