Further experiments and modeling for microscale compression molding of metals at elevated temperatures
- PDF / 387,219 Bytes
- 10 Pages / 585 x 783 pts Page_size
- 62 Downloads / 203 Views
E. Lara-Curzio High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (Received 21 December 2006; accepted 2 March 2007)
Replication of metallic high-aspect-ratio microscale structures (HARMS) by compression molding has been demonstrated recently. Molding replication of metallic HARMS can potentially lead to low-cost fabrication of a wide variety of metal-based microdevices. Understanding the mechanics of metal micromolding is critical for assessing the capabilities and limitations of this replication technique. This paper presents results of instrumented micromolding of Al. Measured molding response was rationalized with companion high-temperature tensile testing of Al using a simple mechanics model of the micromolding process. The present results suggest that resisting pressure on the mold insert during micromolding is governed primarily by the yield stress of the molded metal at the molding temperature and a frictional traction on the sides of the insert. The influence of strain rate is also considered.
I. INTRODUCTION
Metal-based microscale devices can perform better than their Si-based counterparts; one example is microheat exchangers.1 In other instances, metal-based microdevices possess functions not achievable using Si-based materials, for example, microelectromagnetic relays.2 Prototypes of metallic microheat exchangers and microelectromagnetic relays have been reported in the literature.3,4 Metal-based microdevices may also function better than Si-based microelectromechanical systems when subjected to high stresses, high temperatures, and other harsh conditions. Realization of most metal-based microdevices requires the fabrication of high-aspect-ratio microscale structures (HARMS). Metal-based HARMS can be fabricated by combining x-ray/ultraviolet (UV) lithography and electrodeposition. Such a manufacturing protocol is expensive and slow. In comparison, replication of secondary HARMS from primary microscale mold inserts by compression molding is fast and simple.5,6 We are therefore investigating its potential as a low-cost, high-throughput, production technique for metal-based microdevices. Prior to 2003, replication by compression molding had been achieved only in polymer-based materials.7 Since
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0252 J. Mater. Res., Vol. 22, No. 7, Jul 2007
http://journals.cambridge.org
Downloaded: 23 Mar 2015
2003, we have demonstrated successful molding replication in Pb,8 Zn,9 Al,10 and Cu.11 We have shown that one critical element for successful micromolding of reactive metals, such as Al, is to engineer the near-surface chemical and mechanical properties of the mold insert, and that conformal deposition of a suitably chosen thin ceramic coating over the microscale mold insert is an effective means for accomplishing such surface engineering.9,10,12,13 To mold metals with higher melting temperatures (Tm), the bulk of the mold insert needs to be constructed out of materials with
Data Loading...
