Low Temperature Bonding to 304 Stainless Steel for High Temperature Electronic Packages

沙竹軒 (加州大學爾灣分校材料暨製造科技博士班)

 

http://www.ectc.net/program/2010/60ECTCFinal.pdf

 

本篇研究中,於不使用助熔劑的低溫環境下,成功的運用銀銦雙合金系統在矽晶片和304不鏽鋼基板間以及兩片304不鏽鋼基板間形成完美鍵結. 於鍵結構思中,我們使用電鍍法在304不�鋼基板上形成多層銀銦結構.雖然嘗試了許多電鍍步驟及溶液,仍然無法直接將銀電鍍在304不�鋼基板上.目前為止,最成功的方法是先將一層鎳電鍍在304不�鋼基板上,再將一層銀電鍍在鎳上,形成不�鋼/鎳/銀結構.而如果在鍵結過程中,晶粒成長是必要的話,我們會對不�鋼/鎳/銀基板進行退火處理來增大銀的晶粒.在掃描式電子顯微鏡的觀察下,證明了幾乎完美的鍵結形成於矽晶片和304不�鋼鐵基板間以及兩片304不�鋼基板間.鍵結處是由銀,銀銦固熔體,三銀化銦,以及二銀化銦組合而成.鍵結溫度僅有190度C而鍵結處的熔點可高於650度C.我們期望這個新穎的鍵結方法能對高溫電子構裝有貢獻,同時,也能對於低溫304不�鋼鍵結有所幫助.

 

In this study, silicon (Si) chips were bonded to 304 stainless steel (SS) substrates using silver-indium (Ag-In) binary system without any use of flux. 304SS substrates were also bonded to 304SS substrates to develop low temperature fluxless processes to bond and seal two 304SS parts together. In the bonding design, Ag and In were deposited separately in layered structure. Various processes and solutions were experimented to plate Ag on 304SS. We have not found the process that could plate Ag directly on 304SS without an intermediate layer. So far, the most successful intermediate layer is nickel (Ni). Thus, Ni was plated on 304 SS, followed by Ag. The resulting 304SS substrates were annealed to increase Ag grain size if grain growth is needed for successful bonding. Nearly perfect joints were produced on Si to 304SS bonding and 304SS to 304SS bonding. The resulting joints are composed of Ag, Ag-rich solid solution (Ag), Ag3In, and Ag2In. The joints were fabricated at only 190oC of bonding temperature. The melting temperature of the joints exceeds 650oC. This new bonding process should be valuable for packaging electron devices that need high operating temperature. It is also useful for bonding 340SS parts together at low temperature.