TWI777707B - Energy-storage capacitor malfunction detection method based on test carrier board - Google Patents

Abstract

An energy-storage capacitor malfunction detection method based on a test load board is provided that includes following steps. (S1) The test load board of an automatic test equipment is connected to a DPS test circuit. (S2) The test load board is set to be an empty-load status having no under-test chip thereon. (S3) The test load board begins to operate. (S4) A target capacitance of an energy-storage capacitor is estimated according to at least one parameter of the test load board. (S5) A constant output voltage and a clamped current are retrieved. (S6) A test time is calculated. (S7) At least one operation parameter of the DPS test circuit is set. (S8) A force-v mode of the DPS test circuit is triggered. (S9) An actual capacitance of the energy-storage capacitor is calculated. (S10) A malfunction condition is determined according to data of the actual capacitance. Comparing to a current technology, the present invention use an already-presented function of the automatic test equipment to detect and obtain the malfunction condition of the energy-storage capacitor and handle the condition instantly to guarantee a test accuracy.

Description

Failure detection method of energy storage capacitor based on test carrier board

The invention relates to the technical field of semiconductor testing, in particular to a method for detecting failure of an energy storage capacitor based on a test carrier board.

In general, a stable power supply is required for the normal operation of the integrated circuit chip. Usually, when designing a circuit, some decoupling capacitors, including filter capacitors with small capacitance and energy storage capacitors with large capacitance, are arranged near the power pins where the power pins of the chip are connected to the power network.

For wafer testing applications, all the pins of the wafer must be connected to the pins of the automatic testing machine one by one, and there are often long internal cable connections between the pins and the test circuit unit inside the automatic testing machine. Therefore, when the chip under test is loaded on the circuit board of the test carrier, the power pins of the chip generally do not have the opportunity to connect to the power network with a large area of copper cladding. In this case, in order to accurately test the function and performance of the chip under test, it is even more necessary to connect some decoupling capacitors near the power pins of the chip on the test carrier board.

However, among these decoupling capacitors, the energy storage capacitors with larger capacitance will bring a problem: when the indicator of the static DC leakage current IDDQ of the tested chip needs to be tested, the energy storage capacitor will bring obvious errors. Therefore, when the test item of the test program is executed to measure IDDQ, it is necessary to cut off the storage Capacitor connection to the power pins of the wafer under test. That is to say, the connection of the energy storage capacitor needs to be designed to be on or off. Usually, relays are used to realize this on-off switching. When designing the circuit board of the test vehicle, a relay should be connected in series between the energy storage capacitor and the power network.

However, various failures will occur in the test vehicle circuit board during use. One of the typical failure scenarios is the failure of the circuit related to the energy storage capacitor. For example: failure of relay, failure of energy storage capacitor, open circuit or short circuit of circuit connection, wrong material of capacitor. This type of failure will show an abnormal capacitance value of the energy storage capacitor. Therefore, measuring the capacitance value of the capacitor can diagnose this type of failure of the test vehicle circuit board.

This kind of failure usually leads to a decrease in the yield or performance of the wafer under test, but there are too many factors related to the test process and yield, so this kind of failure has a certain degree of concealment. Under normal test conditions, there is no targeted detection method and method for whether the capacitance value of the energy storage capacitor is abnormal. Therefore, when investigating the reasons for the low yield rate, many other factors are often checked first, and then it is the turn to check the energy storage capacitor of the carrier circuit board. This often takes a lot of time.

In order to overcome the deficiencies of the prior art, the present invention provides an energy storage capacitor failure detection method based on a test carrier board, which utilizes the existing functions of an automatic testing machine to realize the failure detection of the energy storage capacitor on the carrier circuit board.

In order to achieve the above purpose, a method for detecting the failure of an energy storage capacitor based on a test carrier board is designed, including: (S1) connecting the test carrier board of an automatic testing machine to a DPS (Device Power Supply; device power supply) test circuit; (S2) place the test carrier board in an unloaded state without the tested chip; (S3) start the test carrier board to run; (S4) estimate the energy storage capacitor according to at least one parameter of the test carrier circuit board (S5) Read the constant output voltage Vdut and the clamping current Iclamp according to the data of the test program; (S6) Calculate the test time t; (S7) Set at least one working parameter of the DPS test circuit; (S8) Make the main control module of the automatic testing machine trigger the constant voltage mode of the DPS test circuit; (S9) calculate the measured capacitance value C2 of the measured energy storage capacitor; and (S10) according to the measured measured capacitance value C2 of the energy storage capacitor data to determine the failure of the energy storage capacitor.

