Automated conveying technology is the fundamental core technology of PCB loader/unloaders, directly influencing the equipment’s conveying efficiency and stability. Currently, the mainstream conveying methods mainly include belt conveying and roller conveying.

This technology uses high-elasticity, wear-resistant polyurethane belts as the conveying medium. Servo motors drive the belt pulleys to achieve stable conveying of PCB boards. It offers advantages such as smooth conveying and low noise, effectively preventing scratches and damage to the PCB surface. Thus, it is suitable for conveying thin and flexible PCB boards. Meanwhile, by adjusting the belt tension and motor speed, belt conveying can achieve precise conveying of PCB boards of different sizes, with a typical conveying speed range of 0.5–3 m/min.

The conveying unit consists of multiple precision-machined metal rollers. Synchronous rotation of the rollers is achieved through timing belts or gear transmission, which in turn drives the movement of PCB boards. Roller conveying features high load-bearing capacity and low maintenance costs, making it suitable for conveying thick/heavy PCB boards or those with metal brackets. To ensure conveying accuracy, the coaxiality error of the rollers must be controlled within 0.02 mm, and the spacing between adjacent rollers must be optimally designed based on the minimum size of the PCB board—usually, the spacing is no more than 1/3 of the shortest side of the PCB.

Precision positioning technology is crucial for ensuring accurate alignment between PCB boards and subsequent equipment (e.g., screen printers, pick-and-place machines) during the loading/unloading process, directly affecting the overall processing accuracy of the SMT production line. Current PCB loader/unloaders mainly adopt a hybrid positioning method that combines mechanical positioning and visual positioning.

Initial positioning is achieved through the cooperation of positioning pins, positioning blocks, and the edges or positioning holes of the PCB board. Positioning pins are made of high-hardness alloy materials, with their surfaces subjected to quenching treatment (hardness reaching HRC 60 or above) to ensure positioning accuracy after long-term use. The repeat positioning accuracy of mechanical positioning can typically reach ±0.05 mm, making it suitable for conventional PCB processing scenarios with low positioning accuracy requirements.

High-definition industrial cameras (with a resolution usually ranging from 2 to 5 megapixels) are used to capture images of positioning marks (e.g., fiducial points, pads) on the PCB surface. Image algorithms (such as template matching and edge detection) identify these positioning marks and calculate their coordinates, then drive servo motors to adjust the PCB position for precise positioning. The repeat positioning accuracy of visual positioning can reach ±0.01 mm, meeting the positioning requirements of high-precision PCB boards (e.g., mobile phone motherboards, automotive electronics PCBs). In addition, visual positioning has an automatic compensation function, which can real-time detect defects such as PCB warping and deformation and correct the position, further improving positioning accuracy.

Intelligent control technology is the core for enhancing the automation and intelligence levels of PCB loader/unloaders, mainly including PLC (Programmable Logic Controller) control, Human-Machine Interface (HMI), and coordinated control with the SMT production line.

A high-performance PLC serves as the control core to realize logical control of executive components such as the equipment’s conveying motors, positioning mechanisms, and lifting mechanisms. PLCs feature fast response speed and high reliability, enabling millisecond-level output of control commands to ensure precise coordination of all equipment actions. Meanwhile, by programming control logic, PLCs can realize automatic equipment operation, fault diagnosis, and alarm functions. When issues such as board jamming or motor failure occur, the PLC can immediately send an alarm signal and display the fault location, facilitating quick troubleshooting and maintenance by operators.

A touchscreen is equipped as the human-machine interaction interface. Operators can use the touchscreen to set equipment parameters (e.g., PCB size, conveying speed, positioning accuracy), monitor equipment operating status (e.g., operating speed, cumulative output, fault information), and perform manual operations (e.g., manual lifting, manual conveying). The HMI interface is designed to be concise and intuitive, supporting multi-language switching to meet the needs of operators in different regions. In addition, the HMI of some high-end PCB loader/unloaders has data storage and export functions, which can record equipment operating data (e.g., daily output, fault records) to facilitate production management and data analysis for enterprises.

Through industrial Ethernet (e.g., Profinet, EtherNet/IP), data interaction is conducted with the MES (Manufacturing Execution System) and equipment management system of the SMT production line to realize coordinated operation between the equipment and the production line. For example, after the subsequent pick-and-place machine completes the placement task of the current PCB board, the MES can send a command to the PCB loader/unloader to control the automatic conveying of the next PCB board. At the same time, the PCB loader/unloader can real-time feed back its operating status and fault information to the MES, enabling managers to conduct overall scheduling and optimization of the production line.

Manual assistance is required for some operations, such as manually stacking PCBs into the magazine and manually removing unloaded PCBs from the magazine. This type of equipment has a simple structure and low cost, making it suitable for small-batch, multi-variety PCB production scenarios (e.g., small electronic processing plants, R&D laboratories). The loading/unloading efficiency of semi-automatic PCB loader/unloaders is usually 10–20 boards per minute, which can meet the needs of small-scale production.

No manual intervention is required—it can realize automatic loading, conveying, positioning, unloading of PCBs, and automatic magazine replacement. Fully automatic PCB loader/unloaders are usually equipped with an automatic magazine storage unit, enabling continuous production of multi-batch PCBs. This type of equipment features high automation and high production efficiency, with a loading/unloading efficiency of up to 30–50 boards per minute. It is suitable for large-scale, high-volume PCB production scenarios, such as SMT production lines in large electronic manufacturing enterprises (e.g., mobile phone and computer manufacturers).

It adopts a vertical magazine storage structure, where PCBs are stacked vertically. Lifting mechanisms are used to realize vertical conveying of PCBs. Vertical equipment occupies a small area and has high space utilization, making it suitable for production scenarios with limited workshop space. However, due to the vertical placement of PCBs, higher requirements are placed on the positioning accuracy and stability of the equipment to prevent PCBs from tilting or falling during conveying.

It adopts a horizontal magazine storage structure, where PCBs are stacked horizontally. Conveying belts or rollers are used to realize horizontal conveying of PCBs. Horizontal equipment is easy to operate and maintain, and has stronger compatibility with PCB sizes (adapting to PCBs of different lengths and widths). However, horizontal equipment occupies a larger area, making it suitable for production scenarios with sufficient workshop space.

It is suitable for loading/unloading standard FR-4 material PCBs, with a typical PCB thickness of 0.8–2.0 mm and a size range of 50 mm × 50 mm to 500 mm × 500 mm. This type of equipment has mature technology and low cost, and is currently the most widely used type in SMT production lines.

It is specially designed for the characteristics of flexible PCBs (FPCs), adopting special conveying mechanisms (e.g., vacuum adsorption belts, flexible rollers) to prevent FPCs from wrinkling or deforming during conveying. Meanwhile, flexible PCB loader/unloaders are equipped with dedicated positioning fixtures to achieve precise positioning of FPCs, making them suitable for SMT production lines of products such as flexible mobile phone screens and wearable devices.

It is mainly used for loading/unloading high-precision PCBs (e.g., automotive electronics PCBs, aerospace PCBs). Such PCBs have extremely high positioning accuracy requirements (repeat positioning accuracy ≤ ±0.01 mm) and are usually equipped with complex components and dense pads. High-precision PCB loader/unloaders adopt high-precision visual positioning systems, servo drive systems, and high-rigidity mechanical structures to ensure positioning accuracy and stability of PCBs during the loading/unloading process.