Abstract:
Adapters for electrostatic discharge probe tips are disclosed herein. An embodiment of the adapter includes an attachment device that is attachable to the tip of the probe. A first conductor is affixed to the attachment device so that the first conductor contacts the tip when the attachment device is attached to the tip of the probe. A second conductor extends between the first electrical conductor and a point external to the attachment device.

Description:
BACKGROUND 
       [0001]    Many electronic devices are susceptible to failure when they are subjected to an electrostatic discharge (ESD). The ESD is a high voltage pulse that is typically short in duration. When an electronic device receives an ESD, the energy of the discharge may destroy or degrade electronic components within the electronic device. 
         [0002]    The effects of ESD are very unpredictable. Testing an electronic device for susceptibility to ESD involves subjecting a sample of the electronic device to simulated ESD pulses and then testing the electronic device to determine whether it has failed. The testing involves two steps. The first step involves connecting an ESD simulator to the electronic device and subjecting the electronic device to a simulated ESD pulse. The ESD simulator is then disconnected from the electronic device and test equipment is connected to the electronic device. The electronic device is then tested to determine whether it has failed, which determines whether the device can withstand ESD. 
         [0003]    Connecting both the ESD simulator and the test equipment simultaneously to the electronic device presents several problems. One problem is that the simulated ESD pulse generated by the ESD simulator may damage the test equipment. Another problem is that the simulated ESD pulse is a very short, but high voltage signal. As such, it is very susceptible to loading that may occur by being connected to the test equipment. For example, internal capacitance in the test equipment or the leads of the test equipment may dampen the simulated ESD pulse to a point where the electronic device is not being subjected to the correct simulated ESD pulse. 
         [0004]    Therefore, a need exists for simpler methods and devices for testing electronic devices. The methods and devices need to be quick, provide accurate simulated ESD pulses to the electronic devices, and leave the test equipment undamaged. 
       SUMMARY 
       [0005]    Adapters for electrostatic discharge probe tips are disclosed herein. An embodiment of the adapter includes an attachment device that is attachable to the tip of the probe. A first conductor is affixed to the attachment device so that the first conductor contacts the tip when the attachment device is attached to the tip. A second conductor extends between the first electrical conductor and a point external to the attachment device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is an embodiment of a schematic diagram of a test system to determine whether a device under test can withstand ESD. 
           [0007]      FIG. 2  is an enlarged schematic diagram of the test probe of  FIG. 1 . 
           [0008]      FIG. 3  is a cross sectional side view of an attachment mechanism of the test probe of  FIG. 2 . 
           [0009]      FIG. 4  is a flow chart describing an embodiment of the operation of the test system  100  of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    A system  100  for testing a device under test  104  is shown in  FIG. 1 . In the embodiment of  FIG. 1 , the device under test  104  is an integrated circuit. However, the device under test  104  is not limited to integrated circuits and may be any electronic device. An ESD probe  106  is electrically contactable with a lead  108  of the device under test  104 . An ESD simulator  110  is connected to the ESD probe  106  by way of a line  114 . In some embodiments, the ESD simulator  110  and the ESD probe  106  are a single device, such as a hand-held device. In such devices, there is no line  114 . The ESD simulator  110  generates an electrical signal that simulates an electrostatic discharge. For example, the ESD simulator may generate a simulated ESD pulse of a few thousand volts that has a duration of a few nanoseconds. The simulated ESD pulse is transmitted to the device under test  104  by way of the probe  106 . 
         [0011]    Test equipment  120  is electrically connectable to the probe  106  by way of a line  122 , a relay  124 , and another line  126 . The relay  124  has an open state wherein the test equipment  120  is not electrically connected to the probe  106  and a closed state wherein the test equipment  120  is electrically connected to the probe  106 . The relay  124  may be a switch that electrically connects and disconnects the test equipment  120  from the probe  106 . The line  122  may be relatively short in order to electrically locate the relay  124  close to the probe  106 . In doing so, the impedance of the line  122  will likely have little effect on the simulated ESD pulse emitted by the probe  106 . 
