Shunsuke Kanetsuki

Size effect in self-propagating exothermic reaction of Al/Ni multilayer block on a Si wafer

In this paper, the threshold size of sputtered Al/Ni multilayer blocks required for inducing a self-propagating exothermic reaction on a Si wafer is described. An Al/Ni multilayer film with a bilayer thickness of 100 nm is deposited on a Si wafer, and then micronsized Al/Ni multilayer blocks from the film are fabricated using a focused ion beam. By inducing small sparks in the vicinity of the blocks, we investigate reactivity. From scanning electron microscopy observations, we confirm that Al/Ni multilayer blocks with high aspect ratios and small widths can react easily. The effect of Al/Ni multilayer block size on reactivity is discussed from the viewpoint of heat conduction from the block to a Si wafer during an exothermic reaction.

Effect of thickening outermost layers in Al/Ni multilayer film on thermal resistance of reactively bonded solder joints

To reduce the thermal resistance of solder joints obtained by Al/Ni self-propagating exothermic reaction, we focus on the interface between the solder and the reactive Al/Ni multilayer before the reaction. We fabricate an Al/Ni film in which the outermost Al or Ni layer is deposited more thickly. By the laser flash method with response function analysis, the thermal resistance of the bonded specimens was measured in the case of thickening and non-thickening of the outermost layer. It is found that the resistance decreases with the thickness of the outermost layers, particularly the Ni layer. To investigate the influence of the amount of void on the resistance, scanning acoustic tomography (SAT), scanning electron microscope (SEM) observation, and field-emission electron probe micro-analysis (FE-EPMA) were carried out. Differences in the interfacial state between Ni-thickening and Al-thickening specimens are discussed in light of solder wettability, diffusion into the solder, and the type of intermetallic compound at the solder interface. It can be considered that thickening the outermost Ni layer has a great impact on decreasing the number of voids generated at the AlNi–solder interface even in low-pressure bonding, leading to reduction in the thermal resistance of solder joints.

Temperature behavior of exothermic reaction of Al/Ni multilayer powder materials based on cold-rolling and pulverizing method

In this paper, the characteristics of self-propagating exothermic reactions of an Al/Ni multilayer powder materials fabricated by a cold-rolling and powdering procedure are reported as initial findings of the first trial on a heat source for various applications with the energy-saving feature. Experimental results showed that, following the reaction of the developed Al/Ni multilayer powder materials in air atmosphere, the maximum temperature increased from approximately 1450 °C to over 1768 °C with increasing number of passes from 20 to 40 in cold-rolling. Furthermore, observations by scanning electron microscopy and crystallographic identification by X-ray diffraction measurements showed that the multilayer structure of powdered Al/Ni after 40 passes of cold-rolling was deformed, became thinner with below sub-micrometer thickness, and almost completely reacted to NiAl intermetallic compounds. It is possible that optimizing cold-rolling conditions enables us to control exothermic heat, which will be useful for heat sources.

20pm3-PM006 The evaluation of heat-affected zone on solder joints with self-propagating exothermic material Al-Ni multilayers

We measured heat of self-propagating exothermic reaction for Al/Ni multilayer with inducing electric spark at room temperature. We prepared the isoperibolic calorimeter for this measurement, and self-propagating reaction was induced in heating medium. As a result, the heat of reaction on the Al/Ni multilayer film 20μm thick was 1100~ 1200J / g. This is consistent with the DSC results in past studies.