Pd effects on the reliability in the low cost Ag bonding wire

Cho, Jong-Soo; Yoo, Kyeong-Ah; Hong, Sung-Jae; Moon, Jeong-Tak; Lee, Yongje; Han, Wongil; Park, Heung-Woo; Ha, Seung-Weon; Son, Seong-Bum; Kang, Suk Hoon; Oh, Kyoung-Hee

doi:10.1109/ectc.2010.5490789

Cited by 24 publications

(13 citation statements)

References 3 publications

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“…The Cu-Al and Au-Al IMC growth kinetics were studied, and it was found that Cu-Al growth is at least 5× slower than Au-Al IMC [16]. However, copper wire bonding still pose reliability challenges and complex failure mechanisms which could be the main barriers to entirely replace gold wire bonding [17]. In this study, we have prepared FBGA 64 package assembled with gold and Pd-coated copper wire and load for unbiased HAST (UHAST), temperature cycling (TC), and HTSL tests.…”

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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“…Two intermetallic regions at the interface were identified as AuA1 2 + (Au, Ag) 4 Al and Ag 2 Al, respectively. The enthalpy of formation of Au aluminides is about one order of magnitude lower than Ag aluminides, which means that Au aluminides are easier to form than Ag aluminides fil In a thermal aging test of a ball bond on Al pad, the IMC layer grows faster by about 3 times for a pure Au than for a Au-30Ag alloy J1].…”

Section: Inh·oductioomentioning

confidence: 99%

Thermal Aging Behavior of Fine Pitch Palladium Coated Silver (PCS) Ball Bonds on Al Metallization

Gomes

Mayer

et al. 2015

International Symposium on Microelectronics

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Keywo1·ds: Fine pitch, Pd coated Ag wire bond, high temperature storage test, inten.netallic compotmd. Abstl'11ctTI1e high price of Au has motivated many to look for alternative bonding wire materials in the field of microelectronics packaging. In the present study, the reliability performance of palladium coated silver (PCS) wire in high temperature storage test (HTST) is carried out using 18 ~till diameter fine pitch PCS wire. Fine pitch ball bonds are made on Al metallization, with bonded ball diameter (BBD) of 32 ± 0.5 ~tm and ball height (BH) of 8 ± 0.5 µm . The aging temperature used in HTST is 170 °C and both shear and pull test are used to evaluate the aged ball bonds at regular time intervals. The shear force increases from 9.9 gf at 96 h to 12.5 gf at 192 h, and remains almost constant until 1344 h, and starts dropping gradually until 10.9 gf at 1848 h. The pad lift percentage recorded in pull test gradually drops from 90 % at 96 h to 20 % at 1008 h, and increases to 90 % at 1848 h. The chip side fractography after shear test indicates that the main failure modes are through pad at 96 h, tltrough ball bond at 504 h, and half of both at 168 h, respectively. Cross-sectional images show that the thickness of the intermetallic compound (IMC) layer growth follows parabolic relationship and the rate constant is 0.1 O ± 0.02 µm/h 112 . Gaps are observed along the periphery of the ball bond interface where no IMC is observed. The IM Cs are located at the center of the ball bond interface, and the width is 16.0-19 .3 µm at 96 h and 17 .2-22. 7 ~tm at 1344 h, respectively. Keywo1·d s: Fine pitch, Pd coated Ag wire bond, high temperature storage test. intennetallic compound. Inh·oductiooWire bonding is the most widely used in chip-scale interconnection technology in microelectronics packaging. Au ball-wedge bond is the most widely used in wire bonding industry due to its high bondability and acceptable reliability. However in some cases, alternative wires are preferred due to the high cost of Au.Cu wire costs less than Au, but readily oxidizes in air and requires shielding gas in free air ball (FAB) formation. Moreover, the high hardness of Cu FAB causes more Al pad splashing and higher chance of cratering.With its lower cost than Au as well as its higher resistance to oxidation and lower hardness than Cu, the poor reliability of Ag with Al metallization can prevent Ag from being a suitable alternative to Au. Recent studies hav e found that alloying Ag with Pd and/or Au can result in improved ball bond reliability on Al metallization. The presence of Pd at the bond interface proves to shown that wire annealing at 275 °C prior to bonding helps reduce the IMC growth rate at the ball bond interface of Ag-2Pd on Al pad.Although Ag alloy wire has better reliability than Ag wire, it has substantially lower electrical conductivity than pme Ag, and is more expensive to produc. e. Moreover, the Ag alloy wire FAB can be defective when the ball size is too small. For example, for a 95 % Ag alloy

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“…This allows improved bonding on bond pads coving active areas on devices with a less complex metallization stack. Cho et al (2010) studied the effects of per cent Pd content in Ag alloy which helped in improving the PCT reliability. The life time in PCT increased with increasing Pd concentration in the Ag wire: Ag-3 per cent Pd wire Ͼ Ag-1 per cent Pd wire Ͼ Ag wire.…”

Section: Silver Wirebondingmentioning

confidence: 99%

Future and technical considerations of gold wirebonding in semiconductor packaging – a technical review

Gan¹,

Francis²,

Chan

et al. 2014

Microelectronics International

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Purpose -The purpose of this paper is to provide a systematic review on technical findings and discuss the feasibility and future of gold (Au) wirebonding in microelectronics packaging. It also aims to study and compare the cost, quality and wear-out reliability performance of Au wirebonding with respect to other wire alloys such as copper (Cu) and silver (Ag) wirebonding. This paper discusses the influence of wire type on the long-term reliability tests. Design/methodology/approach -Literature reviews are conducted based on cost and wire selections of Au, Cu or Ag wirebonding. Detailed wear-out failure findings and wire selection with cost considerations are presented in this review paper. The future and the status of Au wirebonding in microelectronics packaging are discussed in this paper. Findings -This paper briefly reviews selected aspects of the Au ball and other alternative bonding options, focusing on reliability performance, and discusses the future of Au wirebonding in the near future in semiconductor packaging. Practical implications -The paper reveals the technical considerations when choosing the wire types for future microelectronics packaging. Originality/value -The in-depth technical review and strategies of the selection of wire types (Au, Cu or the latest Ag alloy) in microelectronics packaging are discussed in this paper based on previous literature studies.

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Pd effects on the reliability in the low cost Ag bonding wire

Cited by 24 publications

References 3 publications

Extended reliability of gold and copper ball bonds in microelectronic packaging

Extended reliability of gold and copper ball bonds in microelectronic packaging

Thermal Aging Behavior of Fine Pitch Palladium Coated Silver (PCS) Ball Bonds on Al Metallization

Future and technical considerations of gold wirebonding in semiconductor packaging – a technical review

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