Failure analysis of lead‐free solder joints for high‐density packages

Lau, John H.; Shangguan, Dongkai; Castello, Todd; Horsley, Rob; Smetana, Joe; Hoo, Nick; Dauksher, Walter; Love, Dave; Menis, Irv; Sullivan, Bob

doi:10.1108/09540910410537345

Cited by 19 publications

(10 citation statements)

References 5 publications

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“…The diffusion coefficients D ij a=b as well as the stiffness coefficients 2 can be found in literature, (Brandes and Brook 1992;Kittel 1962). The HGCs A ij ; a ij and b ij are calculated from atomistic theories as mentioned above.…”

Section: Materials Data For Ag-cumentioning

confidence: 99%

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Changes in the microstructure of materials and their impact on reliability: experiments and modeling

2008

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Several types of microstructural changes in microelectronic solder materials are briefly discussed, namely the formation of intermetallics, Kirkendall voiding, spinodal decomposition, and coarsening. Moreover, a theoretical framework, based on the entropy principle, is developed by means of which constitutive equations can be derived that are necessary to understand and simulate such processes. The resulting equations are specialized to binary alloys and then investigated numerically. Finally, simulations of spinodal decomposition and coarsening are performed for the eutectic solder AgCu. The theoretical predictions are compared with experiments.

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Section: Materials Data For Ag-cumentioning

confidence: 99%

“…Spinodal Formation of cracks at phase boundaries in eutectic SnPb(Lau et al 2004) Motion and deformation of a body with respect to a reference state 1 Throughout the whole article we use an index notation for vectors and tensors (e.g., v = v i , i = {1, 2, 3}) as well as the sum convention, i.e., v Á w = v i w i = R i v i w i .…”

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confidence: 99%

Changes in the microstructure of materials and their impact on reliability: experiments and modeling

2008

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“…After washing, samples are sputter coated with a thin layer of gold to facilitate the SEM inspection and EDX analysis. Most of the cross-sectional images from the SEM are obtained using a backscatter electron detector as this imaging mode gives a mostly atomic number-based contrast mechanism [4][5].…”

Section: Solder Joints Failure Analysismentioning

confidence: 99%

Key failure modes of solder joints on HASL PCBs and root cause analysis

Yao

Luo³

2013

2013 14th International Conference on Electronic Packaging Technology

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Over the last several decades, HASL (hot air solder level) coating has been one of the most robust finishes. During the HASL process, the copper surfaces of bare boards are first cleaned and coated with flux, the boards continue to be dumped into a lead or lead-free solder pot and finally the extra solder is blew out. As the intermetallic has already been formed in the HASL process, the HASL pads are easily soldered well because during the soldering process it is only need to reflow the solder. However, the HASL finishes still have several disadvantages such as lack of flatness on the pads and poor quality HASL finishes. Based on the authors' experience of long-term solder joints failure analysis, two kinds of key failure modes for HASL solder joints were introduced in this paper. One was poor wetting (nonwetting or de-wetting) of the solder to the HASL surface finish on PCB pads during soldering process, and the other one was solder joint crack, causing an electrical open. At the same time, several typical solder joint failure cases were used to show how the two kinds of failure modes occurred. Metallography microscope and SEM were used to reveal details of HASL pads surfaces and the fracture in the solder joints. The compositions of HASL pads surfaces were determined by EDX analysis. Additionally the failure mechanisms of both failure modes were investigated. The root cause for poor wetting is the poor quality HASL finishes which showed poor solderability. Exposed copper-tin IMC at the surfaces of HASL coating oxidized and was very difficult to wet during reflow. For solder joint crack, the reason is because the strength of solder joints was not enough to withstand the overstress. Finally, in order to prevent the two kinds of key failure modes, several suggestions were given.

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“…The dye staining analysis is commonly applied to verify whether solder joint cracks have occurred under BGA packages (Liu et al, 2010 andLau et al, 2004). The dye staining technology, which is a destructive test method used to reveal defects on the solder balls, relies on a liquid dye that penetrates existing micro cracks or under open solder balls.…”

Section: Dye Staining Analysismentioning

confidence: 99%