Materials of Flexible PCB

Each element of the flex circuit construction must be able to consistently meet the demands placed upon it for the life of the product. In addition, the material must work reliably in concert with the other elements of the flexible circuit construction to assure ease of manufacture and reliability. Following are brief descriptions of the basic elements of flex circuit construction and their functions.

The base material is the flexible polymer film which provides the foundation for the laminate. Under normal circumstances, the flex circuit base material provides most primary physical and electrical properties of the flexible circuit. In the case of adhesiveless circuit constructions, the base material provides all of the characteristic properties. While a wide range of thickness is possible, most flexible films are provided in a narrow range of relatively thin dimension from 12 µm to 125 µm (1/2 mil to 5 mils) but thinner and thicker material are possible. Thinner materials are of course more flexible and for most material, stiffness increase is proportional to the cube of thickness. Thus for example, means that if the thickness is doubled, the material becomes eight times stiffer and will only deflect 1/8 as much under the same load. There are a number of different materials used as base films including: polyester (PET), polyimide (PI), polyethylene napthalate (PEN), Polyetherimide (PEI), along with various fluropolymers (FEP) and copolymers. Polyimide films are most prevalent owing to their blend of advantageous electrical, mechanical, chemical and thermal properties.

Adhesives are used as the bonding medium for creating a laminate. When it comes to temperature resistance, the adhesive is also typically is the performance limiting element of a laminate especially when polyimide is the base material. Because of the earlier difficulties associated with polyimide adhesives, many polyimide flex circuits presently employ adhesive systems of different polymer families. However some newer thermoplastic polyimide adhesives are making important in-roads. As with the base films, adhesives come in different thickness. Thickness selection is typically a function of the application. For example, different adhesive thickness is commonly used in the creation of cover layers in order to meet the fill demands of different copper foil thickness which may be encountered.

A metal foil is most commonly used as the conductive element of a flexible laminate. The metal foil is the material from which the circuit paths are normally etched. A wide variety of metal foils of varying thickness are available from which to choose and create a flex circuit, however copper foils, serve the vast majority of all flexible circuit applications. Copper’s excellent balance of cost and physical and electrical performance attributes make it an excellent choice. There are actually many different types of copper foil. The IPC identifies eight different types of copper foil for printed circuits divided into two much broader categories, electrodeposited and wrought, each having four sub-types.) As a result, there are a number of different types of copper foil available for flex circuit applications to serve the varied purposes of different end products. With most copper foil, a thin surface treatment is commonly applied to one side of the foil to improve its adhesion to the base film. Copper foils are of two basic types: wrought (rolled) and electrodeposited and their properties are quite different. Rolled and annealed foils are the most common choice, however thinner films which are electroplated are becoming increasingly popular.

In certain non standard cases, the circuit manufacturer may be called upon to create a specialty laminate by using a specified alternative metal foil, such as a special copper alloy or other metal foil in the construction. This is accomplished by laminating the foil to a base film with or without an adhesive depending on the nature and properties of the base film.

The deep BAF process for PCB waste water (3)

3.2 BAF impact on the rest of the water quality indicators

3.2.1 wastewater pH changes

raw water after the factory original coagulation precipitation process preliminary treatment, when entering the BAF system average pH 9.0, basic on the verge of overweight and direct emissions may be the cause of river pollution, soil alkalization, etc. Using BAF process, due to the microbial nitrification system consumes basicity (mainly NH4 +) in waste water, the water pH basic remain at around 7.9, standard ensures water at any time.

3.2.2 the change of ammonia nitrogen in wastewater

Wastewater after treated with BAF system declined, of ammonia nitrogen in water by 19.86 mg/L fell to 13.89 mg/L, but has yet to reach discharge standards, this is due to the best of nitrifying bacteria, proliferation and survival temperature is 25 ℃, while during the experiment system in a row after the water temperature maintained in 11 ~ 16 ℃, under the temperature of BAF in the growth and activity of nitrifying bacteria is restrained, resulting in poor ammonia nitrogen removal efficiency.

