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Vol.50, No.1, 71 ~ 78, 2012
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| Title |
| Effect of Heat Treatment on Mechanical Reliability of Solder Joints in LED Package |
| 고민관 Min Kwan Ko , 안지혁 Jee Hyuk Ahn , 이영철 Young Chul Lee , 김광석 Kwang Seok Kim , 윤정원 Jeong Won Yoon , 정승부 Seung Boo Jung |
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| Abstract |
| We studied the effect of heat treatment on the microstructures and mechanical strength of the solder joints in the Light Emitting Diode (LED) packages. The commercial LED packages were mounted on the a flame resistance-4 (FR4) Printed Circuit Board (PCB) in the reflow process, and then the joints were aged at 125℃ for 100, 200, 300, 500 and 1000 hours, respectively. After the heat treatment, we measured the shear strength of the solder joints between the PCB and the LED packages to evaluate their mechanical property. We used Pb-free Sn-3.0Ag-0.5Cu solder to bond between the LED packages and the PCBs using two different surface finishes, Electroless Nickel-Immersion Gold (ENIG) and Electroless Nickel-Electroless Palladium-Immersion Gold (ENEPIG). The microstructure of the solder joints was observed by a scanning electron microscope (SEM). (Cu,Ni)6Sn5 intermetallic compounds (IMCs) formed between the solder and the PCB, and the thickness of the IMCs was increased with increasing aging time. The shear strength for the ENIG finished LED package increased until aging for 300 h and then decreased with increasing aging time. On the other hand, in the case of an ENEPIG finished LED package, the shear strength decreased after aging for 500 h. |
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| Key Words |
| intermetallics, soldering, mechanical property, scanning electron microscopy, LED package |
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