Exposed Shunt Resistor Package With Stepped Pads for Heat Dissipation

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Solution Overview

Problem

Current semiconductor packages face inefficiencies in heat dissipation from heat-generating devices like shunt resistors, leading to potential damage, and issues with solder flow causing functional or cosmetic defects during assembly.

Innovation Solution

The design includes a lead frame with pads separated by a gap, where a shunt resistor is exposed to the exterior, coupled to heat conductors for efficient heat dissipation, and uses stepped pads to prevent solder flow into critical areas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If heat-generating devices are enclosed within the package, then protection from environmental factors is improved, but heat dissipation deteriorates

Engineering Contradiction:

Improveprotection from environmental factorsVSAvoidheat dissipation

Core Design Contradiction:

Object-affected harmful factorsVSTemperature

Solution Approach 1:

The heat-generating device (shunt resistor) is extracted from the enclosed package structure and positioned to extend through the mold compound to an exterior surface. This allows the device to remain protected within the package while exposing critical surfaces for heat dissipation to the external environment, resolving the contradiction between protection and heat dissipation.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If solder is applied to connect components, then electrical connection is improved, but solder flow into critical areas causes defects

Engineering Contradiction:

Improveelectrical connectionVSAvoiddefect prevention

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The pad structure is segmented into multiple levels (stepped pads with different heights). This segmentation creates physical barriers that prevent solder from flowing into critical areas during assembly, while still allowing adequate solder to remain for reliable electrical connections. The multi-level structure selectively controls solder distribution.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stepped pad structure is designed in advance to counteract the harmful effect of solder flow before it occurs. By creating elevated barriers on the pads, the design preemptively prevents solder from reaching critical areas, eliminating the need for post-assembly defect correction.

Inventive Principle:

Principle #9Preliminary anti-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 configuration effectively dissipates heat from the package, preventing damage and reducing the occurrence of defects by exposing the shunt resistor and using stepped pads to manage solder flow.

Implementation Method 1

coupled to heat conductors for efficient heat dissipation

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11742265B2Exposed heat-generating devices

Publication Date: 2023.08.29 TEXAS INSTRUMENTS INC

AI summary

In some examples, a semiconductor package comprises a lead frame. The lead frame includes a first row of leads; a first pad coupled to the first row of leads; a second row of leads; and a second pad coupled to the second row of leads, the first and second pads separated by a gap. The semiconductor package includes a heat-generating device coupled to the first and second pads and exposed to an exterior of the semiconductor package.