黄锡峰,王运明,张武.基于石墨烯阻挡层Cu-In微纳米层超声波键合技术[J].表面技术,2023,52(12):456-463.
HUANG Xi-feng,WANG Yun-ming,ZHANG Wu.Ultrasonic Bonding Technology Based on Graphene Barrier Layer Cu-In Micro and Nano Layers[J].Surface Technology,2023,52(12):456-463 |
| 基于石墨烯阻挡层Cu-In微纳米层超声波键合技术 |
| Ultrasonic Bonding Technology Based on Graphene Barrier Layer Cu-In Micro and Nano Layers |
| 投稿时间：2022-11-03 修订日期：2023-08-08 |
| DOI：10.16490/j.cnki.issn.1001-3660.2023.12.040 |
| 中文关键词: 超声波键合 Sn-Ag-Cu 石墨烯 界面反应 扩散 |
| 英文关键词:ultrasonic bonding Sn-Ag-Cu graphene interfacial reaction diffusion |
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| 中文摘要: |
| 目的 采用松木状形貌铜铟微纳米层和超声能量，低温下实现键合互连，保证互连的可靠性，从而解决传统回流焊工艺高温引发高热应力、信号延迟加剧的问题。方法 将镀有松木状二级铜铟微纳米层的基板表面作为键合偶一端，另一端为无铅焊料。在键合偶之间加入单层共形石墨烯作为阻挡层，在低温下(温度120 ℃)，对键合接触区域施加超声能量和一定压力便可实现铜铟基板与无铅焊料的瞬态固相键合。用扫描电子显微镜、透射电子显微镜、X射线衍射(XRD)、焊接强度测试仪等分析键合界面处的显微组织、金属间化合物，以及剪切强度，对键合界面进行老化处理。结果 铜微米层具有圆锥状凸起的表面结构，其上镀覆纳米铟层，形成的结构具有巨大的表面积。在超声作用、较小的压力，以及低温条件下，铜铟松木状阵列结构插入较软的锡基焊料中，形成稳定的物理阻挡结构，实现与周围填充挤入的无铅焊料，以进行焊接互连。键合压力过小或者超声时间过长，都会在键合界面处产生线性孔洞或者裂纹，这些孔洞或者裂纹无法通过热处理消失。结论 石墨烯阻挡层避免锡焊料与粗糙表面铜基板之间直接接触，防止脆性金属间化合物的过度生长。铜铟松木状阵列结构的特殊形貌及超声波能量引入，键合在瞬间、低温条件下即可完成，键合质量良好，可以获得较小的键合尺寸。 |
| 英文摘要: |
| The copper indium micro nano layer with pine like morphology and ultrasonic energy are used to realize bonding interconnection at low temperature. The work aims to ensure the reliability of interconnection, and solve the problem of high thermal stress and signal delay caused by high temperature of traditional reflow soldering process. The surface of the substrate coated with pine like secondary copper indium micro nano layer was used as one end of the bonding couple, and the other end was lead-free solder. A monolayer of conformal graphene was added between the bonding couples as a barrier layer. At low temperature (120 ℃), the transient solid state bonding of copper indium substrate and lead-free solder could be realized by applying ultrasonic energy and certain pressure to the bonding contact area. A scanning electron microscope, a transmission electron microscope, an X-ray diffraction (XRD) and a welding strength tester were used to analyze the microstructure, intermetallic compound and shear strength at the bonding interface. The copper micro layer had a conical convex surface structure, which was coated with nano indium layer. The indium nano layer protected the conical copper array structure from air oxidation. The pine like copper indium secondary micro nano structure formed had a huge surface area. Under the condition of ultrasound, low pressure and low temperature, due to the nano size effect, the surface of pine like indium layer was highly meltable. The copper indium pine like array structure was inserted into the soft tin based solder to form a stable physical barrier structure, which could realize the welding interconnection with the surrounding lead-free solder. The thin indium layer at the bonding interface was rapidly diffused into intermetallic compounds (Cu6Sn5, Cu2In) under the action of ultrasonic energy. Cu2In was a high-quality phase with good mechanical properties, which was conducive to improving the interconnection strength. When the thickness of indium layer at the bonding interface was 300 nm, the bonding temperature was 120 ℃, the bonding pressure was 0.6 MPa, and the bonding time was 2.5 s, the optimal bonding quality was obtained, and the bonding interface pores disappeared. The average shear strength of the bonding interface was about 36 MPa, which was still a gap compared with the reflow soldering process, which could reach 43 MPa. If the bonding pressure was too small or the ultrasonic time was too long, linear holes or cracks would be generated at the bonding interface. These holes or cracks could not disappear through heat treatment. The monolayer conformal graphene barrier layer avoided direct contact between tin solder and copper substrate with rough surface. The copper tin reaction was slowed down and excessive growth of brittle intermetallic compounds was prevented. After aging at 160 ℃ for 100 h, the microstructure of the bonding interface had no obvious change. The interface composition was stable and no new holes were generated. As the graphene interlayer prevents dislocation expansion, the average shear strength of the bonding interface increased to 40 MPa. It was predicted that the long-term use process could maintain high reliability. The graphene interlayer can avoid the aging of the structure and improve the life of the bonding interface. Due to the special morphology of copper indium pine wood like array structure and the introduction of ultrasonic energy, the bonding can be completed in an instant and at low temperature. The bonding quality is good, and smaller bonding size can be obtained. |
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