Leadframe-Free QFN Interconnect Structure for Dense Routing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor packaging technologies face limitations in constructing compact structures due to the use of capture pads and leadframes, which restrict routing density and result in exposed copper on the package periphery, leading to oxidation and difficulties in sidewall solder wetting.
Innovation Solution
The development of a quad flat no-lead (QFN), dual flat no-lead (DFN), or small-outline no-lead (SON) package without a leadframe, featuring conductive stumps over a semiconductor chip, a single-step encapsulant around the chip, and a solderable metal system (SMS) or organic solderability preservative (OSP) applied over conductive pads, eliminating the need for capture pads and exposed copper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional capture pads are used in interconnect structures, then manufacturing consistency is improved, but routing density is reduced and device compactness is limited
Solution Approach 1:
The patent removes capture pads from the interconnect structure entirely, replacing them with direct via-to-pad connections. This extraction of the unnecessary capture pad element increases routing density while maintaining manufacturing consistency through direct alignment features.
Solution Approach 2:
The patent introduces alignment marks and dimensional tolerancing in the planar direction to replace the vertical tolerance compensation function of capture pads. By shifting the tolerance management to a different dimensional approach (planar alignment vs. vertical capture), routing density is improved while manufacturing consistency is maintained.
2Strength
If leadframes are used in packaging, then structural support is provided, but exposed copper on the periphery leads to oxidation and soldering difficulties
Solution Approach 1:
The patent extracts and removes the leadframe component entirely, replacing it with a substrate-based support structure. This eliminates the exposed copper periphery that causes oxidation and soldering problems, while the substrate provides the necessary structural support through its mechanical properties and design.
Solution Approach 2:
The patent uses composite material structures in the substrate and encapsulant system to provide structural support without exposed copper. The combination of substrate materials and encapsulant creates a support structure that is both mechanically sound and resistant to oxidation, replacing the traditional leadframe function.
3Adaptability or versatility
If conventional interconnect structures with multiple layers are used, then connectivity is achieved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the functions of multiple interconnect layers into a simplified single-layer or reduced-layer structure. By combining connectivity functions and using direct via-to-pad connections, the patent achieves necessary connectivity while reducing structural complexity and manufacturing steps.
Solution Approach 2:
The patent creates a universal interconnect structure where the substrate and via system serve multiple functions simultaneously - providing structural support, electrical connectivity, and alignment reference. This multi-functionality reduces the need for separate specialized layers, simplifying the overall structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the creation of compact, high-density interconnects with improved thermal dissipation and reduced oxidation, allowing for better solder wetting and inspection, while eliminating the need for costly burr removal processes and enhancing the reliability of electrical connections.
Implementation Method 1
a solderable metal system (SMS) or organic solderability preservative (OSP) applied over conductive pads
Implementation Method 2
a first layer of encapsulant disposed in a single step around four side surfaces of the semiconductor chip, over the active surface of the semiconductor chip, and around the conductive stumps
Implementation Method 3
a first conductive layer and first vertical conductive contacts electrically coupled with the conductive stumps of the semiconductor chip
Data Source
AI summary
A method and related structure for a quad flat no-lead (QFN), dual flat no-lead (DFN) or small outline no-lead (SON) package without a leadframe. A semiconductor chip with conductive stumps over an active surface, a first layer of encapsulant disposed around the semiconductor chip, over the active surface, and around the conductive stumps, a first conductive layer and first vertical conductive contacts electrically coupled with the conductive stumps, the first conductive layer comprising conductive traces formed over a planarized surface of the encapsulant and conductive stumps, a second layer of encapsulant disposed over the first encapsulant layer, conductive layer, conductive traces, and first vertical conductive contacts, a plurality of conductive pads formed over a planarized surface, and a solderable metal system (SMS) formed or an organic solderability preservative (OSP) applied over at least a portion of the conductive pads.