Flexible PCBs
Flexible PCB, also known as flexible circuit board or FPC, it is made with flexible plastic substrates, such as polyimide, PEEK or transparent conductive polyester film by photo-lithographic technology.
Flexible printed circuit boards were initially designed as an alternative solution for traditional wire harness. They have been often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring.
Due to its flexibility to be bent to any shape, it has grown much popularity as technology advances. FPCs are usually found in portable electronics (e.g. cameras, smartphones, wearable devices, laptops, and hard drives etc.), industrial devices, medical devices, IoT, connectivity and mobility fields where many interconnections are required a more compact and lightweight package.
As a connective component, the typical benefits of flex PCB compared to conventional wiring and rigid PCB include:
Design Freedom: Flexible PCBs are as flexible as wires or ribbon cables, so the design options are not so limited as that for rigid PCBs. PFC allows more spaces and opportunities for designers to turn their ideas into reality.
Reduced Space and Weight: The characteristics of base materials enable FPC to have a huge reduction in package volume and weight.
Durability: A properly designed flexible circuit board fabricated with qualified materials and craftsmanship can be more durable than common rigid PCB under external circumstances with strong force and vibration.
Higher Circuit Density: Flexible circuits allow for narrower tracks and spacing can be laid out which gives way to high density design.
Increased Heat Dissipation: Due to the larger surface-to-volume ratio of the copper traces and the ultra-thin electrical dielectric layer, heat generated inside can be dissipated more easily from both sides of the flex circuits.
Minimized Errors: Flexible circuit boards have replaced many types of connectors and harness assembly in several applications, so the use of FPC can reduce the incidence of human errors during manual wiring.
Cost-effective: With the comprehensive advantages of FPC mentioned above, a well-designed FPC can reduce the overall cost of a project.
Although there are many benefits, the FPC technology also has some drawbacks, such as higher one-time initial cost and more difficult on repairing the circuits when it needs to be reworked. Furthermore, due to its flexible features, more assembly fixtures and handling care should be applied during assembly procedures.
For some applications, such as some smart wearable devices and medical devices, the choice of flexible PCB is necessary; for others, it depends on the overall analysis between benefits and drawbacks.
Types of Flexible PCBs
IPC6013 Type 1 – Single-Sided
IPC6013 Type 2 – Double-Sided
IPC6013 Type 3 – Multi-Layer
Rigid-Flex PCBs
Rigid-flex PCB is a hybrid combination of rigid and flexible substrates laminated into a single structure. It makes full use of the benefits each board type provides.
The rigid areas are where no bending requirements needed. The outer rigid layers are connected with inner flexible layers through copper plated vias. Rigid-flex circuits usually provide higher components density and more spaces for design options.
Rigid-flex may also involve in advanced technologies like HDI, unlike the cost-effective FPC or rigid PCBs, rigid-flex PCBs usually have higher cost due to their more complicated design.
With the joint advantages of flex and rigid PCBs, rigid-flex PCBs can be used to reduce costs and assembly time for applications which require lots of manual wiring work. Like the pure FPC, more and more rigid-flexible PCBs have been applied to medical devices, automotive electronics, aviation and space applications.
Types of Rigid-Flex PCBs
Type 1 – Standard Rigid-Flex Construction
Type 2 – Asymmetrical Rigid-Flex Construction
Type 3 – Multi-layer/HDI Rigid-Flex Construction
X-Parts FPC Manufacturing Capabilities
| Features | Prototypes | Mass Production |
| Layer Count | 1-6L | 1-6L |
| Materials | PI 12.5-100 μm ; Copper 12/18/35 μm | PI 12.5/25/38/50 μm ; Copper 12/18 μm |
| Minimum Track Width | 0.04 MM | 0.045 MM |
| Minimum Track Space | 0.035 MM | 0.04 MM |
| Minimum Hole Size | 0.05 MM (Laser) | ≧ 0.1 MM |
| Minimum Solder Pad Diameter | ≧ 0.25 MM | ≧ 0.3 MM |
| Minimum Board Thickness | 0.05 MM | 0.05 MM |
| Precision of Connector Pins | ± 0.05 MM | ± 0.05 MM |
| Drilling Hole Tolerance | ± 0.025 MM | ± 0.05 MM |
| Track Etching Tolerance | W ± 10% | W ± 10% |
| Stiffener | PI / FR4 / 304 / 316 / Aluminum Sheet | PI / FR4 / 304 / 316 |
| Surface Finish | ENIG | ENIG |
X-Parts Rigid-Flex PCBs Manufacturing Capabilities
| Features | Capabilities | |
| Layer Count | 4-16L | |
| Technology Highlights | Mixed materials including RF and high speed, standard FR-4, polyimide flex. Adhesiveless or adhesive based polyimide flex constructions, with cover coat or flexible solder mask materials. | |
| Materials | RA Copper, HTE Copper, FR-4, Polyimide, Adhesive | |
| Copper Thickness | 18 μm – 105 μm | |
| Minimum Track / Spacing | 0.075 MM / 0.075 MM | |
| PCB Thickness | 0.4 MM – 3 MM | |
| PCB Thickness (Flex Section) | 0.05 – 0.8 MM | |
| Maximum Dimensions | 610 MM x 450 MM | |
| Surface Finish | ENIG, Immersion Tin, Immersion Silver | |
| Minimum Mechanical Drill | 0.15 MM | |
| Minimum Laser Drill | 0.10 MM Standard, 0.075 MM Advanced | |
In X-Parts, beyond of manufacturing service, our professional engineers will be happy to provide engineering services (Design for Manufacturability and Assembly Analysis, Design Rule Check, Controlled Impedance Modeling and Panelization etc.) to help your design and products to meet their best quality and performances.
