PHASE 06ORDERING
Commit the design to the real world: boards from a fab, parts from distributors.
Ordering is mostly a handful of choices and a lot of double-checking. There are two carts to fill — one at the board house, one at the parts distributor — and a few traps that cost you a week if you miss them.
A few options turn your Gerbers into physical boards.
Upload the Gerber zip and pick the fab options: a 2-layer board, a thickness (1.6 mm is standard), and a surface finish — (cheap, slightly lumpy) or (flat gold, better for the WROOM's fine-pitch pads). Order a few spares; the extra board is nearly free, and the shipping isn't.
Your board has the fine-pitch WROOM module pads. HASL or ENIG? ENIG — its flat surface solders fine-pitch parts more reliably than lumpy HASL.
▸Deep dive· ENIG vs HASL — why the finish matters here
Bare copper pads tarnish, so the fab coats them. (hot-air solder leveling) dips the board in molten solder and blows the excess off with hot air — cheap and very solderable, but it leaves the pads slightly domed and uneven in height. plates a flat layer of nickel capped with a thin gold flash — dead flat, long shelf life, a little pricier. For through-hole and 0805 work, HASL is perfectly fine. But the WROOM's underside pads are fine-pitch and packed close, and there a flat surface lets every pad meet the module at the same height; uneven HASL bumps invite a missed or bridged joint you can't even see under the module. That flatness is what makes this board worth the ENIG upcharge.
Your BOM becomes a shopping cart — with a few traps.
Order every line by its exact . Mind the — passives come on reels of thousands — and buy extra of the parts you'll hand-place and lose. If anything is out of stock, this is where the second sources you noted back at sourcing (the RT9080-for-AP2112K, the UMW USBLC6-2) pay off.
You need two 5.1 kΩ resistors but they sell in reels of 5,000. What now? Buy the reel — it's cents — and keep the spares. Always order a few extra of any part you hand-place.
Quick check — ordering
Create the build, then attach the PCB order and the parts order to it.