Custom FPC Sensor Module PCBA Assembly

This is a typical optical-sensor flexible PCBA for consumer electronics. On a 40×25 mm black polyimide flex, we assembled one RGB ambient-light LED, two IR phototransistors, four 0402 chip resistors, a board-to-board FPC connector and two exposed gold spring-contact pads. The flex tail is routed into a custom irregular shape to fit cramped internal enclosures, while the sensor island is backed by a steel stiffener so the optical window stays flat through reflow and final assembly.

Silkscreen `axi_0825 / E1v1-SENSOR` with clear IR / R / G / A polarity markers — ready to drop into wearables, TWS charging cases, smart-home appliances and handheld medical devices. Juehui Weiye Circuit delivers this class of flex as a one-stop package: flex fabrication + SMT assembly + functional test, from 1 prototype in 3–7 days.

Specifications

Product family ： FPC sensor module PCBA (flexible PCB + SMT assembly)

Board size ： 40 × 25 mm, custom outline, laser-routed

Layers ： 1-layer flex, polyimide substrate

Coverlay ： Black matte PI coverlay, white legend

Surface finish ： ENIG — immersion gold (ENEPIG on request)

Stiffener ： Stainless-steel / FR-4 stiffener bonded under sensor island

Ground pads ： 2 large exposed-gold EMI shield pads on the flex tail

Mounting holes ： 2 × Ø1.0 mm plated holes

B2B connector ： SMT, ~10–12 positions, 0.4 mm pitch

Spring contacts ： 2 exposed gold finger pads for pogo-pin docking

Optical devices ： 1 × RGB / ambient LED (ceramic package) + 2 × IR phototransistors

Passives ： 4 × 0402 / 0201 chip resistors

Smallest package ： 0201 / 0402

Solder ： SAC305 lead-free reflow, RoHS

Assembly side ： Single-sided SMT

Inspection ： SPI → Reflow → AOI; X-ray and 100% ICT available

Flex bend ： Static bend on delivery; recommended radius ≥ 6× thickness

MOQ ： From 1 pc prototype; 100+ for pilot production

Lead time ： Prototype 3–7 days · Mass production 12–18 days

Process Highlights

- Black matte coverlay — hides inner routing and blocks stray light from the IR/RGB sensor, matching premium consumer-device aesthetics.

- ENIG surface finish — flat coplanarity on contact fingers, spring pads and B2B lands; long shelf life and repeated-contact durability.

- Steel stiffener island — keeps the optical window flat through reflow and assembly, eliminating coplanarity drift that breaks sensor calibration.

- Fine-pitch SMT + full inspection — 0201/0402 passives, 0.4 mm-pitch connectors and optical die placed on SPI → reflow → AOI; X-ray and 100% ICT for production runs.

Applications

Smartwatch / wristband HR · SpO₂ · ambient light flexes · TWS earbud charging-case lid & wear detection · smartphone / tablet proximity & ALS · smart-home human-presence and daylight-harvest modules · handheld diagnostic pens, pulse-ox clips and bedside monitors · automotive cabin occupancy & steering-wheel grip · VR/AR headset proximity · industrial handheld terminals and night-vision optics.

Why OEMs Choose Juehui Weiye

Juehui Weiye Circuit is a Shenzhen-based one-stop PCBA partner for low-to-medium-volume custom builds. We run flex fabrication, SMT assembly, component sourcing, functional test and conformal coating under one roof:

- Rigid up to 22-layer / 2-stage HDI, back-drilled, resin-plugged, blind & buried vias

- 0.2 mm ultra-thin boards, 2 oz thick copper, selective ENIG up to 4 µm nickel

- BGA / QFN / 0201 fine-pitch assembly, IPC-A-610 Class 2 / Class 3

- Track record in medical, 5G communications, AI high-speed servers, automotive TBOX / eCall, aviation navigation and defense communications

- NPI from 1 pc, with a dedicated engineer running DFM review before quotation

FAQ

Q1. Can you fabricate the flex and assemble it in the same order?

Yes. This unit was built end-to-end: flex etch, coverlay, stiffener lamination, then SMT on the RGB LED, IR sensors, passives and connector. Send Gerber + BOM + centroid; we return a tested PCBA.

Q2. What is the minimum order?

Prototype runs start at 1 pc for design validation; pilot production at 50–500 pcs, scaling to 10k+ monthly. Most flex outlines are laser-routed — no hard tooling.

Q3. Do you support black coverlay and selective ENIG?

Yes. Black / white / yellow PI coverlay, immersion gold on selected contact pads only, and PI / FR-4 / stainless-steel / PET stiffeners are all standard.

Q4. How are optical sensors tested?

AOI confirms placement and joints, then a custom ICT / functional fixture drives the RGB LED and reads back the IR phototransistor — your calibration tolerance can be programmed into the outgoing test report.

Q5. What files do you need to quote?

Gerber (RS-274X) + drill file + pick-and-place + BOM (with manufacturer and P/N) + assembly drawing. If you only have a photo of a reference unit, send it — our engineer will help reverse-engineer a build spec.

Order Instructions

Please provide PCB Gerber files, BOM, component centroid coordinate files and functional‑test specifications. We will furnish one‑stop quotation and manufacturing evaluation covering PCB production, SMT assembly and through‑hole assembly. Adjustments to substrate material, layer count, surface finish and component‑sourcing schemes can be made on demand.

📞 Tel: +86 189‑2464‑6170

📧 E‑mail: szjhpcb@vip.126.com

🌐 Official Website: https://www.szjhpcba.com