Dispensing of Adhesives

Application Example for heatable Dispensers

Adhesives often have high viscosities. There are two ways to dispense them: the design of the microdispenser can be optimized for higher viscosities or the viscosity is reduced by heating. GeSiM microdispensers should not be heated to more than 120 °C, i.e., the viscosity of the liquid should not exceed 5 mPa·s at 120 °C.

Droplet velocity (blue) and diameter (red) vs. excitation voltage at 90 °C for UVO-114

Droplet velocity (blue) and diameter (red) vs. excitation voltage at 90 °C for UVO-114

The UV-curable adhesives OG169 and UVO-114 (Epoxy Technologies) could be dispensed (viscosities at room temperature: 82 mPas and 300 – 700 mPas, resp.) The left image depicts the dependence of droplet velocity and diameter on the excitation voltage for UVO-114; the inset of Fig. 1 shows a picture of a single droplet of adhesive in front of the dispenser nozzle.

The right side picture shows an array of single epoxy spots on glass, made by the Nano-Plotter. The spot size is about 200 µm and can be varied using different piezo settings. Although the viscosity of OG169 is much lower than that of UVO-114, it needs a higher temperature for dispensing.

Array of UVO-114 with a spot diameter of ~ 200 µm on a glass slide

Array of UVO-114 with a spot diameter of ~ 200 µm on a glass slide

A number of liquids (e.g. glycerol) were successfully tested. Inthe case of two-component epoxies, the individual components must be dispensed using two different microdispensers. Mixing and curing of the epoxy then takes place on the substrate, one example being 301-2 from Epoxy Technologies.