Erwin Yacoub-George

Selective one-step plasma patterning process for fluidic self-assembly of silicon chips

Applying a tetrafluoromethane (CF4) low pressure plasma process to the surface of a polymeric foil with a structured thin film copper layer on top results in an opposed wettability behavior of metal areas and polymer areas. Difference in the local water contact angle between the hydrophobic polymer and the hydrophilic copper after a maskless CF4 plasma treatment is 95deg-105deg. By storing the plasma treated foils under nitrogen their programmed wetting behavior can be preserved for at least ten day. The special wetting properties of surface energy patterned foils favor them as substrate materials in fluidic self assembly processes. Self alignment of small and thin silicon chips on copper bonding sites on polyimide foils was observed. Specific design patterns are proposed that enable both bonding of dies at dedicated target positions and electrical interconnects at front side or rear side of electronic components with two connection pads. Using a droplet of water as assembly medium and an anisotropic conductive adhesive (ACA) coating lead to successfully assembled test chips on patterned polyimide foils that were pre-treated in the selective one-step CF4 plasma.

Self-assembly and self-interconnection of thin RFID devices on plasma-programmed foil substrates

The paper reports on a self-assembly process that enables both self-alignment of microelectronic devices and self-interconnection of devices with the surrounding electrical wiring. The complete process was successfully demonstrated using state-of-the-art RFID devices (radio frequency identification device) which were self-connected to four metal pads on polymer foil substrates. The new self-assembly concept comprises the following steps: mask-less plasma patterning process to define target areas for die assembly on polymer tapes, application and self-alignment of a liquid assembly medium at the target area, dropping of the chip device onto the assembly liquid, self-orientation of the chip with respect to the contact pads and finally heat induced bonding and interconnection of the device.

Multifunctional system integration in flexible substrates

In this paper we present a technology developed for reliable electrical interconnection on film substrates and between vertically stacked film layers. Applying through-hole via technologies for 3D foil stacks enables multi-functionality and RF performance combined with open form-factor and very cost-efficient manufacturing of conformable electronic modules. The manufacture of fine line metal patterns (line /space geometries below 20μm) on film substrates is performed by cost-effective roll-to-roll technology. Furthermore procedures and technologies for handling and lamination of film based sub-modules have been developed. Also the manufacture and handling of ultra-thin and flexible integrated circuits has been combined with placement of SMD type passive and with integrated printed passive components in the same technology.