Electronic – Are thermal reliefs on SMD pads beneficial when reflow soldering

I've left wet paste on a board overnight in cool weather without problems, but I'd be worried it would dry out over a few days - especially if left uncovered in a refrigerator (although I'm not sure if this would adversely effect the reflowing).

If there are pads under the parts, then soldering with an iron is out of the question, but a hot air rework gun should work fine. Depending on the complexity and the number of missing parts, I would either:

• Flow now and solder the additional parts later (you can place a cube of metal under specific parts of the board to reflow individual parts on the hotplate).
• Clean the board and restart when you've got the new parts

Because PSUs use many big lumpy parts that are not SMDable and/or need good mechanical fixing. Also, for minimum cost they like to use single-layer PCBs - TH is a little more amenable to this as parts act as jumpers over tracks. TH parts can be machine-inserted - e.g. http://www.youtube.com/watch?v=eOQ3pZkKX24 (30kparts/hour!)