CERES is a stand-alone microscale 3D print system from Exaddon, capable of printing complex and pure metal objects at the micrometer scale while offering sub-micrometer resolution.
Image Credit: Exaddon AG
This article explores the CERES print system’s capabilities with a focus on viable print materials, substrates, as well as the material properties of printed objects.
Viable Materials for Printing
Several materials are suitable for printing, with copper and gold currently offered as production ready "inks", with nickel next in line (though still in the development phase). Platinum and silver have also been explored by Exaddon. Aluminum, however, is not compatible with electroplating, and thus cannot be used with the CERES system.
Print materials are typically developed to meet research and industry demand - copper and gold have been developed first due to their critical role in electronic applications. In theory, if a metal can be electroplated, it can be 3D printed with the CERES technology.
Printing occurs by electrochemical deposition onto a substrate with a conductive surface. The substrate material does not have to be the same material as the printed objects – the inks used in the CERES system can be printed on different materials or carriers.
Some combinations offer more effective printing, however; for example, copper – copper, copper – gold, copper - ITO (a transparent conductive oxide) and copper - PEDOT (conductive polymer) are all possible. However, not all inks and substrates can be viably combined, as the electroplating process has the potential to dissolve some metals. For example, printing copper on aluminium is not possible - this would cause both the copper and aluminum to be reduced, causing them both to disappear.
However, printing on non-compatible substrates can be made possible by adding a very thin conductive layer (eg a 200 nm gold layer) onto a substrate surface. An example could be gold contact pads or conductive traces on a silicon wafer surface.
Material Properties of 3D Printed Objects
People may think that there are voids inside the printed material, as printing is a voxel-based process. However, it is actually a very dense material. Cross-section analyses of printed objects revealed a 99.5% density (or even greater) of pure copper metal. Testing of printed structures has shown the resistivity to be: ρcopper = 2.2E-8 Ω.m. This equates to around 75% of the conductivity of bulk copper.
The semiconductor industry frequently employs an electroplating process using high-quality copper – Exaddon's method can be understood in the same terms as this process, except for the production of 3D shapes.
The tensile strength and yield strength properties [please link to Testing Tensile Strength of Microscale AM Objects (azonano.com)] of Exaddon's 3D printed objects are in line with cold-drawn copper.
Utilizing 3D Printed Objects with Other Devices
Exaddon typically print parts exactly where they are needed, such as connectors on a chip – these are not intended to be removed from the substrate after printing. However, it is possible for printed objects to be removed if required, by using a polymer substrate.
One of Exaddon’s customers, a university in Japan, has worked with metal parts that had to be handled separately, which was achieved by printing onto a removable polymer foil (PEDOT).
This can be removed with a micromanipulator due to its elastic behavior being different to that of the printed metal part. This can be a somewhat complex process, but it enables Exaddon's 3D printed pure metal objects to be handled and used without any connection to a carrier.
Limitations of the CERES System
Like any technology, the CERES system has some limitations due to the processes involved. For example, it is not designed to print oxides. The system’s electrolytic bath is water-based, meaning that there is a small chance of oxides when printing certain metals other than copper or gold.
The print process relies on previously printed voxels being conductive in order to print the next one in line. Oxides are much less conductive, meaning that the CERES system cannot print these.
This information has been sourced, reviewed and adapted from materials provided by Exaddon AG.
For more information on this source, please visit Exaddon AG.