Study on Ag-Plated Cu Lead Frame and Its Effect to LED Performance Under Thermal Aging

A systematic study about the effect of thermal aging time on lead frame morphology and LED optical performance was demonstrated in this paper. Three different lead frames for LED manufacturing were chosen to execute thermal aging test for reliability qualification. An evolution about Ag recrystalliz...

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Bibliographic Details
Published in:IEEE transactions on device and materials reliability 2014-12, Vol.14 (4), p.1022-1030
Main Authors: Lei Zhang, Yejun Zhu, Wei Wang, Xianghong Bi, Haibin Chen, Leung, Karina, Yeqing Wu, Jingshen Wu
Format: Magazinearticle
Language:English
Subjects:
Aging
AGING MECHANISMS
Alloys
Copper
Cu diffusion
DIFFUSION
Intermetallic compounds
LEAD FRAMES
Light emitting diodes
Morphology
Nickel
NUCLEATION
Nucleation and growth
Optical reflection
PLATE
PLATING
Reflectance
Reflectivity
Reliability
Silver
Surface morphology
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Summary:A systematic study about the effect of thermal aging time on lead frame morphology and LED optical performance was demonstrated in this paper. Three different lead frames for LED manufacturing were chosen to execute thermal aging test for reliability qualification. An evolution about Ag recrystallization, Cu diffusion, Cu nucleation, and growth on lead frame surface was comprehensively explained. The relationship between surface morphology and lead frame reflectance was first established by experimental characterization and comparison. After that, theoretical analysis based on diffusion theory reasonably explained the copper diffusion and nucleation process, which matches well with the morphology changes. Later on, optical simulation on various commercial LED packages was implemented to evaluate the effect of lead frame reflectance on the optical output. In conclusion, centering on Cu diffusion induces reflectance decrease, the connection initializes from thermal aging to final LED lumen performance was successfully built up in this paper. The findings can be directly applied as guidance to facilitate industrial LED manufacturing and reliability qualification.
ISSN:1530-4388
1558-2574
DOI:10.1109/TDMR.2014.2360081