3.2.3 waste water in copper complexing state changes

The copper ammonia wastewater mainly complex ion (Cu (NH3) 2 + 4) exist, Cu2 + is very little.BAF role to eliminate the Cu complex in from [Cu (NH3) 2 + 4) isolated Cu2 +, OH - from their response to that of the wastewater generated Cu (OH) 2 precipitate, which was BAF biological flocculation adsorption.

BAF process in the wastewater Cu complexing state overall declining (1.40 mg/L to 0.82 mg/L), but the water was not up to standard. This is because the BAF nitrification and the Cu (OH) 2 is the best temperature flocculation adsorption 20 ~ 30 ℃, and the system straight into the water after the water temperature maintained at 11 ~ 16 ℃, seriously inhibit the adsorption of biofilm activity, lead to the removal of Cu effect is not very ideal.

4. Conclusion

(1) using the depth of the BAF process a printed circuit board factory PCB wastewater treatment, when the water COD load of 0.12 kg/(m3 · d), average inlet COD is 187.8 mg/L, the process average effluent COD can be dropped to 41.8 mg/L; When water COD load up to 0.36 kg/(m3 · d), the average COD water can also fell to 42.1 mg/L, fully meet the local relatively strict wastewater discharge standard requirements.

(2) Because the backwash water quality to suit the requirements of discharge standards, emissions should be to adjust the pool to processing. Backwash cycle is about 15 d.



(3) During the experiment temperature is 11 ~ 16 ℃, BAF in the growth and activity of nitrifying bacteria is restrained, flocculation adsorption activity of the biofilm, ammonia nitrogen and complexing state Cu removal effect is not very ideal. Need to consider to take corresponding measures to improve the filter water temperature or appropriate to ammonia nitrogen in water and Cu for further processing.

Flex circuits

Flex circuits are often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring. A common application of flex circuits is in computer keyboards; most keyboards use flex circuits for the switch matrix.
In LCD fabrication, glass is used as a substrate. If thin flexible plastic or metal foil is used as the substrate instead, the entire system can be flexible, as the film deposited on top of the substrate is usually very thin, on the order of a few micrometres.
Organic light-emitting diodes (OLEDs) are normally used instead of a back-light for flexible displays, making a flexible organic light-emitting diode display.
Most flexible circuits are passive wiring structures that are used to interconnect electronic components such as integrated circuits, resistor, capacitors and the like, however some are used only for making interconnections between other electronic assemblies either directly or by means of connectors.
In the automotive field, flexible circuits are used in instrument panels, under-hood controls, circuits to be concealed within the headliner of the cabin, and in ABS systems. In computer peripherals flexible circuits are used on the moving print head of printers, and to connect signals to the moving arm carrying the read/write heads of disk drives. Consumer electronics devices make use of flexible circuits in cameras, personal entertainment devices, calculators, or exercise monitors.
Flexible circuits are found in industrial and medical devices where many interconnections are required in a compact package. Cellular telephones are another widespread example of flexible circuits.
Flexible solar cells have been developed for powering satellites. These cells are lightweight, can be rolled up for launch, and are easily deployable, making them a good match for the application. They can also be sewn into backpacks or outerwear.

If you need expert flexible PCB service, please contact wonderful02@wonderfulpcb.com.

OEM PCB and PCBA----Wonderful PCB(hk)Limited

Total product solution often requires Flexible pcb production and assembly which we offer our clients. Among the different types of OEM products we produce are complete /partial turnkey manufacturing including BOM building+ Material procurement and management assurance.

In the PCBA lines we have the most advanced machinery that include Lead-Free Capability, BGA SMT placement, Conventional ‘thru-hole’ PCB assembly. For the testing we offer In-Circuit Test, Analogue/ Digital functional test equipment, Customized testing programs and fixtures.
Wonderful PCB well trained engineering stuff will be happy to learn your needs and reply accordingly just let us know -we can assure you will be satisfied from the results...
Printed circuit board is wide application in all kinds of electronic products. The aluminum PCB is use LED light.
Wonderful PCB is professional manufacturer of high quality PCB&PCBA with competitive price and attractive lead time.
NO MOQ:
We supply PCB Prototype & Mass production with good price and high quality.              

