Basic information of flexible printed ciruicts boards

FPC flex printed circuits board process includes exposure, PI etching, opening, electrical testing, punching, appearance testing, performance testing, etc. The FPC flexible board production process is related to the performance of the FPC, after the completion of the production it needs to be tested to screen out the unqualified FPC flexible board, to ensure that the FPC in the application maintains good performance, to play the best role. The FPC flexible board test can have the role of conduction and convection of high-current slug micro-pin module to protect the stability and efficiency of the FPC flexible board test.

flex printed circuits substrates are mainly polyimide, polyester, and polytetrafluoroethylene three categories.
Polyimide (PI), with high-temperature resistance, high dielectric strength, excellent electrical and mechanical properties, but the price is on the blame, easy to absorb moisture.PI is the most commonly used substrate for FPC. Different manufacturers produce out of the polyimide name, such as DuPont produced out of the PI called “Kapton”.
Polyester (PET), has many properties and PI similar, but poor heat resistance, which determines the product can only be operated at room temperature.
Polytetrafluoroethylene (PTFE) is very expensive and is mainly used in high-frequency products with low dielectric constants.

The flexible sheets of polyimide are divided into adhesive and non-adhesive sheets.
Glued sheet, by the copper (copper) + glue (adhesive) + base material (base film) composition.
Non-adhesive sheet, which is directly composed of copper foil (copper) + base film (base film).
The difference lies in whether or not there is glue in the middle.
General products can be produced using normal adhesive sheets; but the high-performance requirements of the product, such as the need to carve precision lines or products operating at high temperatures (TG value of ≥ 170 degrees), require to use of non-adhesive sheets, but non-adhesive sheet price is expensive, for the ordinary adhesive sheet of about 7 times, so customers should be designed to measure the two sides of the product factors.

The covering film is equivalent to the solder ink of the rigid board, which plays the role of anti-soldering. Covering film consists of polyimide + adhesive, polyimide thickness is generally 0.5mmil, 1mmil, 2mmil, which corresponds to the thickness of the glue being different, the role of the glue is to bond with the flexible sheet.

Advantages and disadvantages of flex printed circuits boards:
Compared with ordinary PCB (hardboard), wires, or cables, flexible boards have the following advantages.
(1) Flexibility, can meet the three-dimensional, dynamic needs
(2) thickness tour, small size, lightweight
(3) Low processing costs, easy to assemble
In particular, other advantages over ordinary cables or shielded cables are.
(1) high consistency of mechanical and electrical characteristics (relative to cables)
(2) High density
(3) Good impedance control capability
(4) Fewer connection points
At the same time, its shortcomings are.
(1) Difficult to maintain
(2) Requires additional support
(3) Poor impedance consistency
(4) Dimensional stability is not good enough (relative to hardboard)

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