ESD Coatings for the Semiconductor Industry Minimizing the Risk of Electrical Charges in Manufacturing

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FAULHABER Drive Systems

ESD coatings on toolings in the semiconductor industry prevent voltages from building up and being suddenly discharged. Rhenoterm offers a new ESD coating that can be applied at low temperatures and removed from the toolings without leaving any residue if required.

The semiconductor industry is considered a growth market. In the production of electronic components and semiconductors, all major manufacturers worldwide use automatic placement machines, among other things. In automated production processes, these placement systems move PCBs, circuit boards and wafers at high cycle frequencies; PCBs and circuit boards are precisely fitted with electronic components. Electrostatic discharge (ESD) is a key challenge here. ESD can occur wherever electrical voltage is built up through friction.

In semiconductor production, such voltages must be avoided at all costs or dissipated in a controlled manner, as even very low voltages can damage sensitive components. Defective components impair the functionality of the end device and can result in costly recalls for manufacturers. It is therefore crucial to prevent voltage peaks.

Protection Concepts Against ESD in Production

Protection against ESD is generally achieved in two ways in production: by earthing and by ESD coatings. Earthing provides a defined discharge path for electrical charges. To do this, the entire assembly system is brought to a uniform potential and all conductive parts are earthed. ESD coatings complement this concept by making the surfaces of tools electrostatically dissipative and thus preventing the uncontrolled accumulation of static charges.

At the same time, they enable the controlled transport of electrical charge to earth - even on materials that are naturally insulating or poorly conductive. This prevents a rapid, damaging discharge, as the voltage can dissipate slowly and in a controlled manner. ESD coatings can also reduce so-called particle-related contamination: Electrostatically charged surfaces can attract more dust.

The functional coater Rhenotherm has developed a new ESD coating - especially for toolings of pick-and-place machines that pick up, move and process wafers and circuit boards. These toolings often work with negative pressure (vacuum toolings) in order to securely fix the sensitive wafers, for example during transportation through a placement system. The coating is applied automatically and without mechanical pre-treatment such as sandblasting, so that warping of thin components during the process is avoided.

The ESD coating must also have a low surface roughness or a smooth and even surface topography in order to guarantee the desired vacuum values. At the same time, tool components are often bonded. Temperature-sensitive adhesives are often used for this. Accordingly, the ESD coating must be cured at the lowest possible temperatures in order to avoid damaging the bond.

The new Rhenotherm coating is suitable for a wide variety of substrates and combines ESD protection with dry lubrication, sliding optimization and high abrasion resistance. It can also be adapted to specific requirements, for example in terms of mechanical resilience or adhesive compatibility.

Energy Savings Through Low Process Temperatures

Conventional ESD coatings are often applied in several layers and then cured at high temperatures. Polymer coatings are sometimes sintered at temperatures of up to 400 degrees (approx. 750 °F). However, such temperatures are not suitable for all components. Delicate and thin components can warp and bonded toolings are generally temperature-sensitive and cannot be heated to such high temperatures. The same applies to plastic substrates and components made of aluminum or alloys with aluminum.

The new ESD coating can be processed at significantly lower temperatures. This not only enables the coating of temperature-sensitive components, but also significantly reduces energy consumption in the coating process, which lowers operating costs and CO₂ emissions.

Coating of Complex Geometries

Tooling components often have complex or intricate geometries. The more complex the shape, the more demanding the coating process. In many cases, geometries have to be adapted to compensate for mechanical distortion. However, this can lead to increased part weight, lower process speeds and cycle losses. The new ESD coating, on the other hand, is applied in thinner layers and cross-linked at lower temperatures. As a result, even the finest drill holes remain functional and even delicate components can be coated without reworking.

Recoating and Sustainability

Another factor is sustainability: toolings are cost-intensive to manufacture, which is why reusing them makes economic and ecological sense. If an ESD value is no longer achieved after prolonged use or a component is damaged, it can simply be recoated and does not have to be disposed of.

The Rhenoterm coating can be gently removed using pulsed laser radiation (photon ablation) without damaging sensitive components. The component can then be recoated without any loss of quality, several times if necessary. The service life of the coating depends heavily on production intensity and cycle times. Many companies therefore keep critical components in stock as spare parts. While a part is being recoated, a spare part can be used. Re-coating takes place within a few working days.

With the option of recoating, these ESD coatings contribute to sustainable and resource-saving production processes. They combine process reliability, energy efficiency and environmental compatibility in electrostatically sensitive applications. (sb)

*Nadja Müller is a freelance copywriter.