FPC PCB Manufacturing: How to Choose the Right FPC Parameters for Optimal Performance
5 min
- What Are FPC Parameters?
- Key Factors to Consider When Choosing FPC Parameters
- Common Processes
What Are FPC Parameters?
FPC flexible printed circuit boards parameters refer to the specific design and material choices that define the performance and functionality of a flexible printed circuit. These parameters include material selection, thickness, layer count, bend radius, and more. Properly selecting these parameters ensures that the FPC meets the requirements of its intended application.
Key Factors to Consider When Choosing FPC Parameters
Board Quantity/Board Size
Board size refers to the dimensions of the board. The maximum size for JLC FPC boards is 234X490mm (limit 250X500mm), while the minimum size is not restricted. However, for sizes smaller than 20X20mm, panelization is recommended.
Number of Layers
The number of layers is generally determined during design, so you can directly select the required number of layers based on design specifications.
FPC boards can be classified into single-layer, double-sided, and multi-layer boards.
- Single-layer boards are the simplest flexible boards and are commonly used in industrial control and electronic instruments.
- Double-sided boards differ from single-layer FPCs by incorporating vias to connect two copper layers, forming electrical pathways. They are typically used in mobile phones, automotive dashboards, and similar products.
- Multi-layer boards consist of multiple single or double-sided FPCs laminated together. Through drilling and plating, they form metallized vias to create electrical pathways between layers. These are commonly used in high-end consumer electronics like smartphones.
Common Processes
Solder Mask Color
- FPC solder masks come in yellow, black, and white. Yellow is recommended.
- Yellow film is suitable for most products, such as various types of flexible ribbon cables.
- Black film is commonly used in high-end applications or products requiring light absorption, such as automotive, mobile phones, and LED displays.
- White film has an additional white coating and is often used in reflective products like lighting equipment, LED displays, and medical beauty devices.
Board Thickness
Board thickness refers to the thickness of the FPC flexible board itself, excluding reinforcement thickness.
If the measured area has no copper or coverlay, the final thickness may be reduced.
If a white coverlay is used, the thickness increases by 18um for single-sided boards and 36um for double-sided boards.
Copper Foil Thickness
This refers to the thickness of the copper foil in the FPC circuit layer, which should match the board thickness.
- Available options for single-sided boards: 18um (0.5oz), 35um (1oz)
- Available options for double-sided boards: 12um (0.33oz), 18um (0.5oz), 35um (1oz)
Minimum Line Width/Spacing
The smaller the width/spacing, the higher the difficulty. The general recommendation is 3/3mil or above.
JLC's limit is around 2/2mil, but it is recommended to avoid designing at this limit.
Minimum Via/Pad
The via outer diameter must be at least 0.2mm larger than the inner diameter, with a recommended margin of 0.25mm or more.
In general, the smaller the via, the more expensive it is. Recommended via inner diameter: 0.3mm, outer diameter: 0.55mm.
Solder Mask Covering
FPC uses a coverlay as the solder mask layer. There are two main types of solder mask coverage: via opening and via tenting.
- Via opening: The via pad is exposed in the final board. However, exposed vias in FPC may cause oxidation and copper fracture.
- Via tenting: The via pad is covered with solder mask to protect the copper from oxidation and to prevent copper fracture during bending. JLC defaults to via tenting. If via opening is required, it must be specifically noted when placing an order.
Minimum Solder Mask Bridge Width
The minimum solder mask bridge width is 0.5mm. That is, pad spacing must be ≥0.5mm to retain the bridge. If the spacing is smaller, JLC will default to exposing the vias.
There are five main types of reinforcement: PI, FR4, steel sheet, 3M double-sided adhesive, and electromagnetic shielding film.
- PI reinforcement is commonly used for gold finger insertion products.
- FR4 is used for reinforcing component hole areas.
- Steel sheet is more expensive but has excellent flatness and does not deform, making it suitable for products requiring chip mounting (since steel sheets have weak magnetism, they are not recommended for products like Hall sensors).
- 3M adhesive is generally used for fixing FPC boards during assembly.
