Continuity Test

Question 1

Why do we do Continuity Test? / Objective of Continuity Test

Answer 1

FIMV.
To detect open/short present in between tester resources and die pad.

Question 2

How much current should be force? Why?

Answer 2

Force current between 100 - 500 uA.
Because able to measure diode knee voltage (0.3/0.7 V). Also, to avoid heat generation if any short present.

Question 3

How much voltage expected to measure using that method?

Answer 3

Expected to measure clam diode knee voltage (0.3-0.8V)

Question 4

Do clamp need to be setup? If yes, how much?

Answer 4

Yes, for open condition. Setup clamp voltage 1.5<voltage clamp<VCC.

Question 5

How to tell if continuity test FAILED?

Answer 5

Short Condition: Measured voltage < 0.3V
Open Condition: Measured Voltage > 1V
Passed Condition: 0.3 -0.8V

Question 6

Can we force voltage for Continuity Test?

Answer 6

Yes, FVMI can also be used.
Generally analog pin continuity is used to verify impedance of pin.

Question 7

What pin are used to test for continuity?

Answer 7

Input pins
Output Pins
I/O pins (which has protection diode)

Question 8

Can we do Continuity test for VCC, GND pins?

Answer 8

When we run continuity test at any digital pin, return current flows through VCC /GND pin. Therefore, discontinuity power pin will also be detected.

Question 9

why clamp diode presents in digital pins?

Answer 9

Clamp diode is used for protecting pin from overvoltage/undervoltage.

Question 10

How can we check continuity if no clamp diode presents in pin under test?

Answer 10

Using FVMI to calculate impedance and will validate with specs given for each pin.

Question 11

What is the difference between continuity and diode mode present in multimeter?

Answer 11

Continuity Mode: Will sound buzzer whenever path resistance between two test point is less than 50 Ohm. Using FVMI to measure impedance.
Diode Mode: Detect presence of diode. Multimeter force small current (500uA) and measure voltage (FIMV). Show diode knee voltage (0.7V) in forward bias.

Question 12

How much voltage measure if 100mA is force instead of 100uA?

Answer 12

Voltage will be around 1.5V (diode forward drop)

Question 13

What will happen to voltage if force current keeps increasing (more than 100mA)?

Answer 13

Voltage across diode will also slowly increase if current increase.

Question 14

What are the instruments that can be used for continuity test?

Answer 14

Bech Testing:
SMU (Source Measurement Unit) to FIVM
ATE Testing: PPMU (Pin Parametric Measure Unit)

Question 15

Debugging step if you measure zero voltage at pin

Answer 15

If zero voltage, short is present.
1. Remove device (open condition), if voltage is zero (then short), if voltage is hitting clamp (then open).