1. Flexibility and reliability of flexible circuits
Currently there are: single-sided FPC, double-sided, multi-layer flexible boards and just four kinds of flexible boards.
①Single-sided flexible board is the lowest cost, when the electrical performance requirements are not high printed board. In the single-sided wiring, should choose a single-sided flexible board. It has a layer of chemical etching out of the conductive pattern, in the flexible insulating substrate surface of the conductive pattern layer for the calendered copper foil. The insulating substrate may be polyimide, polyethylene terephthalate, aramid fiber ester and polyvinyl chloride.
② double-sided flexible board is in the insulating base film on each side of a layer of conductive graphics made by etching. Metallized holes will be insulating material on both sides of the graphic connection to form a conductive pathway to meet the design and use of flexural function. The overlay film protects single and double-sided wires and indicates where components are placed.
③Multilayer flexible board is 3 or more layers of single- or double-sided flexible circuits laminated together, through the drilling of solenoids, plating the formation of metallization holes in the different layers to form a conductive pathway. This eliminates the need for complex soldering processes. Multi-layer circuits make a huge functional difference in terms of higher reliability, better thermal conductivity and easier assembly performance. The interaction of assembly dimensions, number of layers and flexibility should be taken into account when designing the layout.
④Traditional rigid-flexible boards are composed of rigid and flexible substrates selectively laminated together. The structure is tightly packed with metallized solenoids to form conductive connections. If a printed board has components on both the front and back sides, a rigid-flexible board is a good choice. However, if all the components are on one side, it is more economical to choose a double-sided flexible board with a layer of FR4 reinforcement laminated on the back side.
⑤Hybrid-structured flex circuits are multilayer boards with conductive layers made of different metals. An 8-layer board uses FR-4 as the dielectric for the inner layer and polyimide as the dielectric for the outer layer, with leads protruding from the main board in three different directions, each made of a different metal. Conoco alloy, copper and gold are used as separate leads. This hybrid structure is mostly used in the relationship between electrical signal conversion and heat conversion and the electrical properties of the more demanding low-temperature case, is the only viable solution.
Can be evaluated by the convenience and total cost of the internal connection design to achieve the best performance-price ratio.
2. Economy of flexible circuits
If the circuit design is relatively simple, the total volume is not too large, and the space is suitable, most of the traditional internal connection methods are much cheaper. If the circuit is complex, handles many signals or has special electrical or mechanical performance requirements, flexible circuits are a better design choice. When the size and performance of the application exceeds the capabilities of a rigid circuit, the flexible assembly method is the most economical. Flexible circuits can be made on a single sheet of film with 12 mil pads with 5 mil via holes inside and 3 mil lines and spacing. Therefore, it is more reliable to mount chips directly on the film. This is because it does not contain flame retardants that can be a source of ionic drilling contamination. These films may be protective and cure at higher temperatures to get a higher glass transition temperature. The cost savings of flexible materials over rigid materials is due to the elimination of connectors.
The high cost of raw materials is the main reason for the high price of flexible circuits. The price of raw materials varies greatly, the cost of raw materials used in the lowest-cost polyester flexible circuits is 1.5 times the cost of raw materials used in rigid circuits; high-performance polyimide flexible circuits are up to four times or more. At the same time, the flexible nature of the material makes it difficult to automate the manufacturing process, resulting in lower yields; in the final assembly process is prone to defects, these defects include peeling off the flexible attachment, line breakage. These are more likely to occur when the design is not suitable for the application. Under high stresses caused by bending or molding, it is often necessary to select reinforcing or strengthening materials. Despite their high raw material costs and manufacturing hassles, foldability, bendability, and multi-layer paneling capabilities lead to a reduction in overall component size and a subsequent reduction in the materials used, resulting in a lower total assembly cost.
The flexible circuit industry is in the midst of a small but rapid development. The polymer thick-film method is an efficient, low-cost production process. The process selectively screen prints conductive polymer inks on inexpensive flexible substrates. A representative flexible substrate is PET, and the polymer thick film conductors include screen-printed metallic fillers or toner fillers. The polymer thick film method is inherently clean, uses lead-free SMT adhesives, and does not require etching. Because of its additive process and low substrate cost, polymer thick-film circuits are 1/10 the price of copper polyimide thin-film circuits and 1/2 to 1/3 the price of rigid circuit boards. polymer thick-film is particularly well suited for device control panels. In cell phones and other portable products, polymer thick film method is suitable for the printed circuit board components, switches and lighting devices into polymer thick film circuit. Both cost and energy savings are realized.
