Heatsink
A metal part that spreads the heat produced by a power device over a large surface and transfers it to the surroundings; its job is to lower the sink-to-ambient thermal resistance. While a small aluminium profile is around 8–15 °C/W, a finned profile with a large surface comes down to the order of 1–3 °C/W under the same conditions and noticeably lowers the junction temperature at the same loss.
The effectiveness of a heatsink depends on three things: total surface area, air flow and contact quality.
- Surface area: As the number of fins increases the area grows, but if the fins get too close to each other the air is choked in natural convection and the gain stops.
- Orientation: In fanless use the fins must be vertical; as hot air rises it draws cool air in from below. A profile mounted horizontally can lose close to half of its efficiency.
- Contact: Metal surfaces are rough on a microscopic scale; the air gaps left in between are insulating. Thermal interface material fills these gaps.
Leave at least a few centimetres of clearance around a driver placed inside a cabinet; in a closed, narrow volume the heatsink warms the air around it and loses its effect.
The product data of AXI DC drivers does not include heatsink information. You have to derive the heatsink requirement from your own loss budget according to the actual current and ambient temperature in your application.
The context in which this term is used: DC Motor Driver Selection Guide