Effect of Laser Intensity on the Characteristic of Inkjet-Printed Silver Nanoparticles During Continuous Laser Sintering

Abstract

The variation in electric conductivity was examined for laser irradiation with various beam intensities. A 532-nm continuous wave laser was irradiated onto inkjet-printed silver lines on a glass substrate and the electrical resistance was measured in situ during the irradiation. The results demonstrate that electrical conductivity varies nonlinearly with laser intensity, and has a minimum specific resistance of 3.1 x 10(-8) Ωm at 4 kW/cm2 irradiation. These results are interesting because the specific resistance achieved by the present laser irradiation was approximately 1.9 times lower than the best value obtainable by oven heating, even though it was still higher by 1.9 times than that of bulk silver. It is also demonstrated that the irradiation time required to complete the sintering process decreases with laser intensity. The numerical simulation of laser heating shows that the heating temperature could be as high as 250 degrees C for laser sintering, while it is limited to 250 degrees C for oven sintering. The characteristics of sintering with laser intensity based on the results of field emission scanning electron microscope images are discussed.

Stepwise Current Increment Sintering of Silver Nanoparticle Structures

“…The minimum resistivity of 6.28 μΩcm was achieved in 0.15 s by the SCIS technique with 0.57 A final-step and this value was close to the Ag NP line resistivity sintered for 600 s at 250 °C via furnace sintering. The induced high temperatures with the application of the final-step C was selected because the best resistivity results were reported at this temperature in previous studies [27,28] without any thermal damage. The resistivity of the Ag NPs sintered in a furnace for longer durations was decreased.…”

“…For example, typically higher temperatures provide much better sintering results [17,25,26]. However, this restricts the use of temperature-sensitive substrates [16,27]. Therefore, the measurement of the process temperature during sintering is essential.…”

“…The furnace sintering times were 1, 10, and 50 min at furnace temperatures of 150, 200, and 250 • C, respectively. The maximum furnace temperature of 250 • C was selected because the best resistivity results were reported at this temperature in previous studies[27,28] without any thermal damage. The resistivity of the Ag NPs sintered in a furnace for longer durations was decreased.…”

Effect of Thickness on Surface Morphology of Silver Nanoparticle Layer During Furnace Sintering

“…This nonlinear variation of the specific resistance of Ag nanoparticle layer agrees well with previous studies. [13][14][15][16] To examine the reason of this nonlinear variation of electrical conductivity, XRD measurements were first carried out and the possible oxidation of Ag nanoparticles were checked. As shown in Fig.…”

“…Further heating results in the loss of electrical conductivity due to the formation of too large Ag agglomeration and broken connectivity. [13][14][15][16] The limitation of sintering temperature could be critical to some application where high temperature processes should be followed up. For example, printing of oxide semiconductor thin film transistors (TFTs) might need high-temperature treatments at 300-600°C for metal oxides, and the already printed bottom electrodes will also suffer the high temperature.…”