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Improved Reliability and Producibility of Ballistic
Missile Defense Systems through Highly Controlled
Deposition of Critical Battery Components
AGREEMENT NO.: MDA-RHIT-022305-00
Progress Status Report
Submitted
August 15, 2008
To
Odyssian Technology LLC
By
Azad Siahmakoun, PhD
Director, Micro-Nanoscale Devices and Systems Facility
Rose-Hulman Institute of Technology
5500 Wabash Avenue
Terre Haute, IN 47803
Technical Contact: Azad Siahmakoun
TEL: (812) 877-8400
FAX: (812) 877-8023
Email: [email protected]
Business Contact: Danielle Helt
TEL: (812) 877-8454
Email: danielle.helt @rose-hulman.edu
1
The Project Goals
The current igniters used have a wire bridge connecting two contacts. Electrical current is sent
through a contact to heat up the wire and ignite pyrotechnic powder that lay under the wire.
These igniters must pass the No-Fire/ All-Fire tests i.e. they must not ignite when up to 1 amp
current passes for 5 minutes, but must ignite when 3.1-3.5 amps pass for 20ms. The variables in
this process are the way a bridge is deposited over the contacts, the settings at which the bridge is
deposited, the geometry of the bridge, and the material properties of the bridge.
In the Phase-I of this project it was determined that thin film deposition by sputtering was
optimal. After comparing the wire, line deposition, and circular deposition, it was determined
that circular deposition provided the least variance in resistance. Nichrome also appeared to be
the material that would be most durable and be able to pass all-fire and no-fire tests.
Currently, we are working to find sputtering settings which produce an optimum nichrome
thickness, which gives us a resistance of 1.0 – 1.4 Ohms. The igniters need to have a uniform
thermal distribution, so as to dissipate heat more evenly across the powder. The affects of
annealing on thermal distribution, as well as film composition and surface appearance are also a
concern. By the end of this Phase-II of the project, we hope to have the sputtering settings and
film thickness that give us optimal thermal distributions, determine whether or not annealing is
needed, and produce a solid thermal model of the igniter’s heat distributions.
Calibration of Voltage and Current meters
Before performing testing on new igniters, the multimeters used to measure the current and
voltage of the igniters were tested to ensure they were delivering data properly. Six resistors,
chosen with known resistance around the values expected from the igniters, were tested. Three
of these resistors had an associated error of their value provided by the manufacturer, the other
three did not. Of the three resistors with no reported manufacturing error there were two 1 Ω
resistors with a maximum power capacity of 10 W, and one resistor of 0.1 Ω with a maximum
power capacity of 5 W. The three resistors with reported manufacturing errors had the following
specifications: a 1 Ω resistor with a 10 W maximum power capacity and error of 5%; a 1 Ω, 10W
resistor with an error of 10 % and a 6.8 Ω, 5W resistor with an error of 5%.
Data for these six resistors was compiled by ramping current from a current source in increments
between 25 to 100 mA depending on the resistor, just like the no fire tests. Two multimeters
were used to measure the current and voltage across the resistors. These values were used
calculate the power going through the resistor. The resistance is calculated at each current
interval using Ohm’s Law and compared to its manufactured resistance value. In the case of
resistors with a given manufacturer’s error the percent error values are of significant importance
as to determining the quality of the setup. The percent error data of these six resistors appears in
Fig. 1.
2
% Error of Resistors
13.00
12.00
11.00
10.00
9.00
% Error
8.00
1 Ohm, Error not Given
1 Ohm, 5% Manufacturing Error
1 Ohm, 10% Manufacturing Error
1 Ohm,Error not Given
0.1 Ohms, Error not Given
6.8 Ohms, 5 % Manufacturing Error
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
Current (mA)
Figure 1: Percent error of known resistors using the ramping no fire setup
For resistors that provided a manufacturing error, the resistance computed using our setup was
within that manufacturer’s error range. For resistors providing no error range, two of them were
within 7% of the given resistance. For the other 1 Ω, 10 W resistor, the computed resistance
stayed within 13% of the given resistance throughout the test and was with 10% of the given
resistance until 1650 mA was reached. In conclusion, especially due to the fact that resistors of
given manufacturing error stayed within their given ranges, our setup was found to read current
and voltage properly. Figure 2 shows images of the setup with the inclusion of the thermocouple
described in the next section.
