IPC Committee Revises DSC Test Method for Tg

Reading time ( words)

IPC’s 3-11 Laminate/Prepreg Materials Subcommittee has announced the publication of the latest revision of the test method for the determination of glass transition temperature (Tg) of copper-clad laminates (CCL). IPC-TM-650 Method 2.4.25 utilizes Differential Scanning Calorimetry (DSC) to measure the Tg of the base materials for rigid printed circuit boards. The Tg is one of the characteristics used to estimate the thermal reliability of materials used in electronics.

The key change in the document clarifies what is and what is not a phase transition as the temperature approaches the Tg for the first time. In the past, the unusual exotherms or endotherms could be interpreted as being a Tg. There are a number of reasons cited for these spurious events including stress relief, release of moisture and evaporation of residual solvent. The Pre-Scan step is needed to make the baseline more stable for the calculation of Tg1 and Tg2. The Pre-Scan takes the temperature to about 10°C above the predicted Tg1, then the sample is cooled immediately back to the starting point temperature. The determination of Tg1 is then carried out by a second scan which terminates at either 175°C or 190°C depending of the type of epoxy resin system. At the termination temperature, the specimen is held at isothermal conditions for 15 minutes before cooling again to the starting point temperature. Finally, a third scan is conducted to determine Tg2. It is Tg1 and Tg2 that are used to calculate either the cure factor or the delta Tg.

All of the IPC-TM-650 test methods can be found free of charge at the IPC website, www.IPC.org under the “Knowledge” tab. 


Suggested Items

Institute of Circuit Technology Meriden Seminar, 2018

03/21/2018 | Pete Starkey, I-Connect007
The Institute of Circuit Technology returned to Meriden, traditionally regarded as the centre of England, for its Annual General Meeting, which was followed by a technical seminar of five presentations, introduced as ever by Technical Director Bill Wilkie.

RTW IPC APEX EXPO: IPC—Industry Trends Moving Forward

03/20/2018 | Real Time with...IPC
Sharon Starr, director of market research for the IPC, discusses industry trends moving forward covering both EMS and PCB. She also mentions the upcoming studies IPC will be conducting in 2018.

Bridging Knowledge and Understanding of Thermal Management Materials

03/14/2018 | Pete Starkey, I-Connect007
At IPC APEX EXPO recently, Pete Starkey and Ian Mayoh, Ventec International’s technical support manager, had a chance to sit down and discuss the I-Connect007 micro E-book: The Printed Circuit Designer's Guide to Thermal Management with Insulated Metal Substrates, of which Ian is a co-author.

Copyright © 2018 I-Connect007. All rights reserved.