Matseng added some test patterns to his latest batch of PCBs to stress the limits of Seeed Studio’s PCB service. Seeed advertises 6mil/6mil in their specification, so Mats added concentric circles in 6mil trace/6mil space, 5/5, 4/4 ,3/3, and 2/2 sizes.
As can be seen on the picture above even 3/3 mil seems almost perfect as long as it’s covered by soldermask. The HASL doesn’t work too well even at 6/6 when there’s no soldermask between the tracks. I suppose that ENIG (gold) would be ok at 3/3, but that test will have to wait for a later time.
Check out the hi-res pictures in the forum. Later this month we’ll be visiting the PCB fabrication plant Seeed uses, and we’ll bring you the inside look at their operation.