In the past, defective printed circuit boards have been recycled by using a hot air solder leveling tool to clear solder-plugged vias and plated through holes (PTHs). Such a process, however, required prolonged heating of the entire printed circuit board. The prolonged heating often damaged the circuit board, so the proposed process could never be implemented reliably.
The present invention is a new machine and method for clearing the plugged vias and PTHs of printed circuit boards. The new machine and reworking process utilize localized slow heating of the PTHs that minimizes thermal shock. In addition, the invention does not physically contact the PTHs and surrounding land, thus avoiding or minimizing damage to the metal plating during the reworking process. A plugged hole on the defective panel is heated from below by convection; a subsequent air blast clears the molten solder therefrom.
USPTO Backgrounds
USPTO Backgrounds