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.

Reactively bonded solder joints with Al/Ni exothermic films attract much attention in semiconductor and microelectromechanical systems (MEMS) industries. Higher bond strength of the joints is required for long-term mechanical reliability. We have investigated the strength of rectangular-solid single crystal silicon (SCS) specimens with reactively bonded Sn-3.5Ag solder joint by using specially developed four-point bending test equipment. In this paper, the influences of Al/Ni exothermic film thickness and metallic interlayer on the strength are discussed. The strength increases with increasing Al/Ni film thickness and pressure load during bonding. Metallic interlayer between the solder and SCS also affects the strength because fracture origin is dependent on the types of metals. The obtained results suggest that reacted NiAl is durable against external forces compared with the solder and interlayer.

To realize the practical use of reactively bonded solder joints for thermally sensitive devices such as MEMS and electrical modules, we quantitatively measure the thermal resistance of solder joints fabricated by Al/Ni self-propagating exothermic reaction. By the laser flash method with response function analysis, the influence of bonding pressure on the thermal resistance of the reactive joints is investigated. The thermal resistance of the joints obtained by 3 MPa bonding is higher than that by 20 MPa bonding. By cross-sectional scanning electron microscopy (SEM) observation, many voids are found in the vicinity of the interface between the reacted AlNi and bottom-side solder layers in 3 MPa joints. In 20 MPa joints, a Ni-rich AlNi intermetallic compound instead of voids is produced around the interface. For reducing the thermal resistance of the reactive joints, the void generation mechanism is discussed in light of SEM observation and electron probe microanalysis (EPMA) analysis results.

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The study goal was to establish a standard industrial procedure for the measurement of thermal effusivity by a thermal microscope (TM), using a periodic heating method with a thermoreflectance (TR) technique. To accomplish this goal, a working group was organized that included four research institutes. Each institute followed the same procedure: a molybdenum (Mo) film was sputtered on the surface of Pyrex, yttria-stabilized zirconia (YSZ), alumina (Al 2 O 3 ), Germanium (Ge), and silicon (Si) samples, and then the phase lag of the laser intensity modulation was measured by the resultant surface temperature. A procedure was proposed to calibrate the effect of 3D heat flow, based on the analytical solution of the heat conduction equation, and thermal effusivity was measured. The derived values show good agreement with literature values. As a result, the TM calibration procedure can be recommended for practical use in measuring the thermal effusivity in a small region of the materials.