Global PCB Connections: Rigid-flex and Flexible PCBs—The Backbone of Modern Electronics
Flexible Thinking: The Key to a Successful Flex Circuit Design Transfer
Happy’s Tech Talk #29: Bend-to-Install Semi-flex FR-4
Assembly of Flexible Circuits
April 6, 2017 | John Talbot, Tramonto CircuitsEstimated reading time: 7 minutes
Every type of component can be soldered to flexible circuits with confidence. Through-hole components, SMT components, wires, switches, BGAs, etc. Some require more skill than others to be attached, but they all can be mounted reliably to flexible circuits. Some may be soldered automatically like through-hole or SMT components and others may have to be attached manually like wires or cables. The use of a microscope is necessary in assembly today.
Figure 4: Surface mount components and through-hole components.
The components get smaller each year and we are now in an era where a component that measures .020” by .010” is common. That’s not much bigger than a flake of black pepper. Most manual assembly and inspection, therefore, is done under a microscope or Automated Optical Inspection (AOI) device. With components that are too small to see with the naked eye, imagine the thought of identifying a non-compliant solder joint that is a fraction of the size of those small components. It’s not of significant importance though. A skilled assembler armed with soldering tools and a quality microscope will be able to attach any component to a flexible circuit.
Protection of Solder Joints After Assembly
The concerns do not end with the attachment of components. Products developed with flexible circuits are intended to be flexed. Although the material is flexible, the solder joints are not! If components or solder joints are in, or near a bend area, then it is wise to protect the solder joints. If not, the joint may fracture and cause intermittent issues that are difficult to identify.
A flexible epoxy or conformal coat may be added to the solder joints after the product has been tested and confirmed. This will keep the bends and flexing away from the solder joint and in the material where it is intended to be. This added safety feature will add robustness to flexible circuit assemblies and likely reduce the risk of failures in the field.
Figure 5: Epoxy covered solder joints.
Conclusion
Flexible circuits have many advantages. They’re lightweight, thin and flexible. This allows products to be lighter, smaller and thinner as well. Although the typical circuit assembly is not intended to be bent, formed or even dynamic, it can be done confidently with flexible circuits. The added time spent on the design of fixtures to assist in the assembly process is time well spent and will allow the circuit to flow through the assembly line smoothly and consistently. The result will be a robust flexible circuit assembly.
Page 2 of 2Share on:
Suggested Items
Driving Innovation: Direct Imaging vs. Conventional Exposure
07/01/2025 | Simon Khesin -- Column: Driving InnovationMy first camera used Kodak film. I even experimented with developing photos in the bathroom, though I usually dropped the film off at a Kodak center and received the prints two weeks later, only to discover that some images were out of focus or poorly framed. Today, every smartphone contains a high-quality camera capable of producing stunning images instantly.
Hands-On Demos Now Available for Apollo Seiko’s EF and AF Selective Soldering Lines
06/30/2025 | Apollo SeikoApollo Seiko, a leading innovator in soldering technology, is excited to spotlight its expanded lineup of EF and AF Series Selective Soldering Systems, now available for live demonstrations in its newly dedicated demo room.
Indium Corporation Expert to Present on Automotive and Industrial Solder Bonding Solutions at Global Electronics Association Workshop
06/26/2025 | IndiumIndium Corporation Principal Engineer, Advanced Materials, Andy Mackie, Ph.D., MSc, will deliver a technical presentation on innovative solder bonding solutions for automotive and industrial applications at the Global Electronics A
Fresh PCB Concepts: Assembly Challenges with Micro Components and Standard Solder Mask Practices
06/26/2025 | Team NCAB -- Column: Fresh PCB ConceptsMicro components have redefined what is possible in PCB design. With package sizes like 01005 and 0201 becoming more common in high-density layouts, designers are now expected to pack more performance into smaller spaces than ever before. While these advancements support miniaturization and functionality, they introduce new assembly challenges, particularly with traditional solder mask and legend application processes.
Knocking Down the Bone Pile: Tin Whisker Mitigation in Aerospace Applications, Part 3
06/25/2025 | Nash Bell -- Column: Knocking Down the Bone PileTin whiskers are slender, hair-like metallic growths that can develop on the surface of tin-plated electronic components. Typically measuring a few micrometers in diameter and growing several millimeters in length, they form through an electrochemical process influenced by environmental factors such as temperature variations, mechanical or compressive stress, and the aging of solder alloys.