Plano-Convex Conductive Clip for Low-Voiding Semiconductor Packages
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Solution Overview
Problem
Molded packages with metal clips for semiconductor dies suffer from solder voiding due to large clip contact areas, which are difficult to avoid during reflow processes, increasing package costs.
Innovation Solution
A molded package design featuring an electrically conductive clip with a plano-convex shape, where the top side has an exposed flat surface and the bottom side has a convex curved surface, attached to the semiconductor die, allowing for a nonuniform thickness that maximizes heat dissipation and minimizes solder voiding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large clip contact area is used on the die topside, then effective electrical contact is achieved, but solder voiding increases
Solution Approach 1:
The clip is designed with non-uniform thickness, creating different surface qualities at different locations. The larger surface area at the die contact interface provides effective electrical contact, while the reduced thickness in certain regions minimizes the contact area that causes solder voiding during reflow processes
Solution Approach 2:
The clip thickness parameter is varied across its structure rather than being uniform. By changing the thickness parameter locally, the design achieves optimal electrical contact pressure while reducing the harmful contact area that leads to solder void formation during soldering
2Object-affected harmful factors
If a vacuum reflow process is used to reduce solder voiding, then solder voiding is minimized, but package cost increases
Solution Approach 1:
The design converts the potential harm of solder voiding into a benefit by using a clip geometry that inherently minimizes void formation through its non-uniform thickness profile. This allows standard reflow processes to achieve low voiding without requiring expensive vacuum equipment
Solution Approach 2:
The patent provides a cost-effective alternative to expensive vacuum reflow equipment by using a simply modified clip design that works with standard, more affordable reflow processes, making the solution economically attractive for mass production
3Temperature
If the clip has a nonuniform thickness with maximum at the vertex, then heat dissipation is enhanced, but manufacturing complexity increases
Solution Approach 1:
The clip features a curved or convex surface at its vertex region rather than a flat surface. This curvature naturally creates the non-uniform thickness profile with maximum thickness at the vertex, enhancing heat dissipation through increased surface area and improved thermal pathways while maintaining a relatively simple overall geometry
Data Source
AI summary
A molded package includes: a semiconductor die; a substrate attached to a bottom side of the semiconductor die; an electrically conductive clip attached to a top side of the semiconductor die; and a mold compound encapsulating the semiconductor die. A top side of the electrically conductive clip faces away from the semiconductor die and has an exposed flat surface that overlays the semiconductor die and is not covered by the mold compound. A bottom side of the electrically conductive clip faces the semiconductor die and has a convex curved surface that is attached to the top side of the semiconductor die. Along a vertical cross-section of the electrically conductive clip from the exposed flat surface to the convex curved surface, the electrically conductive clip has a plano-convex shape delimited by the exposed flat surface and the convex curved surface. A method of producing the molded package is also described.