Methodology for Computation of Maximum Power

Technical Note
AN-75-005
Power Handling
Model Type: LTCC Low Pass Filters
Methodology for Computation of Maximum Power Handling in LTCC Low Pass Filters
Purpose:
The purpose of this application note is to describe the
procedure used for determining power handling
capability of LFCW-Series LTCC Low Pass Filters due to
thermal-related failures.
Introduction:
2. Measure small signal insertion loss of the DUT
in the pass band with a network analyzer.
3. Use the highest insertion loss in the pass band
and the thermal resistance determined from
step 1 to compute the power dissipation, and in
turn the temperature rise and the max power
handling. See detailed flow chart in Figure 2.
LFCW series filters are made using LTCC (Low
Temperature Co-fired Ceramic) technology. Due to low
losses and high temperature handling capability of the
ceramic material, they can handle reasonably high
power levels, even though they are of small size. Testing
of power and thermal resistance is required to
determine the maximum power handling capability.
Failure Mechanism:
Applying RF power to the LFCW filters will generate
heat due to Ohmic and dielectric losses and cause the
rise of DUT temperature. LTCC technology uses thin
layers of ceramic on which conductors are printed using
noble metals. Various layers are bonded to each other
by firing around 850°C. In actuality, the DUT is soldered
onto a PCB. While the LTCC filter itself can handle very
high temperatures, the weak point is the solder joint,
whose melting point is much lower than 850°C.
Therefore we use the solder melting point (with some
margins) as the maximum allowable temperature of the
DUT for maximum power computations. Assuming that
the DUT is soldered onto a PCB using high temperature
solder such as SnAgCu, whose melting point is 217°C,
we can allow the DUT temperature to rise to 200°C
without melting the solder joint. Note that the
procedure described here can be used to compute max
power for any user-defined maximum temperature.
Methodology Employed:
1. Determine the thermal resistance of the DUT at
a fixed frequency through thermal imaging
measurements. See detailed flow chart in
Figure 1.
Figure 1: Thermal Resistance Measurement Flow Chart
AN-75-005 Rev.: A M150261 (04/15/15) File: AN75005.doc
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Technical Note
AN-75-005
Power Handling
Model Type: LTCC Low Pass Filters
Test Conditions:
• Room temperature
• RF input: continuous wave
• Frequency = 4 GHz, see note 4
• Pin = 30, 33, 35, 36, 37, 38, 39, 40 dBm.
Notes:
1) Calibration method: zero & calibrate each
power meter before test, connect the throughline of TB-720+ as DUT, and offset power meter
F until it shows the same reading as power
meter H at 4 GHz.
2) Take thermal images after applying each power
level for 5 minutes, or until the DUT
temperature is stable.
3) Record power meter F as input power Pin;
record power meter H as output power Pout.
Insertion loss = Pout – Pin.
4) Choose the frequency at which you have a high
power source. In this case, the test was
performed only at mid-band frequency, 4 GHz.
Figure 2: Flow Chart Representing Determination
of Maximum Input Power
AN-75-005 Rev.: A M150261 (04/15/15) File: AN75005.doc
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Technical Note
Power Handling
Model Type: LTCC Low Pass Filters
AN-75-005
Test Sequence:
A.
Signal Generator
I.
DC Voltage Supply
B.
Attenuator
C.
High Power Amplifier
J.
Thermal
Imaging
Camera
D.
Bi-Directional Coupler
B.
Attenuator
B.
Attenuator
F.
Power Meter
E.
Termination
H.
Power Meter
G.
DUT
Figure 3: LFCW Series Power Handling Test Block Diagram
No. Type
Description
ESG Series Signal Generator, 250kHz4.0GHz
5W, 10dB Attenuator,
DC-18GHz
16W, 45dB High Power Amplifier, 1800-4000
MHz
250W, 35dB Coupler,
900-9000MHz
MFG.
MFG/Model
Agilent
E4422B
A
Signal Generator
B
Attenuator
C
Power Amplifier
D
Bi-Directional Coupler
E
Termination
50-Ohm, SMA Male
F
Power Meter
RF Power Meter
G
DUT
Solder on Test Board
H
Power Meter
EPM-P Series Power Meter,
with E-Series Avg Power Sensor
(-30 - +44 dBm), 10MHz – 18GHz
Agilent
E4416A
I
DC Power Supply
30V/50A, 1500W System DC Power Supply
Agilent
N5765A
J
Thermal Imaging Camera 12VDC, 1.25A Thermal Camera
MiniCircuits
MiniCircuits
MiniCircuits
MiniCircuits
Boonton
MiniCircuits
BW-S10W5+
ZHL-16W-43-S+
ZGDC35-93HP+
4231A
TB-720+
Optotherm InfraSight EL
Table 1 Power Handling Test Equipment List
AN-75-005 Rev.: A M150261 (04/15/15) File: AN75005.doc
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Technical Note
Power Handling
Model Type: LTCC Low Pass Filters
AN-75-005
Test Data and Calculations:
Below is an example of test analysis for filter model LFCW-1142+. Testing was performed at 4 GHz at room
temperature, and prediction was made at 11.4 GHz based on the calculated thermal resistance, assuming thermal
resistance is frequency independent.
