Development and Validation of a Novel Setup for LEDs Lifetime Estimation on Molded Interconnect Devices

Abstract

Higher energy efficiency, more compact design, and longer lifetime of light-emitting diodes (LEDs) have resulted in increasing their market share in the lighting industry, especially in the industries of consumer electronics, automotive, and general lighting. Due to their robustness and reliability, LEDs have replaced conventional light sources, such as fluorescent lamps. Many studies are examining the reliability of LEDs as such or investigating their long-term behavior on standard printed circuit boards (PCB). However, the thermal performance of LEDs mounted on nonconventional substrates is still not explored enough. An interesting example for this is the molded interconnect devices (MID), which are well known for the great design freedom and the great potential for functional integration. These characteristics not only underline the main abilities of the MID technology, but also present some challenges concerning thermal management. The long-term behavior of LEDs on MID is still quite untapped and this prevents this technology from consolidating its existence. In this context, this work highlights a developed test setup aimed at investigating LEDs, mounted on molded interconnect devices, under combined stress conditions. The results of the reliability study, as well as the resulting lifetime model, are also illustrated and discussed.

An Assessment of Thermoset Injection Molding for Thin-Walled Conformal Encapsulation of Board-Level Electronic Packages

“…This layout can also be effectively put into use for later implementation of inline failure detection during environmental tests in accordance with Refs. [11][12][13][14]. Figure 2 shows a CAD model of the demonstrator with a thin-walled encapsulation following the contour of the mounted devices.…”

A Novel Approach for Reliability Investigation of LEDs on Molded Interconnect Devices Based on FE-Analysis Coupled to Injection Molding Simulation

“…In this context, the lifetime model developed in previous works [3], [11], describes the relationship between the initial junction temperature and the characteristic lifetime of the LED. Therefore, the LEDs were tested under different ambient temperatures (25 • C, 85 • C, 105 • C) and were subject to two different forward current levels (75 mA, 100 mA).…”

“…The LEDs mounted on 3D heatsinks are tested under forward currents of 75 mA and 100 mA and by ambient temperatures of 85 • C and 105 • C. These heatsinks are made of LCP (liquid crystal polymer) based thermoplastics, which are filled with talc plates. The characteristic lifetime was determined as explained in the previous studies [3], [11] and the junction temperature was evaluated by two different simulation procedures. The first way, which is the most common and straightforward way, is to conduct a steady state thermal analysis (e.g.…”

“…surface mount devices SMD) assembled on MID, mathematical lifetime models have to be set up. In previous works [3], [11], a deep and detailed reliability investigation of LEDs mounted on MIDs was presented in accordance with the IES LM-80-08 test standard, the IES TM-21-11 estimation method [12] and the JEDEC and EIAJ standards [3], [13]- [16]. The choice of LED as an application example is due to the well-known and already proven dependence of its lifetime on the thermal performance of the substrate, it is mounted on.…”