Stencil printing today requires a higher degree of printer accuracy than ever before. Printer accuracy becomes increasingly difficult to maintain as demands for higher speeds and throughput test the limits of a printer’s capabilities, particularly with tiny apertures and tight land patterns. Today’s equipment design engineers are tasked with building machines with tighter performance tolerances and accuracy.
Printer accuracy must first be defined in terms of real and measurable printer parameters (such as machine alignment accuracy) and then verified. Different tools are used to verify printer accuracy; these include MCA, or Machine Capability Analysis, and PCA, or Process Capability Analysis, both of which are typically administered by independent 3rd party testing companies. Printer manufacturers may also have in-house accuracy checking tools designed for frequent use to maintain printing accuracy, as well as systems that communicate with an external Solder Paste Inspection (SPI) machine; such tools are designed to automatically correct registration errors based on closed-loop feedback from the SPI machine. This paper will discuss defining and verifying printing machine accuracy, and how said accuracy relates directly to SMT printing applications; and some machine design and engineering considerations that go into next-generation high-accuracy, robust printers for SMT fine-feature printing in volume.