Ultra-high Vacuum Bonding at Room Temperature Aided by Ultrasonic Wave

超声键合是一种通过在键合界面施加超声波来实现材料连接的方法。它已被广泛用作印刷电路表面安装技术中的引线键合工具。在空气中，Al可以与Si_3N_4、Al_2O_3、ZrO_2等多种陶瓷相连接，但其连接机理尚不清楚。为了阐明该机理，构建了可抽真空至超高真空并可控制接合气氛的接合装置。金属片和陶瓷片通过压力装置在焊头的尖端和砧座之间接触在一起，并在真空室中结合。结果表明，Al与Si_3N_4在真空和空气中都能实现连接。Cu与Si_3N_4在真空中不能键合，而在空气中可以键合。这些事实表明，键合的性质受气氛的影响。另一个重要的结果是，有一个区域的时间和压力，使键合成为可能。例如，Al与Si_3N_4的超声键合时间大于0.5s，键合压力大于30MPa，说明在金属与陶瓷的超声键合过程中存在热激活过程。

The ultrasonic bonding is a method to join materials by imposing ultrasonic waves on the bonding interface. It has widely been used as a wire-bonding tool in the surface mounting technology of printed circuits. A new attempt to use this method in bonding of metals to ceramics has been made and it has become clear that in the air, Aluminium can be joined to various ceramics like Si_3N_4,Al_2O_3,ZrO_2 and so on.But as for the bonding mechanism, a lot of points remains unknown. In order to clarify the mechanism, a bonding apparatus that can be evacuated up to an ultra-high vacuum and can control the bonding atmosphere was constructed. A metal sheet and a piece of ceramic are contacted together between a tip of horn and an anvil by a press device and bonded in the vacuum chamber. It was shown that Al can be joined to Si_3N_4 in the vacuum as well as in the air. Cu, on the other hand, could not be bonded to Si_3N_4 in the vacuum although the bonding was possible in the air. These facts are showing that nature of the bonding is affected by the atmosphere.Another important result is that there is the region for the time and pressure that makes the bonding possible. For example, Al can be joined to Si_3N_4 with the time longer than 0.5s and with the pressure more than 30MPa, which shows the existence of thermal activation process in the ultrasonic bonding of metal to ceramic.