Sains Malaysiana 43(1)(2014): 117–122

 

Reflow Soldering Process for Sn3.5Ag Solder on ENIG Using

Rapid Thermal Processing System

(Proses Pematerian Aliran Semula bagi Pateri Jenis Sn3.5Ag di atas ENIG Menggunakan

Sistem Pemprosesan Terma Pantas)

 

NOR ADHILA MUHAMMAD¹*, BADARIAH BAIS¹& IBRAHIM AHMAD²

 

¹Department of Electrical, Electronic and System Engineering, Faculty of Engineering

and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor

Malaysia

 

²Department of Electronics and Communication, College of Engineering UNITEN,

Jln IKRAM-UNITEN, 43000 Kajang, Selangor, Malaysia

 

Received: 15 October 2012/Accepted: 17 April 2013

 

ABSTRACT

A study on reflow soldering process for Sn3.5Ag solder on ENIG substrate was performed using the rapid thermal processing (RTP) system. The reflow soldering process by RTP system can be successful, but it is sensitive to some typical defects. A poor RTP system design can lead to significant temperature differences where non-uniform heating or cooling may result in material failure due to increase in thermal stresses or serious damage. From this study, it was found that at a peak temperature (Tpeak) of 251°C, the reflowed solder was observed to be smooth joint appearance over the solder pad and formed a regular joint shape of the solder due to the efficient reflow profile and sufficient heating input during the reflow process. The Ni3Sn4 intermetallic compounds were found to be continuous, thus resulting in a good metallurgical bonding between Sn3.5Ag solder and ENIG substrate. Meanwhile, an uneven reflowed solder and defect mechanism was detected at Tpeak of 246 and 260°C. This is due to the inadequate reflow profile and insufficient heating input during the reflow soldering process in the RTP system. Visual micrographs of reflowed solder and cross-sectional micrograph and elemental analysis were presented in this paper for better understanding of the defect mechanism in order to optimize the reflow soldering process using RTP system. The reflow soldering process can be performed better with appropriate reflow profile in the RTP system in order to achieve a good solder joint of Sn3.5Ag solder and ENIG substrate.

 

Keywords: Cross-sectional micrographs; elemental analysis; reflow profile; soldering defects

 

ABSTRAK

Kajian berkenaan proses pematerian aliran semula ke atas pateri jenis Sn3.5Ag di atas substrat ENIG telah dijalankan menggunakan sistem pemprosesan terma pantas (RTP). Proses pematerian aliran semula menggunakan sistem RTP boleh dilaksanakan dengan jayanya tetapi ia sensitif kepada kecacatan tipikal. Reka bentuk sistem RTP yang lemah akan menyumbang kepada perbezaan suhu yang signifikan dengan pemanasan atau penyejukan yang tidak seragam akan memberi kesan kepada kegagalan bahan disebabkan oleh peningkatan tekanan terma atau kerosakan yang serius. Daripada kajian ini, pateri yang telah mengalami proses pematerian aliran semula pada suhu puncak 251°C dikenal pasti mempunyai penyambungan yang licin pada pad pateri dan menghasilkan bentuk penyambungan pateri yang baik hasil daripada profil aliran semula yang lebih baik dan input pemanasan yang mencukupi semasa proses aliran semula pematerian dilakukan. Sebatian antara logam jenis Ni₃Sn₄ didapati berkeadaan selanjar lalu menghasilkan ikatan metalurgi yang baik antara pateri jenis Sn3.5Ag dan substrat jenis ENIG. Sementara itu, pematerian yang tak seragam dan mekanisme kecacatan diperhatikan terhasil pada pateri yang telah melalui proses aliran semula pematerian pada suhu puncak 246 dan 260°C. Ini adalah disebabkan profil pematerian aliran semula yang tidak memadai dan input pemanasan yang tidak mencukupi semasa proses pematerian aliran semula di dalam sistem RTP. Gambaran mikrograf pateri yang telah melalui proses aliran semula pematerian dan mikrograf keratan rentas dan analisis unsur bahan juga disampaikan di dalam kajian ini untuk lebih memahami mekanisme kecacatan yang berlaku di samping dapat mengoptimumkan proses pematerian aliran semula di dalam sistem RTP. Proses pematerian aliran semula dapat dijalankan dengan baik menggunakan profil aliran yang sesuai di dalam sistem RTP untuk mendapatkan penyambungan pateri antara pateri jenis Sn3.5Ag dan substrat jenis ENIG yang lebih baik.

 

Kata kunci: Analisis unsur; kecacatan pematerian; mikrograf keratan rentas; profil aliran semula

REFERENCES

Chih, T.P., Chia, T.K., Kuo, N.C., Terry, K. & Kenny, C. 2006. Experimental characterization and mechanical behavior analysis of intermetallic compounds of Sn-3.5Ag lead-free solder bump with Ti/Cu/Ni UBM on copper chip. Microelectronic Reliability 46: 523-534.

Ching, K.C., Shih, Y.H. & Cheng, C.Y. 2003. The effect of lamps radius on thermal stresses for rapid thermal processing system. Journal of Manufacturing Science and Engineering 125: 504-511.

Diepstraten, G. 2010. Selective Soldering Defects and How to Prevent Them. www.circuitnet.com/pdf/selective_sol.

Gilbert, B. 2001. Step by Step SMT Soldering: Reducing Soldering Defects, Loctite Corporation.

IPC/ JEDEC J-STD-020D.1. 2008. Moisture/ Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices.

Lau, J.H. 1991. Solder Joint Reliability: Theory and Application. New York: Van Nostrand Reinhold.

Lee, N.C. 2001. Reflow Soldering Process and Trouble Shooting, SMT, BGA, CSP and Flip Chip Technologies. 4th ed. Boston, MA: Newnes. pp.107-141.

Mu, C. & Liwei, L. 2001. Hermetic wafer bonding based on rapid thermal processing. Sensor and Actuators A 91: 398-402.

Ruihong, Z., Ran, Z., Fu, G. & Zhidong, X. 2009. Interfacial reaction between the electroless nickel immersion gold substrate and Sn-based solders. Microelectronic Reliability 49: 303-309.

Sharif, A., Chan, Y.C., Islam, M.N. & Rizvi, M.J. 2005. Dissolution of electroless Ni metallization by lead-free solder alloys. Journal of Alloys and Compounds 388: 75-82.

 

 

*Corresponding author: email: adhila@sirim.my