One public FCC filing, two teardown videos, and our own attempt to spec a 10,000-unit custom phone.

The spec this post orbits around

Current working selections (full decision log: custom_phone_design_decision_summary.md):

Subsystem My selection Working cost (@~10k units)
SoC Qualcomm Snapdragon 7 Gen 4 (SM7750-AB, 4 nm)* $30–40
RAM 12 GB LPDDR5X $10–15
Storage 256 GB UFS 4.0 $15–22
Display 6.36” 1080×2400, 120 Hz AMOLED, matte glass option $25–40
Main camera Sony LYTIA 808, 50 MP, OIS $20–30
Front camera Samsung ISOCELL 3LU, 12 MP, autofocus $3–7
RF front-end PA/PAMiD modules, tuners, switches — set by the band plan (§2) $8–15
Companion kit RF transceiver + PMICs + Wi-Fi/BT + audio codec, platform-mandated (§2) $12–20
PMIC / power tree matched to platform; not fully selected $3–6
Battery 6000 mAh silicon-carbon, removable $8–12
Biometrics Fingerprint in power button (Goodix), no Face ID $1–3
SIM eSIM-only (no tray) —
Charging USB-C, 45 W PD $2–6 (USB subsystem)
Audio ≥3 mics, stereo speakers $2–5
Haptics LRA actuator $0.5–1.5
Sensors accel / gyro / mag / ambient light / proximity $1–3
Mechanical chassis, frame, sealing, buttons, brackets $15–30
Thermal graphite / heat spreader $1–4
OS AOSP / custom Android, hardened (verified boot, TEE, SELinux enforcing) —
Bottom-up sum PCB/FPC/connectors still uncosted ≈$157–260
Target complete hardware BOM @10k units (pre-2026-memory-surge; see §4) ≈$170–220

* Security caveat (os.md §2): ARM MTE unconfirmed on the 7 Gen 4 — “disqualifying on its own” for our GrapheneOS-derived security spec — and no discrete secure element in the BOM yet (StrongBox/Weaver). Verify both with the ODM before locking the SoC. The gap between the sum row and the target row is the ODM negotiation (§5).

0. The tell in the FCC filing

  • 2013 promise: “a fair, repairable phone.” 2025 reality, hiding in the public record: the Fairphone 6’s antenna report is authored by T2 Mobile (Shanghai) — TCL’s ODM arm — measured at TCL’s Ningbo lab. TCL-style part number: BQA6CT0A15C0.
  • Thesis: nobody builds a phone from scratch — not even Fairphone. You enter at one of four altitudes (§6). This post walks the ladder with real photos, part numbers, and a real BOM.
  • Why we can know: a US launch dumps its guts into the public record — 160 documents, 459 MB, labeled antenna maps, naked-board photos. That filing + two teardowns + our own spec attempt = this post.

1. What’s inside a modern phone

Specimen: Fairphone (Gen. 6) — €549, IP55, top iFixit repairability marks (10/10 is confirmed for the Fairphone 5; I have not verified the Gen-6 score myself).

  • Module map: mainboard (top 40%) · battery (middle) · daughterboard + speaker/vibe + USB-C module (bottom) · display · camera cover over two rear cameras, a ToF sensor, front camera, earpiece.
  • One screw type for the whole phone (T5 Torx, ~26 screws). Battery swap ≈ 2 min, screen ≈ 5 min; no adhesive except the button-flex pads.
  • Battery trick: bare pouch (4415 mAh, 3.91 V nom / 4.50 V limit, cell code 1ICP6/61/67) glued to a stamped-steel carrier with screw ears — a floppy pouch becomes a screw-down part, no plastic shell.
  • Three interconnect classes, chosen by who breaks the joint: B2B connectors → customer-swapped parts (battery, display, cameras, earpiece); pogo/spring contacts → technician-swapped parts (buttons, fingerprint, NFC, antennas, speaker, USB-C); coax → antennas (6+ MHF/IPEX receptacles on the mainboard; 3 colour-coded runs, silkscreened WHITE/RED/BLACK, to the daughterboard).
  • The mainboard has zero screws — the camera cover’s foam pads preload it onto pogo pins. And the third rear “camera” is a lie: it’s the ToF sensor.
  • Cost of repairability: IP55 not IP68, 9.6 mm thick, USB 2.0.

