Evaluation of the Effects of 

Hydrogen Peroxide on Common 

Aircraft Electrical Materials

DOT/FAA/AM-10/5

Office of Aerospace Medicine

Washington, DC 20591

OK-10-0077-JAH

Sin Ming Loo, Josh Kiepert, Derek Klein, Michael Pook 

Boise State University

Boise, ID 83725

Shih-Feng Chou, Tony Overfelt

Auburn University

Auburn, AL 36849

Jean Watson

Office of Aerospace Medicine

Federal Aviation Administration

Washington, DC 20591

March 2010

Final Report

Federal Aviation

Administration
NOTICE

This document is disseminated under the sponsorship 

of the U.S. Department of Transportation in the interest 

of information exchange. The United States Government 

assumes no liability for the contents thereof.

___________

This publication and all Office of Aerospace Medicine 

technical reports are available in full-text from the Civil 

Aerospace Medical Institute’s publications Web site: 

www.faa.gov/library/reports/medical/oamtechreports
i 

Technical Report Documentation Page 

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 

DOT/FAA/AM-10/5 

4. Title and Subtitle 5. Report Date 

Evaluation of the Effects of Hydrogen Peroxide on Common Aircraft March 2010 

Electrical Materials 6. Performing Organization Code 

7. Author(s) 

Loo SM,1 Kiepert J,1 Klein D,1 Pook M,1 Chou SF,2 Overfelt T,2 Watson J3 8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

 11. Contract or Grant No. 

Co-Op Agrmt No. 07-CRITE-BSU 

 

1

National Air Transportation Center of Excellence for Research in the 

Intermodal Transport Environment 

Boise State University, Boise, ID 83725 

2

National Air Transportation Center of Excellence for Research in the 

Intermodal Transport Environment 

Auburn University, Auburn AL 36849 

3

Office of Aerospace Medicine 

Federal Aviation Administration 

Washington, DC 20591 

 

12. Sponsoring Agency name and Address 

Office of Aerospace Medicine 

Federal Aviation Administration 

800 Independence Ave., S.W. 

Washington, DC 20591 

13. Type of Report and Period Covered 

14. Sponsoring Agency Code 

15. Supplemental Notes 

Work was accomplished under Public law 108-76 

16. Abstract 

Aircraft can be contaminated with unwanted chemical or biological elements. For years, hydrogen peroxide 

has been used to disinfect equipment in the medical community. The diluted vapor form of hydrogen 

peroxide is being considered for use as a decontaminant/disinfectant/sanitizer of transportation vehicles 

aircraft, buses, subway trains, ambulances, etc. Previous work showed that STERIS Corporation’s Vaporized 

Hydrogen Peroxide (VHP®) technology could be used successfully in complex transportation vehicles. 

However, the compatibility of the process with typical aircraft avionics has not been established. This report 

documents a preliminary evaluation of the effects of hydrogen peroxide exposure on avionics (i.e., avionics 

wires, active circuit boards, and dummy circuit boards). 

 

17. Key Words 18. Distribution Statement 

Aircraft Avionics, Printed Circuit Board, VHP, 

High Voltage 

Document is available to the public through the 

Defense Technical Information Center, Ft. 

Belvoir, VA 22060; and the National Technical 

Information Service, Springfield, VA 22161 

 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 18 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 

iii 

Contents

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

METHODS AND MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Test Setup for Dummy Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Test Setup for Active Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Test Setup for Wires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

VHP® Decontamination Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Test Results for Dummy Circuit Boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Wire Board Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Interdigitated Board Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Pad Board Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Test Results for Active Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Test Results of Aviation Wires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Weight Change of Printed Circuit Boards and Wires . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Chemical Analysis of Aviation Wires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

v 

Abbreviations

As used in this report, the following abbreviations/acronyms have the meanings indicated

Abbreviation Meaning

BI . . . . . . . . . . . Biological Indicator

DSC . . . . . . . . . Differential Scanning Calorimetry

ppm . . . . . . . . . Parts Per Million 

RMS . . . . . . . . Root Mean Squared

VHP® . . . . . . . Vaporized Hydrogen Peroxide 

XPS . . . . . . . . . X-ray Photoelectron Spectroscopy 

1 

Evaluation of the Effects of Hydrogen Peroxide

on Common Aircraft Electrical Materials

INTRODUCTION

Among all of the large-scale disinfection and/or decontamination technologies available, vaporized hydrogen 

peroxide (VHP®)1

 is of particular interest due to its 

rapid sterilization, easy usage, intrinsic environmental 

friendliness (i.e. simple by-products composed of only 

water and oxygen), and compatibility with many materials 

and systems. VHP® technology has been investigated for 

possible usage in aircraft applications (1-4). These studies 

used vaporized hydrogen peroxide concentrations in the 

range of 150 - 600 ppm and cycle times of 80 - 120 min.