All the PCB is reaching IPC II Standard.                                         
In as much as Wonderful PCB has no control over the use to which others may put the material, each user of the material is not released of making his own tests to determine the material’s suitability for his own particular use. Statements concerning possible or suggested uses of the materials described herein are not be construed as constituting a license under any Wonderful PCB patent application covering such use or as recommendations for use of such materials in the infringement of any patent.
Lamination assist had Kraft press pad, silicon rubber press pad, Teflon release film, pressure revealing films. With the description of provide uniform cushioning and precise control over heat rise and long life (up to 150 uses) and faster lay-up. Put talcum powder before use.

Our pressure revealing film is a unique analytical tool. Provides a quick, easy and accurate in-house procedure for checking for “high” and “low” pressure zones due to press platen misalignments or the design configuration (pads, high density circuitry, ground planes, etc.) of the circuit board itself

Wonderful PCB Manufacturer

Common PCB surface treatment process are: hot air leveling (HASL, hot air solder leveling), organic coating (OSP), electroless nickel / immersion gold, immersion silver, immersion tin, etc.

1)HASL，hot air solder leveling
    HASL also known as hot air solder leveling, it is in the molten tin-coated surface of the PCB and use heated air leveling (blown flat) process, to form a layer of copper oxide can be both anti provide good solderability of the coating layer. HASL solder and copper usually formed with copper-tin metal compound has a thickness of about 1 ~ 2mil.

2)OSP
    Skim -> micro etch -> Pickling -> water cleaning -> organic coating -> cleaning, process control relative to other treatment processes more easily.

3)Electroless Nickel / Immersion Gold (also known as chemical gold)
    Clean off the pickling -> micro-etch -> grep -> activate -> Electroless Nickel -> chemical leaching of gold; their process of six chemical tank, involving nearly a hundred kinds of chemicals, the process is relatively complicated.

4)Immersion Silver
    Immersion Silver is a displacement reaction, it is almost sub-micron silver coating. Sometimes silver leaching process can also contain organic compounds, mainly to prevent migration of silver silver corrosion and eliminate the problem, this is very difficult to measure out a thin layer of organic matter, analysis showed less than 1% by weight of the organism.

5)Immersion Tin
Due to the current all tin-based solder is, the tin layer with any type of solder to match, from this point of view, immersion tin process is very promising. But previous PCB via solder dipping process easy after whisker, welding and tin migration over soldering shall bring reliability problems, thus limiting the immersion tin process of adoption. After immersion tin solution, the organic additive, the granular structure of the tin layer structure to overcome the previous problem, but also has good thermal stability and weldability.

Sophie Deng
_______________________________________
Wonderful Rigid-flex pcb Limited
NO.32A,Building NO.1, XianDaiC hengHuaTing,ChuangYeRoad|NanShan District,ShenZhen City 518054|  China  T +86-755-86229518-806 | F  +86 755 2607 3529|  e  wonderful08@wonderfulpcb.com |
w  www.wonderfulpcb.com  | Skype:wonderful-07   |                                                  
Welcome to our trading shows:
1.Booth: L32,Expo Electronic 2013,Apr.10-12th in CROCUS EXPO,Moscow,Russia
2.Booth: 11J36, HK Global sources  Apr.12-15th, 2013 Asia World-Expo, Hong Kong
3.Booth: 9J35, HK Global sources Oct.12-15th,2013 Asia World-Expo, Hong Kong
4.Booth: 70206, CES  2014  Jan,8th-11th in Las Vegas, USA

FPC assembly Pallets features

I would like to introduce the comparison between Magnetic reflow pallets and silica gel plate.