3
Figure 2: Images of the igniter testing setup
Camera Calibration
Along with recalibrating the electronic system, the camera’s calibration was also tested. When
looking at the thermal images, it clearly shows in the no fire tests that the glass substrate appears
the hottest. Thermodynamic laws show that the thin film should be the hottest structure, so this
suggested something was off with the camera. Looking into the operations of any IR camera, the
heat displayed varies with each object’s emissivity value, or the percentage of black body
radiation given off. It was found in numerous sources that the emissivity of nichrome is between
0.65 and 0.85, where as the glass substrate has a value around 0.95, which will cause it to appear
hotter than the thin film even if they are the same temperature.
In order to confirm this, ramping no fire tests were performed on two extra igniters, one ramped
between 0 and 800 mA in steps of 50 mA and the other between 0 and 400 mA in steps of 25
mA. During each step, the temperature of the igniters was measured using an Extech 421307
thermocouple. Once the temperature of the igniter reached steady state, the emissivity of the
camera was adjusted within the range of .65-.85 until the temperature reported by the camera
was within error (or as close as possible) to the temperature reported by the thermocouple.
The IR camera uses two sensors – a low range sensor for temperatures under 100 °C and high
range sensor for temperatures over 100 °C. The low range sensor has a product error of +/- 2 °C
while the high range sensor has an error of +/- 2%. These margins of error were used to best
select the ideal emissivity value for the thin film. For thin film temperatures within 15 °C of
room temperature the camera was unable to deliver values whose error range contained the
thermocouple temperature.
Below, in Table 1, is the data collected during the calibration of the camera. Two values for
error appear: Error (#), which indicates the numeric difference between the camera and the
thermocouple, and Error (%), which indicates the percentage error of the camera and the
4
thermocouple. The values that appear in red correspond to the specific camera sensor. For Error
(#) any value between 2 and -2 indicates that the camera’s first sensor and thermocouple reported
agreeable temperatures. For Error (%) any number between -2 and 2 indicates that the camera’s
second sensor and thermocouple reported agreeable values.
Table 1: Comparative results of the IR camera with thermocouple
Thermocouple Camera
Current
Temperature
Error
(mA)
°C
Temperature °C Emissivity (#)
0.0
18.7
22.6
0.85
3.9
25.0
19.7
22.6
0.85
2.9
50.2
22.5
25.6
0.85
3.1
75.1
26.0
29.2
0.85
3.2
100.0
30.0
32.9
0.85
2.9
125.7
36.8
37.0
0.85
0.2
150.1
42.4
42.0
0.85
-0.4
175.2
50.0
50.1
0.81
0.1
200.2
58.5
58.4
0.81
-0.1
225.1
67.7
67.9
0.84
0.2
250.3
75.8
77.0
0.84
1.2
275.1
95.5
94.9
0.80
-0.6
300.3
102.0
101.0
0.85
-1
325.2
119.0
118.5
0.85
-0.5
350.4
141.0
141.3
0.83
0.3
375.3
192.3
192.1
0.83
-0.2
400.1
206
205.8
0.81
-0.2
425.3
225 no data
Current
(mA)
0.0
50.4
100.1
150.6
200.2
250.3
300.3
355.5
400.0
450.4
500.0
600.5
700.5
800.4
Thermocouple
Temperature
°C
20.0
22.0
27.2
36.0
49.0
66.3
85.5
115.0
135.0
173.0
190.0
225
247
265
Error
(%)
20.86
14.72
13.78
12.31
9.67
0.54
-0.94
0.20
-0.17
0.30
1.58
-0.63
-0.98
-0.42
0.21
-0.10
-0.10
Camera
Temperature °C
25.4
26.8
31.6
38.2
49.3
66.0
85.1
116.1
136.1
173.3
190.0
224.3
246.5
266.3
Emissivity
0.85
0.85
0.85
0.85
0.85
0.83
0.83
0.83
0.85
0.85
0.85
0.85
0.85
0.82
Error
(#)
5.4
4.8
4.4
2.2
0.3
-0.3
-0.4
1.1
1.1
0.3
0.0
-0.7
-0.5
1.3
Error
(%)
27.00
21.82
16.18
6.11
0.61
-0.45
-0.47
0.96
0.81
0.17
0.00
-0.31
-0.20
0.49
From this test it was concluded that the emissivity value of the nichrome thin film is between
0.81 and 0.85 and the camera was adjusted accordingly. In order to confirm that these
conclusions would hold true at temperatures closer to 350 °C a brief check was done buy running
505 and 601 mA through igniter 15-1 and then comparing the readings of the camera with the
5
readings of the thermocouple. Table 2 displays the results; it concludes that at temperatures
between 300 and 350 °C an emissivity of 0.81 provided the most accurate measurements. With
all of the equipment recalibrated for more accurate measurements, new igniters were then tested.