Maximum concentrations of hydrogen peroxide vapor 

were carefully controlled to avoid condensation in cool 

locations within the aircraft cabins. Although these studies 

did not evaluate the compatibility of the various cabin 

materials with exposure to vaporized hydrogen peroxide, 

analysis of the collected data showed that VHP® did not 

seem to have any visible effect on the materials (3).

A typical VHP® process cycle consists of an initial dehumidification step, then a conditioning phase followed 

by the actual sanitization/ decontamination process.

Finally, an aeration phase is employed to remove residual 

hydrogen peroxide vapor. During the dehumidification 

phase, warm, dry air flows into the enclosure to lower 

the relative humidity to less than 10%. This allows a 

higher concentration of hydrogen peroxide vapor to be 

injected into the enclosure without causing condensation. Hydrogen peroxide liquid concentrate (35% liquid 

H2

O2 with a pH ~ 3) is then flash vaporized and injected 

into the enclosure during the initial conditioning and 

sanitization/decontamination phases. The purpose of the 

conditioning phase is to rapidly increase the hydrogen 

peroxide concentration to minimize the overall cycle 

time. During the sanitization/ decontamination phase, 

a steady concentration of hydrogen peroxide vapor 

(typically 250 - 450 ppm) is maintained. This produces 

the desired sanitization/decontamination effect that is 

often measured by the 6-log kill (i.e., 106

 reduction) of 

a commercial biological indicator (BI) spore population 

of Geobacillus stearothermophilus. Once the sanitization/

decontamination phase is completed, the enclosure is 

aerated with fresh air while any residual hydrogen peroxide vapor breaks down into environmentally benign 

water and oxygen.

1 VHP is a registered trademark of STERIS Corporation, Mentor, 

OH, USA.

Many polymeric materials are known to be susceptible 

to absorption of moisture. The small water molecules 

diffuse into the polymer matrix and force apart the polymer macromolecules, causing swelling. Increases in the 

distance between the polymer chains reduce the strength 

of the secondary intermolecular bonds and increase the 

softness and ductility of the polymer. However, the 

highly cross-linked epoxies used in aerospace-grade fiber 

composites minimize moisture absorption. Thus, these 

materials exhibit good resistance to degradation in wet 

environments (5). While molecules of H2

O2 vapor should 

be absorbed even less by epoxies than H2

O molecules, the 

intermolecular cross-links might be degraded by oxidation from the hydrogen peroxide. The extensive usage 

of fiber/epoxy composites in aerospace structures and 

avionics dictates that the compatibility of these materials 

with hydrogen peroxide vapor be examined.

Although several similarities exist between the contents 

of this report and technical report entitled “Evaluation 

of the Effects of Hydrogen Peroxide on Common Aviation Structural Materials” (1), this document includes an 

analysis of VHP’s effect on avionics materials not found 

in the other report.

METHODS AND MATERIALS

The specific motivation for this work was to evaluate 

the compatibility of avionic materials. At the early stage 

of the work, multiple attempts were made to obtain used 

aircraft avionic printed circuit boards to test the VHP®

compatibility. The use of real aircraft avionic printed 

circuit boards was not pursued further due to the following reasons:

• History of the avionics: With used avionics, obtaining the operational history is difficult or impossible.

Thus, it would be nearly impossible to set up control 

cases for comparison.

• Difficulty in obtaining the test equipment: Assuming 

avionics were obtainable, the test equipment required 

to analyze the avionics was determined either to be 

impossible to obtain or too expensive.

