IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGY, VOL. 32, NO. 4, DECEMBER 2009 901 Solder Ball Attachment Assessment of Reballed Plastic Ball Grid Array Packages Lei Nie, Student Member, IEEE, Michael Osterman, Member, IEEE, Fubin Song, Jeffery Lo, S. W. Ricky Lee, Fellow, IEEE , and Michael Pecht, Fellow, IEEE Abstract—The ban of lead in consumer-based electronics by many countries has resulted in a dramatic reduction in the availability of electronic components with tin–lead terminations. With the uncertainty associated with lead-free reliability and the issues associated with mixing lead-free solder with tin–lead solder, medical, defense, and aerospace equipment manufacturers are examining and in some cases implementing reprocessing practices to convert lead-free terminations to tin–lead. For area array packages, the practice is referred to as reballing. While reballing has been used for part reclamation, very little information is available on the reliability of reballed parts. This paper presents lead-free ball grid array (BGA) packages subjected to two ball removal and two ball reattachment techniques. Solder attach strength was used as a metric to examine the reballing process. Both the ball shear test and the cold bump pull (CBP) test were used to test solder strength. The impact of isothermal aging was also examined. The solder strength of reballed BGAs remained at the same level when different reballing methods were used and under different aging conditions. The lead-free non-reballed BGAs had higher solder strength and wider strength distribution than reballed tin–lead BGAs. The pull strength increased as the pull speed increased in the CBP test. Index Terms— Ball grid array packages, ball shear, cold bump pull, lead-free, reballing, SnPb. I. I NTRODUCTION T HE EUROPEAN Union’s Directive on the Restriction of the Use of Certain Hazardous Substances in electrical and electronic equipment, which became effective on July 1, 2006, mandates that electronics industries replace tin–lead solder with lead-free solder. China, Japan, and other countries have also published environmental regulations to restrict the use of tin–lead solder [1]–[5]. Exemptions from lead-free legislation have been granted for certain products, especially those in- tended for life-critical applications. However, manufacturers with exemptions face a shortage of tin–lead ball grid array (BGA). Reballing technology, which substitutes new solder balls for the original ones, provides a solution. Reballing has Manuscript received July 31, 2008; revised March 20, 2009. First version published October 13, 2009; current version published November 20, 2009. Recommended for publication by Associate Editor K. Zhang upon evaluation of the reviewers’ comments. L. Nie, M. Osterman, and M. Pecht are with the Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD 20742 USA (e-mail: pecht@calce.umd.edu). F. Song, J. Lo, and S. W. R. Lee are with the Electronic Packaging Labo- ratory, Center for Advanced Microsystems Packaging, Hong Kong University of Science and Technology, Hong Kong (e-mail: rickylee@ust.hk). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TCAPT.2009.2021392 been used to salvage BGA parts, but today it offers a way to convert lead-free solder with tin–lead solder. The reballing process has two major steps: solder ball removal and solder ball reattachment. While the process of reballing has been around for some time, very little information exists related to the reliability of reballed BGAs. Since reballing changes solder balls, one measure of re- balling quality and reliability is the attach strength of the reattached solder balls. Two test methods exist to quantify solder ball attach strength: the ball shear test and the CBP test. The ball shear test is a destructive test conducted to determine the ability of ball BGA solder balls to withstand mechanical shear forces. JEDEC Standard JESD22-B117A offers guidelines to apply the ball shear test to BGA parts, to select the shear speed, and to define failure modes [6]. A substantial amount of literature has focused on the ball shear test on BGA components [7]–[11]. The CBP test is a relatively new destructive test method for assessing solder ball strength. The CBP test uses tensile force rather than shear force. Currently, there is no industry standard for the CBP test. In order to quantify the reliability and quality of reballed BGAs, both the ball shear and CBP tests were applied to reballed BGAs. For the study discussed in this paper, a set of 676 input–output (IO) and 256 IO lead-free (SAC305) BGAs were reballed. Two ball removal and two ball reattachment processes were examined. The ball removal process included solder wick and low-temperature wave solder. Ball reattachment methods included BGA preform and ball drop. Each of these processes is discussed in this paper. After reballing, the BGA parts were subjected to select isothermal aging. For the ball shear test, one tool speed was used. For the CBP test, two tool speeds were used. The failure modes and failure sites were documented. II. EXPERIMENT In this paper, two lead-free (SAC305) plastic overmold ball grid array (PBGA) parts were used to examine the impact of reballing lead-free BGAs to tin–lead BGAs. The reballing process involved two major steps: solder ball removal and solder ball reattachment. In this paper, two ball removal processes and two ball reattachment processes are examined. The solder wick and low-temperature wave solder processes were examined for ball removal. Solder ball preform and ball drop methods were examined for ball reattachment methods. Table I shows the reballing process used in this paper. The 1521-3331/$26.00 © 2009 IEEE Authorized licensed use limited to: CITY UNIV OF HONG KONG. Downloaded on August 17,2010 at 02:29:18 UTC from IEEE Xplore. Restrictions apply.