Polybrite's Unique plastics plating Technique - direct metallization plastics plating - Brief Article - Statistical Data Included

Automotive Finishing, Fall, 2001 by Beverly A. Graves

The traditional plastics plating process as compared to the direct metallization process is shown below.

Certain steps in the process need to be more closely controlled than others. During chromic acid reduction, where CrVI is reduced to CrIll, it is imperative that no CrVI compounds are carried over, since they will harm activation and metallization. In extreme cases it can even completely prevent metal deposition.

The activator is the most important step in the process, according to Mr. Brett. Parts emerge from the predip solution, which consists of hydrochloric acid and water. This protects the highly concentrated Pd activator from dilution. Palladium and tin are adsorbed from the activator onto the pretreated surface. They are adsorbed as clusters of a Sn/Pd colloid surrounded by SnCl. The cluster sizes are determined by the concentrations of hydrochloric acid and Sn. This influences the quantity of Pd adsorbed on the surface. (see Fig. 1) Rinsing follows to ensure that the catalyzed surface remains very clean.

If the activator is the most important step, the Cu-link is the second most important step in the process. During the direct metallization process, the Sn is replaced with Cu. The Cu-link solution contains copper ions bound to a biodegradable complexing agent. Depositing the copper onto the plastic makes the plastic electrically conductive, allowing it to be metallized directly in an electrolytic copper bath.

Maintaining the bath is not a complex process. Manual titrations are completed several times a day and posted in the lab and outside the line, as well as recorded in the computer system. Chemical additions, except for brighteners, are handled manually.

The lab at Polybrite is well equipped and sophisticated, capable of performing AA analysis, CASS tests, thermal cycling, thermal shock, Hull cell, wear resistance, microporosity and thickness tests, among others. Polybrite and its customers determine where samples are to be taken from the different parts. Samples are prepared and examined under the microscope. The software for the microporosity test automatically counts and records the pores in a given area of the part. The thickness of a part is automatically determined in seconds and recorded. Although the system is extremely accurate, it is actually only a backup to the more traditional testing the customers demand per their specifications.

Polybrite is focused on ensuring that its manufacturing processes are efficient and able to provide customers with the highest quality at a competitive price. Wherever possible, capacity has been expanded through the elimination of production bottlenecks and employing innovative processes to ensure increased demands can be met. A minimum of 7% of Decoma's (Polybrite's parent company) pre-tax profit is committed to research and development activities, generating processes and products that help the entire company remain at the cutting edge of the industry and ensuring the long-term viability of the company.