Aluminum Flex-Rigid PCB: All You Need To Know

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Oakley Mae

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An aluminum flex-rigid PCB is a hybrid board that blends the thermal conductivity and rigidity of aluminum boards and the flexibility of aluminum flexible boards.

Generally, the boards find application in high-performance electronics that requires high conductivity but have limited space. 

Normally, the rigid part of this PCB consists of aluminum, while the flexible parts contain a polyimide material.

Experts say aluminum flex-rigid circuit boards provide reduced impedance and high signal integrity. 

However, you might not know many other aspects of aluminum flex-rigid PCBs, including their design guidelines, limitations, and benefits.

This article highlights this and more to help you handle these circuit boards from the point of understanding. Let’s get rolling. 

Table of Contents

What Are Aluminum Flex-Rigid PCB

As mentioned in our introduction, aluminum flex-rigid PCBs are hybrid boards that blend the characteristics of rigid aluminum boards with those of aluminum flexible PCBs.

This includes thermal conductivity and rigidity for aluminum boards and high flexibility for flexible aluminum PCBs. 

The design of aluminum flex-rigid PCBs happens in 3D space, and you’ll find it more difficult than that of rigid circuit boards.

Therefore, designers get more spacial efficiency and the ability to fold and twist the boards to their preferred shapes. 

Normally, aluminum flex-rigid boards experience a reduced impedance and high signal integrity.

As a result, they’re common in high-performance and high-speed electronic devices that demand high conductivity but contain limited space.

Generally, you can use them in the medical, automotive, wearable, consumer electronics, and aerospace industries.

Aluminum Flex-Rigid PCB Types

An electronic circuit board

(An electronic circuit board)

We have several aluminum flex-rigid PCB types, each with unique features to meet specific requirements.

This section highlights the different types: 

Single-sided Flex-rigid PCB: From the name, we can tell that this PCB has a single rigid aluminum layer and another flexible layer.

Therefore, the boards are very thin, and you can use them in applications with very tight spaces. 

Double-sided Flex-rigid PCB: These boards have two rigid aluminum layers and two flexible layers.

Generally, these circuit boards can bend in all directions, making them ideal for applications that require high flexibility. 

Multi-layer Flex-rigid PCB: This circuit board has more than two rigid aluminum and flexible layers.

Therefore, they support greater functionality and are common in high-density applications. 

Hybrid Flex-rigid PCB: Finally, the hybrid option combines the characteristics of aluminum and other materials like FR-4 to develop high-performance boards.

These boards are common in applications where aluminum alone won’t work well, including high-temperature uses. 

Aluminum Flex-Rigid PCB Benefits

A white aluminum printed circuit board

(A white aluminum printed circuit board)

Manufacturers prefer using aluminum flex-rigid circuit boards for the following reasons:

Lightweight and compact: Besides being highly flexible, aluminum flex-rigid boards are also lightweight.

Therefore, they’re compact, thus reducing the packaging size. 

Flexibility: As we mentioned, aluminum flex-rigid PCBs have the characteristics of both flexible and rigid circuit boards.

Therefore, you can employ them to fit smaller areas and create compact electronic devices.

For example, most manufacturers are using the board in wearables like smartwatches. 

Reliable: Aluminum flex-rigid boards don’t have solder joints and solder crimps.

Therefore, cases of failure are rare in these boards.

Also, it guarantees the reliability and integrity of connections. 

Great thermal stability: Besides aluminum, these circuit boards also use polyimide, which has excellent thermal stability.

Therefore, you can use them in devices that work under high temperatures and extreme conditions, like military and defense applications. 

Reduces PCB failure: The blending of rigid and flexible PCBs limits the number of connections.

As a result, failure cases become minimal. 

Cost Effective: Aluminum flex-rigid circuit boards have a low material requirement making them less costly.

Generally, they need fewer materials making the whole manufacturing and procurement process cost-effective. 

Limitations of Aluminum Flex-Rigid PCB

Although flex-rigid circuit boards have the benefits we highlighted above, there are also limitations worth understanding. 

They need elaborate manufacturing: As mentioned, flex-rigid circuit boards require both flexible and rigid manufacturing materials.

Therefore, you’ll find the process to be elaborate and time-consuming. 

Labor-intensive production: Apart from the board’s material-intensive manufacturing process, you’ll also find it labor-intensive.

We can attribute this to flex-rigid board substrates’ inherent variations and sensitive nature. 

Complex manufacturing process: You must use effective software when manufacturing flex-rigid circuit boards.

Such software requires more expertise and might even come at an extra cost.

All these make the flex-rigid circuit board complex to manufacture. 

Aluminum Flex-Rigid PCB Design Guidelines

An engineer designing a circuit board

(An engineer designing a circuit board)

While designing aluminum flex-rigid circuit boards, you should abide by certain design guidelines and rules.

For example, ensure they’re not bent every time you make corners.

And if you must have a bent, ensure it’s curved and not sharp. 

Let’s focus on how you should handle the different elements below: 

Trace width: While calculating the trace width, ensure there are precision and accurate results for the trace width and spacing between the flexible parts.

Moreover, ensure the solder pads are complete in teardrop or rounded styles. 

Annular rings and soldering surface: Ensure that these two aspects are large.

This is possible using different stiffeners.

Moreover, apply coverlay on the PCB surface to protect and insulate the conductor.

Finally, the pads should have anchoring spurs. 

Vias: Metalize the plated vias using the through holes that connect the conductive layer and flexible circuit.

However, never use vias in areas that require bending since it could cause damage.

Understanding OEM Aluminum Flex-Rigid PCB

The circuit board fabrication process

(The circuit board fabrication process)

To get deeper into aluminum flex-rigid PCBs, we have what we call OEM flex-rigid PCBs.

In short, these are Original Equipment Manufacturer (OEM) aluminum flex-rigid PCBs which combine flexible and rigid boards to offer specialized service.

Manufacturers combine rigid and flexible layers using adhesive to form a single complex circuit board. 

Interestingly, you can customize these PCBs to meet your specific design requirements with an option to adjust the surface finish, thickness, and number of layers.

Moreover, you can create them using several through-hole and surface mount components.

We recommend OEM aluminum flex-rigid PCBs in situations where production efficiency and cost are major considerations. 

FAQs

Does aluminum flex-rigid PCB have to meet OC certification requirements?

The need for an aluminum flex-rigid board to meet OC certifications depends on the application and specific regulations that govern the industry you intend to apply the board.

In short, OC certifications involve a process that a third-party certification validation company goes through to determine whether a product meets performance and safety standards. 

For example, if you intend to use the circuit board in the medical industry, it might have to abide by FDA safety standards.

Similarly, all the circuit boards meant for military application should strictly abide by the defense ministry performance standards. 

What are the applications of aluminum flex-rigid PCB?

If we were to mention all the applications of aluminum flex-rigid circuit boards, we’d lose count.

But generally, the common application sectors include the following:

  • Consumer appliances
  • Automotive industry
  • Aerospace industry
  • Telecommunication industry
  • Medical industry
  • Military equipment

Final Remarks

In conclusion, aluminum flex-rigid circuit boards provide versatile electronic solutions with reliability and better performance than traditional PCBS.

Generally, combining flexible and rigid materials creates a hybrid product that withstands mechanical stress and supports high-power applications. 

Moreover, aluminum PCBs can dissipate heat faster through the aluminum layer, making them perfect for thermal management applications.

And very few circuit boards can compete with the cost-effective nature of aluminum flex-rigid circuit boards.

Therefore, we recommend these products to any user without hesitation.