When employing circuit board plotters for product development the main requirement is for fast, efficient and flexible operation. Consequently, the high costs incurred by the long waiting periods inherent when externally procuring circuit board prototypes, particularly those with RF substrates, can be avoided. The ProtoMat 95s/II meets these requirements, and all without chemicals, as it utilizes pure mechanical techniques to produce a circuit board on a copper-coated base plate. The data is provided by a CAD development system, with data formats in Gerber, Excellon, DXF or HPGL all suitable for use.

In operation a cushion of air is created that enables the cutting head to glide over the material during processing to avoid direct contact with the surface. Permanent sensing of the surface of the circuit board material being processed guarantees precise compliance with the specified cutting depth.

Drives for the X and Y directions consist of five-phase stepper motors combined with precision recirculating ball screws and linear guides. This layout enables the plotter to structure circuit boards with a resolution of 5 µm and associated repetition accuracy

This process is supported by the cutting tools developed by LPKF. The RF-cutters, shown in Figure 1 , produce a right-angled cutting edge that ensures optimal compliance with the layout geometry and the best possible match with the mathematical specifications. They are available in diameters from 0.15 mm (6 mil) to 0.40 mm (16 mil). To cut wider insulation tracks, endmills (shown in Figure 2 ) are used, which also cut right-angled edges and are available in diameters ranging from 0.8 mm (31 mil) to 3.0 mm (118 mil). A key feature facilitating high speed, precision circuit board plotting is automatic tool changing that utilizes a magazine carrying 30 tools. This is particularly advantageous for the production of small series boards.

The plotter is suitable for all single-sided and double-sided circuit board types (including RF and microwave materials) in the highest packing densities, and can be used for contour milling, front panel/label engraving and milling holes in aluminum front panels. In particular, the parameters of the machine, such as the rpm of the cutter or the advance and lowering speed (pneumatic lift), can be flexibly co-coordinated for the processing of standard RF and microwave substrates. A contactless depth- limiter (see Figure 3 ) is ideal for thin material as well as flexible circuits, ensuring that the sensitive copper layer is not damaged during the processing of RF substrates.

Typical fields of application include antenna technology, RF measuring and system technology, the development of linear power amplifiers and the realization of laboratory prototypes for the matching of circuit elements, and the power supply of RF high power transistors, shown in Figure 4 . These are some of the areas of development undertaken at the Fraunhofer Institute (see sidebar).

Conclusion

The ProtoMat 95s/II is particularly suitable for cost-intensive development projects due to the wide range of materials it can process, the wide combination of boards and surface substrates offered, and its ability to adapt to differing production specifications. Speed and flexibility are key features and although the machining time is dependent on track density, simple boards take just minutes while even complex multilayer boards only take a few hours.

LPKF Laser & Electronics, Garbsen, Germany Tel: + 49 (0)5131 7095-0; Fax: + 49 (0)5131 7095-90; e-mail: rp.sales@lpkf.de; Web site: www.lpkf.com. LPKF Laser & Electronics Inc., USA Tel: 1-800-345-5753; e-mail: sales@lpkfusa.com; Web site: www.lpkfusa.com. Circle No. 301