What�s the problem?
There area many heat related failure mechanisms in bare boards. You can damage boards with heat several ways. A couple favorites [Don�t try this at home. Perform on a closed track by professional solders only.] are: * Put a heated soldering iron on a pad for about 30 seconds. * Put a board on the rocks [ice] for a couple hours and then run it over the wave/reflow. * Put a board in a bucket of water overnight, dry it off, and then run it over the wave/reflow. * Put the conveyor in 4th gear, put a board on the conveyor, and then run it over the wave/reflow.
Your FR-4 board is fabricated from layers of: * Copper * Epoxy * Woven fiberglass
Each succeeding layer has different properties [ie, CTE, tg, etc.].
Solder Float Test: * J-STD-003 4.2.3.4.1 After fluxing and draining per . . . slide the coupon gently on molten solder. Allow coupon to float on solder for 5 seconds maximum. The coupon may be depressed into the solder bath to a maximum of 50% of the coupon thickness after it has been initially floated on the solder. After the elapsed time, slide the coupon off molten solder. Hold coupon still and horizontal until solder solidifies. * J-STD-003 section 3.5.1 The bulk temperature of the solder bath shall be maintained at 245�C + 5�C [473�F + 9�F] unless another temperature is agreed to by the vendor and user.
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