Print and sintering technology

Aerosol printer Aerosoljet CE 300 system (Optomec)

Aerosoljet printer for the deposition of filigree structures
© Fraunhofer IWS Dresden
Aerosoljet printer for the deposition of filigree structures

Aerosol printing is a novel printing technology for inks with integrated functionality and is most suitable for printing extremely thin and high resolution structures such as interconnects, contact pads, electrodes, or active functional elements (e.g. sensor elements). Minimum resolution is 10 µm. With this aerosol printer it is possible to rigidly and flexibly print without masks and in a contact-free manner on an area with a size of 300 mm x 300 mm. Due to CAD controlled data it is easy to analyze and optimize geometry variations or produce complex print images.

Advantages over ink-jet method are the opportunity of printing on uneven or bent substrates, the nearly complete material yield and a wider processing window for inks, which reduces the development work on new ink materials.


Printing method

The ink is nebulized or atomized via spray aeration or ultra-sonic and subsequently transferred into an aerosol. A carrier gas transports the aerosol through the printing head in which it is focused by a sheath gas and then lead to the substrate. The 1 – 5 µm large drops hit and moisten the substrate so that a coherent coat is formed, which is finally heat treated.


Characteristics of the aerosol jet printing system

  • line width: 10 - 150 µm
  • viscosity of inks: up to 1 Pa·s
  • print speed: up to 200 mm/s
  • distance substrate - head: 2 - 5 mm
  • substrate heater: up to 150 °C

Dispenser Dispense Mate D-583 (Smartec)

Dispenser printer for the deposition of PEDOT and silver contacts
© Fraunhofer IWS Dresden
Dispenser printer for the deposition of PEDOT and silver contacts

The dispenser technology is best-suited for printing highly viscous pastes. Pastes can include metals, ceramics, and polymers or even composites. Using this method, the paste is applied to the substrate through a needle without touching it. Both rigid and flexible substrates with a size of up to 300 mm x 300 mm can be printed. Compared to screen printing methods, dispenser printing works without masks, meaning the printing image can be adjusted a lot easier.

Dispenser printing is used for industrial application of adhesives or printing bus bars on crystalline photovoltaic cells.


Printing method

The paste is hauled from the cartridge to the printing head by pressure or volume control. Between cartridge and the head there is a mixing screw that shears and homogenizes the shear thinning paste before it leaves the fine needle. The paste is then printed onto the substrate. Finally the printed structure is heat treated to remove solvents and possibly, sinter particles.


Characteristics of the dispenser printing system

  • line width: 100 µm up to mm
  • viscosity of inks: up tp 100 Pa·s
  • print speed: up tp 500 mm/s

RTA oven Jetfirst 200 (Qualiflow Therm)

Infrared oven JIPELEC JetFirst 200
© Fraunhofer IWS Dresden
Infrared oven JIPELEC JetFirst 200

This infrared oven is particularly designed for flat substrates up to a size of 156 mm x 156 mm. Infrared heaters warm the substrate by direct heat transfer. Depending on the settings this can take place within seconds.

An infrared lamp system built into the hood of the oven, the automatically controlled temperature measuring and the control system enable to homogeneously heat the substrate over the programmed temperature range. A silicon carbide coated graphite substrate holder allows for the heat treating of insulators and semiconductors (e.g. while using ceramic substrates).

Often used applications are: rapid thermal oxidation or nitriding, baking and activating of layers for use in photovoltaics, oxide free sintering of different materials and crystallization.


Equipment

  • model: JIPELEC JetFirst 200 (Qualiflow Therm)
  • substrate sizes: up to 156 mm x 156 mm
  • temperature regime: room temperature to 1300 °C
  • temperature control: thermocouple or pyrometer
  • ramp rate: 1 K/s to 300 K/s
  • possible atmospheres in process chamber: air, nitrogen, argon, hydrogen in argon
  • vacuum process possible
  • entire oven can be controlled via the computer