Abstract:
A TDR testing method comprises storing test data resulted from a TDR test applied on an electronic component, displaying the test data, identifying a distinctive portion of the test data corresponding to a defective location in the electronic component, modifying the distinctive portion of the test data, and computing the modified test data to verify whether a predetermined requirement is satisfied.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to testing of electronic devices, and more particularly a system and method for time domain reflectometry testing. 
         [0003]    2. Description of the Related Art 
         [0004]    Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. 
         [0005]    Computer electronic components usually have to undergo a number of testing steps to ensure that they perform correctly. The time domain reflectometry (“TDR”) technique is one well-known testing method that is applied to characterize and locate faults in a conductive path of an electronic device. In this technique, a time domain reflectometer applies an input signal that is transmitted along a conductor in a device under test, and then detects a resulting reflection signal returned from the tested device. The reflection signal is a signal in function of time that is indicative of any discontinuities in the conductor impedance. To evaluate whether the device passes a requisite compliance test in the frequency domain, the detected signal is converted into frequency spectrum data, also called the return loss data, which are then compared against a predetermined level. 
         [0006]    To illustrate,  FIG. 1A  is a simplified diagram of a conventional TDR testing setup  100 . The testing setup  100  includes a TDR testing machine  110  that is coupled to a device under test  102  mounted on a printed circuit board (“PCB”)  104 . The tested device  102  may include any computer electronic devices, such as a central processing unit, a graphics processing unit, chipset units, and the like. The testing machine  110  may be coupled to the tested device  102  via a suitable connector interface  106  provided for the tested device  102 . 
         [0007]    During testing, an end terminal  112  of the testing machine  110  applies an electric pulse signal that is transmitted to the tested device  102 . Any impedance discontinuities along the transmission path of the inputted electric pulse signal will create echoes in a reflection signal returned by the tested device  102  and detected at the end terminal  112  of the testing machine  110 .  FIG. 1B  is a schematic graph illustrating a graphic representation  120  of a reflection signal that may be measured at the end terminal  112 . To determine whether the tested device  102  meets a standard requirement, the returned reflection signal is converted into return loss data, which are then compared against a predetermined threshold reference.  FIG. 1C  is a schematic graph illustrating corresponding return loss data  122  that are computed and compared against a threshold reference  124 . If the return loss data  122  are entirely below the threshold reference  124 , the tested device  102  complies with the standard requirement. Otherwise, the test has failed, and correction in the physical structure of the tested device  102  is needed. 
         [0008]    While the aforementioned testing flow allows to generally determine the presence of defective conductor portions, it however fails to provide information helpful to the correction operation of the failed device  102 . Even though the positions of certain distinctive peaks in the reflection signal  120  may be used to identify the defective portions that need reworking, another TDR test is still needed after the rework operation to ensure that all defects have been addressed. As a result, it is possible that multiple TDR testing and correction operations are needed before the tested device  102  successfully passes the compliance test, which increase the verification time and the labor cost as each correction requires a physical modification of the device  102 . 
         [0009]    Therefore, what is needed is an TDR testing system and method capable of providing information that will help in the correction operation of failed devices, and address at least the problems set forth above. 
       SUMMARY OF THE INVENTION 
       [0010]    In one embodiment, the present application describes a TDR testing method. The method comprises storing test data resulted from a TDR test applied on an electronic component, displaying the test data, identifying a distinctive portion of the test data corresponding to a defective location in the electronic component, modifying the distinctive portion of the test data, and computing the modified test data to verify whether a predetermined requirement is satisfied. 
         [0011]    In another embodiment, a TDR testing computer system is disclosed. The system comprises a memory for storing test data resulted from a TDR test applied on an electronic component, a display device, an input device, and a processing unit configured to selectively modify a distinctive portion of the test data identified as corresponding to a defective location in the electronic component, and compute the modified test data to verify whether a predetermined requirement is satisfied. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0013]      FIG. 1A  is a simplified diagram of a conventional TDR testing setup; 
           [0014]      FIG. 1B  is a schematic graph illustrating typical test data of a reflection signal detected in a TDR testing machine; 
           [0015]      FIG. 1C  is a schematic graph illustrating how test data are conventionally computed and evaluated to meet a standard requirement; 
           [0016]      FIG. 2A  is a schematic diagram of a testing system implementing one or more aspects of the present invention; 
           [0017]      FIG. 2B  is a schematic graph illustrating an example of how TDR test data may be modified according to an embodiment of the present invention; 
           [0018]      FIG. 2C  is a schematic graph illustrating examples of return loss data respectively derived from original and modified test data according to an embodiment of the present invention; and 
           [0019]      FIG. 3  is a flowchart of method steps performed in a TDR testing process according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    One embodiment of the invention may be implemented as a program product for use with a computer system. The program(s) of the program product define functions of the embodiments (including the methods described herein) and can be contained on a variety of computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. 
         [0021]      FIG. 2A  is a schematic diagram of a testing system  200  implementing one or more aspects of the present invention. The testing system  200  includes a computer device  202  that may be coupled to a testing machine  204 . The computer device  202  includes a processing unit  206  that is coupled to a memory  208 , a system interface  210 , an input device  212 , and a display device  214 . The memory  208  typically includes dynamic random access memory (DRAM) configured to connect to the processing unit  206 . The processing unit  206  is adapted to execute programming codes of a testing application  216  stored in the memory  208 , operates on TDR test data  218  stored in the memory  208 , and may communicate with the input device  212 , the display device  214  and the testing machine  204  through the system interface  210 . 
