Abstract:
An apparatus for continuity testing of a pogo pin in a probe comprises a substrate having a pad, a power supply providing a voltage difference between the pad and the pogo pin, and a sensing device signaling when the substrate contacts the probe, and a current is generated by the connection of the pogo pin and the pad.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an apparatus and method for continuity testing of pogo pins, particularly to an apparatus and method for continuity testing of pogo pins in a probe for semiconductor device testing.  
           [0003]    2. Description of the Prior Art  
           [0004]    [0004]FIG. 1 is a diagram showing a probe for semiconductor device testing. A probe  1  comprises circularly arranged pogo pins  11  and  12  which provide ground and test signals to a wafer being tested (not shown) respectively. Since the elasticity of the pogo pins  11  and  12  may be worn, which results in a contact fault, a continuity test of the pogo pins  11  and  12  is needed before the wafer can be tested using the probe.  
           [0005]    Conventionally, the continuity test is implemented with the wafer under test put in the probe  1 , a probe card and a test head mounted on the pogo pins  11  and  12 . The results of the continuity test appear on a screen of the test head.  
           [0006]    However, there are several drawbacks to the conventional continuity test method.  
           [0007]    1. Contact faults of the pogo pins  11  for ground signals cannot be detected since all of them are electrically connected in the probe  1 .  
           [0008]    2. Alignment of the wafer under each test is necessary. Thus makes the continuity test time-consuming.  
           [0009]    3. The operator must check hundreds of results appearing on the screen of the test head and a refresh of the results takes 1˜2 seconds due to the long response time of analog-to digital converters.  
           [0010]    There is an alternative method for continuity testing, wherein a sheet of carbon paper is applied to the pogo pins and the operator can detect failed pogo pins by inspecting the imprints on the carbon paper. This method, however, introduces carbon contamination to the pogo pins and the probe.  
         SUMMARY OF THE INVENTION  
         [0011]    Therefore, the object of the present invention is to provide an apparatus and method for continuity testing of pogo pins in a probe, in which the wafer, probe card and test head are not necessary and the operator can easily identify the failed pogo pins.  
           [0012]    The present invention provides an apparatus for continuity testing of a pogo pin in a probe. The apparatus comprises a substrate having a pad, a power supply providing a voltage difference between pad and pogo pin, and a sensing device signaling when the substrate contacts the probe and a current is generated by connection of the pogo pin and the pad.  
           [0013]    The present invention further provides a method for continuity testing of a pogo pin in a probe. The method comprises the steps of providing a substrate having a pad, generating a voltage difference between the pad and the pogo pin, placing the substrate into the probe, and signaling when a current is generated by connection of the pogo pin and the pad.  
           [0014]    In the present invention, LEDs are used to detect contact faults between the pogo pins and the pads. The failed pogo pins do not form closed loops in which currents are generated by the voltage difference. The LEDs corresponding to the failed pogo pins remain unlit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The following detailed description, given by way of example and not intended to limit the invention solely to the embodiments described herein, will best be understood in conjunction with the accompanying drawings, in which:  
         [0016]    [0016]FIG. 1 is a diagram showing a probe for semiconductor device testing.  
         [0017]    [0017]FIG. 2 is a diagram showing an apparatus for continuity testing of a pogo pin in a probe according to one embodiment of the invention.  
         [0018]    [0018]FIG. 3˜ 6  are cross-sectional diagrams showing an apparatus for continuity testing of a pogo pin in a probe according to one embodiment of the invention.  
         [0019]    [0019]FIG. 7 is a flowchart of a method for continuity testing of a pogo pin in a probe according to one embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    [0020]FIG. 2 is a diagram showing an apparatus for continuity testing of a pogo pin in a probe according to one embodiment of the invention. A continuity test apparatus  2  comprises circularly arranged LEDs  22  corresponding to the pogo pins  11  and  12  shown in FIG. 1. The LEDs  22  are all mounted on a substrate  21  to signal contact faults of the pogo pins  11  and  12 .  
         [0021]    [0021]FIG. 3 is a cross-sectional diagram cut along the line AA′ in FIG. 2. The substrate  21  comprises pads  23  corresponding to the pogo pins  11  and  12  on the opposite side of the LEDs  22 . Pads  23  are electrically connected to the negative terminals of corresponding LEDs  22  through via holes (not shown). The positive terminals of the LEDs are electrically connected together through conducting traces (not shown) laid on the substrate  21 .  
         [0022]    A power supply  13  in a tester is connected between the pogo pins  11  and  12 , and the LEDs  22  to generate a voltage difference 2V between the pogo pins  11 ,  12  and the LEDs  22 .  
         [0023]    Please refer to FIG. 4, in which the substrate  21  is mounted on the probe  1  and brought into contact with the pogo pins  11  and  12  so that the pads  23  of the substrate  21  contact the corresponding pogo pins  11  and  12 . Close loops are formed among the power supply  13 , LEDs  22 , pads  23  and pogo pins  11  and  12 . The voltage difference results in currents flowing through the loops, which light the LEDs  22 .  
         [0024]    Please refer to FIG. 5, in which pogo pins  11   2  and  12   4  fail. They are shorter than the others due to lack of elasticity.  
         [0025]    Please refer to FIG. 6, in which a continuity test is implemented with the failed pogo pins  11   2  and  12   4 . There are contact faults between the pad  23   3  and pogo pin  11   2 , and the pad  23   8  and pogo pin  12   4 . The closed loops among the power supply  13 , LED  22   3 , pad  23   3  and pogo pin  11   2 , and the power supply  13 , LED  22   8 , pad  23   8  and pogo pin  12   4  are not completed. Thus, the LEDs  22  are lit except for the LEDs  22   3  and  22   8 . Accordingly, the operator can easily identify the failed pogo pins as  11   2  and  12   4 .  
         [0026]    The previously described LEDs  22  are used to detect the formation of the closed loops by sensing the currents in the loops. They can be electrically connected between any two of the LED, the pad and the pogo pin.  
         [0027]    [0027]FIG. 7 is a flowchart of a method for continuity testing of pogo pins in a probe according to one embodiment of the invention.  
         [0028]    In step  71 , a substrate is provided, which has pads corresponding to the pogo pins and via holes through which the pads electrically connected to terminals.  
         [0029]    In step  72 , a voltage difference is generated between the terminals and the pogo pins.  
         [0030]    In step  73 , the substrate is placed into the probe so that the pads contact the normal pogo pins forming closed loops. The failed pogo pins do not contact the pads, resulting in incomplete loops.  
         [0031]    In step  74 , LEDs corresponding to the pogo pins are connected to sensor currents in the closed and open loops. The pogo pins&#39; contact with the pads results in the currents lighting the corresponding LEDs, while the failed pogo pins result in no current, with the corresponding LEDs remaining unlit.  
         [0032]    In conclusion, the present invention provides a substrate with LEDs for implementation of the continuity test, whereby the operator can easily identify the failed pogo pins thus the wafer, probe card and test head used in the conventional method are not required.  
         [0033]    While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims must be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.