Polyester PCB

Polyester PCB is Ultra-Low-Cost Flex Circuits for Disposable Sensors, Membrane Switches & LED Light-Strips

What Is a Polyester PCB?

A polyester PCB—often called PET flex—uses polyethylene-terephthalate film as the dielectric instead of polyimide.
Typical construction:

Electrodeposited (ED) copper 12 µm or printed silver ink
PET film 50 – 250 µm (εʀ ≈ 3.2, Df ≈ 0.018)
Acrylic adhesive (for copper-clad versions)

Because PET softens near 105 °C, PET flex circuits are screen-printed or chemically etched at low temperatures and finished with low-temp Sn-Bi solder, crimp contacts, or conductive adhesive.

highpcb is one of the largest Flex PCB manufacturing company in China, Click on the link for more information.

Why Pick Polyester Over Polyimide?

50 – 60 % lower laminate cost

Ideal for price-sensitive or disposable devices

Transparent & printable

Back-lit keypads, capacitive touch foils, decorative graphics

Roll-to-roll manufacturable

Tens of metres produced per minute → unbeatable unit cost

High tensile elongation (~120 %)

Survives snap-fit assembly without cracking

Excellent dimensional stability

±0.1 mm per metre at 23 °C / 50 % RH—flat key-matrix domes

highpcb is one of the largest Polycarbonate PCB Manufacturing Company in China, Click on the link for more information.

highpcb is one of the largest PCB assembly factories in China, click here to see more.

Key Limitations & How to Work Around Them

Limitation	Mitigation Strategy
Reflow-incompatible (Tm ≈ 255 °C, softens > 110 °C)	Use Sn-42 Bi-57 Ag-1 paste @ 175 °C peak; hot-bar, ACF, or crimp terminals
Lower peel strength vs. PI	Rough-en copper with micro-etch; use RA copper if space allows
Moisture & UV sensitivity	Add PET-based white overlay or UV-block varnish for outdoor use
Acrylic adhesive cold-flow	Keep continuous operating temp < 85 °C; use stiffeners under SMT parts

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Typical Applications for PET Flex

Segment	Examples
Human–machine interface	Membrane-switch matrices, capacitive slider foils, back-lit touch keys
Disposable medical	Blood-glucose test strips, ECG patches, drug-delivery pump inserts
LED lighting	Edge-lit acrylic panels, string LEDs for signage, holiday lights
RFID & NFC	Antenna inlays for logistics tags, contactless payment cards
Low-power sensors	Force-sensing resistors, printed temperature/humidity arrays

PET Flex Stack-Up Choices

1 Screen-Printed Silver Ink (Single-Conductor Layer)

Protective UV varnish

Printed Ag conductor 8–12 µm

PET film 125 µm (clear)

Adhesive transfer tape (optional)

Backer paper / graphic overlay

Most economical—down to US $0.02 / cm² in volume.

2 Copper-Clad PET (Double-Sided Low-Cost Circuit)

Imm Sn-Bi 2 µm finish

Coverlay: PET 25 µm + PSA

Cu 12 µm — Top tracks

Acrylic adhesive 15 µm

PET core 50 µm

Acrylic adhesive 15 µm

Cu 12 µm — Bottom tracks

Coverlay PET 25 µm

Supports 0.25 mm-pitch ICs & small LEDs.

Manufacturing Flow (Roll-to-Roll & Sheet-Fed)

Step	Silver-Printed PET	Copper-Clad PET
Film clean & corona treat	✔	✔
Conductor formation	Screen print Ag; dry 120 °C × 5 min	Photo-image; etch cupric chloride
Die-punch registration holes	±0.05 mm	±0.05 mm
Coverlay / overlay lamination	UV-curing acrylic	Pressure-sensitive adhesive
Kiss-cut / laser-cut outline	Steel-rule die (200 hits/min)	CO₂ laser ±30 µm
Low-temp solder / hot-bar / ACF	175 °C Sn-Bi; 180 °C ACF	175 °C Sn-Bi; selective-solder mask
100 % E-test	Capacitive or flying-probe	Flying-probe ≤200 pts/s

Roll-width up to 350 mm; sheet panels 510 × 610 mm available for copper versions.

Design Guidelines for PET Flex

Feature	Recommended Value
Min trace / gap (Ag print)	200 µm / 200 µm
Min trace / gap (Cu etch)	100 µm / 100 µm
Min plated through-hole	Avoid—use jumpers or rivets
Static bend radius	≥ 10 × total thickness
Dynamic flexing	Not recommended; choose PI if cycles > 50 k
Pad-to-bend distance	≥ 2 mm
Stiffener thickness	FR-4 or PI 0.2–0.3 mm under SMT
Current vs. trace width	500 mA → 1 mm (Cu 12 µm); 200 mA → 1 mm (Ag 10 µm)

LED strip tip: Use white PET overlay to boost luminous efficiency by > 20 % and protect copper from sulphur tarnish.

Reliability & Test Matrix

Test	Spec	Typical PET Result
Solder dip 180 °C Sn-Bi, 10 s × 3	IPC-TM-650 2.4.13	No blister / no pad-lift
Static bend 5 × t, 1000 cycles	IEC 60068-2-21	ΔR < 3 %
Humidity 85 °C / 85 % RH, 168 h	IPC-TM-650 2.6.3.5	ΔR < 5 %, IR > 100 MΩ
Adhesive cold-flow @ 85 °C, 100 h	MIL-P-50884	Edge creep < 0.3 mm
UV ageing 500 h	ASTM G154 UV-A	ΔR < 5 %, slight yellowing

Cost Drivers & Optimisation

Driver	Cost Impact	Optimisation Tip
Roll-to-roll silver thickness ↑	+US $0.03 / µm per m²	Print 8–10 µm + carbon pad on switch contacts
Coverlay laser area ↑	+US $0.10 / cm²	Gang large windows; use die-cut PSA
Double-sided Cu PET	×1.8 vs single-Ag print	Re-route to single-sided + jumpers if possible
Selective stiffener lam.	+US $25 setup	Use kiss-cut FR-4 self-attach stiffeners
ENIG on Cu PET	×1.4 vs Sn-Bi	Choose Imm SnBi or OSP unless gold needed

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Why Order Polyester PCBs from HighPCB?

Dual production lines – roll-to-roll screen printing for high-volume silver circuits & sheet-fed LDI for fine-pitch copper PET.
Clean-room corona treatment – ensures peel strength > 1.2 N cm⁻¹ even after 85/85 humidity.
Rapid DFM & cost-down advice – panel utilisation, ink-coverage map, stiffener optimisation in 48 h.
Fast lead-times: 3-day silver prototypes (1-layer), 7-day Cu PET (double-sided).
Add-on services: white overlay printing, hot-bar flex-to-rigid attach, Sn-Bi selective wave, 100 % flying-probe & switch-matrix functional test.

Need a flex circuit that hits aggressive cost targets without sacrificing reliability?
Request your instant polyester PCB quotation from HighPCB today—our PET flex specialists will optimise the material, trace geometry, and roll-to-roll process to deliver the lowest total cost for your membrane keypad, disposable sensor, or LED lighting project.