Which aluminum alloy is best for heatsinks?

Choosing the right aluminum alloy for heatsinks isn’t just about conductivity—it also affects manufacturing, cost, and surface finish.

6063-T5 is the most common alloy for heatsinks due to its excellent thermal conductivity, extrusion performance, and anodizing quality.

Other alloys like 6061 offer better strength, while 1xxx-series aluminum provides the best conductivity but lower strength. Let’s compare.

Which aluminum alloys can be used for heatsinks?

Aluminum heatsinks are mainly made from alloys in the 1xxx and 6xxx series. Here’s how they compare:

What to Consider

• Thermal Conductivity: 1xxx > 6063 > 6061
• Strength: 6061 > 6063 > 1xxx
• Extrudability: 6063 is the best
• Finish Quality: 6063 allows excellent anodizing

So in most situations, 6063 is the ideal balance. Only move to 6061 or custom alloys when strength or environment requires it.

What’s the difference between 6063-T5 and 6061 for heatsinks?

Both are common alloys, but they serve different roles.

6063-T5 has better thermal conductivity and surface finish, while 6061 provides higher mechanical strength.

Thermal Conductivity

• 6063-T5: ~200 W/m·K
• 6061-T6: ~150–170 W/m·K

That makes 6063 slightly better at conducting heat, which matters for performance.

Strength

• 6061 is stronger than 6063.
• It’s preferred when the heatsink must support loads, resist impact, or bolt tightly to structure.
• 6063 is still strong enough for many light-duty or indoor applications.

Extrusion Performance

• 6063 extrudes better.
• It supports finer fin shapes and more complex cross-sections.
• This matters when designing high-efficiency heatsinks with narrow fins or dense geometries.

Surface Finish

• 6063 delivers cleaner, smoother finishes.
• It’s better for anodizing—less color variation and better appearance.
• 6061 can be anodized but may show streaks or uneven tones.

Can we use custom aluminum grades for extrusion?

Yes—custom aluminum alloys can be developed or sourced to match specialized needs.

Custom alloys can improve conductivity, strength, or corrosion resistance—but they require testing and may increase cost.

When to Consider Custom Alloys

• You need higher thermal performance than 6063 allows.
• You need better corrosion resistance (e.g. marine environments).
• You want a balance of conductivity and high strength.
• You need specific surface finish properties (e.g. colored anodizing).

What to Watch Out For

• Custom alloys must still extrude well.
• The die design may need changes.
• Machining and post-treatment behavior may be different.
• They cost more, and have longer lead times.

For example, companies like HTS-ALU and Lori Thermal support custom alloy requests but often require minimum order quantities and validation steps.

Example Scenarios

If you’re interested in this, we can test a sample batch and validate its behavior before production.

Which alloy offers better thermal conductivity?

Conductivity is critical in heatsinks—but it’s not the only factor.

1xxx-series aluminum offers the highest conductivity, but 6063 is the best among practical extrusion alloys.

Thermal Conductivity Comparison

Pure aluminum has less resistance to heat flow, but it’s too soft for most structural heatsinks. That’s why we use 6063—it balances good conductivity and workability.

Factors Affecting Conductivity

• Alloy composition (magnesium, silicon, iron content)
• Grain size and direction
• Extrusion quality
• Age-hardening or temper
• Stress and machining

Even with the same alloy, conductivity can vary by 5–15% based on manufacturing.

Design Matters Too

Don’t rely only on conductivity numbers. A poorly designed 6061 heatsink with short fins may cool worse than a well-shaped 6063 part with taller, optimized fins.

Do different alloys affect CNC and surface treatments?

Yes—the choice of aluminum alloy changes how easy it is to machine or finish a heatsink.

6063 machines easier and gives a smoother anodized finish; 6061 is stronger but harder to cut and color.

CNC Machining

• 6063 is softer, easier to cut.
• 6061 is harder—more wear on tools, more effort.
• 6061 requires stronger clamps and deeper cuts.

Anodizing and Surface Finish

• 6063 anodizes beautifully—clear, even finish, good dyeing.
• 6061 can show streaks or uneven tones unless polished.
• Alloys with higher iron or copper may anodize poorly.

Other Surface Treatments

• Powder coating: both are compatible.
• Electrophoresis: works best with 6063.
• Hard anodizing: 6061 responds well to hardcoat, with higher durability.

Always test a small batch before committing large production.

Conclusion

For most heatsinks, 6063-T5 is the best choice—it combines thermal conductivity, easy extrusion, and a great finish. Use 6061 only when strength is a top priority, or consider custom alloys when you need special performance.