Printed circuit boards (PCBs) are some of the common things you will come across when developing your device or solution.
You will have to decide early on whether to use Flex PCBs (more on that later) or rigid PCBs or a hybrid of both, the rigid-flex PCBs. Your decision, however, will depend on several factors which we would look at in this post.
But first, let?s define what these terms are.
What are Flex PCBs?
From the name, it is evident that these types of PCBs are flexible. Though you may have seen where names like flex boards, flexible circuit boards, flexible electronics were used to describe these types of PCBs, they are all referring to the same kind of circuit board.
The name, however, stems from their ability to be shaped into any configuration. That is, you can bend, crease, fold, twist them into different shapes, and they would still retain their integrity.
What are rigid PCBs?
As the name implies, these type of circuit boards is not flexible. They are solid and often comes either as single or double-sided or multilayered PCB.
Their rigidity is because of a solid substrate, the FR4 stiffener which acts as the base material for the board. It is important to note that once manufactured; the rigid PCB cannot be modified again.
These are hybrid printed circuit boards that combine the best of both worlds. A rigid-flex PCB co-opts the advantages of both the flex and rigid circuit boards while eliminating their limitations.
So, when do you use Flex PCBs vs Rigid-Flex PCBs?
Here are some cases when using either a flex PCB or rigid-flex PCB is desirable:
For lightweight, wearable consumer products
Today?s consumers increasingly prefer thin, lightweight devices than bulky ones that take up a lot of space. Using flex PCBs sure satisfies this new trend as they are flexible enough to accommodate this new design taste.
Flex PCBs also affords you the leeway to design circuit boards around products instead of struggling to fit products in with board designs.
When high power application is needed
As a result of the design features of flex circuits they can be made to have high current carrying power than their rigid counterparts.
The polyimide dielectrics used as insulators in the circuit not only allows flex PBC to bend and resist contamination but also has the ability to withstand high temperatures which is necessary in high power applications.
When wiring space is limited
Today more and more products are miniaturized ? are getting smaller in size, yet needing higher processing powers. The implication is that, while the need for more wiring and circuitry designs are on the increase, available real-estate to accommodate these demands on printed circuit boards are increasingly getting limited.
Using rigid PCBs is out of it. They are inflexible and takes up a lot of limited space to design. Flex circuits, on the other hand, are ideal wiring solutions to get around the need for space.
With flex circuits one can easily design PCBs for spaces where rigid-flex boards cannot fit.
When cost is a concern
Flex PCBs are relatively less expensive at the individual part level compared to rigid-flex designs. The high cost of rigid-flex PCBs can be attributed to the extra processes and material needed to manufacture the board.
That?s not to say, however, that rigid-flex based solutions are more expensive than flex when all production costs for the final product are accounted for.
In fact, the improved performance of the rigid-flex solution can in the long-term offset any extra initial cost.
Higher-level performance and reliability are a priority
Rigid-flex PCBs eliminates the need for connectors, flexible cables and discrete wiring required in flex only designs while at the same time, integrating the versatility of flex boards which ultimately enhances its performance.
Rigid-flex based designs are ideal for products which are likely to be exposed to high-level vibrations or repeated shock over their lifetime as they are reliable and able to handle the harsh environment without failing.
Need to decrease assembly time
As mentioned earlier, rigid-flex circuits reduce the need for connectors which in turn lowers the purchasing cost of the PCB.
By embedding the flex circuit inside the PCB, itself to form the rigid-flex hybrid, you not only reduce manufacturing time but also the time it would have taken to assembly the whole product.
While flex and rigid-flex PCBs fundamentally perform the same function, there are use cases where each is best suited than the other.