Abstract
Additively printed circuits provide advantages in reduced waste, rapid prototyping, and versatile flexible substrate choices relative to conventional circuit printing. Copper (Cu) based inks along with intense pulsed light (IPL) sintering can be used in additive circuit printing. However, IPL sintered Cu typically suffer from poor solderability due to high roughness and porosity. To address this, hybrid Cu ink which consists of Cu precursor/nanoparticle was formulated to seed Cu species and fill voids in the sintered structure. Nickel (Ni) electroplating was utilized to further improve surface solderability. Simulations were performed at various electroplating conditions and Cu cathode surface roughness using the multi-physics finite element method. By utilizing a mask during IPL sintering, conductivity was induced in exposed regions; this was utilized to achieve selective Ni-electroplating. Surface morphology and cross section analysis of the electrodes were observed through scanning electron microscopy and a 3D optical profilometer. Energy dispersive X-ray spectroscopy analysis was conducted to investigate changes in surface compositions. ASTM D3359 adhesion testing was performed to examine the adhesion between the electrode and substrate. Solder-electrode shear tests were investigated with a tensile tester to observe the shear strength between solder and electrodes. By utilizing Cu precursors and novel multifaceted approach of IPL sintering, a robust and solderable Ni electroplated conductive Cu printed electrode was achieved.
Highlights
Printed circuits provide advantages in reduced waste, rapid prototyping, and versatile flexible substrate choices relative to conventional circuit printing
It was found that Cu precursor in an amount of 30 wt.% relative to Cu NPs has the highest electrical conductivity and packing density when sintered with IPL25
We investigated the feasibility of nickel plating on intense pulsed light (IPL) sintered hybrid copper electrodes
Summary
Printed circuits provide advantages in reduced waste, rapid prototyping, and versatile flexible substrate choices relative to conventional circuit printing. Utilizing common polymers as substrates such as polyimide (PI), polyethylene terephthalate (PET), and polyethylene terephthalate glycol (PETG) provide a pathway to a wide variety of robust and cheap electronic devices These polymers are susceptible to damage from high temperature processes due to their low glass-transition temperatures ranging as low as 67 °C. Sintering via IPL bypasses high temperature processing by using the surface plasmonic effect; during IPL irradiation, electrons on the surface of nanomaterials resonate at a frequency that collapses its surface energy and allows significant necking/densification within the loose particles[12,13,14] This effect significantly reduces sintering temperature and time requirements, which would otherwise damage the flexible substrate and immensely increase the manufacturing cost of flexible electronics. IPL provides electrically conductive and oxide species reduction that reduce Cu particles for a high-performance ink receptive of existing printing technologies[16,17,18]. It has been difficult to realize the mass production of ink-printed electronic circuit components
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