为了实现Al钎料对AlN的直接钎焊,提出了一种可以在熔化后自行去除表面Al₂O₃膜的镀膜Al箔钎料,以及提高Al钎焊AlN接头强度的升温钎焊方法,研究了表面气相沉积Ni/Al双层薄膜对Al箔表面Al₂O₃氧化膜的自去除作用,以及钎焊温度对接头强度提高的作用。结果表明,由于被Ni/Al双层薄膜掩埋,原Al箔表面的Al₂O₃氧化膜在钎料加热及熔化的过程中被破碎并卷入到含1%Ni (原子分数)的Al液中,实现了Al对AlN的无界面反应过渡层直接钎焊。采用升高钎焊温度的方法,可显著提高接头的强度。680 ℃钎焊时,由于Al液不润湿AlN,接头的断裂发生在Al钎缝与AlN的界面,剪切强度为79 MPa;随着钎焊温度的提高和润湿性的改善,Al/AlN的界面强度得到显著提高,接头的断裂逐步由界面转移至钎缝金属中,接头强度也相应逐步提高,并在840 ℃后达到最高值(146 MPa)。

The wettabilities of molten metals on ceramics are poor normally. In order to improve the wettability, all existing ceramic brazing methods introduce a compound transition layer formed by the reaction of active metal and ceramic. The transition layer between brazing seam and ceramic however creates negative effect on the properties of brazing joints. Although Al is the scarce metal which can wet some ceramics such as AlN and Al₂O₃ without reaction, the difficulty of removing oxide layer on surface prevents it being ceramic brazing filler. This work proposed a kind of coated Al foil filler able to remove its own Al₂O₃ film and an elevating temperature brazing process to enhance Al/AlN joint strength. Removing Al₂O₃ film effect of vapor deposited Ni/Al double layer film on Al foil and the effect of brazing temperature on improving joint strength were studied. The results showed that due to buried by Ni/Al double layer film, Al₂O₃ film on Al foil original surface broken and was swept in Al-1%Ni (atomic fraction) alloy liquid during heating and melting process. As a result, the direct brazing of Al to AlN without interface reaction transition layer was realized. The joint strength was significantly enhanced by elevating brazing temperature. When brazing at 680 ℃, the joint fractured along the interface between Al seam and AlN and the sheer strength was 79 MPa because of Al liquid not wetting AlN. With the elevating of brazing temperature, the wettability and interface strength of Al/AlN improved. The fracture gradually transferred to brazing seam from interface. The joint strength increased and reached to the maximum value of 146 MPa at 840 ℃.