Leadless Package Leadframe with Embedded Pins and Extended Die Pad

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Solution Overview

Problem

The heat dissipation efficiency of quad flat non-leaded (QFN) packages is limited by the small size of the die pad, which restricts the package's ability to manage heat effectively, especially for multi-function dies, and the pins are prone to damage and delamination issues during manufacturing.

Innovation Solution

A leadframe design with a die pad extending to the edges and pins featuring concave and convex parts, where the die pad and pins are embedded within openings and covered with a molding material to enhance heat dissipation and structural integrity, respectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the die pad size is increased to improve heat dissipation efficiency, then the heat dissipation efficiency is improved, but the package size increases

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidpackage size

Core Design Contradiction:

TemperatureVSArea of stationary object

Solution Approach 1:

The die pad extends in the vertical direction (thickness dimension) to increase heat dissipation area without significantly increasing the horizontal package footprint. This allows heat to be dissipated through the thickness of the package rather than requiring a larger planar area

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The pins are embedded within openings formed in the die pad, creating a nested structure where the pin structure is contained within the die pad volume. This allows the die pad to extend closer to the package edges while maintaining proper pin spacing and functionality

Inventive Principle:

Principle #7Nested doll (Nesting)

2Temperature

If the die pad extends closer to the surrounding pins, then the heat dissipation area is increased, but the manufacturing precision becomes more difficult to control

Engineering Contradiction:

Improveheat dissipation areaVSAvoiddistance control between die pad and pins

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The pins are positioned within openings formed in the die pad, creating a nested relationship where the pin locations are defined by the opening geometry rather than by external spacing constraints. This integrates the pin positioning and die pad boundary definition into a single manufacturing step

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The openings are pre-formed in the die pad structure before the pins are attached. This preliminary creation of the opening pattern establishes precise reference locations that guide subsequent pin placement, ensuring consistent spacing and positioning

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the pins are exposed without embedding, then the manufacturing process is simpler, but the pins are prone to damage and delamination

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidpin stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The molding material serves as an intermediary that fills the spaces around and between the pins, mechanically anchoring them to the die pad structure. This intermediary material prevents direct exposure of pin ends while maintaining manufacturing feasibility

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8105876B2Leadframe for leadless package, structure and manufacturing method using the same

Publication Date: 2012.01.31 CHIPMOS TECH INC

AI summary

A leadframe employed by a leadless package comprises a plurality of package units and an adhesive tape. Each of the package units has a die pad with a plurality of openings and a plurality of pins disposed in the plurality of openings. The adhesive tape is adhered to the surfaces of the plurality of package units and fixes the die pad and the plurality of pins.