FPC Assembly

Flexible PCB Assembly

FPC assembly, is the process of integrating electronic components onto FPC. FPC assembly involves mounting surface mount components, such as resistors, capacitors, integrated circuits, and connectors, onto the flexible substrate using various techniques such as soldering, conductive adhesive bonding, or laser ablation.

As an experienced FPC assembly manufacturer, Sienta offers FPCA that meets your requirements!

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FPC Assembly

Capabilities Of FPC Assembly

Limit Tolerance Normal tolerance
Layer / 1-6 layer 1-6 layer
Cutting size mm 250*1000mm 250*500mm
Min. thickness mm 0.075mm 0.10mm
Adhesive stiffener um PSA:50um PSA:50um
Hot setting adhesive um 12.5/25/40um 12.5/25/40um
Min. drilling hole size mm 0.1 0.2
Hole diameter tolerance mm ±0.075 ±0.1
Hole wall copper thickness um 8/15/25 8/15/25
Min line width/space mm 0.05/0.05 0.075/0.075
Line width tolerance mm ±0.03 ±0.04
Distance between hole edge to outline mm ≥0.4 ≥0.5
Solder mask thickness um 8 15
Silk screen thickness um 8 15
Immersion gold um Ni: 2.0~5.0 Ni: 2.0~5.0
Au: 0.03~0.08 Au: 0.03~0.08
Key Points of FPC SMT Process

Abstract: With the trend towards miniaturization in consumer electronic products, the application of Flexible Printed Circuits (FPC) is becoming increasingly widespread.

The SMT (Surface Mount Technology) process for FPC differs from traditional PCBs, and this article provides a detailed description of the key process steps in FPC SMT production, including pre-treatment, fixation, printing, component placement, reflow soldering, testing, inspection, and separation.

This information will be helpful for readers who are new to FPC SMT production.

Keywords: FPC, SMT, FPCA,Flexible PCB SMD,FPCA,FPC assembly.

A PCB (Printed Circuit Board) is a rigid board used in electronics.

FPC (Flexible Printed Circuit), also known as a flexible circuit board or flex board, is a flexible circuit board.

It is commonly referred to as a flexible board. Miniaturization of electronic products is an inevitable trend in development.

For many consumer products, surface mount components (SMD) are assembled on FPC due to space constraints, facilitating the overall assembly of the device.

FPC has found widespread application in digital products such as calculators, smartphones, digital cameras, and camcorders.

Conducting SMD surface mount assembly on FPC has become one of the trends in SMT (Surface Mount Technology) development.


The SMT (Surface Mount Technology) process requirements for FPC (Flexible Printed Circuit) differ significantly from traditional rigid PCB (Printed Circuit Board) SMT solutions. To achieve success in the FPC SMT process, proper positioning is of utmost importance. Due to the inherent flexibility and softness of FPC boards, it's essential to use dedicated carriers or fixtures. Without them, it's impossible to secure and transport the FPC boards, which are fundamental for processes like printing, component placement, and reflow soldering in SMT. The following are detailed descriptions of key process steps in FPC SMT production, including pre-treatment, fixation, printing, component placement, reflow soldering, testing, inspection, and separation:


Before SMT, FPCs may undergo surface cleaning and preparation to ensure proper adhesion and solderability of components.


To overcome the flexibility of FPCs, specialized carriers or fixtures are used to securely hold and transport the boards during the SMT process.


The solder paste is accurately applied to the FPC's pads using a stencil or screen-printing process, ensuring precise component placement.

Component Placement:

Surface mount components (SMD) are carefully placed onto the FPC, aligning them with the solder paste on the pads.

Reflow Soldering:

The FPC with components is passed through a reflow oven, where the solder paste is melted to form strong electrical connections between components and the FPC.


Functional and electrical testing may be performed to verify the integrity of the solder joints and the overall functionality of the assembled FPC.


Visual inspection and quality control measures are carried out to identify any defects or issues that may require correction.


After completing the SMT process, the FPCs may be separated from their carriers or panels, getting them ready for further assembly or integration into electronic devices.

