Guides / Materials
Choosing an Aluminum Alloy for Semiconductor Hardware
September 21, 2026
Aluminum carries most machined semiconductor hardware and most of the arguments about it come down to one question: will the part still be the shape you machined once it is unclamped, finished and installed.
The short version
| Alloy | Where it fits | Watch for |
|---|---|---|
| 6061-T6 | The default. Chamber parts, brackets, jig plates, handling hardware | Needs stress relief on thin or heavily pocketed parts |
| 6082 | Common alternative to 6061 where local stock favours it | Slightly different anodize appearance, similar behaviour |
| 5052 | Sheet metal, covers, light brackets | Not for tight machined features, poor in thick sections |
| 7075-T6 | Stiff, high load, wear parts | Does not weld, corrodes more, anodizes darker |
| Cast tooling plate | Flat jig plates and fixture bases | Higher price, not for welded assemblies |
Stress is the real material property
An aluminum plate holds internal stress from rolling or casting. Machining removes material unevenly, the remaining stress redistributes and the part moves. This is why a plate can measure flat in the machine and bow on the inspection table.
What controls it:
- Stress relieved plate, or a plate stress relieved by the shop before finish machining
- Roughing, a rest, then finish machining, rather than one continuous cut to size
- Balanced material removal, pocketing both faces where the design allows
- Light final cuts with the part clamped gently
None of this is exotic and all of it takes time. When a shop quotes a flat plate at a suspiciously low price, this sequence is usually what is missing. The cost side of that is in what drives the cost of a semiconductor test jig.
Anodize response by alloy
The coating quality depends on the alloy. 6061 and 5052 anodize evenly and light. 7075 and 2024 contain copper, which gives a darker coating, more variation and lower corrosion performance. If a drawing calls for a specific coating appearance or a coating that faces process chemistry, the alloy choice is part of that requirement, not a separate decision. See hard anodize or electropolish.
Purity and cleanliness grades
For parts that face plasma or aggressive chemistry, some buyers specify high purity aluminum with controlled inclusion levels and specific surface treatments. These are specialty products with their own supply chains and long lead times, and very few general machine shops stock them. If your application needs one, treat the material as a separately sourced, separately qualified item and say so in the RFQ, because a shop that has to find it after the order will quote a schedule it cannot hold.
What to write on the drawing
- Alloy and temper, plus the plate form if it matters, for example cast tooling plate
- Whether stress relief is required and at what point in the sequence
- Certificate required with the shipment, mill certificate at minimum
- Coating, thickness and masked features
- The flatness requirement with its datum scheme and whether it is free state
If you have a plate or chamber part and want it quoted by shops that stock the right form of aluminum rather than the nearest one, send the RFQ with the alloy and the flatness requirement in it.
Frequently asked questions
Why is 6061 used so much more than 7075?
6061 machines predictably, welds, anodizes cleanly and is stable once stress relieved. 7075 is stronger but it does not weld well, it costs more and it is more prone to corrosion. Most semiconductor hardware needs stability, not strength.
What is cast tooling plate and when is it worth it?
A cast and stress relieved plate sold flat and ready to machine, under names like Mic 6 and Alca. It moves less after machining than rolled plate, which is why it is common for jig plates and fixture bases. It costs more per kilo and buys you flatness.
Does the alloy affect anodize quality?
Yes. Copper bearing alloys such as 2024 and 7075 anodize to a darker, less uniform coating with lower corrosion resistance. 6061 and 5052 give a cleaner, more predictable result, which matters when the coating faces the process.
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Get matched with a supplierMore on materials
- ESD Requirements on Machined Semiconductor Hardware
- Hard Anodize or Electropolish: Choosing a Finish for Semiconductor Hardware
- Machining PEEK, Vespel and Torlon for Semiconductor Hardware
- Stainless and Nickel Alloys in Semiconductor Hardware
All guides and the sourcing glossary.