Silicone Check Valve for Pb-Free Electronic Package Integrity

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Solution Overview

Problem

Current electronic packaging solutions fail to maintain package integrity during lead-free solder reflow temperatures, as the increased temperature leads to moisture intrusion and premature failure due to the inability of existing materials to manage internal pressure and condensation expansion.

Innovation Solution

Incorporation of a silicone rubber umbrella check valve that allows expanded air and steam to escape while preventing external moisture and contaminants from entering, maintaining package integrity by using a commercially available silicone rubber valve that can withstand high temperatures and is integrated into the package cap without increasing its height.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the package uses a standard plastic cap bonded with epoxy to create a near airtight cavity, then package sealing is improved, but internal pressure management deteriorates during lead-free reflow

Engineering Contradiction:

Improvepackage sealingVSAvoidinternal pressure

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The cap is segmented into two functional zones: a sealed perimeter region that maintains package integrity and a central vent region with a check valve that manages internal pressure. This segmentation allows the cap to simultaneously provide both sealing and pressure relief functions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A silicone rubber check valve acts as an intermediary component between the package interior and exterior. It selectively opens to vent pressure when internal pressure exceeds external pressure, and closes when external pressure exceeds internal pressure, mediating the pressure differential without compromising the sealed cavity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the package is sealed airtight to prevent moisture intrusion, then moisture protection is improved, but moisture management deteriorates during reflow heating

Engineering Contradiction:

Improvemoisture intrusionVSAvoidcondensation expansion pressure

Core Design Contradiction:

Object-affected harmful factorsVSStress or pressure

Solution Approach 1:

The check valve converts the harmful effect of condensation expansion into a beneficial pressure relief mechanism. By allowing the condensation to expand and push the check valve open, the system automatically vents the excess pressure and steam, preventing package failure while maintaining moisture protection during normal operation.

Inventive Principle:

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

3Stress or pressure

If a vent is added to the cap to relieve internal pressure, then pressure management is improved, but package integrity deteriorates due to potential moisture entry

Engineering Contradiction:

Improveinternal pressure reliefVSAvoidpackage integrity

Core Design Contradiction:

Stress or pressureVSReliability

Solution Approach 1:

The check valve provides dynamic pressure management by automatically opening and closing based on the pressure differential between package interior and exterior. This dynamic response allows pressure relief when needed while maintaining sealing when not needed, preserving package integrity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The silicone rubber check valve utilizes the flexibility of elastomeric materials to create a one-way sealing mechanism. The flexible membrane can deform to open the vent passage under positive internal pressure while elastically returning to seal the passage under external pressure, providing intelligent pressure management.

Inventive Principle:

Principle #30Flexible shells and thin films

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 manages internal pressure and moisture expansion during lead-free solder reflow, reducing gross failure rates and ensuring package reliability by allowing controlled venting and sealing, thus qualifying for Pb-free solder reflow temperature requirements.

Implementation Method 1

the air inside the package is heated and thus expands at a predictable rate per the Ideal Gas Law

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the amount of moisture or condensation a given SPM may have inside. All packages will have some amount of liquid water due to capillary condensation inside the micro-voids of the package components

Methodology Applied

Scientific EffectCondensation expansion: Phase Change

Implementation Method 3

a silicone rubber umbrella check valve inserted into the cover or cap

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS7675149B1Check valve package for Pb-free, single piece electronic modules

Publication Date: 2010.03.09 MAXIM INTEGRATED PROD INC

AI summary

Check valve package for pb-free, single piece electronic modules, the package having an exterior and an interior, and at least one electronic device mounted within the interior of the package electrically connected to a lead-free solder ball grid array on a surface of the package, the package having a check valve between the interior and exterior of the package configured to allow flow from the interior to the exterior and to prevent flow form the exterior to the interior. The package withstands the solder reflow temperatures for the reflow of the pb-free solder balls of a ball grid array packaging of an NVSRAM during mounting on a circuit board. The package is suitable for packaging circuits containing rechargeable batteries and for packaging other electronic devices.