The transfer molding method is a molding method of thermoset plastic resin. Although the compression molding method described last time is a typical molding method of thermoset plastic resin, the applied pressure may become non-uniform when the mold is closed and the pressure is applied, and as a result, it is possible that thin pins or some parts of the mold get deformed and damaged.

The transfer molding is a molding method that has been proposed as an improvement that corrects such weaknesses in the compression molding method.

The injection of the plastic to the interior of the mold is carried out by a plunger. Therefore, it is possible to inject the plastic to the interior of the mold with a relatively uniform pressure.

The molds for this method can be broadly classified into the following two types.

	1.	Hot type molds
	2.	Plunger type molds

The transfer molding method is used very frequently for molding the sealing of semiconductor MPUs, or for molding electronic components (device components).

Measures for preventing inclusion of gases or bubbles that are generated during molding and the balancing of the runners in multiple cavity molds are important factors of know-how in this method of molding.