Critical study of thermosonic copper ball bonding

Srikanth, Narasimalu; Murali, Sarangapani; Wong, Y.M.; Vath, Charles J.

doi:10.1016/j.tsf.2004.05.116

Cited by 72 publications

(33 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Au adjacent to the Au-Al interface also possesses a relatively high dislocation density, with subgrains forming inside the Au ball bond. The high density of dislocations is a result of the plastic deformation that happens during the wire bonding process; this also leads to strain hardening of the ball bond [10,11]. Thus, the microstructural changes across the deformed Au ball bond affect the mechanical properties and the strength of the Au ball bond.…”

Section: Microstructural Analysismentioning

confidence: 99%

“…Analysis of the microstructural changes in the ball bond during wire bonding has been conducted by several researchers [9][10][11][12][13][14][15]. This analysis has been limited to analysing the strengthening of the ball bond and has not examined the strengthening of the Au ball and the bond pad.…”

Section: Microstructural Analysismentioning

confidence: 99%

“…However, the results obtained from the various methods suggest that different types of mechanisms control thermosonic Au wire bonding. Some of the methods, namely footprint morphology, intermetallic coverage, microstructural and frictional bonding analyses, have concluded that solid-state diffusion is the main mechanism of thermosonic Au wire bonding [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. However, a new possible bonding mechanism (liquid-state diffusion) has been proposed based on TEM examinations [27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Some thoughts on bondability and strength of gold wire bonding

et al. 2012

View full text Add to dashboard Cite

The bonding mechanisms of gold, to give the desired strength of wire bonding, still require detailed investigation, including establishing adequate and reliable testing procedures. The current practices for analysing the mechanisms of wire bonding are inadequate and do not provide a comprehensive picture. This is because the focus of the tests is not clear, which causes variation in the results obtained, changing the conclusions about the responsible mechanism. Furthermore, as the size of Au wire bonds decreases, the mechanism responsible for thermosonic Au wire bonding may change. This paper provides a comprehensive analysis of the current and possible future methods for elaborating the bonding mechanism and strength of thermosonic Au wire bonds. We discuss the testing methods, their limitations and advantages, and suggest ways in which they can be improved.

show abstract

Section: Microstructural Analysismentioning

confidence: 99%

Section: Microstructural Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Some thoughts on bondability and strength of gold wire bonding

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Several studies set out to confirm that changes in the bonding process (smaller balls, lower bonding temperatures) did not alter the behaviour of copper ball bonds during bonding and reliability testing. The problems associated with copper ball bonding on aluminium alloy bond pads remained and Murali et al studied FAB hardness and cratering [28] in 25μm, 50μm and 75μm copper wires in 2003 and Srikanth et al [29] published similar data in 2004. Both papers draw essentially the same conclusion that FABs harden significantly during the copper bonding process.…”

Section: Reliability Studies 2003 To Presentmentioning

confidence: 99%

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

Breach¹

2010

Gold Bull

View full text Add to dashboard Cite

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.

show abstract

“…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. 3,5) In general, three factors affect the reliability of copper wire bonding 3,6) namely: 1.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2006

View full text Add to dashboard Cite

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.

show abstract

Critical study of thermosonic copper ball bonding

Cited by 72 publications

References 10 publications

Some thoughts on bondability and strength of gold wire bonding

Some thoughts on bondability and strength of gold wire bonding

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

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

Contact Info

Product

Resources

About