SMT Line – A Complete Guide on Surface Mount Technology Line

SMT Line – A Complete Guide on Surface Mount Technology Line

Surface mount technology (SMT) has revolutionized the electronics manufacturing industry over the past few decades.

The SMT assembly line, commonly known as the SMT line, allows for automated mass production of printed circuit board (PCB) assemblies with great precision and speed.

This article provides a comprehensive overview of SMT lines, how they work, costs, and choosing the right SMT line manufacturer.

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    What is SMT Line?

    An SMT line refers to the fully automated production line utilized to assemble surface mount devices (SMDs) onto printed circuit boards. SMT lines consist of a sequence of machines and components optimized for high-volume manufacturing of electronics.

    SMT Line
    SMT Line

    The SMT line sequentially transports PCBs to various modules that use advanced robotic technology to populate boards with surface mount components through solder jetting, adhesive dispensing, inspection, testing, cleaning, and other automated processes.

    SMT lines offer extreme accuracy at ultra-high speeds compared to manual PCB assembly, allowing manufacturers to mass produce electronic products cost-effectively. They enable automated assembly of consumer electronics, appliances, vehicles, aerospace avionics, medical devices, industrial equipment and more.

    How SMT line works

    Why Do We Use SMT Line?

    There are several key reasons SMT lines have become the gold standard for electronic and PCB assembly in most manufacturing facilities:

    Increased Production Speed
    SMT lines can operate at speeds of over 15,000 components per hour, completing assembly much faster than humanly possible. This results in higher throughput and productivity.

    Improved Consistency and Precision
    Automated SMT machinery ensures extremely consistent, repeatable, and precise component placement and soldering down to 0.05mm accuracy, superior to manual methods.

    Versatile Configuration
    SMT lines are highly modular and can be configured to handle components of varying sizes from 01005 chips to large QFPs and connectors. Feeders, trolleys, sorters, magazines, detectors, dispensing heads, and nozzles can all be adapted across product lines.

    Reduced Labor Costs
    Automation significantly reduces labor requirements and associated costs compared to hand soldering. SMT allows high volumes without expanding labor proportionally.

    Abilities to Handle Complex PCBs
    SMT lines can accommodate complex multilayer PCBs, fine-pitch components, and miniaturized circuits, enabling advanced electronics manufacturing.

    Improved Quality and Reliability
    Automated process controls, machine vision inspection, and testing lead to reduced defects and improved end-product quality and reliability.

    Scalable for Demand
    SMT lines offer flexible capacity that can scale up or down by adding or reducing equipment to match production needs, ideal for fluctuating demand.

    What is the SMT Line Process?

    SMT Line Process
    SMT Line Process

    While SMT line configurations can vary, the core assembly process generally follows these key steps:

    1. Solder Paste Printing: The PCBs first pass through a solder paste printer that deposits a controlled pattern of solder paste onto the contact pads where components will be placed.

    2. SMD Component Placement: Next, pick-and-place machines precisely populate the PCBs by rapidly picking components from feeders and placing them on their designated solder-paste-coated pads in the programmed sequence.

    3. Solder Reflow: The populated boards then pass through an industrial soldering oven that melts or reflows the solder paste to form permanent electrical solder joints that affix the SMDs to the PCB.

    4. Conformal Coating: An optional coating machine may then deposit a protective plastic coating layer onto the assembled PCBs providing insulation and preventing damage.

    5. Automated Optical Inspection (AOI): Computerized optical inspection examines the assembled PCBs for defects in soldering, placement or components using cameras.

    6. Functional Testing: Electrical tests are conducted to confirm proper functioning by checking continuity, resistance, voltage, and other parameters.

    7. Labelling, Packaging and Shipping: Finally, finished assemblies are marked with serial numbers, packaged and shipped out. Conveyors, robots and computer tracking manage material flows.

    This fully automated in-line sequence allows consistent, end-to-end assembly of electronics with minimal human intervention for mass production efficiencies.

    What is an SMT Line Machine?

    There are several key equipment modules that comprise a cohesive SMT line:

    Solder Paste Printer: Prints precise solder paste pattern onto PCBs before components are placed.

    Pick and Place Machine: High-speed automated robotic arm that picks components from feeders and places them accurately onto the boards.

    Solder Reflow Oven: Soldering system that melts solder to attach components to boards through convection, infrared radiation or vapor phase reflow.

    Conformal Coating System: Optional machine to deposit protective plastic film coating onto assembled boards.

    AOI (Automated Optical Inspection) Machine: Imaging-based system that scans boards and components for defects.