Given these challenges, the decision was made to design 

dummy and active printed circuit boards. The dummy 

circuit board had no active components. The active board 

had operational components including voltage level 

converters, a microcontroller, resistors, capacitors, and 
2 

connectors. In addition to these boards, avionics wires 

were also used as test samples (see Figure 1).

Test Setup for Dummy Circuit Board

In order to study different characteristics, tests were 

performed on several different dummy circuit board layouts, active board, and aviation wire. The three dummy 

board layouts were wire, interdigitated, and pad. The wire 

board layout shown in Figure 1(a) was used to test the 

effects of VHP® on the impedance of traces. The interdigitated board layout shown in Figure 1(b) was used to 

test how VHP® affected the impedance between traces.

The pad board layout shown in Figure 1(c), was used to 

test the effects of VHP® on pad impedance. A board with 

active component (microcontroller) was designed to test 

the effect of VHP® (Figure 1(d)). Aviation wire was also 

used in our tests (Figure 1(e)). A HP4263B Inductance, 

Capacitance, and Resistance (LCR) meter (Figure 2) was 

used to measure the impedance of the traces on each 

board. For the wire boards, the impedances of all 16 traces 

were measured at 100mV, 1kHz. For the interdigitated 

boards, the impedances were measured at 100mV, 1kHz, 

and 10kHz. For the pad boards, the impedances were 

measured at 100mV, 1kHz. Figure 2 shows the test setup.

The resistance of the wires was measured and subtracted 

from the trace measurements to obtain the impedance 

of the traces themselves.

Results from the research indicated that a conformal 

coating is normally applied to avionics circuit boards.

Therefore, some of the samples were coated with 1B31 

acrylic coating (HumiSeal Protective Coatings; Woodside, 

NY.) Multiple tests were performed for each board layout 

(uncoated, uncoated-VHP® exposed, conformal coated, 

and conformal coated-VHP® exposed).

Test Setup for Active Circuit Board

To test the active boards, sine and square waves 

were generated by the active boards to verify the signal 

output capabilities. As the active circuit was digital 

in nature, the square wave output could be directly 

generated. The sine wave signal was generated through 

pulsewidth-modulation and a filter circuit. The signals 

for the unexposed boards and the VHP® exposed boards 

were recorded and compared by using an oscilloscope.

Figure 3 shows the testing circuit for sine wave and square 

wave acquisition from the active board.

For input acquisition tests on the active boards, a 

function generator was configured to output a sine 

Figure 2: Test Setup for Dummy Boards 

Figure 3: Active Circuit Output Configuration 

 

(a) (b) 

 

(c) (d) 

 (e) 

Figure 1: Wire Board (Fig. a), Interdigitated 

Board (Fig. b) [6], Pad Board (Fig. c), Active 

Board (Fig. d), and Aviation (MILSPEC) Wire 

(Fig. e) 

Figure 1: Wire Board (Fig. a), Interdigitated 

Board (Fig. b) [6], Pad Board (Fig. c), Active 

Board (Fig. d), and Aviation (MILSPEC) Wire 

(Fig. e)
3 

wave or square wave, which would be captured with the 

analog-to-digital converter present in the active circuit 

board (microcontroller). Figure 4 shows the circuit used.

Test Setup for Wires

To test for any potential degradation of the aviation wire 

insulation (MIL227597/34-20), a high-voltage power 

supply and current measuring electronics were set up to 

apply high-voltage stress to the insulation (Figure 5). This 

was done in to determine the effect of VHP® exposure 

on the time-to-breakdown of the wire insulation. In this 

set of tests, ~18.5 KV RMS at 60 Hz was applied to ~1 

ft sections of aviation wire. One terminal was connected 

to one end of the wire with the insulation intact. The 

other terminal was connected to the wire’s conductor. The 

high-voltage power supply system kept a record of when 

the insulation breakdown occurred (VHP®- exposed wires 

versus non-VHP® exposed wires). Twenty samples were 

tested for both exposed and non-exposed 

wires. Breakdown was detected by the 

current spike associated with the resulting 

short circuit.

