Inductive inline sintering of printed, wet conductor tracks in combination with a process control
Desired research results:
- TUC: Inductor (induction coil) for sintering wet, printed conductor tracks with thicknesses from 30 μm and widths from 300 μm
- IWU: model-based process control for the sintering process, max.conductivity deviation ± 5%
Source: Fraunhofer IWU, Chemnitz University of Technology
After the functional printing, e.g. with the jet dispense process, the still moist, printed conductor path (LB) must be cured in order to achieve the intended conductivity. This process step is currently being implemented globally in the furnace. This limits the size of the component, leads to holistic component heating and thus limits the choice of substrate. From a production and energy point of view, this process step is ineffective. In addition, local inline determination and adaptation of the conductivity is not possible. Local sintering processes known to date (e.g. laser, pulsed light, microwaves) either have high safety requirements and are associated with high investment costs (laser and microwaves) or can damage the substrate due to too large a focus point (pulsed light). The depth of penetration is also limited, since the laser and microwave radiation is absorbed in the edge areas of the printed LB. Due to the lack of a regulated, local inline sintering process, the reject rate for components with printed electronics is low. The manufacturing speed is still low and manufacturing costs are correspondingly high.
A sintering process must be established which can cure locally printed conductor tracks quickly, inexpensively, effectively. Inductive sintering is suitable because it is a contactless, energy-effective, locally acting process with a high penetration depth. It also ensures a short sintering time and minimizes substrate and conductor path damage. This enables high electrical conductivities of up to 80% of the excellent conductive solid Ag to be achieved. A process control keeps the process stable within a narrow target range. Taken as a whole, the approach leads to more cost-effective and productive manufacturing.
Benefits and economic importance for SMEs
With the research results, a selective inline-integrable sintering plant can also be manufactured and implemented by SMEs. There are new sales opportunities for SMEs along the value chain. The value chain is shown as an example:
Expected contribution to increasing the competitiveness of SMEs:
- Expansion of the fields of application and performance of MID assemblies
- New products and markets for paste manufacturers and plant manufacturers and their suppliers (e.g. Generators, inductor manufacturers)
- Reduction of production costs for users by reducing the reject rate (sintering process control and defect correction) and more energy-efficient (local) and time-saving (inline) post-treatment
- Expansion of the product portfolio of manufacturers of printed electronics
Expected industrial implementation of the R&D results after the end of the project:
- Automated production of functional elements for component functionalization for e.g. automotive engineering using additive printing processes.