Composite Metal Matrix Castings and Solder Compositions and Methods for Microelectronics and Metal Matrix Castings
The rapid advance in the miniaturization of electronic components require novel soldering solutions with sub-micron reinforcements. Sub-micron reinforcements can minimize grain boundary sliding. Another challenge is increased current density in Micro-Electro-Mechanical Systems (MEMS). Ion migration across electrodes causes voids and ultimately solder joint failure. This invention provides the necessary submicron reinforcements to mitigate these emerging challenges and thus to extend its service life.
Description of Technology
This technology is an improved solder composition. Lead-free solder is strengthened by introducing nanoscale reinforcements consisting of organofunctionalized silicon-oxygen cage-structured compounds. These reinforcements comprise POSS (polyhedral oligomeric silsesquinoxanes and derivatives) and POS (polyhedral oligomeric silicates). POSS has organic moieties (aliphatic and aromatic hydrocarbons) bonded to the silicon atoms of a silicon-oxygen, 3-dimensional cage structure. The solder composition has about 3% weight of POSS, which is about 20% volume.
- Longer service life: The reinforced solder has superior mechanical properties under conditions of thermo-mechanical fatigue that result in a much desired longer service life than existing solders. For example, the reinforced solder outperforms unreinforced solder under thermocyclic conditions: after 1000 thermomechanical fatigue cycles, there was less than 20% decrease in strength, vs. a 40-50% loss with unreinforced solder.
- Better properties: Reinforcing phase segregates to grain boundaries where it reduces grain boundary sliding and thus creep, stabilizes solder microstructure: no grain growth is observed, and has little effect on electrical conductivity.
- Inexpensive process: Reinforcing phase (nanosize POSS or POS) can be mechanically mixed into commercial solder pastes.
- Uniform distribution: After mixing, reinforcing phase is uniformly distributed with no noticeable micron-sized agglomerations.
The technology has utility in electronics especially microelectronics and could potentially be extended to metal matrix castings.
Prototype exists; proof of concept demonstrated.
US 2005/0034791 A1 (filed Aug 3, 2004)
Karatholuvu Subramanian, Andre Lee
For Information, Contact:
Michigan State University