On Friday, June 23, 2017 at 4:09:03 AM UTC-4, N_Cook wrote:
Chinese no-name YXY-FGD-50W
White goo under the LED metal backing, only covering about 1/3 of the
area, as originally placed blob , not fully splurged. Bowing of the
metal at rear of the LED array , probably at original placement due to
blob shape of the goo , only maybe worsened in use. So heatsinking via
the periphery only , ie delayed heatsinking.

The 12v 5A SMPS units from China as well only have a thin seam of white thermal paste at the edge of the switching transistors to make it 'appear' properly done, there is none between the transistor and the heatsink = early failure.

I have to reapply paste on all before I use them.