Chinese designs are a PAIN!!!!!!!1 cheap build quality and poor solder joints being made. And now with lead free coming in the poor solder quality is really affecting mainboard connections. BGA's are failing at a rate of knots and the whole thermal problems are getting worse as the lead free joints are more brittle then tin/lead soldering.
Damn cheap builds and lead free soldering really dont mix, I had a laptop in the other day, intermittant as hell. Seemed more stable once warm, struck as a poor solder joint somewhere, luckily saw that it had a few memory issues once it did boot so resoldered the lead free DIMM skts with normal tin/lead solder. Fixed it first time :D however not all fixes are as easy as that, and lead free is making things a whole hell of a lot harder:'(
Here's what I do, I will blend 60/40 with the lead free*, then cover all of it with flux, then flow the iron across it. Also verifyling that I didn't short close connections... If there is too much, I will wick off the excess, then flow again. Not leaving the iron in one spot too long.
That will also allow a lower melting point vs Lead Free alone. Too bad Radio Shack still haven't gotten good irons and tips for the lead-free work yet.