Compression/Transfer moulding

Compression moulding

Compression moulding is a technique mainly for thermoset moulding and is often used for moulding of glass fibre reinforced plastic. In the process the moulding compound is placed in the open mould cavity, the mould is closed and heat and pressure are applied until the material is cured. High hardness steel is normally used. For big moulds it is common to use prehardened material with high hardness inserts, in places where higher wear resistance is needed.

Mould material properties

Important properties are:

  • Wear resistance
  • Strength and hardness

Transfer moulding

Transfer moulding is a method of moulding thermosetting materials and is very common in production of electronic devices such as: integrated circuits, capacitors and diodes. In the process the plastic is softened by heat and pressure in a transfer chamber, then forced by high pressure through sprues, runners and gates into a closed mould for final curing. An important advantage with this method is the close dimensional tolerances possible to achieve.

Mould material properties

The resin, especially epoxy, tends to attack the mould and the part may stick in the mould during ejection. Often some type of surface treatment is needed. In order to avoid indentations the compressive strength should be high. Bigger inclusions in the mould material must be avoided, as it may give an imperfect surface. Because of the very strict tolerances of the part the mould inserts must have a very good dimensional stability during production.

The different components of an IC mould each have individual demands on the tool material. Each component requires steel with a suitable properties profile. The following properties are important:

  • Wear resistance
  • Compressive strength
  • Corrosion resistance
  • Cleanliness
  • Dimensional stability during use
Uddeholm - Tool Steel for Plastic Moulding

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