In-Situ Investigation on Melting Characteristics of 1d Sncu Alloy Nanosolder

Abstract

Nanosoldering can bond various nanomaterials together or connect them with electrodes to form electrical contacts, thus assembling these nanomaterials into functional nanodevices; it is believed to be a promising interconnection technique due to its flexibility, controllability and crucial advantage of avoiding detrimental effects on the nano-objects. In this technique, molten solder as a filler material is introduced between the objects to be joined to form a reliable bond, in which the realization of the nanosolder reflow melting is a crucial prerequisite for successful nanosoldering. This work focuses on studying the melting characteristics of onedimensional 97Sn3Cu nanosolder, which has many advantages including low-cost, prominent properties and high mechanical reliability, and aims to promote its applications in nanosoldering. The reflow melting of an individual nanosolder has been dynamically observed by in-situ heating holder in transmission electron microscopy, where the obtained reflow temperature (530 °C) is much higher than its melting temperature (220.4 °C) because of the external oxide layer confinement. Furthermore, the size-dependent melting temperature of nanosolders with various diameters (20-300 nm) has been investigated by differential scanning calorimetry and theoretical calculation, revealing that the melting temperature decreases as the diameter goes down, especially for the sizes below 80 nm, at which the value decreases significantly. The experimental results are in good agreement with the theoretical predictions. These results pointed out here can be readily extended to other nanosolders.

Keywords: Keywors: SnCu alloy, nanosolder, in-situ reflow behavior, size-dependent melting temperature