The package substrates with through silicon plugs (or vias) described above provide lateral and vertical heat dissipation pathways for semiconductor chips that require thermal management. Designs of through silicon plugs (TSPs) with high duty ratios can most effectively provide heat dissipation. TSP designs with patterns of double-sided combs can provide high duty ratios, such as equal to or greater than 50%. Package substrates with high duty ratios are useful for semiconductor chips that generate large amount of heat. An example of such semiconductor chip is a light-emitting diode (LED) chip.