Effects of Brighteners in a Copper Plating Bath on Throwing Power and Thermal Reliability of Plated Through Holes

Electroplated Copper Additives for Advanced Packaging: A Review

Acid copper electroplating stands as a core technology in advanced packaging processes, facilitating the realization of metal interconnects, bumps, vias, and substrate wiring between transistors. The deposition quality of copper interconnect materials has a crucial impact on the final performance of chips, directly influencing their yield, reliability, and stability. In this intricate process, additives play a pivotal role in regulating the deposition quality and behavior of metal copper. This mini-review comprehensively summarizes the recent research progress in the field of electroplating copper additives for advanced packaging, both domestically and internationally, delving into the types and mechanisms of various additive molecules, including accelerators, inhibitors, and leveling agents. Through in-depth research on these additives, we gain a profound understanding of their specific roles in the electroplating process and the intricate interaction mechanisms among them, providing theoretical support for optimizing the electroplating process. Furthermore, this mini-review also delves into a thorough analysis of the current issues and challenges facing acid copper electroplating, exploring the key factors that constrain the further development of electroplating copper technology. Based on this analysis, we propose several potential solutions and research directions, offering crucial references for the development and application of electroplating copper additives in advanced packaging. In conclusion, this mini-review aims to provide a comprehensive perspective and profound understanding of the development and application of electroplating copper additives through a review and analysis of recent research progress, ultimately aiming to promote the further advancement of advanced packaging technology.

Concurrently Fabricating Precision Meso- and Microscale Cross-Scale Arrayed Metal Features and Components by Using Wire-Anode Scanning Electroforming Technique

In order to improve the thickness uniformity of the electroformed metal layer and components, a new electroforming technique is proposed-wire-anode scanning electroforming (WAS-EF). WAS-EF uses an ultrafine inert anode so that the interelectrode voltage/current is superimposed upon a very narrow ribbon-shaped area at the cathode, thus ensuring better localization of the electric field. The anode of WAS-EF is in constant motion, which reduces the effect of the current edge effect. The stirring paddle of WAS-EF can affect the fluid flow in the microstructure, and improve the mass transfer effect inside the structure. The simulation results show that, when the depth-to-width ratio decreases from 1 to 0.23, the depth of fluid flow in the microstructure can increase from 30% to 100%. Experimental results show that. Compared with the traditional electroforming method, the single metal feature and arrayed metal components prepared by WAS-EF are respectively improved by 15.5% and 11.4%.

Promotion of High-Speed Copper-Filling Performance for Interconnections with Increasing Aspect-Ratio Using Compound Additives

Interconnections are essential for integrating the packaging substrate, and defect-free copper-filling can further improve the reliability in through holes (THs). The coating properties and filling processes are mainly dominated by the interplays among additives in the direct current electroplating. The acidic copper sulfate electroplating solution contained three typical convection-dependent additives and chloride ions (Cl^-). The THs with aspect ratios (ARs) of 6.25, 5, and 4.17 (thickness of 500 μm) were selected as the study subjects. The effects of Cl^- and ARs on the interactions among the additives were investigated in detail using electrochemical measurements, which were verified by the THs filling experiments. The additive compounds present a convection enhanced inhibition effect and cathodic polarization, leading to a copper filling capacity increase with ARs and the amelioration of copper compactness and corrosion resistance. The defect-free copper filling of THs and a uniform mirror bright surface circuit can be achieved simultaneously using compound additives at a relatively high speed.

Ultra-Uniform Copper Deposition in High Aspect Ratio Plated through Holes via Pulse-Reverse Plating

The uniformity and microstructure of the copper deposition in the high aspect ratio plated through holes (penetrating holes) are crucial for the performance of printed circuit board. We systematically investigated the effects of reverse pulse parameters in the period pulse reverse (PPR) plating on the uniformity and microstructure of the copper deposition, including reverse pulse frequency, reverse pulse duty cycle and reverse pulse current density. The Cu deposition behavior (throwing power) and its crystallographic characteristics, including grain size, crystallographic orientation, and grain boundary, were characterized by means of field-emission scanning electron microscopy (FE-SEM), X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD). Our results clarify that the reverse pulse current density and duty ratio should be low to achieve the full filling and high uniformity of the through holes. The reverse pulse frequency of 1500 Hz would prevent the through holes to be fully filled. The copper electrodeposition in PTH prepared by double pulse electrodeposition has the good (111) surface texture and grain boundary distribution. This work demonstrated that the period pulse reverse (PPR) plating provides unique advantages in achieving the ultra-uniform copper deposition in the high aspect ratio plated through holes.

Improving the Performance of Aqueous Zinc-ion Batteries by Inhibiting Zinc Dendrite Growth: Recent Progress

Aqueous zinc-ion batteries (ZIBs) are promising candidates for the next-generation high-energy storage devices, owing to their resource availability, low cost, eco-friendliness, and high safety. The zinc (Zn) metal anode in a suitable battery system, including an electrolyte and a high-performance cathode electrode, can deliver an excellent electrochemical performance. However, several obstacles must be overcome to utilize aqueous ZIBs. Among these, Zn dendrite growth, corrosion, and side reactions severely impair the performance of rechargeable ZIBs. To deal with these issues, a profound understanding of the mechanism of the matter occurring in electrochemical cycles is essential to thoroughly solve the challenges. Instead of focusing solely on techniques for improving the performance of Zn metal anodes, this review delves into and summarizes the causes of side reactions and dendrite formation, thereby establishing a logical system of methodologies for improving the electrochemical performance of mild aqueous ZIBs. The correlation between the Zn metal anode, aqueous electrolyte, separators and the performance of ZIBs is also discussed in detail. There is also a brief perspective on the future development of Zn metal anodes in aqueous solutions. This study sheds a light on the challenges associated with the construction of high-performance ZIBs, which will significantly aid in their practical implementation.

A Life Prediction Model of Multilayered PTH Based on Fatigue Mechanism

Plated through hole (PTH) plays a critical role in printed circuit board (PCB) reliability. Thermal fatigue deformation of the PTH material is regarded as the primary factor affecting the lifetime of electrical devices. Numerous research efforts have focused on the failure mechanism model of PTH. However, most of the existing models were based on the one-dimensional structure hypothesis without taking the multilayered structure and external pad into consideration. In this paper, the constitutive relation of multilayered PTH is developed to establish the stress equation, and finite element analysis (FEA) is performed to locate the maximum stress and simulate the influence of the material properties. Finally, thermal cycle tests are conducted to verify the accuracy of the life prediction results. This model could be used in fatigue failure portable diagnosis and for life prediction of multilayered PCB.