Self-alignment in the stacking of microchips with mist-induced water droplets

Abstract

This paper reports a novel and versatile water droplet self-alignment technique where the water is delivered in mist form onto the assembly site. The droplet forming process has been carefully investigated using machine vision, where each individual droplet on the microchip surface can be identified and the volume per surface area can be calibrated at a specific time. The result reveals that the volume of water droplets on the assembly surface grows linearly as a function of time. Self-alignment based on the mist-induced droplets has been studied, where a robotic microgripper is used to deliver the microchips on the assembly site. The paper also investigates the maximum tolerance of the initial placement error in stacking SU-8 chips 200 × 200 × 70 µm in size, and the possibility of stacking two SU-8 chips of different dimensions using the proposed self-alignment technique. Moreover, self-alignment of chips on hydrophilic/hydrophobic patterns covered by mist-induced water droplets has been studied. The experimental results indicate that this novel self-alignment technique is very promising. Furthermore, a statistical model has been used to validate the experimental results.

Capillary self-alignment assisted hybrid robotic handling for ultra-thin die stacking

“…The method is built upon the recent efforts on combining robotic microhandling and self-assembly into a hybrid microassembly strategy [3][4][5][6][7], where fast-speed robotic pick-and-place is used for coarse positioning, and high accuracy is reached by capillary self-alignment of a droplet, driven by the capillary force between the die and the receptor site. The capillary force also aids in overcoming the adhesion forces between the die and the gripper, which is a common problem in micromanipulation.…”

Hybrid microassembly for massively parallel assembly of microchips with water mist

“…Self-assembly technique has been demonstrated for assembly of micro sized components driven by capillary forces [2][3][4][5][6][7], magnetic forces [8] and electrostatic forces [9]. Another promising technique to achieve high alignment accuracy and high speed is hybrid assembly technique, which is proposed by the authors previously [10][11][12][13]. The technique combines the robotic pick-and-place technique and self-assembly technique.…”

“…In our earlier work [10][11][12][13], we have reported that the hybrid assembly technique can simultaneously achieve the desired performance in both speed and accuracy. However, it has not been proven that the hybrid assembly technique can be used for massively parallel assembly of microchips.…”

Surface-tension driven self-assembly of microchips on hydrophobic receptor sites with water using forced wetting

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] One key aspect of the technology is a well-designed receptor site where the self-alignment process of the selfassembly will take place. The general rule is that the receptor site should be lyophilic (against the lyophobic background) to the self-alignment medium-the liquid medium between the receptor site and the micropart to be assembled, e.g., hydrophilic receptor site if water is used as the self-alignment medium in air [6][7][8][9][10][11] or oleophilic receptor site if adhesive is used as self-alignment medium in water. [1][2][3][4][5] In air, solid-edges can also be used as the boundary for the self-alignment process.…”