Lead Frame Recesses and Notch Steps to Prevent Burr Formation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Lead frames with outer frames prone to burr formation when stored, leading to potential electric short-circuits due to burr contact with die pads and leads.

Innovation Solution

A lead frame design featuring recesses and notch step portions on the outer frame surfaces to reduce the occurrence of burrs, with recesses extending from the upper surface to the side surface and notch step portions from the lower surface to the side surface, minimizing contact with storage frame walls and preventing short-circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If the outer frame has long side surfaces for standard packaging, then the lead frame can be properly stored and handled, but the right-angled portions of the long side surfaces contact and rub inner walls of the frame stocker causing burrs to form

Engineering Contradiction:

Improveouter frame shapeVSAvoidburr formation

Core Design Contradiction:

ShapeVSObject-generated harmful factors

Solution Approach 1:

The patent applies curvature by forming rounded portions at the right-angled corners of the outer frame's long side surfaces. These rounded portions replace the sharp right angles that cause rubbing against the frame stocker walls, thereby preventing burr formation while maintaining the overall rectangular shape and functionality of the lead frame package.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If burrs form on the outer frame, then the structural integrity may be compromised, but more critically the burrs can contact die pads and leads causing electric short-circuits

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidburr contact with electronic components

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary anti-action by proactively preventing burr formation through the rounded portion design before any rubbing contact occurs. The rounded corners eliminate the mechanical condition that would generate burrs during storage and handling, thereby preemptively protecting the die pads and leads from burr-induced short circuits and maintaining electrical reliability.

Inventive Principle:

Principle #9Preliminary anti-action

3Manufacturing precision

If the outer frame maintains sharp right angles for precise manufacturing, then manufacturing precision is improved, but the sharp edges increase friction and burr formation during storage

Engineering Contradiction:

Improveframe corner precisionVSAvoidfriction-induced burrs

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent resolves this contradiction by applying localized curvature only at the corner portions of the outer frame, while maintaining precise manufacturing tolerances for the overall frame dimensions and critical features. The rounded corners specifically address the friction issue during storage without compromising the manufacturing precision of the functional elements.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10201917B2Lead frame

Publication Date: 2019.02.12 SHINKO ELECTRIC IND CO LTD

AI summary

A lead frame includes an outer frame. The outer frame includes: one surface; another surface that is opposite to the one surface; a side surface between the one surface and the other surface; a recess that is formed to extend from the one surface to the side surface; and a notch step portion that is formed to extend from the other surface to the side surface.