| 摘要 |
A molding apparatus having variable-volume cavities is provided. The apparatus consists of a lower and an upper mold defining a cavity for the lead frame, and having a conduit for forcing fluid plastic from a reservoir to the cavity for encapsulating an integrated circuit bonded to a lead frame. A pressure source is used to force the plastic from the reservoir through the conduit into both the upper and lower portions of the cavity surrounding the lead frame. The cavity of the mold is equipped with at least one piston-like insert slideably mounted in a bore hole in the surface of the cavity. The insert can be compressed or expanded to reduce or increase, respectively, the volume of the cavity. Thus, the final size of the cavity in the mold is determined by the position of the insert at the end of the encapsulation process. By allowing the expansion of the insert during a first phase of the molding operation, excess plastic is forced into the cavity. During a second phase, the volume of the cavity is reduced to its final size by the application of back pressure on the insert, causing the excess molten plastic to be forced out of the cavity together with residual air bubbles trapped in the plastic.
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