Board Level Drop Reliability of Epoxy-Containing Sn-58 mass% Bi Solder Joints with Various Surface Finishes

Abstract

Board-level drop reliability testing under JEDEC (Joint Electron Device Engineering Council) drop conditions was conducted for lowtemperature Sn-58 mass%Bi solder joints. The effects of surface finish and the number of reflow processes (one, three, or five) on the drop reliability of the Sn-58Bi joints were evaluated. Three types of surface finishes were used including electroless nickel immersion gold (ENIG), electroless nickel electroless palladium immersion gold (ENEPIG), and organic solderability preservatives (OSP). We successfully fabricated six types of drop test specimens with various surface finishes and bonding materials, and then performed the board-level drop tests. The board-level drop reliability was improved when using the composite Sn-58Bi solder with epoxy as compared to Sn-58Bi solder without epoxy. In addition, the reliability of the Sn-58Bi epoxy solder/OSP joint was better than both the ENIG and ENEPIG surface finishes. When the number of reflow processes increased, the drop reliability showed two different behaviors; specifically, the reliability of the ENIG and ENEPIG surface finishes decreased while the OSP surface finish improved. The existence of epoxy in the solder paste improved the drop reliability of the solder joints. After drop testing, cracks propagated differently with different surface finishes, namely between Ni 3 Sn 4 IMCs and the Ni-P layer for the ENIG surface finish, between Ni 3 Sn 4 IMCs and the solder bulk for the ENEPIG surface finish, and within the solder bulk for the OSP surface finish. These data show that, when it is necessary to perform repeated reflow processes for electronic components, solder joints with an OSP surface finish provide better drop test reliability results.

Research Status of Evolution of Microstructure and Properties of Sn-Based Lead-Free Composite Solder Alloys

“…Ma and Wu [105] reported that the thickness of total IMC layers decreased by 56.31% compared with the plain Sn5-8Bi-0.7Zn solder joint when the doping of GNSs was 0.114 wt%. In addition, the suppress effect of the IMC was observed by the other researchers due to the doping of GNSs [36,38,106] and epoxy [59,60] into Sn-Bi solder.…”

“…Meanwhile, Yang et al [106] pointed out the UTS of Sn-Bi + 0:07 wt% composite solder had no obvious change compared with the plain solder, and the elongation and creep properties show a great improvement. Moreover, the improvement phenomenon of mechanical properties is observed by the other researchers due to the doping of GNSs [36,38,106] and epoxy [59,60] into Sn-Bi solder. [50] demonstrated that the doping of TiO 2 could have resulted in the refinement of microstructure of Sn-0.7wt%Cu-0.05 wt%Ni solder by the fabricate process of microwave sintered and the homogeneous (Cu, Ni) 6 Sn 5 intermetallics appear in the grains of particles.…”

Low Melting Temperature Sn-Bi Solder: Effect of Alloying and Nanoparticle Addition on the Microstructural, Thermal, Interfacial Bonding, and Mechanical Characteristics

“…Addition of nanoparticles or fibers like CNT, Y 2 O 3 , Al 2 O 3 , ZrO 2 , TiO 2 , Cu, and Ni to solders is another approach [23][24][25][26][27][28]. The epoxy-containing solders, which form an epoxy layer over the solder fillet, is also helpful to enhance shear strength and drop reliability [29][30][31][32][33]. Therefore, in this paper, we would like to introduce the significant results corresponding to the melting temperature, spreading and wetting, microstructure, inter-metallic thickness, and mechanical properties of Sn-Bi solder upon alloying and nanoparticle addition.…”

“…It was found that the number of drop impacts coincided with the shear failure energy trend [31]. Lee et al [29] investigated the drop reliability of epoxy-containing Sn-58%Bi solder joints with various surface finishes in the board level. The presence of epoxy in the Sn-58%Bi solder slightly improved the drop reliability for ENIG and ENEPIG surface finishes compared to the Sn-58%Bi solder joints without epoxy.…”