Micro and nano structuring of carbon based materials for micro injection moulding and hot embossing Victor Usov, Graham Cross, Neal O Hara, Declan Scanlan, Sander Paulen, Chris de Ruijter, Daniel Vlasveld, Jan Edelmann, Bernd Gründig FaBiMed Workshop, EuSPEN 30 May 2016 Nottingham The work leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under Grant Agreement N 608901 Lead: Pablo Romero, AIMEN 1
Overview DLC as enabling material for mould fabrication Introduction to ion implant mask die forming technology Process development for fabrication of micro/nano features on mould Placing micro/nano features on industrial moulds Demonstration of replication by injection molding and hot embossing Conclusions 2
Diamond like carbon (DLC) material Amorphous, smooth Low cost relative to diamond 3
DLC mechanical applications Hard disk coating Steel razor blade coating 4
DLC as enabling material for mould fabrication The benefit of using DLC coating for moulding: Smooth conformal coatings from nm to tens of µm thickness Low surface energy Low polymer-tool adhesion and friction Inert and very resistant to wet chemistry Highly wear resistant Low thermal expansion and high elastic modulus Mature and optimized coating technology Multiple sources of DLC coatings available Strong adhesion to tooling steel 5
Molded PMMA using DLC coated Si mold : 18 th operation The research has shown that the ac:h coatings are robust, and advantageous in terms of reducing the inherent forces during demoulding. Further process optimisation is necessary Molded PMMA to widen the application area and using also to make possible the deposition of single and uncoated Si multiple features with a high mold : 3 rd degree of accuracy. operation 6
DLC as enabling material for mould fabrication These properties have an impact: Reducing de-moulding force (eg. 40% ABS) Improved feature quality and integrity Enhanced die lifetime and reusability Protection of the underlying machine metal features Potential for removal of polymer residue or build-up via wet chemistry without impacting feature size Potential for mould reuse: If the coating is used to a point where feature size is impacted, entire coating can be plasma or thermally removed and small features restored. Technical papers: Microinjection Moulding of Enchanced Thermoplastics, Monica Oliveira et al, Department of Mechanical Engineering, University of Aveiro, Portugal. Investigation of surface treatment effects in micro-injection-moulding, C.A.Griffiths et al, Int. J. Adv. Manuf. Technol., 47, (2009) A novel texturing of micro injection moulding tools by applying an amorphous hydrogenated carbon coating, C.A.Criffiths et al, Surf. Coating Tech., 235, (2013). 7
Patterning technology: Top surface mask G. L. W. Cross, et. al., Process and System for Fabrication of Patterns on a Surface, US 8,524,100 (2013), EU Nationalization (2015) 8
Diamond AFM Probes: Lateral resolution for pillars down to 5.0 nm 5 nm 9
Diamond AFM Probes: Lateral resolution for pillars down to 5.0 nm www.adama.tips 5 nm Tip Dimension 15nm x 125nm 10
Diamond AFM probes diamond probes Adama Super Sharp 2 nm tip radius Standard Si chip Diamond coated Si cantilever Diamond coated tip Single crystal apex Diamond atomic lattice fringes Super sharp diamond February 3-2016 Wafer scale diamond probe production 11 www.adama.tips
Diamond Flat Punch Probes: 12 2 um diameter; AR 1:1.5; Vertical side sides
Ion implant lithography and DLC coated moulds Steel Die or Mould Hard Coating Die or Mould Product Replication Hot Embossing Cold Forging Injection Moulding Nano-scale pattern by Ion Implant Patterning Technology Benefits : Smooth, featureless canvas No need for shims : Pattern integrated directly into mould Takes advantage of mould-protective coating feature 13
