Stepped Lead Frame for Side-by-Side Chip Packages

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Solution Overview

Problem

In semiconductor packaging, side-by-side disposition of chips with non-uniform sizes or thicknesses leads to unbalanced mold flow during injection molding, causing air bubbles and affecting package appearance and yield.

Innovation Solution

A lead frame package structure with chip carrying areas of different horizontal levels, achieved through a down set stamping process, ensuring balanced mold flow and accommodating chips of varying sizes while reducing the number of stamping processes to enhance coplanarity control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If chips of different sizes are disposed side-by-side on a standard lead frame, then the package can accommodate non-uniform chips, but the mold flow becomes unbalanced during injection molding causing air bubbles and affecting package quality

Engineering Contradiction:

ImproveAbility to accommodate chips of different sizesVSAvoidMold flow balance during injection molding

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The lead frame is designed with chip carrying areas having different horizontal levels corresponding to different chip sizes. Each chip carrying area is locally adapted to its specific chip, creating a stepped configuration that maintains uniform mold cavity height throughout the package, thereby balancing mold flow during injection molding while accommodating non-uniform chips

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention transitions from a two-dimensional flat lead frame to a three-dimensional stepped structure by creating different horizontal levels for chip carrying areas. This dimensional change allows the lead frame to accommodate chips of varying sizes while maintaining a uniform top surface for mold closure, resolving the mold flow balance issue

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If multiple down set stamping processes are performed to create different horizontal levels for chip carrying areas, then chips of different sizes can be accommodated, but the manufacturing complexity increases and coplanarity control becomes difficult

Engineering Contradiction:

ImproveAbility to accommodate chips of different sizesVSAvoidNumber of stamping processes required

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple stamping operations that would traditionally be performed separately to create different horizontal levels are merged into a single down set stamping process. The stamping die is designed with multiple levels that can simultaneously create the stepped configuration for different chip carrying areas in one operation, reducing manufacturing complexity and improving coplanarity control

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8299587B2Lead frame package structure for side-by-side disposed chips

Publication Date: 2012.10.30 POWERTECH TECHNOLOGY INC

AI summary

A lead frame package structure for side-by-side disposed chips including a lead frame, at least two chips, and a package material. The lead frame includes a plurality of inner leads; a plurality of outer leads; and at least two chip carrying areas having different horizontal levels. The chips are of different sizes and are respectively disposed on the chip carrying areas. The package material encapsulate the inner leads, the chip carrying areas and the chips, wherein the outer leads exposed out of the package material extend from the inner leads and have different horizontal levels.