Small Package Thermal Pad With Corner-Straddling Pins
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Solution Overview
Problem
Small SON/QFN packages with 1 mm by 1 mm area struggle to handle power beyond 0.5 W due to the lack of a thermal pad, which is essential for dissipating heat effectively, especially for semiconductor chips with areas of 0.3 mm2 or more and varying edge aspect ratios.
Innovation Solution
The arrangement of six terminals is optimized to create space for a thermal pad by grouping them in sets along package edges or forming pairs that straddle corners, allowing for the integration of a metal pad that can handle at least 1 W of power by interdigitating mold locks and using half-etched metal portions for enhanced adhesion and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the package size is reduced to 1 mm by 1 mm, then the miniaturization requirement is satisfied, but the power handling capability deteriorates to below 0.5 W due to lack of thermal pad space
Solution Approach 1:
The package is segmented into distinct functional zones: signal terminals are positioned at the periphery while the central area is dedicated to the thermal pad. This spatial segmentation allows the thermal pad to occupy maximum central space for heat dissipation, while peripheral terminals maintain electrical connectivity, resolving the conflict between miniaturization and power handling.
Solution Approach 2:
The invention transitions from conventional 2D peripheral terminal arrangements to a 3D spatial optimization where the thermal pad extends vertically and horizontally in the package center. The thermal pad is positioned in the dimensionally optimal location (package center) rather than being constrained to peripheral 2D arrangements, enabling effective heat dissipation in the minimized 1x1 mm footprint.
2Ease of manufacture
If conventional rectangular leads with center-line mold locks are used, then manufacturing simplicity is maintained, but the chip pad space is eliminated forcing chip assembly on insulating adhesive layers
Solution Approach 1:
The lead geometry is changed from symmetric rectangular shapes to asymmetric configurations where signal leads have peripheral positioning with specific mold lock orientations. This asymmetry allows mold locks to be positioned away from the package center, creating space for the thermal pad while maintaining adequate anchoring. The asymmetric layout enables the thermal pad to occupy the central area without interference from lead structures.
Solution Approach 2:
Instead of placing mold locks at the center line of leads (conventional approach), the invention inverts the mold lock positioning to the peripheral edges of leads. This inversion creates central space for the thermal pad while maintaining manufacturing simplicity through standardized leadframe processes. The mold locks are repositioned from central to peripheral locations, fundamentally changing the spatial arrangement.
3Quantity of substance
If six terminals are arranged along package edges, then terminal count requirement is satisfied, but thermal pad integration becomes impossible without compromising adhesion
Solution Approach 1:
Different regions of the package are assigned different functional qualities: peripheral regions contain signal terminals with mold locks for mechanical anchoring, while the central region is dedicated to the thermal pad for heat dissipation. This local differentiation allows six terminals to be arranged along package edges without interfering with thermal pad integration, as each zone serves its specific function without compromising the other.
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 configuration enables effective heat spreading and thermal energy transfer to a heat sink, supporting power handling of 1 W or more while maintaining compatibility with existing design rules and assembly processes.
Implementation Method 1
a metal pad for dissipating thermal energy... which can handle at least 1 W of power by interdigitating mold locks and using half-etched metal portions for enhanced adhesion and heat dissipation
Implementation Method 2
using half-etched metal portions for enhanced adhesion and heat dissipation
Data Source
AI summary
A plastic package for high power has a pair of oblong metal pins exposed from a surface of the plastic, the pins straddling a corner of the package; each pin has a long axis, the long axes of the pair forming a non-orthogonal angle. Package further includes a chip assembly pad, acting as a thermal spreader and semiconductor chip.