Semiconductor Package Singulation via Notched Leadframe Breaking

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Solution Overview

Problem

The existing leadframe-based memory card packaging process results in protruding supporting bars that can rust and complicate the fabrication process, necessitating a novel method to encapsulate these bars and simplify the singulation process.

Innovation Solution

A package process where a carrier with supporting bars having notches is encapsulated, and a tensile force is applied to break the bars at the notches within the encapsulant, eliminating the need for cutting tools and exposing only the distal ends of the supporting bar remnants on the outer surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If supporting bars are used to connect the carrying portion to the side rail, then the structural strength is improved, but the supporting bars protrude from the encapsulant outer surface causing rust and requiring additional processing

Engineering Contradiction:

Improvestructural strengthVSAvoidrust

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The harmful protruding portions of the supporting bars are removed through controlled breaking at the notches. The encapsulant is designed to cover only the functional portions of the supporting bars while allowing the excess to be broken off and removed, eliminating the rust-causing exposed metal surfaces.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Notches are pre-formed on the supporting bars before encapsulation. These notches serve as predetermined breaking points that allow the supporting bars to be cleanly broken at the correct location after encapsulation, ensuring that the functional portions remain protected while excess portions can be removed.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If cutting tools are used to separate the side rail from the leadframe, then the singulation process is completed, but the process complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvesingulation process efficiencyVSAvoidfabrication process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The supporting bars are segmented into functional portions (encapsulated) and non-functional portions (to be broken off). The notches create natural segmentation points that allow the side rail to be separated from the leadframe by breaking at these predetermined locations, eliminating the need for complex cutting operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The traditional mechanical cutting system is replaced with a breaking system. Instead of using cutting tools to separate the side rail, the process uses applied force to break the supporting bars at the pre-formed notches, simplifying the manufacturing equipment and process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If the encapsulant covers the entire supporting bar, then rust prevention is improved, but the supporting bar cannot be properly separated from the side rail

Engineering Contradiction:

Improverust preventionVSAvoidsingulation ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The encapsulant provides different coverage to different portions of the supporting bar. The functional portions near the carrying portion are fully encapsulated for rust prevention, while the portions near the side rail remain accessible for breaking and separation. This localized quality differentiation solves both the rust prevention and singulation ease requirements.

Inventive Principle:

Principle #3Local quality

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

This method simplifies the memory card packaging process by avoiding the use of cutting tools and reducing the complexity of the singulation process, while ensuring the supporting bars are fully encapsulated, thus preventing rust and improving efficiency.

Implementation Method 1

forming an encapsulant on the carrier to cover the chip and encapsulate an inner portion of each of the supporting bars and the notch located on the inner portion

Methodology Applied

Scientific EffectEncapsulation: Physical Containment

Implementation Method 2

applying a tensile force to the outer portion of each of the supporting bars to form a breaking point on the notch of each of the supporting bars

Methodology Applied

Scientific EffectStress concentration: Fracture Mechanics

Data Source

PatentUS8927343B2Package process

Publication Date: 2015.01.06 APTOS TECH

AI summary

A package structure and a package process are provided. The package structure comprises a carrier having a carrying portion and a plurality of supporting bar remnants disposed around and extending outward from the carrying portion, a chip mounted to the carrying portion, and an encapsulant disposed on the carrier and covering the chip, wherein the supporting bar remnants are encapsulated by the encapsulant, and each of the supporting bar remnants has a distal end shrank from an outer surface of the encapsulant. A package process for fabricating the package structure is also provided.