Topside Package Cooling via Laser-Exposed Conductive Clip

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Solution Overview

Problem

The existing methods for enhancing heat removal from integrated circuits, such as mechanical buffing and post-mold plating, are costly and limited by the need for post-mold plating capabilities, and they do not effectively expose conductive clips for top-side cooling without imperfections.

Innovation Solution

The method involves removing molding compound from the side of a package structure using laser ablation to expose a conductive clip, followed by depositing solder paste and reflowing it to create a top-side thermal path without mechanical buffing or post-mold plating, allowing for direct heat dissipation or connection to a heatsink.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If mechanical buffing is performed to expose the heat slug, then the heat slug becomes accessible for cooling, but imperfections are left on the surface making subsequent soldering difficult

Engineering Contradiction:

Improveaccessibility of heat slugVSAvoidsurface quality of heat slug

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent removes only the necessary portion of molding compound covering the heat slug through laser ablation, exposing the heat slug surface without mechanically buffing it. This extraction approach eliminates the source of surface imperfections while maintaining accessibility for heatsink attachment.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If post-mold plating is performed on the heat slug, then soldering capability is improved, but manufacturing cost and process complexity increase

Engineering Contradiction:

Improvesoldering capabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies plating to the heat slug during the lead frame fabrication process before molding, rather than performing post-mold plating. This preliminary action ensures the heat slug surface is properly prepared for soldering without requiring additional post-molding steps, reducing overall process complexity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent combines the plating operation with the lead frame manufacturing process, merging two separate operations (plating and molding) into one integrated workflow. This eliminates the need for post-mold plating capability and reduces manufacturing complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Temperature

If mechanical buffing and plating are used to expose the heat slug, then top-side cooling is enabled, but fabrication cost increases

Engineering Contradiction:

Improveheat dissipation capabilityVSAvoidfabrication cost

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical buffing with laser ablation to remove molding compound and expose the heat slug. Laser ablation is a more precise and cost-effective method that eliminates the need for costly mechanical grinding tools and subsequent plating operations, while still enabling effective top-side cooling.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Device complexity

If the assembly line has no post-mold plating capability, then manufacturing simplicity is maintained, but top-side cooling cannot be implemented with existing methods

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidcooling implementation capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent applies plating to the heat slug during lead frame fabrication before molding, rather than requiring post-mold plating capability. This preliminary action enables top-side cooling implementation on assembly lines without post-mold plating equipment, maintaining manufacturing simplicity while achieving cooling versatility.

Inventive Principle:

Principle #10Preliminary action

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 approach provides effective top-side cooling without the need for costly grinding tools or post-mold plating, enabling efficient heat dissipation from integrated circuits and allowing for the direct attachment of a heat sink, thereby enhancing thermal performance.

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

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

depositing solder paste on the exposed portion of the conductive clip, and reflowing the solder paste

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11742266B2Electronic device topside cooling

Publication Date: 2023.08.29 TEXAS INSTRUMENTS INC

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.