The formula for calculating the test time is t=C1*Vdut/Iclamp.

The calculation formula of the measured capacitance value of the energy storage capacitor is C2=△Q/△V=(I*t)/△V=I*(t1-t0)/(V1-V0).

The failure conditions of the energy storage capacitor include the short circuit of the energy storage capacitor to the ground, the open circuit or detachment of the capacitor, the wrong specification of the capacitor material, the failure of the relay to open, the failure of the relay to close, and the failure of the line connection.

To determine the failure of the energy storage capacitor, the specific judgment method is as follows: (1) Under the condition of the relay being closed, when the test voltage does not change within the test time and is close to 0V, it is judged that the energy storage capacitor is short-circuited to the ground; (2) Under the condition that the relay is closed, when the test voltage reaches the limit value immediately after the test is started, it shows that the measured capacitance value cannot be measured, and it is judged that the capacitance is open circuit or falling off; (3) Under the condition of the relay being closed, the actual measured If the capacitance value and the standard deviation are more than 25%, it is judged that the specification of the capacitor material is wrong; (4) After executing the relay open command and close command, test the measured capacitance value respectively, and the results are the same, which is the normal value of the capacitor, and it is judged as The relay cannot be disconnected; (5) After executing the relay opening command and closing command, test the measured capacitance value respectively, and the result is the same, which is the value of the capacitor disconnection condition, showing that the capacitance value cannot be measured, and it is judged that the relay cannot be closed; (6) Under the condition that the relay is closed, when the test voltage reaches the limit value immediately after the test is started, the display capacitance value cannot be measured, and it is judged that the line connection is not possible.

Compared with the prior art, the present invention provides a method for detecting the failure of an energy storage capacitor based on a test carrier board, which utilizes the existing functions of an automatic testing machine to realize the detection of the failure of the energy storage capacitor on the carrier circuit board, and accurately know the carrier circuit. The failure situation of the energy storage capacitor on the board, and deal with it in time to ensure the accuracy of the integrated circuit chip test.

Regarding the features, implementation and effects of this case, a preferred embodiment is described in detail as follows in conjunction with the drawings.

200: Failure detection method of energy storage capacitor

S1~S10: Steps

300: DPS test circuit

310: Adjustable sampling resistor

320: Current Amplifier

330: Voltage Amplifier

340: Force Amplifier

400: Test Carrier Board

410: wafer under test

420: Relay

ADC1, ADC2: Analog to Digital Converters

CS: energy storage capacitor

DO: Diode

DPS_DAC: Voltage

I_clamp: clamp current

Vdut: constant output voltage

[Fig. 1] is a working curve diagram of the DPS test circuit in an embodiment of the present invention; [FIG. 2] is a flowchart of a method for detecting failure of an energy storage capacitor based on a test carrier board in an embodiment of the present invention; and [FIG. 3] is a DPS test circuit and a test carrier board in an embodiment of the present invention Schematic diagram of the connection.

The present invention will be further described below according to the accompanying drawings.

Please refer to Figure 1 to Figure 3 at the same time. FIG. 1 is a working curve diagram of a DPS test circuit in an embodiment of the present invention. FIG. 2 is a flowchart of a method 200 for detecting failure of an energy storage capacitor based on a test carrier board according to an embodiment of the present invention. FIG. 3 is a schematic diagram of the connection between the DPS test circuit 300 and the test carrier board 400 in an embodiment of the present invention. The DPS test circuit 300 is connected to the test carrier board 400 to perform the energy storage capacitor failure detection method 200 .

As shown in FIG. 1 , typically, the power pins of the wafer under test are connected to a DSP test circuit 300 called a device power supply unit (Device Power Supply) inside the automatic test machine.

The DSP test circuit 300 has both the function of constant voltage output and the function of clamping current. When the DSP test circuit 300 starts to power on the tested chip 410, its output voltage will not jump from 0 to the constant output voltage Vdut, but power the tested chip 410 with a constant clamp current I_clamp. At this time, the DSP The test circuit 300 operates in the current clamp clamp I mode, which is essentially a constant current mode. During this process, as the wafer under test 410 and its decoupling capacitors are charged, the voltage thereof rises steadily. When the voltage rises to the constant output voltage Vdut, the DSP test circuit 300 switches to the ForceV mode, that is, the constant voltage mode, and the current will drop to the working current of the chip at this time.

At the same time, the DSP test circuit 300 also has a measurement circuit of analog-to-digital converter sampling, which can measure the current and voltage output by it at any time. This allows us to plot a V-t curve of voltage versus time.

