High-Throw DC Acid Copper Formulation for Vertical Continuous Electroplating Processes


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Abstract

The electronics industry has grown immensely over the last few decades owing to the rapid growth of consumer electronics in the modern world. New formulations are essential to fit the needs of manufacturing printed circuit boards and semiconductors. Copper electrolytes for high throwing power applications with high thermal reliability and high throughput are becoming extremely important for manufacturing high aspect ratio circuit boards.

Here we discuss innovative DC copper metallization formulations for hoist lines and vertical continuous plating (VCP) applications with high thermal reliability and throughput for high aspect ratio PCB manufacturing. The formula has a wide range of operation for current density. Most importantly, plating at high current density using this DC high-throw acid copper process offers high throughput, excellent thermal reliability, and improved properties for present-day PCB manufacturing. The operating CD range is 10–30 ASF where micro distribution of ≥ 85% for AR 8:1 is achievable. This formulation offers bright ductile deposits where plating parameters are optimized for improved micro-distribution and the properties of the plated copper deposit such as tensile strength and elongation. The thermal reliability and properties of the deposits were examined at different bath ages. Measured properties are: Elongation ≥ 18% and tensile strength ≥ 40,000 psi. All the additives can be easily controlled by cyclic voltammetry stripping (CVS) analysis.

Introduction

Copper has a high electrical conductivity and is relatively inexpensive compared to other high conductive metals such as silver. Therefore, the use of copper in the mass production of PCBs and semiconductors grew exponentially in the last few decades[1]. With today’s complex circuit board designs an even deposition with specific physical properties is necessary to meet the standards. Especially with high aspect ratios, through-hole plating to obtain desired plating distribution is much more challenging. During the quality control inspection, a board can be rejected if there is insufficient copper on the center walls of the through-holes. Moreover, plated copper should meet the minimum requirements of physical properties such as tensile strength and elongation (T&E) to withstand the high temperature applications[2].

To read the full version of this article which appeared in the August 2017 issue of The PCB Magazine, click here.

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