Standard SMT lines are designed for rigid FR4 boards. Flex PCBs introduce three challenges that most contract manufacturers underestimate: the substrate deflects under vacuum conveyor rails, solder paste deposits shift on unsupported polyimide, and thermal mass differences between flex and rigid stiffener sections require custom reflow profiles. FlexiPCB's SMT assembly operation uses hard tooling plates and custom vacuum carriers to hold flex panels flat to within 0.1mm across the entire board surface — the same flatness tolerance required for reliable 0.3mm pitch BGA placement. Our engineers have processed over 12 years of flex-specific SMT builds, which means we have reflow profiles for common polyimide thicknesses (50µm, 75µm, 125µm) already benchmarked, not guessed. Every solder paste deposit is measured by SPI before placement — a step that catches bridging and insufficient-volume defects before they become costly rework on a bent, unrepairable flex circuit.
Continuous glucose monitors, ECG patches, and hearing aids require miniaturized SMT assemblies on thin flex substrates. IPC-A-610 Class 3 workmanship ensures zero-defect results for patient-contact electronics.
ADAS camera flex circuits, LiDAR sensor interconnects, and in-cabin display modules demand 0.4mm pitch BGA assembly with IATF 16949 traceability and AEC-Q100 component qualification.
Foldable phone hinges, smartwatch bodies, and AR/VR headset modules require 01005 passives and fine-pitch IC placement on double-layer flex — assembled to IPC Class 2 with cycle-life testing on flex joints.
Wireless vibration, temperature, and pressure sensors package entire sensor electronics onto single-layer flex — low-profile, conformal, and ready to mount in tight equipment cavities without brackets.
Avionics flex assemblies and satellite interconnects require AS9100-aligned workmanship, serialized traceability, and X-ray verification of all solder joints — including hidden BGA balls under shielded enclosures.
Before quoting, our engineers review your Gerbers for SMT-specific risks on flex: insufficient solder mask clearance, component placement near bend zones, and stiffener-to-flex thermal transitions that can cause solder cracking. We model the reflow profile against your flex thickness before a single board is placed.
We source components from Digi-Key, Mouser, Arrow, and other authorized distributors. Every reel is verified for part number, date code, and moisture sensitivity level (MSL) before entering the SMT line. MSL-sensitive packages are baked to J-STD-033 requirements before placement.
Solder paste is applied through laser-cut stainless stencils with apertures optimized for each component's paste volume requirements. A 3D SPI scanner measures every deposit — volume, height, area, and position — before any component is placed. Boards outside ±15% paste volume specification are reprinted, not assembled.
Flex panels are loaded into hard tooling carriers that support the full board surface. High-speed placement machines position components using vision alignment referenced to fiducial marks. Fine-pitch BGAs and QFNs are placed last with force-controlled heads at reduced speeds to prevent pad lifting on unsupported flex areas.
Boards travel through a nitrogen-atmosphere reflow oven using profiles benchmarked for the specific polyimide thickness. The slow ramp rate (1.5–2°C/s) prevents thermal shock to flex joints. Peak temperature and time-above-liquidus are monitored by thermocouples placed on representative flex and stiffener areas of the first article panel.
Post-reflow 3D AOI inspects every visible solder joint against IPC-A-610 accept/reject criteria. BGA and QFN joints are verified by X-ray imaging. ICT or flying-probe electrical test confirms connectivity and shorts. Boards are packaged in anti-static, humidity-controlled bags and shipped with full inspection reports.
We do not tape flex boards to backing plates and hope for the best. Every flex job runs on custom vacuum carriers matched to your panel dimensions, giving the consistent flatness that precision SMT stencil printing requires.
Solder paste inspection after reflow tells you what failed. SPI before placement prevents failures from reaching the oven. On flex boards where rework is expensive — sometimes impossible for embedded BGAs — catching a bad paste print before placing 200 components saves real money.
Polyimide conducts heat differently from FR4. Our engineers maintain a library of verified reflow profiles for standard flex thicknesses and stiffener configurations — so your first article board is not a reflow experiment.
Medical device and aerospace customers regularly specify Class 3 workmanship. Our assembly team holds IPC-A-610 CIS certification. Class 3 jobs include mandatory inspector sign-off at post-reflow AOI, X-ray review, and a final visual audit before packaging.
The more complete the package, the faster and cleaner the quote.
Gerber, drawing, or sample photos
BOM, stackup, and key materials
Quantity, target lead time, and application
Designed to help procurement and engineering move without extra loops.
DFM and manufacturability feedback
Quoted price, tooling, and lead time options
Testing and documentation plan
Send your drawing or Gerber, BOM, quantity forecast, application environment, and target lead time. Incomplete inputs slow quotation and increase assumptions.
Our engineers review risks first, then return pricing, lead time, and any DFM or sourcing concerns so you can compare options before release.
Yes. The same workflow supports prototype validation, pilot build, and volume release with traceability and testing requirements carried forward.
See how we handle solder paste inspection, fine-pitch placement, and reflow profiling on flexible circuits
Discover our complete range of flex PCB manufacturing and assembly services
