Which of the following is the preferred method of cleaning solder from plated-through circuit-board holes?

Using a vacuum device is the preferred method for cleaning solder from plated-through circuit-board holes because it allows for the effective removal of solder without risking damage to the circuit board. This method provides precise suction that can access the holes directly and efficiently eliminate excess solder that may obstruct electrical connections or component placement.

In contrast to other methods, using a vacuum device minimizes potential harm to the board and surrounding components, as it does not apply any additional heat or chemical substances that could affect the integrity of the circuit board material or its plated connections. Additionally, this technique can help maintain the cleanliness of the board, which is critical for ensuring optimal performance and reliability in electronic circuits.

Other methods, while they have their uses, might introduce the risk of damage or leave residues. For example, solder wick relies on capillary action to absorb solder, and while it is effective in many scenarios, it might not completely clear out solder from deeper holes. Brushes may also risk scratching or damaging sensitive surfaces and can fail to remove all solder effectively. Chemical solvents, on the other hand, could harm components or materials on the board if not used carefully.