In the electronics manufacturing industry, the environmental reliability of PCB boards directly determines the service life and safety level of end products. As consumer electronics, automotive electronics, new energy and other industries continue to raise their protection requirements, conformal coating (three-proof paint) has become a core protection process in PCB manufacturing. A key pain point for many electronics manufacturers is how to ensure coating uniformity and regional accuracy while meeting mass production capacity requirements.
Inline automated coating equipment, with its continuous operation, high-precision valve control and vision positioning compensation capabilities, is gradually replacing traditional manual coating and offline equipment to become the standard solution for mass production lines.
1. Process Essence and Core Requirements of PCB Conformal Coating
Conformal coating is a process that applies liquid polymer coating evenly on the PCB surface. After curing, it forms a flexible protective film with insulation, moisture resistance, salt spray resistance and mildew resistance, which can effectively protect the components and circuits on the circuit board from environmental erosion.
Four Core Process Requirements for Conformal Coating
● Uniform and controllable film thickness: The conventional coating thickness is controlled within the range of 20μm to 400μm. Too thin a film will lead to insufficient protection, while too thick a film is prone to stress cracking. It needs to be precisely adjusted according to the product protection level.
● Accurate coating area: Non-coating areas such as connectors, pads and sensitive components must be accurately avoided, and coating is only applied on the surface of specified components to avoid affecting electrical performance.
● Adaptation to mass production rhythm: It adapts to palletized continuous production, is compatible with PCB products of multiple sizes, and can be directly connected to the front and rear production lines to match the overall production rhythm.
● Strong glue compatibility: It needs to be compatible with coatings of different viscosities and different curing types.
Traditional manual coating and single-valve offline equipment generally have problems such as poor consistency, low efficiency and difficulty in covering fine areas. Inline coating equipment with multi-valve collaboration is the core solution to these pain points.
2. SEC-J450 Inline Coating Machine: An Integrated Solution for PCB Mass Production Coating
The SEC-J450 is an inline automated equipment launched by Second Intelligent for PCB conformal coating scenarios. It is compatible with standard pallet products, supports chain-type continuous conveying, and can complete the whole process with a single workstation. Its core design focuses on three dimensions: precision, efficiency and compatibility.
● Automated in-line operation: It adopts a left-in right-out chain conveyor line, with a maximum pallet load of 5kg and an adjustable line width of 80-400mm, compatible with products of various specifications. Driven by a stepper motor, the conveying speed is adjustable from 10 to 150mm/s, and can be directly connected to the front and rear production lines to realize unmanned circulation.
● High-precision motion platform: The XYZ three axes adopt Panasonic servo motors + TBI ball screws + HIWIN linear guide rails, with a repeat positioning accuracy of ±0.015mm and a maximum speed of 800mm/s for the XY axes. It supports continuous interpolation coating of points, lines, surfaces, arcs, circles and irregular curves, meeting the path planning requirements of complex PCBs.
● CCD vision positioning compensation: Equipped with a 1.3-megapixel CCD vision system, it supports automatic Mark point recognition and positioning, with a single-point recognition time of only 200ms. It can automatically correct the trajectory error caused by product offset; matched with a coaxial light source to achieve accurate recognition of reflective surfaces, it solves the problems of pallet positioning deviation and product placement errors.
● Complete supporting systems: It is standard equipped with a 10L pressure drum for glue supply, a 1L cleaning bucket and a dedicated glue discharge position. It supports SEMMA communication and MES system integration, meeting the production traceability and management needs of digital factories.
3. Core of Large-Area High-Efficiency Coating: Working Principle and Process Value of Spray Valves
In the conformal coating process, the open areas on the PCB surface require fast and uniform thin-film coating. The core execution unit for this scenario is the spray valve (atomizing coating valve), which is also the key component determining coating efficiency.
3.1 Working Principle of the Spray Valve
The H-808 high-precision spray valve configured in the SEC-J450 is a pneumatic atomizing coating valve. Its working principle is to accurately control the atomizing air pressure and glue inlet pressure to break low-to-medium viscosity liquid coatings into uniform mist particles, which cover the workpiece surface in a circular atomization form. Both the flow channel and valve stem of the valve are made of stainless steel, matched with NBR+PTFE seals, which can adapt to long-term stable operation of solvent-based and volatile coatings without corrosion.
3.2 Key Parameters and Process Adaptability
● Wide viscosity adaptability: The applicable glue viscosity ranges from 1 to 1500cps, compatible with various surface coating materials such as conformal coatings, UV glues and adhesives;
● Adjustable spray width: The spray width is adjustable from 3mm to 10mm, which can be flexibly adjusted according to the size of the coating area, taking into account both wide board coating and narrow edge area operation;
● Precise film thickness control: The coating thickness can be adjusted in the range of 20μm to 400μm. By adjusting the glue inlet pressure, equipment moving speed and atomizing air pressure, the film thickness requirements of different protection levels can be achieved;
● High-quality coating effect: The atomized particles are uniform and fine, and the sprayed product has no splash and neat edges, eliminating the need for additional manual trimming and effectively reducing post-processing procedures.
