Test circuits and current pulse generator for simulating an electrostatic discharge

Abstract

This invention is an electrostatic discharge (ESD) testing circuit that can deliver current pulses to a component under test (CUT) with controlled impedance. Generated current pulses simulating ESD events, such as those compliant to the European International Electrotechnical Commission IEC 61000-4-2 standard, can be delivered to the CUT with low distortion through a constant impedance electrical path, such as a combination of cables and controlled impedance conductors of printed wiring boards and wafer probes compatible with packaged IC devices, assemblies, and wafers, plus an impedance controlling series resistance. The current pulse can be delivered to the CUT with various forcing impedances. Measurements of the current passing through the CUT can be made.

1 . A testing apparatus comprising:
 a pulse generator with output and ground terminals and containing an energy storage network with a switch operable to connect and disconnect said energy storage network to said output terminal such that, when disconnected, said energy storage network can be charged to a predetermined level and such that, when connected, said energy storage network is discharged to produce a current pulse between said output and ground terminals that rises to a peak current in ten nanoseconds or less and decays to substantially zero current within one microsecond after said connection; and   an electrical conduction path having a signal conductor and a ground conductor, said signal conductor having an approximately constant impedance along its length relative to said ground conductor, and having first and second ends, wherein the first end of said signal conductor is connected to said pulse generator output terminal, the first end of said ground conductor is connected to said pulse generator ground terminal, and the second end of said signal conductor is sized to be connected to one of a plurality of terminals of a circuit under test; and   a resistor of resistance equal to or greater than the impedance of said signal conductor connected between the second end of said ground conductor and one or more other tetuiinals of said circuit under test.   
     
     
         2 . The apparatus of  claim 1  wherein said electrical conduction path is comprised of a network of conductors, connectors and/or inserted components all of approximately the same mutual impedance. 
     
     
         3 . The apparatus of  claim 2  wherein said network of conductors, connectors and/or inserted components all have an impedance of approximately 50 ohms 
     
     
         4 . The apparatus of  claim 2  wherein said network may include low pass filters, relays, electrical signal transducers, current sensors, voltage sensors, attenuators, wafer probes, test fixture boards, or sockets. 
     
     
         5 . The apparatus of  claim 2 , wherein at least one component of said network includes a printed wiring circuit board having a socket sized to hold and make electrical contact with the terminals of said circuit under test. 
     
     
         6 . The apparatus of  claim 1 , wherein the resistance value of said resistor is approximately equal to the electrical conduction path impedance. 
     
     
         7 . The apparatus of  claim 1 , wherein the resistance value of said resistor is approximately 330 ohms minus the electrical conduction path impedance. 
     
     
         8 . A testing apparatus comprising:
 a pulse generator with output and ground terminals and containing an energy storage network with a switch operable to connect and disconnect said energy storage network to said output terminal such that, when disconnected, said energy storage network can be charged to a predetermined level and such that, when connected, said energy storage network is discharged to produce a current pulse between said output and ground terminals that rises to a peak current in ten nanoseconds or less and decays to substantially zero current within one microsecond after said connection; and   an electrical conduction path having a signal conductor and a ground conductor, said signal conductor having an approximately constant impedance along its length relative to said ground conductor, and having first and second ends, wherein the first end of said signal conductor is connected to said pulse generator output terminal, the first end of said ground conductor is connected to said pulse generator ground terminal, and the second end of said signal conductor is sized to be connected to one of a plurality of terminals of a circuit under test; and   an electrical recording device that has an input resistance of approximately 50 ohms; and   a cable having first and second conductors with mutual impedance of approximately 50 ohms along its length, each having first and second ends, wherein the first end of said first conductor is connected to the second end of said ground conductor, wherein the first end of said second conductor is connected to one or more terminals of said circuit under test, and wherein the second ends of said conductors are connected to said electrical recording device.   
     
     
         9 . The apparatus of  claim 8 , wherein said cable is divided into two or more segments and further comprises one or more 50-ohm impedance signal attenuators inserted in series between said cable segments. 
     
     
         10 . The apparatus of  claim 8 , further comprising a resistor of 50 ohms or greater resistance inserted in series between said first end of said second conductor and said one or more terminals of said circuit under test. 
     
     
         11 . The apparatus of  claim 10  wherein said signal conductor has an impedance of approximately 50 ohms, and the value of said resistor is approximately 230 ohms.