Table 2: Comparison of the IR camera and thermocouple at high temperatures
Current (mA) Thermocouple
Camera
Error (%) Emmsivity
Temperature °C Temperature °C
505.0
601.0
302
327
301.5
327.0
-0.17
0.00
0.81
0.81
Initial Igniter Resistance
Each igniter in a set is first applied 25 mA for an initial resistance test. Figure 3 are the plots of
resistance values for each set in the report.
Resistance of set 13 at 25 mA
9
8
7
Resistance (ohm)
6
5
4
3
2
1
0
#13-1
#13-2
#13-3
#13-4
#13-5
Igniter #
(a)
6
Set 14 Resistance at 25 mA
7
6
Resistance (Ohm)
5
4
3
2
1
0
#14-1
#14-2
#14-3
#14-4
#14-5
#14-6
#14-7
#14-8
#15-7
#15-8
Igniter Number
(b)
Set 15 Resistance at 25 mA
3.50
3.00
Resistance (ohms)
2.50
2.00
1.50
1.00
0.50
0.00
#15-1
#15-2
#15-3
#15-4
#15-5
#15-6
Igniter #
(c)
Figure 3: Initial resistance values of set 13 (a), 14 (b), and 15 (c) at 25 mA
Set 13 had a mean resistance of 6.43 ohms and a standard deviation of 1.32 ohms. Set 14 had a
mean resistance of 5.59 ohms and a standard deviation of 0.63 ohms. Set 15 had a mean
resistance of 2.76 ohms and a standard deviation of 0.33 ohms. These high resistance values
suggest that either the sets are not 3 microns or that different conditions in the sputtering process
is affecting the resistance of each set.
7
No Fire Test
After the initial resistance test of set 13, it was clear they would not perform well, but a ramping
no fire test was still done on 2 of the igniters from this set. In a ramping no fire test, the igniters
are measured for resistance and temperature in steps of 50 mA, increasing until the igniter burns
out. As figure 4 shows, both igniters hit 350 C and burnout well before 1 A, failing the no fire
test. Instead of testing the rest of the igniters in this set in this fashion, the rest were used for all
fire tests to see how well they would perform.
No Fire of set 13
600
550
500
450
400
Temp (C)
350
13-1
13-4
300
250
200
150
100
50
0
0
50
100
150
200
250
300
350
400
450
500
550
600
Current (mA)
Figure 4: No fire ramping test of 2 igniters from set 13
Set 14 went through the same no fire tests, but also went through a 3 day 25 mA current test, so
those comparative results will be displayed in that section. Set 15 also went through several long
tests at 25 mA and a single no fire test was performed on igniter 15-1 after these tests, Fig. 5.
This igniter was chosen because it was near the average resistance of the set, so it would give a
general idea on if any in the set could pass the no fire test and also judge what currents could be
used in other tests without burning out the rest of the igniters in this set.
