高密度互连印制电路板孔金属化研究和进展

doi:10.13208/j.electrochem.201119

摘要/Abstract

摘要：

孔金属化互连是印制电路板（PCB）高密度集成的核心制程之一,化学镀铜和电子电镀铜是实现孔金属化的关键技术。本文介绍HDI-PCB的概念和制作流程;综述化学镀铜和电子电镀铜孔金属化互连的研究和进展,包括溶液组成和操作条件的影响,添加剂及其相互作用机理,以及盲孔填充和通孔孔壁加厚机制;展望高密度互连印制电路板电子电镀基础研究及新技术发展方向。

关键词: 印制电路板, 孔金属化, 化学镀, 电子电镀, 添加剂

Abstract:

Printed circuit boards (PCBs) are almost the core components of all electronic systems. With the rapid development of sciences and technologies, PCBs are gradually developing in the direction of multi-layer, thin and high-density wiring due to the functionalization, miniaturization, lightweight and high reliability of electronic products, as well as the widespread popularization of the subminiature package such as chip scale package (CSP) and ball grid array (BGA). Therefore, High-density interconnected printed circuit boards (HDI-PCBs) arise. Hole metallization is one of the core technologies in HDI-PCBs and includes two processes composed of conductive treatment and electron electroplating. Electroless copper plating, as one of the conductive treatment methods, not only can deposit a copper layer with excellent conductivity and adhesion, but also has more reliable process maturity. However, reducing agent formaldehyde harms human health and environment. As a relatively eco-friendly and cheap reducing agent, hypophosphite is expected to replace formaldehyde in the process of the electroless copper plating if the copper deposition rate and the coating quality can be improved. Electron copper electroplating is closely related to the electrical properties of the electronic products. With the increase of PCBs integration, the diameters of holes decrease and the aspect ratios increase, which makes blind microvia and through hole more difficult to realize the superfilling and conformal thickening, respectively. For the superfilling of blind microvia, there are some mature models. But for the conformal thickening of through hole, there is no applicable theoretical guidance, and therefore, more studies are needed. It is very important to find suitable and novel additives besides the improvement of plating conditions for electron copper electroplating. In acidic sulfate copper electron electroplating process, although there are lots of studies on the additives, the interaction mechanism of the additives still needs to be further revealed, which not only contributes to understand the molecular mechanism of various additives, but also provides theoretical basis and guidance for the design and development of novel and efficient additives. In addition, the research and development of weakly alkaline and neutral electron copper electroplating process are also important for hole metallization of HDI-PCB. This paper firstly describes the concept of HDI-PCB, and then reviews recent studies and progresses on the electroless copper plating and acidic sulfate copper electron electroplating processes, which involves the effects of bath composition and operating conditions, the interactive mechanism of additives, and the filling and thickening mechanisms of the holes. Finally, the future directions towards basic research and novel electron electroplating development are highlighted.

Key words: printed circuit board, hole metallization, electroless plating, electron electroplating, additives

王赵云, 金磊, 杨家强, 李威青, 詹东平, 杨防祖, 孙世刚. 高密度互连印制电路板孔金属化研究和进展[J]. 电化学（中英文）, 2021, 27(3): 316-331.

Zhao-Yun Wang, Lei Jin, Jia-Qiang Yang, Wei-Qing Li, Dong-Ping Zhan, Fang-Zu Yang, Shi-Gang Sun. Studies and Progresses on Hole Metallization in High-Density Interconnected Printed Circuit Boards[J]. Journal of Electrochemistry, 2021, 27(3): 316-331.

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链接本文: https://electrochem.xmu.edu.cn/CN/10.13208/j.electrochem.201119

https://electrochem.xmu.edu.cn/CN/Y2021/V27/I3/316

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Application	Electronic product
Communication	5G, smartphone
Computer	Tablet computer, supercomputer
Automobile	Navigator, Millimeter-wave radar
Apparatus	Infrared spectrometer, muclear magnetic resonance analyzer
Aerospace industry	Satellite, missile, black box
Armarium	Electroencephalograph, microelectrode monitor
Industrial control system	Sensor, printer, unified remote

Electroless copper system	Advantage	Disadvantage
Formaldehyde	Technology maturity, good coating quality	Environmental pollution, toxic, strong alkaine
Glyoxylate	Fast deposition rate, nontoxic	Instability, high cost, active corrosion
Hypophosphite	Low cost, safe, weak alkaline	Requring catalytic active metal ions, high resistivity of copper layer
Protosalt	Eco-friendly, low pH, avoiding hydrogen gas evolution	Instability, low deposition rate

Bath composition	Bath 1	Bath 2
CuSO₄·5H₂O	220 g·L^-1	75 g·L^-1
H₂SO₄	60 g·L^-1	180 g·L^-1
Cl^-	60 mg·L^-1	60 mg·L^-1
Suppressor（PEG）	200 mg·L^-1	200 ~ 500 mg·L^-1
Accelerator（SPS）	1 mg·L^-1	1 mg·L^-1
Leveler（JGB）	0.5 ~ 3 mg·L^-1	2 mg·L^-1
Current density	2 A·dm^-2	1.5 ~ 2 A·dm^-2
Temperature	25 ^oC	28 ^oC
Agitation	Air	Air