The Ultimate guide To PCB Stiffeners

• Make the connector areas stable: Connector areas on flex PCBs can cause mechanical stress during connector insertion and removal. That is why stiffeners are used in these areas to provide the necessary rigidity, so that the connectors remain securely attached and the solder joints do not break or crack under repeated stress.
• Prevent delamination and cracking: Repeated flexing can cause delamination or cracking of the flex PCB substrate. Stiffeners reduce the flexing in critical areas, minimizing the risk of such damage.
• Reduce assembly stress: During the assembly process, PCBs can experience stress from machinery and handling. Stiffeners distribute this stress evenly across the board, reducing the possibility of damage during assembly.
• Maintain planarity for critical operations: Certain operations, such as soldering, require the PCB to remain flat. Stiffeners maintain planarity in these critical areas so that the flex PCB can undergo these processes without issues.  

How to Use a PCB Stiffener?

This guide provides a step-by-step approach on how to effectively use PCB stiffeners in your PCB design and assembly process.

1. Find the type of stiffener required: In the first step, you need to recognize what type of stiffeners suits your PCB design. In this you can consider the following factors:

• Board size and thickness
• Component placement
• Flexibility requirements
• Environmental condition

2. Pick the suitable material: Picking up the appropriate material for your PCB stiffeners is crucial. Common PCB materials include stainless steel/ aluminum, FR4, and polyimide.

• FR4:  This is the same substrate material used to build PCBs and feature reinforced fiberglass, epoxy resin, and copper. FR4 material provides solid support during the reflow, and pick and place assembly process.
• Polyamide: These stiffeners are made from high-temperature polymers, such as Kapton. Polyamide stiffeners create solder resistance, bond strength, and additional wear resistance over hole locations, limiting damage over the time.
• Aluminum/Stainless Steel: These materials are quite expensive than the other two materials, and provide several benefits. They are tougher, corrosion resistant, and offer great formability for components.

3. Design and integration: Now it’s time to incorporate the stiffeners into your PCB design using your PCB layout software. Follow these steps:

• Identify and mark the areas on the PCB where stiffeners are needed.
• Specify the dimensions of the stiffeners, ensuring they cover the necessary areas without interfering with other components or traces.
• Ensure that the stiffener details are included in the design files sent to the manufacturer.

4. Manufacturing process: Once the design is finalized, proceed with the manufacturing process. In this step, first you need to prepare the material. The stiffener material is cut to size. For metal stiffeners, machining or stamping is used. Laser cutting or precision knives are used for polyimide stiffeners. Then, attach the stiffeners to the PCB.  Stiffeners can be attached to the PCB using adhesive bonding, thermal bonding for polyimide stiffeners, or mechanical fastening for metal stiffeners.
5. Inspection and testing: After attaching the stiffeners, now inspect the PCB to ensure proper alignment and adhesion. Do the proper mechanical testing to verify that the stiffeners provide the desired level of support.

Incorporating stiffeners is a crucial step for durability and reliability of the flexible printed circuit boards. By understanding, what is stiffeners and its importance in PCB design, designers can make informed decisions to enhance the performance and longevity of their products. If you want to need a practical guidance on using PCB stiffeners in your flexible PCBs, you can contact the team of Twisted Traces. With 30 years of experience, the experts at the company will help you understand the benefits of stiffeners, and help you choose the right one for your PCB.