Thermal imaging test for computing the Thermal Resistance of DUT
Power Handling Test 4GHz (@25°C) TB#1
Input Power
(dBm)
Input Power
(W)
Power Out
(dBm)
Power Out
(W)
0
30
33
35
36
37
38
39
40
0.001
1.00
2.00
3.16
3.98
5.01
6.31
7.94
10.00
-0.38
29.62
32.60
34.58
35.54
36.52
37.51
38.48
39.44
0.0009
0.92
1.82
2.87
3.58
4.49
5.64
7.05
8.79
Unit
Insertion Loss Power Dissp
Temperature
(dB)
(W)
(°C)
0.38
0.0001
23.0
0.38
0.08
24.6
0.40
0.18
27.7
0.42
0.29
31.5
0.46
0.40
34.8
0.48
0.52
38.1
0.49
0.67
44.2
0.52
0.90
50.9
0.56
1.21
59.3
Calculating the max input power at room ambient temperature, 25°C
To be conservative, we choose the max thermal resistance to do the calculation.
Power Handling Analysis 11.4GHz (@25°C) TB#1
Thermal
Input Power Input Power Insertion Loss Power Out
Power Out Power Dissp
Resitance
(dBm)
(W)
(dB)
(dBm)
(W)
(W)
(ϴda)
0
0.001
2.13
-2.13
0.001
0.0004
31.5
30
1.00
2.13
27.87
0.61
0.39
31.5
33
2.00
2.15
30.85
1.22
0.78
31.5
35
3.16
2.17
32.83
1.92
1.24
31.5
36
3.98
2.21
33.79
2.39
1.59
31.5
37
5.01
2.23
34.77
3.00
2.01
31.5
38
6.31
2.24
35.76
3.77
2.54
31.5
39
7.94
2.27
36.73
4.71
3.23
31.5
40
10.00
2.29
37.71
5.90
4.10
31.5
2.31
38.69
7.40
5.19
31.5
41
12.59
42
15.85
2.33
39.67
9.27
6.58
31.5
Calculating the max input power at 100°C ambient temperature
Power Handling Analysis 11.4GHz (@100°C) TB#1
Thermal
Input Power Input Power Insertion Loss Power Out
Power Out Power Dissp
Resitance
(dBm)
(W)
(dB)
(dBm)
(W)
(W)
(ϴda)
0
0.001
2.61
-2.61
0.001
0.0005
31.5
30
1.00
2.61
27.39
0.55
0.45
31.5
33
2.00
2.63
30.37
1.09
0.91
31.5
35
3.16
2.65
32.35
1.72
1.44
31.5
36
3.98
2.69
33.31
2.14
1.84
31.5
37
5.01
2.71
34.29
2.69
2.33
31.5
2.72
35.28
3.37
2.94
31.5
38
6.31
39
7.94
2.75
36.25
4.22
3.73
31.5
40
10.00
2.77
37.23
5.28
4.72
31.5
Temperature
Change (°C)
Thermal
Resitance
(ϴda)
1.6
4.7
8.5
11.8
15.1
21.2
27.9
36.3
19.1
26.8
29.2
29.5
28.8
31.5
31.1
30.0
Temperature
Change (°C)
12.2
24.5
39.2
50.0
63.4
80.1
101.8
129.1
163.5
207.2
Temperature
Change (°C)
14.2
28.5
45.5
57.9
73.3
92.5
117.3
148.5
Unit
Temperature
(°C)
25.0
37.2
49.5
64.2
75.0
88.4
105.1
126.8
154.1
188.5
232.2
Unit
Temperature
(°C)
100.0
114.2
128.5
145.5
157.9
173.3
192.5
217.3
248.5
Figure 4: Power Handling Test Analysis in Excel
AN-75-005 Rev.: A M150261 (04/15/15) File: AN75005.doc
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Technical Note
Power Handling
Model Type: LTCC Low Pass Filters
AN-75-005
Table 2 below shows the final results of maximum
power for models LFCW-1062+, LFCW-1142+, and
LFCW-133+.
Max Input Power Max Input Power
@25°C (W)
@100°C (W)
Model
LFCW-1062+
4.0
1.6
LFCW-1142+
6.3
3.2
LFCW-133+
12.6
6.3
Conclusion:
The method for testing of power handling
demonstrated in this application note feasibly predicts
the maximum power rating of LFCW-Series low pass
filters. Analysis shows that the model with less pass
band insertion loss exhibits a higher maximum power
rating.
Table 2: Maximum Power Rating Comparison of LFCWSeries
Max Power Computation at User-Defined
Maximum DUT Temperature:
Equations [1] and [2] below can be used to compute
maximum power at any maximum DUT temperature
defined by the user.
Abbreviation
TDUT
Description
Max. allowed DUT temperature (°C)
TA
Ambient temperature (°C)
IL
Insertion loss (dB)
Pd
Power dissipation (W)
Θ
Thermal resistance (°C/W)
Table 3: Parameters for Computation of Power
Dissipation and Maximum Power Handling
[1]
[2]
AN-75-005 Rev.: A M150261 (04/15/15) File: AN75005.doc
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Technical Not
AN-75-005
Power Handling
Model Type: LTCC Low Pass Filters
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