Coefficient of Moisture Expansion (CME)

The Coefficient of Moisture Expansion (CME) refers to the change in strain due to moisture absorption or desorption per unit mass variation. The moisture content and strain changes between two moisture equilibrium states are used to calculate the CME.

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<strong>Coefficient of Moisture Expansion (CME)</strong>

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

The coefficient of moisture expansion is a property that is used to define the extent to which a given material expands or contracts as it gains or loses moisture. The property is particularly significant in polymers, composites, and electronics, as exposure to moisture can cause expansion, leading to internal stress.

The coefficient of moisture expansion is defined as the change in dimension per unit length as a function of unit change in moisture content or relative humidity. The property is significant in all instances where there is exposure to varying environmental conditions, especially in electronics, coatings, and structures.

Scope, Applications, and Benefits

Scope

The Coefficient of Moisture Expansion, or CME, test is applicable across a wide range of different materials, including polymer resins, composites, PCBs, electronic packaging, coatings, and laminates. The test is crucial in determining the performance of these types of materials when they are exposed to humid environments, especially when the ability of the material to maintain dimensional stability is of the utmost importance.

What we measure:

– The change in dimensions as the material absorbs the moisture
– The strain that is a result of the absorbed moisture
– The overall expansion of the material due to the hygroscopic effect

Applications

Reliability testing of electronic components
Printed circuit board (PCB) design
Semiconductor packaging
Coating performance evaluation
Adhesive and sealant testing
Aerospace composite materials
Automotive interior and exterior components
Research and development of moisture-sensitive materials

Benefits

Predicts dimensional stability in humid environments
Prevents warpage and delamination
Improves reliability of electronic assemblies
Supports material selection and design
Enhances product durability
Enables moisture sensitivity assessment
Provides standardised evaluation of hygroscopic behaviour
Reduces failure risks in service conditions

Test Process

Sample Preparation & Baseline Measurement

Specimens are prepared, dried, and initial dimensions are accurately measured.

Conditioning & Moisture Absorption

Samples are exposed to controlled humidity and temperature to absorb moisture.

Dimensional Measurement

Changes in specimen dimensions are measured after conditioning.

Calculation & Reporting

CME is calculated from dimensional change data and reported.

Technical Specifications

Parameter	Details
Applicable Materials	Polymers, composites, PCBs, coatings
Environmental Conditions	Controlled humidity and temperature (e.g., 85% RH, 85°C)
Measurement Direction	X, Y, and Z axes (depending on material anisotropy)
Output Units	ppm/% moisture or ppm/% RH
Analysis Type	Dimensional and hygroscopic behaviour analysis

Instrumentation Used for Testing

Humidity chamber (temperature and RH controlled)
Digital micrometre or calliper
Coordinate measuring machine (CMM)
Analytical balance (for moisture uptake correlation)
Data acquisition system
Environmental monitoring sensors

Results and Deliverables

Coefficient of Moisture Expansion (CME) values
Dimensional change data (X, Y, Z directions)
Moisture absorption correlation
Material stability assessment
Comparative analysis under different humidity conditions
Reliability and performance evaluation reports

Why Choose Infinita Lab for Coefficient of Moisture Expansion (CME)?

At the core of this breadth is our network of 2,000+ accredited labs in the USA, offering access to over 10,000 test types. From advanced metrology (SEM, TEM, RBS, XPS) to mechanical, dielectric, environmental, and standardised ASTM/ISO testing, we give clients unmatched flexibility, specialisation, and scale. You’re not limited by geography, facility, or methodology—Infinita connects you to the right testing, every time.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote

Frequently Asked Questions

The significance of CME is that it allows insight into material behavior under conditions of variable moisture level exposure. In general, this occurs in construction, aerospace, the automotive industry, and electronics when the dimensional stability of materials becomes crucial.

CME is commonly used in the determination of polymers, composites, wood, ceramics, and perhaps textiles under conditions of variable humidity.

Common test conditions include elevated temperature and humidity environments such as 85°C and 85% relative humidity, although conditions may vary depending on the application.

Moisture expansion can cause stress between different materials in electronic assemblies, leading to solder joint failure, delamination, or cracking of components.