Sintered Cu Paste as a Via-Filling Material for Through-Glass Via

We developed a sintered Cu paste that can be used as a filling material for through-glass vias (TGVs). A TGV substrate with a high-aspect-ratio via (aspect ratio: 11.1) can be filled with sintering Cu paste without voids or cracks using the vacuum-pressing method. The results showed that cracks and voids could be suppressed by combining the optimum amounts of small- and large-diameter Cu particles. A Cu film with the lowest volume resistivity of approximately$3.5 \mu \Omega$. cm was obtained at 350° C in a hydrogen atmosphere. Daisy chain samples were prepared using TGV substrates filled with Cu paste, and reliability tests were conducted. The changes in the resistance of the daisy chain samples after the reliability tests [thermal cycle test$\left(-55 / 125{ }^{\circ} \mathrm{C}, 1000\right.{}$cycles), high-temperature storage test ($150^{\circ} \mathrm{C}-1000 \mathrm{h}, 260^{\circ} \mathrm{C}-10 \mathrm{h}$), unbias high-accelerated-stress test, pressure cooker test, and reflow cycle test (maximum temperature: 265° C, 10 times,$\left.\mathrm{N}_{2}\right)$] were within 3% of the initial value. It is possible to fill the vias by sintering the Cu paste up to a board size of$510 \times$515 mm. The developed Cu paste is suitable as a filling material in TGV substrates.