Pre-encapsulated Lead Frames for Microelectronic Packages

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Solution Overview

Problem

Conventional microelectronic device packages face issues with lead finger shifting and co-planarity during handling and assembly, leading to potential short circuits and encapsulation failures, with adhesive tape solutions compromising reliability due to moisture absorption and thermal expansion mismatches.

Innovation Solution

Pre-encapsulated lead frames with an encapsulating compound that fixes and maintains the alignment of lead fingers, eliminating the need for adhesive tape by providing a stiffening effect and ensuring co-planarity, thereby reducing shifting and enhancing package reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If adhesive tape is used to secure lead fingers, then lead finger shifting is reduced, but reliability deteriorates due to moisture absorption and thermal expansion mismatches

Engineering Contradiction:

Improvelead finger alignment stabilityVSAvoidpackage reliability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent removes adhesive tape from the lead finger assembly process entirely. Instead, lead fingers are pre-positioned and secured within the mold cavity during the encapsulation process, eliminating the need for separate adhesive tape application and avoiding all associated reliability issues.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent combines the lead finger positioning function with the encapsulation process. The mold cavity serves dual purposes: it positions and secures the lead fingers while simultaneously providing the encapsulation structure, eliminating the need for separate adhesive tape steps.

Inventive Principle:

Principle #5Merging (Combining)

2Manufacturing precision

If adhesive tape is used to maintain co-planarity of lead fingers, then alignment is improved, but device complexity increases due to additional materials and processes

Engineering Contradiction:

Improvelead finger co-planarityVSAvoidassembly process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the lead finger positioning function with the encapsulation mold cavity. The mold cavity is designed to hold lead fingers in the correct co-planar positions during encapsulation, eliminating the need for separate adhesive tape application and reducing process complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mold cavity serves multiple functions: it positions lead fingers, maintains co-planarity, and provides encapsulation. This multi-functional approach eliminates the need for separate adhesive tape components and simplifies the overall manufacturing process.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Length of stationary object

If lead fingers are made longer to span the package, then electrical connection is improved, but stability deteriorates due to increased shifting susceptibility

Engineering Contradiction:

Improvelead finger lengthVSAvoidlead finger position stability

Core Design Contradiction:

Length of stationary objectVSStability of the object's composition

Solution Approach 1:

The patent positions and secures lead fingers in their final positions within the mold cavity before encapsulation occurs. This preliminary positioning prevents any shifting during subsequent handling and assembly operations, stabilizing long lead fingers that would otherwise be susceptible to movement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The encapsulating compound acts as an intermediary that fills spaces and secures lead fingers in position. Once cured, this compound provides mechanical support and prevents shifting of long lead fingers without requiring additional fastening mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 pre-encapsulated lead frames effectively prevent lead finger shifting and maintain co-planarity, improving the reliability and throughput of microelectronic device packaging by eliminating the risks of short circuits and encapsulation failures, while also reducing the need for adhesive tape, which can cause moisture absorption and thermal expansion issues.

Implementation Method 1

fixes and maintains the alignment of lead fingers, eliminating the need for adhesive tape by providing a stiffening effect and ensuring co-planarity

Methodology Applied

Scientific EffectStiffening effect:

Data Source

PatentUS11189548B2Pre-encapsulated lead frames for microelectronic device packages, and associated methods

Publication Date: 2021.11.30 MICRON TECHNOLOGY INC

AI summary

Pre-encapsulated lead frames suitable for use in microelectronic device packages are disclosed. Individual lead frames can include a set of multiple lead fingers arranged side by side with neighboring lead fingers spaced apart from each other by a corresponding gap. An encapsulating compound at least partially encapsulates the set of lead fingers without encapsulating a microelectronic device. The encapsulating compound can generally fill the plurality of gaps between two adjacent lead fingers.