Reproduction of microparts based on standard X-ray LIGA processes for mass production

Abstract

This paper presents a rapid reproduction method of microparts based on the standard X-ray LIGA processes. The SU-8 master mold of microparts is fabricated by X-ray lithography which offers the high aspect ratio microstructure with vertical sidewall for high precision microparts. A 10:1 mixture of pre-polymer PDMS is cast onto the master mold and peeled off to create the replicated PDMS. It is pressed on the substrate coated with chromium seed layer, resulting in the temporary bonding between them. Nickel is then grown inside the replicated PDMS to create another metallic micropart by electroplating. After the replicated PDMS is removed from the sample, the over-electroplated microparts are covered with unexposed SU-8 photoresist and planarized to achieve the final thickness, followed by photoresist removal. The metallic microparts are finally released from the substrate by the mechanical force, resulting in the massive reproduced metallic microparts. The key geometric dimensional changes throughout the process were less than 1% which obviously confirmed the reliability of the reproduction using X-ray LIGA technology. The proposed method offers the rapid replication of micromolds and microparts in low-cost mass production without further X-ray lithography process.