LED flip-chip assembly with electroplated AuSn alloy

InGaN based high brightness (HB)‐LED chips have been fabricated and bonded to substrates that were coated with electroplated Au/Sn/Au solder. The assemblies yielded a forward voltage of 5.6 V and an optical output power of 42 mW when tested at 1,000 mA bias. The electroluminescence distribution was mapped with a CCD camera to determine the current spreading into the p‐contact region. Computational fluid dynamics (CFD) was used to check the effect of non‐uniform current spreading on the thermal resistance of the assemblies. We show that a good knowledge of the non‐uniform heat generation is required to obtain accurate modelling results. The bond strength of the AuSn solder joints exceeded the norm, when shear tested according to MIL‐STD‐883E (method 2019.5). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)