- Electromagnetic shielding film is used to solve EMC issues. It is generally recommended to add grounding openings in the solder mask layer to connect the shielding film to the ground copper, enhancing shielding effectiveness. (Note: Prototype verification is required first, as the shielding film significantly impacts impedance. Improper design may lead to signal abnormalities.)
Total reinforcement thickness = FPC board thickness + reinforcement thickness, but it is not a direct sum. Solder mask thickness and whether the backside of gold fingers has copper must also be considered.
If you don't know how to calculate reinforcement thickness, click the link below to use the Reinforcement Thickness Calculator: https://jlcpcb.com/gold-fingers-PI-thickness
Panelization
The maximum panel size is 234X490mm.
Recommended spacing: 2mm; if steel sheet reinforcement is used, spacing should be 3mm.
Important! Many FPC board outlines are irregularly shaped. Improper panelization may reduce material utilization, increase costs, and complicate production. If you are unsure about panelization, JLC engineers can assist.
In addition to the above standard parameters, FPC production also involves gold fingers, impedance, half-cut holes, and other processes.
Choosing the right FPC parameters is essential for manufacturing high-quality, reliable, and cost-effective flexible printed circuits. By considering factors such as material selection, thickness, bend radius, and thermal performance, you can design FPCs that meet the demands of your application. Whether you're working on consumer electronics, automotive systems, or medical devices, understanding FPC parameters will help you achieve optimal results.
Keep Learning
Innovative Applications of Transparent Circuit Boards
Transparent PCB boards have a wide range of applications in modern electronic devices. Due to their unique appearance, transparent printed circuit boards are increasingly popular in consumer electronics. The application includes: smartphones, wearables, and high-end home appliances. Transparent printed circuit boards not only enhance product aesthetics but also make internal circuits visible. Which makes the inspection and maintenance process easy. Moreover, transparent printed circuit boards play a s......
Rigid PCB vs. Flexible PCB: Making the Right Choice
In today's world of modern technology, Printed Circuit Boards (PCBs) play a pivotal role as the backbone for connecting and facilitating the functionality of various electronic components. PCBs come in numerous varieties, but the most prevalent types are rigid PCBs and flexible PCBs. It's crucial to grasp the differences between these two categories when deciding on the most suitable PCB for a specific application. In this article, we will embark on a journey into the world of PCBs, delving into their......
The Role of Flex PCBs in Automotive Electronics
Flex PCBs, short for flexible printed circuit boards, have revolutionized various industries, including healthcare, automotive, and aviation. They have become an essential part of modern electronic devices. They have upset different enterprises, including clinical, car, and aviation. These PCBs, made from flexible materials like polyimide or polyester, can withstand high temperatures, making them suitable for harsh environments. Their flexibility allows them to fit into tight spaces, making them ideal......
Flex PCB Designing Useful Tips - JLCPCB
Flexible printed circuit boards, or Flex PCBs, are thin, lightweight printed circuit boards that can be bent, folded, and twisted to fit into any shape or size without damaging the electrical connections on the board. Flex PCBs are becoming increasingly popular in various industries, such as aerospace, automotive, medical devices, and consumer electronics. In this article, we will discuss what to consider while designing a Flexible PCB for effective product development. Currently, flex PCB manufacturi......
Considerations for Automotive Flex PCBs
Flex PCBs have gained significant popularity in the automotive industry due to their ability to conform to unique shapes and contours of automotive components. These PCBs are designed to withstand high temperatures, making them suitable for harsh environments. With the increasing demand for advanced technologies in automotive electronics, the use of flex PCBs is expected to continue to grow in the future. Design Considerations for Automotive Flex PCBs Due to their ease of conformation to the distincti......
Mastering PCB Stiffeners: A Comprehensive Guide to Types, Applications, and Design Best Practices for Flexible Circuits
Flexible and rigid-flex PCBs are increasingly common in modern electronic designs, but their soft nature poses mechanical reliability challenges, especially in connector, component mounting, and dynamic bending areas. PCB stiffeners serve as localized reinforcement materials to effectively address these issues. They add rigidity in designated areas to provide mechanical support while maintaining bendability in flexible zones. Engineers widely use them in consumer electronics, medical devices, automoti......