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Maximum Time Above Tg for PWB



Maximum Time Above Tg for PWB | 24 January, 2005


I have the below PWB Specifications:

Dimension: 7.25 inches L x 6.45 inches W Thickness: 0.102" (2.5mm) No. of Layers: 12 Material: FR4, Tg >=130�C as per IPC-4104/21

What will happen if I expose the PWB Assembly with components to a temperature of between 135'C to 152'C, which is above Tg, for 1 hour? Will there be delamination or possible damage to my PWB? What about with the rests of the components (0603's, 0805's - ceramic caps etc.)? How about my PBGA with FR4 which will suffer on the same stressful temperature exposure?

The reason for this exercise is a proposal to solder some connectors with more than 200 pins for modification and requires a hot plate with 185'C temp under the PWB during the modification process. Estimated tact time for the process is 60 to 90 minutes.

Thanks in advanced.

Dreamy Thanks and regards,

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Maximum Time Above Tg for PWB | 24 January, 2005

In addition to the potential problems you mentioned, add: * Barrel cracking of PTH and via. * Lifted pads. * Warped boards.

And the reason you're not using a solder fountain to to solder this connector is?

Or use an old trick we've done here on SMTnet for years [NOTE: This is a paste from a previous thread on Mictor connector removal, but you'll get the idea how it'll work in your situation.] as follows: * Buy two Leister [800.700.6894 ] hot air soldering tools, each with a nozzle for your Mictor connector. * Cut a hole in a bench and mount the first Leister underneath with the nozzle at the level of the bench. * Place the board with the connector PTH down on the Leister. * Use the second Leister to the top to melt the primary side solder on the connector. * Pull the connector. * Live well. Live long.

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