Abstract: A heat exchanger suitable for cooling a heat source is provided, wherein a bypass channel formed in the heat exchanger has a width greater than a width of other channels to reduce a flow resistance of a fluid and a pumping power for driving a system. That is, under the same pumping power loss, more fluid is driven to achieve a better heat dissipation effect. By applying the heat exchanger, electronic devices are bonded to a top of the heat exchanger through a supporting substrate. In this way, heat generated when the electronic devices are is transferred to the heat exchanger through the supporting substrate and dissipated to the outside via the heat exchanger. Since the distance of heat transfer is decreased, the thermal resistance generated by an interface between the devices is reduced to improve heat transfer efficiency and heat dissipation effect.