A further analysis of liquid resin molding

Since the introduction of the first commercial equipment for encapsulating electronic devices in liquid thermosetting resin systems under pressure was announced a couple of years ago, interest in this approach has intensified. The process seemed to combine the best elements of transfer molding with the lower pressures and viscosities associated with liquid resins for what appeared to be a very economical and high speed means of encapsulating devices under less severe conditions than the transfer molding approach. Emphasis was placed on fast cycles, a more economic material, and less damage to the components being encapsulated due to the inherently lower molding pressures. The material being most highly touted at this time was an acrylic modified polyester resin capable of long storage times (several hours to several days) at room temperature but with a relatively short cure (several seconds to a few minutes) at the normal molding temperature of approximately 300°F.