Finest Structures in Conductive Thin Layers

The Neuroelectronics working group at the Technical University of Munich (TUM) has a research focus on the development of µ-electrode-based biosensors with novel materials and manufacturing processes. In a laser producibility test, she tested the structure widths of demanding thin layers that can be achieved in practice - with astonishing results.

The strength of the LPKF ProtoLaser R4 with a green picosecond laser source is cold ablation. It can remove layers from a carrier with precisely controllable energy inputs without thermal impairments occurring. This made the system an interesting candidate for the neuroelectronics group. They provided two materials: 100 nm gold deposit on 70 µm polyimide film and 100 nm platinum on 1 mm glass substrate. 

LPKF ProtoLaser R4: Ultra-short laser pulses  
for research and development

New materials are the basis for promising innovations, but they require sophisticated and flexible tools. LPKF ProtoLaser R4 stands for micro material processing with the lowest possible heat input in thermally sensitive materials. 

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The layout of the test pattern 

The test sample with dimensions of 1.9 x 0.85 mm has four markings of four squares 40 x 40 µm with a spacing of 20 µm in the corners. The other square pads are 50 x 50 µm. Insulated pads are intended for drill testing. The rest is connected in pairs with lines and spaces of different thickness. Five groups each consist of six such pairs with varying distances. This specially designed pattern determines the minimum track width for laser processing, minimum gaps and repositionability . 

The results are promising: although polyimides have high absorption in the green laser range, the penetration depth of 12 - 13 µm in the base substrate was low. In this constellation, minimum conductor tracks of 8 µm and gaps of 13 µm were produced. 

In the case of the platinum/glass sample, the structures are even finer: Structures with a minimum width of 5 µm and gaps of 10 µm can be produced here. You can download the entire report free of charge from the Knowledge Center.


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