Useful information for good direct dispensing
An appropriate substance is provided at a defined height on a structurable substrate (foil). The substance height on the foil largely determines the amount of material transferred.
The transfer of the substance takes place via the adhesive force. Therefore this material property is of utmost importance.
When transferring the substance, the component must be pressed down to the foil. This guarantees a constant and defined substance transfer. In addition to wetting the component’s underside, wetting of side surfaces is also possible, which strongly depends on the surface tension and the level of the substance.
The component must be immersed and lifted out at defined speeds. For the repeatability of a defined substance transfer, it is important that these speeds are identical for each subsequent process. Constant holding times during wetting are also important for the process repeatability.
The component can be wetted in two ways.
Immersing the component in a even, unstructured substance. The component is wetted on its underside wherever the substance reaches the underside. This is usually used on structured components, such as components with protruding component pads, or on flat components that have to be completely wetted, such as wafer dice. The structuring of the substance takes place immediately before the component is lifted out.
The component is immersed in an already structured substance. The component is only wetted where the structured substance reaches the component. This variant is often used for unstructured flat components, for example to save adhesive on large areas or to specifically leave certain areas of the component unwetted.