In the Clamp I stage, according to the time characteristic of voltage rise, that is, the slope of the V-t curve, the total capacitance at the power supply pin of the chip 410 under test can be calculated, which basically reflects the capacitance of the parallel energy storage capacitor CS.

As shown in FIG. 2 , a method for detecting failure of an energy storage capacitor based on a test carrier board includes: (S1) connecting the test carrier board 400 of the automatic testing machine to the DSP test circuit 300; (S2) connecting the test carrier board 400 is in an unloaded state without the tested chip 410; (S3) start the test carrier board 400 to run; (S4) estimate the target capacitance of the energy storage capacitor CS according to at least one parameter of the test carrier circuit board 400 (S5) read the constant output voltage Vdut and the clamping current Iclamp according to the data of the test program; (S6) calculate the test time t; (S7) set at least one working parameter of the DSP test circuit 300; (S8) enable the automatic The main control module of the testing machine triggers the constant voltage mode of the DSP test circuit 300; (S9) calculates the measured capacitance value C2 of the measured energy storage capacitor CS; (S10) calculates the measured capacitance value C2 according to the measured measured energy storage capacitor CS , to determine the failure of the energy storage capacitor CS.

The formula for calculating the test time is t=C1*Vdut/Iclamp.

The calculation formula of the measured capacitance value of the energy storage capacitor CS is C1=△Q/△V=(I*t)/△V=I*(t1-t0)/(V1-V0).

The failure conditions of the energy storage capacitor CS include the short circuit of the energy storage capacitor CS to the ground, the open circuit or detachment of the capacitor, the wrong specification of the capacitor material, the situation that the relay 420 cannot be disconnected, the situation that the relay 420 cannot be closed, and the line connection is blocked.

Judging the failure of the energy storage capacitor CS, the specific judgment method is as follows: (1) Under the condition that the relay 420 is closed, when the test voltage does not change within the test time and is close to 0V, it is judged that the energy storage capacitor CS is short-circuited to ground; ( 2) Under the condition that the relay 420 is closed, when the test voltage reaches the limit value immediately after the test is started, it shows that the measured capacitance value cannot be measured, and it is judged that the capacitance is open circuit or falling off; (3) Under the condition that the relay 420 is closed, when the test is calculated, If the measured capacitance value and the standard deviation are more than 25%, it is judged that the specification of the capacitor material is wrong; (4) After executing the opening and closing instructions of the relay 420, the measured capacitance value is tested respectively, and the results are the same, which is the normal value of the capacitance, It is judged that the relay 420 cannot be disconnected; (5) after executing the opening and closing commands of the relay 420, the measured capacitance values are tested respectively, and the results are the same, which are the values of the capacitor disconnection condition, and the displayed capacitance value cannot be measured, and it is judged that the relay is a relay. 420 cannot be closed; (6) Under the condition that the relay 420 is closed, when the test voltage reaches the limit value immediately after the start of the test, the display capacitance value cannot be measured, and it is judged that the line connection is not connected.

As shown in FIG. 3 , the equivalent circuit diagram of the DSP test circuit 300 working in the constant voltage output mode. The circuit has two negative loops controlled by a closed loop, one is an adjustable sampling resistor 310 and a current amplifier The amplifier 320 forms a current negative receiving loop, and the other is a voltage negative receiving loop formed by the voltage amplifier 330 . When the output voltage is relatively small, the output current is relatively large, and the output of the current amplifier 320 is greater than the output of the voltage amplifier 330. At this time, the diode DO in the figure is turned on, the circuit works in the current negative receiving mode, and the output is a constant current. This constant Current is clamp current. When the output current is relatively small and the output voltage is relatively large, the output of the current amplifier 320 is smaller than the output of the voltage amplifier 330, and the circuit works in the negative voltage receiving mode, and the output is a constant voltage.

