Selective electroplating and bonding for the integration of microstructures

Techniques of selective electroplating and bonding have been developed for the integration of microstructures, including flip-chip LIGA assembly, parallel electrical interconnection and batch transfer of LIGA microstructures. These processes are conducted in nickel electrolyte at a temperature of 50°C for less than 90 minutes. A pixel-wise, 3D electroplating process and a micro intrusion process for making metallic and plastic microstructures are also conducted as the foundations of integrated microstructures.; The LIGA assembly process uses nickel gears of 1500μm in diameter and 250μm in height fabricated by the standard LIGA process. They are bonded to a glass substrate that has 500/2000Å of Cr/Au layer on top by using the selective electroplating and bonding process. A 100μm wide bonding stripe is formed around the perimeter of the gear and it is concluded that the penetration width of this bonding stripe depends on the diffusion distance of the electrolyte between the two bonding surface.; In the second example, a parallel electrical interconnection process is accomplished by means of flip-chip, selective electroplating and bonding. The electrical interconnection lines are built on a glass substrate made of 500/2000Å of Cr/Au with 3150μm in length and 10μm in width. Two silicon device chips, each has 102 bonding pads, are to be electrically interconnected and 98 interconnects are established in parallel during the bonding process. The average resistance of the electroplating bond is 12Ω and the reliability test shows that 100% of interconnects survive after 2 cycles of the quenching process from room temperature to −195°C.; The last example of selective electroplating and bonding process is a flip-chip, batch transfer process for LIGA microstructures. Single layer LIGA microstructures with thickness of 200μm are fabricated on a dummy substrate and batch transferred to an IC substrate. The originally fixed single-layer microstructures on the LIGA substrate become free standing and moveable devices. Experimentally, an electrothermally driven LIGA microgripper has been demonstrated to operate after the batch transfer process and 92μm of movement is measured by the tips of microgripper when a maximum input current of 1.6 ampere is applied.