Tag Archives: Flexible Circuits

The issue of flexible pcb cut-out areas uneven

Posted by on June 21, 2012 No comments

When you make flexible pcb samples, and it with many cut-out inside, do you have the uneven issue for the cut-out areas?

We analyzed it and have the following reasons:
1, the cut-outs too much, making with a little difficulty;
2, make samples with simple tooling, so more or less will be a bit uneven phenomenon.

The solution to the problem is actually very simple, use laser cutting, or set up hard tooling. As it’s just the flexible pcb samples stage, in order to save costs, we recommend using a laser cutting, the cost is only increased by a little bit.

If you have any doubts of flexible pcb production process, please feel free to contact us.

The thickness of Coverlayer

Posted by on June 25, 2011 No comments

There are normal three kinds of coverlayer of flexible circuits(flexible pcb), please see below thickness:

1)12.5UM:     PI：12.5UM    AD：15UM           Thickness：27.5UM

                         PI：12.5UM    AD：25UM           Thickness ：37.5UM
             
2)  25UM:     PI：25UM     AD：25UM            Thickness：55UM

If you need any other information of flexible circuits and flexible pcb, please contact us anytime.

The problems appear in etching process

Posted by on November 23, 2010 No comments

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 Production Process

Posted by on May 20, 2010 No comments

Last time we talk about the PCB production process, now please see the below form of flexible circuits production process for you study.

CMD Circuits has a very strict quality control system to ensure to make high quality flexible circuits. Please feel free to contact us for any queries.

Copper foil features of flexible circuits

Posted by on January 12, 2010 No comments

Here, let’s to know the more details of copper foil is used in the flexible circuits. The cooper foil is very improtant part of flexible circuits.

1. There are two kinds of copper foil:
1>. rolled annealed copper foil(RA-copper)
2>. electrodeposited cooper foil(ED-copper)

2. The thickness:
1>. normally use 1/3oz, 1/2oz,1oz and 2oz four kinds;
2>. RA-copper: 1oz, 1/2oz, 1/3 oz or less thickness, but higher cost.

3. flexibility:
Rolled annealed copper foil is of high strength and can stand bending, two times for electrodeposited cooper.

Now, I think you know the Copper foil features of circuit boards more details. Ok, if you need more information, please do feel free to contact us.

What types of flexible circuits are available?

Posted by on March 9, 2009 No comments

There are four basic types of flexible circuits(FPC) are available. These four types of flexible circuits can be used in different combinations to solve most every interconnection design problem.

1. The simplest flexible circuit is single-sided FPC. They provide maximum flexibility for dynamic applications and can withstand hundreds of millions of flex cycles. These simple circuits are also the most easily adaptable to SMT, TAB, and other developments in circuit technology.

2. Double-sided FPC consists of double-sided copper clad material with top and bottom cover films. The ability to interconnect between sides using through-hole plating helps double-sided circuits carry complex designs, and still maintain flexibility.

3. Multilayer FPC are ideal for complex, highly populated design requirements. Large numbers of conductors can be designed into a small package. Maybe flexibility will be somewhat limited by the number of layers in the design. Multilayer circuits are also the ideal problem-solving technology when confronted with design challenges like unavoidable crossovers, specific impedance requirements, elimination of crosstalk in sensitive circuits, additional shielding or ground planes, and high component density.

4. Rigid-Flex circuits are circuits combination of Rigid circuit and Flex circuits. So it have both the advantage of each other and it’s newest types used in various applications.

For more information of the flexible circuits, please do feel free to contact us.

The performances of flexible circuits

Posted by on August 6, 2008 No comments

This time let’s to know the performances of flexible circuits.

(1) Base material:
PI(Polyimide) is the most common used, which is a kind of macromolecule material of high temperature proof and high strength, invented by Dupont. The polyimide made by Dupont is called Kapton. Besides some polyimide made in Japan can also be found. Its price is much lower. Polyimide can bear 10 seconds of high temperature of 400 degree centigrade. Its tensile strength is 15,000~30,000 PSI. The base material with 25um thickness is the cheapest and the most popular one. If we need the circuit board to be more rigid, we should choose 50um. Otherwise, if we need the circuit boards to be more flexible, then choose 13um.

(2) Adhesive:
It is divided into epoxy resin and polyethylene, they are all thermosetting adhesive. The polyethylene’s strength is lower. If we hope the circuit boards to be more flexible, then choose polyethylene. The thicker the base material and the adhesiveon it is , the more rigid the circuit boards are. If the circuit boards have to be bent in a large area, we should choose thinner base material and adhesive so as to reduce the stress on the surface of the copper, then lower appearance of micro crack.

(3) Copper:
It is divided into rolled annealed copper foil and electrodeposited cooper foil. Rolled annealed copper foil is of high strength and can stand bending, but its price is higher. Electrodeposited copper foil is much cheaper, but of low strength, easier to be bent.

When we choose to use rolled annealed copper foil, we should pay attention to the direction of the copper. The direction of the copper has to be the same with the bending direction of the circuit boards.

(4) Coverlay with adhesive:
25um coverlay would make the circuit board more rigid, but it is cheaper. Therefore to the circuit board needing to be bent greatly, we’d better choose 13um coverlay.

The adhesive is also divided into epoxy resin and polyethylene. The FPC using epoxy is more rigid. After thermosetting, there are some adhesive squeezed out at the edge of the coverlay. If the soldering pads are larger than the hole on the coverlay, the adhesive squeeze out would reduce the size of the soldering pads and lead to irregular edge. Therefore, we’d better choose 13um adhesive.

These are more details about the performances of the flexible circuits. If you still need more information, please do fell to contact us.

The package of flexible circuits

Posted by on August 13, 2006 No comments

The most common package of flexible circuits(FPC) is using the paper strips to fix on the rigid board. Every part is to pile up 10~20pcs flexible circuits together. We should avoid using tape, because if the chemical substances in the tape adhesives oozes, the terminal would be easy to be oxidized and change color. The base material is polyimide which is easy to absorb moisture.

The flexible circuits together with silica gel, etc. the drying agents have to be put into the polythene bag and sealed. Then put it into the cartons together with cushion material.

Due to special shapes of Flexible PCB, we should adopt different packages according to different shapes.

Where would we use Flexible Circuits?

Posted by on June 4, 2005 No comments

Where would we use flexible circuits? Flexible circuits are used as an innovative interconnect solution offering point to point connection. Flexible and flex-rigid circuits have long been used in numerous industry sectors including defence, electronic data processing, aerospace, communications, medical, automotive/motor sport, industrial and consumer. Applications are wide ranging, from dishwashers to fighter jet instrumentation.

If you need to know more information, please don’t hesitate to contact us.