Flexible Circuits-9 Factors you need to Consider When Designing

Flexible printed circuits that find substantial use in nearly all electronic devices are as much as mechanical devices as they are electronic devices. Unlike rigid printed circuit boards, flexible printed circuit boards can flex, bend, or contort to fit the final assembly process properly.

In the flexible circuits' manufacture, plenty of successful designs get forgotten with designers looking to handle the next challenge.

However, failures stick in the mind of a designer for many years. Competent designers are those who learn from their mistakes and ensure that they never repeat those mistakes. So, what are the do and do not inflexible circuit design? Here are 9 of them that flexible circuit designers need to be aware of all the time.

The exquisite flexible PCB board

1. The Flexible Circuit Conductors Must be Arranged

As you may be aware, flexible circuits are slightly different from rigid printed circuit boards. Flexible circuits can easily twist, stretch or bend, unlike rigid ones. For this reason, when designing a flex circuit board, it is essential to be cautious towards the conductor's arrangement.

If you are a designer dealing with the manufacture of a flexible circuit, you must ensure that you are very keen when arranging the conductors. Incorrect or inadequate conductor setting is a hazardous process that can cause a severe failure of the entire circuit, especially during board flexing.

If possible, the conductors used here should pass through curved and curved areas. By doing this, there is a high chance of minimizing stress on the conductors during flexing while ensuring that you maximize your flexible circuit's life.

a close inspected flexible PCB

2. Correctly Set the Bending Area at the Initial Stage

Designers need to comprehend the bendability of their flexible printed circuit boards when designing flexible printed circuit boards. Here, it is vital to understand two crucial aspects of bending. First, how many times the board will be turning, and secondly, what the council can bend.

The board's number of times can flex, and use will determine whether the board is dynamic or static. When manufacturing a flexible printed circuit board, manufacturers should ensure that they rightly set the bending area during the initial stages of making them.

Both the minimum and the maximum bending have to be set in the right manner way back in the manufacturing process to ensure that a board functions as desired. For instance, bend radius, or the smallest amount of bendiness, must be appropriately identified way early in the design.

It will ensure that the design phase prepares to create a flexible circuit that can bend without damaging the materials inside.

 flexible PCB connecting circuit

3. Notches and Slots in Curved Areas

When designing how to make notches around your PCB's curved or bend areas, your drawing tools will matter a lot as a designer. You will have to have a deep understanding of your Arc tool to create three or four bridging sections where you will likely place the slots. You will then have to put small holes around the bridges' narrowest point to make room for the slots.

Once you have the board outline ready, you can now easily arrange these bridged sections to achieve a polygonal edge. These edges will generally fit your desired curved PCBs and make room for the notches and slots you want to create. It will now be an easy task of cutting out the slots from the edges.

Another trick would have a circular board outline on your board outline layer. The circle's two halves can be manipulated with a radius to meet your notches' size individually.

Flexible PCB with notches on the curved area

4. Flexible Routing

When routing comes to electronic design, there is a step known as wire routing or called the path. The path is an essential step in the design of printed circuit boards. It builds a preceding step known as placement, which goes a long way into determining every active element or component's location on a printed circuit board.

It does not concern features that will later cause discontinuities, especially in a bending area. When a flexible circuit gets bent or stretched, compressing forces can cause discontinuity, leading to fractures in insulation or the conductors. Again, it is better to avoid beams and also minimize the ability of copper circuits to thin.

example of flexible routing in PCB

5. Risks of Flexible Through Holes

Through-hole technology involves mounting solutions for electronic components, in which leads mounted into holes drilled on the PCB and then soldered to pads on both sides of the board. This exercise can place manually or using an automated machine.

There are several risks associated with through-hole. When designing a printed circuit board, it is essential to ensure that plated through-holes are kept out of areas that regularly flex or bend—the through-hole subject shear forces due to compression and tension between the outer and inner bends.

Further, the need to ensure the same surface and another side surface of the same used in the use side of the through-hole. Additionally, the surface finish on one team needs to be the same as the one used on the other side. As a flexible printed circuit board designer, it is advisable not to design through-holes in bend regions and avoid direct force.

incorporation of Flexible designs and through-hole technology

6. Flexible Layer Placement for Multilayer Boards

A multilayer printed circuit board comprises three or more layers, which we can distinguish by referring to PHT through holes. Flexible multilayer printed circuit boards are excellent for applications that require increased circuit density, or applications where circuit density and layout can not be included or used in a single layer.

When designing multilayer printed circuit boards, it is essential to pay detailed attention to layer placement. Layer placement on a flexible printed circuit board is one of the most complicated processes that require a robust technical nature. A slight mistake will affect the functionality of the entire board.

There is a common saying, especially when designing printed circuit boards the says the design of printed circuit boards is 10% routing, but 90% placement. Scrutinized, this is very accurate. By taking the time to place all the components correctly, rest assured of having a printed circuit board that will function as desired.

For multilayer flexible printed circuit boards, poor placement of layers comes with busted boards' risk, very ugly aesthetics, and too many hours wasted. Even though there is no right way to place components, there are some layout rules that designers need to pay attention to during the placement of elements.

It is, however, advisable to avoid placing components or parts that make up a printed circuit board on the solder side of the PCB. Although this process can be a daunting challenge for many designers, how to place the circuit board will significantly help manufacture the circuit board and the circuit board's original design quality.

multilayer red-colored flexible PCB

7. Do not Specify the Thickness of the Adhesive on the Drawing

When designing flexible printed circuit boards, it is good not to determine adhesive width on the picture. Designers need to be aware that the description only needs to determine the flexible printed circuit board's overall width and the total width of some of the critical dielectrics that impact impedance.

Designers need to come up with drawing packages for their flexible printed circuit designs. However, while it is essential to specify some essential features, as a designer, you should not entirely over-specify the non-critical features or elements of a drawing. The reason for this is to ensure that you minimize your costs.

8. Do Not Stack Conductors on Multilayer Boards

When designing multilayer printed circuit boards, ensure that you do not stack conductors. A majority of flexible printed circuit board designers prefer to return and signal lines on top of each other across adjacent layers as a means of minimizing electromagnetic interference or EMI in short.

Doing so will eventually result in a thicker circuit, an aspect that brings about what is known as an “I-beam” effect. If electromagnetic reduction gets used, line pairs may be staggered to minimize the impact.

9. Selection of Cover Material

Lifetime and the printed circuit board's overall performance largely depends on choosing the cover material used in the manufacture of a printed circuit board. When selecting the cover material, it is essential to choose those materials that suit the circuit board's applicability.

When it comes to selecting the cover material, ensure that you put quality into consideration. Whether you use flexible printed circuit boards for home or industrial use, quality is paramount.

When selecting cover materials for printed circuit boards, ensure that the selected content is chosen based on appropriate performance, specification, and the board's environment.

Summary:

Flex printed circuit boards are known to be exceptional and long-lasting units that have the ability to make all electronic components better. However, there are plenty of challenges when it comes to designing them. There are essential steps to include and some things to avoid during the design process.

Fortunately, we at OurPCB have made everything easy for you. As a reliable manufacturer, we can easily design flex PCBs for you, following all the design rules. We at OurPCB provide everything that you require for flexible PCBs, including flexible PCB assembly, wire harness procedure, and fast completion of your orders.