We report tin-lead (Sn-Pb) and low temperature lead free solder pastes for interconnecting structured ribbons. Lead free option was tin-bismuth (Sn-Bi) based engineered non eutectic alloy HRL1. We found an acceptable wettability and printability of both the solder pastes. These pastes show excellent stability, long stencil life and consistent transfer efficiency (>90 %). Solder joints were strong with peel strength more than 2N/mm and voiding less than 10 %, indicating bonds have better contacts and complete wetting. We found that solder paste based assemblies yield uniform intermetallic compound (IMC) formation and no loss in power output. Both pastes could be fast reflowed and laminated with EVA. The modules assembled using these pastes pass thermal-cycling and damp heat reliability testing according to IEC61215. Our results suggests that solder pastes could be an attractive alternative to expensive electrically conductive adhesives for interconnecting structured ribbons.
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