Via tent on both side of the PCB; Immersion Tin| 6 October, 2001
Yes, some solder masks do not tent well, because the material is too thin. That�s the trade-off. Thin masks: * Conform well to [don't bleed onto] fine pitch features. * Tent vias poorly, requiring an additional "plugging" step.
As you imply, if the via is open, process chemicals can enter the via. * Your fabricator can discuss the impact of these chemicals on the LT reliability of your product. This may require contacting Dexter or Florida CirTech (Omicron), the two companies that license the process to fabricators. [Check the fine SMTnet Archives for contacts.] * Alternately, a test lab can analyze there presence of and discuss the potentail impact of chemicals in your vias.