2. Finished FPC Specifications

Parameter	Specification
Layer count	2 layers
Base material	Polyimide (SF202), 50 µm
Copper type	RA copper (rolled annealed)
Finished copper weight	0.6 oz (≈21 µm)
Total board thickness	0.118 mm
Minimum hole size	0.1 mm
Surface finish	ENEPIG (Ni/Pd/Au)
Solder mask	Green liquid photoimageable ink
Silkscreen	None
Panel size	100 mm × 100 mm (1 piece)

3. Copper Foil Types – Why RA Copper for Dynamic Flex

Copper is the most common conductor material for flexible circuits. This applies to all flexible circuit designs, including standard dynamic flex applications and Transparent Flexible Printed Circuit FPC On PET Substrate. Two types of copper foil are available: ED copper and RA copper. This product uses RA copper for superior dynamic flex performance.

 

 

3.1 ED Copper (Electro-Deposited)

ED copper is produced by electrolytic deposition, similar to rigid PCB copper foil. It has a treated (rough) surface on one side for better adhesion to the base material. The key characteristic of ED copper is its vertical grain structure (see illustration below), which results from the electrolytic process. This vertical structure gives ED copper relatively low ductility, making it unsuitable for dynamic (moving) applications.

Common thicknesses for flexible circuits: 17.5, 35, 70, 105, 175 μm (0.5, 1, 2, 3, 5 oz.)

3.2 RA Copper (Rolled Annealed) – Used in This FPC

RA copper is produced by melting electrolytic cathode copper, casting into ingots, hot-rolling, milling, then cold-rolling and annealing to the desired thickness. Unlike ED copper, RA copper has a horizontal grain structure (see illustration below). This horizontal structure provides much higher flexibility and better flex-life endurance, making RA copper the only choice for dynamic applications.

Disadvantage: The bonding surface of RA copper is fairly smooth, resulting in lower natural adhesion. However, adhesion can be enhanced with an electrolytic copper flash without degrading flex characteristics.

Common thicknesses for flexible circuits: 17.5, 35, 70, 105, 175 μm (0.5, 1, 2, 3, 5 oz.)

This FPC uses RA copper with 0.6 oz (≈21 µm) – a standard thickness within the 0.5–5 oz range.

 

4. Base Material Advantages – SF202 Polyimide for This FPC

This 2‑layer FPC uses SF202 polyimide as the base substrate – a double‑side, adhesiveless flexible copper clad laminate. The adhesiveless construction (copper directly bonded to polyimide) provides three key benefits for the finished PCB:

Thinner overall build – contributes to the 0.118 mm total thickness.

Higher heat resistance – supports lead‑free soldering without delamination.

Better dynamic flex life – outperforms adhesive‑based materials in moving applications.

4.1 Key Properties of SF202 Substrate

Soldering reliability – withstands assembly temperatures.

Dimensional stability – minimal expansion/shrinkage during etching and lamination.

Chemical resistance – resists etching, plating, and cleaning chemicals.

Halogen‑free and UL94 VTM‑0 flame rating.

RoHS compliant (no Pb, Hg, Cd, Cr6+, PBB, PBDE).

4.2 Typical End‑Use Applications

This SF202‑based FPC is suitable for computers, mobile phones, digital cameras, flat panel displays, instrumentation, and automotive electronics.

 

5. Purchasing Information (SF202 Rolls)

SF202 is supplied in rolls. Standard dimensions are listed below. Other sizes are available upon request.

Parameter	Standard Options
Roll width	250+2/-0 mm or 500+2/-0 mm
Roll length	50+1/-0 m or 100+2/-0 m
Custom sizes	Available upon request

 

6.Storage Condition (SF202 Rolls)

To maintain performance, store SF202 as follows:

Environment: Dry, indoor area, no corrosive gases.

Temperature: 5°C to 35°C

Humidity: ≤75%

Shelf life: 1 year when stored in original packaging under above conditions.

 

7. Product Code Description (Shengyi Adhesiveless FCCL Designation)

SF202 product code format: SF202 05 12 D T

Position	Meaning	Options
SF202	Product designation	Fixed
05	PI film thickness	05 = 12.5 µm, 08 = 20 µm
12	Copper foil thickness	12 = 12 µm, 18 = 18 µm
D	Double side?	D = double side; if not D, indicates other side copper thickness
T	Copper type	R = RA copper, T = RTF (reverse treated copper)

Example: SF202 05 12 D T = PI 12.5 µm, 12 µm copper both sides, double side, RTF.

This product uses RA copper (code R). The finished PCB uses 0.6 oz (≈21 µm) copper – thicker than standard 12/18 µm, available as a custom order.

 

8.Data sheet

 

Test Item	Test Method	Unit	Standard*	Typical ValueSF202 0512DT
Peel Strength 90°	IPC-TM-650, No.2.4.9 Method AMethod C	N/mm	≥0.525≥0.525	1.21.2
Thermal Stress	IPC-TM-650, No.2.4.13	-	Pass	Pass
Dimensional Stability	IPC-TM-650, No.2.2.4 Method B	%	±0.2	MD: 0.01TD: 0
Chemical Resistance	IPC-TM-650, No.2.3.2	%	≥80	85
Moisture Absorption	IPC-TM-650, No.2.6.2	%	≤2	1.3
Volume Resistivity	IPC-TM-650, No.2.5.17	MΩ·cm	≥10⁶	4.8×10⁸
Surface Resistance	IPC-TM-650, No.2.5.17	MΩ	≥10⁵	1.2×10⁶
Dielectric Constant (1GHz)	IPC-TM-650, No.2.5.5.9	-	-	3.2
Dissipation Factor (1GHz)	IPC-TM-650, No.2.5.5.9	-	-	0.007
MIT Folding Endurance	R0.38×4.9N, with cvl	Times	-	>2000
Dielectric Strength	IPC-TM-650, No.2.5.6.2	V/μm	≥80	150

 

 

9. Summary

This 2-layer, 0.118mm thick FPC combines the benefits of RA copper (superior flex life, horizontal grain structure), ENEPIG (flat, solderable, wire-bondable surface), and liquid solder mask (fine resolution for 0.1 mm features). Built on SF202 adhesiveless polyimide, it offers soldering reliability, dimensional stability, chemical resistance, UL94 VTM-0, and RoHS compliance. SF202 is available in rolls (250/500 mm width, 50/100 m length) with one-year shelf life under proper storage. The product code (e.g., SF202 05 12 D R) specifies PI thickness, copper thickness, double side, and RA copper. This FPC is ideal for computers, mobile phones, digital cameras, automotive electronics, and other compact, dynamic flex applications.