This is very essential with dogbone type BGA escaping. Dry Film Solder Mask is a everlasting material primarily used for circuit safety on the outer layer of Flexible/Rigid printed circuit boards, IC substrates and different rigid boards.

The function of the PCB’s soldermask is to protect the copper traces from injury, oxidation, and solder bridging. Tented vias will be extra immune to physical harm and electrical shorts. Vias which are also in shut proximity to SMT pads also needs to be tented. This will prevent the solder paste from wicking into the through and making a poor solder joint.

Whether or not tenting a via with LPI soldermask can be carried out reliably depends on the dimensions of the via. The smaller the via, the simpler it is for the by way of to be filled. After a sure point the vias are too massive and tenting can not be done. This tends to be round 15mil diameter for the through with the LPI soldermask used by MacroFab’s PCB manufacture. Vias bigger then 15mils should be left uncovered so they can be plated with ENIG surface finish instead of relying on the LPI soldermask to seal the by way of.

These bigger vias ought to be avoided areas with solder paste to forestall paste from wicking away from the pad area. Make positive vias underneath BGA components, or vias proper subsequent to SMD pads, are tented. When I design boards, I usually go away vias of any dimension uncovered except they're proper subsequent to a SMD pad.

Due to price implications, fantastic conductive patterns considerably smaller than one hundredµm ought to solely be used when completely needed. For long term reliability of the PCB, and improved manufacturability of the PCB, it's higher to seal the through completely to prevent ingress of moisture and fluids. Filling vias with epoxy and capping (to be defined in a future article!) can be costly.

Tenting through creates a barrier that can help prevent any damages to the PCB layers. If the printed circuit boards are milled, burring may be avoided by designing a conductive pattern with no less than zero.23 mm distance to the contour. The minimal distance between the conductive pattern/copper and outer PCB edge depends on the contour machining expertise used. Generally, a enough distance, considering all the tolerances, is required to keep away from milling off copper. This would creates burrs and outcome in the PCB surfaces being scratched in all subsequent processes when the circuit boards are laid on high of one another.