2. The silicon reality: you don’t pick chips, you pick a platform

  • Under the shields, a Qualcomm solar system: Snapdragon 7s Gen 3 (SM7635) with LPDDR5 stacked on top; around it the mandatory companion kit — SDR735 RF transceiver · PM7550 + PM8550VS PMICs · WCN6755 Wi-Fi 6E/BT · WCD937B audio codec; Micron UFS 3.1 beside.
  • The modem is not a chip you choose — it’s in the SoC. The Quectel/SIMCom modules beginners (us included, §3) reach for pair only with non-cellular processors.
  • What is chosen per design: the RF front-end — one Qualcomm QPM PA module, two PAMiD/receive modules (Skyworks-style S55643-51), tuners, switches — all dictated by the band plan.
  • 11 antennas + NFC in a €549 mid-ranger: 8 cellular (n41 and n77/78 each need four — 4×4 MIMO/SRS), 3 Wi-Fi/BT IFAs, one 40.7 × 29.15 mm NFC loop; all laser-structured onto plastic around a metal core (hence the plastic-overmoulded frame).
  • Even SAR is inherited: Qualcomm Smart Transmit power tables live in the modem’s filesystem. You don’t build this; you receive it.
  • Why you can buy a PC CPU but not a phone SoC: PCs standardised OS↔hardware discovery (UEFI/ACPI), so any OS boots any board and the CPU is a retail commodity. Phones didn’t — every SoC+board needs a bespoke BSP, so the chip is useless without it (gray-market Snapdragons on AliExpress prove it). Rockchip/Allwinner are the permissive end — which is exactly why §6’s rung 3 exists. Full table: SKR_learnings.md.

3. Our attempt: the spec sheet we wrote before we knew better

  • Written before any teardown: 21 sections, SoC to sealing (custom_phone_design_decision_summary.md).
  • Two reference phones inspired it: Fairphone 6 (repairability template) and the Jolla Phone — Sailfish OS, privacy switch, replaceable 5450 mAh battery, assembled in Finland, €649–749, launching October 2026; proof a Dimensity 7100 mid-ranger is enough and a tiny (ex-Nokia MeeGo) team can ship.
  • Our picks vs. the phone we tore down (costs live in the top table):
Subsystem Our pick Fairphone 6
SoC Snapdragon 7 Gen 4 7s Gen 3 — one gen older
RAM / storage 12 GB LPDDR5X / 256 GB UFS 4.0 8 GB LPDDR5 / UFS 3.1
Display 6.36” 120 Hz AMOLED 6.31” LTPO, 10–120 Hz
Main camera Sony LYTIA 808, 50 MP, OIS LYTIA 700C
Front camera ISOCELL 3LU, 12 MP AF 32 MP KD1
Battery 6000 mAh Si-C, removable 4415 mAh removable
Biometrics Power-button fingerprint (Goodix) same approach
SIM eSIM-only nano-SIM + eSIM + µSD
Charging 45 W USB-C PD 30 W, USB 2.0
Haptics LRA coin ERM — a documented FP6 cost-cut
  • Got right before the teardown: removable battery, button fingerprint, modular ambitions, mid-range Snapdragon.
  • Got wrong: a whole “pick a modem module” section (Quectel/SIMCom/Cat-1 bis) — meaningless on a Snapdragon phone; the modem is on-die and the real work is RFFE + an 8+3+NFC antenna system (§2). Spec §7 rewritten.
  • Voted against by both references: our eSIM-only line (FP6: nano+eSIM+µSD; Jolla: dual nano, no eSIM). Flagged for revisit.
  • Still open, honestly: RFFE, antennas, PMIC, Wi-Fi/BT, NFC, audio, haptics, thermal, sealing, BSP, certification — plus the two security-hardware gaps (os.md §2): MTE unconfirmed on 7 Gen 4, no secure element.

