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US 5,328,870 AGranted
Method for forming plastic molded package with heat sink for integrated circuit devices
AssigneeAmkor Electronics, Inc.
InventorRobert C. Marrs
Life of this patent
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AssigneeAmkor Electronics, Inc.
InventorRobert C. Marrs
Estimating the term…
An improved integrated circuit package including a heat sink and an improved method for making the package is disclosed. The package incorporates an improved sealing (or locking) ring located circumferentially around the heat sink to provide a better seal between the encapsulant and heat sink and to reduce the possibility that contaminants from outside the package will reach the interior semiconductor die. A stress relief section is formed in the package leads and a dielectric adhesive material is used to attach the package leads to a heat sink surface. The dielectric adhesive creates a secure bond between leads and heat sink, allows heat transfer from the leads to the heat sink, and prevents shorting of the leads to the heat sink. An improved method for making the package involves creating a dimensional mismatch between the thickness of the heat sink and a corresponding dimension of the mold cavity so as to provide a tighter seal between a heat sink surface that will be exposed to the exterior of the finished package and the mold cavity during the encapsulation process to prevent encapsulant from forming on the exposed heat sink surface. Stresses in the leadframe created during encapsulation are mitigated by the stress relief section in the leads.
A method for encapsulating in encapsulant an assembly comprising a semiconductor die, an integrated circuit with a plurality of electrically conductive bond pads being formed on a first surface of the die, a heat sink, a second surface of the die being attached to a first surface of the heat sink, a plurality of electrically conductive leads, an inner end of each of the leads attached to the first surface of the heat sink with a dielectric adhesive material such that each lead extends outwardly form the heat sink, and a plurality of bond wires, each bond wire connecting one of the leads to one of the bond pads on the die, the method comprising the steps of:
A method for encapsulating in encapsulant an assembly comprising a semiconductor die, an integrated circuit with a plurality of electrically conductive bond pads being formed on a first surface of the die, a second surface of the die being attached to a first surface of a heat sink, a first surface of an adhesive dielectric material attached to the first surface of the heat sink such that a portion of the dielectric material extends beyond a periphery of the heat sink, a plurality of electrically conductive leads, an inner end of each of the leads attached to a second surface of the dielectric material such that each lead extends outwardly from the heat sink, a portion of the dielectric material extending beyond the inner end of each lead, and a plurality of bond wires, each bond wire connecting one of the leads to one of the bond pads on the die, the method comprising the steps of:
A method for forming a sealing ring on a heat sink, the heat sink having a first surface and a second surface opposite thereto, the method comprising the step of closing a cutting tool to a predetermined depth on one or both of the first and second surfaces of the heat sink at a predetermined distance from a periphery of the heat sink thereby to partially separate a portion of the heat sink material from the remainder of the heat sink material to form said sealing ring on an edge surface.
A method for forming a heat sink, the heat sink having a first planar surface and a second planar surface perpendicular to the first planar surface, the intersection of the first and second planar surfaces defining an edge, the heat sink being rounded or otherwise deformed at or near the location of the edge, the method comprising the step of shaping the heat sink at or near the location of the edge such that one or more planar shelf surfaces are formed between the first and second planar surfaces.
A method for forming a heat sink, the method comprising the step of forming a sealing feature in or on a heat sink surface such that the sealing feature has a cross-sectional shape, in a plane perpendicular to the heat sink surface, that has, at a first distance from the heat sink surface, a width that is smaller than the width at a second distance from the heat sink surface, the second distance being greater than the first distance.
Dependencies are inferred from the claim text.