Abstract:
A method and apparatus for improving yield ratio of testing are disclosed. The method includes the following steps. First of all, devices are tested and electromagnetic interference is measured. Next, the test results are examined for whether the devices pass the test or not. Then, electromagnetic interference data are examined for whether the electromagnetic interference data are over a predetermined standard if the devices fail the test. The above-mentioned steps are performed again if the electromagnetic interference data are over a predetermined standard. The test is terminated if the devices still fail the test and the values of electromagnetic interference are still over a predetermined standard.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The entire contents of Taiwan Patent Application No. 098109158, filed on Mar. 20, 2009, from which this application claims priority, are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method and apparatus for improving yield ratio of a testing device, and more particularly, to a method and apparatus for improving yield ratio of a testing radio frequency device. 
         [0004]    2. Description of Related Art 
         [0005]    Functions and electric properties of various integrated circuit chips (IC) such as radio frequency ICs, memory devices, consumer devices, logic and mixed signal ICs, image sensors and driver ICs must be tested and verified by a tester in order to insure their quality. The above-mentioned devices under test or DUTs are tested through test signals provided by the tester to verify the functions. However, DUTs are usually sensitive to high frequency electromagnetic interference, such as with radio frequency ICs, wireless LAN devices or cellular phone application devices. The testing of such radio frequency ICs, wireless LAN devices or cellular phone application devices specifically sensitive and susceptible to high frequency electromagnetic interference can result in alteration of test results. Particular instances in which high frequency electromagnetic interference can alter test results of the testing of these sensitive devices can involve the high frequency electromagnetic interference altering the judgment of the tester such that a DUT is placed in a fail bin rather than a pass bin, or vice versa, or can even result in incorrect marginal-fail decisions thus causing yield loss of testing quantity and reducing an efficiency of (e.g., wasting the time of) the work force. 
         [0006]    In order to avoid such interference from the testing environment and resulting misjudgments of test results, the interference from a given testing environment is usually checked before testing. Uses of wireless communication equipment are restricted and other outside influences are removed or adjusted before testing. However, such acts cannot immediately resolve the problems resulting from unpredictable electromagnetic interference since the strength and influence of electromagnetic waves tend to vary with location and time. Such unpredictable electromagnetic interference problems can also introduce uncertainty as to yield loss of testing or even if there is any yield loss of testing. In such circumstances, it is hard to estimate how much yield loss of testing is caused by electromagnetic interference when electromagnetic interference is present and to timely exclude the electromagnetic interference. Since yield loss of testing caused by electromagnetic interference can be difficult to estimate, yield loss recovery evaluation can also be difficult to perform. 
         [0007]    In order to solve the above-mentioned problems, the invention provides a method and apparatus for improving yield ratio of testing devices to avoid error resulting from electromagnetic interference of the environment and timely resolve the yield loss of testing caused by unpredictable electromagnetic interferences so as to improve the efficiency and yield ratio of testing and decrease the cost of testing. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the present invention is to provide a method and apparatus for improving yield ratio of testing to avoid the error resulting from electromagnetic interference of environment and timely resolve the yield loss of testing caused by unpredictable electromagnetic interferences, so as to improve the efficiency and yield ratio of testing and to decrease the cost of testing. 
         [0009]    According to the object, one embodiment of the present invention provides a method for improving yield ratio of testing. The method comprises the following steps. First of all, a test of a device and measurement of electromagnetic interferences is performed. Then, whether the device passes the test or not is determined. Next, whether values of the electromagnetic interference are over a predetermined standard value or not is determined if the device fails the test. The above steps are performed again if the values of the electromagnetic interference are over the predetermined standard value. The test is terminated if the device fails the test and the values of the electromagnetic interference are over the predetermined standard value. 
         [0010]    The invention provides a test apparatus (e.g., device) for improving yield ratio of testing. The test apparatus comprises a test procedure module in a tester and an interference-receiving module. The interference-receiving module receives electromagnetic interferences and transmits values of the electromagnetic interference to the tester, wherein the test procedure module determines whether the electromagnetic interferences will or is likely to affect a testing result of devices under test. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings illustrate various embodiments of the present invention and are a part of the specification. The illustrated embodiments are merely examples of the present invention and do not limit the scope of the invention. 
