2012.1.10Nihon Superior Highlights IMC Differences between Low-Ag and No-Ag Lead-Free Solders
For Immediately Release
Cu and Ni are the decisive factor
OSAKA, Japan- January 10, 2012- Nihon Superior Co. Ltd., a supplier of advanced soldering materials to the global market, has highlighted the effectiveness of the Cu and Ni as the essential elements in forming a stable IMC layer in lead-free soldering.
The micrographs below come from a study undertaken by the University of Queensland to compare the Intermetallic layer at the interface between various lead-free solders and a copper substrate. The fluxed copper/OSP test boards were exposed to the solders for five seconds in a mini-wave machine with a pot temperature of 255°C. It was found that after 528h at 150°C the intermetallic compound on the board soldered with Sn-0.7Cu-0.05Ni, was smoother with slower growth of Cu3Sn and no cracking. By contrast the IMC layer in Sn-0.7Cu-0.3Ag and Sn-0.7Cu-0.3Ag-0.1Bi with additions of 0.3Ag and 0.3Ag+0.1Bi were uneven with growth of Cu3Sn and cracking. (Figure 2)
Figure 1．Micrographs before and after 528h at 150℃
Figure 2. Total thickness of IMC after 528h at elevated temperature
The Sn-0.7Cu-0.05Ni is the basis for Nihon Superior’s SN100C® solder that also incorporates a Ge addition as an antioxidant and flow promoter.
Silver-free, lead-free solder, SN100C now has a track record of more than 12 years of successful delivery of high productivity and high reliability. The first of the new SN100C Advantage Series®, SN99CN, builds on the strengths of the Sn-Cu-Ni formulation of SN100C with a controlled addition of silver. Both SN100C and SN99CN include Cu and Ni to form the stable IMC (Cu,Ni)6Sn5. These alloys will be exhibited under the theme “Implementing Lead-Free Soldering with Cost Reduction AND Reliability” at INTERNEPCON JAPAN 2012 to be held at the Tokyo Big Sight January 18 to 20 (Booth No. East 13-30, East Hall 6).