         [0022]    The system interface  210  may include a system bus, a memory controller, universal serial bus, and other interfaces necessary to establish communication links between the processing unit  206  and the input device  212 , display device  214  and testing machine  204 . The input device  212  may include a keyboard, a pointer mouse, and any devices enabling user&#39;s inputs during the execution of the testing application  216 . The display device  214  is an output device capable of emitting a visual image corresponding to an input data signal. For example, the display device may be built using a cathode ray tube (CRT) monitor, a liquid crystal display, or any other suitable display system. 
         [0023]    The testing machine  204  is operable to perform TDR testing on an electronic device (not shown). The test results obtained by the testing machine  204 , which include sampled values of the time reflection signal, may be directly transferred through the system interface  210  to be stored as test data  218  into the memory  208 . In alternate embodiments, the test data  218  provided by the testing machine  204  may be initially stored in a remote storage device (not shown), and then loaded into the memory  208  for execution of the testing application  216 . 
         [0024]    The processing unit  206  executes the testing application  216  to display the test data  218  in a visual form on the display device  214 , such that the user is able to modify and change portions of the test data  218  thanks to a user interface  220  incorporated in the testing application  216 . The user interface  220  may include a graphic user interface. As a result, the user is able to desirably simulate at least a portion of the test data  218  corresponding to the reflection signal. Furthermore, the testing application  216  is configured to cause the processing unit  206  to operate on the test data  218  to derive return loss data, and then evaluate whether the return loss data satisfy a standard requirement in a compliance test. 
         [0025]    In conjunction with  FIG. 2A ,  FIG. 2B  and  FIG. 2C  are schematic graphs illustrating how the test data  218  may be modified according to an embodiment of the present invention. Referring to  FIG. 2B , the test data  218  may be visualized on the display device  214  in the form of a graphic representation  230  that plots the reflection signal in function of time. As shown in  FIG. 2C , to verify whether the standard requirement is met, return loss data  242  in function of frequency are derived from the test data  218  and then compared against a predetermined threshold reference  240 . When a portion  241  of the return loss data  242  exceeds the threshold reference  240 , the compliance test has failed, indicating the presence of defects. Defective locations in the tested device may be identified based on the position of certain distinctive portions of the graphic representation  230  including, without limitation, a peak, a dip, a resonance, or a level shift from the required value. For the purpose of illustration, suppose that one identified defective location corresponds to a dip region  232 . By using the input device  212 , the user is able to manually modify a value V 1  of the dip region  232  to another value V 0  that simulates an expected test result which may be obtained after the application of a virtual correction operation on the identified defective location. In an example of implementation, the manual modification of the test data  218  may be made by selecting the value V 1  in the dip region  232  with a selector icon  234 , and then entering or displacing the selector icon  234  to the desired value V 0 . In this manner, the dip region  232  of the test data  218  may be changed to a simulated test result portion  236 . Based on the modified test data  218 , simulated return loss data  244  are computed and evaluated again against the threshold reference  240 , as shown in  FIG. 2C . The standard requirement is met when the computed return loss data are entirely below the threshold reference  240 , such as shown for the simulated return loss data  244 . 
         [0026]    By enabling a manual modification of the test data  218 , the testing system  200  is thus able to simulate return loss data obtained for a virtual test device in which the identified defective portions would have been modified. If the simulated return loss data satisfy the standard requirement of the compliance test, it means that all the defective portions have been identified and the correction operation then can actually take place in an efficient manner. 
         [0027]    In conjunction with  FIGS. 2A-2C ,  FIG. 3  is a flowchart of method steps performed in a TDR testing process according to one embodiment of the present invention. In initial step  302 , an electronic device is tested in the TDR testing machine  204 , which accordingly provide TDR test data  218  corresponding to sampled values of the reflection signal returned by the tested device during the TDR testing. In following step  304 , the test data  218  are stored in the memory  208 . In step  306 , the testing application  216  then is launched to visually render the test data  218 , and also compute the test data  218  to derive return loss data  242 . In step  308 , the return loss data  242  are then evaluated by the testing application  216  to determine whether a standard requirement is satisfied. As has been described above, the standard requirement may impose that the return loss data  242  be less than a threshold reference  240 . 
         [0028]    If the return loss data  242  do not satisfy the standard requirement, the tested device contains defective portions. To simulate a correction operation, the user in step  310  then can manually modify certain portions of the test data  218  that are identified as likely corresponding to the defective portions of the tested device. While the modification of the test data  218  has been described as being manually done, it is worth noting that the modification of the test data  218  may also be programmed to be automatically computed by the testing application  216 . The steps  306  and  308  then are repeated to reprocess the modified test data  218 . 
         [0029]    When the return loss data satisfy the standard requirement, it is then determined in step  312  whether any portions of the test data  218  have been modified. In case no changes have been introduced by the user in the test data  218 , the tested device has passed the compliance test. Otherwise, the defective portions of the tested device corresponding to the modified portions of the test data  218  may be corrected in step  314 . The modified device then may be tested again through the steps  302 - 308 . 
         [0030]    As has been described above, the TDR testing system and method are thus able to allow a user to flexibly modify the test data of the reflection signal provided by the testing machine, so that the correction operations on identified defective locations in the tested device may be simulated when the test data are computed for evaluation. When the evaluation step fails, the actual correction operations thus may be performed on the tested device in a more efficient manner. In particular, a testing operator can determine which modifications are more cost competitive and efficient before the corrections are actually applied, which saves labor cost and time. 
         [0031]    The above description illustrates various embodiments of the present invention along with examples of how aspects of the present invention may be implemented. The above examples, embodiments, instruction semantics, and drawings should not be deemed to be the only embodiments, and are presented to illustrate the flexibility and advantages of the present invention as defined by the following claims.