Development of a capillary coating technology with on-line detecting system and its application for silver conductive circuit patterning

Printing technology becomes much more important for circuitry manufacture due to the advantages of high throughput, and low equipment cost. Nowadays, photolithography, screen printing and inkjet printing are the most popular technologies for producing PCB; however, photolithography has disadvantage of low material utility, screen printing is restricted for its low resolution and inkjet printing has limitation of using low viscosity fluid. In this paper, a novel direct patterning technology, the capillary coating technology, has been developed to pattern silver ink with viscosity around 220cP. This is a viscosity that is too low for screen printing but too high for ink jet printing. Different sizes of capillary tubes (10 μm - 200 μm) were used to directly "write" the arbitrary patterns of circuits on glass and pattern width of 12 μm were achieved. In order to control circuit morphologies and its electricity properties, e.g. width (W), thickness (T) resistance (R) and resistivity (ρ), the operation parameters have been investigated in different coating conditions, such as head diameter (D), coating velocity (V), tip-to-substrate distance (G) and liquid pressure head (H). A resistivity about 8 ~ 12 μΩcm of patterned conducting circuits has obtained by suitable drying and sintering conditions.