Influence of Flow Rate and Current Density on Copper Deposition in Through Hole

With the development of CPU and GPU in tablet and laptop applications, lower thickness and lighter weight of packaging are required. To achieve this goal, materials in the package such as chip, substrate, microbump and BGA ball can all be considered to reduce its thickness. Among these materials, substrate is a solution since the thickness of core layer can be greatly reduced. Nevertheless, when a thinner substrate core is applied, the void formed in the through hole (TH) during copper-filled plating process is a challenge for substrate suppliers. The existence of a large-sized void may lead to crack or delamination failure during package reliability tests. This study focuses on exploring the influence of flow rate and current density on copper deposition in the TH to avoid void formation or minimize the void size. In conclusion, high flow rate and low current density condition is recommended. Less copper deposition at the protrusion of TH is helpful for avoiding void formation by preventing the TH opening closes earlier than TH center. Besides, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15 \mu \mathrm{m}$</tex> of copper thickness can be secured to prevent a large-sized void formation, which lowers the risk of package reliability failure.