Capacitive Touch Key FPC SMT Assembly

This is a typical consumer-electronics capacitive touch-key flexible PCBA. On a 55×19 mm black polyimide flex, four square copper sensing pads are laid out in a 2×2 array — no mechanical contacts at all. A finger is detected through acrylic, glass, plastic or even solid-wood panels. The board plugs directly into the host FPC socket through its ENIG gold-finger tail, and the back can be pre-laminated with 3M transfer adhesive, so the end customer simply peels, aligns and sticks.

Typical use cases include **smart wearables, smart lighting, beauty devices, hidden home-appliance control panels and medical-device keypads**. Juehui Weiye Circuit delivers this class of touch FPC as a one-stop PCBA service: FPC fabrication + touch-IC SMT + adhesive lamination, from as low as 1 piece, with prototypes turned around in 3–5 days.

Specifications

Product family : Capacitive Touch Key FPC (Touch Pad Flex)

Board size : 55 × 19 mm, custom outline, laser-routed

Layers : 1-layer flex, polyimide (PI) substrate

Coverlay : Black matte PI coverlay, white legend

Surface finish : ENIG — immersion gold on contact fingers & per-channel shield dots

Touch channels : 4 × square copper sensing pads, 2×2 array

Shield design : 1 round gold-plated ground / shield dot at the center of each pad

Connector end : ENIG gold-finger tail, plugs into host ZIF / LIF FPC socket

Finger pitch : 0.3 mm / 0.5 mm (matched to customer's mainboard socket)

Stiffener : Local FR-4 / PI stiffener behind the gold-finger tail

SMD on reference build : None (pure flex); touch IC can be SMT on a tail island on request

Optional on-board IC : TTP223 / GT911-class capacitive touch controller + passives

Substrate thickness : 25 / 50 µm PI with 12–18 µm copper

Coverlay thickness : 25 µm PI coverlay + adhesive

Panel penetration : Through 1–4 mm acrylic / glass; up to 8–10 mm wood / stone veneer

Back adhesive : 3M 467MP / 468MP transfer adhesive with die-cut release liner (optional)

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

Operating temperature : −20 °C to +70 °C (consumer grade)

MOQ : From 1 pc for prototyping; 100+ pcs for pilot production

Lead time : Prototype 3–5 days · Mass production 10–15 days

Compliance : RoHS / REACH, ISO 9001 workflow

Process Highlights

- High-precision sensing-pad routing — copper pad geometry, guard-ring spacing and ground-copper clearance are all designed for production consistency, eliminating phantom touches and cross-key crosstalk.

- ENIG gold fingers — immersion gold on the tail prevents oxidation over repeated mating and guarantees flat coplanarity for stable contact with the host ZIF socket.

- Local stiffener — an FR-4 / PI stiffener is bonded behind the gold-finger end to prevent the flex from folding or being inserted backward during plug-in, improving final-assembly yield.

- Black coverlay & DFM review — the matte black coverlay is invisible behind decorative panels. Before release, our engineers review pad-to-ground clearance, ESD guarding and adhesive lay-up to avoid rework in mass production.

- Optional touch-IC SMT — if a controlled output is required, TTP223 / GT911-class touch ICs, bypass capacitors and LED indicators can be SMT-assembled on a small tail island and delivered after full functional testing.

Applications

Smart wearables · Smart-lighting touch dimmers and ambient-lamp panels · Beauty devices, facial cleansing brushes and skin-care tools · Aroma diffusers and humidifiers · Hood, washer and air-purifier hidden control panels · Medical bedside nurse-call stations and dental-equipment control panels · Automotive steering-wheel touch keys and sunroof control panels · Kids' appliances and smart-mirror panels.

Why Choose Juehui Weiye Circuit

Juehui Weiye Circuit specializes in one-stop, low-to-medium-volume FPC + PCBA customization: flex fabrication, SMT assembly, component sourcing, functional testing and adhesive lamination, all under one roof. Our standard capabilities include:

- 2-layer / 4-layer FPC, PI / PET substrate options

- Black / white / yellow coverlay with customer-specific silkscreen legend

- ENIG / OSP / immersion-silver surface finishes

- PI / FR-4 / stainless-steel / PET stiffener options

- Touch-IC, LED and passive SMT on the tail island

- 3M transfer-adhesive lamination with die-cut release liner

- Up to 22-layer / 2-stage HDI rigid boards and rigid-flex assemblies for the rest of your system

- Prototype from 1 pc, with a dedicated engineer running 1-on-1 DFM review during NPI

FAQ

Q1. Do you only fabricate the flex, or can you also SMT the touch IC?

Both. This reference build ships as a pure flex (gold fingers plug directly into the host), but we routinely assemble TTP223 / GT911-class touch controllers, bypass capacitors and LED indicators on a small tail island — delivered as a fully tested PCBA ready to plug into your mainboard.

Q2. How thick a panel can the touch pads work through?

Typical design target is 1–4 mm acrylic or glass; solid wood or stone veneer can reach 8–10 mm, tuned by sensing-pad size and panel dielectric constant. Send us your panel material and thickness, and our engineer will size the pads.

Q3. Can the number and shape of the touch keys be changed?

Yes. Key count, shape (square, round, slider, rotary wheel), spacing and guard-ring routing are all built to your Gerber. The pictured 4-key 2×2 layout is just one reference — single-key sliders, 6-key keypads and rotary wheels are all standard work.

Q4. Do you apply the 3M adhesive on the back?

Yes. We can laminate 3M 467MP / 468MP or equivalent transfer adhesive on the back, with die-cut release liner, so your assembly team simply peels off the liner and aligns the panel.

Q5. What files do you need to quote?

FPC Gerber + drill file + fabrication drawing (coverlay, stiffener and adhesive layers). If touch-IC SMT is required, also send the SMT centroid file and BOM.

Ordering Information

To get started, please provide: **PCB Gerber files, BOM, pick-and-place (centroid) file, and functional test specification**. We will return a one-stop quotation and production assessment covering PCB fabrication, SMT assembly and through-hole assembly. Material, layer count, surface finish and component sourcing can all be adjusted to your project.

📞 Tel: +86 189‑2464‑6170

📧 E‑mail: szjhpcb@vip.126.com

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