8
Ramp 15-1 Resistance of 3.21 ohms
350
300
Temp (C)
250
200
150
100
50
2.
56
25
.0
8
50
.4
5
75
.3
1
10
0.
12 8
5.
4
15 1
0.
6
17 2
5.
74
20
0.
5
22
5.
3
25
1.
3
27
5.
6
30
1
32
5.
9
35
0.
7
37
5
40
1
42
5.
3
45
0.
1
47
5.
6
50
0.
6
52
5
55
0.
8
57
5.
5
60
0.
9
62
5.
1
65
0.
6
67
5.
1
70
0.
3
0
Current (mA)
Figure 5: No fire test performed on igniter 15-1
72 Hour Testing
One of the requirements for the igniters is that they maintain a steady resistance after being
exposed to 25 mA of current for 72 hours. Set 14 had 4 igniters perform the no fire test and 4
igniters that has the 72 hour 25 mA current test performed and then went through the same no
fire test. As Fig. 6 shows, the igniters went through a significant increase in resistance after the
72 hour test, with a 6.7 to 10 % increase. As expected, the increase in resistance caused these
igniters to fail the no fire test slightly sooner than the ones that did not go through the test, failing
around 550 mA compared to 600 mA for the ones that did not go through the 72 hour test.
Resistance Change after 3 Day Test
8
7
Resistance (Ohm)
6
5
4
3
2
1
0
#14-3 9.91%
#14-4 7.67%
#14-5 9.99%
#14-6 8.51%
Igniter #
Figure 6: Resistance change of igniters from set 14 that went through the 72 hour test
9
Six igniters from set 15 also went through the 72 hour test. Initially, set 15 was tested for 44
hours before the test was stopped, which was holding up the setup for other tests. The test was
restarted and set 15 went through two 72 hour tests at 25 mA. Figure 7 displays a resistance
versus time trend of these six igniters for all 3 tests.
Set 15 Igniters - Exposure to 25 mA over 44 hours
4.00
3.50
Resistance (Ohms)
3.00
2.50
0 hours
30 hours
44 hours
2.00
1.50
1.00
0.50
0.00
1 11.25%
2 6.06%
3 8.90%
4 8.25%
5 4.80%
6 10.63%
Igniter #
(a)
Resistance During Second 72 hour/25 mA Test
4.00
3.50
Resistance (Ohms)
3.00
2.50
0 hours
65 hours
69.5 hours
72 hours
2.00
1.50
1.00
0.50
0.00
1
2
3
4
5
6
Igniter #
(b)
10
72 Hour Resistance Test Set 15 Igniters
4.50
4.00
3.50
Resistance (Ohms)
3.00
0 hours
7 hours
71 hours
72 hours
2.50
2.00
1.50
1.00
0.50
0.00
1
2
3
4
5
6
Igniter #
(c)
Figure 7: Change of igniters’ resistances as specific times during a 44 hour (a), first 72 hour (b) and second 72
hour (c) tests at 25 mA
As can be seen in the chart above, the igniters have a significant rise in resistance during the 44
hours and the following 72 hour test. For the second 72 hour test, the resistance change has
stabilized. The largest percentage change after all three tests was 23.44 % by igniter 1, Fig. 8.
The average percent change from the beginning of the test to the end for all six igniters was
15.12 %. The changes observed indicate that 25 mA for 72 hour trial will have a significant
impact on the igniter’s performance.
Percent Change After All 3 Long Term 25 mA Exposures
25.00
Percent Change (%)
20.00
15.00
10.00
5.00
0.00
1
2
3
4
5
6
Igniter #
Figure 8: Percentage change of igniters after a cumulative 188 hours of 25 mA
11
All Fire Tests
As part of the igniter’s working requirements is to reach 350 C when 3.5 A are applied for 20
ms. Beyond this requirement, tests were done with different currents on different resistance
igniters to see the speed of thermal conductivity of the igniters. Having the thermal camera
better calibrated, a fast frame rate capture was used to measure the temperature trends. A first
attempt at 650 mA, chosen so that it would not burn out the igniter, took well over 2 minutes to
reach a stable temperature of around 300 C. The current was increased to 1 A and 5 igniters
were tested from set 15. Just to note, all of these all fire test on set 15 were done after the
various 3 day current runs on them, so their resistance have changed slightly from their initial
value. Although it may be hard to see in Fig. 9, at 1 A the igniters hit 350 C as early as 2.6
seconds, but also as late as 26.2 seconds giving an average of 9.78 seconds.
