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Research Papers

Laser Soldering of Fine Pitch QFP Devices Using Lead-Free Solders

[+] Author and Article Information
Zongjie Han, Songbai Xue, Jianxin Wang, Xin Zhang, Liang Zhang

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing, P. R. C.

Shenglin Yu

College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing, People’s Republic of China; The 14th Research Institute, China Electronics Technology Group Corporation, 210013 Nanjing, P. R. C.

J. Electron. Packag 131(2), 021004 (Apr 01, 2009) (5 pages) doi:10.1115/1.3103932 History: Received November 20, 2007; Revised November 13, 2008; Published April 01, 2009

In this paper, soldering experiments of fine pitch quad flat package (QFP) devices were carried out when soldered with Sn–Ag–Cu and Sn–Cu–Ni lead-free solders by means of diode laser soldering system, and compared with the experimental results soldered with Sn–Pb solders and with infrared (IR) reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode and the fixed laser soldering time, an optimal power is obtained when the optimal mechanical properties of QFP microjoints are achieved. Mechanical properties of QFP microjoints soldered with laser soldering system are better than that of QFP microjoints soldered with IR soldering method. Results also indicate that adding rare earth element Ce to Sn–Ag–Cu and Sn–Cu–Ni lead-free solders improves mechanical properties of QFP microjoints, and the optimal amount of Ce is about 0.03%.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 2

Relation between laser output power and tensile force of QFP microjoints: (a) Sn–Ag–Cu microjoints and (b) Sn–Cu–Ni microjoints

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Figure 3

Tensile test of QFP microjoints soldered with two different kinds of methods

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Figure 4

Fracture microstructures of QFP microjoints soldered with Sn–Pb solder: (a) IR reflow soldering and (b) laser soldering

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Figure 5

Fracture microstructures of QFP microjoints soldered with Sn–Ag–Cu lead-free solder: (a) IR reflow soldering and (b) laser soldering

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Figure 6

Tensile test of QFP microjoints soldered with two kinds of methods: (a) Sn–Ag–Cu–Ce microjoints and (b) Sn–Cu–Ni–Ce microjoints

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Figure 1

Schematic of the diode laser soldering system

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