Abstract The joining of sapphire with a Sn-3.5Ag-4Al solder was accomplished by a fast ultrasonic-assisted soldering (0.5 s) based on ultrasonic-assisted dipping in air at a low temperature of 250 °C. The sapphire joints were fabricated with different ultrasonic durations during the dipping. The uptrend of the shear strength of joints was composed of two processes: the formation of interfacial bonding and the interfacial strengthening. During the bonding process, the shear strength increased rapidly to 25 MPa on average as the dipping duration extended to 50 s. In the strengthening process, the shear strength of joints slowly increased and nearly doubled to 40 MPa as sapphires were dipped for 300 s. The interfacial microstructure was investigated by SEM and TEM to study the bonding and strengthening mechanisms of the sapphire/ Sn-3.5Ag-4Al joints. A transition layer of amorphous Al2O3 was found at the sapphire/ solder alloys interface and it is supposed to determine the bonding process of sapphire and the solder alloys. The Al enrichment layer and Ag3Al2 phases formed on top of the amorphous Al2O3 layer. These structures led to the formation of strong interfacial bonding between sapphire and the solder alloys, and thus improved the shear strength of the joints. The present results demonstrate the positive effects of Ag3Al2 and Al enrichment layer at the interface on the sapphire joints.

中文翻译：

---

Sn-3.5Ag-4Al焊料超声辅助焊接蓝宝石的键合强化机制

摘要 蓝宝石与 Sn-3.5Ag-4Al 焊料的接合是通过基于超声辅助浸渍在 250 °C 低温空气中的快速超声辅助焊接 (0.5 s) 完成的。在浸渍期间用不同的超声波持续时间制造蓝宝石接头。接头剪切强度的上升趋势由界面结合形成和界面强化两个过程组成。在粘合过程中，随着浸渍时间延长至 50 s，剪切强度平均迅速增加至 25 MPa。在强化过程中​​，随着蓝宝石浸渍 300 秒，接头的剪切强度缓慢增加，几乎翻了一番，达到 40 MPa。通过SEM和TEM研究界面微观结构以研究蓝宝石/Sn-3.5Ag-4Al接头的结合和强化机制。在蓝宝石/焊料合金界面处发现了非晶Al2O3 过渡层，它被认为决定了蓝宝石和焊料合金的结合过程。Al 富集层和 Ag3Al2 相形成在非晶 Al2O3 层的顶部。这些结构导致蓝宝石和焊料合金之间形成牢固的界面结合，从而提高了接头的剪切强度。目前的结果证明了界面处的 Ag3Al2 和 Al 富集层对蓝宝石接头的积极影响。这些结构导致蓝宝石和焊料合金之间形成牢固的界面结合，从而提高了接头的剪切强度。目前的结果证明了界面处的 Ag3Al2 和 Al 富集层对蓝宝石接头的积极影响。这些结构导致蓝宝石和焊料合金之间形成牢固的界面结合，从而提高了接头的剪切强度。目前的结果证明了界面处的 Ag3Al2 和 Al 富集层对蓝宝石接头的积极影响。