Abstract
In this study, interfacial reactions between eutectic Sn-Pb and Sn-Ag-Cu with different solder volumes and electroless nickel/immersion gold (ENIG) surface finish are investigated. Soldering on copper finish has also been investigated for reference. Three different solder ball sizes (300, 500 and 700 μm) were used on the substrate surface finish pads with a diameter of 380 μm. The effect of solid state thermal ageing is also examined, focusing on the type of intermetallic compound (IMC) formed, the IMC thickness and growth rates. The results revealed that the solder volume has a significant effect on the thickness of intermetallics formed at the solder joints. The intermetallic formed in the solder with smaller volume was observed to be thicker than that in the solder with larger volume. It was also found that the eutectic Sn-Pb solder forms a thicker intermetallic and a much greater intermetallic growth rate compared to the Sn-Ag-Cu solder. Examination of solder joints microstructures revealed that several types and morphologies of intermetallics formed after reflow soldering and solid state ageing. However, the solder bump volume has no effect on the intermetallics types or morphologies. For the eutectic Sn-Pb solder, mainly Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> intermetallics formed at the solder joints whereas in the Sn-Ag-Cu solder joints (Cu, Ni) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> and (Ni, Cu) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> were observed. The investigation also revealed that more Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn intermetallics were observed just ahead of the solder joint interface and in the bulk of the Sn-Ag-Cu solder with the larger volume (solder ball with diameter of 700 μm).
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
