Exposed Pad IC Package Mold Lock via Trench Encapsulant

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Solution Overview

Problem

Integrated circuit packages face separation issues between the mold compound and the die pad due to differing thermal coefficients of expansion, leading to potential contamination and device failure during thermal cycling.

Innovation Solution

A die pad with a trench and openings is used, allowing the encapsulant to fill and form a ring that secures the die pad to the package body, preventing separation and maintaining planarity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the encapsulant and die pad are allowed to separate due to CTE differences, then the package can accommodate thermal cycling, but contaminants can enter along the separations causing device failure

Engineering Contradiction:

Improvethermal cycling accommodationVSAvoidpackage integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The die pad is segmented by forming a trench that divides it into regions, with openings created in the trench. This segmentation allows the encapsulant to flow through and lock into the structure, creating mechanical interlocking that prevents separation while accommodating thermal expansion differences between materials

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The encapsulant is nested within the trench structure and openings of the die pad, creating a interlocked configuration where the encapsulant material flows into and occupies the void spaces formed by the trench and openings, preventing delamination during thermal cycling

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If a trench with openings is formed in the die pad, then the encapsulant can lock to the die pad preventing separation, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvemold compound attachmentVSAvoiddie pad fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The trench and openings are formed in the die pad before the encapsulant is applied. This preliminary structuring of the die pad allows the encapsulant to be simply flowed or injected into the pre-formed features, avoiding the need for complex post-assembly operations while ensuring reliable mechanical interlocking

Inventive Principle:

Principle #10Preliminary action

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 solution effectively locks the die pad to the package body, preventing separation and ensuring the integrity of the package during thermal cycling and exposure to contaminants.

Implementation Method 1

the encapsulant can fill and form a ring that secures the die pad to the package body

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS9362211B1Exposed pad integrated circuit package with mold lock

Publication Date: 2016.06.07 NXP USA INC

AI summary

An integrated circuit package has an exposed die pad with a trench and openings in the trench that are filled with encapsulant to form an encapsulant ring near the edges of the die pad. During assembly, the encapsulant passes through the openings and fills the trench to form the encapsulant ring. The ring helps to keep the die pad from separating from the encapsulant caused by thermal cycling. Air vents might be included in the die pad surface to allow air to escape from the trenches and the openings as they fill with encapsulant. Trenches from the openings to the die pad edge on the chip-side of the die pad might be included to increase adhesion of the encapsulant to the die pad.