Wettability of hydraulically profiled low-carbon steel substrates

Purpose The purpose of this research was to develop a new process to bond silicon (Si) chips to low carbon steel substrates using pure tin (Sn) without any flux. Design/methodology/approach Iron (Fe) substrates were first electroplated with a Sn layer, followed by a thin silver (Ag) layer that inhibits Sn oxidation thereafter. It is this Ag capping layer that makes the fluxless feature possible. Fluxless processes are more environmentally friendly and more likely to produce joints without voids. The Si chips were deposited with Cr/Au dual layer structure. The bonding process was performed at 240°C in vacuum. The Sn joint thickness was controlled by spacers during the bonding. Scanning electron microscopy images on cross sections exhibited quality joints without visible voids. Energy dispersive X-ray spectroscopy analysis was used to detect joint compositions. Findings It was revealed that the Sn layer was bonded to a Si chip at the Cr–Sn interface and to the Fe substrate by forming an FeSn2 intermetallic compound (IMC). The IMC is only 1.1 to 1.5 µm in thickness. Thin IMC is highly preferred because IMC deforms a little in accommodating the coefficient of thermal expansion (CTE) mismatch between Si and Fe. Shear test results showed that the fracture forces of the samples passed the military criteria by a wide margin. Originality/value This new fluxless bonding process on Fe should make Fe or low carbon steel a more likely choice of materials in optical modules and electronic packages.

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Microstructural and Nanomechanical Properties of Aluminium Nitride (AlN) Thin Films Deposited by RF Magnetron Sputtering

Advanced Science Letters ◽

10.1166/asl.2018.12209 ◽

2018 ◽

Vol 24 (8) ◽

pp. 5855-5858

Author(s):

G Balakrishan ◽

A. Karthik Kumar ◽

M Kannan ◽

K Manikandan ◽

V Karthikeyan ◽

...

Keyword(s):

Thin Films ◽

Carbon Steel ◽

Magnetron Sputtering ◽

Substrate Temperature ◽

Room Temperature ◽

Salt Spray ◽

Low Carbon Steel ◽

Rf Magnetron Sputtering ◽

Low Carbon ◽

Steel Substrates

Aluminium nitride (AlN) thin films were deposited on AISI-1018 low carbon steel substrates at different substrate temperature (Room temperature −600 °C) using RF magnetron sputtering technique. The microstructural, mechanical and corrosion properties were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), nanoindentation and salt spray test respectively. The microstructural and properties were investigated as a function of substrate temperature. The XRD analysis of the AlN thin films prepared at RT and 200 °C indicated the poor crystallinity of the films, while the films prepared in the temperature 400–600 °C range indicated the increased crystallinity with hexagonal (0002) and cubic (002) structure. The AFM analysis showed the average roughness of 7 nm, 5.5 nm and 16 nm for room temperature, 200 °C and 500 °C temperature respectively. The hardness of the AlN thin films were found to be 11.99 GPa, 13.05 GPa, 12.29 GPa, 23.0 GPa and 11.12 GPa at room temperature, 200 °C, 400 °C, 500 °C and 600 °C, respectively. The salt spray analysis indicated no corrosion on low carbon steel substrates for 12 hours.

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