A novel bumping process for fine pitch Sn–Cu lead-free plating-based flip chip solder bumps

10 µm fine pitch Cu/Sn micro-bumps for 3-D super-chip stack

“…3 shows the bump height variation of 10 µm pitch micro-bump. Average bump height is approximately 5 µm and height variation is approximately ±3 % (95%, 2σ), which is very uniform variation compared to conventional electroplated Cu/Sn bump [6].…”

“…Electroplating method is widely used in industry because of an advantage of high throughput. However, it has difficulty to form uniform height of bumps due to the variation of current density on a wafer [6]. Difference of bump heights can cause poor metal joining in fine pitch and high density micro-bumps.…”

“…Uniform bump height is significant factor to confirm stable micro-joining of fine size and high density micro-bumps. However, conventional electroplated Cu and Sn bumps had difficulty to form uniform height of bumps due to the variation of current density on a wafer [6]. Especially, it is more difficult to control uniform current density for the formation of fine pitch and high density micro-bumps.…”

Mechanical properties of Sn electrodeposited in supercritical CO2 emulsions using micro-compression test

“…Therefore, Sn is often used in electronic devices, such as solder bumps or part of a load bearing component. Electroplating is one of the best processes for manufacture of solder bumps [1]. However, formation of voids is often occurred in the Sn films fabricated by conventional method (CONV) due to H 2 evolution [2][3][4].…”

Impact of microbump induced stress in thinned 3D-LSIs after wafer bonding

“…In order to realize 3-D super chip with high I/Os, it is the prime requirement to have fine-pitch, uniform-height and low-resistance microbumps. However, in general there is a large height variation in the electroplated bumps due to the variation of current density on a wafer [2]. The un-even bump height can cause poor metal joining in the fine-pitch and high-density microbumps.…”