           [0012]      FIG. 1  shows one embodiment of a test system for improving yield ratio of testing in accordance with the invention. 
           [0013]      FIG. 2  shows one embodiment of a method for improving yield ratio of testing according to the invention. 
           [0014]      FIGS. 3A and 3B  show two preferred embodiments of the interference-receiving module of the invention. 
           [0015]      FIG. 4  shows a diagram of carrier to noise(C/N) versus bit error rate(BER). 
           [0016]      FIG. 5  shows a diagram of the RF signals versus DC voltage signals. 
           [0017]      FIG. 6  shows a diagram of DC voltage signals transformed from the received RF signals versus time. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    A detailed description of the present invention will be provided in the context of the following embodiments, which are not intended to limit the scope of the present invention and which can be adapted for other applications. While drawings are illustrated in detail, it is appreciated that the scale of each component may not be expressed exactly. 
         [0019]      FIG. 1  shows one embodiment of a test system for improving yield ratio of testing in accordance with the invention. The test system  100  comprises a tester  102 , an interference-receiving module  108 , and a test interface  110 . The tester  102  comprises a host  104 . The host  104  comprises a control unit including a central processing unit, data storing media comprising hard disks, and memory devices. The host  104  is the center of control and management for handling all test activities of the system  100  including the generation and transmission of test signals, control of a handler to pick up and place and to sort devices under test, and determinations of pass or failure of the devices under test according to the test signals. The host  104  comprises a test procedure module  106 . The test procedure module  106  includes a central processing unit, a computer readable medium storing processor executable instructions or programs, and instructions or programs stored on the computer readable medium operable to perform the method for improving yield ratio of testing of the invention. The computer readable medium comprises, but is not limited to, hard disks and memory devices. The programming language of the instructions or programs stored on the computer readable medium operable to perform the method for improving yield ratio of testing of the invention includes but is not limited to C/C++. The interference-receiving module  108  connects to the tester  102  to receive electromagnetic interference noises (i.e./e.g., interference(s)) and transmits the electromagnetic interference noises to the tester  102 . The host  104  and the test procedure module  106  determine whether the electromagnetic interference noises affect the testing result of the devices under test. The test interface  110  includes a device under test board(DUT board) or a load board as the interface of signal transmission between the tester  102  and the devices under test  112 . The devices under test  112  comprise, but are not limited to, WLAN 802.11a/b/g/n devices, RF devices, cellular phone application devices such as GPRS, CDMA and Bluetooth devices. 
         [0020]      FIG. 2  shows an embodiment of a method for improving yield ratio of testing according to the invention. In one embodiment, as performed in the test system  100  shown in  FIG. 1 , the tester  102  controls a handler (not shown) to pick and place the devices under test  112  onto the test interface  110 . The tester  102  transmits test signals to the devices under test  112  through the test interface  110  so as to test the devices  112 . The interference-receiving module  108  detects and receives electromagnetic interference noises and transmits the electromagnetic interference noises or data to the tester  102 , as block  202  in  FIG. 2 , devices are tested and electromagnetic interferences (i.e./e.g., interference(s)) are measured. The test items depend on the specifications of the devices under test  112  or the demand of the customer. The test items include, but are not limited to, error vector magnitude(EVM), bit error rate(BER), signal to noise ratio(S/N) and noise value. In order to receive and measure the electromagnetic interferences, the interference-receiving module  108  is set to receive the frequency band of the devices under test  112 . Next the tester  102  determines whether the devices pass the test or not according to the test signals transmitted from the devices under test  112  through the test interface  110 , as block  204 . The tester  102  proceeds to other test(s) if the tester  102  determines that the devices under test  112  pass the test according to predetermined standard(s), as block  206 . The tester  102  examines the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  if the tester  102  determines that the devices under test  112  fail the test according to predetermined standard, as block  208 . Then the tester  102  examines and determines whether the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  exceed a predetermined value, as block  210 . The tester  102  determines that the devices under test  112  fail the test due to self-failure of the devices under test and proceeds to other tests if the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  do not exceed a predetermined value. The tester  102  tests the devices under test and the interference-receiving module  108  measures electromagnetic interferences again if the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  exceed the predetermined value. Then the tester  102  determines whether the devices pass the test or not according to the test signals transmitted from the devices under test  112  through the test interface  110  again. Next the tester  102  proceeds to other tests if the tester  102  determines that the devices under test  112  pass the test according to predetermined standard. The tester  102  examines the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  if the tester  102  determines that the devices under test  112  fail the test according to predetermined standard again. The tester  102  proceeds to other tests if the tester  102  determines that the devices under test  112  pass the test according to predetermined standard again. The tester  102  examines the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  if the tester  102  determines that the devices under test  112  fail the test according to predetermined standard again. The tester  102  determines that the devices under test  112  fail the test due to self-failure of the devices under test and proceeds to other tests if the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  do not exceed a predetermined value again. The tester  102  stops testing and controls a handler to cause/provide an alert if tester  102  determines that the devices under test  112  fail the test and the values or data of the electromagnetic interferences transmitted from the interference-receiving module  108  exceed a predetermined value again, as block  212 . 
