The Best Positive Sensitized Prototyping Boards

Understanding Positive Sensitized Boards

Positive sensitized boards are designed for photo-etching processes. They come pre-coated with a light-sensitive emulsion that hardens when exposed to UV light through a positive transparency. This hardened resist protects the copper traces during the etching process. When selecting a board, consider the thickness of the copper layer, as thicker copper is more robust and easier to solder.

Key Features to Consider

• Board Material: Most boards are made of FR-4 fiberglass, offering good durability and electrical insulation. Cheaper alternatives like phenolic paper may be less durable.
• Emulsion Sensitivity: Higher quality emulsions offer better resolution and are more forgiving with exposure times.
• Copper Thickness: Common thicknesses are 1 oz and 2 oz copper. 1 oz is standard for most applications, while 2 oz provides more current-carrying capacity.
• Board Size and Availability: Ensure the board size suits your project needs and that the material is readily available in packs that match your project volume.

Preparing for Etching

Proper preparation is key to successful etching. Ensure your workspace is clean and free from dust, which can interfere with the photo-resist. Use a high-resolution transparency for your circuit layout and align it precisely. Expose the board to a UV light source for the recommended duration, typically specified by the manufacturer, to properly cure the emulsion.

Etching and Finishing

Once exposed, the board needs to be developed to remove the unhardened photo-resist, revealing the copper traces. Then, immerse the board in an etching solution (like ferric chloride or ammonium persulfate) to remove the exposed copper. Finally, clean the board thoroughly to remove any remaining resist and etchant, preparing it for drilling and soldering.