เป็นเนื้อหาของบทความหรือสินค้าโดยละเอียดกรุณาใส่ข้อความ …
What is the different between CDM , HBM and MM test ?
uWhen people walk, they generate some electricity and discharge it to ground. Every step builds up charge that can be represented by:
uΔV/Δt = n Δq/C
uwhere n is the
number of steps/second and C is the person’s capacitance. Consider a typical
case on an insulating floor, showing a ΔV increase of 300 V per human step and
reaching about 3 kV in 10 seconds. (Note: some charge leakage occurs.)
uFor HBM tests,
there is a simple series RC network to simulate the discharge from a human
body. A 1-MΩ resistor is used to charge a 100-pF capacitor. A 1.5-kΩ resistor
is used for discharging. HBM events are most disruptive with fast rise times.
Therefore, fast rise time pulses are required to more precisely simulate a HBM
discharge event.
ui(t) = i0 exp(–t/τ)
uwhere:
ui0 = VHBM/(RDUT + R)
uand:
ut = C(R + RDUT)
uR = 1.5 kΩ
uPower
dissipation to the device under test (DUT) is:
uP(t)=i2(t) RDUT
CDM
uCDM simulates
device damage that could not be simulated by HBM testing. It simulates a device
charged either directly by triboelectric effect (see
“Harvesting Power Using Triboelectric Generators”)
or indirectly by electrostatic induction and static charge stored in a part’s
body that discharges in an outside environment.
u
uThis test is
used to simulate situations that happen in manufacturing environments such as
mechanical device handling where devices slide down shipping tubes or test
handlers that build up a charge that’s subsequently discharged to ground.
Figure 2 shows the CDM ESD test and typical current waveform characteristic.
When an external ground touches the DUT pin of the charged device, the stored
charge will be discharged from the device to the outside ground. In the CDM
test, the device is kept on its back, facing upward on a test fixture.
CDM currents
are higher than HBM currents because there is no current limiting resistor in
the path to limit the discharge. For a 500-V test voltage, the current waveform
rise time is generally around 400 ps with the peak
current around 6 A for 1.5 to 2 ns. For a 1000-V test voltage, the peak current
magnitude is around 12 A.uSimilar rise
times (i.e., ~10 ns) and total duration for HBM and MM cause comparable joule
heating that results in similar failure mechanisms for both models. The failure
signature and discharge processes of the MM test are generally the same as that
of the HBM test. Thus, the HBM test could guarantee MM ESD robustness.
u
uUsually, the
stress level of MM ESD is approximately 10 times lower than that of HBM ESD.
Also, the protection voltage level for HBM typically is ~2 kV while for MM it
is ~200 V and for CDM it is ~500 V. CDM is completely different from HBM and
MM, so there is no correlation between them. Therefore, CDM and HBM tests are
commonly used to test ESD protection circuits. Figure 4 shows current waveforms
characteristics for HBM, MM, and CDM. The CDM waveform corresponds to the
shortest known ESD event and has a rise time of 400 ps with a total
duration of ~2 ns.
