Power Semiconductor Moisture Barrier Coating for Reflow Reliability

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Solution Overview

Problem

Packaged power semiconductor devices are susceptible to moisture absorption, leading to delamination, cracking, or explosion during the soldering reflow process, which can result in premature device failure, and this issue complicates the fabrication process and increases the risk of moisture-induced failure in larger electronic systems.

Innovation Solution

A moisture barrier is applied conformally to the plastic overmold encapsulation of power semiconductor devices, using materials like acrylic, polyurethane, or silicone, to prevent moisture ingress and extend the time the devices can be exposed before soldering, while also maintaining thermal conductivity and electrical insulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the plastic overmold encapsulation is used to package power semiconductor devices, then the manufacturing cost is reduced and ease of manufacture is improved, but the device becomes susceptible to moisture absorption leading to delamination, cracking, or explosion during soldering reflow

Engineering Contradiction:

Improveease of manufactureVSAvoidreliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies a moisture barrier coating composed of inorganic materials (such as silica, alumina, or titania) deposited on the plastic overmold surface. This creates a composite structure combining organic plastic material with inorganic moisture-blocking layers, achieving both ease of manufacture and moisture protection reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent uses thin film moisture barrier coatings deposited on the plastic overmold surface. These thin inorganic film layers provide effective moisture protection while maintaining the flexibility and manufacturing advantages of the plastic encapsulation structure.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If a moisture barrier coating is applied to the plastic overmold, then the reliability is improved by preventing moisture absorption, but the device complexity increases

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the moisture barrier function with the existing plastic overmold encapsulation structure by depositing inorganic coating layers directly on the mold surface before or during the encapsulation process. This integration approach adds moisture protection without significantly increasing overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent modifies the surface properties of the plastic overmold by changing its chemical composition through deposition of inorganic materials. This parameter change transforms the surface from moisture-absorbing to moisture-resistant while maintaining the bulk properties of the plastic encapsulation.

Inventive Principle:

Principle #35Parameter changes

3Duration of action of stationary object

If the moisture barrier coating is applied to the plastic overmold, then the duration of action is extended allowing longer exposure times before soldering, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveduration of actionVSAvoidmanufacturing precision

Core Design Contradiction:

Duration of action of stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies the moisture barrier coating to the mold surface before injecting the plastic material. This preliminary action ensures that the moisture protection is established prior to encapsulation, allowing extended exposure times and improving manufacturing precision by preventing moisture-related defects during the molding process.

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 moisture barrier significantly reduces the risk of moisture-induced failure, allowing for longer exposure times before soldering and improving device reliability by preventing moisture absorption into the overmold encapsulation, thus enhancing the stability and performance of power semiconductor devices.

Implementation Method 1

a moisture barrier is applied conformally to the plastic overmold encapsulation of power semiconductor devices, using materials like acrylic, polyurethane, or silicone, to prevent moisture ingress

Methodology Applied

Scientific EffectPhysical barrier (moisture barrier):

Implementation Method 2

A moisture barrier is applied conformally to the plastic overmold encapsulation

Methodology Applied

Scientific EffectConformal coating: Deposition (physical)

Implementation Method 3

while also maintaining thermal conductivity and electrical insulation

Methodology Applied

Scientific EffectThermal conductivity: Conduction (thermal)

Implementation Method 4

while also maintaining thermal conductivity and electrical insulation

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS20230378010A1Power semiconductor devices having moisture barriers

Publication Date: 2023.11.23 WOLFSPEED INC

AI summary

A power semiconductor device comprises a package, a power semiconductor die within the package, and a moisture barrier on an upper surface and side surfaces of an exterior of the package.