    Functional Tester: Tests electronic functions and parameters like continuity, resistance, voltage, etc.

    Conveyors: Roller conveyors that transport PCBs between machines.

    Feeders: Provide a constant supply of components to the pick-and-place system from reels, sticks or trays.

    Software: ERP, MES and machine control software manages production scheduling, setup, materials, process monitoring and tracking.

    These core machines integrated together in sequence comprise the automated SMT production line that touches every stage of assembly.

    How SMT Line Works?

    On an operational level, SMT lines work by first drawing Computer Aided Design files of the PCB circuits and then programming the assembly sequence into the machines through sophisticated software that translates CAD into machine instructions.

    How SMT Line Works
    How SMT Line Works

    Operators load the materials – blank PCB panels, solder paste, components, etc. The conveyor transfers panels into the solder paste printer to deposit paste on pads per the program. PCBs are then conveyed to the pick-and place-machine which uses pneumatic vacuum suction heads to rapidly pick components from feeders and precisely place them on the boards as instructed.

    The components are now tacked loosely on the pads. The conveyor advances panels into the reflow oven to melt solder and solidly attach parts to the boards. Coating and inspection stations perform their automated tasks next before boards exit the line fully assembled.

    Changeovers between product variants are completed by swapping in appropriate feeders and programs. The modular machines work in tightly coordinated harmony to receive boards, add value at each step, then output completed boards through software-orchestrated automation that runs 24/7 with high reliability.

    How Much Does an SMT Line Cost?

    The cost of an SMT line can range quite significantly from around $500,000 for a basic 6-8 station line up to $5 million or more for a fully loaded, high-end line with the latest technologies. The factors impacting overall capital cost include:

    • Number of machines/modules needed based on production volumes and complexity.
    • Type of mounting technology – chip shooter vs multi-gantry, dual delivery, etc.
    • Speed and precision capabilities.
    • Additional inline processes like coating, inspection, testing.
    • Degree of automation and software sophistication.
    • Conveyor length and features.
    • Brand reputation and quality of equipment.
    • Service contracts, training, installation, etc.

    While representing a substantial upfront investment, the long-term efficiencies and revenue-generating capabilities of a high-performing SMT line usually far outweigh the initial costs for electronics manufacturers focused on growth, consistency, and technology leadership.

    How to Choose an SMT Line Manufacturer?

    SMT Line Manufacturer
    SMT Line Manufacturer

    With many machine builders to choose from, here are some tips for selecting the right SMT line supplier:

    • Research industry reputation, credentials, client reviews and case studies. More established players tend to be more reliable.
    • Look for specialized expertise in your products and volumes rather than generalists.
    • Consider technical sophistication – does their line incorporate the latest innovations?
    • Evaluate speed, precision, changeover times, and other capabilities.
    • Assess flexibility – can the line be readily expanded and adapted in the future?  
    • Examine the proposed factory layout and material flows for bottlenecks.
    • Review after-sales support services, maintenance plans, training services, documentation, and warranties.
    • Compare total cost of ownership against expected ROI rather than just focusing on upfront price.
    • Seek suppliers ready to collaborate as long-term partners, not just vendors.

    By carefully assessing your manufacturing objectives, and then evaluating providers on their track record, specialized abilities, technological sophistication, and after-sale support, you can identify the ideal SMT line partner to fulfill your product roadmap.


    Implementing an advanced SMT line is a strategic investment that enables electronics manufacturers to achieve automated economies of scale and remain competitive. As this article outlined, SMT lines offer extreme speed, precision, flexibility and reliability in mass-producing PCB assemblies compared to conventional manual approaches. With diligent planning and selection of the right equipment and integrators, manufacturers can leverage SMT lines to reduce costs while expanding capabilities and output. The result is the capacity to profitably deliver high-quality, leading-edge electronic products at market-beating value.

    FAQ-about PCB

    An SMT line refers to the fully automated production line utilized to assemble surface mount devices (SMDs) onto printed circuit boards. SMT lines consist of a sequence of machines and components optimized for high-volume manufacturing of electronics.

    • Increased Production Speed
    • Improved Consistency and Precision
    • Versatile Configuration
    • Reduced Labor Costs
    • Abilities to Handle Complex PCBs
    • Improved Quality and Reliability
    • Scalable for Demand

    1. Solder Paste Printing

    2. SMD Component Placement

    3. Solder Reflow

    4. Conformal Coating

    5. Automated Optical Inspection (AOI)

    6. Functional Testing

    7. Labelling, Packaging and Shipping


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