Fine pitch copper wire bonding in high volume production

Appelt, Bernd K.; Tseng, Andy; Chen, Chun-Hsiung; Lai, Yi‐Shao

doi:10.1016/j.microrel.2010.06.006

Cited by 52 publications

(16 citation statements)

References 25 publications

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“…The potentials and cost considerations of finding an alternative to replace gold wire bonding in microelectronic packaging are driven by new technologies coming to the market [1]. Copper wire bonding appears to be the alternate materials, and various engineering studies on copper wire deployment have been reported [2,3]. The Au-Al intermetallic compound (IMC) growth is widely characterized and analyzed [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Extended reliability of gold and copper ball bonds in microelectronic packaging

Gan

Francis²,

Chan³

et al. 2013

Gold Bull

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Wire bonding is the predominant mode of interconnection in microelectronic packaging. Gold wire bonding has been refined again and again to retain control of interconnect technology due to its ease of workability and years of reliability data. Copper (Cu) wire bonding is well known for its advantages such as cost-effectiveness and better electrical conductivity in microelectronic packaging. However, extended reliabilities of Cu wire bonding are still unknown as of now. Extended reliabilities of Au and Pd-coated Cu (Cu) ball bonds are useful technical information for Au and Cu wire deployment in microelectronic packaging. This paper discusses the influence of wire type and mold compound effect on the package reliability and after several component reliability stress tests. Failure analysis has been conducted to identify its associated failure mechanisms after the package conditions for Au and Cu ball bonds. Extended reliabilities of both wire types are investigated after unbiased HAST (UHAST), temperature cycling (TC), and high-temperature storage life test (HTSL) at 150, 175, and 200°C aging temperatures. Weibull plots have been plotted for each reliability stress. Obviously, Au ball bond is found with longer time to failure in unbiased HAST stress compared to Cu ball bonds for both mold compounds. Cu wire exhibits equivalent package and or better reliability margin compared to Au ball bonds in TC and HTSL tests. Failure mechanisms of UHAST and TC have been proposed, and its mean time to failure (t 50 ), characteristic life (t 63.2 , η), and shape parameter (ß) have been discussed in this paper. Feasibility of silver (Ag) wire bonding deployment in microelectronic packaging is discussed at the last section in this paper.

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Section: Introductionmentioning

confidence: 99%

Extended reliability of gold and copper ball bonds in microelectronic packaging

Gan

Francis²,

Chan³

et al. 2013

Gold Bull

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“…Au wire diameter has continued to decrease to 15 µm due to rising gold prices and shrinking pad size [5,6]. On the other hand, the rising gold price has motivated the packaging industry to look for alternative wire materials such as silver (Ag) and copper (Cu) [7][8][9][10][11]. Recently, several packaging companies have bonded Cu wires on Al bond-pads in production.…”

Section: Introductionmentioning

confidence: 99%

“…Since Cu wires get oxidized easily and exhibit higher hardness as compared to Au and Ag alloy wires, Cu wires possess a narrower process window for wire bonding. The high hardness of Cu could cause Al pads splashing, and the higher bonding force for Cu wire bonding could induce Si chip cratering [9]. In addition, Cu-Al wire bonds exhibit low corrosion resistance to halogen elements under high humidity.…”

Section: Introductionmentioning

confidence: 99%

A study on intermetallic compound formation in Ag–Al system and evaluation of its mechanical properties by micro-indentation

Lee

2017

J Mater Sci: Mater Electron

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In electronic packaging in recent years, silver (Ag) alloy wires have been widely adopted in wire-bond processes. The bond pads on the device chips are mostly aluminum (Al). Thus, the bonding interface is mainly Ag-Al. In recent Ag alloy wirebond publications, it is unclear what intermetallic phases form at the interface. In this research, experiments were designed to understand the Ag-Al intermetallic compound (IMC) formation in the Ag-Al system and evaluate its mechanical properties. First, the Ag-Al alloys with compositions from 19 to 43 at.% Al were evaluated to identify the phase equilibrium and crystal structure of the Ag-Al intermetallic phases. Microstructures and phase compositions of the designed Ag-Al alloys are presented. To further study the intermetallic compound formation at the Ag/Al interface, the interfacial reaction of the Ag/Al joints at 200 °C was investigated. The µ-Ag 3 Al and δ-Ag 2 Al IMC were identified to form at the Ag/Al interface and stabilize after long-time annealing at 200 °C. At last, deformation and fracture behaviors of the bulk µ-Ag 3 Al and δ-Ag 2 Al were analyzed by the micro-indentation. The measured results reveal that µ-Ag 3 Al exhibits significantly higher hardness and lower fracture toughness as compared to δ-Ag 2 Al. Indentation crack propagation in µ-Ag 3 Al demonstrates the fracture characteristics of brittle materials. In the case of δ-Ag 2 Al, the presence of slip bands exhibits the ductility of δ-Ag 2 Al to endure plastic deformation prior to fracture. The effect of the mechanical properties of the µ-Ag 3 Al and δ-Ag 2 Al IMC on the Ag-Al joint reliability is discussed. New information obtained in this research is important for future study of the joint reliability and failure mechanism of Ag-Al wire bonds.

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“…Recently, copper wire bonding appears to be the alternate materials and various engineering studies on copper wire development have been reported [1]. Technical barriers and reliability challenges of Cu wire bonding in microelectronics packaging are well identified [2][3][4][5][6][7][8][9][10][11]. Au-Al microstructure evolution and intermetallic compound (IMC) formation is widely studied by Karpel et al [12].…”

Section: Introductionmentioning

confidence: 99%

Evolution and investigation of copper and gold ball bonds in extended reliability stressing

Gan

Francis²,

Chan³

et al. 2014

Gold Bull

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This paper discusses the microstructure evolution of copper (Cu) and gold (Au) ball bonds after various extended reliability stresses such as biased highly accelerated temperature and humidity test (HAST), unbiased highly accelerated temperature and humidity test (UHAST), temperature cycling (TC), and high temperature storage life (HTSL) in BGA package. Objective of this study is to study the microstructure evolution and changes after long hours and long cycles of component reliability stressing and its predicted failure mechanisms and to determine the long-term reliability comparison with combination of bonding wires in HAST, UHAST, and TC. Secondary electron microscopy (SEM) and energy dispersive X-ray (EDX) have been carried out to understand the respective microstructure of failed samples in HAST, UHAST, TC, and HTSL long-term reliability failures. Respective failure mechanisms of copper and gold ball bonds carrion under HAST and UHAST, ball bond lifting in TC and HTSL have been analyzed and proposed. The evolution of surface morphology, including copper and gold ball bond micro cracking, gold ball bond Kirkendall microvoiding and intermetallic compound (IMC) formation, was studied in FBGA package with copper and gold ball bonds during various reliability stresses. Biased HAST, UHAST, TC, and HTSL mechanisms were proposed to explain the observed morphological changes and the resulting ball bond wear out modes after extended reliability stresses. Weibull reliability analyses have been established to compare the performance of copper and gold ball bonds under humid and dry environmental tests.

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Fine pitch copper wire bonding in high volume production

Cited by 52 publications

References 25 publications

Extended reliability of gold and copper ball bonds in microelectronic packaging

Extended reliability of gold and copper ball bonds in microelectronic packaging

A study on intermetallic compound formation in Ag–Al system and evaluation of its mechanical properties by micro-indentation

Evolution and investigation of copper and gold ball bonds in extended reliability stressing

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