In summary, the unique characteristics of FPCs, such as their flexibility, necessitate special handling and fixation during SMT. This is critical for ensuring precise soldering and the overall quality of the assembled components. Properly addressing these differences is essential for successful FPC SMT production.

Benefits Of FPC Assembly

  • Flexibility

    FPCs are designed to be highly flexible, allowing them to bend, twist, and fold to fit into tight spaces or unconventional shapes. FPC assembly is especially valuable in miniaturized electronic devices or systems with limited space.

  • Weight Reduction

    This advantage is particularly beneficial in applications where weight reduction is a priority, such as portable devices, wearables, or aerospace applications. By using FPC assembly, you can achieve significant weight savings in your electronic designs.

  • Space Saving

    FPCs are thin and lightweight, making them ideal for applications with limited space or where weight reduction is crucial. The compact nature of FPCs allows for efficient utilization of available space, enabling smaller and slimmer electronic devices.

  • Enhanced Signal Integrity

    The thin and flexible nature of FPCs helps to minimize signal losses, crosstalk, and electromagnetic interference. This enables better signal integrity and higher data transmission rates, making FPC assembly well-suited for high-speed digital applications or sensitive analog circuits.

  • Design Freedom

    FPCs can be tailored to fit into irregularly shaped enclosures, wrap around corners, or conform to complex geometries, providing designers with more freedom and creativity in their electronic designs.

  • Cost Efficiency

    Although the initial production costs of FPC may be higher than traditional rigid PCBs, FPC can help reduce costs during assembly, testing, and maintenance by eliminating connectors, reducing assembly time, and simplifying integration.


  • Q What is your MOQ(Minimum Order Quantity)?

    We have no MOQ limited.Sample and mass production all can support.

  • Q What is needed for quotation?

    FPC&rigid-flex PCB&PCB:Quantity, Gerber file and Technical requirements(material,surface finish treatment, copper thickness,board thickness ,...)
    PCBA:PCB information, BOM list

  • Q Can you manufacture my PCB from a picture?

    No, we cannot accept BMP, GIF, TIFF, or JPG pictures as the manufacturing file.If you do not have gerber file, you can send us sample to copy it.

  • Q Are my files safe?

    We ensure complete safety and security of your files and protect our customers' intellectual property throughout the entire process. Any documents provided by our customers are kept strictly confidential and are never shared with any third parties.

  • Q How long will it take to receive my quotation?

    We will respond your quotation within 24 hours to the quotation requests.

  • Q How can I pay?

    We accept payments by PayPal, cash, bank transfer (T/T),WU,Alipay. If need other payment method please contact us (sienta@sienta.com.cn).

  • Q What's your transport method?

    We use UPS, FedEx, or DHL to ship the boards. If you have your own freight forwarding company, we can also work with them.

  • Q Do you offer free sample?

    We can offer samples, but you must pay for them first. If you go ahead with mass production later on, the cost of the samples will be deducted.We look forward to establishing a long-term business relationship with you!

  • Q What is your standard lead time?

    As FPC&PCB belong to customized products,generally it is 3-7 days for samples and 10-20 days for mass products.The actual delivery date according to difficulty of the products, the quantity and etc.Please contact us to get different product lead time.

  • Q How do you control the product quality?

    We adhere to strict quality control standards set by ISO 9001, ISO 14001, IATF 16949, and SGS. All boards undergo 100% testing and we offer a range of inspection options including visual, X-ray, AOI, and ICT/FCT.

  • Q How many layer can you produce for flexible PCB?

    For FPC, we can produce from 1 layer to 8 layers.

  • Q How many layer can you produce for Rigid flexible PCB?

    For Rigid flexible PCB board, we can produce from 2 layer to 8 layers.

  • Q Which surface treatment can you produce for FPC, PCB and rigid flexi PCB?

    We can produce Immersion gold, immersion silver, OSP, hot air Levelling(L/F), Gold plating,ENIPIG, Immersion tin and etc.

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