What Is FPC Stiffener? Everything You Need To Know

FR4 stiffener

FPCBs have become more and more common recently. However, they have several drawbacks. The boards can be challenging to handle at times because they are excessively pliable, which is a huge difficulty. FPCBs are frequently equipped with stiffeners, which provide the board’s stiffness and stability, to get around this.

The use of stiffeners while creating FPCBs is essential since it enhances the boards’ handling and stability. The stiffeners act as a link between the parts on the board and can be composed of a variety of materials, including metal. They come in a variety of thicknesses and shapes to meet the intended function and location, and they also help dissipate heat.

Continue reading to gain a thorough understanding of FPC stiffeners and their variety of uses. Our article provides comprehensive information covering the many shapes, sizes, and uses of FPC stiffeners.

What is a FPC Stiffener?

An FPC stiffener is a passive component that improves the bond between two circuit elements. It doesn’t display any energetic electrical properties when used as an electronic material. The stiffener, which is typically made of metal, provides both mechanical strength and thermal control.

A Printed Circuit Board (PCB functionality)’s and dependability are elevated when FPC stiffeners are added. The use of FPC stiffeners is not required for all flexible circuits, which is an important point to remember. The particular requirements and specifications of the circuit will determine whether stiffeners are required.

Importance of FPC Stiffener

Since FPC stiffeners don’t directly affect the electronics, their use in a circuit could seem unnecessary. However, several considerations make them essential for assuring the circuit’s greatest performance and durability. The following are a few justifications for the significance of FPC stiffeners:

  • The chance of breaking increases when force is applied to a solder joint or pad because all the tension is concentrated at the point of connection. The use of a stronger stiffener layer strengthens the circuit and improves its capacity to withstand force to lessen this risk.
  • The tiny components that are fastened to the pad can be stabilized by incorporating a support plate or by applying a stiffener. Without this support, the circuit board can be excessively malleable and prone to parts breaking loose or tumbling off. The likelihood of de-mounting is reduced by the stability that stiffeners provide.

Materials for Making FPC Stiffener

Full PCB Manufacturing

The metallic materials used in stiffeners come in a variety, and all have excellent heat dissipation. It is crucial to choose the right stiffener material because each option has unique advantages that should be considered according to the requirements of the particular circuit.

We shall examine some of the most popular stiffener materials in this article.

· Polyimide Stiffeners

“The term “gold fingers” refers to a sort of stiffener that is frequently employed and has come to represent convenience and adaptability. Due to their simple compatibility with ZIF connectors, these stiffeners are a favored option among designers & engineers alike. These stiffeners’ usage of polyimide material improves their flexibility and reshapes the point of contact, greatly strengthening the components without introducing extra mass.

They are perfect for use in ZIF connector applications since they may be integrated into the circuit board at any moment, even after initial assembly. Additionally, these stiffeners may be added without negatively impacting the functionality of the circuit, provided the PCB is not laminated.

· FR-4 Stiffeners

The “CCL of stiffeners”—FR-4 stiffeners—can be easily affixed to perforated plates. When used on one side of the board, they offer a smooth surface, enclosing the circuit in a secure perimeter. The FR-4 stiffeners aid in maintaining the holes’ alignment by limiting their size to 0.3 mm or less. This helps shield the circuit board from further harm.

· Aluminum & Stainless Steel Stiffeners

Stiffeners made of aluminum and stainless steel is crucial for applications where corrosion resistance is required. Before being included in the circuit, these materials must go through several procedures, such as milling, drilling, and shaping.

Laser cutting, registration & pre-cutting are a few of the processes in the lengthy insertion procedure. Despite the extra work and expense, the finished product is a robust circuit, making it a worthwhile investment.

· Multiple PCB Stiffener

PCB Stiffener

In some circumstances, strengthening the solder joints is required to retain their strength. The circuit may become too thick if only one material is used for this purpose. A stacking strategy utilizing many FPC stiffeners can be used to balance strength and thickness. These multi-layer FPC stiffeners typically have the following stacking order:

  • FR-4
    • Adhesive
    • Polyimide
    • Copper
    • Polyimide
    • Copper
    • Polyimide

Features To consider while using FPC Stiffener 

Let’s first grasp the properties of an FPC, also known as a flex circuit, before delving further into the topic of FPC stiffeners. One of the most important factors to take into account when adding a stiffener to an FPC is accurate alignment and, if necessary, strengthening it with a plate. As opposed to a single-layer application, where the stiffener is typically placed on the same side as the flex circuit, in some circumstances, it may be necessary to place it on both sides to achieve greater stability. This involves multiple lamination cycles and is, therefore, more expensive. Therefore, it’s essential to carefully assess your unique needs and choose the best course of action.

How Are FPC Stiffeners Used?

A key component in the creation of a flexible printed circuit board is the usage of FPC stiffeners. The producers want to make sure that the stiffeners are used precisely, reliably, and over a lengthy period. To accomplish this, stiffeners are frequently added to the plated-through holes that are located on the same side of the board as the other components.

A thorough and careful approach is needed when putting the pieces together, with an emphasis on designing configurations that will be simple to work with in the long run. There are two typical methods for adding stiffeners to an FPC, each with distinct advantages and disadvantages.

· Pressure-Sensitive Adhesives

Consumer gadgets like computers, televisions, and similar devices use pressure-attached stiffeners. They are straightforward to install and have a limited amount of strength, making removal simple without harming the adjacent components. Due to the minimal amount of stress it can withstand, this kind of FPC stiffener is appropriate for use in such devices. These stiffeners are not only reasonably priced but also relatively simple to add.

· Thermal Bonding

A safe choice for high-end applications that demand strength and endurance is the heat-activated FPC stiffener. High heat and pressure are used to create an unbreakable link between the stiffener and the flex circuit, making it suited for demanding applications like avionics and the military. The stiffener won’t peel off easily and will stay in place, ensuring the stability of the circuit, even if this bonding procedure is time-consuming and expensive. The drawback of this tight bonding is that removing the stiffener can potentially harm adjacent circuit components.


Including an FPC stiffener is the best approach to guarantee a fluid functioning and perfect assembly of your flexible circuit. With so many different layouts and choices, it’s crucial to talk with your manufacturer about which one best suit your requirements. To guarantee you obtain a product that fully satisfies your needs be sure to investigate all the trustworthy possibilities that are offered.

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