You may have noticed that I often include a paperclip (paper binder clip) in my breadboard prototypes. This paperclip serves as a simple heatsink for TO-220 components.
A few examples include this industrial relay driver:
Another is this TO-220 pass device in a current limiting regulator circuit used to charge hybrid Lithium-ion Capacitor (LiC).
The paper binder clip heatsink is far from ideal, but it does reduce the temperature considerably. When you move from prototype to final design you can switch to a proper heatsink for your through-hole and Surface Mount Devices (SMD).
Tech Tip: Be careful as the heatsink is electrically part of the circuit. To prevent contact with the transistor’s metal tab, you could use a thermal pad or a TO-220 “Full Pack” devices such as this list of NPN transistors.
Please forward this link to your friends, classmates, and colleagues. It’s a clever but not well-known solution that can save time prototyping circuits.