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What is Transfer Molding?

Alexis W.
Alexis W.

Transfer molding is defined as a process during which a specific weight of polymer is placed into a special chamber called a transfer pot. The transfer pot is preheated before the polymer is placed inside. A sprue is then used and the polymer is put through a preheated cavity or opening, so it may take the shape of this opening or mold. Finally, the polymer is cured when pressure and heat are applied to it, so it permanently takes the shape of the mold.

The transfer molding process makes creating integrated packaging for circuits, and various other molded pins for electronic components that require a high level of precision and care, much simpler. The transfer molding process can also be used for the creation of thermoplastics. The most common use for transfer molding processes is for the creation of thermosets.


The process of transfer molding is quite simple. It is very much like the process of compression molding, however, there is one major difference. Instead of the polymer substance being loaded into a mold that is open, the polymer is forced into a closed mold after being melted down.

The steps for the transfer molding process begin when the pre-heated and uncured molding material is placed into a transfer pot, which is located at the top of the closed mold. A plunger is then inserted with force to push the melted material down into the mold through a tiny opening at the bottom of the transfer pot called a sprue.

Once the polymer is pushed down past the sprue and into the cavity for the mold, the material is left to cure. After the curing process, the enclosed mold is then opened with the help of an ejector pin located at the bottom of the mold. Once the pin is removed, the mold can be opened. The finished piece is then removed from the mold and used for whatever it has been created for.

Transfer molds are used for a number of different purposes. Transfer molding is essential for the creation of products that contain various items including semiconductor chips and ceramics. Some of the materials used in the creation of these thermosets for the types of products mentioned above include epoxy, unsaturated polyester, Phenol-formaldehyde plastic and silicone rubber.

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