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Ultrasonic treatment of aerosol jet printed traces

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08 nov 2024
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Figure 1

Schematic diagram of the aerosol jet printer with an ultrasonic atomiser equipped with (A) control unit, (B) microfluidic Elveflow controller, (C) ink reservoir, (D) ultrasonic transducer, (E) air compressor, and (F) sonotrode with PH fixed above CNC bed.
Schematic diagram of the aerosol jet printer with an ultrasonic atomiser equipped with (A) control unit, (B) microfluidic Elveflow controller, (C) ink reservoir, (D) ultrasonic transducer, (E) air compressor, and (F) sonotrode with PH fixed above CNC bed.

Figure 2

PH (a) and UH (b) fixed and attached to manipulator arm, (c) CNC heating bed. 1 – aerosol inlet, 2 – shielding gas inlet, 3 – exchangeable nozzle with an inner orifice diameter of 0.36 mm, 4 – sample (polyimide foil) with printed traces.
PH (a) and UH (b) fixed and attached to manipulator arm, (c) CNC heating bed. 1 – aerosol inlet, 2 – shielding gas inlet, 3 – exchangeable nozzle with an inner orifice diameter of 0.36 mm, 4 – sample (polyimide foil) with printed traces.

Figure 3

Schematic view of high-power ultrasonic field impact on ink particles.
Schematic view of high-power ultrasonic field impact on ink particles.

Figure 4

Cross section of the model of the designed ultrasonic system: transducer (1), sonotrode (2), and plate (3).
Cross section of the model of the designed ultrasonic system: transducer (1), sonotrode (2), and plate (3).

Figure 5

Distribution of vibration amplitude and stress along the waveguide [41].
Distribution of vibration amplitude and stress along the waveguide [41].

Figure 6

Results of modal analysis of the designed ultrasonic system for 20,000 Hz longitudinal mode. Idle state (a), different phases of tool displacement: +45° (b) and +90° (c).
Results of modal analysis of the designed ultrasonic system for 20,000 Hz longitudinal mode. Idle state (a), different phases of tool displacement: +45° (b) and +90° (c).

Figure 7

View of 3D model of the ultrasonic system with the working plate for ultrasonic wave concentration.
View of 3D model of the ultrasonic system with the working plate for ultrasonic wave concentration.

Figure 8

Frequency characteristics of the designed ultrasonic system intended to increase the uniformity of particle distribution of injected paths. Impedance characteristics of transducer (a), transducer coupled with sonotrode (b), and complete ultrasonic system (c).
Frequency characteristics of the designed ultrasonic system intended to increase the uniformity of particle distribution of injected paths. Impedance characteristics of transducer (a), transducer coupled with sonotrode (b), and complete ultrasonic system (c).

Figure 9

Top view of printed traces: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d).
Top view of printed traces: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d).

Figure 10

The boundary region of sample P + S (a) and P + U + S (b).
The boundary region of sample P + S (a) and P + U + S (b).

Figure 11

Top view of printed and sintered traces: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d). The dark region in the central part of the trace responds to porosity and high roughness.
Top view of printed and sintered traces: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d). The dark region in the central part of the trace responds to porosity and high roughness.

Figure 12

Sample P + H + U + S with a visible crack in the axis: DM (a) and AFM (b).
Sample P + H + U + S with a visible crack in the axis: DM (a) and AFM (b).

Figure 13

AFM scans of sample surface: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d). Black dots respond to SOP.
AFM scans of sample surface: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d). Black dots respond to SOP.

Figure 14

AFM micrographs of P + S (a) and P + U + S (b) samples. Red circles highlight black dots and respond to SOP.
AFM micrographs of P + S (a) and P + U + S (b) samples. Red circles highlight black dots and respond to SOP.

Figure 15

SEM micrographs presenting cross-section of printed traces: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d).
SEM micrographs presenting cross-section of printed traces: P + S (a), P + H + S (b), P + U + S (c), and P + H + U + S (d).

Figure 16

Results of resistance measurements and resistivity calculations.
Results of resistance measurements and resistivity calculations.

Formulas for estimating length of sonotrode depending on its shape_

Sonotrode shape First resonance length
Cylindrical L = C 2 f L\hspace{.25em}=\hspace{.25em}\frac{C}{2f} [41]
Stepped cylindrical L = k 1 c 4 f + k 2 c 4 f L\hspace{.25em}={k}_{1}\hspace{.25em}\frac{c}{4f}+{k}_{2}\frac{c}{4f} [42]
Exponential L = C 2 f 1 + ln D 1 D 2 π 2 L\hspace{.25em}=\frac{C}{2f}\sqrt{1+{\left(\frac{\text{ln}\left(\frac{{D}_{1}}{{D}_{2}}\right)}{\pi }\right)}^{2}}\hspace{.25em} [43]
Conical L = 2 c  atan ( 2 π f c α ) 2 π f L\hspace{.25em}=\hspace{.25em}\frac{2c\text{ atan}\left(\frac{2\pi f}{c\alpha }\right)}{2\pi f} [44]
where

k 1, k 2 represent coefficients depending on the cross-sectional area (for simplicity, they are taken equal to unity),

D 1, D 2 represent the diameter of the attachment surface and working surface,

α is the angle of inclination of the outline formers with respect to the axis.

Properties of the utilised ink provided by manufacturer [40]_

Dynamic viscosity (m·Pa·s) Surface tension (dynes/cm) Density (g/cm3) Silver content (%) Silver powder particle size range (nm)
7.5–10.5 28.5–32.5 1.1–1.3 45 3–8

Geometry and properties of printed traces_

Sample Width (µm) Height (nm) Roughness SOP (%)
Total Without spilled ink Average value Sa (nm) Sz (nm)
P + S 406 ± 8 311 ± 11 586 ± 31 123 ± 20 995 ± 33 17.2
P + H + S 383 ± 47 294 ± 29 556 ± 89 91 ± 13 888 ± 30 9.1
P + U + S 526 ± 56 416 ± 35 629 ± 106 148 ± 21 1158 ± 181 5.9
P + H + U + S 415 ± 29 302 ± 33 722 ± 103 92 ± 9 1276 ± 198 2.7