When preparing for the test, first set the DPS_DAC voltage to 0V, then the output terminal of the forced amplifier 340 is also 0V, and the voltage of the pin 410 of the tested chip is 0V, and the voltages of all negative loops are also 0V. When the circuit starts to work, the DPS_DAC voltage is set to the target voltage (eg, 3.3V), and the output voltage Vout of the forced amplifier 340 will first rise rapidly. However, due to the existence of the adjustable sampling resistor 310 and the capacitance of the carrier board, the voltage of the pin of the tested chip 410 will not rise rapidly, and the output current Iout of the forced amplifier 340 will rise rapidly along with Vout. The negative current is limited and the output intensity of the amplifier 340 is forced to further increase, maintaining the current output Iout at the current clamp value. At this time, the circuit works in the clamp current stage: the current is constant, the capacitor is charged, and the voltage increases evenly. When the voltage rises to the target value, the closed loop control of the negative voltage dominates. At this time, the circuit works in the constant voltage output stage: the voltage will no longer climb, the capacitor will no longer be charged, the output current will soon drop to a relatively low level, and the diode DO will be cut off. The actual test work is done in the clamp current phase. By setting the voltage of the DPS_DAC, the voltage parameter of the constant voltage output of the DSP test circuit 300 can be set, that is, the constant voltage parameter. By selecting the gear of the adjustable sampling resistor 310, the clamp output current parameter of the DSP test circuit 300 can be set. Namely the Clamp I parameter, the current actual current can be read out through the analog-to-digital converter ADC1 at any time. The current actual voltage can also be read out at any time through the analog-to-digital converter ADC2. When the circuit works in the clamped current stage, by measuring the actual voltage multiple times, it can be drawn. Create a V-t diagram (voltage versus time waveform diagram, as shown in Figure 1), when the circuit is working in the clamp current stage, the actual current can be measured once, so as to calibrate the clamp constant current value, according to the V-t diagram, Calculate the slope of the voltage climbing slope △ V/△t, if the slope is not significantly abnormal (neither close to 0, nor close to infinity), then calculate the measured capacitance C_real=I_clamp/(△V/△t) according to the measured value of the clamp current I_clamp, the slope and the voltage The capacity can be used to judge whether it is abnormal and infer various failure conditions.

Although the specific embodiments of the present invention are described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principle and essence of the present invention .

200: Failure detection method of energy storage capacitor

S1~S10: Steps

Claims (5)

A method for detecting failure of an energy storage capacitor based on a test carrier board, comprising: (S1) connecting the test carrier board of an automatic testing machine with a DPS (Device Power Supply; device power supply) test circuit; (S2) connecting The test carrier board is in an unloaded state without the tested chip; (S3) start the test carrier board to run; (S4) estimate an energy storage according to at least one parameter of the test carrier circuit board A target capacitance value C1 of the capacitor; (S5) read a constant output voltage Vdut and a clamping current Iclamp according to a data of a test program; (S6) calculate a test time t; (S7) set the DPS test circuit at least one working parameter; (S8) make a main control module of the automatic testing machine trigger a constant voltage mode of the DPS test circuit; (S9) calculate a measured capacitance value C2 of the actual measured energy storage capacitor; and (S10 ) According to the measured data of the measured capacitance value C2 of the energy storage capacitor, determine a failure condition of the energy storage capacitor. The method for detecting failure of an energy storage capacitor based on a test carrier board according to claim 1, wherein a formula for calculating the test time is t=C1*Vdut/Iclamp. The method for detecting failure of an energy storage capacitor based on a test carrier board according to claim 1, wherein the calculation formula of the measured capacitance value of the energy storage capacitor is C2=△Q/△V=(I*t)/△V =I*(t1-t0)/(V1-V0). The method for detecting the failure of an energy storage capacitor based on a test carrier board according to claim 1, wherein the failure condition of the energy storage capacitor includes a short circuit of an energy storage capacitor to ground, a capacitor open circuit or falling off, a capacitor material Incorrect specifications, a relay cannot be disconnected, a relay cannot be closed, and a line cannot be connected. The method for detecting the failure of an energy storage capacitor based on a test carrier board according to claim 1, wherein the failure condition of the energy storage capacitor is determined, and the specific determination method is as follows: (1) Under a relay closing condition, when the When the test voltage does not change within the test time and is close to 0V, it is judged that the energy storage capacitor is short-circuited to the ground; (2) Under the condition that the relay is closed, when the test voltage reaches a limit value immediately after the test is started, the measured capacitance is displayed. If the value cannot be measured, it is judged that the capacitor is open circuit or falling off; (3) Under the condition that the relay is closed, when the measured capacitance value and a standard deviation of more than 25% are calculated after the test, it is judged that the material specification of the capacitor is wrong. ; (4) After executing a relay opening command and a closing command, test the measured capacitance value respectively, and the result is the same, which is a normal value of capacitance, and it is judged that the relay cannot be disconnected; (5) When executing the relay After the opening command and the closing command, the measured capacitance value is tested respectively, and the same result is obtained, which is a value of a capacitor disconnection condition, indicating that the measured capacitance value cannot be measured, and it is judged that the relay cannot be closed; and (6) in the Under the condition that the relay is closed, when the test voltage reaches the limit value immediately after the test is started, it shows that the measured capacitance value cannot be measured, and it is judged that the line connection is not possible.

Images