3.3 Core Value in Conformal Coating
The core advantage of the spray valve is to efficiently complete large-area uniform coating. For the open areas on the PCB surface, a single valve can complete the entire surface coating with continuous movement, which is several times more efficient than traditional needle dispensing. The SEC-J450 adopts a dual spray valve configuration, supporting simultaneous operation of two valves, which can further cover a wider width and adapt to large-size PCBs or multi-panel products, making it the core unit for improving coating efficiency in mass production lines.
4. Precise Glue Control for Fine Areas: Core Role of Needle Valves in Coating Process
In addition to large-area coating areas, there are a large number of fine positions such as component pins, gaps and corners on the PCB surface, as well as non-coating areas that need to be accurately avoided. This requires needle valves to achieve precise glue control, forming process complementarity with spray valves.
4.1 Working Principle of the Needle Valve
The F-Z201 compact impact needle valve equipped in the SEC-J450 adopts an impact-type glue shut-off structure: the pneumatic piston drives the valve stem to hit the valve seat at high speed to realize fast on-off of the fluid channel. The valve stem stroke can be flexibly adjusted, with fast glue shut-off response and clean cut-off, which can effectively control the dispensing volume and avoid common problems such as stringing, glue dripping and tailing.
4.2 Core Performance Features
● Ultra-wide viscosity adaptability: The applicable viscosity range covers 100 to 1,000,000cps, compatible from low-viscosity conformal coatings machine to high-viscosity silicones, and can withstand a maximum glue inlet pressure of 3.5Mpa;
● Micro-precise glue control: The impact-type glue shut-off structure delivers clean cut-off, suitable for small-volume dispensing and fine-line coating, and can accurately control the coating amount at component pins and gaps;
● Strong compatibility: The stainless steel flow channel is compatible with various glue types, and can be matched with different specifications of needles such as plastic seat needles, stainless steel needles and TT angled needles to meet coating requirements of different fineness.
4.3 Three Core Functions of Needle Valves in Coating Process
In conformal coating production lines, needle valves play the key role of “fine filling, precise edge trimming and fixed-point thickening”, and are the core components to ensure no dead corners and no over-coating.
● Edge trimming of non-coating areas: After the spray valve completes large-area coating, the needle valve can precisely trim the edges of non-coating areas such as connectors and pads, preventing the coating from covering sensitive areas and ensuring stable electrical performance;
● Gap filling at dead corners: For dead corners that are difficult to be evenly covered by spraying, such as gaps at the bottom of components and pin roots, the needle valve can realize fixed-point and quantitative filling to ensure no blind spots in protection;
● Thickened protection at special points: For some high-value components that require enhanced protection, fixed-point thickened coating can be applied through the needle valve to achieve differentiated film thickness control and improve the protection level of key areas.
5. Dual-Valve Collaboration + Multi-Head Fine-Tuning: Dual Guarantee of Efficiency and Precision for SEC-J450
The SEC-J450 adopts a four-valve configuration of “2 sets of spray valves + 2 sets of needle valves”, matched with a multi-head fine-tuning assembly, which can realize independent fine-tuning of a single head and simultaneous operation of dual valves, maximizing both coating efficiency and precision.
● Independent multi-head fine-tuning: Each valve set is equipped with an independent fine-tuning mechanism, and the valve head spacing can be flexibly adjusted in the range of 75mm to 300mm. The valve position can be flexibly adjusted according to the PCB layout to adapt to the coating paths of different products;
● Simultaneous dual-valve operation: Two sets of the same valve can perform coating actions simultaneously. For panel products or symmetrically laid out PCBs, two areas can be coated at the same time, greatly shortening the operation time of a single pallet;
● Flexible path planning: Combined with Second Intelligent’s customized software, drawing files in formats such as DXF can be imported to directly generate coating paths. Combined with CCD vision positioning compensation, even if the product is offset, the trajectory can be automatically corrected to ensure coating accuracy.
6. Supporting Selection Suggestions for Mass Production Implementation of Conformal Coating
A stable inline coating solution requires the support of supporting systems in addition to the core valve set and main engine to ensure long-term stable operation:
● Glue supply system selection: For conformal coatings, a 10L stainless steel pressure drum for glue supply can meet the glue replenishment cycle of mass production. Equipped with an electronic scale glue shortage alarm function, it can monitor the glue volume in real time to avoid coating defects caused by glue shortage;
● Cleaning and maintenance design: The equipment is standard equipped with a dedicated glue discharge position and a 1L cleaning bucket. The valve set and pipeline can be quickly cleaned before glue change or shutdown to avoid glue curing and blockage, extending the service life of the valve set;
● Digital integration capability: The equipment supports SEMMA communication port and MES system integration, which can upload coating parameters, production data and yield information to meet the production traceability and management needs of smart factories.
As electronics manufacturing upgrades toward high precision and high reliability, the automation and refinement of conformal coating processes have become an inevitable industry trend. The Second Intelligent SEC-J450 inline coating machine, through the dual-valve collaborative solution of “large-area high-efficiency coating by spray valves + fine filling by needle valves”, combined with a high-precision motion platform and vision positioning system, well balances coating accuracy, consistency and mass production efficiency, making it a highly adaptable solution for PCB three-proof coating mass production lines.
For manufacturers with coating requirements for different glue types and product specifications, the valve configuration, glue supply method and vision solution can be adjusted according to actual process needs to customize a coating solution more suitable for the production line.
