A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient
Flip chip bonding technology on gold–tin (Au-Sn) microbumps for MEMS (Micro Electro Mechanical Systems) and 3D packaging is becoming increasingly important in the electronics industry. The main advantages of Au-Sn microbumps are a low electrical resistance, high electrical reliability, and fine pitc...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-12-01
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| Series: | Micromachines |
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| Online Access: | https://www.mdpi.com/2072-666X/14/12/2242 |
| _version_ | 1797379975609843712 |
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| author | Wenchao Wang Ziyu Liu Delong Qiu Zhiyuan Zhu Na Yan Shijin Ding David Wei Zhang |
| author_facet | Wenchao Wang Ziyu Liu Delong Qiu Zhiyuan Zhu Na Yan Shijin Ding David Wei Zhang |
| author_sort | Wenchao Wang |
| collection | DOAJ |
| description | Flip chip bonding technology on gold–tin (Au-Sn) microbumps for MEMS (Micro Electro Mechanical Systems) and 3D packaging is becoming increasingly important in the electronics industry. The main advantages of Au-Sn microbumps are a low electrical resistance, high electrical reliability, and fine pitch. However, the bonding temperature is relatively high, and the forming mechanism of an intermetallic compound (IMC) is complicated. In this study, Au-Sn solid-state diffusion (SSD) bonding is performed using the thermal gradient bonding (TGB) method, which lowers bonding temperature and gains high bonding strength in a short time. Firstly, Au-Sn microbumps with a low roughness are prepared by using an optimized process. Then, Au-Sn bonding parameters including bonding temperature, bonding time, and bonding pressure are optimized to obtain a higher bonding quality. The shear strength of 23.898 MPa is obtained when bonding in the HCOOH environment for 10 min at the gradient temperature of 150 °C/250 °C with a bonding pressure of more than 10 MPa. The IMC of Au-Sn is found to be Au-Sn and Au<sub>5</sub>Sn. The effect of annealing time on the IMC is also investigated. More and more Au<sub>5</sub>Sn is generated with an increase in annealing time, and Au<sub>5</sub>Sn is formed after Sn is depleted. Finally, the effect of annealing time on the IMC is verified by using finite element simulation, and the bonding strength of IMC was found to be higher when the bonding temperature is 150 °C at the cold side and 250 °C at the hot side. The temperature in the bonding area can reach 200 °C, which proves that the Au-Sn bonding process is solid-state diffusion because the temperature gradient reaches 2500 °C/cm. |
| first_indexed | 2024-03-08T20:31:49Z |
| format | Article |
| id | doaj.art-43d5fbb9f06642ecb1ca9a25d8a15b09 |
| institution | Directory Open Access Journal |
| issn | 2072-666X |
| language | English |
| last_indexed | 2024-03-08T20:31:49Z |
| publishDate | 2023-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Micromachines |
| spelling | doaj.art-43d5fbb9f06642ecb1ca9a25d8a15b092023-12-22T14:25:31ZengMDPI AGMicromachines2072-666X2023-12-011412224210.3390/mi14122242A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal GradientWenchao Wang0Ziyu Liu1Delong Qiu2Zhiyuan Zhu3Na Yan4Shijin Ding5David Wei Zhang6State Key Laboratory of Integrated Chips and Systems, School of Microelectronics, Fudan University, Shanghai 200433, ChinaState Key Laboratory of Integrated Chips and Systems, School of Microelectronics, Fudan University, Shanghai 200433, ChinaJiashan Fudan Institute, Jiaxing 314100, ChinaSchool of Electronic Information Engineering, Southwest University, Chongqing 404100, ChinaState Key Laboratory of Integrated Chips and Systems, School of Microelectronics, Fudan University, Shanghai 200433, ChinaState Key Laboratory of Integrated Chips and Systems, School of Microelectronics, Fudan University, Shanghai 200433, ChinaState Key Laboratory of Integrated Chips and Systems, School of Microelectronics, Fudan University, Shanghai 200433, ChinaFlip chip bonding technology on gold–tin (Au-Sn) microbumps for MEMS (Micro Electro Mechanical Systems) and 3D packaging is becoming increasingly important in the electronics industry. The main advantages of Au-Sn microbumps are a low electrical resistance, high electrical reliability, and fine pitch. However, the bonding temperature is relatively high, and the forming mechanism of an intermetallic compound (IMC) is complicated. In this study, Au-Sn solid-state diffusion (SSD) bonding is performed using the thermal gradient bonding (TGB) method, which lowers bonding temperature and gains high bonding strength in a short time. Firstly, Au-Sn microbumps with a low roughness are prepared by using an optimized process. Then, Au-Sn bonding parameters including bonding temperature, bonding time, and bonding pressure are optimized to obtain a higher bonding quality. The shear strength of 23.898 MPa is obtained when bonding in the HCOOH environment for 10 min at the gradient temperature of 150 °C/250 °C with a bonding pressure of more than 10 MPa. The IMC of Au-Sn is found to be Au-Sn and Au<sub>5</sub>Sn. The effect of annealing time on the IMC is also investigated. More and more Au<sub>5</sub>Sn is generated with an increase in annealing time, and Au<sub>5</sub>Sn is formed after Sn is depleted. Finally, the effect of annealing time on the IMC is verified by using finite element simulation, and the bonding strength of IMC was found to be higher when the bonding temperature is 150 °C at the cold side and 250 °C at the hot side. The temperature in the bonding area can reach 200 °C, which proves that the Au-Sn bonding process is solid-state diffusion because the temperature gradient reaches 2500 °C/cm.https://www.mdpi.com/2072-666X/14/12/2242flip chipAu-Snsolid-state diffusion (SSD)thermal gradient bonding (TGB)intermetallic compound (IMC) |
| spellingShingle | Wenchao Wang Ziyu Liu Delong Qiu Zhiyuan Zhu Na Yan Shijin Ding David Wei Zhang A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient Micromachines flip chip Au-Sn solid-state diffusion (SSD) thermal gradient bonding (TGB) intermetallic compound (IMC) |
| title | A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient |
| title_full | A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient |
| title_fullStr | A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient |
| title_full_unstemmed | A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient |
| title_short | A Method for Fast Au-Sn Bonding at Low Temperature Using Thermal Gradient |
| title_sort | method for fast au sn bonding at low temperature using thermal gradient |
| topic | flip chip Au-Sn solid-state diffusion (SSD) thermal gradient bonding (TGB) intermetallic compound (IMC) |
| url | https://www.mdpi.com/2072-666X/14/12/2242 |
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