Difference and Tolerance Explanation Between Via and Pad Holes in PCB

What is the difference between Via and Pad in PCB design files?

A via is also known as a through-hole, and it comes in types such as through-hole, blind hole, and buried hole. It is primarily used for connecting circuits on different layers while it cannot be used as a soldering hole for component insertion. During production, the diameter of via holes is not controlled (JLC currently does not process blind holes or buried holes; only through-holes are supported).

The main function of a via is electrical connection. In actual production, the hole size may be adjusted to combine closely spaced holes to reduce the number of drills and improve work efficiency. Alternatively, the hole size might be reduced due to limited space between lines and widths to meet production requirements. Via holes are generally smaller. As long as the PCB manufacturing process is achievable, it is sufficient.

The surface of a via can either be coated with solder mask ink or left uncoated. Besides, the via hole can support the filling of ink, resin, or copper paste.

A pad is referred to as a solder pad, which includes through-hole pads for legged components and surface-mount pads for surface-mount components. Through-hole pads have solder holes mainly for soldering legged components, while surface-mount pads do not have solder holes and are mainly for soldering surface-mount components.

In production, pad holes are controlled for diameter (the diameter of pad holes are controlled), with a tolerance of +0.13mm/-0.08mm (for strictly controlled tolerances, a press-fit hole can be made with a tolerance of +/-0.05mm).

Pad holes not only serve the electrical connection but also provide mechanical fixation. The diameter of pad holes must be large enough to pass through the component's pins. Otherwise, it may cause production issues (considering the possibility of negative tolerance, under permissible design and assembly conditions, it is recommended that pad hole designs exceed the maximum size of component pins by 0.1mm (such as the diagonal of a square). Additionally, since drill bit sizes are fixed in metric units, it is advisable to design hole diameters in metric units with one decimal place (e.g., 32 mil converts to 0.812mm, and the actual processing diameter is 0.8mm; 40 mil converts to 1.012mm, and the actual processing diameter is 1.0mm)."