David John Lacey

A comparison study on thermal characterization of high power leds with different ceramic attach adhesives for automotive lighting applications

In general, the increased electrical current used to drive head lamp LEDs has focused more attention on the thermal paths in the packages. Consequently, the increase in the heat flux can cause thermal runaway and catastrophic failures, limiting the full exploitation of the LED chip technology. The present study aims to develop highly thermal conductive composite materials, based on aluminium nitride (AlN) epoxy composites, as ceramic attach thermal adhesive layer for high power LEDs. Two different polymer matrices were employed to compound the AlN filled epoxy composites; bisphenol-A diglycidyl ether (D1) epoxy resin and a cycloaliphatic compound (Cl). Comparing D1 and C1 with the control glue system, it was found that control glue performed the best. D1 performed the worst with highest thermal resistance in the application. The material properties of the glues and the thermal transient measurement of head lamp LEDs are discussed extensively in this paper.

Study on thermal performance of high power LED employing aluminium filled epoxy composite as thermal interface material

The demand for high power light emitting diodes (LEDs) has spawned a dramatic revolution in illumination industry. However, the miniaturization of electronic devices especially LEDs have increased the need for highly sophisticated yet cost effective thermal management solutions in order to sustain this technological advancement. This paper elucidates the thermal behaviour of an LED employing metal filled polymer matrix as thermal interface material (TIM) for an enhanced heat dissipation characteristic. Highly thermal conductive aluminium were incorporated in bisphenol A diglycidylether (DGEBA) epoxy matrix to identify the effect of filler to polymer ratio on the thermal performance of high power LEDs. The curing behaviour of DGEBA was optimized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dispersion nature of the Al fillers into polymer matrix was verified with Field Emission Scanning Electron Microscope (FESEM). The thermal performance of synthesized Al filled polymer composite as TIM was tested with 5W green LED employing thermal transient measurement technique. Comparing the filler to polymer ratio, the rise in junction temperature for 60 % Al filled composite was higher by 11.0 °C than 50 % Al filled composite at cured state. In addition, it was also observed from the structure function analysis that the total thermal resistance was 10.96 K/W higher for 60 % Al filled composite compared to 50 % Al filled composite. On the other hand, a significant rise of 9.46 °C in the junction temperature between cured and uncured samples of 50 % Al filled polymer TIM was observed and hence the importance of curing process of metal filled polymer composite for effective heat dissipation has been discussed extensively in this work.