I'm still working on my board layout while waiting on the final BOM & Schematic. I'd appreciate any comments or suggestions.
1. It sounds like I'll be forced into the BGA I hoped to avoid (176 pin, 0.8mm pitch, 12x12mm package) This means I need a good fan out strategy. Specifically, the third row/column is my concern. I'm thinking of placing vias in the middle of the quadrants formed between the 2nd & 3rd rows.
2. The via size I'm considering is .016 Pad /.008 Hole. With a .062" board thickness this means a 7.75 aspect ratio.
3. For the vias, I'd like to use a smaller annular ring, on the top layer, and a larger one on the bottom. Is this possible with 99SE? If so, how? I appears I can do this with the Pad Stack, but I don't see the same flexibility for vias.
4. 99SE allows me to tent vias. I'm not fully sure of its meaning. Does this mean that the solder mask covers the vias on both sides? I definitely need the vias covered on the side common with the BGA pads. I'd prefer no solder mask covering the via on the opposite side.
5. General Plan (edited from previous post):
Manual route. I haven't heard many positive comments regarding 99SE's auto router.
BGA and fine pitch parts will be fanned out with a via for each pad.
Minimum trace width/clearance = 0.004/0.004",
Minimum annular ring = 0.005" (That is 20/10 vias).
Minimum hole size = 0.008"
Layers = 6 or 8
LPI Solder Mask
.062" Board Thickness
1oz copper
HASL/SMOBC
FR4
Thanks, Steve
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