Heatsinks · Bonded Fin
Bonded fin heatsinks
Bonded fin heatsinks combine an extruded or machined base with thin stamped fins bonded or soldered into slots — achieving high fin aspect ratios that pure extrusion cannot reach, at a lower cost than skived for many volumes.
When to choose bonded
A bonded fin heatsink sits between extruded and skived: it reaches tall, thin fins via stamped aluminum inserts bonded (adhesive) or soldered into a base. Good for high surface area with moderate cost and no extrusion die limit on fin ratio. Solder bonding gives a stronger thermal joint than adhesive — we select based on power and temperature.
It is the pragmatic middle: more density than extrusion, lower cost than skiving at many volumes, and compatible with a complex or machined base that skiving cannot produce.
Typical specs
- Fin thickness: 0.2–0.8 mm
- Fin height: up to ~150 mm
- Join: adhesive or soldered
- Alloy: 6063 fins / 6061 base
Fin density set by stamping, not by die limits.
How a bonded fin heatsink is made
- Base preparation. An extruded or CNC-machined base is slotted to receive the fins; slot tolerance is controlled for insertion.
- Fin stamping. Thin aluminum fins are stamped to shape in high volume.
- Insert & join. Fins are placed into the slots and bonded with thermal adhesive or soldered for a stronger joint.
- Cure / reflow. Adhesive cures or solder reflows; the joint is inspected.
- Base machining & finish. Mounting face milled flat, then anodize or powder coat.
Capability & typical specs
Numbers below are typical; confirm exact limits against your drawing.
| Parameter | Typical capability |
|---|---|
| Fin aspect ratio | high (tall / thin) |
| Fin thickness | 0.2–0.8 mm |
| Fin height | up to ~150 mm |
| Base | extruded or CNC machined |
| Join method | bonded / soldered |
| Finish | anodized / powder coat |
Thermal & design notes
Design for bonded fins
- Specify joint type. Soldered for high temperature or power; adhesive for lighter loads and lower cost.
- Allow slot tolerances in the base for clean fin insertion and a consistent bond line.
- Match alloys. 6063 fins with a 6061 base is common; pick for conduction vs strength.
- Plan base machining. A complex machined base is where bonded construction beats skived.
- Consider the bond line. It adds a small thermal resistance versus skived — acceptable at the density and cost you gain.
Bonded vs skived vs extruded
| Need | Best choice |
|---|---|
| Tall fins, moderate cost, complex base | Bonded fin |
| Highest density, no bond line, compact | Skived fin |
| Low cost at volume, simple fins | Extruded |
Bonded fin is the flexible middle: stamping sets fin density freely, and the base can be machined into shapes skiving cannot make.
How to specify a bonded fin sink
Tell us the envelope, target thermal resistance (or power and ΔT), fin height and pitch, base geometry, joint type and finish. If you only have a thermal target, we propose the fin construction and base approach and return a DFM note before tooling.
Where bonded fin heatsinks are used
Power supplies
AC/DC and server PSU sinks needing tall fins in a standard envelope.
Industrial drives
Variable-frequency drives with moderate-to-high thermal load.
Medical
Equipment where a clean machined base matters.
EV & charging
Charge-point and onboard cooling modules.
Frequently asked questions
Bonded or soldered — which joint?
Soldered fins give a stronger, lower-resistance thermal joint and survive higher temperature and power; adhesive bonding is cheaper and fine for lighter loads. We choose with you based on operating temperature, power density and cost target. If the sink sees sustained high heat, specify soldered.
How dense can bonded fins be?
Fin thickness of 0.2–0.8 mm is typical, with height up to about 150 mm. Because fins are stamped, density is not limited by an extrusion die — you can specify a pitch the extrusion process could not hold. The practical limit is fin insertion, bond quality and airflow, not the die.
Why pick bonded over skived?
Bonded fin wins when the base is complex (machined features skiving cannot make) or when a slightly lower cost at volume matters. Skived still leads on pure density and fin-to-base conduction because it has no bond line. If you need the absolute thinnest, tallest fins in a simple slab, skived is usually better.
Which alloys for bonded construction?
6063 fins with a 6061 base is a common pairing — 6063 for the fin (good conduction and finish), 6061 for a stronger machined base. Pure 1060 fins maximize conduction but are soft. We match alloys to your thermal and mechanical needs.
What do you need to quote a bonded fin sink?
Envelope, thermal target (resistance or power/ΔT), fin height and pitch, base geometry, joint type and finish. A drawing gets the tightest quote; otherwise describe the load and we propose construction and price.
Quote a bonded fin heatsink
Send envelope and thermal load — we propose base + fin construction.