All Fire Test at 1 A
650
600
550
500
450
Temp (C)
400
15-6
15-5
15-4
15-3
15-2
350
300
250
200
150
100
50
0
0
5
10
15
20
25
30
35
40
45
50
Time (s)
Figure 9: All fire tests at 1 A for 5 igniters from set 15
The test was done at 3 A, the limit of the power source, with 3 igniters from set 13 and 2 igniters
from set 15 seen in Fig. 10. For the igniters from set 13, the igniters hit 350 C on average of 244
ms and the igniters from set 15 hit 350 C on average of 33 ms. This major difference in time is
due to the different resistance value. Set 13 had an average resistance of 6.37 ohms; where as set
15 had an average resistance of 2.95 ohms. Although this is not enough data to find a clear
trend, it does suggest that a lower resistance, like the target 1.0 ohms, would likely hit 350 C
within 20 ms.
12
All Fire Test at 3 A
600
550
500
450
Temperature (C)
400
350
#13-2
#13-3
#13-5
300
250
200
150
100
50
0
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
Time (s)
(a)
All Fire at 3 A
650
600
550
500
450
Temp (C)
400
350
15-7
15-8
300
250
200
150
100
50
0
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
1.100
Time (s)
(b)
Figure 10: All fire tests at 3 A for 3 igniters from set 14 (a) and 2 igniters from set 15 (b)
Four Point Probe Calibration
In order to get more accurate thickness measurements from the 4 pt. probe, it was decided that
the formula used to compute thickness should be investigated. The formula used to compute
thickness is:
t = ρ*V/(I*F)
13
where ρ is the resistivity of the material being measured, V is the voltage from the 4 pt. probe, I
is the current from the 4 pt. probe, and F is a correction factor. In previous calculations we have
used 4.53 for F. This F number though, was found to be based on the assumption that we were
using the 4 pt. probe in the middle of a large sample. A more accurate correction factors was
found in a paper by Schwartzendruber. The correct factor used depends on the ration between
the size of the 4 pt. probe and the sample size. Figure 11 is a comparison of a wafer’s thickness
measurements with and without the proper correction factor. From the comparison, it shows a
slight change in the distribution pattern, but the thicknesses remain the same.
Wafer 4 Thickness (microns)
9
8
7
6
5 Row
4
3
2
1
1
2
3
4
5
6
7
8
9
1.5-1.55
1.45-1.5
1.4-1.45
1.35-1.4
1.3-1.35
1.25-1.3
1.2-1.25
1.15-1.2
1.1-1.15
1.05-1.1
1-1.05
0.95-1
0.9-0.95
0.85-0.9
0.8-0.85
Column
(a)
Wafer 4 Thickness Profile - Corrected
9
8
7
6
5Row
4
3
2
1.5-1.55
1.45-1.5
1.4-1.45
1.35-1.4
1.3-1.35
1.25-1.3
1.2-1.25
1.15-1.2
1.1-1.15
1.05-1.1
1-1.05
0.95-1
0.9-0.95
0.85-0.9
0.8-0.85
1
1
2
3
4
5
Column
6
7
8
9
(b)
Figure 11: Comparison on wafer thickness without (a) and with (b) the proper correction factor
14
AFM
With concern of the sputtering machine not providing the desired thickness and that the 4 pt.
probe was not giving the exact thickness measurements, the Atomic Force Microscope (AFM)
was tested on various samples for a thickness measurement. What the AFM does is scans a
region with a fine tipped vibrating probe. The alterations of the movement of the probe due to its
interaction with the surface are recorded to produce a topographical map of the region scanned.
