Lead Frame Sealing Structure for Solder Thickness and Heat Dissipation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional semiconductor devices face challenges in ensuring reliable electrical connections, thermal management, and efficient size reduction while maintaining structural integrity and ease of inspection, particularly due to variations in solder layer thickness and stress concentration.

Innovation Solution

A semiconductor device design featuring a lead frame with a concave portion and a convex portion, where the solder layer is placed within the concave portion, allowing for increased thickness and uniformity, and the sealing resin covers the lower surface of the lead frame except for the convex portion, enhancing thermal dissipation and reducing stress concentrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the solder layer thickness is increased to improve electrical reliability and reduce stress, then the device structure becomes more complex requiring concave portions in the lead frame

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidlead frame structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The lead frame is designed with concave portions at specific locations where solder layers are placed, creating local structural variations. This allows the solder layer to be thicker at these specific points to improve electrical reliability and stress distribution, while the rest of the lead frame maintains its original simple structure.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the sealing resin covers the entire lower surface of the lead frame to protect the device, then thermal dissipation efficiency decreases

Engineering Contradiction:

Improveprotection from environmental factorsVSAvoidheat dissipation efficiency

Core Design Contradiction:

Object-affected harmful factorsVSTemperature

Solution Approach 1:

The sealing resin is deliberately excluded from covering the convex portions of the lead frame, creating exposed regions. This extraction of resin coverage from specific areas allows heat to dissipate more efficiently through the metal lead frame to the external environment, while the rest of the device remains protected by the resin sealing.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If the solder layer thickness varies to accommodate manufacturing tolerances, then electrical connection reliability deteriorates

Engineering Contradiction:

Improvemanufacturing tolerance accommodationVSAvoidelectrical connection reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The concave portions in the lead frame are designed with sufficient depth to accommodate variations in solder layer thickness. This pre-designed structural cushioning ensures that even when solder thickness varies within manufacturing tolerances, the solder remains contained within the concave region, maintaining reliable electrical connections without defect formation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Device complexity

If the convex portion is completely covered by sealing resin to simplify the structure, then stress concentration increases causing defects

Engineering Contradiction:

Improvesealing resin structure simplicityVSAvoidresistance to stress-induced defects

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The sealing resin is selectively applied to cover only certain portions of the lead frame while deliberately leaving the convex portions exposed. This local differentiation allows the convex portions to serve as stress-relief features that prevent stress concentration and defect formation, while the resin-covered areas provide environmental protection and structural support.

Inventive Principle:

Principle #3Local quality

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 design improves electrical reliability, reduces stress-induced defects, facilitates easy inspection, and enhances thermal management by allowing for efficient heat dissipation and uniform resin distribution, thereby improving the overall performance and durability of the semiconductor device.

Implementation Method 1

a solder layer provided in the concave portion and fixing the semiconductor chip to the upper surface of the lead frame

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

a sealing resin for sealing the semiconductor chip and the lead frame

Methodology Applied

Scientific EffectSealing: Physical Containment

Data Source

PatentUS12469771B2Semiconductor device with sealing resin over chip and lead frame

Publication Date: 2025.11.11 FUJI ELECTRIC CO LTD

AI summary

Provided is a semiconductor device including: a lead frame having an upper surface provided with a concave portion and a lower surface provided with a convex portion; a semiconductor chip fixed to the upper surface of the lead frame; a solder layer provided in the concave portion and fixing the semiconductor chip to the upper surface of the lead frame; and a sealing resin for sealing the semiconductor chip and the lead frame. A thickness of the solder layer is larger than a depth of the concave portion. The sealing resin covers at least a part of the lower surface of the lead frame. At least a part of the convex portion of the lead frame is exposed from the sealing resin.