Plugging via holes with LPI solder mask is actually superior to trying to
tent them with dry film solder masks for a number of reasons:

1. When you plug with the LPI masks, you completely fill the holes with the
solder mask polymer. Therefore, the corrosive fluxes cannot enter the via
holes and cannot come into contact with the metallized hole where corrosion
problems and, hence, reliability problems can occur.

2. No dry film solder mask supplier can guaranty 100% perfect tented vias and
there is always a chance that some of the tents will crack or break. When
this happens, fluxes will enter the via holes and there is no way to remvoe
these flux residues. The end result is the potential for corrosion and
reliability problems.

Bottom line! Plug the via holes with LPI solder mask and don't try to tent
them
(you';; save some money too)

Regards,

Larry Fisher
[log in to unmask] 

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]>   *
* with <subject: subscribe/unsubscribe> and no text in the body.          *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************