         [0021]      FIGS. 3A and 3B  show two preferred embodiments of the interference-receiving module of the invention respectively. In the embodiment of  FIG. 3A , the interference-receiving module  108  comprises an antenna module  302 . The antenna module  302  includes dipole antennas with operating frequency corresponding to the frequency band of the devices under test. The antenna module  302  transmits electromagnetic interference signals, noises or data to the tester  102  via RF ports of the tester  102 .  FIG. 4  shows a diagram of carrier to noise(C/N)versus bit error rate(BER). The electromagnetic interference noise is transmitted from a personal handy-phone system(PHS), the frequency is 1900 MHz and the testing item is bit error rate. The electromagnetic interference noise detected by the antenna module  302  can be used as background noise of the device under test. The electromagnetic interference noise would increase the bit error rate of the device under test. The bit error rate resulting from the electromagnetic interference noise can be obtained through  FIG. 4  if the modulation system, C of carrier and N of electromagnetic interference noise, are known or measured. The real bit error rate of the device under test can be obtained by calculating the difference between the measured bit error rate of the device under test and the bit error rate resulting from the electromagnetic interference noise so that one can exclude the effect of the electromagnetic interference noise on the measure of the bit error rate. The modulation systems in  FIG. 4  includes Phase Shift Keying(PSK), Quadrature Amplitude Modulation(QAM), Binary Phase Shift Keying(BPSK), Quadrature Phase Shift Keying(QPSK), 8PSK, 16PSK, 32PSK, 16 QAM, 64 QAM and 256 QAM. 
         [0022]      FIG. 3B  shows another one of the preferred embodiments of the interference-receiving module of the invention. In the embodiment of  FIG. 3B , the interference-receiving module  108  comprises an antenna module  302 , a low noise amplifier  304 , and a RF power detector  306 . The antenna module  302  includes dipole antennas with operating frequency corresponding to the frequency band of the devices under test. The low noise amplifier  304  amplifies and transmits RF signals to the RF power detector  306 . The low noise amplifier  304  can be omitted. The RF power detector  306  transforms the received RF signals to DC voltage signals and transmits them to the tester  102 .  FIG. 5  shows a diagram of the RF signals versus DC voltage signals. In  FIG. 5 , the RF signals could be electromagnetic interference noise when the DC voltage signals are over 0.6V. The measurement of the DC voltage signal can be performed by the following two methods: 
         [0000]    (a) Performing progressive average calculations using a VI measurement instrument.
 
(b) Performing function test using a tester, wherein DC voltage signals transformed from the received RF signals are transmitted to the tester through I/O pin(s) of the tester.  FIG. 6  shows a diagram of DC voltage signals transformed from the received RF signals versus time. In  FIG. 6 , the peak values of DC voltage signals last for 577 μs. The function test can be performed by setting threshold voltage as 1.0V for 1 μs. By using the threshold voltage comparing to low, the existence of electromagnetic interference can be detected. The function test performed on the tester can be performed together with regular test item(s) to monitor electromagnetic interferences so that the resource of testing equipment and testing time can be saved.
 
         [0023]    The invention utilizes a tester, an interference-receiving module, and a test interface to test RF devices. A test procedure module of a host of the tester performs a method for improving yield ratio of testing to avoid test errors resulting from electromagnetic interferences. The method and system can timely detect yield loss of testing caused by unpredictable electromagnetic interferences so as to improve yield ratio of testing and decrease the cost of device testing. 
         [0024]    Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.