Effective (Pd,Ni)Sn4 diffusion barrier to suppress brittle fracture at Sn-58Bi-xAg solder joint with Ni(P)/Pd(P)/Au metallization pad

One of the major failure modes in lead-free solder joints is the brittle fracture at the solder/Cu pad interface under dynamic loading conditions. Such brittle fracture often leads to catastrophic premature failure of portable electronic devices. Therefore, it is desirable to design the package and the solder joints in such a way that brittle interfacial fracture can be avoided during drop test. To develop such design guidelines, we studied in this paper the dynamic failure of a single solder joint (SSJ). The SSJs with different geometry and substrate surface finish were prepared by laser-cutting from a BGA package assembled on a printed circuit board (PCB). The SSJs were tested under various shear loading rates, ranging from 5 mm/s to 500 mm/s. In conjunction with the experimental tests, finite element analyses (FEA) of these SSJ samples subjected to various loading rates were also conducted. Results from both experimental testing and numerical simulations show that the distribution of plastic strain near the solder/IMC interface is a key indictor of the failure mode. For a given sample geometry and loading rate, if the maximum solder plastic strain lies near the solder/IMC interface, the failure will be more likely to be ductile failure within the solder alloy. On the other hand, if the maximum plastic strain is mainly located at the edge of the interface between solder and the IMC layer with very little plasticity within the solder near the interface, brittle fracture of the IMC/Cu interface will be more likely to occur. Since numerically computing the plastic strain distribution in a solder joint is much easier than predicting joint failure, results of this study provide us with an effective means to predict the type of failure mode of a solder joint under dynamic loading.

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Effect of interfacial reaction layer on the brittle fracture of the SAC305 solder joint on ENIG and ENEPIG surface finish

2012 14th International Conference on Electronic Materials and Packaging (EMAP) ◽

10.1109/emap.2012.6507909 ◽

2012 ◽

Author(s):

Sang-Hyun Kwon ◽

Kang-Dong Kim ◽

Deok-Gon Han ◽

Tae-Hyun Sung ◽

Chang-Woo Lee ◽

...

Keyword(s):

Brittle Fracture ◽

Solder Joint ◽

Interfacial Reaction ◽

Surface Finish ◽

Reaction Layer ◽

Sac305 Solder ◽

Interfacial Reaction Layer

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Correlation Between Chemical Reaction and Brittle Fracture Found in Electroless Ni(P)/immersion gold–solder Interconnection

Journal of Materials Research ◽

10.1557/jmr.2005.0246 ◽

2005 ◽

Vol 20 (8) ◽

pp. 1931-1934 ◽

Cited By ~ 37

Author(s):

Yoon-Chul Sohn ◽

Jin Yu

Keyword(s):

Intermetallic Compound ◽

Brittle Fracture ◽

Solder Joint ◽

Chemical Reaction ◽

Solder Joints ◽

Interfacial Fracture ◽

Solder Interconnection ◽

Failure Locus ◽

Electroless Ni ◽

First Time

Occurrence of brittle interfacial fracture at an electroless Ni(P)/immersion gold–solder joint has long been a serious problem not yet fully understood. In our previous report on the electroless Ni(P) [J. Mater. Res.19,2428 (2004)], it was shown that crystallization of the Ni(P) film and growth of the Ni3SnP layer were accelerated after the intermetallic compound (IMC) spalling, and accurate failure locus of the brittle fracture due to so-called “IMC spalling induced microstructure degradation of the Ni(P) film” is presented for the first time in this communication. For Sn–3.0Ag–0.5Cu solder joints, (Ni,Cu)3Sn4and/or (Cu,Ni)6Sn5ternary IMCs formed at the interface, and neither spalling nor interfacial fracture was observed. For Sn–3.5Ag joints, Ni3Sn4compound formed, and the brittle fracture occurred through the Ni3SnP layer in the solder pads where Ni3Sn4had spalled. Since the Ni3SnP layer is getting thicker during or after Ni3Sn4spalling, control of IMC spalling is crucial to ensure the reliability of Ni(P)/solder system.

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