Lead Frame Corner Rounding to Suppress Resin Cracks

Solution Overview

Problem

Conventional light emitting devices with integrally molded lead frames and resin suffer from crack generation during the dicing process due to stress concentration at the cutting plane, particularly when using thermosetting resin materials.

Innovation Solution

The solution involves rounding or chamfering the corner parts of the lead frames' cutting planes to reduce stress concentration and prevent cracks, ensuring that the cutting plane of the resin and lead frames are on the same plane, and using thermosetting resin for the package.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the cutting plane of lead frames and package are made to be on the same plane, then the device structure is simplified and manufacturing is easier, but cracks occur in the package during dicing due to stress concentration at the lead frame corners

Engineering Contradiction:

Improveease of manufactureVSAvoidreliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by modifying only the corner portions of the lead frames while keeping the rest of the structure unchanged. Specifically, the corner portions are rounded or chamfered to eliminate stress concentration points, allowing the package and lead frames to remain on the same plane for manufacturing simplicity while preventing cracks during dicing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs spheroidality by rounding the corner portions of the lead frames. This curvature eliminates the sharp angles that cause stress concentration during dicing, thereby preventing cracks in the package while maintaining the simplified structure where lead frames and package are on the same plane.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Strength

If thermosetting resin is used for the package, then mechanical strength and stability are improved, but cracks still occur during dicing due to stress concentration at lead frame cutting planes

Engineering Contradiction:

ImprovestrengthVSAvoidreliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies local quality by modifying only the corner portions of the lead frames while keeping the rest of the structure unchanged. Specifically, the corner portions are rounded or chamfered to eliminate stress concentration points, allowing the package and lead frames to remain on the same plane for manufacturing simplicity while preventing cracks during dicing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs spheroidality by rounding the corner portions of the lead frames. This curvature eliminates the sharp angles that cause stress concentration during dicing, thereby preventing cracks in the package while maintaining the simplified structure where lead frames and package are on the same plane.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS9537072B2Light emitting device, lead frame and resin cavity molding package

Publication Date: 2017.01.03 NICHIA CORP

AI summary

Pkg resin crack is suppressed after dicing.A light emitting device 1 where a light emitting device 2 that emits light is mounted on a lead frame 3 and that uses a resin cavity molding package 5 having an integrally molded lead frames 3, 4 constituting electrodes that correspond to the light emitting element 2 and resin, wherein roundness is given to a part or all of a cutting plane corner part of a retention section (hanger lead 3a, 4a) that become a cause of crack generation due to the retention sections (hanger leads 3a, 4a) of the lead frames giving stress concentration to resin at the time of cutting by a blade 7.