Guides / Materials

Machining PEEK, Vespel and Torlon for Semiconductor Hardware

September 21, 2026

Engineering plastics carry the parts that must not conduct, must not mark a device and must survive test temperatures. They are also the materials where the shop’s process discipline shows up fastest, because the material moves.

What each one is for

PEEK. The general purpose choice. Good chemical resistance, useful up to around 250 C depending on grade, machines well, available in unfilled, glass filled and carbon filled forms, plus static dissipative grades.

Polyimide such as Vespel. Higher temperature, excellent wear and dimensional behaviour under load, low outgassing grades available. Expensive, and stock sizes are limited, so the design has to suit the available shapes.

Torlon and PAI grades. Very strong and stiff for a polymer, used for test sockets and load bearing insulators. Needs a proper cure schedule, and machined parts may need post machining conditioning.

Static dissipative grades of PEI and PEEK. Used where charge build up is the problem rather than heat. Covered in ESD materials and coatings.

Why plastic parts fail inspection

1. Stress in the blank. Extruded and moulded stock carries internal stress. Machine it away unevenly and the part warps overnight. Annealing before finish machining fixes it and takes a day.
2. Moisture. Several of these materials take up moisture from the air and change dimension with it. A part measured in an air conditioned metrology room and used in a hot test cell is two different sizes.
3. Heat from the cut. These are insulators, so cutting heat stays in the part. A tool that would be fine in aluminum melts or smears the surface.
4. Clamping. Plastic deflects under clamp pressure and springs back. Soft jaws, vacuum fixtures and light cuts are the difference between a flat part and a potato chip.

What to put on the drawing

• Grade and filler, exactly, including the supplier trade name if the application was qualified on it
• Whether annealing or conditioning is required and at what point
• The temperature and humidity that the dimensions apply at
• Edge condition and surface requirement, since burrs on an insulator are a particle source
• Cleaning and packing, because plastics pick up static and dust immediately

Cost behaves differently from metal

With metals, material is usually a small part of the price. With Vespel and Torlon the blank can be most of the price, which changes the whole optimisation: nesting parts into fewer blanks, using a smaller stock size, or splitting a part into two simpler pieces saves real money. Ask the shop what stock sizes it can buy before you finalise the geometry.

For sockets and change kit hardware, the same logic applies to the whole kit. That subject is covered in test handler change kits.

If you have plastic parts to quote and want them handled by shops that anneal and condition rather than cut straight from bar, send the RFQ with the grade and the dimensional condition stated.

Frequently asked questions

More on materials

• Choosing an Aluminum Alloy for Semiconductor Hardware
• ESD Requirements on Machined Semiconductor Hardware
• Hard Anodize or Electropolish: Choosing a Finish for Semiconductor Hardware
• Stainless and Nickel Alloys in Semiconductor Hardware

All guides and the sourcing glossary.