Third Harmonic Measurement in Printed Electronics
A. Samano, Dr. Y. Xu* and Prof. D. Harrison
Dr. C. Hunt , M. Wickham and Dr. O. Thomas
School of Engineering and Design, Brunel University,
Kingston Lane, Middlesex, UB83PH, United Kingdom
yanmeng.xu@brunel.ac.uk
Electronics Interconnect, National Physical Laboratory
Teddington TW110LW, United Kingdom
Abstract— The purpose of this research paper is to investigate
the defects detecting technique in printed electronics by the third
harmonic measurements. Various types of defects were
introduced on the samples and the third harmonic signal was
measured using a component linearity tester (Radiometer CLT1).
The relationship between the defects in the printed samples and
the third harmonic signal and the third harmonic ratio was
identified.
Keywords—reliability testing, defect detection, third harmonic
index, printed electronics
I. INTRODUCTION
Printed Electronics has become popular because of its
capability to be manufactured at low cost, low temperature
and at high throughput. Printing of conductive ink requires
chemical and liquid additives in order to transport the material
into a desired location. During the process of printing, the ink
is susceptible to damage because of its liquid state. The
printed structure can easily be damaged with little force or
contact. Printed electronics can be scratched and perforated by
contaminants during printing and curing.
Third harmonic has been used as a realibility tester in
resistor manufacturing industry. The test is used primarily by
resistor manufacturing industry to detect inhomogenous
defect, improper or high resistive contacts [1]. Previous
research work has applied third harmonic measurement to
capacitors [2] and semiconductors [3] to determine the
components reliability and to prevent the early operation
failure of the devices. In this study, the third harmonic
measurement has been performed by applying a pure
sinosoidal signal and the generated third harmonic signal was
detected and measured. The results shows that the defective
samples can produce higher third harmonic signal. The test
procedure is included in the IEC 60440 standard [4] that
requires the application of first harmonic frequency and the
measurement of the generated third harmonic signal
consequently. The definition of Third Harmonic Ratio (THI) is
the ratio between the fundamental frequency and the sum of
harmonic signal generated by the sample. The third harmonic
is chosen because it is time consuming to measure all the
harmonics, and it is enough to represent the remaining
harmonics [4]. The formula in calculating the third harmonic
ratio is given by the following equation [5]:
𝐕
𝑻𝑯𝑹 = 𝟐𝟎𝒍𝒐𝒈 𝐕𝟏
𝟑
where, THR is the third harmonic ratio, 𝑉1 is the input voltage
at fundamental frequency and 𝑉3 is the third harmonic signal
generated by the sample tested.
II. EXPERIMENT DESIGN AND METHODOLOGY
ED4000 carbon filled ink and ED3000 silver filled ink was
sourced from Electrapolymer. ED3000 was used as predeposited electrodes while ED4000 was used to create the test
structure. The printed electronics was cured according to the
manufacturing requirements. Various types of defects were
mechanically induced on the printed electronics. The pin-hole
defects were introduced using a center punch; the line defects
across the test structure were created by a scalpel; and two
grams of ground medium density fibers were added into 15
grams of the ED4000 ink in order to obtain contaminated
printed sample. All of the conductive pastes were printed
using screen printing technique. Measurements were
performed on all the following different samples: fully cured
samples, scratched samples, the sample contaminated with
fibers, under cured sample (ambient) and 1 k resistor.
Radiometer CLT1 was used to measure the third harmonic
frequency of the printed electronics. The equipment was
operated at 10 kHz frequency and the third harmonic was
measured at 30 kHz. The samples were optically examined
using Alicona Infinitefocus 3D surface measurement.
III. RESULTS AND DISCUSSION
Figure 1 shows an example of a pin-hole defect created on
the printed electronics. Three indentations have been created
with the following diameters: 607, 545 and 516  5 m.
Fig. 1.
Brunel University and National Physical Laboratory - PhD studenship in
Metrology of Printed Electronics.
*Corresponding author.
(1)
3D image of a pin-hole defect.