The topographical map can then be analyzed with the software to find the thickness. Initially the
AFM was used to measure the thickness on a supposed 3 micron thin film that was sputtered
with a set of igniters. The AFM did show a thickness of about 3 microns. The AFM was then
used on a few of the sputtered wafers sent by Odyssian. Measuring the edges formed from the
tabs that held down the wafer during sputtering, the AFM measurements were taken and
compared to data from the 4 pt. probe, Table 3.
Table 3: Comparative results from the 4 pt. probe and the AFM thickness measurements
4 pt. probe
AFM Ave.
Difference
AFM Range
(μm)
(μm)
(μm)
% Error
(μm)
Wafer 1
Tab 1
Side 1
0.862187
0.8965
0.034313
3.902
0.191
Side 2
0.826324
0.8510
0.024676
2.942
0.252
Tab 2
Side 1
0.845684
0.8700
0.024316
2.835
0.214
Side 2
0.912596
0.9345
0.021904
2.372
0.191
Wafer 4
Tab 1
Side 1
1.118226
1.1610
0.042774
3.753
0.338
Side 2
1.005439
1.0460
0.040561
3.954
0.348
Tab 2
Side 1
1.023671
0.9895
0.034171
3.395
0.301
Side 2
1.127259
1.1650
0.037741
3.293
0.27
As seen in the table of data comparing the 4 pt. probe thickness measurements with the AFM, the
difference is only 2 to 4%, which is the operation error of the equipment. The important factor to
note is the range of the data from the AFM. The measurements from the AFM images are based
on user input, thus an average number of measurements were used to determine the thickness.
Along with a large range of thickness measurements, the AFM is easily effected by minor
vibration from anywhere around the room. These vibrations can produce a larger error. With
more accurate scans taking upwards of 10 minutes each, extraneous vibrations will likely effect
part of the scan. Figure 12 shows the accuracy of the AFM and the effects of vibrations. Finally,
the AFM requires a gradual edge to measure thickness within its scanning area of 100 x 100 μm.
Because of these factors and showing that the 4 pt. probe provides similar results, the 4 pt. probe
will be the dominate method for measuring thickness.
15
Figure 12: An example of a nice clear edge and an example of different vibration effects on an image
Sputtering Conditions
Table 4 lists the sputtering conditions of the three sets of 3 micron thin film igniters that are used
for the various tests in this report.
Wafer ID
Igniter 13
Igniter 14
Igniter 15
Table 4: Sputtering conditions of the igniter sets described in the report
Start
End
Start
End
Base
Power
Deposition
Material
Voltage Voltage Current Current Pressure
(W)
Rate (A/s)
(V)
(V)
(A)
(A)
(Torr)
Ni/Cr 80/20 300
449
392
0.669 0.771 5.0*10^-5
4.3
Ni/Cr 80/20 300
334
321
0.896 0.945 2.7*10^-5
2.8
Ni/Cr 80/20 300
591
505
0.505 0.594
?
5.1
Final
Time
Thinkness
(min)
(kÅ)
125
30.03
194
30.01
96.5
30.01
Each set has very different resistance values, but from these sputtering conditions, it is unclear
what factors cause the large range of resistance values.
SEM Images
With the igniters not producing the desired resistance, each igniter is viewed with the Scanning
Electron Microscope (SEM) to verify that there is no adhesion or other unknown cause to the
higher resistance values. All sets described in the various sections shown no unique
characteristics. With the testing of different etching methods to remove the thin film from used
igniters, the results from each of these different etching methods are also viewed with the SEM.
The SEM images can show which method best removes the thin film and causes the least amount
of excess damage. As seen in the images of Fig. 12, etching the igniter for too long can cause
excess damage to the contacts, which could affect adhesion when applying a new thin film.
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Figure 13: SEM images showing an effective etching process and the effect of etching for too long
Finally, the SEM was used to provide dimensions of the igniter needed for modeling and a range
of hole sized in the glass substrate to predict the effectiveness of filling them with ERA3, Fig.
14.
