Molded Array Package with Exposed Tab for Thermal Management
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Solution Overview
Problem
Conventional chip scale packaging technologies, such as QFP, QFN, and DFN, face challenges in heat transfer capability for high power applications and limited mounting options for attaching packages to next levels of assembly like heat sinks and printed circuit boards.
Innovation Solution
The development of a molded array package with exposed tabs and through-holes, which allows for improved heat transfer and flexible attachment options using lead frames compatible with existing chip scale assembly platforms, enabling better thermal management and diverse mounting configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional QFP, QFN, or DFN packages are used, then the package size is minimized close to chip size, but heat transfer capability is poor for high power applications
Solution Approach 1:
The package structure is segmented into distinct functional zones: a large bottom surface area for thermal attachment to heat sinks, peripheral leads for electrical connection, and an exposed tab for mechanical mounting. This segmentation allows each area to optimize its function independently, resolving the contradiction between heat transfer and mounting versatility.
Solution Approach 2:
The invention utilizes the vertical dimension by exposing the tab on the top surface of the mold compound rather than confining all connections to the bottom plane. This dimensional change enables through-hole mounting and vertical heat path integration, simultaneously improving heat transfer capability and mounting flexibility without increasing footprint.
2Adaptability or versatility
If conventional QFP, QFN, or DFN packages are used, then chip scale packaging is achieved, but mounting options for attaching to heat sinks and PCBs are limited
Solution Approach 1:
The exposed tab serves multiple functions simultaneously: it provides mechanical support for mounting to PCBs and heat sinks, acts as a thermal conduction path, and enables through-hole attachment methods. This multi-functionality increases adaptability without proportionally increasing structural complexity.
Solution Approach 2:
The lead frame is nested within the mold compound, with the exposed tab emerging through the mold surface. This nested configuration allows the package to maintain a compact form factor while providing external mounting interfaces, balancing versatility with structural simplicity.
3Temperature
If conventional packages are used, then automated assembly is simplified, but heat transfer capability deteriorates
Solution Approach 1:
The tab is pre-formed as an integral part of the lead frame structure before packaging, with through-holes already positioned and sized for standard mounting operations. This preliminary preparation enables straightforward automated assembly while establishing optimized thermal pathways from the chip through the tab to external heat sinks.
Data Source
AI summary
In one embodiment, a method for forming a molded flat pack style package includes attaching electronic chips to an array lead frame, which includes a plurality of elongated flag portions with tab portions and a plurality of leads. The method further includes connecting the electronic chips to specific leads, and then molding the array lead frame while leaving portions of the leads exposed to form a molded array structure. The molded array structure is then separated to provide molded flat pack style packages having exposed leads for insertion mount and exposed tab portions. In an alternative embodiment, the separation step produces a no-lead configuration with exposed tab portions.