Figure 2 to 4 show three different sizes of single line
scratch defects cut over the tested structure with various
width. Figure 2 is the defect of 0.40  0.01 mm over 2.37 
0.01 mm width of the tested structure which is equivalent to
17 % of the structure. Figure 3 is the defect of 0.97  0.01 mm
over 2.26  0.01 mm width of the tested structure which is
equivalent to 42% of the structure. Figure 4 is the defect of
1.45  0.01 mm over 2.04  0.01 mm width of the tested
structure which is equivalent to 71% of the structure.
Figure 5 shows total of 9 line scratches made alternatively
on the two sides of the tested structure. Several scratches were
cut across the test structure, however, the remaining
conductive path was maintained for at least 50% of the
structure.
Fig. 5.
Fig. 2.
17% defect across the tested structure.
Fig. 3.
42% defect across the tested structure.
Fig. 4.
71% defect across the tested structure.
9 alternating line defects across the tested structure.
Figure 6 is the measurement results of the third harmonic
on the printed structure for all the samples with different
defective conditions. It shows that at higher input voltage the
alternating defects with 9 alternating line cuts across the tested
structure generated distinguished higher third harmonic signal
compared with all the other samples with various condition of
defects or non-defects, and the higher the input voltage the
larger the difference of the third harmonic measurement. It can
be seen that all the samples with different defective conditions
produced an increasing third harmonic signal in line with the
increase of input voltage.
A summary of the THR measurements is shown in Table I.
It can be found out that the initial value of 114 dB for the fully
cured printed electronics decreased when more defects were
introduced. The pin-holes have the least effect on the THR
value, followed by the increasing percentage of defects across
the tested structure. The alternating defects with the total nine
cuts across the tested structure have produced the largest third
harmonic signal thus the smallest THR. Therefore, a number
of cuts across the tested structure will generate more harmonic
signal than a single cut defect. The individual pin-hole defect
also generated third harmonic signal enough to differentiate it
from the fully cured printed electronics. The third harmonic
measurement comparison between fully cure printed
electronics and commercially available 1 k resistor which is
produced through high vacuum deposition, showed that the
printed electronics produces higher third harmonic signal as
compared to high vacuum deposition process. The printed
electronics samples containing fibers or under cured (ambient)
produced higher THR and lower third harmonic signal than
the fully cured samples. This was due to the response of the
contaminants to the AC test frequency applied. Therefore, the
Third harmonic Measurement is not suitable to detect this type
of defects.
REFERENCES
[1]
[2]
[3]
[4]
[5]
Fig. 6.
Third harmonic measurements.
TABLE I. THR MEASUREMENTS
Printed
Electronics
THR (dB)
THR difference to
fully cured (dB)
Fully cured
114.0
Pin holes
113.2
0.8
17 % Defect
112.2
1.8
42 %Defect
112.6
1.2
71 %Defect
110.5
3.5
Alternating
92.6
21.3
Fibers
114.6
-0.6
Ambient
116.3
-2.3
1 k
121.2
-7.3
IV. CONCLUSION
The third harmonic measurement is capable of detecting
defects in the printed electronics such as scratches or pin-hole
defects. However, it cannot detect contamination such as
fibers and under cured printed electronics due the response of
the contaminants to the AC test frequency. The fully cured
printed electronics will generate higher third harmonic signal
compared to the commercially available 1 k resistor.
A. Salomon and T. Troianello, "Component Linearity Test Improves
Reliability Screening Through Measurement of Third Harmonic
Index." pp. 69-76, 1973.
L. Spiralski, L. Hasse, K. Rogala and J. Turczyński, "Production testing
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E. P. Vandamme and L. K. J. Vandamme, "Current crowding and its
effect on 1/f noise and third harmonic distortion - A case study for
quality assessment of resistors," Microelectronics Reliability, vol. 40,
pp. 1847-1853, 1999.
R. W. Kuehl, "Reliability of thin-film resistors: Impact of third
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The British Standards Institution, "BS EN 60440:2012," London, U.K.:
BSI Standards Limited, 2012, pp. 9-10.