An analysis of intermetallics formation of gold and copper ball bonding on thermal aging

Murali, Sarangapani; Srikanth, Narasimalu; Vath, Charles J.

doi:10.1016/s0025-5408(03)00004-7

Cited by 114 publications

(63 citation statements)

References 5 publications

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“…Both papers draw essentially the same conclusion that FABs harden significantly during the copper bonding process. Another paper by Murali et al [30] compared intermetallic growth in gold and copper ball bonds and concluded that after 2 days ageing at 175°C there was little intermetallic growth in the [31] annealed copper ball bonds at 150°C, 250°C and 350°C and measured intermetallic thickness without a gold control annealed under identical conditions. Shear strengths are shown in Fig.…”

Section: Reliability Studies 2003 To Presentmentioning

confidence: 99%

What is the future of bonding wire? Will copper entirely replace gold?

Breach¹

2010

Gold Bull

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Thermosonic ball bonding is a major interconnect process in microelectronics packaging and is positioned to remain one of the key process technologies available to package designers in the near future. However, the main wire material used in fine pitch (FP) and ultra-fine pitch (UFP) ball bonding is gold and with significant increases in gold price, gold ball bonding has become a more costly process that has a considerable economic effect on the assembly of packages used in consumer electronics. An alternative wire material to gold is copper, which is much cheaper and has several technical benefits including better electrical conductivity and has been widely used in discrete and power devices with wire diameters typically larger than 30μm in diameter for many years. However, copper wire behaves quite differently than gold due to its different physical properties, some of which are beneficial and others detrimental to bonding performance. In this article, we briefly review some of the advantages and difficulties with using copper wire advanced packaging and explain why copper cannot replace gold in many applications and why gold offers significant benefits.

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Section: Reliability Studies 2003 To Presentmentioning

confidence: 99%

What is the future of bonding wire? Will copper entirely replace gold?

Breach¹

2010

Gold Bull

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“…Gold wire and copper wire are the preferred interconnection materials to bond with the aluminum metalized wafer pads during this process. 1,2) Gold is expensive, and the electrical conductivity and thermal conductivity of gold is lower than those of copper. 3,4) In addition, the inherent properties of higher tensile strength, hardness and stiffness of copper as well as its cost effectiveness compared to gold, have made it a preferred alternative.…”

Section: Introductionmentioning

confidence: 99%

Electric Flame-Off Characteristics and Fracture Properties of 20 μm Thin Copper Bonding Wire

et al. 2009

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In the present study, the neck fracture properties of annealed wire with ¼ 20 mm (0.8 mil) at 225 C for 1 hour and un-annealed wire were compared. In addition, the microstructural characteristics, the mechanical properties and the texture transition using EBSD methods before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that the recrystallization temperature of the as-drawn wire was $225 C, and the annealed copper wires possessed a fully annealed structure. Through recrystallization, the matrix structure transferred from long, thin grains to equiaxed grains and a few annealed twins. The microstructure of the free air ball (FAB) after an EFO process consisted of column-like grains, and grew from the heat-affected zone (HAZ) to the Cu ball. For the annealed and un-annealed wires, their preferred orientations on the wire and the neck were h100i == AD. Under the thermal effect of EFO, the orientation of the Cu balls were mainly h101i == AD and h111i == AD for annealed wires. Additionally, the hardness of the Cu balls and the strength of the neck sites of the EFO wires were able to affect the reliability of the copper wire bonding.

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“…Gold wire and copper wire are the preferred interconnect materials to bond with the aluminum metallized wafer pads during this process. 1,2) Gold is expensive, and the electrical conductivity and thermal conductivity of gold is lower than that of copper. 3,4) In addition, the inherent properties of higher tensile strength, hardness and stiffness of copper as well as its cost effectiveness compared to gold, have made it a preferred alternative.…”

Section: Introductionmentioning

confidence: 99%

“…So, the annealing treatment of as-drawn copper wire is very important. Many studies 2,3,6) have discussed the process variables such as bonding force, temperature and electric flame-off (EFO), etc. However, the recrystallization effect in the microstructure and the relevant mechanical properties of the thin copper wires ( ¼ 25 mm) have still not been examined.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, because the breakage sites of EFO wires are in the neck between HAZ and the ball, it's clear that the breakage result from the structure of the neck zones and stress affecting the breakage sites. 2,6,7) Thus, this paper not only investigated the mechanical properties of copper wire by varying the annealing temperature (at 150-250 C for 1 hour), but also investigated the fracture mechanism of the free air ball (FAB) with various annealing wires using EFO process.…”

Section: Introductionmentioning

confidence: 99%

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Recrystallization Effect and Electric Flame-Off Characteristic of Thin Copper Wire

et al. 2006

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Compared with gold wire, copper wire is cheaper and possesses lower cost, greater strength and better electrical conductivity, and therefore is becoming more commonly used. But the lower ductility and oxidation undermine the reliability of copper wire bonding, making the wire susceptible to breaking. In the present study, the annealed effect (at 150-250 C for 1 hour) on the tensile mechanical properties of copper wires with ¼ 25 mm (1 mil) was investigated. In addition, the microstructural characteristics and the mechanical properties before and after an electric flame-off (EFO) process were also studied.Experimental results indicate that with annealing temperatures of more than 200 C, the copper wires possessed a fully annealed structure, the tensile strength and the hardness decreased, and the elongation was raised significantly. Through recrystallization, the matrix structure transferred from long, thin grains to equiaxed grains and a few annealed twins. The microstructures of the free air ball (FAB) of the variation annealing wires after an EFO process were column-like grains. The column-like grains grew from the heat-affected zone (HAZ) to the Cu ball, and the preferred orientation was h100i. Under the thermal effect of EFO, the necks of the Cu balls underwent recrystallization and the grain growth was induced. Additionally, the decreased hardness and the strength of the HAZ resulted in the breakage sites of the EFO wires being in the HAZ near the Cu balls.

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An analysis of intermetallics formation of gold and copper ball bonding on thermal aging

Cited by 114 publications

References 5 publications

What is the future of bonding wire? Will copper entirely replace gold?

What is the future of bonding wire? Will copper entirely replace gold?

Electric Flame-Off Characteristics and Fracture Properties of 20 μm Thin Copper Bonding Wire

Recrystallization Effect and Electric Flame-Off Characteristic of Thin Copper Wire

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An analysis of intermetallics formation of gold and copper ball bonding on thermal aging

Cited by 114 publications

References 5 publications

What is the future of bonding wire? Will copper entirely replace gold?

What is the future of bonding wire? Will copper entirely replace gold?

Electric Flame-Off Characteristics and Fracture Properties of 20 &mu;m Thin Copper Bonding Wire

Recrystallization Effect and Electric Flame-Off Characteristic of Thin Copper Wire

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Product

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Electric Flame-Off Characteristics and Fracture Properties of 20 μm Thin Copper Bonding Wire