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AN0013
NBB Series and NDA Series Reliability
NBB Series and NDA Series Reliability
This application note provides additional information on component reliability with varying device junction temperature,
and the effect of the package used on junction temperature. This information is provided for the NBB Series HBT Broad-
band Feedback Amplifiers and NDA Series HBT Distributed Amplifiers.
Device Reliability
RFMD uses an industry-proven, high-performance, high-reliability gallium indium phosphide on gallium arsenide (InGaP/
GaAs) heterojunction bipolar transistor (HBT) technology for its NBB series and NDA series broadband amplifiers.
This process has completed in excess of 1 million device hours of accelerated life testing. The test device used has two
emitter fingers of size 3µm by 20µm. The device was operated at 3V and with a current density of 25KA/cm
2
. The test
device is of comparable size to device sizes in the NBB series and NDA series of components. Additionally, the operating
point, both of voltage and current, was comparable to the nominal operating point of the device. Testing was performed
at five junction temperature points (257°C, 275°C, 285°C, 300°C and 315°C) with 50 to 100 devices tested at each tem-
perature.
Figure 1 shows the device results with extrapolation of Mean Time to Failure (MTTF) for lower junction temperatures.
Results show that for a device junction temperature of 150°C the mean time to failure is greater than 2 million hours. For
a device junction temperature of 125°C the mean time to failure is 30 million hours.
1.5
350
300
250
Junction Temperature ( °C )
200
Ea = 1.3 eV
MTTF = 3E7 Hrs
@ Tj = 125 C
1.7
1.9
2.1
2.3
2.5
100
2.7
2.9
50
30
25
Stress Condition :
3V , 25 KA/cm2
1.0E+05
1.0E+08
3.1
3.3
1.0E+04
1.0E+06
1.0E+07
1.0E+09
1000 / °K
150
15
1.0E+01 1.0E+02
1.0E+03
Median Time to Fail (hrs)
Figure 1. MTTF for Test Device
Copyright 1997-2002 RF Micro Devices, Inc.
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TECHNICAL NOTES
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AN0013
Packaged Component Reliability
All NBB and NDA products complete a junction temperature measurement before design qualification is completed. The
test verifies device junction temperature in the package at the maximum recommended baseplate operating tempera-
ture.
From Figure 1, RFMD recommends that all NBB and NDA products be operated with a junction temperature below
150°C to ensure MTTF greater than 1 million hours.
The junction temperature is dependent upon several key factors:
1. Baseplate temperature
2. Package type
3. Device bias
4. Die to package attachment process
5. Package to board attachment process
6. Board via layout
Each of these key factors is addressed during thermal junction measurements. Details are given below.
RFMD recommends that these devices be used at a baseplate temperature no greater than 85°C, to ensure that the
device junction temperature limit outlined above is maintained. Therefore all device junction thermal measurements are
performed on components at 85°C baseplate temperature.
RFMD tests all die types in every package style offered. For the NBB series and NDA series the package styles currently
offered are the Micro-X 4-lead surface mount ceramic package and surface mount ceramic multi pin grid array (MPGA)
package.
The junction temperature measurement is carried out at three bias points:
Low current, Id set between half the recommended current and the recommended bias current.
Nominal current, Id set at nominal recommended current.
Limiting current, Id is set to the draw the maximum current while maintaining a device junction temperature of 150°C.
Die are mounted in packages using the standard manufacturing process. However the package lids are not fitted to allow
the die junctions to be viewed during testing.
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TECHNICAL NOTES
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The packages are then mounted to an evaluation board using a standard RF board material, with the recommended via
hole layout. This layout uses multiple ground via holes to ensure good thermal dissipation away from the package to the
baseplate.
In conclusion, the parts are mounted in a realistic application setting, and the test simulates actual device junction tem-
perature operation at the maximum recommended baseplate temperature for a variety of device biases.
Measurements are performed using a calibrated thermal imaging camera to accurately determine the temperature varia-
tion across the die when mounted in the package. Multiple components of each die type and package style are mea-
sured to allow an average junction temperature result to be generated.
An example of the thermal image generated is shown in Figure 2. This shows the temperature variation across an NBB-
300 (Micro-X style package) at 85°C baseplate temperature, with nominal 50mA device current. The temperature scale
is shown below the image. The image clearly shows the region of maximum temperature with a peak temperature of
139°C. This occurs at the transistor junction.
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Copyright 1997-2002 RF Micro Devices, Inc.
AN0013
Figure 2. NBB-300 Packaged Die Thermal Image
An example of some results of testing for NBB series and NDA series devices in each package style is given below for a
baseplate temperature of 85°C. The results shown are the average junction temperature of the sample measured.
Table 1. NBB Series Micro-X Packaged Junction Temperatures
Part
Number
NBB-300
NBB-400
NBB-500
Base
Temperature
o
C
85
85
85
Id
mA
25
Low
Tj
o
∆Tj
o
C
C
105.2 20.2
Nominal
Id
Tj
∆Tj
o
o
mA
C
C
50
47
35
138.0 53.0
131.2 46.2
120.3 35.3
Limiting
Id
Tj
Tj∆
o
o
mA
C
C
57
58
53
150.2 65.2
150.2 65.2
150.2 65.2
15
Part
Number
NBB-302
NBB-502
Base
Temperature
o
C
85
85
Id
mA
36
20
Low
Tj
o
∆Tj
o
C
C
107.6 22.6
97.9 12.9
Nominal
Id
Tj
∆Tj
o
o
mA
C
C
50
35
124.8 39.8
114.3 29.3
Limiting
Id
Tj
Tj∆
o
o
mA
C
C
67
57
151.4 66.4
150.7 65.7
Table 3. NDA Series MPGA Packaged Junction Temperatures
Id1
mA
NDA-212
NDA-312
NDA-412
85
85
85
28
Id2
mA
36
Tj
o
C
∆Tj
o
C
Id1
mA
29
29
29
Id2
mA
36
42
36
Tj
o
C
∆Tj
o
C
Id1
mA
32
31
Id2
mA
55
55
Tj
o
C
∆Tj
o
C
133.9 48.9
133.1
139.9
140.0
48.1
54.9
55.0
150.4
151.0
65.4
66.0
Copyright 1997-2002 RF Micro Devices, Inc.
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Table 2. NBB Series MPGA Packaged Junction Temperatures
AN0013
Note there is significant temperature rise from the baseplate temperature under nominal operating condition. This rise is
of the order of 30°C to 55°C above the baseplate temperature (85°C), depending on the device.
Additionally, the MPGA package style provides improved thermal performance. Device junction temperatures for NBB
parts tested in the MPGA package styles show a reduced junction temperature.
In conclusion, all NBB series and NDA series packaged parts operated at nominal bias with a baseplate temperature of
85°C (maximum recommended baseplate temperature) show an average junction temperature well below the 150°C rec-
ommended device junction temperature limit. Hence all NBB series and NDA series packaged parts provide a mean time
to failure greater than 1 million hours under these conditions.
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Copyright 1997-2002 RF Micro Devices, Inc.
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