A method for local application of thin organic adhesive films on micropatterned structures

The application of adhesive films can be an important step in the manufacturing process of micromechanical structures if precise control of very small volumes of the adhesive over small contact areas is guaranteed. Residues of adhesives outside the joint area are to be avoided. Conventional microdispensers allow the handling of volumes down to about 1 nl. Recent developments employ techniques used in ink jet printers and are capable of delivering single drops of adhesive with volumes as low as 5 pl. Some micromechanical joints may require volumes even lower (an adhesive joint of 200 nm thickness over an area of 10 μm × 10 μm requires for instance a volume of 0.02 pl). The method developed for this purpose involves the deposition of a thin organic adhesive film by a spin coating process and the controlled transfer to (and only to) the intended locations on the micromechanical structure. One benefit of this method is increased design flexibility due to extension of the range of combinations of conventional thin film technology with other materials such as polymer films. The method was tested by preparing small cavities and other simple three-dimensional microstructures where it was mandatory to prevent the adhesive filling up the voids between the contact areas. Examples of composite structures made of 0.6 μm thick PET films glued to micropatterned structures on silicon substrates are presented.