Leadframe-Free QFN Package Layout for Direct Via Alignment
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Solution Overview
Problem
Conventional semiconductor packages with leadframes face limitations in constructing compact structures due to routing density issues and misalignment of vias, which affect manufacturing efficiency and reliability, particularly in QFN, DFN, and SON packages.
Innovation Solution
A leadframe-free QFN, DFN, or SON package design featuring conductive studs over an active layer, encapsulant layers, and dielectric layers with conformal interconnect structures, including LGA pads and flags, that allow for precise alignment and high-density connections without the need for capture pads, using unit-specific patterning and molded direct contact interconnect build-up layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional interconnect structures with alternating dielectric and conductive layers are used, then connectivity between layers is achieved, but manufacturing precision deteriorates due to via misalignment requiring capture pads
Solution Approach 1:
The invention removes the capture pad layer from the conventional interconnect structure, extracting the source of alignment complexity. By eliminating this intermediate layer, the structure achieves direct via-to-via alignment without requiring misalignment compensation features, thereby improving both manufacturing precision and reliability
Solution Approach 2:
The invention transitions from a multi-layer alternating dielectric-conductive structure to a simplified structure where conductive build-up layers are formed directly over molded encapsulant. This dimensional reorganization eliminates the need for via capture pads by changing the structural arrangement, allowing direct alignment between successive via layers
2Reliability
If conventional interconnect structures with capture pads are used, then via misalignment is corrected, but device complexity increases due to additional layers and routing constraints
Solution Approach 1:
The invention extracts and removes the capture pad layer from the interconnect structure, reducing the total number of layers. This elimination of unnecessary components simplifies the overall device complexity while maintaining reliable via alignment through direct build-up layer formation
Solution Approach 2:
The invention merges the functions of multiple separate layers into a more integrated structure. By forming conductive build-up layers directly over the encapsulant without intermediate dielectric layers, the design combines routing and interconnection functions into a streamlined architecture, reducing complexity
3Strength
If leadframes are used in conventional packages, then structural support is provided, but routing density is limited affecting compact structure construction
Solution Approach 1:
The invention extracts and removes the leadframe component from the package structure, replacing it with molded encapsulant that provides both structural support and routing functionality. This elimination of the leadframe enables higher routing density and more compact structure construction while maintaining necessary mechanical strength
Solution Approach 2:
The molded encapsulant serves multiple functions simultaneously: it provides structural support previously provided by the leadframe, enables high-density routing paths, and forms the substrate for conductive build-up layers. This multi-functional approach eliminates the need for separate leadframe components while achieving superior routing density
Data Source
AI summary
A QFN, DEN, SON, or LGA package without a leadframe, including a component comprising conductive studs disposed over a surface of the component, a single layer of encapsulant disposed around four side surfaces of the component and around at least a portion of the conductive studs, a layer of dielectric disposed over the single layer of encapsulant with via openings formed through the layer of dielectric, and a terminal conductive layer disposed over the layer of dielectric, the terminal conductive layer further comprising a lower surface that conformally follows contours of the layer of dielectric and the via openings, and the terminal conductive layer further comprises an upper surface having a flat surface, a slightly domed surface, a slightly concave surface or an upper surface that is flatter than the lower surface.