Hi Geof, Paul, Steve, Michael & ALL,
Mea culpa, sorry, Verzeihung, etc.
>How can Resin=30-40; Cu=17-18 and the combination=8?
Converting fonts got me into trouble; please accept my apologies. Find
correction below:
The CTE for FR-4 resin (not laminate) is:
CTE(<Tg) = 30 to 40 ppm/°C, CTE(>Tg) = 90 to 130 ppm/°C.
The CTE for FR-4 laminate is: CTE(x,y) = 18±2 ppm/°C;
CTE(z,<Tg) = 50 to 85 ppm/°C, CTE(z,>Tg) = 240 to 390 ppm/°C
CTE(Cu) =17 to 18 ppm/°C.
And to answer Steve's question completely, the CTE(x,y) = 18±2 ppm/°C, even
though
resin=30-40; Cu=17-18 is because of the glass-fiber reinforcements
constraining the CTE(x,y) of the laminate; that is also the reason why CTE(z)
is 2 to 3 times the resin CTE.
CTE measurement and reporting unfortunately is not standardized. Outside the
region of Tg +/-25C the CTE values are pretty constant. Thus good test
temperature ranges would be (Tg - 75) to (Tg - 25) AND (Tg + 25) to (Tg +
75); any test range that includes the Tg is nonsensical and useless for any
other T-range, because it combines non-linear behavior into a single number.
When you have multiple materials with different Tg's, you have a more
difficult time. But if you have the correct CTE's below and above Tg, you can
figure out the thermal expannsion for any T-range.
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################
|
