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

超声波键合是一种通过在键合界面上施加超声波来连接材料的方法。在印刷电路的表面贴装技术中，它被广泛地用作一种线键合工具。用这种方法进行了金属与陶瓷结合的新尝试，结果表明，在空气中，铝可以与Si_3N_4、Al_2O_3、ZrO_2等各种陶瓷结合。但关于成键机理，还有很多问题尚不清楚。为了弄清其机理，研制了一种可抽真空至超高真空并可控制键合气氛的键合装置。金属薄片和一块陶瓷通过压压装置在牛角的尖端和铁砧之间接触，并在真空室中粘合。结果表明，Al在真空和空气中都能与Si_3N_4结合。另一方面，Cu在真空中不能与Si_3N_4成键，而在空气中可以成键。这些事实表明，键合的性质受大气的影响。另一个重要的结果是，有一个区域的时间和压力使得键合成为可能。Al与Si_3N_4的结合时间大于0.5s，压力大于30MPa，表明金属与陶瓷的超声结合存在热活化过程。

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.