Outline processing of flexible circuits usually use punching method. The tooling we have two kinds: simple tooling and hard tooling for punching. Please see below the differences between these two molds:
Category Archives: FPC - Page 2
Stripping of Flexible circuits
Posted by admin
on December 3, 2010
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Stripping of flexible circuits is intended to clear resist layer to expose the copper on the board after etching. Does operation of stripping of flexible circuits going smoothly, dependent on equipment design and preparation of the liquid two main parts.
Stripping is relative simple compare to etching of flex circuit with the complex machine. But the “film residue” filtering, and recycling waste shall be disposed properly.
The chemical liquid of stripping, generally use the traditional NaOH(based),solution concentration is about 1-3% in weight, and temperature of the solution between about 40-55 ℃. The major reasons to use the NaOH in our industry: for dry film with good solubility, low prices and easy got. However, according to the actual use of that low concentration of NaoH work not very well, so now the mostly use KoH instead of NaoH as the solution for stripping.
The chemical properties of KoH and NaoH are very similar, but because of the dissolution of K for the dry film with excellent performance, and enhance the effect of stripping. This way don’t need to change the existing production equipments and the filtering effect of the film residue are improved.
The problems appear in etching process
Posted by admin
on November 23, 2010
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Do you know what problems will appear in etching process of flexible circuits? Ok, follow me to know the details:
1) Etching speed is geeting slower
This is usually because of the low temperature, low spray pressure or chemical proportion of etching solution. But if these conditions under well control, the etching speed slow may be due to the dissolution copper content is too high. At this point, it is necessary to adjust the etching solution.
2) Precipitation appear in solution
This is due to lack of complexing agent Cl-, or the dilution caused by water. Precipitate is Cu2Cl2: insoluble in water.
3) Resist layer is damaged:
When excess acid is being, this phenomenon appeared. Especially in higher temperatures will appear. Now we can replaced by NaOH or water to adjust. If the acid concentration and the conditions are suitable, then the problem may be due to improper cleaning of the board or exposure of flexible pcb.
4) The yellow residue in the copper surface
This residue is generally copper hydroxide, which does not dissolve in water. When the board is etched or alkaline cleaning to as the residue left on the board. In addition, when Cl-concentration and the acidity is too low in etching solution, after etched the white precipitate appeared on board, which may be insoluble Cu2Cl2 precipitation. Now we can use 5% hydrochloric acid solution to wash, and last wash by water.
When we know the above problems will appear in the etching process of flex circuits, so we will make the well quality controlling system to control these problems, and then ensure high quality flexible circuits, flex pcb.
Flexible circuits Developing Quality Check
Posted by admin
on November 11, 2010
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Let’s tell you one way to check the trace quality is good or not after developing of flexible circuits. After developing, even if some developing trace is dirty, or the base is long, is unable to check them out with a magnifying glass; but Cucl2 test is a non-destructive testing way. Testing methods are as follows:
1) First to clean the flexible pcb surface after developing, for example:
After developing → acid washing → acid etching → acid
2) in a 5% Cucl2 solution for 30 seconds, the best to swing liquid slightly, and use a sponge to remove small air bubbles on the board to invoid to affect judgments.
3) washed
4) drying
5) visual inspection
The copper surface of normal developing will form a layer of gray and black oxide layer after handling. When the surface of flex pcb with dry film glue, there will still maintain a bright copper color. This method can be tested if developing of flexible circuits is good.
Related Posts:
1.Drilling of flexible circuits;
2.FPC Exposed Process Operation Notes.
Solution configuration of FPC developing process
Posted by admin
on November 5, 2010
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Developing process of flexible circuits is the unexposed active group of photographic film part response to dilute alkali solution to the produce soluble substances and dissolve, leaving the already sensitive graphical circuit pattern. The most common used liquid is made of Na2CO3, weight content ratio between 0.75% and 2%.
Dry or wet film load is small, so the correct solution configuration of flexible pcb is the most basic step, in order to accurately control the concentration, we use acid-base titration method calculate the concentration of Na2CO3.
