Reliability Report

AOS Semiconductor
Reliability Report
AOB27S60_AOT27S60_AOTF27S60,
600V 27A MOS Power Transistor, rev A
ALPHA & OMEGA Semiconductor, Inc
www.aosmd.com
AOS Reliability Report
1
This report applies for high voltage MOSFET AOB27S60_AOT27S60_AOTF27S60.
The AOT27S60& AOB27S60 & AOTF27S60 have been fabricated using an advanced high voltage MOSFET
process that is designed to deliver high levels of performance and robustness in popular AC-DC applications.
By providing low RDS(on), Ciss and Crss along with guaranteed avalanche capability these parts can be
adopted quickly into new and existing offline power supply designs.
For Halogen Free add "L" suffix to part number:
AOT27S60L & AOB27S60L & AOTF27S60L
“Commitment to Excellence at Quality & Reliability!”
To achieve this vision, AOS continuously strive for the excellence in design, manufacturing, reliability
and proactively response to the customer’s feedback.
AOS ensures that all the product quality and reliability exceed the customer’s expectation by
constantly assessing any potential risk, identifying cause of the suspected failures, driving corrective
actions and developing prevention plan within the committed time through the continuously
improvement.
This AOS product reliability report summarizes AOS Product Reliability result. The published product
reliability data combines the results from new product Qualification Test Plan and routine Reliability
Program activities. Accelerated environmental tests are performed on a specific sample size, and
then followed by electrical test at end point. The released product will be categorized by the process
family and be monitored on a quarterly basis for continuously improving the product quality. Table 1
lists the generic reliability qualification requirements and conditions:
Table 1: AOS Generic Reliability Qualification Requirements
Test Item
Test Condition
HTGB
Temp = 150°c ,
Vgs=100% of Vgsmax
HTRB
Solder reflow
precondition
HAST
Temp = 150°C ,
Vds=80% of Vdsmax
168hr 85°c /85%RH +
3 cycle reflow @250°c
(MSL level 1)
130 +/- 2°C ,
85%RH, 33.3 psi,
Vgs = 80% of Vgs max
Sample
size
Acc/Reject
77 pcs / lot
0/1
77 pcs / lot
0/1
-
The sum of
PCT ,TC and
HAST
0/1
100 hrs
55 pcs / lot
0/1
Time Point
168 / 500 hrs
1000 hrs
168 / 500 hrs
1000 hrs
Pressure Pot
121°C , 29.7psi,
100%RH
96 hrs
77 pcs / lot
0/1
Temperature
Cycle
-65°C to 150°C,
air to air,
250 / 500
cycles
77 pcs / lot
0/1
Power Cycle
∆ Tj = 125 °C
4286 cycles
77 pcs / lot
0/1
AOS Reliability Report
2
High Temperature Gate Bias (HTGB) & High Temperature Reverse Bias
(HTRB)
HTGB burn-in stress is used to stress gate oxide at the elevated temperature environment hence any
of the gate oxide integrity issue can be identified. HTRB burn-in stress is used to verify junction
degradation under the maximum operation temperature.
Through HTGB & HTRB B/I stress test, the device lifetime in field operation & long term device level
reliability can be determined. FIT rate is calculated by applying the Arrhenius equation with the
activation energy of 0.7Ev and 60% of upper confidence level at 55 deg C operating conditions.
Solder reflow precondition (pre-con)
Solder reflow precondition is the test that simulates shipment and storage of package in under
uncontrollable environment. Precondition is the pre-requirement for the mechanical related reliability
tests (such as Temperature Cycle, Pressure Pot and High Acceleration Stress TEST (HAST). The
routine of the test are: parts will be soaked in moisture then bake in pressure pot, or being placed into
85% RH, 85 deg C environment for 168 hrs. Then they will be run through a solder reflow oven with
temperature at 250ºC+/- 5ºC. The test condition totally complies with MSL level 1. Pre-condition is a
test that is detected package delamination, lifted bond wire issue.
Temperature Cycling (TC)
Temperature cycling test is to evaluate the mechanical integrity of the package and the interaction
between the die and the package. This is an air to air test at temperature range from -65ºC/150ºC
and stress duration is from 250 cycles to 500 cycles.
Pressure Pot (PCT)
PCT test is the test that measures the ability of the device withstand to moisture and contaminant
environment. The test is done under enclosed chamber with the condition 121ºC 15+/- 1PSIG,
100%RH and stress duration is 96 hrs.
High Acceleration Stress Test (HAST)
High acceleration stress test is to stress the devices under high humidity, high pressure environment
under DC bias condition. If ionic contamination involved, the corrosion from metal layer can be
accelerated by the HAST stress condition.
Power Cycle
The power cycle test is performed to determine that the ability of a device to withstand alternate
exposures at high and low junction temperature extremes with operating biases periodically applied
and removed. It is intended to simulate worst case conditions encountered in typical application.
The following tables summarize the qualification results based on the device/process families and the
package types, respectively.
AOS Reliability Report
3
Table 2 Reliability Test and Package test Result:
Test Item
Test Condition
HTGB
Temp = 150°c ,
Vgs=100% of Vgsmax
HTRB
Solder reflow
precondition
Temp = 150°C ,
Vds=80% of Vdsmax
168hr 85°c /85%RH +
3 cycle reflow @250°c
Total
Sample
size
Number of
failure
539
0
462
0
-
627
0
Time Point
168 / 500 hrs
1000 hrs
168 / 500 hrs
1000 hrs
(MSL level 1)
HAST
130 +/- 2°C , 85%RH, 33.3 psi,
Vgs = 80% of Vgs max
100 hrs
165
0
Pressure Pot
121°C , 29.7psi, 100%RH
96 hrs
231
0
Temperature
Cycle
-65°C to 150°C,
air to air,
250 / 500
cycles
231
0
Power Cycle
∆Tj=125°C
4286 cycles
231
0
AOS Reliability Report
4
Reliability Evaluation:
FIT rate (per billion): 4
MTTF = 32220 years
The presentation of FIT rate for the product reliability (AOB27S60_AOT27S60_AOTF27S60) is
restricted by the actual burn-in sample size of the selected product. Failure Rate Determination is
based on JEDEC Standard JESD 85. FIT means one failure per billion hours.
2
9
Failure Rate (FIT) = Chi x 10 / [2 (N) (H) (Af)]
9
= 1.83 x 10 / [2 (13x77) (1000) (258)] = 4
9
8
MTTF = 10 / FIT = 2.82 x 10 hrs = 32220 years
Chi² = Chi Squared Distribution, determined by the number of failures and confidence interval
N = Total Number of units from HTRB and HTGB tests
H = Duration of HTRB/HTGB testing
Af = Acceleration Factor from Test to Use Conditions (Ea = 0.7eV and Tuse = 55°C)
Acceleration Factor [Af] = Exp [Ea / k (1/Tj u – 1/Tj s]
Acceleration Factor ratio list:
Af
55 deg C
70 deg C
85 deg C
100 deg C
115 deg C
130 deg C
150 deg C
258
87
32
13
5.64
2.59
1
Tj s = Stressed junction temperature in degree (Kelvin), K = C+273.16
Tj u =The use junction temperature in degree (Kelvin), K = C+273.16
k = Boltzmann’s constant, 8.617164 X 10 -5eV / K
AOS Reliability Report
5