Topside Package Cooling via Laser-Exposed Conductive Clip
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Solution Overview
Problem
Existing methods for top-side cooling of electronic devices involve mechanical buffing and post-mold plating, which are costly and inefficient, and cannot be used in assembly lines without post-mold plating capability.
Innovation Solution
Exposing a conductive clip through a top-side opening of a molded package structure using laser ablation and depositing solder paste to create a thermal path without mechanical buffing or post-mold plating, allowing for top-side thermal conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical buffing is performed to expose the heat slug, then the heat slug becomes accessible for heatsink attachment, but the surface quality deteriorates with imperfections that complicate subsequent soldering
Solution Approach 1:
The patent replaces the mechanical buffing process with laser ablation to expose the heat slug. This substitution eliminates the surface imperfections caused by mechanical contact while achieving the same goal of making the heat slug accessible. The laser ablation process provides a non-contact, precision method for removing molding compound without compromising the underlying heat slug surface quality.
Solution Approach 2:
The patent changes the method parameter from mechanical removal to optical/thermal removal (laser ablation). This parameter change transforms the exposure process from one that damages the surface to one that preserves surface integrity, enabling direct soldering of heatsinks to the exposed heat slug without requiring additional plating steps.
2Reliability
If post-mold matte tin plating is performed after mechanical buffing, then solderability of the heat slug is improved, but the fabrication process complexity and cost increase
Solution Approach 1:
The patent extracts the plating step from the fabrication sequence by preventing oxidation during molding through inert gas atmosphere. This eliminates the need for subsequent plating operations, simplifying the process while maintaining solderability. The heat slug remains in its original metallic state but protected from oxidation, allowing direct soldering without additional coating steps.
Solution Approach 2:
The patent performs preliminary protection of the heat slug during the molding process itself by maintaining an inert gas atmosphere. This preliminary action prevents oxidation before it can occur, eliminating the need for later corrective plating steps. The protection is built into the molding process rather than added as a separate post-processing step.
3Temperature
If mechanical buffing and plating processes are used, then topside cooling capability is achieved, but fabrication costs increase and compatibility with assembly lines without post-mold plating is lost
Solution Approach 1:
The patent makes the molding process multi-functional by combining the encapsulation function with the heat slug exposure function. By controlling the inert gas atmosphere during molding, the same process that protects the device also exposes the heat slug in a solder-ready state. This eliminates the need for separate buffing and plating lines, making the process universally applicable to any standard molding assembly line.
Solution Approach 2:
The patent merges the heat slug exposure and protection functions into the molding process itself. Instead of separate sequential steps (molding, then buffing, then plating), the inert atmosphere control during molding simultaneously achieves encapsulation and prepares the heat slug for direct soldering. This consolidation reduces process steps and improves manufacturing efficiency.
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
Provides efficient top-side thermal conduction without the need for mechanical buffing or post-mold plating, reducing fabrication costs and enabling direct heat dissipation from the device.
Implementation Method 1
removing a portion of molding compound from a side of a package structure to create an opening that exposes a portion of a conductive clip, as well as depositing solder paste on the exposed portion of the conductive clip
Implementation Method 2
provides efficient top-side thermal conduction without the need for mechanical buffing or post-mold plating, reducing fabrication costs and enabling direct heat dissipation from the device
Data Source
AI summary
A method comprises removing a portion of molding compound from a side of a package structure by a laser ablation process to create an opening that exposes a portion of a conductive clip, depositing solder paste on the exposed portion of the conductive clip, and reflowing the solder paste. The laser ablation process in one example is a pulsed laser ablation process that includes raster scanning a laser along a portion of the side of the package structure to create the opening. Depositing the solder paste in one example includes performing a dispense process or a screening process that deposits solder paste in the opening onto the exposed portion of the conductive clip.