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

超声连接是一种通过在连接界面施加超声波来连接材料的方法。在印制电路表面贴装技术中，它被广泛用作引线键合工具。将这种方法应用于金属与陶瓷的粘接是一种新的尝试，在空气中，铝可与各种陶瓷如Si_3N_4、Al_2O_3、ZrO_2等连接，但其结合机理尚不清楚。为了阐明键合机理，研制了一种可真空到超高真空、键合气氛可控的键合装置。金属片和陶瓷片通过按压装置在喇叭尖端和砧座之间接触在一起，并粘合在真空室中。结果表明，Al在真空和空气中均可与Si3N4连接。另一方面，铜在真空中不能与Si_3N_4键合，但在空气中可以键合。这些事实表明，键合的性质受到气氛的影响。另一个重要的结果是，存在使键合成为可能的时间和压力的区域。例如，Al在Si3N4中的连接时间大于0.5s，连接压力大于30 Mpa，表明金属与陶瓷的超声连接中存在热激活过程。

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.