Honeoye Falls, N.Y. – A thick film deposition system is based on the concept of “direct writing.” Called the MicroPen, fluid materials are extruded from a tool`s tip onto a substrate, producing an image directly from computer-generated data without the use of hard tooling. In operation, an integral computer with pattern-design software designs a part and sends the data to the dispensing/plotting system. Keeping the “pen” assembly stationary while moving the writing surface permits the use of dispensing and high Z-axis control. Resistive ink flows through the pen`s orifice via a controlled, positive-pressure pump system so that a constant force is applied to the fluid regardless of viscosity.
The technique, developed by OhmCraft Inc., reportedly counters the difficulty of maintaining thickness uniformity of dispensed fluids (owing to substrate cambers) by actually riding or floating on the material emitted. Thus, lines can be drawn over previous lines or on fragile material while accurate patterns can be drawn uniformly on irregular or contoured surfaces. The pen tip also reportedly makes it practical to draw a line within a slot or groove to protect it from damage. Line thickness can be controlled so that its surface is even with adjacent surfaces. In this manner, MicroPen technology is said to be an alternative to screen printing of thick films in terms of integrity of line width, thickness and uniformity. The CAD-controlled system draws multiple layers without firing and with no intervening screen or phototool to be made. Line widths as narrow as 0.002″ and high edge smoothness may make the system preferred over screen printing for thick film microwave circuits as well as applying photoresist for thin film circuits. For further information, contact Walter M. Mathias at wmm@ ohmcraft.com.
Direct-writing technology as applied to making high-voltage, five-percent inked-to-value resistors.