Flexible circuit board's -STG PCB Assembly
1、Flexible circuit board's deflection sex and reliability
There are four kinds of flexible circuit:Single-sided, double-sided, multi-layer flexible board and rigid board.
a)single-sided flexible print circuit boards is the lowest cost, when less demanding on the electrical properties of the PCB. Single-sided wiring should choose the single-sided flexible board.It has a layer of chemical etching of conductive graphics, the flexible insulating substrate conductive graphics for rolled copper foil insulation layer on the surface of the substrate can be a polyimide, polyethylene terephthalate, aromatic polyamide fiber and polyvinyl chloride (PVC)
b)Thedouble-sided flexible board On both sides of the base film with a layer of insulation etching made of a conductive pattern,Metallized hole graphical connection is formed ofthe insulating material on both sides of the conductive paths,in order to meet the deflection design and use function.And the covering film can protect single-sided conductor and indicate the position of the element housing.
c)The multilayer flexible plate are three or more layers of single-sided or double-sided flexible circuits laminated together.Metallized hole are formed by drilling away L, electroplating, form a conductive path between different layers.So, do not need to adopt complicated welding process. Multilayer circuit in higher reliability, better heat conductivity and convenient assembly has the huge function differences in performance.In designing the layout, you should take into account the mutual impact this pcb assembly dimensions, layers and flexible, without the use of complex welding process.
d)The traditional rigid board is selected by the rigid and flexible substrates laminated together to form the. Compact structure, and forming conductive connections metalization larvae L. If a PCB is, the opposite has components, rigid flexible board is a good choice. However, if all the components are in the side, a double-sided flexible board, and the reinforcing material laminated on the back layer of FR4, will be more economical.
e)The flexible circuit of the mixed structure is a multilayer, the conductive layer is constituted by a different metal. An 8 laminates using FR-4 as the inner layer of the medium, using polyimide as the outer layer of the medium, leads, each lead extending in three different directions from the motherboard made of a different metal. Of constantan alloy, copper and gold, respectively, for independent leads. Most of this hybrid structure relations and electrical properties of the electrical signal is converted heat conversion harsh cold case, is the only viable solution.
2、The economy of flexible circuit
If the circuit design is relatively simple, the total volume is small, and suitable space, even in the traditional way are far less expensive. If the pcb assemblt line complex,processing many signals or special electronic or mechanical property requirement,flexible corcuit is agood design choice.When appication size and performance beyond the rigid circuit capacity,flecible packing is the most economical.On a piece of film can be made with 5mil 12mil of through-hole pad and 3mile line spacing and flexible circuits. Therefore,mounting chips directly on the film aremore reliable. morereliable.Because they don't contain flame retardants of smear ion source.These film may be protective in nature,and cured at high temperatures,higher glass transition temperature.Flexible than rigid materials cost saving due to eliminating the connector
Flexible printed circuits industry is in a small but rapid development. Polymer thick-film method is an efficient, low-cost production technology. Cheap flexible substrates the technology to selectively screen printed conductive polymer inks. Its representation of the flexible base material for the PET. Polymer thick-film conductors including screen printing metal filler or toner filling. Polymer thick film itself is very clean, using lead-free SMT adhesives without etching. By using the addition process and base materials, low cost, polymer thick-film circuit is a copper price of polyimide thin film circuits one-tenth; is price of rigid circuit board 1/2~1/3. Polymer thick film method is especially useful for device control panel. On mobile phones and other portable products, polymer thick film suitable for components on the printed circuit board, switches and lighting devices into polymer thick film circuits. Both cost savings and reduced energy consumption.
Despite these cost factors, but flexible Assembly prices are falling, and close to the traditional rigid circuit. The main reason is the introduction of the updated material, improve the production process and the change of structure. Structure allowing for higher thermal stability now, few materials do not match. Some more updated material for copper layer is thin and can produce more sophisticated lines that enables components lighter, more suitable for mounting in small spaces. The past, the use of rolling technology of copper foil residue on the adhesive-coated media, and now, you can build directly on the media does not use adhesive copper foil. These technologies can be a few Micron thick layer of copper, are 3M. 1 precision line of even width more narrow. Removed after a certain adhesive flexible printed circuits with flame retardant properties. This can speed up the uL certification process and further reduce costs. Flexible PCB solder masks and other surface coatings enable flexible Assembly to reduce costs further.