Mathematical Modeling of Electroplating in High Aspect Ratio Through‐Holes of Multilayer Printed Circuit Boards

Abstract

ance are shown in Fig. 3. The platinum loading for all cases is 1 mg/cm 2. The optimum platinum/Nation ratio is 1:1. Polymer fractions that are much higher than 0.5 are kinetically limited, and polymer fractions that are much lower than 0.5 are diffusion limited.The effect of platinum loading on MEA performance during discharge is shown in Fig. 4. MEAs with platinum loadings of 4.0, 2.0, 1.0, and 0.5 mg/cm 2 were simulated for e = 0.5 and a 50 mV applied potential across the catalyst zone. The best performance was achieved with a 1.0/cm 2 loading. The current densities are highest at the gas-membrane interface (x = 0). The local current density decreases rapidly in the catalyst zone for the case where the platinum loading was 4 mg/cm 2. Improved performance was achieved for the 1 mg/cm 2 loading, because the local current density was more uniformly distributed in the catalyst zone. ConclusionsThe model reported here is a useful tool which can be used to determine conditions where MEA performance is optimized. The structure of the catalyst zone has been shown to affect the performance of the MEA. When the particles are densely packed, the performance is gas diffusion limited, and when the particles are loosely packed, the performance becomes kinetically limited.

Characterization of Through-Hole Filling by Copper Electroplating Using a Tetrazolium Salt Inhibitor

“…Currently, microvia filling by copper electroplating is a necessary process for the advanced PCB fabrication of smart phones. [4][5][6][7] For TH metallization, the traditional plated through-hole (PTH) process [8][9][10][11][12][13][14][15][16][17] that creates only hole wall metallization does not meet the requirements for HDI, which include small holes, high conductivity and solid filled materials. [1][2][3] Alternatively, TH filling by copper electroplating is a process that has recently emerged to meet the HDI requirement of PCBs.…”

“…[1][2][3][18][19][20][21][22] However, uneven current density distributions and difficult mass transfers inside the THs, especially for a high aspect ratio (AR), commonly result in a subconformal deposition (i.e., a low throwing power and a copper overhang at the TH mouth). [8][9][10][11][12][13][14][15][16] These physical issues have been overcome by the use of chemical additives in the copper plating solution, which changes the secondary current density distribution due to the adsorption, consumption and desorption of these chemical additives inside the TH during copper electroplating. [18][19][20][21][22] Two typical chemical additives are nitrotetrazolium blue chloride monohydrate (NTBC) 19,23 and tetranitroblue tetrazolium chloride (TNBT), 20,21 and their molecular structures are illustrated in Fig.…”