4. The money: BOM, royalties, and the certification wall

  • Bottom-up sum: ≈$157–260, PCB/FPC uncosted (decision summary’s own total: $159–267). The $170–220 target is not the sum — the gap is the ODM negotiation. Sanity check via Fairphone spares: battery €39.95 · display €89.95 · USB-C €19.95 · camera €69.95.
  • The 2026 memory surge already broke it: TrendForce (May 2026) — LPDDR5X contract prices +78–83% in 2Q26 (~$10/GB → ~$20/GB). Realistic now: 12 GB ≈ $40–60, 256 GB UFS ≈ $25–40 → component BOM ~$225–370; landed @10k (assembly $8–15 + tooling amort $10–20 + cert amort $10–25) ~$255–430. Memory, not the SoC, is the biggest line.
  • The royalty stack nobody puts in a launch deck: buying the chip ≠ licensing the patents (Qualcomm’s “no license, no chips” splits the two contracts). Cellular SEPs attach to the device: Qualcomm 3.25% of selling price (base capped at $400 → ≤~$13) · Nokia ≤€3 · Ericsson $2.50–5 · Huawei ≤$2.50 · InterDigital ~$1–2 → ~$20–25/device, plus BT SIG (~$10k/product), Wi-Fi Alliance, HEVC (~$1–2; AV1 free). Budget ~$25–35/device. Contract nuance: white-label → ODM is licensee of record; semi-custom → the brand is liable. Put it in the contract.
  • Certification wall, with numbers: enclosure tooling $50–150k; global cert stack (FCC + CE/RED + BIS + PTCRB/GCF, plus CTS/VTS if you ship GMS) ~$100–250k per model → $10–25/unit @10k. Scale: FP6’s FCC campaign = 160 exhibits from one lab; SAR ~40 docs; n77/78 runs 8 parts. New since most write-ups: EN 18031 (RED cybersecurity) mandatory in the EU since 1 Aug 2025 — FP6’s DoC already cites it.
  • Software is a parallel BOM with payroll: BSP + 8 years of updates = a staffed team. Google apps: small brands don’t sign a MADA directly — path runs via a Google-authorized ODM/3PL + CTS/GTS/VTS + (since the 2018 EU ruling) a per-device EEA fee. De-Googled with commercial support = Murena (the €599 FP6 /e/OS SKU; also Teracube, Volla, SHIFT). Decide GMS vs. de-Googled before the BSP contract — it forks the plan.

5. The ecosystem: who actually builds phones (and how you’d buy in)

5.1 The ODM pyramid — who takes your call

  • ODMs design and build most of the world’s phones; brands do spec, story and distribution. The FP6’s actual engineer is T2 Mobile (TCL) (§0). Qualcomm/MediaTek reference designs (QRD) are the starting point for everything.
Tier Who Typical MOQ Track record
1 — giants Huaqin, Wingtech, Longcheer (together ~70–76% of global ODM smartphone shipments, 2019–2023 counts), BYD Electronic, T2 Mobile, FIH (Foxconn) 100k+ Samsung A-series, Xiaomi, Honor, HMD; BYD built the Nothing Phone (1); T2 built the FP6
2 — mid-size Tinno (owns Wiko), Sprocomm (HMD/Nokia), Arima (built the Fairphone 3), Emdoor ~10k–50k the realistic band for a 10k-unit brand
3 — Shenzhen “public model” (公模) houses via Alibaba/Made-in-China; behind Unihertz, Teracube, Ulefone, Doogee ~500–1k rebrand; ≥3k with hardware changes Snapdragon 4 / Helio / Unisoc class only
  • The hype brands are this pyramid + marketing: OnePlus 1 = Oppo’s factories with a community story; Nothing Phone (1) = a BYD design with a transparent back. Below the top-10 OEMs, nobody escapes the pyramid — you pick a tier and a story.
  • Component tier (you specify, the ODM buys): BOE/TCL-CSOT/Tianma (displays) · ATL/Sunwoda (batteries) · Sunny Optical/O-Film (cameras) · Skyworks/Qorvo/Murata (RFFE) · AAC/Goertek (acoustics/haptics) — tier names as I understand them, not independently confirmed.

5.2 How you engage — there is no shop

  • Tier 1–2 publish no catalogue (checked: Tinno’s and Sprocomm’s “product” pages are category names + a phone number — reference designs embed NDA’d Qualcomm/MTK material). The menu is a sales process you qualify for: company brief + volume forecast → NDA → roadmap deck → samples → RFQ with your deltas → quote. Tier 1 politely declines 10k-unit brands.
  • Public windows: trade shows (MWC, Global Sources HK, Canton Fair) and Tier-3 Alibaba listings — the only browsable specs/MOQ/prices (rebrand MOQ ~500–1k, ≥3k with hardware changes, per Alibaba’s own buying guide).
  • Getting replies, in order: named BD person on LinkedIn · trade-show booth (leave with WeChat contacts) · Alibaba “send inquiry” · Shenzhen sourcing agent · chip-vendor intro (needs credible volume) · Indian EMS (Dixon, Optiemus — built Nothing Phone (2a)) if “Make in India” is the story.
  • Quote vocabulary: MOQ (smallest run they’ll accept) · NRE (one-time engineering/ tooling fee for your changes) · FOB unit price (falls with volume) · deltas (your changes vs. their reference design — each one costs NRE and raises MOQ, so the art is a short list) · 30–50% deposit · tooling/ID/firmware ownership (make it yours).
  • The BOM’s real job: RFQ annex, cost yardstick and requirements record — not a shopping list. At 10k units you never hold a PO with Qualcomm; the ODM’s platform catalogue is the SoC menu (SKR_learnings.md). BOM lines split into spec (you dictate: display, cameras, battery cell, enclosure, secure element) and menu (the platform bundle: SoC + PMIC + RFFE + companion kit + qualified memory combos).