VHP® Decontamination Processes

The printed circuit board and aviation 

wire specimens were subjected to 25 VHP®

cycles and 10 VHP® cycles of decontamination processes, respectively. The cycles were 

designed to increase the aggressiveness of 

the decontamination environment where the chamber 

concentration was maintained at 450 ppm, and the inlet 

concentration was ~ 2000 ppm. Each cycle lasted for a 

total of 6.5 hrs, and the decontamination phase was held 

to 4.5 hrs. During the exposure of vaporized hydrogen 

peroxide, the printed circuit boards were placed on a stainless steel rack with the circuits facing upward to achieve 

the maximum contact to the vapor. The aviation wire 

samples were detached from a coil form and stretched 

out randomly inside the VHP® chamber to avoid surface 

contact between materials, which provided maximum 

exposure to the vapor.

RESULTS AND DISCUSSION

Test Results for Dummy Circuit Boards

In this study, each of the Dummy circuit board layouts was divided into two categories: conformal coated 

and non-coated. Within each category, only half of the 

samples were exposed to VHP®.

Wire Board Results

The average resistance of the long, medium, and 

short length traces was about 11, 8, and 7 MOhms, 

respectively (Figure 6 and Tables 1 to 4). The results had 

a small standard deviation across all measurements less 

than 0.01 MOhms. From the measurements, the longer 

traces had slightly more resistance than the shorter ones, 

but there was only about a 1 MOhm difference between 

the non-exposed versus exposed boards. This difference 

is so small that it would not affect the DC characteristics 

of the traces.

Interdigitated Board Results

The impedance between the traces was measured on the 

interdigitated board. Since the traces were unconnected, 

they behaved like a capacitor with air as the dielectric. As 

a result, the magnitude of the impedance measured was 

large (in the MOhm range), and the standard deviation 

was also large (on the order of 100-500 kOhms) (Tables 

5 to 8, Figures 7 to 10). The plots in the figures above 

clearly show that the impedance does change on the order 

Figure 4: Active Circuit Input Configuration 

Figure 5: VHP Wire Insulation Stress Configuration 

Figure 6: Wire Board Trace Resistance Summary 
4 

Table 1: Uncoated & Unexposed Impedance 

Uncoated

Avg Stdev

Long Mag (Ohms) 0.011 0.0015

Long Phase (Deg) 0.008 0.0041

   

Short Mag (Ohms) 0.007 0.0011

Short Phase (Deg) 0 0.0018

   

Med Mag (Ohms) 0.008 0.0017

Med Phase (Deg) 0.004 0.005

Table 2: Uncoated & Exposed Impedance 

Uncoated‐Exposed

Avg Stdev

Long Mag (Ohms) 0.01 0.0044

Long Phase (Deg) 0.008 0.0041

Short Mag (Ohms) 0.007 0.0013

Short Phase (Deg) 0.002 0.0038

Med Mag (Ohms) 0.008 0.0019

Med Phase (Deg) 0.005 0.0051

Table 3: Coated & Unexposed Impedance 

Coated

Avg Stdev

Long Mag (Ohms) 0.01 0.0017

Long Phase (Deg) 0.008 0.0038

Short Mag (Ohms) 0.006 0.0014

Short Phase (Deg) 0.001 0.0035

Med Mag (Ohms) 0.007 0.0015

Med Phase (Deg) 0.004 0.005

Table 4: Coated & Exposed Impedance 

Coated‐Exposed

Avg Stdev

Long Mag (Ohms) 0.01 0.0019

Long Phase (Deg) 0.009 0.0055

Short Mag (Ohms) 0.006 0.0012

Short Phase (Deg) 0.001 0.0031

Med Mag (Ohms) 0.008 0.0017

Med Phase (Deg) 0.003 0.0053

Table 5: Interdigitated Uncoated-Unexposed Impedance 

Frequency 1KHz    10KHz

Traces 1 & 2 1 & 3 3 & 5 4 & 5    1 & 2 1 & 3 3 & 5 4 & 5

Mag Avg 3.75E+07 4.23E+07 4.18E+07 3.73E+07    3.77E+06 4.22E+06 4.28E+06 3.80E+06

Mag StdDev 4.67E+05 5.85E+05 2.45E+05 4.93E+05    2.65E+04 3.44E+04 3.32E+04 4.51E+04

