Industrial machine vision systems handle tasks such as visual inspection, positioning guidance, and dimensional measurement on production lines; core equipment includes industrial cameras, image acquisition cards, and vision controllers. The circuit boards used within these devices are primarily high-density multilayer boards and HDI (High-Density Interconnect) boards, with high-speed signal areas requiring impedance control and low-loss materials. Selecting the right circuit board requires understanding the specific board requirements for each machine vision module.
I. Circuit board requirements for industrial cameras
Industrial cameras serve as the "eyes" of machine vision systems. With compact internal spaces and high integration of image sensors and processing circuitry, they impose two main requirements on circuit boards:
First, high density. Due to their small size and multifunctionality, cameras require extensive routing within a limited area. HDI boards, which utilize blind and buried via structures to achieve high-density interconnection, are a common choice for camera mainboards. Smaller micro-via apertures and higher via-stacking orders allow for greater routing density and design flexibility.
Second, high-speed signal transmission. Handling massive amounts of image data requires high transmission rates between the sensor and processor, making the system sensitive to impedance consistency. Internal board traces require strict characteristic impedance control to prevent signal reflection and attenuation from compromising image quality.
II. Board characteristics for image acquisition cards and vision controllers
Image acquisition cards are responsible for high-speed data transfer from the camera to the industrial control system. Characterized by high interface speeds and dense routing, they typically employ multilayer boards with strict impedance control to ensure high-speed signal integrity. The number of layers is determined by the number of interfaces and routing complexity; more data channels require more reference and routing layers.
Vision controllers are essentially high-performance industrial computers. Their mainboards feature high layer counts to accommodate CPUs, memory, and various expansion interfaces; the selection logic is similar to that of server mainboards, though with stricter constraints on size and power consumption. Light source controllers, conversely, function as power control boards handling high currents, making copper thickness and thermal management the primary design priorities.
III. Selection strategy: Determine signal rates first, then the board-level solution
A three-step approach is recommended when selecting circuit boards for machine vision:
First, assess the signal rate and density requirements for each module. Cameras and acquisition cards operate in high-speed, high-density environments, making HDI and high-layer-count solutions the preferred choices. Controller mainboards should have their layer counts determined by the processor platform requirements, while light source boards should have copper thickness selected based on current requirements. Next, verify the manufacturer's manufacturing capabilities against your design requirements. Check specifications such as the maximum HDI layer count, minimum trace width and spacing, minimum via diameter, and the aspect ratio (via diameter to board thickness). For high-speed boards, also confirm the manufacturer's impedance control and testing capabilities. Checking the process capability chart item by item is more reliable than relying on verbal assurances.
Subsequently, focus on batch consistency. For machine vision equipment, boards of the same model must maintain consistent performance across production batches. The stability of impedance distribution and dimensional control (scaling) determines the yield and consistency of the production run.
IV. Relevant Processes and Considerations
Common processes for high-speed, high-density boards include blind and buried vias, resin-plugged vias, and ENIG (Electroless Nickel/Immersion Gold) surface finish. Blind and buried vias facilitate high-density interconnects; resin-plugged vias create a flat surface conducive to subsequent routing; and ENIG provides excellent solderability and storage stability. When selecting a surface finish, consider factors such as the storage period and the number of soldering cycles.
Machine vision boards operate in industrial environments where temperature fluctuations, vibration, and dust are common. When placing an order, inform the manufacturer of the operating environment and reliability requirements to ensure the appropriate board material grade and process parameters are selected. Additionally, request impedance test reports and full inspection records to verify that every board has been validated before leaving the factory.
The type of circuit board used for industrial machine vision depends on its location within the equipment: high-density HDI boards with impedance control are chosen for cameras and image acquisition cards; multi-layer boards are selected for controllers based on the computing platform; and thick-copper boards are prioritized for light sources to aid heat dissipation. By breaking down requirements by module, selecting manufacturers based on process capabilities, and conducting acceptance checks based on data, you can ensure the high speed and stability of the machine vision system.