A clean metal surface is essential for wire bonding. Metal surfaces can be cleaned using three different plasma processes, each with its own effect and different treatment results. The first process, neutralisation, involves the removal of both surface charge as well as statically bound dirt, such as dust particles. This is done by the charge carriers of the Openair Plasma treatment. In the second process, using evaporation, the volatile components such as moisture and VOCs (volatile organic compounds) are eliminated by the thermal effect of the Openair Plasma treatment. The final cleaning process is oxidation, which removes organic contaminants using oxidation. The reactive species of Openair Plasma breaks down hydrocarbon chains and breaks them down into smaller, volatile molecules (up to H2O and CO2).
Successful treatment can be verified, for example, by means of atomic force microscopy, which provides visual evidence of the change in the surface. A special scanning probe microscope is used here, which is used in surface chemistry for mechanical scanning of surfaces and for measuring atomic forces on the nanometer scale. Furthermore, the changed surface tension, e.g. by a drop of water, can be proven with the contact angle measurement. The water drop on a plasma-treated surface changes its wetting properties in such a way that contact angle and height are reduced, with a larger base and the same volume.
A similar process is used to remove copper oxides, especially in the production of semiconductors and LEDs. With X-ray photoelectron spectroscopy, the chemical composition of solids and their surface can be determined without any destruction. After the treatment of copper, the surface proportion of copper can therefore increase from 3% to 38%, with a concomitant reduction in the carbon content from 43% to 18%.
In addition to aluminium and copper substrates, nickel surfaces show similarly good characteristics after treatment with Openair-Plasma. This is particularly important in battery production. Since nickel oxide functions like a barrier layer, which makes it massively more difficult to combine with other materials, cleaning the nickel surface from oxides is indispensable. For this reason, a special nozzle was developed for this application, which meets the general requirements and at the same time meets the temperature requirements of the process step
Do you have questions regarding this matter?
Your contact person: Nico Coenenn
company: Plasmatreat GmbH