Improved package structure for reducing the thermal shock of high-power LD bar

초록

Thermal stress on the laser diode (LD) chip holder bends the LD-bar while it is operated at a high-power condition, and it is called ‘smile phenomenon’, which is apt to damage the LD bar module when repeated and beyond limit. We propose a micro-trench structure on the surface of chip holder to minimize the thermal stress by isolating the cumulative stress effectively without enlarging holder size or changing base materials. The trench depth needs to be optimized not to degrade thermal resistance, as while adequate depth of trench reduces the thermal stress effectively, excessive depth of trench might obstruct thermal flow from the heating source to heatsink. We analyzed the optimal depth through commercial simulation tool ‘SolidWorks’. The optimal depth is estimated at the thickness of 80-90% of the lower holder, and the thermal stress around the chip bar of HP condition is relieved by up to 70%.