Video: Dynamic Mechanical Analysis

 

Dynamic Mechanical Analysis or DMA measures the storage and loss modulus and Tan Delta of a material. Storage or elastic modulus is a material’s ability to store energy applied to it for future use or to spring back when deformed. Loss modulus is a material’s ability to dissipate energy that is applied to it. For example, when silly putty is stretched the energy that goes into it is lost and it cannot return to its original shape. Tan delta is the ratio of the storage to loss modulus.

These measurements are calculated from a sample’s response to a change in position when a known force is applied to it. The most common clamps are dual cantilever, single cantilever and thin film. It is important to remember that because the force is applied to the sample differently with each clamp, the results cannot be compared. Unless otherwise noted, the results reported by Isola’s Analytical Services Lab use the dual cantilever clamp.

The temperature of the sample can be held isothermally or changed at a fixed ramp rate. Sample temperature is measured indirectly by a thermocouple. Careful calibration and a slow ramp rate of 3°C per minute ensure the temperature of the sample is the same as the reported temperature within plus or minus 2°C.

The glass transition is very complex and causes changes in many measurable characteristics over a temperature range; a significant decrease in storage modulus, a peak in loss modulus and a peak in tan delta. Several methods have been defined to assign a single temperature. It is important that temperatures be assigned by the same method if they are to be compared. Unless otherwise noted, the glass transition temperature reported by the Isola ASL is the temperature of the peak in the tan delta curve.

Laminates and printed wiring boards are composites and many factors affect their modulus value, therefore, modulus values are not reported. An incomplete list includes overall resin content, glass type, stack up of laminate and prepreg, grain direction and presence of copper. Changes in modulus, indicating the glass transition region are not affected by these factors, because they only occur within the resin component.

Two characteristics of printed wiring boards will affect the glass transition temperature. Samples with large copper content heat slowly and the temperature error increases with the amount of copper. Results for these samples will be noted as “clad.” Plated thru holes also cause a temperature error and affect the sample’s ability to respond to the instrument force. The glass transition temperature cannot be measured with confidence when they are present.

18 October 2013

Related Posts

How Much Bandwidth Does A High Speed Differential Pair Require
How Much Bandwidth Does a High-speed Differential Pair Require?
Watch Lee Ritchey of Speeding Edge as he discusses high-speed differential pairs. Topics addressed in this video include: A description of the two basic logic signaling protocols—single-ended logic paths and differential signaling paths and how these two protocols are very different. How single-ended logic paths have inputs that…
Microwave Journal
CEO Jeff Waters Featured in the Microwave Journal
Minimizing time to market through a global presence that is close to customers Isola is a material sciences company that develops and manufactures laminate materials that are used to fabricate advanced multilayer printed circuit boards. The company has a global footprint, with manufacturing and research centers in Asia, Europe and…
IPC Apex Expo February 19 21 2013
IPC / Apex Expo – February 19-21, 2013
Isola exhibited in booth 1717 at the Apex Expo / IPC on February 19-21, 2013 at the San Diego Convention Center. This is the largest and most prestigious electronics assembly exhibition and event in North America with over 8,900 colleagues from more than 50 countries.