5 Things About Rigid Flex PCB Manufacturing Technology

Rigid-flex PCB is getting popular, all because of their ability to tick the right boxes. Quite sophisticated in their approach, such a PCB is the right combination of flexible and rigid PCB.

It is this quality that flex-rigid manufacturing technology is making headlines. So what is it? Here, we will reveal some of the interesting facts about this technology.

With that in mind, let us explore some exciting things you must know about rigid and flexible manufacturing. But before that, let us understand what rigid-flex PCB is.

1. What Are Rigid-Flex PCB?

As is indicated by its name, a flex-rigid PCB is a type of printed circuit board that consists of the goodness of both flexible substrate material and rigid PCB.
Reportedly, PCB rigid-flex offers a range of benefits when compared to its counterparts. They are comparatively thinner, weigh lighter, capable of bending dynamically, and can assemble 3D interconnection. What is more, they allow you to exercise a higher degree of freedom as far as mechanical and electronic design is concerned.

Not only this, but they are also space-saving and are the right fit for today are compact devices.

With that in mind, let us explore some exciting things you must know about rigid and flexible manufacturing.

(Caption: Rigid-Flex Printed Circuit Board with SMD & IC mounted part on board)

2.Things About Rigid-Flex PCB Manufacturing Technology

Material

As is the case with any other PCB, the performance of rigid-flex PCB, to no small extent, is also determined by their substrate material.

Typically, a flexible dielectric film made of polyester is in the low-end products. In contrast, more advanced products like those used in the military and aerospace purposes use fluoropolymer and polyimide.

If we compare these three types of flexible materials, polyimide tops the list for having the highest dielectric constant. It can also withstand high temperatures and offers excellent mechanical and electrical properties. However, it can absorb moisture quickly and is quite expensive.

Talking about polyimide, it also performs well, but polyester offers pretty bad temperature resistance.

If you want to operate the product at high frequencies, polytetrafluoroethylene offers a low dielectric constant and serves the purpose well.

In terms of adhesive films, the best materials for this purpose include polyester, acrylic, and epoxy because of the high degree of flexibility. They also have excellent adhesion and are relatively resistant to heat and chemicals.
But here is the catch. These materials have a significant coefficient of thermal expansion, and this is why the internal thickness of the film should not exceed 0.05 mm.

(Research on PCB material issues)

3.Flex-rigid PCB Pricing

When we are talking about flex-rigid PCB cost comparison, it is essential to mention here that a rigid PCB is used instead of a flex circuit more often than not.

You might argue that the costs associated with designing and manufacturing flexible circuits are lower. True. But contrary to this, manufacturers are still expected to pay more when compared to a rigid PCB configuration. Regarding the price, we certainly hope that we can minimize our production costs. But because the circuit design is more complicated, we have to face higher production costs. However, you can negotiate with your PCB supplier for maximum benefits.

Further, there has been a significant dip in the prices of both flexible PCB and rigid PCB. It has not improved the conditions for flexible PCB, though, but only worsened them so much that when rigid PCB could serve the purpose, it will likely be used.

(High-tech PCB electronic production)

4.Flex-rigid PCB Types Of Methods

Rigid and flexible PCB can replace the wiring harness and connector, thereby solving the problem of loose contact and heat dissipation, thereby improving the device's reliability. The plastic part can be bent at any angle, and the entire PCB is excellent in electrical and mechanical properties. It may be produced through a series of rigid-flex PCB manufacturing techniques. We will introduce three types of production next so that you can understand this knowledge more clearly.

Window opening method

It is a method in which rigid-flex PCB with a core board structure makes the most out of mold punching to get rid of the rigid core in a flexible construction. It is the production of rigid-flex PCB with the help of lamination.

The copper foil etching method

It is another excellent method used to produce flex-rigid PCB. Here, PCB copper foil structures for making the flexible portion of the PCB. This is an exciting process.

The positive and negative depth control method

In this process, a blind groove was created in advance on the rigid board next to the flexible board. After proper lamination, the blind grove is combined during molding using the mechanical depth control method. Then remove the rigid plate in the window position, and the flexible portion is exposed.

(Caption: Blank square SMD microchip mounted on a colorful cyan glowing print board)

5.Flex-rigid PCB Processes

The emergence of rigid, flexible PCBs can effectively reduce electronic products' volume and quality by replacing wire harnesses and connectors commonly used in electronic products. Also, the rigid and flexible PCB can solve the contact and muscular heat problems caused by the wiring harness and the connector, thereby significantly improving the device's reliability.

Rigid printed circuit board technology and flexible printed circuit board technology.

For instance, the flexible substrate circuit and rigid substrate circuit are etched together and then connected by PTH to develop a rigid-flex PCB.

Let's take a look at the various technologies that do the job:

Drilling technology

Here, by making effective use to drill a hole cover and the base plate. We have to check the drill bit quality and other drilling parameters properly. It will help you in obtaining a perfect hole wall.

To prevent the nail head from appearing on the flexible substrate, You should choose sharp drill bits and replace them with the number of holes you drill to ensure they are always sharp.

In addition to the sharpness of drill bits, pay close attention to the rotation speed and feed speed of the drill. If the feed speed is too slow, this will heat the PCB and produce a lot of drilling waste. Similarly, if it is too fast, it might lead to the production of a nailhead.

Desmear

When producing rigid and flexible PCB, once drilling, it is possible to provide drilling contamination on the hole wall—the degree to which this contamination depends on the type of materials you have chosen for building substrates.

As a rigid-flex PCB is composed of two kinds of materials: rigid and flexible, all the associated materials melt and get attached to the fiber wall during the drilling process. If this contamination is not taken care of in time, it will fail the copper layer plating and negatively impact the binding force between the hole wall and inner layers.

Electroless plating

Quite predictably, in this method, a layer of metal is deposited in the hole after the chemical process drills it. The hole is then metalized by thickening the metal layer. This is done by initiating chemical oxidation and reduction reaction.

In this process, copper ions are reduced to copper, and the reducing agent releases electrons that get oxidized.

(Multiplied printed circuit boards PCB isolated on the white background. )

Conclusion

Although rigid-flex PCB is getting popular, not all rigid-flex PCB manufacturers do it right. And the ones that do are not capable of doing this affordably. Although the industry is still trying to improve its production techniques, there are some technical problems.
Expected in the next few years, and the industry will soon overcome all these challenges. That said, it is essential to choose the right PCB manufacturing company to get the desired results.

OurPCB can help you. Talk to us today to learn more about our rigid-flex PCB manufacturing process.