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Materials Science in Additive Manufacturing Intense pulsed light sintering of conductive film

technology that requires high processing temperature In general, a sintering treatment is required to process
which poses restrictions on the material options . In the printed ink layers in order to make the active materials
[3]
contrast, printed electronics technology uses functional functional . This is because the active materials are
[23]
inks to create circuits and electronic components, normally covered with a layer of organic stabilizer,
thereby lowering the process temperature and creating which impedes their functionality. Sintering treatment
more opportunities for new electronic architectures with removes the organic stabilizer layer and binds the active
various substrates, particularly for low thermal stability materials together. For the case of metal nanoparticle, the
substrates [4-7] . It has allowed for new opportunities for the nanoparticles receive energy during the sintering process
creation of flexible electronic components that can be used and fuse together and grow larger to form a conductive
in applications such as water technology for system health network of nanoparticles. Besides, sintering treatment
monitoring purpose . also enhances the adhesion of the printed materials to
[8]
the substrates. Till now, there are many different sintering
In the early years, printed electronics is normally done techniques that have been developed such as thermal
using traditional additive-based printing techniques that sintering , electrical sintering , induction sintering ,
[24]
[26]
[25]
require tool, mask, or stencil for the patterning of inks . and photonic sintering . Each sintering technique offers
[9]
[27]
These traditional printing techniques include screen its unique advantages and possesses certain limitations.
printing, gravure printing, flexographic printing, and For examples, thermal sintering treatment can achieve
offset printing. These techniques are compatible with homogeneous sintering but may not be suitable for all
the roll-to-roll manufacturing process and allow the use substrates as the substrate will be exposed to the same
of flexible substrates, which makes them highly suitable sintering condition. In contrast, induction sintering and
for mass production of flexible electronics. However, electrical sintering offer selective sintering of nanoparticle
the recent shift in the industry’s needs for custom-made layers, but only work with metallic inks and require pre-
electronics has spurred the search for cheaper alternatives thermal treatment to make them conductive.
for electronic fabrication because of the high initial
cost for the tools and stencils renders the traditional Intense pulsed light (IPL) sintering is a type of photonic
printing techniques uneconomic for such purpose. In sintering method that uses pulses of high intensity light to
[28]
contrast, three-dimensional (3D) printing, also known sinter the nanoparticle inks . The process uses a xenon
as additive manufacturing, is found to be a better option lamp that emits a broad spectrum of light with wavelength
for the fabrication of highly customizable advanced ranges from visible light to UV light as the energy
electronics . At present, 3D printing techniques such as source [29-31] . Unlike other sintering techniques, IPL sintering
[10]
inkjet printing , aerosol jet printing [12-15] , and direct ink can be done in a very short time and does not induce
[11]
writing have been increasingly used by the industry significant damage to the substrates. The performance of
[16]
to manufacture advanced electronics that require fine the IPL sintering technique depends on various factors
resolution and sophisticated geometry. Among which, such as the light intensity, the type of substrates, the ink
aerosol jet printing technique has gained much attraction composition, the light absorption of the nanoparticle, and
over the years due to its capability to process a wide range the thickness of the printed film. Despite the advantages of
of materials and the high printing resolution . Besides, it IPL technique, it is widely known that the process can cause
[17]
can also be used to integrate electronics on 3D structures, defects such as cracks and delamination of the printed
making it suitable for realizing novel electronic designs . film due to the rapid vaporization of the gases originating
[18]
from the organic compounds . These defects can cause
[32]
Regardless of the printing techniques, the functional undesirable and inconsistent performance of the electrical
inks remain the key ingredient to achieving the low circuit or electronics components. Severe delamination
processing temperature for printed electronics [19,20] . To date, can also restrict the use of the IPL-sintered conductive film
various types of functional inks such as silver nanoparticle for multilayer electronic designs which requires additional
inks, gold nanoparticles inks, and silver nanowire inks have insulating or functional layers atop of the printed
been developed to cater for different applications [4,21,22] . conductive film such as the case of electrochemical sensing
Functional inks generally contain several components, electrodes. Although this issue can be solved by using back
namely, the active material, the solvent, the binder, the irradiation rather than top irradiation, it is only limited
surfactant, and other additives . The active materials and to transparent substrate and does not address the issue
[31]
[20]
binder made up the main materials of the printed layers for some samples that requires top irradiation. Although
that determine the type and property of the layers, whereas preheating the samples is found to be helpful in reducing
the other materials such as the solvent, surfactant, and delamination in certain cases, it may not solve the issue
other additives will be removed in the sintering process. entirely for thicker samples .
[33]

Volume 1 Issue 2 (2022) 2 http://doi.org/10.18063/msam.v1i2.10