Reference to below methods:
(1) Sampling 25ml developing liquid in 250ml beaker;
(2) by adding D.I. water 100ml and 3-5 drops of methyl orange;
(3) use 0.1N hydrochloric acid to titrate the color changed to red;
(4) Calculate: wt% Na2CO3 = 0.0212 × titre (ml).
Usually dry film in 1% Na2CO3 developing liquid, the loading is about 12-15 mil-ft2/gal. At a higher developing pressure and under the full water washing can be obtained higher loading.
DI water, soft water is recommended for developing of flexible circuits, the use of hard water would have caused the hard dirt to clog of the nozzles.
FPC Exposed Process Operation Notes
Posted by admin
on November 2, 2010
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Today follow me to know the FPC exposed process operation notes, exposed is the very important step of making flexible circuits.
(1) The vacuum framework of exposure machine is essential, vacuum degree≥ 90%, only through the vacuum machine to let film tightly with the base substrate, and to ensure that no distortion of the circuits in order to improve accuracy.
(2) After the exposed, should immediately remove the panels, otherwise peripheral vision of light will cause unwanted film in developing of flex circuits.
(3) Working conditions must be met: clean (10,000 scale or higher) operating under yellow light, indoor temperature and humidity (21 ± 1 ℃, 55 ± 5%). Exposed machine should have the cooling air exhaust system.
(4) Exposed, the film emulsion side must face down, and firmly stick the light-sensitive surface side to improve the resolution for circuits.
(5) Exposed machine should regularly calibrate to ensure accurate exposure.
Related Posts:
1. The structure of FPC;
2. Flexible Circuits Production Process;
3. The stiffener of flexible circuits.
FPC Enhance Board
Posted by admin
on October 28, 2010
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FPC enhance board is the stiffener glued to the local position of flexible circuits. It can support the substrate of flexible, and convient to flexible PCB connection, fixed, plug components or other functions. FPC enhanced board material to be choose according to different purposes.
Often flexible PCB need to bending and do not want too much mechanical strength and hardness, but the components or connectors assembly location need the appropriate material for the FPC enhanced board.
Drilling of flexible circuits
Posted by Frank
on October 8, 2010
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Drilling is a flexible circuit an important processing operation, as the flexible circuits material was soft and easy to deformation, It’s different from the rigid printed circuit boards when drilling. The process is as following:
lamination → fixed → drilling → demolition board
lamination: it is going to pile up the copper substrate material or the protective film material together at a certain layers, and at the bottom and top layer with plate and covered tightly with a single-sided adhesive tape together.
CMD Circuits offer you more information about the flexible circuits here blog.
The stiffener of flexible circuits
Posted by admin
on September 30, 2010
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The characteries of flexible circuits are thin, light weight, but easy to happen folding, scars in the process of using, and mechanical strength is small, easy to crack. Stiffener is intended to strengthen the mechanical strength of flex circuits, easy to install surface components.
Stiffener has a variety of types, according to requirements of using, mainly have PET, PI, adhesive, metal or resin reinforcement plate, etc.
There have two ways to press stiffener of flexible circuits:
1. Hot pressing of stiffener: Using high temperature to melt adhesive film of stiffener, then use of appropriate pressure or vacuum to closely fit the stiffener film on the products;
2. Sensitive pressure of stiffener: no heating, products pressure through the cold pressing machine.
The shortcomings of FPC characteristics
Posted by admin
on September 7, 2010
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As your know, Flexible circuits(FPC) provide major benefits over rigid circuit boards, but they also have the shortcomings. Please see below shortcomings of FPC Characteristics:
1. Small mechanical strength,easy to crack;
2. Difficulties in process design;
3. The possibility of re-processing is low;
4. The difficulties for checking;
5. Can’t Carrying heavy parts for single one;
6. Easy to break, beat, wound;
7. Higher cost of the product.
Althrough FPC have these shortcomings, but now more and more widespread use of Flex circuits, more and more advanced technology. We can develop the strong points and avoid the weak points and provide quality goods at competitive cost.