Jon Chung — Adom Molecule LED Nameplate

@@ -0,0 +1,134 @@+# Jon Chung: an Adom molecule LED nameplate++Jon Chung's name, **etched out of the soldermask over the ground plane**, lit by+15 side-view LEDs that fire inward across the board, powered from any+USB-C phone charger, and mountable in a probing workcell by four large machine+pins on the 32 mm base-scaffold grid.++## The one idea++**The name is the ground plane.** A rectangular GND copper pour covers the top+layer, and the soldermask is opened in the shape of the letters so bare plated+copper shows through. There is deliberately **no second ground path** (no+bottom ground pour), so every milliamp those 15 LEDs draw physically+crosses the letters on its way back to the connector.++So the line you get to say to Jon Chung, *"your name is part of the electrical+path that lights up the LEDs"*, is a statement about the netlist, not a+slogan. It is enforced by construction: the ground pour is sized to swallow+every ground pad on the board, so ground is bonded by geometry and the+autorouter is never given the chance to route a shortcut around the letters.++## The board++| | |+|---|---|+| Board | 268 x 76 mm, 2 layer, 4 mm corner radius |+| Pin box | **256 x 64 mm** = 8 x 2 on the 32 mm grid |+| Name | 209.2 x 40 mm, Familjen Grotesk Bold |+| Mask openings | 478 letter polygons |+| GND plate | 261.6 x 69.6 mm, top layer |+| LEDs | 15 x Würth WL-SMSW `155060GS75300`, 515 nm side-view |+| Current | 180 mA @ 5 V (15 x 12 mA) |+| Parts / traces / vias | 40 / 63 / 35 |++### Molecule compliance++Per [molecule-design-guide](https://wiki.adom.inc/adom/molecule-design-guide)+and [base-scaffold-system](https://wiki.adom.inc/adom/base-scaffold-system):++- A **large machine pin at every corner** (3.6 mm body press-fit into a 3.45 mm+  plated hole, 0.15 mm diametral interference).+- The pin box is **256 x 64 mm**, both exact multiples of 32 mm (the base+  scaffold's large-contact pitch), so it drops straight onto 9 x 3+  contact positions of the 18 x 18 field across the 576 x 576 mm workspace.+- **Minimal wings:** the board stops 6 mm outside each corner pin. That is as+  tight as the pin allows: a 5.2 mm annular ring eats 2.6 mm of it, leaving+  3.4 mm of solid laminate, about 2x board thickness, which is what a press-fit+  needs so insertion force does not crack the edge out.+- Corner pins carry power, not just mechanics: **MP1/MP4 are GND, MP2/MP3 are+  +5 V**, so the plate can run off a workcell control panel instead of USB-C.+  The GND pins land inside the plate, which means the scaffold's ground return+  also passes through the name.++## Why side-view LEDs++A normal chip LED is a top-view emitter: it fires straight up, away from the+board, and the copper you are trying to light sees nothing. This board uses a+true **side-view** part. The die sits on its side behind a window in the long+face of the package, so the beam leaves *parallel* to the board about 0.5 mm+above the soldermask. Ringed around the edge facing inward, the light rakes+across the plate at a grazing angle and washes the exposed-copper letters+instead of escaping to the sky.++Worth knowing if you go sourcing: Kingbright's `APTR3216` family is+*reverse-mount* (it fires down through a hole in the PCB) and Broadcom's+`HSMx-C265` is bottom-entry. Both come back in a "right angle SMD LED" search+and neither does this job.++- 1.6 x 0.8 x 1.1 mm; 2 pads 0.6 x 0.8 mm on 1.4 mm pitch+- 515 nm peak / 525 nm dominant, 260 to 560 mcd @ 20 mA, 140 deg 2θ½+- VF 3.2 V typ; run here at 12 mA through 150 R++## Power++USB-C VBUS (5 V) -> 150 R -> LED (3.2 V) = 12 mA each, **180 mA total**, well+inside the 500 mA a charger gives an unnegotiated sink, so any phone brick+works. `R_CC1`/`R_CC2` are the mandatory Rd pulldowns. Without them on *both*+CC lines a USB-C source never enables VBUS at all and the board is dead.++Layer plan is inverted from the usual convention on purpose:++- **Top** = GND, one rectangular pour. The name is cut out of it.+- **Bottom** = +5 V plane.++Everything is placed on the **top side only** (the line does single-sided+pick-and-place), so each LED string runs LED -> 150 R -> a via down to the +5 V+plane, while the cathode bonds straight into the plate.++## BOM++| Ref | Qty | Part | Package |+|---|---:|---|---|+| D* | 15 | Würth WL-SMSW `155060GS75300` side-view green 515 nm | 0603 side-view |+| R1 to R15 | 15 | 150 R ±1 % `CR0402-FX-1500GLF` | 0402 |+| R_CC1/2 | 2 | 4.7 k ±1 % `CR0402-FX-4701GLF` | 0402 |+| C1 | 1 | 10 µF X5R `0603X106K100CT` | 0603 |+| C2 | 1 | 100 nF X7R `0402B104J160CT` | 0402 |+| J1 | 1 | `TYPE-C-31-M-12` USB-C (JLC C165948) | SMD + 4 plated anchors |+| MP1 to MP4 | 4 | `MachinePinLargeStandard` | 3.45 mm plated hole |++Passives are all Adom Basic Parts. The LED is Mouser/DigiKey (~$0.40).++## Fab notes++- **Specify ENIG, not HASL.** The letters are 209 x 40 mm of deliberately+  bare copper and are the entire point of the board. HASL leaves them lumpy,+  ENIG leaves them mirror flat.+- Dark soldermask maximises contrast against the exposed letters.+- The four 3.45 mm machine-pin holes are an **interference fit** and are meant+  to be undersized. Do not let a fab house "correct" them to a clearance fit.+- Tented/plugged vias: there are vias whose rings lap onto LED resistor pads.++## Verifying the mask opens++Do not trust the render. Read the gerber. `F_Mask.gbr` is negative polarity+(`%TF.FilePolarity,Negative*%`), so what is *drawn* is where mask is *removed*:++- **478 region polygons**, bounding box **209.18 x 40.00 mm**, the letters+- the plate rectangle **absent** from F_Mask (present would mean inverted)+- **zero** letter regions in `F_Paste.gbr`. The letters are decoration, not+  solder joints, and must never be stencilled++## Reproducing it++Built with [adom-tsci](https://wiki.adom.inc/adom/adom-tsci) from a parametric+tscircuit source. One command per name:++```bash+scripts/make-nameplate.sh "Jon Chung"+```++Board size, pin box, LED count and silkscreen are all derived from the name's+ink box, so a new name is a one-liner. The source bundle attached to this page+has everything.