| 摘要 |
In molding integrated circuit packages voids are found in the molded plastic due to air entrapped in the charging container. It was discovered that entrapped air can be avoided if a portion of the preheated charge material has a higher viscosity than the remainder. Conveniently, this is achieved by preheating the preforms in a temperature gradient and charging the hottest preforms last into the container. The pressure causes the material at the top of the chamber to flow first, thereby expelling unwanted air through the runners ahead of the plastic flow. An effective implementation results from tilting the RF electrode in the preheating apparatus.
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