BQ25792 Charger

@@ -31,44 +31,53 @@ INNER copper layers (2, 15) and the silkscreens do not exist as 3D bodies in a F they are the actual gerber layers rendered to copper/white images, registered to the board outline. The assembled (non-exploded) model is `bq25792-charger-assembled.glb` in Files. -## Board stackup (exact, measured from the design)+## Board stackup (exact physical fabrication stack)  Layer set from the EAGLE design rules: `layerSetup (1+2*15+16)` = 4 copper layers, `mtCopper` 0.035 mm-per layer. Outer geometry measured from the exported 3D bodies (values exact as modeled). The 3D-model adds micro anti-z-fighting offsets, noted exactly.+each. A 4-layer board is fabricated as **copper / prepreg / copper / core / copper / prepreg / copper** -+a thin core carries the two inner copper layers, then prepreg is bonded top and bottom with the outer+copper. The FR4 is NOT one slab: it is prepreg + core + prepreg. Dielectric split fitted to the+measured board (1.516 mm total dielectric): outer prepregs 0.200 each, core 1.046. Exact z, mm: -| # | Layer | z bottom (mm) | z top (mm) | thickness (mm) |+| # | Layer | z bottom | z top | thickness | |---|---|---|---|---|-| 1 | Components (seated on mask) | 1.582 | varies by part | per part |-| 2 | Top silkscreen (ink plane) | 1.582 | 1.582 | ink (~0.010 nominal) |+| 1 | Components (seated on top mask) | 1.582 | varies | per part |+| 2 | Top silkscreen | 1.582 | 1.582 | ink | | 3 | Top soldermask | 1.516 | 1.582 | 0.066 |-| 4 | Top copper, layer 1 (traces) | 1.516 | 1.551 | 0.035 |-| 5 | Inner copper, layer 2 | inside core | inside core | 0.035 (design rules) |-| 6 | FR4 core + dielectrics | 0.000 | 1.516 | 1.516 |-| 7 | Inner copper, layer 15 | inside core | inside core | 0.035 (design rules) |-| 8 | Bottom copper, layer 16 | -0.035 | 0.000 | 0.035 |-| 9 | Bottom soldermask | -0.065 | 0.000 | 0.065 |-| 10 | Bottom silkscreen (ink plane) | -0.065 | -0.065 | ink (~0.010 nominal) |+| 4 | Copper L1 (top, traces) | 1.516 | 1.551 | 0.035 |+| 5 | Top prepreg (FR4) | 1.316 | 1.516 | 0.200 |+| 6 | Copper L2 (inner) | 1.281 | 1.316 | 0.035 |+| 7 | Core (FR4) | 0.235 | 1.281 | 1.046 |+| 8 | Copper L15 (inner) | 0.200 | 0.235 | 0.035 |+| 9 | Bottom prepreg (FR4) | 0.000 | 0.200 | 0.200 |+| 10 | Copper L16 (bottom) | -0.035 | 0.000 | 0.035 |+| 11 | Bottom soldermask | -0.065 | 0.000 | 0.065 |+| 12 | Bottom silkscreen | -0.065 | -0.065 | ink | -Inner layers 2 and 15 are not modeled as 3D bodies by the Fusion export; their copper thickness is-from the design rules (`mtCopper`), and their exact depths inside the core are set by the fab's-dielectric stack (`mtIsolate`: 0.15 / 0.2 mm pattern). Anti-z-fighting offsets in the 3D model,-exact: top mask +0.005, bottom mask -0.005, top copper +0.002, bottom copper -0.002.+Copper L1 and L16 are the real exported 3D bodies (routing as geometry). Inner copper L2 and L15 are+the real gerber layers (`copper_l2.G1`, `copper_l3.G2`) - Fusion does not export inner layers as+bodies. Outer prepreg/core split is symmetric to the measured board; the exact fab dielectric ratio+comes from `mtIsolate` when the fab sets it explicitly. -### Exploded view placement (exact, 5.000 mm per slot)+### Exploded view placement (physical, 6.000 mm per slot, real thicknesses) -| Element | z in exploded model (mm) |-|---|---|-| Components (seat plane) | 26.587 |-| Top silkscreen quad | 21.516 |-| Top soldermask | 16.521 to 16.587 |-| Top copper (layer 1) | 11.518 to 11.553 |-| Inner copper layer 2 quad (gerber) | 6.516 |-| FR4 core | 0.000 to 1.516 |-| Inner copper layer 15 quad (gerber) | -5.000 |-| Bottom copper (layer 16) | -10.037 to -10.002 |-| Bottom soldermask | -15.070 to -15.005 |-| Bottom silkscreen quad | -20.000 |+Each layer is its own slab at its EXACT thickness, separated by 6 mm. The FR4 appears as its three+real sublayers (top prepreg, core, bottom prepreg) with the four copper layers between them:++| Element | slot | z-center in exploded model (mm) | thickness (mm) |+|---|---|---|---|+| Components | +6 | 36 | per part |+| Top silkscreen | +5 | 30 | ink |+| Top soldermask | +4 | 24 | 0.066 |+| Copper L1 (top) | +3 | 18 | 0.035 |+| Top prepreg (FR4) | +2 | 12 | 0.200 |+| Copper L2 (inner) | +1 | 6 | 0.035 |+| Core (FR4) | 0 | 0 | 1.046 |+| Copper L15 (inner) | -1 | -6 | 0.035 |+| Bottom prepreg (FR4) | -2 | -12 | 0.200 |+| Copper L16 (bottom) | -3 | -18 | 0.035 |+| Bottom soldermask | -4 | -24 | 0.065 |+| Bottom silkscreen | -5 | -30 | ink |  ## What the BQ25792 does