Re: SDR Micron - 14-bit Direct Digital Conversion Receiver with USB connection

Marc olanie

hi Steven
Any manufacturer will do the same. As long as the soldermask is wrong, all via are "tented" by default. This is specifically mentionned by all pcb manufacturers (and it's a necessity if you don't want shorts between vias and pads during a reflow process). It is strictly impossible to have some tenting if the gerber file shows a well defined solderpaste mask. 

To avoid this kind of trouble, a "no soldermask" zone and a solderpaste mask should be defined -and designed- for each IC if handsoldering is considered (and probably a large 1.5mm to 2 mm "super via"  for the gnd pad soldering when possible) 

in this case, you can circumvent the problem with a fiberglass pencil and scratch the tenting and the surrounding area of the lower side.  You can also (not recommanded) use a hot air reworking gun and solder your QFN after some pre-tinning the pads on the component side. That's what I call a "a phone repairer tip". Not elegant at all but it works (not always) 
Marc f6itu
ps : using fiberglass pencils is a rather dangerous process. One should wear gloves, protective googles and a mask to avoid breathing small glass particles. The working area should be carefully cleaned after each operation. 

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