         [0012]    The test equipment  120  is used to test the functionality of the device under test  104 . For example, the test equipment  120  may test the device under test  104  before and after the device under test  104  has been subjected to a simulated ESD pulse. In some embodiments, the test equipment  120  includes, oscilloscopes, spectrum analyzers, voltmeters, and ohmmeters. The test equipment  120  may only test the functionality of the device under test  104  related to the lead  108  to which the probe  106  is connected. Therefore, after the device under test  104  has been subjected to the simulated ESD pulse, the test equipment  120  may test the device under test  104  to make sure circuits connected to the lead  108  are functioning correctly. In other embodiments, the test equipment  120  may test more than just the components connected to the lead  108 . In such embodiments, the simulated ESD pulse may cause damage to other circuits while the circuits tested on the lead  108  appear to function properly. Thus, the extended testing provided by the test equipment  120  may provide a complete test of the device under test  104 . 
         [0013]    A controller  130  is connected to the relay  124  by way of a line  132 . The relay  124  has an open state wherein the line  122  is not connected to the line  126  and a closed state wherein the line  122  is connected to the line  126 . In the embodiment of  FIG. 1 , the controller  130  controls the state of the relay  124 . A voltage output to the relay  124  on the line  132  may cause the relay  124  to close and no voltage on the line  132  may cause the relay  124  to open. The controller  130  may also be connected to the test equipment  120  by a line  134  and the ESD simulator  110  by a line  136 . As described in greater detail below, in some embodiments, the controller  130  may operate both the ESD simulator  110  and the test equipment  120 . For example, the controller  130  may open the relay  124  when the ESD simulator  110  is active in order to prevent the test equipment  120  from being damaged or loading the simulated ESD pulse. 
         [0014]    Having described the test system  100 , the probe  106  will now be described in greater detail. An enlarged view of the probe  106  is shown in  FIG. 2 . The probe  106  includes a conductive tip  140  that ends with a point  142 . The point  142  is configured to contact specific electronic devices. For example, the point  142  of  FIG. 2  is somewhat sharp and is able to contact the lead  108  on the device under test  104 ,  FIG. 1 . The tip  140  is attached to a holder  144 . The holder  144  may be made of an insulating material so that a user may hold the holder  144  while operating the probe  106 . The tip  140  and the holder  144  may be of the type used in conventional ESD simulator devices. 
         [0015]    The probe  106  includes a novel adapter  150  that contacts the tip  140 . A cross sectional side view of the adapter  150  is shown in  FIG. 3 . The adapter  150  shown herein is made to fit over the tip of an existing probe, so there are no modifications that need to be made to a conventional ESD simulator in order to make the probe  106 , other than adding the adapter  150  to the tip  140 . 
         [0016]    The adapter  150  includes an attachment device  152  that at least partially contacts the tip  140 . The attachment device  152  has an inner surface  154  and an outer surface  156 , wherein at least a portion of the inner surface  154  is adapted to contact the tip  140 . A conductor  158 , sometimes referred to as a first conductor, is located proximate the inner surface  154  so that it electrically contacts the tip  140  when the adapter  150  is located on the tip  140 . The conductor  158  may have a shape that at least partially matches the outer surface of the tip  140  in order to form an electrical connection between the tip  140  and the conductor  158 . 
         [0017]    A line  160 , sometimes referred to as a second conductor, electrically connects the conductor  158  to a point external to the attachment device  152 , which in  FIG. 3  is the line  122 . It is noted that the first conductor  158  and the second conductor  160  are described as being separate components. However, it is to be understood that the first and second conductors  158 ,  160  may be a single conductor. A filter  164  may be connected to the line  160  in order to isolate the test equipment  120 ,  FIG. 1 , from the simulated ESD pulse. In the embodiment of  FIG. 3 , the filter  164  is a resistor that is connected in series with the line  160  so as to provide a resistance between the conductor  158  and the line  122 . The resistor serves to filter or isolate the probe  106  from impedances associated with the adapter  150  and wires and devices connected to the adapter  150 . The resistance within the device under test  104  when measured from the lead  108  may only be a few ohms. Therefore, a resistor  164  having a value of a few kilohms will typically suffice in preventing the adapter  150  from interfering with the simulated ESD pulse emitted by the tip  140 . 