Phs Avg ‐89.35 ‐89.24 ‐89.49 ‐89.04    ‐89.46 ‐89.44 ‐89.48 ‐89.44

Phase StdDev 0.26 0.47 0.33 0.37    0.09 0.05 0.04 0.05

Table 6: Interdigitated Uncoated-Exposed Impedance 

Frequency 1KHz    10KHz

Traces 1 & 2 1 & 3 3 & 5 4 & 5    1 & 2 1 & 3 3 & 5 4 & 5

Mag Avg 3.80E+07 4.28E+07 4.21E+07 3.79E+07    3.79E+06 4.21E+06 4.32E+06 3.83E+06

Mag StdDev 2.95E+05 3.83E+05 9.11E+05 4.85E+05    3.21E+04 5.77E+04 3.63E+04 3.74E+04

Phs Avg ‐89.82 ‐89.76 ‐89.74 ‐89.9    ‐89.58 ‐89.52 ‐89.6 ‐89.56

Phase StdDev 0.08 0.17 0.11 0.07    0.04 0.04 0 0.05
5 

Table 7: Interdigitated Coated-Unexposed Impedance 

Frequency 1KHz    10KHz

Traces 1 & 2 1 & 3 3 & 5 4 & 5    1 & 2 1 & 3 3 & 5 4 & 5

Mag Avg 3.66E+07 4.11E+07 4.02E+07 3.62E+07    3.65E+06 4.04E+06 4.14E+06 3.68E+06

Mag StdDev 3.44E+05 1.92E+05 1.95E+05 3.70E+05    4.83E+04 5.50E+04 2.17E+04 1.64E+04

Phs Avg ‐89.7 ‐89.76 ‐89.66 ‐89.76    ‐89.5 ‐89.5 ‐89.5 ‐89.5

Phase StdDev 0 0.09 0.13 0.13    0 0 0 0

Table 8: Interdigitated Coated-Exposed Impedance 

Frequency 1KHz    10KHz

Traces 1 & 2 1 & 3 3 & 5 4 & 5    1 & 2 1 & 3 3 & 5 4 & 5

Mag Avg 3.68E+07 4.15E+07 4.10E+07 3.65E+07    3.67E+06 4.08E+06 4.16E+06 3.70E+06

Mag StdDev 3.08E+05 4.93E+05 4.88E+05 3.58E+05    3.11E+04 7.05E+04 5.15E+04 2.55E+04

Phs Avg ‐89.72 ‐89.7 ‐89.78 ‐89.76    ‐89.5 ‐89.5 ‐89.5 ‐89.5

Phase StdDev 0.04 0.14 0.18 0.13    0 0 0 0

Figure 7: Interdigitated Z Magnitude, 1KHz Figure 8: Interdigitated Z Magnitude, 1KHz 

Figure 9: Interdigitated Z Phase, 1KHz Figure 10: Interdigitated Z Phase, 10KHz 
6 

of about 2 MOhms with respect to the various coatings 

and exposures. The largest change was between the coated 

and uncoated-exposed boards, which had a 1.46 MOhm 

difference. This was most likely caused by the coating 

affecting the capacitance of the traces. Compared to the 

standard deviation of about 0.5 kOhms, this difference is 

insignificant to the performance of the traces. At 10kHz, 

a similar trend, followed with the values being scaled 

down by a factor of 10. The phase between the traces 

had small changes that were insignificant with respect to 

their performance.

Pad Board Results

The pad board resistance had a maximum difference 

of approximately 2 MOhms between the uncoated and 

uncoated-exposed boards (Table 9 and Figure 11). Since 

the standard deviation was about 1 MOhm, this change 

was insignificant.

In summary, the results indicated that there were no 

statistical differences between the boards that were exposed 

to VHP® and those that were not exposed. These tests 

were carried out on boards without solder mask. Solder 

mask (as is found on a typical PCB) would have provided 

another layer of protection against corrosion. The Auburn 

team found that a very thin layer of copper oxidation 

was present on the tested boards. However, some oxidation due to air exposure would have occurred on these 

unprotected boards even without the presence of VHP®.

Test Results for Active Board

As is clear from the figures (Figures 12 to 27), the 

pre-and post-generated/measured waveforms were 

found to match with only minor deviations that may 

be attributed to expected noise. The input and output 

signals of unexposed boards and VHP® exposed boards 

were compared. No statistical difference was found, and 

the ability of the active boards to output or acquire signals was not found to be diminished in any way by the 

exposure to VHP®. However, oxidation was visible on 

unprotected tin contacts.

