When I first started working with flexible PCBs (Printed Circuit Boards), one of my biggest questions was: “Can I use the same mounting methods I use for rigid boards?” If you’ve ever wondered the same, you’re not alone.
Flexible boards are becoming increasingly common in today’s electronics – from wearable gadgets to medical devices – but mounting them isn’t always straightforward. Let’s explore how rigid board mounting technology fits into the world of flexible circuits.
A flexible printed circuit board (FPC) that is thin, flexible, and bendable. Even though it is the same printed circuit board, the materials, and characteristics are different from those of a hard rigid circuit board. Can component mounting technology and connection technology for rigid boards be used for flexible boards?
Table of Contents
Understanding Rigid vs Flexible Boards
- Rigid Boards (FR4, etc.): These are the traditional PCBs used in most electronics. They’re stiff, strong, and easy to mount with screws, clamps, or brackets.
- Flexible Boards (Flex PCBs): Made of thin, bendable materials like polyimide. They’re lightweight, compact, and can bend or twist to fit into tight spaces.
I like to think of it this way: rigid boards are like wooden planks, while flexible boards are more like sheets of plastic. Both can be used in construction, but the way you mount them will differ.
Can Rigid Mounting Technology Work for Flexible Boards?
The short answer is: sometimes, but with limitations.
Rigid mounting technologies (like mechanical fasteners, brackets, or direct soldering to stiffeners) can be applied to flexible boards, but you have to account for the nature of flex circuits.
Here’s what I’ve learned:
- Works well if the flexible board is reinforced with a stiffener.
- For example, many flexible PCBs have stiffeners at connector ends so they can be mounted just like a rigid PCB.
- Not ideal for areas where the board needs to bend.
- Using rigid mounting on a part of the board that must flex will lead to cracks, stress, or long-term reliability issues.
Common Mounting Methods for Flexible Boards
When I worked on a wearable electronics project, here are the techniques I found most useful:
- Stiffeners (Polyimide, FR4, or Stainless Steel):
- Added to specific areas of a flexible PCB to provide rigidity where components or connectors need support.
- Adhesives & Tapes:
- Lightweight and flexible, perfect for keeping the PCB in place without restricting movement.
- Clamps or Brackets (Modified from Rigid Designs):
- Can be used if positioned only on non-bending areas.
- Overmolding / Potting:
- Encapsulates the flex circuit for durability in harsh environments.
Real-Life Applications
- Wearables: Smartwatches often use a combination of flexible boards and rigid mounting at connector points.
- Medical Devices: Flexible boards inside diagnostic tools are mounted with adhesives for vibration resistance.
- Automotive: Flex PCBs in dashboards use stiffeners so they can be mounted like rigid boards where needed.
When I opened my smartwatch out of curiosity, I saw that the charging connector was mounted on a stiffened flex section – that’s exactly how rigid mounting was adapted to a flexible design.
Conclusion
So, can rigid board mounting technology be used for flexible boards? Yes – but carefully.
If the flex PCB has reinforced stiff areas, rigid mounting works perfectly. But if the circuit is meant to bend, you’ll need more flexible solutions like adhesives or tapes.
In my experience, the best designs often use a hybrid approach: rigid mounting where support is needed, and flexible adhesives where mobility is critical.
FAQs
What is the difference between rigid and flexible PCB mounting?
Rigid PCB mounting is straightforward because the board doesn’t bend – you can screw it down, use brackets, or solder it in place. Flexible PCBs, on the other hand, bend and twist, so you need softer solutions like adhesives, tapes, or stiffeners to support them.
Can flexible boards handle the same stress as rigid ones?
Not really. Flexible boards are designed to bend, but they don’t like constant mechanical stress at the mounting points. That’s why most designs add stiffeners in critical areas – it gives them the strength of a rigid board where needed.
Why are stiffeners important in flex PCB mounting?
Think of stiffeners as giving your flexible PCB a “backbone.” They’re added only in specific spots (like connectors) so that you can mount or solder the board without damaging the flexible part.
Where are flexible PCBs most commonly used?
You’ll find them in wearables (like smartwatches), medical devices, automotive dashboards, and even foldable smartphones. Basically, anywhere space is tight and the board needs to bend or fit into unusual shapes.