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TG grade for PCB manufacture / Assembly.
669 1 Jan 02.2020, 18:13:00

Would be interested to know of your experiences of using various TG Grades of PCB, and why you choose the various things;
My end product is'nt goign to run hot, so that is not a driver for the selcetion.   its a pretty standard 4 layer stack, 1.6mm thick.   The solder process is lead free ( PbF ).    The new PCB assembler I'm auditioning with a few project wants to use TG-170 but the boards end up nearly twice the price of TG-140 or TG-150
I've not had delamination issues using it before.   
Is this an ultra cautious approach on their part or should i run with this suggestion?

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Jan 15.2020, 09:53:30

There are Tg and Td. Tg is glass transition temperature, which should be at least 150 deg C for lead free 4 layer PCB, and preferably 170 deg C+. Td is decomposition temperature, so by definition (unless you want magic smoke ), it should be higher than any expected peak temperature, with margin. De facto standard is 340 deg C.
If you expect more reworking, such as for prototyping, higher Tg is required. I use isola FR408 with 180 deg C Tg and 340 deg C Td, and so far, not problems. I heat each of my board several tens of times to soldering temperature because I use got air gun to rework on them, and so far, only a couple of copper delamination happened

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