Why PCBs Need the Polyimide Stiffener

Polyimide Stiffener

Flexible PCBs are becoming increasingly popular, with their demand rising in industries ranging from the military and industrial market to the medical industry. Their physical properties make them applicable in many areas which require bendable circuit boards. However, even though this property is crucial to flexible PCBs, it isn’t necessary to have flex PCBs bending adjacent to hole patterns, solder joints, mounted components, and connectors. Due to this reason, technicians have come up with a way to counter this issue using unique components known as stiffeners.

Stiffeners come in 4 types: polyimide, aluminum, stainless steel, and FR4. However, out of these four stiffener types, manufacturers mostly opt to utilize polyimide due to its reliability. However, is this the only feature that makes this stiffener stand out? Or are there other polyimide characteristics that make this stiffener one of a kind?

Stiffeners in a Nutshell

Polyimide Stiffener flex circuit
Polyimide Stiffener flex circuit

Stiffeners are unique PCB components that technicians utilize to add stability and rigidity to a flexible PCB. Doing so adds reliability to this circuit, and it becomes more durable.

Stiffeners might also be utilized for different purposes. For instance, there might be a section in a flex PCB design that needs a specific thickness (one that does not match the thickness of the other board sections) to meet connector specifications when merging various components. Using stiffeners, technicians can quickly achieve the required thickness without harming the board’s integrity. Moreover, a section on a flex PCB might also require a stiffener to constrain a specific bend to a particular location effectively.

Additionally, different working elements in a product or a piece of machinery might rub against a flexible PCB and cause damage to the board via wear and tear. You can utilize a stiffener to add more abrasion resistance and durability.

Moreover, another crucial way technicians utilize stiffeners is by controlling temperature during the assembly process. Using stiffeners, technicians can effectively draw excess heat away from various components, shielding the element from damage.

However, you should note that PCB stiffeners aren’t integral parts of a Printed Circuit Board design. They don’t show up in any PCB design. Instead, these components mainly exist to offer mechanical support to the circuit board and to become crucial in specific instances.

Polyimide Stiffeners

Flex PCB Polyimide Stiffener

Polyimide stiffeners are generally PCB stiffeners made of high-temp polymer crafted into thin film layers. These polyimide stiffener film layers come in varying thicknesses to offer the advantage of variety. Moreover, technicians can also stack multiple layers together to gain a more significant thickness.

The thickness of polyimide stiffeners ranges between 0.001” and 0.009”, even though flex PCBs typically only need a thickness of around 0.005”.

To attach polyimide stiffeners, technicians utilize thermal set adhesives. Moreover, these stiffeners can be used with various connectors and/or components. However, they are mostly needed explicitly for ZIF (Zero Insertion Force) connectors.

Polyimide stiffeners help technicians to effectively meet the required circuit board thickness level as per the specified requirements.

Crucial Functions of Polyimide Stiffeners

FPC Polyimide Stiffener

Polyimide stiffeners are crucial in the PCB industry. And even though they aren’t part of the integral components of PCB designs, they still have multiple functions, which include:

Mechanical Support

Polyimide stiffeners offer impeccable mechanical support when compared to other stiffeners. Therefore, technicians primarily utilize them to boost the mechanical properties of a specific area in a flexible PCB, especially those that contain PTH and surface mount tech components.

Maintaining Thickness

While using Polyimide stiffeners, you can easily maintain the original or authentic thickness of your flexible circuit board while gaining the required thickness of a specific section in the PCB.

Supporting Connectors

Polyimide stiffeners effectively support various PCB components and connectors.

Restricting Flexible Parts

Polyimide stiffeners effectively restrict specific flexible parts of a flex PCB according to the design requirements and provide rigidity to these sections. By using this trick, technicians can tackle various design issues and enhance the board’s durability and reliability.


Polyimide stiffeners meet the Zero Insertion Force or ZIF for various connector specifications.

Enhancing Bend Radius

Polyimide stiffeners effectively enhance the banding radius of circuits at the rigid and flexible intersection. Using this trick, technicians can efficiently eliminate excessive stress on the flexible section of the PCB when flexed.

Retaining and Routing Arrays

Polyimide stiffeners efficiently route and retain arrays when extended to the array.

When should you consider using a Polyimide Stiffener for your flex PCB?

PI Polyimide Stiffener

Polyimide stiffeners are primarily applicable in the following scenarios:

  • If you are looking to place various electrical components on the flexible section of your flex PCB
  • When you have various connectors that require a lot of insertions, and therefore you have to reduce the stress that falls on the PCB pads.
  • Or when you come across design requirements that require you to develop a flat rigid surface on the flexible zone of the PCB to insert surface mount pad components.

Benefits of Using Polyimide Stiffeners

Polyimide stiffeners have a lot of functions, but it is evident that the application of these stiffeners is bound to bring impeccable benefits. So what are some benefits you will gain from utilizing polyimide stiffeners?

Abrasion Resistance

Polyimide stiffeners effectively strengthen the board’s solder joints leading to a boost in the PCB’s abrasion resistance.

Relieving Strain

In addition to boosting the abrasion resistance of PCBs, these components also help relieve the strain on flexible sections of a flex PCB. Moreover, it also helps with the dissipation of heat.

Tips to help you select the Best Polyimide Stiffener Manufacturing Company

Selecting the best polyimide stiffener manufacturing company takes you a step closer to making your flexible PCB more durable and efficient. However, since there are so many polyimide stiffener manufacturing companies, how can you know the right one for your project? You can utilize the following criteria:

  • Try to review the company profile to see whether they offer diverse and quality polyimide stiffener services and products.
  • Secondly, check on their QMS (Quality Management System) certs to learn more about their resources, capacity, and pedigree to effectively produce and source quality polyimide stiffener products.
  • You should also check on the company’s technological flexibility and adoption.
  • Lastly, check on the cost.


Polyimide stiffeners are becoming popular in the PCB market with the growing need for flexible and semi-flex printed circuit boards. Moreover, their application areas grow daily due to their efficiency and durability. Additionally, these stiffeners play vital roles in maintaining the durability of flex PCB and providing added mechanical support to the boards. Therefore, if you want to work on a project requiring PCB stiffeners, you should try this impeccable circuit board stiffener.

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