Highly reliable and cost effective thick film substrates for power LEDs

Abstract

This paper presents Thick Printed Copper (TPC) as substrate technology for High Brightness LEDs, which features a strongly improved reliability combined with a significant cost advantage over incumbent technologies for High Brightness LED substrates. The advantages of TPC over Direct Bonded Copper (DBC) and Direct Plated Copper (DPC) substrates will be demonstrated by thermal shock test results and a demonstration of the versatile design options. The good thermal performance of TPC is demonstrated by comparative Finite Element Modelling of TPC and DBC substrates. A detailed review is given discussing the different copper to ceramic bonding mechanisms, which prevent void formation and are responsible for the excellent thermo-mechanical reliability

t‐ZrO2 toughened Al2O3 free‐standing films and as oxidation mitigating thin films on silicon nitride via colloidal processing of flame made nanopowders (NPs)

“…In this section, the sinterability, microstructures, and fractural toughness of ZTA films up to ~200 µm thick and ~ 2×2 cm 2 were investigated for possible application as power electronic substrates [11][12][13][14] using composition D from the above studies.…”

“…Alumina (Al 2 O 3 ) is a widely studied structural ceramic with applications as grinding media, for cutting tools, high‐temperature engine components, prosthetic implants, and substrates for power electronics due to its high melting point, excellent mechanical strength, hardness, and chemical stability as well as its widespread abundance 1–17 . However, applications using pure α‐Al 2 O 3 are limited by its low resistance to crack propagation, that is, poor fracture toughness (4‐5 MPa m 1/2 ) 18,19 that can lead to catastrophic failure 1–3 .…”

“…While thin films are suitable for applications such as electronic devices and protective coatings, for other structural applications such as wear components, dental composites, and prosthetic implants, bulk materials are also highly desirable. At the interface between bulk and thin films, intermediate thicknesses, for example, up to ~300 µm, are used as electrically insulating layers as well as high‐strength substrates for piezoresistive sensors and power electronics 11–14 . Finally, to test ZTA mechanical properties, greater thicknesses are preferred to prevent cracking caused simply by handling.…”

“…At the interface between bulk and thin films, intermediate thicknesses, for example, up to ~300 µm, are used as electrically insulating layers as well as highstrength substrates for piezoresistive sensors and power electronics. [11][12][13][14] Finally, to test ZTA mechanical properties, greater thicknesses are preferred to prevent cracking caused simply by handling.…”