An Electroless-Ag Reflector Developed for High-Brightness White LEDs

W. C. Liu, T. Y. Chung, Y. H. Chen, C. Y. Hsiao, C. P. Lin, C. Y. Liu

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


This study was conducted to investigate the reflectivity and the reflectivity stability of the electroless (Ag) metallization of reflectors used in high-brightness white GaN light-emitting diode packages. Two main reflector metallization schemes were studied: (1) electroless-Ag/electroless-pure-Pd/electroless-Ni plating and (2) electroless-Ag/electroless-Pd(P)/electroless-Ni plating. The reflectivity achieved using all reflector-metallization schemes was >85% in the visible range. However, in the electroless-Ag/electroless-pure-Pd/electroless-Ni reflector, reflectivity exhibited substantial thermal degradation; this was because of two principal factors: (1) the change in the surface morphology of the electroless-Ag surface grains; and (2) the alloying effect on the Ag layer exerted by the interdiffusion occurring with the underlying Pd layer. In this study, P was added to the Pd layer, and the thermal degradation of the annealed electroless-Ag/electroless-Pd(P)/electroless-Ni reflector was measured to be less than that of the electroless-Ag/electroless-pure-Pd/electroless-Ni reflector. The P content retarded the interdiffusion between the Ag and Pd(P) layers and preserved the faceted surface of the electroless-Ag layer, which enhanced the stability of the reflectivity of the electroless-Ag reflector. Furthermore, increasing the thickness of the electroless-Ag layer reduced the amount of Pd diffusing through the Ag layer, which helped retain the reflectivity of the Ag surface.

Original languageEnglish
Pages (from-to)4602-4609
Number of pages8
JournalJournal of Electronic Materials
Issue number12
StatePublished - Dec 2014


  • Ag reflector
  • electroless-Ag/electroless-Pd/electroless-Ni
  • light-emitting diodes
  • surface finishing


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