无助焊剂甲酸回流技术在铜柱凸点回流焊中的应用

doi:10.16257/j.cnki.1681-1070.2024.0133

摘要/Abstract

摘要： 摩尔定律放缓，先进制程逼近物理极限，先进封装朝连接密集化、堆叠多样化和功能系统化方向发展，这一趋势使得铜柱凸点互连可靠性更具挑战性。回流焊是形成铜柱凸点的关键工艺，回流后凸点质量对于互连可靠性至关重要。对传统助焊剂回流用于铜柱凸点回流焊的劣势进行了简要阐述，综述了甲酸回流技术用于铜柱凸点回流焊的可行性，重点从还原效果、焊料润湿性、清洁性方面进行评述。概述了甲酸回流技术的原理和工艺流程，总结了其相较于助焊剂回流技术在产品质量、成本等方面的优势，并介绍了当下处于研究阶段的2种新型无助焊剂回流技术，展望了回流技术的未来发展趋势。

关键词: 先进封装, 铜柱凸点, 无助焊剂回流, 甲酸回流技术

Abstract: As Moore's Law slows down, advanced manufacturing processes approach their physical limits, and advanced packaging develops in the direction of connection densification, stacking diversification and functional systematization, making the reliability of copper pillar bump interconnection face greater challenges. Reflow soldering is a critical process for the formation of copper pillar bumps, and the quality of the bumps after reflow is critical to the reliability of the interconnection. The disadvantages of traditional flux reflow for copper pillar bump reflow soldering are briefly described, and the feasibility of formic acid ~~(FA)~~ reflow technology for copper pillar bump reflow soldering is summarized, focusing on the reduction effect, solder wettability and cleanliness. The principle and process flow of formic acid reflow technology are outlined, and its advantages compared with flux reflow technology in terms of product quality and cost are summarized. Two new fluxless reflow technologies in the research stage are introduced, and the future development trend of reflow technology is prospected.

Key words: advanced packaging, copper pillar bump, fluxless reflow, formic acid reflow technology

中图分类号:

TN405.97

刘冰. 无助焊剂甲酸回流技术在铜柱凸点回流焊中的应用[J]. 电子与封装, 2024, 24(10): 100401 .

LIU Bing. Application of Flux-Free Formic Acid Reflow Technology in Copper Pillar Bump Reflow Soldering[J]. Electronics & Packaging, 2024, 24(10): 100401 .

