Structure of FPC
According to the number of layers of conductive copper foil, FPC
can be divided into single layer circuit, double layer circuit,
multi-layer circuit, double sided and so on.
Single-layer structure: the flexible circuit of this structure is
the simplest structure of the flexible PCB. Usually the base
material (dielectric substrates) + transparent rubber(adhesive) +
copper foil is a set of purchased raw materials(semi-manufactures),
the protective film and transparent glue are another kind of bought
raw material. First, copper foil must be etched to obtain the
required circuit, and the protective film should be drilled to
reveal the corresponding pad. After cleaning, the two are combined
by rolling. Then the exposed part of the pad electroplated gold or
tin to protect. In this way, the big panel board will be ready.
Generally also it’s stamped into the corresponding shape of the
small circuit board. There is also no protective film directly on
the copper foil, but printed resistance soldering coating, so that
the cost will be lower, but the mechanical strength of the circuit
board will become worse. Unless the strength requirement is not
high and the price needs to be as low as possible, it is best to
apply the protective film method.
Double layer structure: when the circuit is too complex to be
wired, or copper foil is needed to shield the ground, it is
necessary to choose a double layer or even a multilayer. The most
typical difference between a multilayer and a single plate is the
addition of a perforated structure to connect the layers of copper
foil. The first process of transparent rubber + base material +
copper foil is to make holes. Drill holes in the base material and
copper foil first, clean and then plated with a certain thickness
of copper. The subsequent fabrication process is almost the same as
the single-layer circuit.
Double sided structure: both sides of the double sided FPC have
pads, mainly used to connect other circuit boards. Although it and
monolayer structure is similar, but the manufacturing process is
very different. Its raw material is copper foil, protective film
and transparent glue. The protective film should be drilled
according to the position of the pad first, then the copper foil
should be affixed, the pad and track lines should be etched and
then the protective film of another drilled hole should be affixed.
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.
FPC Case: Rigid-flex PCBs Built on FR-4 and Polyimide
(FPC’s are custom-made products, the picture and parameters shown
are just for reference)
General description
This is a type of rigid flexible printed circuit boards for the
application of Wireless Security System. It’s a 3 layer rigid-flex
PCB at 1.6mm thick at rigid part. The base laminate is from
Shengyi. It’s fabricated per IPC 6012 Class 2 using supplied Gerber
data.
Parameter and data sheet
| Size of Flexible PCB | 91.5X 105.3mm |
| Number of Layers | 3 |
| Board Type | Rigid-flex PCB |
| Board Thickness | 1.6mm |
| Board Material | Polyimide (PI) 25µm |
| Board Material Supplier | Shengyi |
| Tg Value of Board Material | 60℃ |
| |
| PTH Cu thickness | ≥20 µm |
| Inner Iayer Cu thicknes | 35 µm |
| Surface Cu thickness | 35 µm |
| |
| Coverlay Colour | Yellow / Green Solder mask |
| Number of Coverlay | 2 |
| Thickness of Coverlay | 25 µm |
| Stiffener Material | NO |
| Stiffener Thickness | N/A |
| |
| 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 |
| RoHS Required | Yes |
| Famability | 94-V0 |
| |
| 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
Excellent flexibility
Reducing the volume
Weight reduction
Consistency of assembly
Increased reliability
Controllability of electrical parameter design
The end can be whole soldered
Material optionality
Low cost
Continuity of processing
Professional and experienced engineers
Eligible products rate of first production: >95%
Application
Laser head FPC, POS antenna soft board, tablet keypad flex board
About us
Based in China, Bicheng PCB adheres to the philosophy of helping
small and medium sized companies reduce their cost and time spent
on PCB. We provide a variety of PCB products to meet the demands.
Our Driving Circuit Boards Capabilities 2019
Blind vias, Buried vias
Flex PCB
Heavy Copper Boards 12oz
High Tg, High CTI Material
Hybrid FR-4 and High Frequency Material
Impedance Controlled PCB
IPC Class 2, IPC Class 3
Lead Free PCB (RoHS Compliant)
Multilayer PCBs to 32+ copper layers boards
Metal Core PCB (MCPCB)
PCB Materials – FR-4, Polyimide, Rogers & More
RoHS Compliant PCB Manufacturer
Rigid Flex PCB
RF PCB / High Frequency PCB
Through-hole, BGA, Gold Finger, Edge dome
Via-in-pad, Filled vias
TS16949 (2009), ISO14001 (2004), ISO9001 (2008), UL certified
Our Services
Focus on Prototypes, Small Batches, Volume Production
Quick turn-around, double sided PCB 24 hours available.
Door to door shipment service
Our Clients are located worldwide.
Australia: Perth, Melbourne, New South Wales, South Australia, West
Australia
Austria: Breitenfurt bei Wien, Graz
Bangladesh: Purana Paltan
Belgium: Deinze, Hasselt
Bulgaria: Plovdiv
Brazil: Caxias do Sul
Canada: Quebec, Ontario, Vancouver
Czech: Pardubice, Horní Pocernice
France: Villeneuve La Garenne Cedex, Montchenu
Germany: Stuttgart, Garbsen, Hamburg, Altenburg, Velbert
Kleinmachnow, Potsdam
Hungary: Budapest
India: Tamilnadu
Ireland: Cork
Israel: Nettanya City, Ben-Gurion Airport, Tel Aviv, Yahud, Acre,
Italy: Peschiera Borromeo, Verona, Mezzocorona, Pietrasanta Lucca,
Torino
Kuwait: Safat
Malta: Mosta
Malaysia: Selangor
Mexico: Leon Guanajuato
Portugal: Guimaraes
South Korea: Gyeonggi-DO
Serbia: Kragujevac
Sweden: Goteborg, Siljansns,
Thailand: Bangkok, Chonburi
Turkey: Ankara, Istanbul, Kocaeli
The Netherlands: Diemen
UK: Bristol, Surrey
Ukraine: Kiev
USA: Connecticut, Alaska, New York City, Miami,, New Jersey, Texas,
Colorado, Largo, California, Candler
Vietnam: HoChiMinh City
Zambia: Kitwe
