Lead-Free Nanomaterials for Electronics

In electronics manufacturing, lower solder reflow temperature is desirable to prevent manufacturing problems such as popcorning, delamination and warpage. On the other hand, during operation, especially in high temperature application such as aerospace and military electronics, the solder joint must withstand high temperatures and maintain high reliability. This poses a converse set of goals, namely, low manufacturing melting point and high operation melting point, which cannot be achieved with bulk solder joint materials. Alloy nanoparticles offer a unique combination of low and high melting temperature. In collaboration with Rice University [Tabatabaei et. al, 2012], we have shown that AuSn nanoparticles exhibit significantly reduced melting temperature for manufacturing. As the particles melt and form solder joint, they can recover the high bulk AuSn melting point making them suitable for high temperature and high reliability electronic applications.

Plastic Encapsulated Microelectronics

Hygroscopic Swelling: For many years, moisture induced swelling in plastic encapsulant in microelectronic package was ignored. Recently, new techniques of swelling measurements revealed that swelling coefficient is comparable to the coefficient of thermal expansion (CTE), and therefore, swelling mismatches between adjacent components in plastic encapsulated microelectronics must be considered in the design and reliability analysis. Dr. Ardebili's previous reaserch [Ardebili et. al, 2003] involved a pioneering work in new measurement technique for swelling coefficients of common plastic encapsulants (epoxy molding compounds) using a modified thermo-mechanical analyzer (TMA).

Microelectronics

Moisture Diffusion Modeling: Moisture in plastic encapsulated electronics (PEMs) can lead to variety of reliability problems including popcorning (cracking during solder reflow), delamination and corrosion. Modeling moisture diffusion allows us to better understand and predict the diffusion process, and more effectively mitigate it. Moisture diffusion can be either Fickian or non-Fickian. Dr. Ardebili's research [Ardebili et. al, 2002] involving experimental observations from moisture sensor placed inside the PEM shows that in many cases, Fickian model is sufficient to predict moisture content at the interface of encapsulant and passivated chip.

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