金锡镀层在CSP气密封装中的应用及其可靠性

Application and reliability of Au-Sn electroplated layer on the CSP hermetical packaging

芯片级尺寸封装的气密性被越来越广泛的关注,为了实现CSP器件的可伐管帽与陶瓷基板之间的气密性互连,采用分层电镀沉积的方法在高温共烧陶瓷(HTCC)基板表面制备了金/锡/金镀层,利用金与锡间的共晶反应以实现管帽和基板的气密性可靠封接.文中分析了金/锡/金镀层质量、焊接工艺对Au80Sn20共晶焊料封接结果的影响.结果表明,金/锡/金镀层厚度和层间的结合力决定了Au-Sn共晶焊料的封接质量.在焊接升温过程中,锡镀层首先熔化形成“熔池”,溶解上下侧与之接触的金镀层,直至完成共晶反应;采用较短的焊接时间能够实现更好的金锡共晶封接;焊接温度为330℃、保温时间为30 s时,Au-Sn镀层共晶反应形成δ/(Au,Ni)Sn—ζ相—δ/(Au,Ni)Sn的分层共晶组织,实现了可伐管帽与HTCC基板的气密性封接.

Hermetical packaging in CSP component is increasingly investigated.In order to realize the hermetic interconnection between Kovar cap and ceramic substrate,the electroplating method was used and Au/Sn/Au sandwiched layers were fabricated on the HTCC substrate.Through the eutectic reaction between Au and Sn,a hermetic interconnection was realized.In this paper,the influence of Au/Sn/Au electroplated layer quality and soldering parameter on the packaging quality of Au-Sn eutectic solder was systematically investigated.It is found that the Au/Sn/Au electroplated layer thickness and interlayer bonding would directly determine the packaging results.During the soldering process,Sn electroplated layer firstly melted and a molten pool thus formed.The molten Sn then dissolved the surrounding Au electroplated layer and the Au-Sn eutectic reaction occurred.The shorter soldering time was better for the Au-Sn eutectic packaging.When the soldering temperature was 330℃and holding time was set to 30 s,the(Au,Ni)Sn—ζphase—(Au,Ni)Sn delaminated eutectic microstructures formed due to Au-Sn eutectic reaction and a reliable hermetical packaging between Kovar cap and HTCC substrate was eventually realized.