via capping

SR1000 is commonly used for tenting. Search the fine SMTnet Archives on : tenting

Someone gave us this note. We have lost their name. It seems to be good advice.

If Liquid Photo Image (LPI) solder mask is required, do not tent via holes. Tenting the via holes with LPI solder mask will result in the following problems: * Incomplete encapsulation of the via hole * Exposed copper/metal on via holes * Solder on via pads and in holes * Uncured solder mask in the holes, which result in peeling of LPI and trapping contamination inside the holes.

The solder mask pads for via holes can be made about 5 mils bigger than the via drill size. This will result in deposition of solder in via holes, reducing the possibility of bridging problems during wave soldering operation.

If the via plugging is used to fill open holes with the solder mask to block air leakage during in circuit test, via plugged one side only is the suggested.

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> What material is used to cap a via? Is it the > standard LPI Process/Material?

we tent vias all the time, mostly to assist with assembly and the majority of the time outgassing is not a problem. What is the purpose in your case?

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