A heat-sink drawing describes shape, but it does not always describe the cooling problem. A productive RFQ combines the mechanical drawing with thermal targets, airflow conditions and the downstream operations required to turn an extrusion into an installable component.
Define the thermal problem first
State the heat load in watts, the maximum allowed device or case temperature and the maximum ambient temperature. Identify the heat-source footprint and where it contacts the heat sink. If you have a required thermal resistance, explain the reference points and test conditions used to calculate it.
Clarify whether cooling is passive, fan assisted or liquid based. For air cooling, provide airflow direction, expected velocity or fan curve, available pressure and the installed orientation. Natural convection and forced airflow do not reward the same fin arrangement. Space around the heat sink, nearby obstructions and recirculation can matter as much as the outline dimensions.
Hydro’s heat-sink guidance distinguishes passive and active cooling and emphasizes matching fin geometry to the movement of air or liquid. It also notes the design flexibility available from aluminium extrusion.
Source: Hydro, Efficient Thermal Management with Aluminum Heat Sinks ↗
Decide whether extrusion fits the volume and geometry
An extruded profile is produced through a die, creating a continuous cross-section that is cut to length and then machined or finished. This route is often attractive when the same cross-section will be used repeatedly. Tooling cost, extrusion quantity, profile size and downstream machining all affect the business case.
Very tall, thin or closely spaced fins can be difficult to extrude consistently. A supplier will review fin ratio, minimum wall thickness, tongue strength, dimensional tolerances and the way metal flows through the die. Small changes to fin thickness, corner radii or base geometry may improve manufacturability without changing the thermal objective. Ask for a manufacturability review before freezing the production drawing.
Boyd describes extruded aluminium as a common, cost-effective and scalable heat-sink route, while also noting that profile and size limits must be considered. Its selection guide recommends defining convection mode, ambient temperature, dissipated power, maximum device temperature, heat-source footprint and available space.
Source: Boyd, Heat Sink Fabrications Guide ↗
Specify material and temper deliberately
Name the required aluminium alloy and temper, along with the governing standard. Do not select the alloy from conductivity alone. Extrudability, strength, machinability, corrosion performance, anodizing response and availability also influence the choice. If an alternative alloy is acceptable, ask the supplier to state the expected effect on thermal and mechanical performance.
The extrusion drawing should separate critical functional tolerances from general profile tolerances. Identify the base surface that contacts the thermal interface material, the permitted flatness, the datum system and the areas that will be machined after extrusion. If tight flatness is needed over a large base, define how and when it will be measured.
Describe every secondary operation
- Cut length and length tolerance
- CNC machining, drilled and tapped holes, slots and pockets
- Deburring and edge-break requirements
- Base milling or surface-flatness requirement
- Anodizing, conversion coating, painting or other finish
- Masked electrical-contact or thermal-contact areas
- Inserts, fasteners or other assembly work
- Cosmetic surface class and permitted handling marks
- Cleaning, packaging and protective-film requirements
Anodizing requirements should identify colour, finish class, thickness or governing specification where relevant. If the heat sink provides an electrical ground path, clearly mark surfaces that must remain conductive and confirm the treatment sequence.
Plan prototype verification
A first-article review should cover both dimensions and thermal use. Agree which dimensions are reported, how base flatness is checked and whether the finish is evaluated visually or by a measurable criterion. Prototype testing should use a realistic heat source, interface material, mounting load, orientation and airflow condition.
Thermal simulation can help compare concepts, but physical testing confirms the combined effect of extrusion variation, contact resistance, mounting and the installed environment. If the customer owns the thermal validation, make that division of responsibility clear in the quotation.
RFQ package
Send a 2D drawing and, when available, a 3D model. Include annual and batch quantities, prototype quantity, destination and target schedule. Add the thermal inputs, alloy and temper, finish, inspection plan and packaging requirement. Mark unresolved items as questions rather than allowing assumptions to become hidden specifications.
A complete heat-sink RFQ lets the supplier review thermal intent, extrusion feasibility and finishing scope together. That reduces late drawing changes and produces a quotation that reflects the finished component, not only a length of aluminium profile.