PCB Assembly Services - Screaming Circuits: Tented QFN/QFP Via in pad


Tented QFN/QFP Via in pad

Tented vias in padHere's a pretty decent example of mask-tented vias in the thermal pad of a QFP. Most manufacturers recommend no more then 100 - 125 um wider than the via to minimize voiding and thermal insulation in cases like this. This is a reasonably inexpensive way to handle vias in the thermal pad. Sometimes though, the tents will pop open allowing solder to wick down through the via.

The mask over the center via on the right looks a little thin, so you'd want to give it an extra look over after reflow to make sure it's okay. (We'd do that here, of course)

We'd rather not see this technique on really small parts because it gets difficult for the fab house to put the mask down with enough precision. With small parts, filling and plating over the vias is the preferred technique. Well, that's always the preferred method. It's just more important with smaller parts and BGAs. This method is acceptable for most QFPs and larger QFNs though.

Duane Benson
All your via are belong to us


TrackBack URL for this entry:

Listed below are links to weblogs that reference Tented QFN/QFP Via in pad:


The particular form of the mineralised woodchips is a unique attribute of Cemwood leveling material. The geometry of the chippings permits the leveling material to interlock (clawing mechanism) thus ensuring consistent results in use. As a consequence of this distinctive materials characteristic the pouring, filling and surfacing of Cemwood allows it to level with ease. The settling behavior is near 0, which signifies that compaction of the fabric after surfacing is not necessary. The levelling material can be filled in its dry and free type and is similar to stable infill. This has the major benefit for builders to be able to continue flooring buildup instantly after filling.


Post a comment

If you have a TypeKey or TypePad account, please Sign In.

« What is it? | Main | What it is... »