DSC Differential Scanning Calorimetry: measures the differential energy between a standard and a sample, energy is applied to both and the endothermic or exothermic response of the sample is measured. This is the difference in energy seen between the standard (possibly an empty cell or a blank sample) and the sample hence the term differential. Any extraneous materials present or absent will significantly effect the results measured hence the difference in expected results between samples with and without copper. The presence or absence of copper will more likely effect the heat sink and hence the overall results. DMA Dynamic Mechanical Analysis measures the mechanical response, expansion, contraction, physical structural changes that take place as energy is applied e.g. as the Tg is exceeded. The measurement is that of a physical movement. There is no differential comparison as in DSC so although the presence or absence of copper, if that is the material incorporated, can potentially effect the DMA results, the effect is significantly reduced. Note energy applied can be isothermal or dynamic (positive or negative). Andrew Hoggan BBA Associates Ltd www.bba-associates.com -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Timothy Reeves Sent: 21 September 2001 17:51 To: [log in to unmask] Subject: Re: [TN] Tg measurements by DMA DSC (Differential Scanning Calorimetry) measures the temperature of the material as known quantities of heat are added to it. This behavior depends on absorbed moisture content which in turn is affected by whether or not the material is copper clad or not. DMA measures mechanical properties as the material's temperature is raised which do not so much depend on moisture content. Tim Reeves ECD -----Original Message----- From: Gerard O'Brien [mailto:[log in to unmask]] Sent: Thursday, September 20, 2001 8:23 AM Subject: Tg measurements by DMA When testing Tg with DSC, the TM-650 test method calls out for the test to be run with the copper clad still attached and that if removed to expect an 8 to 15 degree reduction in values. For DMA it does not reference testing with copper clad or removed. Can anyone give me the reason why? Regards Gerard O'Brien ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------