Application Cases

Experiment Name: Experimental Study on Particle Electrospray Deposition and Control

Test Purpose: This study focuses on the characteristics of conductive particle electrospray deposition and control. By comparing particle deposition under different parameters, the target operating range for this process is investigated, and other phenomena encountered during the experiments are analyzed and explained.

Test Equipment: High-voltage amplifier, Driver, Industrial camera, Injection control pump, Computer, etc.

Experimental Process:

Figure 1: Prototype device for particle deposition and control

A prototype device for spraying and depositing conductive particles was designed and manufactured (Figure 1a). Based on automation and modularization concepts, this device updates several functional components of the original platform, including the high-voltage power components and the injection control pump. It also incorporates a motorized bottom platform to assist in improving particle deposition effectiveness and to be compatible with expected chip wafer sizes.

The high-voltage generation module uses a high-voltage amplifier. This component's function is to amplify the input weak voltage signal to the required strength. By controlling the digital-to-analog conversion element on the PC side, the output voltage can be controlled in real time, enabling two key functions:

1. Synchronized application of voltage with the motion platform and flow control timing to initiate electrospray deposition, allowing selection of the approximate deposition area.

2. Setting the voltage function during electrospray. As previously mentioned, in steady cone-jet mode, the spray jet and spray field continuously deflect as the voltage increases. To achieve symmetric and uniform deposition patterns, the operating voltage should be chosen as close as possible to the lower threshold voltage for triggering the steady cone-jet mode. However, due to hysteresis effects, if the voltage is too close to this lower threshold, there is a chance the spray might remain in the pulsating cone-jet mode. In this case, the PC control can set a slightly higher initial voltage followed by a slight decrease, ensuring the formation of a steady cone-jet while effectively lowering the operating voltage.

   
   

Figure 2: Overall morphology of particle deposition patterns under different electrode distances

First, the size of the overall particle deposition patterns was compared using different electrode distances (the distance between the needle and the substrate). When the distance is too small, the spray cannot fully develop. When it is too large, the spray field loses optimal symmetry due to increased susceptibility to external airflow. Clearly, neither condition is conducive to obtaining uniform deposition patterns. Therefore, the needle height range selected for this experiment was limited to 10–30 mm. Figure 2 shows the overall views of deposition patterns obtained at electrode distances of 10 mm, 20 mm, and 30 mm. The diameter of the patterns can be measured using the calibration scale (1 mm per division) on the left side of the images. Overall, the obtained deposition patterns have clear boundaries, complete morphology, and are relatively smooth, demonstrating that the electrospray process can effectively and uniformly disperse a large number of conductive particles over a large-area substrate. Figure 3 statistics the distribution of deposition pattern diameters from 10 experiments at different electrode distances. Observing the change in diameter with electrode distance, except for a slight deviation at the closest distance, it generally shows a linear growth relationship.

Figure 3: Distribution of deposition pattern diameters under different electrode distances

Experimental Results:

Through the comparison and observation of the overall morphology of the deposition patterns, a working electrode distance of 20 mm was preliminarily selected, considering both coverage area and deposition uniformity. Regarding experimental parameters, this section primarily used a conductive particle suspension with a mass fraction of 0.2 wt.% (approximately 0.02g of particles per ml of solution), with pure isopropanol as the solvent. The needle specification used was 24G, the supply flow rate was 0.5 ml/H, and the spraying duration was one minute. Apart from the flow rate and needle type, the other parameters mentioned basically do not affect the shape of the deposition pattern. Changes in concentration only affect the darkness of the pattern, and similarly, extending the spraying time does not significantly change the diameter of the pattern.

Voltage Amplifier Recommendation: ATA-7100

Figure: ATA-7100 High-Voltage Amplifier Specifications

This document has been compiled and released by Aigtek. For more application cases and detailed product information, please follow us continuously. Xi'an Aigtek has become an instrument and equipment supplier with a wide range of product lines and considerable scale in the industry. Demo units are available for free trial.