Лако-красочные материалы — производство

Adhesives of various rheological properties are available for the usual deposition processes: screen printing, pin transfer, and dispensing [7]. The adhesive droplet must have a definite height and size, which depend on the board design and the type of component, to bridge the distance between the surface of the circuit board and the electronical component. This can be achieved by a specific adjustment of the adhesive rheology, especially thixotropy and yield point. Usually, the adhesive is deposited on the board. If higher distances between board and device have to be bridged, an additional deposition of the adhesive on the underside of the component may be favorable to ensure wetting of both parts to bond and to counteract the drain-away of adhesive by gravitation. Some examples of distances between circuit board and various components are shown in Fig. 6. The usual diameter/height ratio of an adhesive droplet is about 10:1. Commercially available SMD adhesives may have ratios of up to 1:1 (Fig. 7).

Figure 7 Comparison of droplet heights