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Industry

Optical Module Heat Sinks Held to ±0.05 mm Fin Pitch

In an optical module the heat sink is a mechanical part with a thermal job. Fin pitch and fin position decide how much air reaches the surface; base flatness decides whether heat crosses into the sink at all. Both are dimensional problems, not thermal ones.

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Blue anodized aluminum section of the type supplied for optical module housings
Fin pitch
±0.05 mm
Base flatness
Agreed per part
Profile
±0.05 mm
Alloy
6063-T5
The challenge

Three numbers that decide a module heat sink

Thermal simulation gives you a fin geometry. Manufacturing decides whether you actually get it.

01

Fin pitch that has to repeat

Fins are formed in the die, but the die wears and the profile pulls. Without a controlled run and a measured first article, pitch drifts and the thermal model no longer matches the part.

±0.05 mm fin pitch
02

Base flatness for thermal contact

A base that is not flat traps an air gap under the module. The heat sink then performs like a much smaller one, and the failure shows up in the field, not on the bench.

Flatness agreed per part
03

Thin fins that must not fill short

A high fin-to-gap ratio is hard to fill. The die needs a feeder design matched to the fin geometry, or the tips come out rounded and short.

Feeder design at DFM
The answer

How we hold fin geometry through two processes

Extrusion forms the fins; machining makes the mounting face and the interface. Both are measured before shipment.

  1. Die designed around the fin ratio

    Long thin fins need a different feeder and bearing length than a plain box section. We design for the fin geometry you specify rather than adapting a stock die.

  2. Fins formed, not cut

    The fins come out of the die with the body, so there is no milling between fins and no burr to remove from a 0.05 mm gap. Machining is limited to the base, the mounting holes and the interface.

  3. First article measured on pitch and flatness

    Pitch and base flatness are measured on the first part and reported with the sample, so you can check the thermal assumption against a real number before production.

  4. Base machined for contact

    The mounting face is machined flat and, where the design calls for it, drilled and tapped for the module fixings from the same datum as the fin array.

Discuss Your Thermal Design Read the optical heat sink case
Typical parts

Parts we quote for optical programmes

Part families we quote for this industry. Client names are withheld; the process facts are ours.

  • Module heat sink ±0.05 mm pitch
  • Fine-fin profile 3–6 mm pitch
  • Shielded housing Machined cavity
  • Module carrier Flat base
  • Transceiver cover Thin wall
  • Mounting clip 6061-T6
Programs

Program in this industry

One published case where fin position through two processes was the whole problem.

Optical Module Heat Sink

Fin position held through extrusion and machining for a communications module programme.

Fin pitch ±0.05 mm

Read the case study

Integrated Heat-Sink Housing

Fins extruded with the housing body at controlled pitch, removing a separate heat sink.

Profile ±0.05 mm

Read the case study

Spec highlights — Optical Communication

  • Fin pitch held to ±0.05 mm through extrusion and machining
  • Profile cross-section ±0.05 mm, wall capability ±0.02 mm
  • Base machined flat; mounting holes from the same datum
  • Fin pitches from 3–6 mm, thin-fin sections on request
  • Alloy 6063-T5 for thermal sections
  • Die in 4–5 days, first sample about 7 days
Constraints

Where we stop

  • Thermal simulation or thermal resistance guarantees — we hold dimensions, not watts
  • Skived or bonded fin assemblies
  • Vapour chambers, heat pipes and other two-phase parts
  • Die-cast heat sinks — we can quote and manage them, but extruded fins are the route that removes the interface thermal resistance

We can tell you the geometry we can hold and measure it on a first article. Whether that geometry delivers the junction temperature your design needs is a thermal question, and it is answered by your simulation and your test, not by our inspection report.

FAQ

Optical heat sink questions

What thermal and mechanical engineers ask before a heat-sink tool is cut.

How is fin pitch measured?

On the finished part, at the root and at the tip, across the full fin array rather than at one point. The first article report shows the measured values so the drift is visible before a production lot exists.

Can you tell me the thermal resistance of a heat sink?

No. Thermal resistance depends on airflow, interface material and module power, and we do not publish a figure we cannot test. We hold the fin geometry and the base flatness; the thermal performance is verified on your bench.

What fin pitch can you extrude?

We hold fin pitch to ±0.05 mm and normally run 3–6 mm pitches, with finer arrays evaluated per section. Send the fin geometry and we will tell you whether the die can fill it before you commit.

Send the Fin Geometry. We Will Tell You If the Die Can Fill It.

Include the fin pitch, the base flatness that matters and the module power range. You get a DFM note on the section and a first article measured on pitch and flatness.

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What to send

  • 2D drawing or 3D model (STEP, IGES, DWG, DXF, PDF)
  • Alloy and temper
  • Surface finish and color
  • Estimated annual quantity