Flow Properties and Correct Dosage of Adhesives in Micro-Applications

Adhesives used in micro-manufacturing processes must be applied in fine structures and minute quantities. Micro-manufacturing therefore presents a challenge regarding both the application techniques and the properties of the adhesives being used. Up until now users have had little choice but to test adhesives in direct applications. Apart from being highly complex, such testing delivers no transferable results. The key to resolving this problem lies in the rheology of adhesives. The ability to apply an adhesive is crucially influenced by its rheological properties - its flow behaviour. Relatively little research has been undertaken to date on the correlation between flow properties and adhesive application in the area of micro-manufacturing. Of the different techniques used for applying adhesives in micro-manufacturing, the research reported in this paper focuses on screen and stencil printing, although stamping and ink jet application are also of interest. Different adhesives, covering both filled and non-filled systems, were used in these studies. The application behaviour and evenness of deposits were evaluated. The flow behaviour of the adhesives was characterised in detail. In the case of screen and stencil printing it was ascertained that there is a relationship between the flow characteristics of the adhesives at low shear rates and the printed impression. Some of the research results concerning the correlation between the rheological properties of adhesives and their application behaviour are presented in this paper. The critical rheological value is indicated and characterised