Strength evaluation of lead-free-solder joint fabricated by reactive film local heating

To realize the application of reactive joint process to electronic packaging, we analyze thermal resistance for solder joints fabricated by using Al/Ni self-propagating exothermic reaction. Laser flash method with response function analysis is used for thermal resistance measurement. The specimens with 4-8-µm-thick Sn-3.5Ag solder joint have thermal resistances ranging from 5.0 ' 10 %6 to 8.1 ' 10 %6 m 2 K/W. In the specimen with 12-µm-thick SnAg solder joint, periodical heating analysis suggests that high and low thermal resistance areas happen to coexist due to incomplete bonding. Micro thermo-reflectance (m-TR) analysis suggests that thermal effusivity of reacted NiAl layer is lower than expected. Thermal resistance of the joints will be influenced by voids, cracks, and grain boundaries in reacted NiAl layer.

Section: Introductionmentioning

confidence: 99%

Thermal property measurement of solder joints fabricated by self-propagating exothermic reaction in Al/Ni multilayer film

Miyake¹,

Kanetsuki²,

Morino³

et al. 2015

“…As one of these sources, Al/Ni multilayer material has received attention because of its outstanding characteristics such as instantaneous and local reactions and its ease in obtaining a high temperature through only a small electronic spark, laser beam, or other thermal sources. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Al/Ni multilayer materials have been studied to determine methods of controlling their thermal reaction characteristics for practical applications. [16][17][18] The Al/Ni multilayer material forms Ni-Al intermetallic compounds (IMCs) by receiving small energy from a thermal source such as a spark.…”

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.

“…aluminum). [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Usually, Al/Ni multilayer materials are fabricated by alternately stacking Al and Ni layers, which are a few tens of nanometers thick, by physical vapor deposition (PVD). Several papers on the fabrication of Al/Ni multilayer films by the PVD method have been published in the literature.…”

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.