A breakdown of a flexible circuit shows that it consists of 3 basic elements: copper foil, dielectric material and adhesive. Most of the manufacturing proceses, i.e. imaging transfer, plating and etching , are quite similar to those used when producing plated-through boards. However, there're differences due to the thin and floppy material used in flexible circuits.
Purpose of Flexible Circuits
1) To provide interconnections between printed circuit boards and other components.
2) To serve as three-dimensional substrates for the mounting of SMT components, e.g., in
photographic and video cameras.
3) To establish interconnections capable of withstanding dynamic flexing.
4) To form part of rigid-flex circuit boards.
2) Volume decreases
3) Weight reduces
4) Consistency of SMD mounting
5) Reliability increases
6) Controllability of electrical design of parameters
7) Tin soldered overall on the FPC end
8) Material optional (PI, PET)
9) Low cost
10) Continuity of processing
Thin-film switch, capacitive touch screen / panel, keypad FPC, laser head FPC,
General purpose LED soft light strip, mobile phone built-in antenna FPC Touch screen,
Telephone receiver / earphone FPC, contact belt of inkjet printer, Toy lamp strip,
LCD module, instrument panel, flexible flat cable, display backlight etc.
Flex PCB Capability
|1||Board Type||Single layer, Doulbe layer, Multilayer, Rigid-Flex|
|2||Base Material||PI, PET|
|3||Copper Weight||0.5oz, 1oz, 2oz|
|4||LED Maximum Size||250 x 5000mm|
|5||General Maximum Size||250 x 2000mm|
|8||Mininum Drill Hole||0.05mm|
|9||Maximum Drill Hole||6.5mm|
|10||Tolerance of Drill Hole||±0.025mm|
|11||Thickness of Hole Wall||≧ 8 um|
|12||Minimum Track/Gap of Single Layer Board||0.025/0.03mm|
|13||Minimum Track/Gap of Double Layer and Multilayer Board||0.03/0.040mm|
|15||Minimum Width of Silk Legend||≧ 0.125mm|
|16||Minimum Heigh of Silk Legend||≧0.75mm|
|17||Distance from Legend to Pad||≧0.15mm|
|18||Distance from Opening Solder Mask of Drill Coverlay to Track||≧0.03mm|
|19||Distance from Opening Solder Mask of Punching Coverlay to Track||≧0.03mm|
|20||Thickness of Immersion Nickel||100-300u"|
|21||Thickness of Immersion Gold||1-3u"|
|22||Thicnkess of Immersion Tin||150-400u"|
|23||Minimum Electrical Testing Pad||0.2mm|
|24||Minimum Tolerance of Outline(Normal Steel Mould Punch)||±0.1mm|
|25||Minimum Tolerance of Outline (Precision Steel Mould Punch)||±0.05mm|
|26||Mininum Radius of Bevel Angle (Outline)||0.2mm|
|27||Stiffner Material||PI, FR-4, 3M Adhesive, PET, Steel Sheet|
|29||Solder Mask Colour||Yellow, White, Black, Green|
Payment & Shipping Terms:
|Number Of Layers:||1||Glass Epoxy::||Polyimide (PI) 25um|
|Final Foil:||1 Oz||Final Height Of PCB::||0.20 Mm ±10%|
|Surface Finish:||Immersion Gold||Solder Mask Color::||Yellow|
|Colour Of Component Legend:||White||Test:||100% Electrical Test Prior Shipment|
Single Layer Thin Flexible PCBs Built On Polyimide With 1oz Copper 0.2mm Thick and Immersion Gold for Embedded Antennas
(FPC’s are custom-made products, the picture and parameters shown are just for reference)
This is a type of single layer flexible printed circuit for the application of Wireless Dongle, 0.2mm thick. The base laminate is from ITEQ, It’s fabricated per IPC 6012 Class 2 using supplied Gerber data. Polyimide stiffener is applied on the inserting head.
Parameter and data sheet
|Size of Flexible PCB||230.5 X 40.8mm|
|Number of Layers||1|
|Board Type||Flexible PCB|
|Board Material||Polyimide (PI) 25µm|
|Board Material Supplier||ITEQ|
|Tg Value of Board Material||60℃|
|PTH Cu thickness||≥20 µm|
|Inner Iayer Cu thicknes||N/A|
|Surface Cu thickness||35µm (1oz)|
|Number of Coverlay||1|
|Thickness of Coverlay||25 µm|
|Type of Silkscreen Ink||IJR-4000 MW300|
|Supplier of Silkscreen||TAIYO|
|Color of Silkscreen||White|
|Number of Silkscreen||1|
|Peeling test of Coverlay||No peelable|
|Legend Adhesion||3M 90℃ No peeling after Min. 3 times test|
|Surface Finish||Immersion Gold|
|Thickness of Nickle/Gold||Au: 0.03µm(Min.); Ni 2-4µm|
|Thermal Shock Test||Pass, -25℃±125℃, 1000 cycles.|
|Thermal Stress||Pass, 300±5℃,10 seconds, 3 cycles. No delamination, no blistering.|
|Function||100% Pass electrical test|
|Workmanship||Compliance with IPC-A-600H & IPC-6013C Class 2|
Features and benefits
Reducing the volume
Consistency of assembly
Continuity of processing
Focus on low to medium volume production
More than 18 years of experience
Mobile phone built-in antenna FPC, flex keyboard for mobile phone keys, Industrial control computer soft board
Copper foil is available in two different types of copper: ED Copper and RA copper.
ED copper is an electro-deposited (ED) copper foil produced in the same way as the copper foil used for rigid printed circuit boards. This also means that the copper is “treated”, i.e., it has a slightly rough surface on one side, which ensures a better adhesion when the copper foil is bonded to the base material.
RA copper is a rolled and annealed copper foil produced from electrolytically deposited cathode copper, which is melted and cast into ingots. The ingots are first hot-rolled to a certain size and milled on all surfaces. The copper is then cold-rolled and annealed, until the desired thickness is obtained.
Copper foil is available in thickness of 12, 18, 35 and 70 μm.
The most common available for dielectric substrate and coverlay is polyimide films. This material can also be used as coverlay. Polyimide is best suited for flexible circuits because of its characteristics as stated below:
High temperature resistance allows soldering operations without damaging the flexible circuits
Very good electrical properties
Good chemical resistance
Polyimide is available in thicknesses of 12.5, 20, 25 and 50 μm.
Base laminates for rigid printed circuit boards are copper foils laminated together with the base materials, the adhesive coming from the prepreg material during lamination. Contrary to this is the flexible circuit where the lamination of the copper foil to the film material is achieved by means of an adhesive system. It is necessary to distinguish between two main systems of adhesive, namely thermoplastic and thermoset adhesives. The choice is dictated partly by the processing, and partly by the application of the finished flexible circuit.