White Papers

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Papers by Dr. Hong-Sik Hwang

• A Compliant and Creep Resistant SAC-Al(Ni) Alloy

  by Dr. Ning-Cheng Lee, Dr. Hong-Sik Hwang, Dr. Benlih Huang

  Addition of Al into SAC alloys reduces the number of hard Ag3Sn and Cu6Sn5 IMC particles, and forms larger, softer non-stoichiometric AlAg and AlCu particles. This results in a significant reduction in yield strength, and also causes some moderate increase in creep rate. For high Ag SAC alloys, adding Al 0.1-0.6% to SAC alloys is most effective in softening, and brings the yield strength down to the level of SAC105 and SAC1505, while the creep rate is still maintained at SAC305 level. Addition of Ni results in formation of large (Ni,Cu)3Sn4 IMC particles and loss of Cu6Sn5 particles. This also causes softening of SAC alloys, although to a less extent than that of Al addition. Addition of Al also drives the microstructure to shift from near-ternary SnAgCu eutectic toward combination of eutectic SnAg and eutectic SnCu. Addition of Ni drives shifting toward eutectic SnAg. For SAC+Al+Ni alloys, the pasty range and liquidus temperature are about 4°C less than that of SAC105 or SAC1505 if the addition quantity is less than about 0.6%. Addition of Al and Ni also results in a slight decrease in modulus and elongation at break, although the tensile strength is not affected.

  Ni, Al, creep resistant, compliant, soften, SAC, lead-free, solder

  [Permanent Link to this Paper]

  Posted on 1 Jan 2009

• A Novel Flexible Silver Paste Enables Thin Film Photovoltaic Flex Solar Cells

  by Dr. Ning-Cheng Lee, James Slattery, Lee Kresge, Dr. Hong-Sik Hwang

  A flexible high performance Ag metallization paste LTTF-6363 has been developed for thin film photovoltaic flex solar cells. The binder of the paste is soft epoxy-based resin system. Compared with a thermoplastic paste system, LTTF-6363 exhibits superior adhesion and is flexible. These features enable the deployment of flex solar panels where tolerance against rolling or bending is critical. LTTF-6363 also displays excellent print characteristics and non-slump performance. This is extremely important for maximizing the effective open areas on solar cells. LTTF-6363 exhibits very good solderability, thus allows easy soldering connection with other electronic devices.

  Thin Film, volume resistivity, contact resistance, solar cell, photovoltaic, metallization paste, flex

  [Permanent Link to this Paper]

  Posted on 2 Mar 2010

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