Substrate with integrated ESD protection packs more LEDs

Technology News | November 11, 2016

By Julien Happich

Automotive Optoelectronics

Marketed as CeraPad, the ultra-thin functional ceramic substrate will inherently protect any circuit designed on top of it against electrostatic discharges thanks to a finely embedded ESD structure able to clamp down discharges. With its low coefficient of thermal expansion of 6ppm/mK and a high thermal conductivity of 22W/mK, the thin substrate (300 to 400 µm thick) is well suited for customized chip-scale packages and multi-LEDs packages.

Based on ZnO ceramics sintered at low temperatures, CeraPad exhibits an ESD strength up to 25kV, more than three times higher than the standard 8 kV of state-of-the-art Zener diodes, claims manufacturer TDK.

A 16×16 LED array on the CeraPad substrate.

One implementation on display at electronica was a 16×16 LED matrix array whereby each one of the 256 LEDs sitting side by side could be controlled and switched on/off individually. The demonstrator packed dies only 0.7×0.7mm each, with built-in ESD protection directly sandwiched underneath.

With this sort of ESD integration, TDK claims a three-fold increase in density versus discrete ESD solutions (being five times thinner), effectively enabling large scale LED arrays for adaptive lighting with several hundreds of LED light points individually addressed.

According to Development Engineer Chen How Cheah at TDK’s Multilayer Piezo and Protection Devices Business Group, such an approach may prove more cost effective than designing large scale multi-pixel LED chips as recently demonstrated by Osram, since yield would be easier to control using individual known good LED dies picked and placed on a large scale CeraPad.

Demonstrating the individual control of LEDs
within the array, for complete adaptability.

Depending on customer requirements, the CeraPad contact pads can be designed for both standard SAC (Sn/Ag/Cu, 260 °C) reflow processes and eutectic bonding (AuSn, 320 °C).