| | Hi there, | | Does any one know what is TCE for fully wet saturated FR4. I came to know that for Dry FR4 the TCE is about 15-19 PPM �C. Is that true? | | | | Appreciated for your help. | | rgs, | | chiakl | Chiakl, | It looks like you are speaking of what could also be | termed as "Coefficient of Thermal Expansion (CTE). | This is commonly expressed in cm /(cm * C) or dimensional | change per degree of temperature change. One of my sources | of information states that FR4 is in fact 16. My guess is | that FR4 was engineered to match the CTE of copper. | I am not aware of any studies of CTE reguarding moisture in | FR4. Many in the industry feel that moisture within the PCB | is not much of an issue, and thus leading me to believe that | the CTE should change very little. | Steve A Back in the good old days, when I was a lad, TCE was the term denoting thermal coefficient of expansion just as TCR for resistance and what happened to foot/lbs of torque no reversed. Anyway, Steve is right. Copper foil has a TCE/CTE of 17-19 ppm/C. while typical resin systems (most all including FR-4, polyimide, BT, modified epoxies, etc.) expand at 15-17 in the x and y axes. Moisture is not an issue concerning TCE/CTE as most resin systems (those mentioned above) are between .2-.5% hygroscopic. The most deleterious effect of this moisture is outgassing in poorly drilled, prepared, and plated hole walls. It also is critical in flexible and rigid/flex circuitry but does not concern TCE. Please do not confuse moisture with improperly cured laminate or MLB's. If boards do not reach full cure (molecularly x-linking) all axes suffer and movement is excessive though other problems will be obvious as delamination, pad lifting, etc.. Earl Moon
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Hi there,
Does any one know what is TCE for fully wet sat...
- Jun 25, 1998
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