Lead Frame Grooves Prevent Mold Flash

Solution Overview

Problem

In integrated circuit packaging, lead frames often develop round corners during the stamping and bending process, leading to poor attachment to packaging molds and resulting in mold flash, which reduces the exposed surface area and impairs heat dissipation.

Innovation Solution

A lead frame design featuring a crisscross interconnecting web portion with unit lead frames having grooves at the junctions of the die-attach and extension sections, preventing the formation of round corners and ensuring a secure attachment to the packaging mold.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the lead frame undergoes stamping and bending to position the die-attach portion and leads at different heights, then the electrical connection and structural configuration are improved, but round corners form at the junction of the die-attach portion and extensions, causing poor attachment to the packaging mold

Engineering Contradiction:

Improveelectrical connection configurationVSAvoidattachment precision to packaging mold

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by forming grooves at the junction of the die-attach portion and extensions before the stamping and bending processes. These pre-formed grooves serve as guides that prevent round corner formation during subsequent deformation, ensuring the die-attach portion maintains precise contact with the packaging mold surface throughout the manufacturing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies segmentation by dividing the junction area into distinct regions through the grooves. This segmentation creates clear boundaries between the die-attach portion and extensions, preventing material flow and round corner formation at the junction while maintaining the integrity of both sections during stamping and bending operations.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If round corners form at the junction of the die-attach portion and extensions, then the stamping and bending process is simplified, but gaps are left between the die-attach portion and the packaging mold, resulting in mold flash

Engineering Contradiction:

Improvestamping and bending processVSAvoidmold flash

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by forming grooves at the junction of the die-attach portion and extensions before the stamping and bending processes. These pre-formed grooves serve as guides that prevent round corner formation during subsequent deformation, ensuring the die-attach portion maintains precise contact with the packaging mold surface throughout the manufacturing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potential harm of material flow during stamping into a benefit by using the grooves to channel and control material deformation. The grooves guide the material flow in predetermined paths, preventing unwanted round corner formation and gaps that would lead to mold flash, while still allowing the stamping process to proceed efficiently.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If mold flash forms on the bottom surface of the die-attach portion, then the packaging process is completed, but the exposed surface area of the die-attach portion is reduced, worsening heat dissipation

Engineering Contradiction:

Improvepackaging process completionVSAvoidheat dissipation performance

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent applies preliminary action by forming grooves at the junction of the die-attach portion and extensions before the stamping and bending processes. These pre-formed grooves serve as guides that prevent round corner formation during subsequent deformation, ensuring the die-attach portion maintains precise contact with the packaging mold surface throughout the manufacturing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potential harm of material flow during stamping into a benefit by using the grooves to channel and control material deformation. The grooves guide the material flow in predetermined paths, preventing unwanted round corner formation and gaps that would lead to mold flash, while still allowing the stamping process to proceed efficiently.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS11495523B2Lead frame having a die pad with a plurality of grooves on an underside

Publication Date: 2022.11.08 CHANG WAH TECH

AI summary

A lead frame is made of conductive material, and includes an interconnecting web portion and a plurality of unit lead frames. Each unit lead frame includes a die pad and a plurality of leads. The die pad has a die-attach section disposed below an upper surface of the interconnecting web portion, and a plurality of extension sections bent at an angle from a periphery of the die-attach section and projecting to the interconnecting web portion. The die pad is formed with a plurality of grooves formed at an underside of junctions of the die-attach section and the extension sections. The leads extend from the interconnecting web portion toward and are spaced apart from the die pad.