Patterning Technology Advantages Separation of patterning and material removal: Multi-scale technique: nm to 100 µm features over cm range areas E-beam comparable throughput Top-surface mask: Resistless Direct write on the mould: Patterns can be placed on non-planar surfaces of irregular shape High Performance Mask: High relief/aspect ratio small features can be produced Grey-scale: Placing patterns of different height on the same mould 5x5 mm Can be used in combination with conventional machining techniques such as mechanical milling and laser machining Complementary to steel die protective coatings 14
Technology development for replication in polymers Development of this technology was part of Fabrication of Medical Devices FaBiMed project Demonstrator medical devices with sub 10 µm features are to be fabricated by embossing/ injection moulding Pattern geometry and dimensions were inspired by medical microfluidic device specification (SensLab) Devices to be Fabricated : Microfluidics (POC diagnostics) Microneedles (Drug delivery) Materials : Glass, Polymer, Ceramics 15
Technology development 2.0 um high relief IM by Promold Width = 2.5 um Space = 1.5 um 6.0 and 7.0 um high relief IM by Promold 6.0 um high relief HE by Fraunhofer Full Channels coverage Solid square Width = 4 um Space = 7 um Width = 1.2 um Pitch = 4, 8, 12 um IM/HE moulds were machined by Fraunhofer and DLC coated by Adama (16)
Technology development Step 1. 0.5 µm relief DLC/Si(100) Step 2. 2.5 µm relief DLC/St. Steel 0.5 µm 3.2 µm 6.8 µm 1.7 µm 4 µm 2.5 µm Step 3. 8.0 µm relief DLC/St. Steel or Al Step 4. 9.0 µm relief DLC/St. Steel; AR 18:1 1.2 µm 8.8 µm 0.5 µm 17 8.0 µm
Technology development Step 1. 0.5 µm relief DLC/Si(100) Step 2. 2.5 µm relief DLC/St. Steel 0.5 µm 3.2 µm 6.8 µm 1.7 µm 4 µm 2.5 µm Step 3. 8.0 µm relief DLC/St. Steel or Al Step 4. 9.0 µm relief DLC/St. Steel; AR 18:1 0.5 µm 1.2 µm 8.8 µm 18 8.0 µm
Highlights of technology development Achieved height of relief of 9 µm for 0.5 micron sized features: AR 16:1 Straight edges and side walls, write fields of 200 x 200 µm Ga mask removal, smooth finish Throughput for FIB process 0.2 to 1.0 mm 2 /hour depending on the pattern complexity and desired relief Throughput can be improved by a factor of 4 by using higher FIB current and improvement to the design layout Good correlation between dimensions of masked and etched features for low relief For higher relief, increase in height of relief comes at the expense of lateral dimensions etched features are narrower than implanted due to erosion of mask sides: Process maps have been established 19
Placing micro/nano structures on a microfluidic mould C.A. Griffiths (U. Manchester) 80 nm pillar diameter 250 nm grating Complex mould shape: Small features of different height and scale placed in different areas on the same mould of irregular shape 4 mm 217nm 410 nm 78 nm 20
Small feature fabrication on DLC coated industrial moulds 3x3 mm 2 3x3 mm 2 1.0 um 1.0 um 10 um 3x0.5 mm 2 (21)
Replication by cold/warm forging Security/visual effect holograms on coins: Pore formation on epoxy coating: 100 nm 22
Replication by injection compression moulding Promold Arburg 25 ton injection molding machine IM by Promold on 250 µm thick lab-on-a-chip blanks Material: PPC- Polypropylene Random Copolymer (Moplen RP 7590) 9 µm relief Full replication of 32x32 µm features Partial replication of 9x9 µm features 23
Replication by hot embossing Reproducible hot embossing in 0.25 mm thick PC (Fraunhofer) 8 µm relief; full replication High vertical and side pattern fidelity Complete cavity filling Temperature 209 C, force 11.3 kn, time 480 s 24
Conclusions 1. DLC coatings are effective and helpful for IM and HE moulds 2. A new technology has been developed that demonstrates micro and nano-patterns fabrication into DLC coating directly on industrial silicon, steel and aluminium moulds 3. High quality replication by injection molding and hot embossing has been demonstrated 4. Higher stress cold/warm forging has also been demonstrated 5. Future work planned in order to evaluated the limits of this technology Limits of resolution Line edge roughness improvement Mould lifetime vs. feature size Throughout optimization 25