Leadframe Downset Baffle Paddle Tie Bar Design

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Solution Overview

Problem

Conventional lead frames with downset baffle paddles experience shifting and twisting of leads during encapsulation, leading to inaccurate die attachment and wire-bonding difficulties due to bending of baffle paddle connections, resulting in reduced bonding strengths and peeling of chips.

Innovation Solution

A lead frame design with a baffle paddle downset configuration, where the internal tie bar has multiple windings to flexibly connect the baffle paddle to adjacent leads, reducing pulling stresses and maintaining leads in a single plane to prevent shifting and twisting, ensuring proper die-attaching and wire-bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the baffle paddle is adjusted to be downset in a different plane as the leads to balance mold flow, then the mold flow balance is improved, but the leads experience shifting and twisting causing inaccurate die attachment and wire-bonding difficulties

Engineering Contradiction:

Improvemold flow balanceVSAvoidbonding strength

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The tie bar is designed with a winding configuration that provides flexibility to absorb deformation forces. This flexible structure allows the tie bar to bend and accommodate the downset of the baffle paddle without transmitting excessive stress to the leads, thereby preventing lead shifting and twisting while maintaining bonding reliability

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The tie bar incorporates winding curves and rounded transitions instead of sharp angles. This curved geometry distributes stress more evenly during the downset formation process, reducing concentration points that would cause lead deformation and improving overall structural reliability

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Manufacturing precision

If the baffle paddle connections are bent to create downset, then the mold flow balance is improved, but the connected leads experience shifting displacement and twisting displacement

Engineering Contradiction:

Improvemold flow balanceVSAvoidlead planarity

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The flexible winding tie bar structure absorbs the deformation forces generated during downset formation, preventing these forces from being transmitted to the leads. This maintains the leads in their original planar configuration while still achieving the required baffle paddle downset for mold flow balance

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The winding tie bar acts as an intermediary element between the baffle paddle and the leads. It mediates the deformation process by absorbing the stress of downset formation, thereby protecting the leads from shifting and twisting while still enabling the baffle paddle to achieve its downset position

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If the tie bar is rigidly connected to the baffle paddle and leads, then the structural strength is improved, but the leads cannot accommodate the downset deformation without shifting and twisting

Engineering Contradiction:

Improvestructural strengthVSAvoiddeformation accommodation

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The tie bar transitions from a rigid structure to a dynamic, flexible structure with winding configurations. This allows the tie bar to adapt its shape during deformation processes, accommodating the downset of the baffle paddle while maintaining structural integrity and preventing lead displacement

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flexible winding design of the tie bar enables it to deform elastically during the downset process. This flexibility allows the structure to accommodate deformation without compromising strength, as the tie bar can bend and return to its original configuration, preventing permanent lead distortion

Inventive Principle:

Principle #30Flexible shells and thin films

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The design enhances die-attaching strengths and improves wire-bonding qualities by maintaining leads in a horizontal position, reducing peeling of chips and eliminating wire-bonding issues, while balancing mold flows during encapsulation.

Implementation Method 1

The internal tie bar is formed between the first plane and the second plane and has at least two or more windings to flexibly connect the baffle paddle to an adjacent one of the leads

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS7812430B2Leadframe and semiconductor package having downset baffle paddles

Publication Date: 2010.10.12 POWERTECH TECHNOLOGY INC

AI summary

A lead frame with downset baffle paddles and a semiconductor package utilizing the same are revealed. The lead frame primarily comprises a plurality of leads formed on a first plane, a baffle paddle formed on a second plane in parallel, and an internal tie bar formed between the first plane and the second plane. The internal tie bar has at least two or more windings such as “S” shaped to flexibly connect the baffle paddle to an adjacent one of the leads. Therefore, the internal tie bar can reduce the shifting and twisting of the connected lead during the formation of the downset of the baffle paddle.