Process Development and Analysis of Self-Assembly Microchips with Surface Modification
Date Issued
2007
Date
2007
Author(s)
Chang, Chia-Shou
DOI
zh-TW
Abstract
Self-assembly is to transform a system from a disordered state to an ordered state, meaning that microstructures automatically assemble on the substrate. Conventional assembly technology has adopted “pick and place” which picks microchips from a wafer and placing them onto the substrate. But this technique encounters speed and cost constraints when chip size is reduced to the micrometer scale. Hence, an economic and effective self-assembly method is very important. We demonstrated a technique for temporally self-assembling silicon microchips onto a silicon substrate and performing further self-alignment at a high temperature to form permanently electrical connection by the eutectic solder bumps. We used surface modification to control the hydrophobic-hydrophilic surface properties of patterned microstructures and substrates to result in a spontaneous wetting. After the first step spontaneous self-assembly process, the second step self-alignment process is followed by means of solder-based surface tension.
On the other hand, we also designed a new releasing mechanism to realize the two-pads self-assembly technique. Meanwhile, we developed a simulation model to explain the phenomenon. The rectangle-shaped pad represents the better assembly performance than square-shaped pad, and the displacement model occurs earlier than rotation model for the single-pad self-assembly. In addition, the two-square-shaped pads represent the better assembly performance than one-rectangle-one-square-shaped pads and the displacement model coincides with rotation model at the same time for the two-pads self-assembly. Also, use of different bonding sizes and shapes help enhancing the self-assembly performance.
At last, the surface force model is provable because experimental result is close to this model. We also combined Young’s equation with Owens-Wendt method to calculate the contact angle between the microchip and substrate in water. Then, we can distinguish the bonding and obtain the optimization. This technique is compatible with the surface mount technique (SMT) and Flip Chip technique. The presented technique could be applied to assembly of light emitting diodes, RFID tags, MEMS components, micro-integrated circuit devices or other types of microstructures.
Subjects
自組裝
兩階段式
共晶銲錫
表面改質
親疏水性
兩接點
接觸角
self-assembly
two-step
eutectic solder
surface modification
hydrophobic-hydrophilic
two-pads
contact angle
Type
thesis
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