An investigation of the effects of fabric and stencil on resolution and registration in the screen printed circuit board

Printed circuit boards are a major component of most modern electronic devices. There are currently two major processes by which circuit boards are imaged; dry film and screen printing. This study investigated the screen printed circuit board. The resolution and registration limits are primary concerns of the screen circuit printer. These two factors are greatly influenced by two screen components; fabric and stencil system. The effects that two fabrics and two stencil systems had on the resolution and registration capabilities of a screen circuit printing system were determined. A test target was printed on a circuit substrate by a screen printing press under production conditions. Data on registration variation and line resolution was collected and analyzed statistically to determine if fabric, stencil or an interaction of both had a significant effect. A strong interaction effect of fabric and stencil upon resolution was found to occur when stainless steel mesh was used with the two stencil systems. Stainless steel combined with indirect stencil yielded the best resolution, while steel with capillary direct stencil yielded the worst resolution. A combination of polyester monofilament fabric and either indirect or capillary direct stencil yielded resolution between the two values found with the steel fabric. Registration variability was found to be significantly affected by the factor FABRIC. Steel mesh produced less registration variability than polyester mesh. However, this registration variability of fabrics seems to be significantly related to the condition of the fabric – new or used. Conclusions of the study were that for best resolution and least registration variability, stainless steel fabric combined with indirect stencils should be used. The second choice would be dyed monofilament polyester combined with either indirect or capillary direct stencil systems. The combination of stainless steel and capillary direct stencil should be avoided. It should be noted that run length is a major consideration when choosing fabric/stencil combinations for circuit imaging. Further investigations of registration variability in stainless steel and polyester monofilament fabrics over numerous runs would also yield valuable information for the screen circuit printer