Leadframe Die Pad Planarization for Mold Flash Reduction
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Solution Overview
Problem
Mold-based packaging techniques for integrated circuit (IC) devices with exposed die pads face issues due to molding compound bleeding onto the die pad, reducing its heat dissipation capability, caused by burrs at the perimeter edge of the die pad during the molding process.
Innovation Solution
A leadframe with a die pad having tool markings of a series of peaks and valleys oriented parallel to the perimeter edge, which are embedded during a planarization process to flatten burrs and prevent molding compound bleeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the die pad is planarized by conventional stamping, then the manufacturing process is simple and fast, but burrs are formed at the perimeter edge causing molding compound to bleed onto the die pad
Solution Approach 1:
The die pad is planarized in advance before the molding process to remove burrs at the perimeter edge. This preliminary action prevents molding compound from bleeding onto the die pad during subsequent molding operations, eliminating the need for post-processing cleanup while maintaining manufacturing efficiency
Solution Approach 2:
The stamping process parameters are modified to include a planarization step that flattens the perimeter edge of the die pad. By changing the physical state and geometry of the edge through controlled deformation, burrs are eliminated and a smooth, flat surface is created that prevents compound intrusion
2Ease of manufacture
If the die pad perimeter edge is left as-is from stamping, then the manufacturing process is simple, but burrs cause molding compound to bleed and form mold flash on the exposed die pad
Solution Approach 1:
The die pad perimeter edge is planarized in advance before molding to remove burrs that would otherwise cause compound bleeding. This preliminary preparation prevents mold flash formation during the molding process while adding minimal complexity to the overall manufacturing workflow
Solution Approach 2:
The planarization process, which initially appears to add a step, actually converts the harmful effect of burrs into a beneficial smooth edge that prevents compound intrusion. The same stamping operation that creates burrs is modified to simultaneously flatten the edge, turning a defect into a protective feature
3Ease of manufacture
If burrs are not removed from the die pad perimeter edge, then the manufacturing process remains simple, but heat dissipation capability of the exposed die pad is reduced due to mold flash
Solution Approach 1:
The die pad edge is planarized in advance to eliminate burrs before the molding process. This ensures that the exposed die pad surface remains free of mold flash, maintaining optimal thermal contact with heat sinks or cooling structures and preserving heat dissipation efficiency
Data Source
AI summary
Embodiments of a method for preparing a leadframe for integrated circuit (IC) die packaging in a molded package with an exposed die pad are disclosed. In one embodiment, a method involves producing a leadframe with a die pad, wherein the die pad has a top surface, a bottom surface, and a perimeter edge. The die pad is then planarized to flatten burrs that may exist at the perimeter edge of the die pad, wherein planarizing the die pad comprises embedding tool markings in the die pad at the perimeter edge of the die pad, the tool markings including a series of peaks and valleys that run parallel to the perimeter edge at all locations around the perimeter edge. Embodiments of a leadframe for IC die packaging in a molded package are also disclosed.