Test Results of Aviation Wires

Figure 28 shows the results. Wires not exposed to 

VHP® failed within 16 minutes on average. The wires 

that were exposed to VHP® failed on average within 4 

minutes. This indicates that VHP® did change the dielectric strength of the wire insulation. However, in the 

interest of increasing the speed at which the breakdown 

would occur, the voltage stress applied was outside the 

operational voltages experienced by aviation wire. The 

Table 9: Pad Boards Impedance Results 

Uncoated Uncoated­Exposed

   Avg Stdev    Avg Stdev

Mag (Ohms) 0.764 0.002 Mag (Ohms) 0.762 0.001

Phase (Deg)  ‐0.08 0 Phase (Deg) ‐0.081 0.003

Coated Coated­Exposed

   Avg Stdev    Avg Stdev

Mag (Ohms) 0.763 0.002 Mag (Ohms) 0.763 0.001

Phase (Deg)  ‐0.08 0 Phase (Deg) ‐0.08 0

Figure 11: Pad Board Resistance Summary 
7 

Figure 12: 01 - Acquisition Sine Wave, 485mHz, 

2.0Vpp, 1.5V DC offset (unexposed) Figure13: 01 - Acquisition Square Wave, 485mHz, 

2.0Vpp, 1.5V DC offset (unexposed) 

Figure 14: 01 - Output Sine Wave (Unexposed) Figure 15: 01 - Output Square Wave (Unexposed) 

Figure16: 02 - Acquisition Sine Wave, 485mHz, 

2.0Vpp, 1.5V DC Offset (10@2000ppm) 

Figure 17: 02 - Acquisition Square Wave, 485mHz, 

2.0Vpp, 1.5V DC offset (10@2000ppm) 
8 

Figure 18: 02 - Output Sine Wave (10@2000ppm) Figure 19: 02 - Output Square Wave (10@2000ppm)

Figure 20: 03 - Acquisition Sine Wave, 485mHz, 

2.0Vpp, 1.5V DC offset (10@2000ppm) 

Figure 21: 03 - Acquisition Square Wave, 485mHz, 

2.0Vpp, 1.5V DC offset (10@2000ppm)

Figure 22: 03 - Output Sine Wave (10@2000ppm) Figure 23: 03 - Output Square Wave (10@2000ppm) 
9 

Figure 28: Results of Pre-VHP® and Post-VHP® Aviation Wire Tests

Figure 24: 04 - Acquisition Sine Wave, 485mHz, 

2.0Vpp, 1.5V DC offset (1@2000ppm)

Figure 25: 04 - Acquisition Square wave, 485mHz, 

2.0Vpp, 1.5V DC offset (1@2000ppm)

Figure 26: 04 - Output Sine Wave (1@2000ppm) Figure 27: 04 - Output Square Wave (1@2000ppm) 
10 

stress voltage was ~18.5 KVRMS for these tests, whereas 

the normal aircraft operating voltage is 28 Volts at 400 

Hz. The next set of tests will be carried out at voltages 

closer to the operational range.

Weight Change of Printed Circuit Boards and 

Wires

Weight change on the specimens due to the exposure 

of hydrogen peroxide was measured precisely before and 

after the VHP® process, and the results are shown in Table 

10. In summary, the results indicated that there were no 

statistical differences in weight change among the boards 

and aviation wires that were exposed to VHP® and those 

that were not exposed.

Chemical Analysis of Aviation Wires

Chemical analyses on the printed circuit boards and 

aviation wire insulation (MIL227597/34-20) were performed by Raman spectroscopy. This process used an 

Invia Confocal Raman Microscope with a 514.5 nm 

wavelength and 1 mW laser excitation source. The Spectra 

were recorded using a 50x objective lens which generated 

a 1 μm laser spot. Additional examination of the surface 

composition of copper layer on the test boards was accomplished using X-ray photoelectron spectroscopy (XPS) 

and Auger electron spectroscopy. The glass transition 

temperature of the wire insulation layer was measured 

by differential scanning calorimetry (DSC). Complete 

chemical analyses of the epoxy resin on the FR4 board 

and the acrylic coating using Raman Spectroscopy can 

be found in the previous report of effects of hydrogen 

peroxide on common aviation structural materials (1).