A. Stability: magnetic reflow pallet in magnetic state to even out the FPC, as the physical process,magnetic may increase or decrease according to request, don't change due to factors such astemperature, time, relatively stable.Silica gel plate adopt chemistry, will change under differenttemperature or Time or other condition, which lack of stability. Especially in the use of a certainperiod of time after a drop in viscosity, and not clean viscosity decreased during us, which cause FPC substrate deformation while crossing the reflow soldering and affect the welding quality.

B. Usage Life: magnetic reflow tray used in magnetic material and working principle of physicalprocess, are high temperature resistant material,As long as it's not  destroyed by man or at accident situation, it can be permanent online.  statecan use permanent damage and accidents.Silica gel plate in use process, USES the chemical process,Inuse process, it will be aging of due to silicone materials, including Japan's material, no more than1000 times return.The cost is very high.

C. Quality: magnetic reflow pallet at work on FPC insulating protection at the same time, FPC won’t be destroyed when workman pick up the FPC.Silica gel plate in use process to ensure the smooth ofFPC, has certain viscosity,and will stick to FPC, which will be difficulty for picking up FPC andmay cause FPC deformation.

Comparison between Magnetic reflow pallets and normal plateA.Quality: magnetic reflow pallet, because of FPC flat surface cause from the steel, reflowsoldering will be reduced during FPC flow, which can guarantee the stability of welding quality,reduce adverse.Ordinary tray can only be used with high temperature tape around the FPC, afterreflow soldering, which easy to cause deformation to the middle part of FPC, tin water to overflow, cause badwelding, which will affect the quality. At the same time, magneticReflow soldering tray can reduce some difficulty, like can avoid the high temperature stick to Flexible pcblead to hard FPC being picked up or flexible PCB deformation.

Cost: magnetic reflow soldering tray, convenient to use,  reduce prework workers, and the personto take off the tape after reflow soldering, at meanwhile, can reduce the use amount of the hightemperature tape. Investment is bigger at first time to magnetic reflow soldering tray, however, ithas cost advantage for mass production.

Several classification of flexible printed circuit board

At present, mainly has the single side, double side, multilayer flexible circuit and Flexible pcb just four.


(1) single flexible plate is the lowest cost, when the PCB for electrical demand is not high.When single wiring, should choose single flexible plate.It has a layer of chemical etching of conductive graphics, in the flexible conductive graphics layer on the surface of the insulating substrate for rolled copper foil.Insulating base material can be polyimide, polyethylene terephthalate, aromatic polyamide fiber resin and PVC.


(2) double flexible plate is on the two sides each have a layer of insulating base film etching made of conductive graphics.Metallized hole to both sides of the insulation materials connection form a conductive path, in order to meet the deflection design and use of the function.While covering film can protect the single and double wires and components placed.


(3) multilayer flexible plate is a level 3 or more layers of single sided or double sided laminated flexible circuit together, through the drill away L form hole metallization, electroplating, the formation of a conductive path between different layers.So, do not need to adopt the complex welding process.Multilayer circuit in higher reliability, better thermal conductivity and convenient assembly has huge function differences in performance.When designing the layout, assembly shall be taken into consideration, layer number and size of flexible influence each other.


(4) the traditional just flexible plate is made from rigid and flexible substrate has a choice of formation pressure together.Structure closely to metallization away L form electrical connection.If a PCB is, opposite element, just flexible plate is a good choice.But if all the components are on one side, selects the double flexible plate, and on the back of the laminated layer on FR4 reinforced material, will be more economic.


Hybrid structure is a kind of sandwich plate, flexible circuit conductive layer made of different metals.A eight layer plate using FR - 4 as inner layer medium, the use of polyimide as outer medium, out from three different direction of the main board, lead each wire made of different metals.Constantan alloy, copper and gold as independent lead, respectively.This kind of hybrid structure is mostly used in electrical signal conversion and is quite harsh relationship and performance of heat transformation of low temperature circumstances, is the only feasible solution.


Even through the design and how easy it is to evaluate the total cost, in order to achieve the best performance/cost ratio.