In general, flexible circuits do cost more than rigid circuits. When flexible boards are manufactured, in many cases they have to face the fact that many of the parameters are out of tolerance. The difficulty in manufacturing flexible circuits lies in the flexibility of the material.
3. Cost of Flexible Circuits
Despite the cost aspect mentioned above, the price of flexible assemblies is decreasing and becoming close to the traditional rigid circuits. The main reasons for this are the introduction of newer materials, improved manufacturing processes, and structural changes. The construction now allows for a more thermally stable product with few material mismatches. Some of the newer materials allow for more precise lines due to thinner layers of copper, making the components lighter and more suitable for fitting into smaller spaces. In the past, copper foils were bonded to an adhesive-coated medium using a roller pressing process; today, copper foils can be produced directly on the medium without the use of adhesives. These techniques allow for copper layers several micrometers thick and precision lines of 3 m.1 or even narrower widths. Flexible circuits are flame retardant after the removal of certain adhesives. This can accelerate the uL certification process and further reduce costs. Flexible circuit board solder masks and other surface coatings further reduce the cost of flexible assembly.
In the coming years, smaller, more complex, and more costly flexible circuits will require more innovative methods of assembly and an increase in hybrid flexible circuits. The challenge for the flex-circuit industry is to capitalize on its technological strengths and keep pace with computers, remote communications, consumer demand, and active markets. In addition, flexible circuits will play an important role in the lead-free initiative.
FPC is short for Flexible Printed Circuit, also known as flexible circuit boards, flexible printed circuit boards, flexible circuit boards, referred to as flexible boards or FPC, with high wiring density, light weight, thin thickness.
Mainly used in cell phones, laptops, PDAs, digital video cameras, LCMs and many other products.
FPC Flexible Printed Circuits are made of polyimide or polyester film as a substrate with a high degree of reliability, excellent flexible printed circuits.
Product Features:
1. It can be freely bent, folded, coiled, and can be moved and retracted at will in three-dimensional space.
2. Good heat dissipation performance, can utilize F-PC to reduce the size.
3. Lightweight, miniaturized, and thin, thus achieving integration of component devices and wire connections.
FPC applications
MP3, MP4 players, portable CD players, home VCD, DVD, digital cameras, cell phones and cell phone batteries, medical, automotive, aerospace and military
FPC become an important variety of epoxy copper cladding boards
With the flexibility of the function of epoxy resin as the substrate for the flexible copper cladding ( FPC ), due to the possession of the epoxy resin as a base material. FPC is becoming an important variety of epoxy resin-based copper-clad laminates due to its special features and wider use. But our country started late to catch up.
Epoxy flexible printed circuit board since the realization of industrial production, has experienced more than 30 years of development. From the 1970s into a truly industrialized production, until the late 80s, due to a new class of polyimide film materials and applications, Flexible Printed Circuit Board so that the FPC appeared without adhesive type of FPC (generally known as the "two-layer type FPC"). In the 1990s, the world developed a photographic cover film corresponding to high-density circuits, which led to a major shift in the design of the FPC. Due to the opening up of new application fields, the concept of its product form changed considerably, and it was expanded to include a wider range of substrates for TABs and COBs. In the second half of the 1990s, high-density FPCs began to enter large-scale industrial production. Its circuit graphics are drastically developing to a finer degree, and the market demand for high-density FPCs is growing rapidly.
FPC can also be referred to as: flexible circuit board
PCB is called a rigid board
The most common materials such as:
U.S.: DUPONT ROGERS Japanese: Arisawa TORAY Shin-Etsu KYOCERA Sony
Taiwan: Taiwan Rainbow Hongren Ruosheng four-dimensional Xin Yang Jia Sheng
Domestic: DANBANG JIUJIANG HUAHONG
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Other Abbreviations
1. =Federal Power Commission
2. =food protein concentrate
3. =Friends Peace Committee
3. 3. =Friends Peace Committee Quaker or Quaker Peace Committee
4. =Food Packaging Council
5. =Free Pascal (a cross-platform Object pascal language similar to the delphi software development platform similar to delphi)