Figure 14: SEM images to find the dimensions of igniter and a range of sizes for holes in the glass substrate
Polishing
In a desire to be able to reuse old igniters that had burned out in past experiments, a chemical
etching process was tried using a nitrogen hydrochloric acid mix. Although this process did
remove the thin film, it also caused a great deal of oxidation of the steel casing. Thus an
alternative method was pursued in order to prepare igniters for reuse – polishing.
In total, six igniters were polished and these igniters were labeled as P1 through P6. An optical
microscope of the Sony Technolook TW-TL10S variety that is capable of zooming in 100x was
used to examine the igniters during each step of the polishing process. The nichrome film was
polished off in three steps – all steps involved hand polishing. The method for hand polishing is
to hold the surface of the igniter level against the pad as it rotates, and move the surface in figure
eights on the pad as it spins. First a polishing pad of 400 grit size was used until it was observed
that the bulk of the nichrome was removed, meaning until no nichrome was visible to the naked
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eye but little specks were visible under the microscope. An 800 grit size pad was then used for
five minutes, followed by a 1200 grit size pad for ten minutes. All six igniters were polished in
this way.
After polishing, optical microscope images were taken. Figure 15 is an image of igniter P1. In
the bottom right corner is a contact and appears to be a crack. Also present on the igniter surface
are numerous divots. These types of features were common to all six igniters.
Figure 15: Image of igniter P1 after the 3 polishing steps
In order to get a more uniform thin film for deposition, it was decided that ERA 3, a silicate with
glass like properties, should be deposited onto the igniters to fill the cracks and divots. ERA 3
was spun onto the igniters in the manner listed in Table 5:
Table 5: Spinning times of ERA3 on various polished igniters
Spinning Setting
Spinning Time
Igniter
(ERA3)
(ERA3)
P1
Full Speed
30 seconds
P2
Full Speed
60 seconds
P3
Full Speed
30 seconds
P4
Full Speed
45 seconds
P5
Full Speed
45 seconds
P6
Full Speed
60 seconds
After spinning on the ERA 3, the igniters were allowed to dry for at least 24 hours before they
were polished again. A 1200 grit pad was used until the contacts were exposed, and then a 0.1
micron pad followed by a 0.05 micron pad was used with the times listed in Table 6.
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Igniter
P1
P2
P3
P4
P5
P6
Table 6: Polishing times of the ERA3 on the igniters
2nd Polishing Time (.1
2nd Polishing Time (.05
micron)
micron)
5 minutes (additional 10
20 minutes (additional 10
minutes)
minutes)
18 minutes
20 minutes
10 minutes
20 minutes
10 minutes
15 minutes
10 minutes
15 minutes
10 minutes
15 minutes
After applying ERA3 and polishing the igniters, images were again taken with the optical
microscope for comparison with the pictures that were taken of the igniters with no ERA3, which
comparative images are shown in Fig. 16.
(a)
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(b)
Figure 16: Comparison images of igniter P4 before (a) and after applying and polishing (b) the ERA3
As can be seen in the pictures above, the deposition of ERA 3 has improved the quality of the
surface by filling in much of the crack and divots. This result was consistent for all six igniters.
Future Plans
One of the requirements for the igniters is that they pass a temperature cycling test between -50
and 135 °F, by maintaining their properties at these two temperature extremes. We plan on
testing this capability with a Sauders and Associates 4210 A Test Chamber.
This test chamber has the ability to cycle between temperatures between -65 and 150°C; is
settable to a hundredth of a degree; and has an accuracy of +/- .1°C. Additionally, the test
chamber can be programmed such that it changes temperatures at a given rate, maintains a set
temperature for a given time, and runs such a program a given number of times. The chamber
also is equipped with the ability to run currents through multiple samples while they are
undergoing temperature transitions. Thus an entire batch of igniters can be tested together for
resistances changes at various temperatures.
Another plan is to test a set of 3 micron igniters that is a mixture of with and without ERA3 on
them. The results will be compared to see if this additional step will improve the adhesion and
overall performance of the igniters.
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