The Communications Edge
TM
Application Note
Product Information
AH11 Temperature Effects on Reliability
AH22 Included by Similarity
The AH11 is a GaAs MESFET MMIC amplifier based on GaAs processes and technology that have been
incorporated into WJ’s products for more than 15 years. Extensive life testing and field history of our GaAs
products have demonstrated excellent robustness and reliability. In general, WJ GaAs MMIC products are capable
of operating reliably at channel temperatures of +175° C based on accelerated lifetest measurements of small-signal
linear parameters like gain and input/output match. Biased lifetests at 250° C channel temperature for 1000 hours
routinely show no I
DS
failures for a sample size of 10 devices.
Long-term aging behavior of two-tone third-order output intercept (3OIP) performance, a non-linear characteristic,
has not been as extensively studied as the small-signal linear parameters. As a result, WJ Communications opted to
take a conservative position in specifying the maximum operating temperature of the AH11. Currently, the
maximum recommended operating temperature is +85° C (referenced to the GND lead of the device) which insures
that the maximum channel temperature at worst case power conditions will never be above a very safe +135° C.
Since releasing the product in 1999, WJ Communications has continued to study the aging characteristics of the
AG101's performance. As shown in the
AH11 Qualification Report,
we have reported no failures with over 7,500
device hours under an Accelerated Biased Humidity (HAST, +130°C, 85% RH, 33 psia) test. In addition, WJ has
not had any failures on over 80,000 device hours with a High Temperature Operating Lifetime (HTOL) test under a
biased condition at +125° C ground tab. The results of these tests confirmed that the AH11 temperature failure
mode is similar to that found in other WJ GaAs devices, and has an activation energy of about 1.5 eV [1].
The channel temperature can be calculated using the temperature rise due to power dissipation of the device, e.g.
ground tab temp erature (59.6° C) + voltage (5 V) x current consumption (360 mA max) x thermal resistance (28°
C/W) = 110° C. The calculation is conservative because as the temperature of the channel increases in the device,
the current consumption of the device typically decreases. A 10% reduction is typical with a temperature increase
from 25° C to 85° C at the ground lead temperature. Using the activation energy of 1.5 eV, the following MTBF
estimates have been calculated from the Arrhenius function [1]:
Channel
Temperature
(°C)
110
120
130
140
150
155
160
170
180
GND Lead
Temperature
(°C)
59.6
69.6
79.6
89.6
99.6
104.6
109.6
119.6
129.6
203.32
63.96
21.31
7.49
2.76
1.71
1.07
0.43
0.18
MTBF (million hrs)
MTBF
(million hours)
MTBF vs. Temperature
1000.0
100.0
Channel Temp
10.0
GND Tab Temp
1.0
0.1
25
50
75
100
125
150
175
200
Temperature (° C)
As can be seen from the MTBF numbers above, the predicted failure rate is still above 1 million hours, even at
operating temperatures up to +109.6° C (corresponding to channel temperatures of +160° C). Also note that these
MTBF estimates are a lower bound as the accelerated testing never resulted in 50% failures.
[1] Please refer to the application note “MTBF Analysis for AH1” for further information.
Specifications and information are subject to change without notice
WJ Communications, Inc
•
Phone 1-800-WJ1-4401
•
FAX: 408-577-6621
•
e-mail: sales@wj.com
•
Web site: www.wj.com
February 2002
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