Silane Coating for Semiconductor Die Pillars

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Solution Overview

Problem

Conventional semiconductor die attach methods using solder materials often result in solder slumping or wicking, leading to undesirable intermetallic formation, bond weakness, and joint failure due to the reaction between solder and conductive elements, which is not adequately inhibited by existing barrier materials.

Innovation Solution

A coating formed from a silane material is applied to the conductive elements to isolate them from solder, preventing wicking and slumping, and enhancing adhesion with underfill materials, thereby reducing intermetallic formation and improving mechanical and environmental stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional barrier materials are used to prevent solder contact with conductive elements, then some protection is provided, but solder wicking and slumping still occur leading to intermetallic formation

Engineering Contradiction:

Improvejoint reliabilityVSAvoidsolder wicking and slumping

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A coating layer is introduced as an intermediary between the solder and the conductive element. This coating acts as a mediator that prevents direct contact and harmful reactions while allowing the solder to properly bond to the conductive element through controlled wetting and reflow processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution employs a composite structure consisting of multiple layers: the conductive element (e.g., copper), a barrier material layer, and an additional coating layer. This composite material approach combines the benefits of different materials to achieve both mechanical strength and protection against solder wicking and intermetallic formation.

Inventive Principle:

Principle #40Composite materials

2Strength

If solder material is used for die attach, then electrical and physical connection is achieved, but intermetallic formation and bond weakness occur due to solder slumping and wicking

Engineering Contradiction:

Improvebond strengthVSAvoidintermetallic formation

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The invention converts the potentially harmful effect of solder wicking into a beneficial outcome by controlling the wetting behavior. The coating is designed to allow controlled solder wetting for proper bonding while preventing excessive wicking that would lead to intermetallic formation and bond weakness.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The coating modifies the surface parameters of the conductive element, changing the wetting characteristics and surface energy to control solder behavior. This parameter change prevents solder slumping and wicking while maintaining adequate wetting for strong bonding.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional conductive elements are used without additional coating, then manufacturing is simpler, but solder contact leads to intermetallic formation and joint deterioration

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidintermetallic formation control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The coating is applied in advance to the conductive elements before the die attach process. This preliminary action prepares the surface to prevent intermetallic formation during subsequent soldering operations, ensuring consistent results without requiring complex in-process adjustments.

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 silane coating effectively inhibits solder contact with conductive materials, reducing the likelihood of intermetallic formation and joint failure, while enhancing the adhesion between components and underfill materials, thus improving the reliability and stability of semiconductor die assemblies.

Implementation Method 1

The coating isolates the conductive material from a solder material used to bond the conductive element

Methodology Applied

Scientific EffectPhysical isolation:

Implementation Method 2

The coating inhibits the solder material from coming into contact with the conductive material, such that the solder is inhibited from wicking or slumping

Methodology Applied

Scientific EffectSurface barrier effect:

Implementation Method 3

enhancing adhesion with underfill materials

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS9224715B2Methods of forming semiconductor die assemblies

Publication Date: 2015.12.29 MICRON TECHNOLOGY INC

AI summary

Semiconductor assemblies, structures, and methods of fabrication are disclosed. A coating is formed on an electrically conductive pillar. The coating, which may be formed from at least one of a silane material and an organic solderability protectant material, may bond to a conductive material of the electrically conductive pillar and, optionally, to other metallic materials of the electrically conductive pillar. The coating may also bond to substrate passivation material, if present, or to otherwise-exposed surfaces of a substrate and a bond pad. The coating may be selectively formed on the conductive material. Material may not be removed from the coating after formation thereof and before reflow of the solder for die attach. The coating may isolate at least the conductive material from solder, inhibiting solder wicking or slumping along the conductive material and may enhance adhesion between the resulting bonded conductive element and an underfill material.