参考文献

[1] DENG Y, ZHAO X K, HE L, et al. Vacuum fluxless reflow technology for fine pitch first level interconnect bumping applications[C]// 2022 IEEE 72nd Electronic Components and Technology Conference (ECTC), San Diego, CA, USA, 2022: 1244-1248.
[2] DONG C C, PATRICK R E, SIMINSKI R A, et al. 活化氢气氛下的无助焊剂焊接[J]. 电子工业专用设备, 2016, 45(8): 1-4，34.
[3] LEE N C, BIXENMAN M. Flux technology for lead-free alloys and its impact on cleaning[C]// 27th Annual IEEE/SEMI International Electronics Manufacturing Technology Symposium, San Jose, CA, USA, 2002: 316-322.
[4] HE S L, NISHIKAWA H. Effect of substrate metallization on the impact strength of Sn-Ag-Cu solder bumps fabricated in a formic acid atmosphere[C]// 2017 International Conference on Electronics Packaging (ICEP), Yamagata, Japan, 2017: 381-385.
[5] HE S, NISHIKAWA H. Effect of heating conditions on void formation during soldering using formic acid atmosphere[J]. National Meeting of Japan Welding Society, 2016, 98: 158-159.
[6] 刘璐, 程东明, 卢显丽. 无助焊剂条件下SnAgCu/Cu钎焊接头金属间化合物的生长规律[J]. 热加工工艺, 2017, 46(13): 68-71.
[7] 孙广辉. 助焊剂残留对PCB的影响[J]. 印制电路信息, 2011, 19(S1): 209-213.
[8] BU?EK D, DU?EK K, R??I?KA D, et al. Flux effect on void quantity and size in soldered joints[J]. Microelectronics Reliability, 2016, 60: 135-140.
[9] CICERONE R J, STOLARSKI R S, WALTERS S. Stratospheric ozone destruction by man-made chlorofluoromethanes[J]. Science, 1974, 185(4157): 1165-1167.
[10] STOLARSKI R S, CICERONE R J. Stratospheric chlorine: A possible sink for ozone[J]. Canadian Journal of Chemistry, 1974, 52(8): 1610-1615.
[11] ROWLAND F S. Chlorofluorocarbons and the depletion of stratospheric ozone[J]. American Scientist, 1989, 77(1): 36-45.
[12] 邓明志, 刘建波, 郝伟, 等. 甲酸生产工艺及提纯方法[J]. 化工设计通讯, 2023, 49(9): 121-123.
[13] MATSUKI H, MATSUI H, WATANABE E. Fluxless bump reflow using carboxylic acid[C]// Proceedings International Symposium on Advanced Packaging Materials Processes, Properties and Interfaces, Braselton, GA, USA, 2001: 135-139.
[14] OZAWA N. Real-time measurement and studly of reduction process of copper oxide film by formic acid[J]. Journal of The Japan Institute of Electronics Packaging, 2017, 20(4): 219-227.
[15] OZAWA N, OKUBO T, MATSUDA J, et al. Observation and analysis of metal oxide reduction by formic acid for soldering[C]// 2016 11th International Microsystems, Packaging, Assembly and Circuits Technology Conference (IMPACT), Taipei, China, 2016: 148-151.
[16] OZAWA N, OKUBO T, MATSUDA J, et al. Sn- and Cu-oxide reduction by formic acid and its application to power module soldering[C]// 2018 IEEE 30th International Symposium on Power Semiconductor Devices and ICs (ISPSD), Chicago, IL, USA, 2018: 248-251.
[17] SAMSON M, OBERSON V, PAQUIN I, et al. Fluxless chip join process using formic acid atmosphere in a continuous mass reflow furnace[C]// 2016 IEEE 66th Electronic Components and Technology Conference (ECTC), Las Vegas, NV, USA, 2016: 574-579.
[18] 段祥飞. 半导体激光器封装及甲酸气体回流烧结技术[D]. 郑州: 郑州大学, 2016.
[19] HUANG S Y, CHANG T C, LIN Y M, et al. Reliability performance of 30μm-pitch solder micro bump fluxless bonding interconnections[C]// 2018 International Conference on Electronics Packaging and iMAPS All Asia Conference (ICEP-IAAC), Mie, Japan, 2018: 419-422
[20] SCHMEI?ER M, SCHUSTER J. Decomposition of formic acid[EB/OL]. [2024-05-29]. https://arxiv.org/abs/1108.5891v1.
[21] BI Y, HE S, LI W, et al. Wettability improvement of solder in fluxless soldering under formic acid atmosphere[C]// 2021 22nd International Conference on Electronic Packaging Technology (ICEPT), IEEE, 2021: 1-4.
[22] 闵志先. 无焊剂软钎焊技术研究[J]. 电子工艺技术, 2014, 35(1):19-21, 25.
[23] 毕宇浩. 甲酸气氛下无残留Sn-Bi焊点性能调控研究[D]. 桂林: 桂林电子科技大学, 2023.
[24] HE S L, BI Y H, SHEN Y, et al. Contact angle analysis and intermetallic compounds formation between solders and substrates under formic acid atmosphere[J]. Journal of Advanced Joining Processes, 2022, 6: 100118.
[25] MONTA M, OKIYAMA K, SAKAI T, et al. Formation of solder cap on Cu pillar bump using formic acid reduction[C]// 2012 IEEE 14th Electronics Packaging Technology Conference (EPTC), Singapore, 2012: 602-607.
[26] YANG W H, ZHOU C G, ZHOU J, et al. Cu film surface reduction through formic acid vapor/solution for 3-D interconnection[C]// 2018 19th International Conference on Electronic Packaging Technology (ICEPT), Shanghai, China, 2018: 1378-1381.
[27] LIN Y S, SHIH C H, CHANG W. Fluxless reflow of eutectic solder bump using formic acid[C]// Proceedings of the 2009 12th International Symposium on Integrated Circuits, Singapore, 2009: 514-517.
[28] 钱泳亮. 使用甲酸的无助焊剂回流方法及甲酸回流装置: CN105562870A[P]. 2016-05-11.
[29] LIN W, LEE Y C. Study of fluxless soldering using formic acid vapor[J]. IEEE Transactions on Advanced Packaging, 1999, 22(4): 592-601.
[30] HIDAKA N, NAGANO M, SHIMODA M, et al. Microjoining and assembly technology in electronics[C]// Effect of Addition Elements on Creep Properties of Sn-Ag-Cu Lead Free Solder, 2005: 171-176.
[31] CONTI F, HANSS A, FISCHER C, et al. Thermogravimetric investigation on the interaction of formic acid with solder joint materials[J]. New Journal of Chemistry, 2016, 40(12): 10482-10487.
[32] KANG H, LEE M J, SUN D, et al. Formation of octahedral corrosion products in Sn-Ag flip chip solder bump[J]. Scripta Materialia, 2015, 108: 126-129.
[33] JING L, KUDRIAVTSEV V, NGUYEN T, et al. Impact of process parameters on vacuum fluxless solder reflow performance in backend applications with bump pitch of 15μm and below[C]// 2023 IEEE 73rd Electronic Components and Technology Conference (ECTC), Orlando, FL, USA, 2023: 1541-1548.
[34] ARSLANIAN G K, DONG C C, PATRICK R E, et al. Fluxless soldering in activated hydrogen atmosphere[C]// 2020 International Wafer Level Packaging Conference (IWLPC), San Jose, CA, USA, 2020: 1-8.
[35] LEMIEUX P, TONG T, BROWN K. The benefits of a flux-free atmosphere for wafer bump reflow[C]// IEEE/CPMT/SEMI 28th International Electronics Manufacturing Technology Symposium, 2003. IEMT, San Jose, CA, USA, 2003: 335-337.
[36] DONG C C, PATRICK R E, ARSLANIAN G K, et al. Production-scale flux-free bump reflow using electron attachment[C]// 2017 China Semiconductor Technology International Conference (CSTIC), Shanghai, China, 2017: 1-3.
（—）（—）

中国半导体行业协会封装分会会刊

中国电子学会电子制造与封装技术分会会刊