Enhanced Heat Spreading Performance of Printed Circuit Boards by Vapor Chamber Implementation

Efficient heat dissipation from active chips on printed circuit boards (PCBs) is crucial for high-power applications. Various techniques have been employed to reduce the chip junction temperature in microelectronic packages, including thermal via deployment, copper coin technology, and heat pipe (HP) integration. Vapor chambers (VCs), which operate similar to HPs by phase transformation and capillary action of the working fluid in a sealed enclosure, are gaining popularity for cooling electronic systems due to their superior heat dissipation capabilities. In this study, we designed a novel device called VC-integrated PCB (VCPCB) and investigated its total thermal resistance. The VCPCB device was fabricated by bonding a Cu lid to a Cu-clad FR4 substrate to form a planar cavity and filling the cavity with working fluid after evacuation. To ensure efficient capillary circulation of the working fluid within the VCPCB, a thin layer of dendritic Cu wick was electrodeposited on the Cu-clad FR4 substrate. The Cu wick layer, fabricated under optimal electrodeposition conditions, exhibits excellent capillary performance with a permeability (
$K$
) to effective pore size (
$R_{\text {eff}}$
) ratio of 1.0 ±
$0.09~\mu \text{m}$
. The VCPCB was hermetically bonded by melting a precoated Sn stripe at the periphery of the copper lid. The sealed VCPCB can achieve a vacuum level of
$4\times 10^{-3}$
torr after optimizing soldering and annealing processes. The VCPCB with a working fluid fill ratio of 60% achieves a thermal resistance of only 35% of the FR4 plate under an input heating power of 4–16 W. This study demonstrates a way to improve the heat dissipation performance of PCB substrates through direct implementation of the VCPCB device.