Polyquaternium-2: Applications in Cosmetics and as a Levelling Agent for Copper Electroplating

Polyquaternium-2 is a polymer that is used as an additive in cosmetics and personal care products. It has been shown to have diffraction, morphology, crystal structure and x-ray properties. It has a cationic charge and can be made basic by the addition of amines. The polymer can also be electrochemically plated with copper or tellurium. Polyquaternium-2 is a cationic surfactant of polyureylene ammonium salt, which can be used as leveling agent in alkaline zinc plating and providing a uniform distribution thickness over a wide range of current densities at a concentration of 2.0-5.0g/L. In addition, it is used in cosmetics, hair, skin onditioner, cleaning composition and etc.

Polyquaternium-2: A New Levelling Agent for Copper Electroplating

Copper (Cu) electrodeposition from acidic solutions has been used extensively by the microelectronic industry for interconnection in both Print Circuit Board (PCB) and integrated circuit (IC) applications.1 Conventionally, through-holes (THs) are used for the interlayer connections in multilayer Printed Circuit Boards (PCB) and it has been an important technology in the fabrication of multilayer PCBs. However, a through-hole suited to the finer scale of printed circuit boards is becoming difficult to produce. As the aspect ratio of the TH increasing, the difference of the plating thickness between the mouth and the center of the TH increase. The quaternary ammonium salts, being proved as effective levelling agent, have been used extensively in copper electroplating industry. However polyquaternium, a strong cationic polymer, having good water solubility, can be found in particular application such as in conditioners, shampoo and hair mousse, and has been rarely researched as a kind of leveler applied in copper electroplating. Herein we present a polyquaternium compound used as levelling agent for TH plating: Poly[bis(2-chloroethyl)ether-alt 1,3-bis[3-(dimethylamino)propyl]urea] (Polyquaternium-2), a commonly conditioner used in hair or skin care product. It is hypotoxic and can be used as additive for Zinc plating according to MSDS of Polyquaternium-2.[1]

Polyquaternium-2 bears two quaternary ammonium cations and two chloride ions in its molecule structure. Hence it may be a candidate for a levelling agent for copper electroplating. In the present paper, we focus on the effects of the innovative structures regarded as leveler in copper electroplating. The interaction between Polyquaternium-2 and copper surface was evaluated. The electrochemical behaviors of Polyquaternium-2 also were characterized. Interaction between Polyquaternium-2 and the copper surface The polished and cleaned copper surface treated without Poly quaternium-2 was used as a contrast. FE-SEM images of the polished and cleaned copper surface treated without or with Polyquaternium-2 were shown. It can be seen there are many trenches deriving from the polishing process. Compared sample showed a completed different morphology. There are many small particles with diameter of about 20–50nm existing on the surface of the copper. Moreover, the trenches deriving from the polishing process can hardly been observed after the copper surface being covered by those small particles. It could be considered that the adsorbed Polyquaternium-2 changed the morphology of copper surface.

It has been shown that Polyquaternium-2 is an effective levelling agent used for the TH copper electroplating from an acidic sulphate copper bath. The addition of Polyquaternium-2 could increase the cathodic polarization of the electroplating bath. The inhibitive effect of the Polyquaternium-2 was attributed to their adsorption on the copper surface shown by FE-SEM and XPS measurements. An excellent TH plating performance was obtained from a copper plating formula composed of 200ppm PEG, 50ppm Cl¹, 1ppm SPS, and 0.17µmol/L Polyquaternium-2. According to E-t curves analyses, the root cause for achieving excellent TH plating performance in the plating solution was attributed to the CDA behavior of this formula and the Polyquaternium-2 existed in plating solution could enhance this CDA behavior. The analysis based on the E-t curves also indicated that Polyquaternium-2 could be used as an effective levelling agent in the present of SPS and PEG.

References

[1]Chen, B., Wang, A., Wu, S., & Wang, L. (2016). Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath. *Electrochemistry*, *84*(6), 414-419. https://doi.org/10.5796/electrochemistry.84.414

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