         [0018]    The attachment device  152  may be made of an elastic material, such as a foam material. The attachment device  152  may also be C-shaped and may have an opening  153 . The elastic material, along with the C-shape, enables the attachment device  152  to expand around the tip  140  and to fit snug against the tip  140 . Accordingly, the attachment device  152  may be retained against the tip  140  by frictional forces between the attachment device  152  and the tip  140 . The material of the attachment device  152  may be electrically insulating. The insulating material will cause fewer effects on the simulated ESD pulse that is emitted by the tip  140  than conductive materials. The use of an insulating material for the attachment device  152  also reduces the likelihood of a user being shocked while using the probe  106 . 
         [0019]    In some embodiments, the attachment device  152  may have a clamp  168  that further secures the attachment device  152  to the tip  140 . The clamp  168  may be more rigid than the attachment device  152  and serves to further secure the attachment device  152  to the tip  140 . The clamp  168  may be made of flexible material, such as plastic, and, like the attachment device  152 , may be C-shaped. 
         [0020]    The operation of the test system  100  will be described with additional reference to the flow chart  200  of  FIG. 4 . The testing process commences with attaching the adapter  150  to the tip  140  of the probe  106  as described in step  202 . The attachment device  152  may be expanded to fit over the tip  140  and secured in place with the clamp  168 . The probe  106  may be a conventional probe used in ESD simulators, except for the addition of the adapter  150 . At step  204 , the tip  140  electrically contacts the lead  108  of the device under test  104 . At this time, the controller  130  may close the relay  124  and prevent the ESD simulator  110  from emitting a simulated ESD pulse to the probe  106  as described at step  206 . Accordingly, the test equipment  120  is electrically connected to the lead  108  of the device under test  104 . 
         [0021]    The controller  130  may initiate a preliminary test on the device under test  104  at step  208  to determine if the device under test  104  is functioning properly before commencing an ESD test. If the device under test  104  is not working properly, there is no need to perform the ESD test. 
         [0022]    If the controller  130  determines that the device under test  104  is functioning properly, it will commence the ESD test. The ESD test commences with opening the relay  124  as shown at step  210 . For example, the controller  130  may send a signal to the relay  124  causing it to open. Opening the relay  124  disconnects the test equipment  120  from the probe  106 . Therefore, the test equipment will not affect the simulated ESD pulse. At step  212 , the ESD simulator  110  generates a simulated ESD pulse that is transmitted to the lead  108  on the device under test  104  by way of the probe  106 . For example, the controller  130  may send a signal to the ESD simulator  110  causing the ESD simulator  110  to generate a specific simulated ESD pulse. 
         [0023]    At this point in the testing, the device under test  104  has been subjected to a simulated ESD pulse. The device under test  104  needs to be tested to make sure that it continues to function properly after being subjected to the simulated ESD pulse. At step  214 , the relay is closed so that the lead  108  on the device under test  104  is connected to the test equipment  120 . The controller  130  may send a signal to the relay  124  that causes the relay  124  to close. The test equipment  120  now tests the device under test  104  as described at step  216 . The controller  130  may send a signal to the test equipment  120  causing it to perform specific tests on the device under test  104 . The controller  130  can analyze the test results to determine if the device under test  104  is functioning properly after being subjected to the simulated ESD pulse. 
         [0024]    The test system  100  has been described above using the controller  130 . In some embodiments, the controller  100  is not required and a user of the test system  100  may manually perform the tests. For example, the user may open or close the relay  124 . Likewise, the user may initiate tests using the test equipment  120  and may cause the ESD simulator  110  to generate the simulated ESD pulse. 
         [0025]    While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.