Robust tuning of Kirkendall void density in circuit interconnections through substrate strain annealing

Abstract

Unpredictable Kirkendall void formation at the interface of circuit interconnections underlies degradation in electronics, yet there is a lack of effective approaches to curb the amount of these voids. Here we developed a strain-anneal method to tailor grain size distributions in the copper substrate of interconnections, and demonstrate quantitatively that not only the removal of the impurities but also an increase in the grain size of the substrates leads to an appreciable decline in the void density. The interconnections on the substrate recrystallized at a high annealing temperature show the massive porosity and the increased sensitivity of the voiding to the grain size. Our findings have broad implications for manipulation of void propensity in many other hetero-interfaces and are essential for high-performance circuit bonding in high temperature/high power electronic devices based on wide band gap semiconductors.

Effect of Free-standing Al/Ni Exothermic Film on Thermal Resistance of Reactively Bonded Solder Joint

“…As a common understanding, grain size is fully influenced by annealing temperature and time because a crystal grain grows at elevated temperatures. (26,27) If this knowledge is applied, the solder layer in the as-sputtered Al/Ni joint would be expected to be subjected to heat generated by an Al/Ni exothermic reaction more than that in the free-standing Al/Ni joint. That is, the heat-affected solder area would be smaller in the case of using the free-standing film.…”

“…In a solder layer deposited by sputtering on a Si substrate, a minute tensile stress is thought to be produced at room temperature because the thermal expansion coefficient of SnAg is clearly higher than that of Si. (26,27) Owing to stress balancing, a small compressive stress is thought to be produced in the Si and Al/Ni layers in the vicinity of the SnAg-deposited interface. Before bonding, there is no stress in the free-standing Al/Ni film, whereas there is a stress slope in the assputtered Al/Ni film because of the small tensile stress generated in the solder layer.…”

Electrohydrodynamic Printing of High‐Resolution Self‐Reduced Soldered Silver Nanowire Pattern for Wearable Flexible Strain Sensors

“…[13,14] Contact printing methods, including gravure printing and screen printing, need a mask that still limits their printing resolution. [15][16][17] Therefore, non-contact printing technologies with relatively higher resolution are widely used for electronic devices. [18] But the resolution of non-contact printing technologies is usually limited by the nozzle, whose size is at the same scale of the printing resolution.…”