Edge-Recessed Bond Pads for Stable Side-Wettable Packaging
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Solution Overview
Problem
Conventional side-wettable semiconductor packages face issues with structural stability and solder adhesion due to cutting processes that create burrs and loosen the lead frame or metal layer.
Innovation Solution
A side-wettable package with edge-recessed bond pads is developed, featuring a composite substrate, a die mounted in an accommodating space, a molding layer, an upper redistribution layer, and a solder mask that forms recessed surface bond pads with an anti-oxidation conductive layer for improved solder adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the lead frame or metal layer is cut to form indented portions for side-wettable structures, then solder adhesion is improved, but structural stability deteriorates due to loosening and burr formation
Solution Approach 1:
The package structure is segmented into distinct functional layers: the intact lead frame provides structural stability, while the upper redistribution layer is selectively patterned to form bond pads with side-wettable structures. This segmentation allows the cutting process to be applied only where needed (on the upper redistribution layer) without compromising the overall structural integrity of the lead frame.
Solution Approach 2:
The upper redistribution layer acts as an intermediary between the lead frame and the bond pads. It is mounted on the lead frame and can be independently processed to create side-wettable structures through cutting, while the lead frame itself remains intact and provides structural support. This intermediary layer isolates the cutting process from the lead frame, preventing loosening and burr formation on the structural component.
2Ease of manufacture
If cutting processes are used to create side-wettable structures, then solder creepage is enabled for AOI, but burrs are formed that affect solder adhesion
Solution Approach 1:
The patent replaces the conventional mechanical cutting process (which creates burrs) with a plating process to form the side-wettable structures. The upper redistribution layer is plated to create protruding portions that provide side-wettable surfaces for solder creepage, eliminating the need for cutting and the associated burr formation problem.
Solution Approach 2:
The invention changes the formation method parameter from mechanical cutting to electroplating. Instead of removing material through cutting, material is added through plating to create the side-wettable structures. This parameter change eliminates burr formation while maintaining the ability to provide solder creepage for AOI inspection.
Data Source
AI summary
A side-wettable package with edge-recessed bond pads has a composite substrate, and the composite substrate is covered with a molding layer. An upper redistribution layer is formed on the molding layer, and the upper redistribution layer is covered with a solder mask and part of the upper redistribution is exposed to form at least one surface bond pad. Surfaces of each surface bond pad are formed with an anti-oxidation conductive layer, wherein at least one side surface of each surface bond pad is recessed relative to side surfaces of the molding layer. The present invention does not form the side-wettable structure by cutting the upper redistribution layer to prolong service life of cutting Wheels and structural stability of the package. The anti-oxidation conductive layer increases a contacting area between solder and each surface bond pad, thereby facilitating AOI instruments to determine soldering condition of the package and another component.