Figure 29 shows the results from Auger electron spectroscopy on the copper layer of the print circuit boards.

The major peaks include Cu, O, and C. No significant 

chemical changes were found even after 25 VHP® cycles.

XPS results (Figure 30) on the copper layer revealed small 

surface changes on the sample exposed to 25 VHP® cycles.

The binding energy between 2p1/2 and 2p3/2 increased 

slightly from 19.4 eV to 20.3 eV. This increase is an 

indication of an increase in the presence of CuO. Upon 

closer inspection of the 2p3/2 peak, one can see that only 

CuO feather is present (see the 25 VHP® cycle data in 

the magnified image in Figure 30). Table 11 shows the 

surface elemental composition for the control and exposed 

specimens. The percentage of oxygen atoms increased 

Table 10: Percentage Weight Change of the Print Circuit Boards and Aviation Wire 

After VHP® Treatment 

Percentage Weight Change (Standard Deviation), % 

Uncoated Coated Specimen Pad Wire Interdigitated Pad Wire Interdigitated 

Aviation 

Wire 

 -0.04 

(0.01) 

-0.06 

(0.01) 

-0.07 

(0.01) 

-0.03 

(0.01) 

-0.05 

(0.02) 

-0.07 

(0.01) 

0.07 

(0.01) 

Figure 29: Auger Electron Spectroscopy of Copper on the Print Circuit Boards 
11 

Table 11: Surface Elemental Composition of the 

Print Circuit Board by XPS 

 Surface Elemental Composition 

(atom %) 

Specimen Cu O C N Cl Sn 

Control 14 27 52 1 5 1 

25 VHP® 11 41 45 0 0 3 

Figure 30: XPS of the Copper Layer on the Print Circuit Board. Insert 

Shows the 2p3/2 Peak 

Figure 31: Raman Spectra of the Insulation Layer on the Aviation Wire 

from 27 % for the control sample 

to 41 % for the exposed sample, and 

the presence of Cl and Sn was due 

to surface contamination.

Results from the Raman spectroscopy of aviation wire insulation 

(MIL227597/34-20) are shown in 

Figure 31. Extraction of the characteristic bands from the insulation 

material was difficult, because the 

surface of the insulation layer contains chemicals that raise the fluorescence noise (curving background).

To accomplish the extraction, data 

were collected from eight tests 

and normalized using a fifth-order 

polynomial. Peaks at 1445 cm-1 and 

2970 cm-1 were assigned to CH2

and CH vibration, respectively (7, 

8). Additionally, the CF vibration band was observed 

at 840 cm-1 as shown in the magnified image in Figure 

31. These characteristic bands did not show any shift at 

their corresponding wave numbers, and no extra peaks 

were found after 10 VHP® cycles. DSC results (shown in 

Figure 32) indicated that the glass transition temperature 

of the wire insulation remained unchanged for specimens 

exposed to 10 VHP® cycles. Having the same glass transition temperature in the two samples means that there were 

no bond changes (chemically) that allowed the polymer 

chains to start moving/vibrating at the transition between 

the glassy state and the rubbery state.
12 

CONCLUSIONS

The above results have lead to the development of 

several important conclusions. First, VHP® exposure 

had no affect on the circuit boards. The discoloration of 

the copper boards would have occurred even in ambient 

environmental conditions. Furthermore, resistance and 

impedance readings were recorded at different frequencies. The results showed no statistical differences between 

the boards exposed to VHP® and those not exposed to 

VHP®. Also, for the active circuit boards, the input and 

output signals for the same board before and after VHP®

exposure showed only minor differences. These variations 

could easily be the result of circuit noise. As for the aviation wires, the data indicate that the fail time of exposed 

wires was noticeably shorter (on average). However, the 

voltage used for the tests was determined to be above any 

realistic level. As of this writing, additional tests are being 

conducted at more realistic voltage levels. Finally, for the 

weight change and chemical analysis, the results indicated 

that there were no statistical differences in weight change 

and no degradation/oxidation chemically between the 

boards and wires that were exposed to VHP® and those 

that were not exposed.

Figure 32: DSC Diagram of the Insulation Layer on the Aviation Wire 

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