Wire Bond Mold Locking for IC Package Delamination

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Solution Overview

Problem

Integrated circuit packages face delamination issues due to the separation of mold compound from the die attach region, leading to electrical problems and variations in resistance, particularly in SOIC and PQFN packages using organic polymer-based adhesives or solder die attach.

Innovation Solution

The implementation of mechanical mold locking features, such as wire wedge bond loops or stud bumps, on the lead frame or PCB substrate to securely engage with the mold compound, preventing delamination by providing a mechanical locking surface that enhances adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional packaging without mechanical mold locking features is used, then the device structure is simpler and easier to manufacture, but delamination occurs between the mold compound and the die attach region leading to electrical problems and reliability issues

Engineering Contradiction:

Improveadhesion between mold compound and lead frameVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Mechanical mold locking features such as wire wedge bond loops or stud bumps are formed on the lead frame or PCB substrate before the molding process. These features protrude above the surface and are positioned to engage with the mold compound during encapsulation, preventing delamination by establishing mechanical interlocking prior to final assembly

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The mechanical mold locking features act as intermediary structures between the lead frame/PCB substrate and the mold compound. These features provide a physical interface that mediates the bonding relationship, with the protruding structures engaging the mold compound to prevent separation while maintaining electrical connectivity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If mechanical mold locking features like wire wedge bond loops or stud bumps are added to prevent delamination, then adhesion and reliability are improved, but the manufacturing process and device structure become more complex

Engineering Contradiction:

Improveprevention of delaminationVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The mechanical mold locking features are integrated with existing lead frame structures or PCB substrate features. Wire wedge bond loops are formed using standard wire bonding processes, and stud bumps are created through conventional bumping techniques, merging the mold locking function with existing manufacturing capabilities rather than requiring entirely new processes

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mechanical mold locking features serve multiple functions: they provide structural support for wire bonding, create mechanical interlocking with the mold compound to prevent delamination, and maintain electrical connectivity. This multi-functionality reduces the need for separate components and processes

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9685351B2Wire bond mold lock method and structure

Publication Date: 2017.06.20 CHIP PACKAGING TECH LLC

AI summary

A method and apparatus are described for fabricating a microchip structure (70) which protects interior electrical integrated circuits and components (120) attached to a lead frame die flag (104) using a molding compound (124) that mechanically interlocks with one or more positive mold lock structures formed as dummy wire loops (114) or stud bumps (214) that are attached to the lead frame (100) and/or die flag (104).