STTR Phase I: Low Temperature, Lead-Free Nanosolder for Microelectronics

这个小型企业技术转移(STTR)第一阶段项目旨在开发一种纳米材料方法，用于热敏微电子、纳米电子和MEMS器件的低温无铅焊接技术，该技术基于亚10 nm颗粒表现出的体熔融温度的降低。初步结果表明，这些合金纳米颗粒使用有机液体和助熔剂结合成糊状，在糊状受热时抑制纳米颗粒的氧化，可以产生高达30°C的凹陷。这种糊状颗粒可以与现有的微电子组装工艺形成互连。欧盟颁布的电子产品中消除了锡-铅焊料，导致行业广泛采用熔化温度明显高于被取代的锡-铅共晶合金的无铅焊料。传感器、系统级封装和MEMS器件等热敏元件勉强维持在183°C的锡铅共晶温度。随着熔化温度高于30°C的无铅合金的引入，在标准组装条件下可能会对关键的电子和MEMS组件造成重大损害。新技术的主要特点是使用直径约为5-10 nm的焊料合金纳米颗粒来创建熔点约为185°C的材料，比整体熔点低约30°。通过使用有机液体和受热时抑制纳米颗粒氧化的助熔剂将这些合金纳米颗粒结合成糊料，糊料可以与现有的微电子组装工艺形成互连。焊料合金纳米颗粒的熔化温度低于它们的块状粉末对应颗粒。然后纳米颗粒会结合在一起，当它们冷却时，会凝固。该技术的一个重要特点是，焊点一旦固化，由于其尺寸较大，其熔化温度将是整体熔化温度。因此，这项新技术允许分步焊接，其中热敏元件可以顺序连接，而不会在后续焊接步骤中损坏部件。

This Small Business Technology Transfer (STTR) Phase I Project is to develop a nanomaterials approach for a low temperature lead-free solder technology for heat-sensitive microelectronic, nanoelectronic and MEMS device that is based on the depression of the bulk melting temperature exhibited by sub-10nm particles. Preliminary results have shown a depression of up to 30ºC. With these alloy nanoparticles combined into a paste using organic liquids and a flux that suppresses nanoparticle oxidation as the paste is heated, the paste can be applied to form an interconnect with existing microelectronics assembly processes.The elimination of Sn-Pb solder in electronics enacted by the European Union has led to widespread industry adoption of Pb-free solders with significantly higher melting temperatures than the Sn-Pb eutectic alloy they replaced. Heat sensitive components, such as sensors, system-in-package, and MEMS devices, were barely surviving the 183°C eutectic temperature of Sn-Pb. With the introduction of Pb-free alloys that melt more than 30°C higher, significant damage can be done to critical electronic and MEMS components under standard assembly conditions. The key feature of the new technology is the use of solder alloy nanoparticles of approximately 5-10nm in diameter to create a material with a melting point of approximately 185°C, some 30° lower than the bulk melting point. With these alloy nanoparticles combined into a paste using organic liquids and a flux that suppresses nanoparticle oxidation as the paste is heated, the paste can be applied to form an interconnect with existing microelectronics assembly processes. The solder alloy nanoparticles melt at a lower temperature than their bulk powder counterparts. The nanoparticles will then coalesce and, as they are cooled, will solidify. An important feature of the technology is that once the solder joints are solidified, because of their large size, their melting temperature will be the bulk melting temperature. This new technology therefore allows for step soldering in which heat-sensitive components may be attached sequentially without damaging components with subsequent soldering steps.