Gear-Shaped Conductive Pillar for Encapsulant Delamination Resistance

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Solution Overview

Problem

Conductive pillars in semiconductor packaging face issues with encapsulant materials delaminating due to stress during thermal cycling or stress tests, leading to gaps between the encapsulant and the pillar.

Innovation Solution

A conductive pillar with a gear-shaped top surface and a manufacturing method using a photomask with a gear-shaped pattern to create protrusions and cavities on the lateral surfaces, increasing the interfacial area with insulating materials and altering the fracture instability propagation mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional cylindrical conductive pillar is used, then the manufacturing process is simple, but the encapsulant material delaminates from the pillar surface under thermal stress

Engineering Contradiction:

Improveadhesion between encapsulant material and conductive pillarVSAvoidcomplexity of conductive pillar geometry

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductive pillar employs a gear-shaped top surface with curved protrusions instead of a conventional cylindrical shape. The contour lines of each protrusion have smooth curves that bulge outward, creating a gear-like geometry that enhances adhesion through increased interfacial area and altered stress distribution, while maintaining manufacturability through standard photolithography processes

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The top surface of the conductive pillar is segmented into multiple protrusions distributed along the periphery, creating a gear-shaped pattern. This segmentation increases the interfacial area between the encapsulant material and the pillar surface, providing more bonding sites and improving overall adhesion under thermal cycling conditions

Inventive Principle:

Principle #1Segmentation

2Reliability

If the encapsulant material is applied to a conventional pillar, then the application process is simple, but gaps form between the encapsulant and pillar during stress testing

Engineering Contradiction:

Improveinterface integrity between encapsulant and conductive pillarVSAvoiddifficulty of forming gear-shaped pattern

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The mechanical process of forming the gear-shaped pattern is replaced by a photolithographic process. A photomask with the gear-shaped pattern is used to expose and develop the photoresist layer, which then defines the conductive pillar geometry through subsequent etching. This substitution enables precise gear-shaped pattern formation using standard semiconductor manufacturing techniques

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The gear-shaped pattern is first created on a photomask, which serves as a template or copy. This pattern is then transferred to the photoresist layer through optical exposure, and subsequently to the conductive pillar structure through etching. The copying process enables precise replication of the gear geometry without requiring complex direct machining

Inventive Principle:

Principle #26Copying

3Reliability

If a gear-shaped pattern is used in the photomask, then the adhesion is improved, but the photomask design and manufacturing becomes more complex

Engineering Contradiction:

Improveadhesion strength between insulating material and conductive pillarVSAvoidprecision of gear-shaped pattern formation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The photomask enables precise gear-shaped pattern formation through optical exposure rather than mechanical machining. The gear pattern with smooth curved contour lines is defined by the photomask design, which can be manufactured with high precision using standard photolithography equipment, ensuring accurate replication of the adhesion-enhancing geometry

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 gear-shaped conductive pillar design enhances the adhesion between the insulating material and the pillar, reducing the likelihood of delamination and improving the structural integrity under stress conditions.

Implementation Method 1

an opaque part which blocks the light

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

a transparent part which allows light to pass through

Methodology Applied

Scientific EffectLight transmission: Light

Implementation Method 3

increasing the interfacial area with insulating materials and altering the fracture instability propagation mode

Methodology Applied

Scientific EffectAdhesion enhancement through increased surface area: Adhesive

Data Source

PatentUS20250038144A1Conductive pillar in a semiconductor package and associated manufacturing method

Publication Date: 2025.01.30 CHENGDU MONOLITHIC POWER SYST

AI summary

The conductive pillar in a semiconductor package has a gear-shaped top surface. The gear-shaped top surface has a plurality of protrusions distributed on the periphery of the gear-shaped top surface. Contour lines of each of the plurality of protrusions includes a smooth curve that bulges towards the space outside the conductive pillar. The conductive pillar can be defined by the space traversed by the gear-shaped top surface as it moves a certain distance in a direction perpendicular to the gear-shaped top surface. The conductive pillar can effectively enhance the adhesion between lateral surfaces of the conductive pillar and insulating materials.