Method of molding a carrier ring to leads
AssigneeMotorola, Inc.
InventorsJames H. Knapp, Keith E. Nelson
Life of this patent
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Abstract
Molding carrier structures to leads of existing semiconductor packages is accomplished by molding at temperatures which maintain approximately matched thermal expansion between an encapsulating material and leads of the semiconductor package. The matched thermal expansion is provided by molding at temperatures below that which is required for glass transition of the encapsulating material. Molding at such temperatures is facilitated by a molding assembly that has a molding pot with an irregular shaped bottom which fluidizes the encapsulating material at low temperatures. Molding at temperatures that essentially match thermal expansion between the package's leads and the encapsulating material prevents damaging the leads of the package.
Claims12
A method of molding a carrier ring to leads of a semiconductor package which comprises:
- providing an assembled semiconductor package having leads;
- providing molding assembly having at least one pot wherein the pot has an irregular shaped bottom, at least one cavity for receiving the semiconductor package, and at least one runner connecting the pot to the cavity;
- placing the semiconductor package into the cavity;
- heating the molding assembly to a temperature of approximately 125 degrees centigrade;
- placing an encapsulating material having a glass transition temperature above said temperature inside the molding pot;
- and
- expanding the encapsulating material and the leads at substantial equal rates by maintaining the encapsulation material at said temperate while fluidizing the encapsulating material and forming a molded carrier ring on the leads.
A method of attaching a carrier ring to a semiconductor package subsequent to assembly of the semiconductor package which comprises:
- providing an assembled semiconductor package having leads;
- provision a molding assembly having a molding pot wherein the molding pot has an irregular shaped bottom, and having a cavity for accepting the semiconductor package;
- provision an encapsulating marital;
- placing the semiconductor package into the cavity;
- heating the mold assembly to a temperature less than a glass transistor temperature for eh encapsulating material;
- inserting the encapsulate marital into the molding pot;
- and
- applying pressure to the encapsulating material to cause a shearing action of the encapsulating meager against the irregular bottom of the pot wherein the shearing action fluidizes the encapsulating material enabling the encapsulating material to flow into the cavity and form a molded carrier ring structure on the leads of the semiconductor package while maintaining the fluidized encapsulating material at the temperature for the purpose of expanding the encapsulating material and the leads at substantial equal rates.
A method of molding to semiconductor packages which comprises:
- providing a molding assembly having a molding pot with an irregular bottom, and having a molding cavity;
- providing an encapsulating material;
- maintaining the mold assembly at a temperature that is less than a temperature required for glass transistor of the encapsulating material;
- and
- fluidizing the encapsulating material causing it to flow into the molding cavity and maintaining the fluidized encapsulation material at the temperature of the purpose f substantial matching thermal expansion rates of leads of the semiconductor package and the encapsulating material while forming a molded carrier ring structure on the leads.
Dependencies are inferred from the claim text.