5.3 The open-ish corner

  • Pine64 (PinePhone), Purism (Librem 5), Fairphone, SHIFT, Teracube, Light Phone, Punkt, Jolla/Sailfish, /e/OS & Murena, LineageOS, postmarketOS.
  • Jolla, the counter-example to the Qualcomm default: MediaTek SoC + Sailfish OS + Finnish assembly — an alternative stack (no GMS) alive 12+ years on niche volumes. fccid.io detail: Jolla’s entire FCC history is one 2015 tablet filing — no Jolla phone was ever FCC-certified; the 2026 phone ships EU/UK/CH/NO only. Who builds Jolla’s hardware I could not establish.
  • The Sailfish nuance (os.md): Jolla’s business is OEM-licensing the OS — it runs on a normal Android BSP via libhybris; core open, but Silica UI and Android AppSupport proprietary. Our OS pick excluded it (“fails open source”) for AOSP + optional /e/OS (Murena) SKU — irony: the values-inspiration company ships a part-closed OS. GrapheneOS’s hardware requirements are our security spec instead (MTE + secure element = the two real gaps).
  • Sailfish pricing: ~€50 one-off consumer licence (AppSupport, Exchange, VoLTE); ~€5/month subscription from Sailfish 5 (perpetual option retained); OEM royalty negotiated, unpublished. It buys a differentiated UI — not a way around the BSP.

6. The four entry paths

  1. White-label / rebrand — ODM catalogue phone, your logo + firmware skin. ~$50k–200k, MOQ 0.5–10k (Alibaba public-model tier starts ~500–1k), ~6 months. You own brand + distribution. (Punkt, early Light-Phone-ish.)
  2. Semi-custom ODM — your ID/mechanical on reference-design electronics; ODM does RF, antennas, certification. The Fairphone route — and ours. ~$1–5M, MOQ 10k+, 12–24 months.
    • Rung 2½ — Android smart-module route: the one place “own board” is purchasable at 1–1,000 units: carrier board + QCM6490-class module (Quectel SG560D, Fibocom SC171, Thundercomm C6490; RB3 Gen 2 kit ~$399). Module vendor holds the Qualcomm license, ships the Android BSP, module is RF pre-certified (FCC/CE, often PTCRB) — collapses most of §4’s cert wall for prototypes. Trade: last-gen silicon, ~$100+ module, thick product.
  3. Linux-phone route — non-Qualcomm AP (i.MX/Rockchip) + modem module (Quectel/Broadmobi) + community OS. No Qualcomm NDA, genuinely open — but 2016-era performance, no GMS. (PinePhone ~$150 BOM-class; Librem 5 — $2M+ and years late.) Where our original Quectel/Cat-1 bis idea actually lives.
  4. From scratch — own board, RF, antennas, cert program. Nobody outside the top ~10 OEMs; even they lean on Qualcomm reference designs.

Our 10k-unit phone lands on path 2, path 3 as the ideological fallback.

7. Feasibility verdict

  • Yes, you can “build a phone” — for the rung-1–3 definitions of build. Capital: rung 1 low six figures · rung 2 low seven figures · rung 3 seven figures + a community · rung 4 don’t.
  • Survivors are values-based niches: Fairphone (repairability + EU regulation tailwind), Light Phone & Punkt (minimalism), Jolla (pivoted to B2B licensing; consumer phone returning October 2026). Graveyard: Essential — $330M raised, dead in 2.5 years.
  • Rung-1 fingerprint, in our own folder (lightphone_specs.md): Light Phone III = Qualcomm SM4450, Light Flip = MediaTek MT8873 — yet both share 6 GB/128 GB, 50 MP sensor, 1800 mAh, IP54. Two SoC vendors, identical supporting spec: public-model sourcing with a custom OS on top.
  • You cannot out-spec BBK/Samsung/Apple at any realistic volume; you can out-value them (repairability, privacy, minimalism).
  • Closing: the FCC filing that started this post is the beginner’s best textbook — every US phone’s guts are public at fccid.io. Go read one. (Just not the Jolla’s — the EU-only phone has never crossed the FCC’s desk.)

8. Resources & further reading

Working notes, BOM decision log, FCC and teardown analysis: skr3178/O-Phone.