Time of resolved X-ray analysis in Self-propagating exothermic reaction of Al/Ni multilayer films

Al/Ni multilayer film shows a self-propagating exothermic reaction when a minute external shock is applied. Using the reactive film as a heat source for soldering enables us to complete the bonding process instantaneously within a second because of its fast reaction propagation. However, cracks are introduced in the reacted NiAl layer after bonding, which becomes a big problem in the viewpoint of thermal and mechanical reliability. In this study, a laser-induced multiple points ignition technique is developed, and reaction propagation characteristics and crack introducing phenomenon are investigated toward crack propagation control.

Section: Methodsmentioning

confidence: 99%

Laser-induced multiple points ignition test in Al/Ni exothermic reactive film for crack propagation control

Morishita

Miyake

Namazu

2021

“…[19][20][21][22][23] Therefore, for Ni and Al to react at a one-to-one atomic ratio, the Al/Ni multilayer material is usually fabricated by alternately depositing Al and Ni using a physical vapor deposition (PVD) method at every few nanometers of thickness for MEMS and Si devices. 8,14,24) However, the size of the fabricated substrate is limited by the size of the vacuum chamber used in the PVD method. This can cause a decline in both productivity and convenience for other engineering applications.…”

Section: Introductionmentioning

confidence: 99%

Microscale thermal characteristics of cold-rolled aluminum alloy using a thermoreflectance method

Yamashita

Miyake

2022

In this study, the microscale thermal propagation behavior of cold-rolled aluminum alloy sheets was characterized using a thermoreflectance (TR) method from the micro and macro perspectives, and the relationship between the crystallite sizes of cold-rolled aluminum sheets with different rolling reduction rates and their thermal propagation characteristics was described. The crystallite sizes were analyzed by X-ray diffraction using Scherrer’s equation. The microscale thermal propagation characteristics of these specimens were measured using a TR method with a high spatial resolution of several micrometers through a focused laser beam and by controlling the thermal diffusion length. The macroscale thermal propagation characteristics of these specimens were then measured using two methods: the spot periodic heating method and the electrical resistance measurement method with the Wiedemann–Franz law. Experimental results showed that the microscale thermal propagation correlated with a change in the crystallite size. However, the macroscale thermal conductivity decreased with an increase in the rolling reduction rate regardless of the crystallite size. It is expected that the thermal propagation characteristics at the microscale can be controlled by a change in the crystallite size.

“…Several papers on the fabrication of Al/Ni multilayer films by the PVD method have been published in the literature. 22,25) However, the quality of the surface of silicon substrates may detrimentally be affected by the PVD process. Moreover, the size of the fabricated substrate is limited by the size of the vacuum chamber used in the PVD method.…”

Section: Introductionmentioning

confidence: 99%

Crystallite size analysis of Al/Ni multilayer powder by synchrotron radiation X-ray diffraction

Yamashita¹,

Yamamoto²,

Miyake³

2021

The self-propagated exothermic reaction characteristics of Al/Ni multilayer powders can be employed as heat sources and controlled by cold-rolling conditions. This feature depends on the heat propagation inside of crystal grains. Therefore, the crystallographic factor that relates cold-rolling conditions to exothermic characteristics should be identified. To determine the change trend in crystallite size with the increase in the number of rolling passes, the crystallite sizes in the Al/Ni multilayer powder were calculated using Scherrer’s equation, and precise X-ray profiles were obtained using the synchrotron radiation X-ray diffraction method. The results indicate that the crystallite sizes were refined by increasing the number of rolling passes up to 30; from 30 to 40 passes, however, the crystallite sizes increased. It is assumed that, in addition to the Al/Ni multilayer powder being thin and multilayered, the increase in crystallite size at 40 passes allows for the smooth propagation of heat, consequently improving the exothermic characteristics. Therefore, crystallite size is the dominant parameter in the relationship between rolling conditions and exothermic characteristics.