Solenoid-Actuated Needle Valve for Precision Conformal Coating
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Solution Overview
Problem
Current conformal coating dispensers struggle with precision and accuracy, particularly with lower viscosity materials, leading to issues like splashing, clogging, and inability to coat small, densely populated areas effectively.
Innovation Solution
A needle valve coating system with a solenoid-operated air cylinder and pulse width modulator controls the needle valve to precisely manage the flow of conformal coating material, allowing for accurate application close to keep-out areas and minimizing waste, while preventing material from clinging to the dispensing tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a needle valve dispenser is used to control flow of lower viscosity conformal coating materials, then material flow control is improved, but the dispensing tip must be maintained extremely close to the substrate surface (within several millimeters) to reduce splashing, which limits applicability to densely populated PCBs
Solution Approach 1:
The patent employs a pneumatic system with an air cylinder and needle valve to control the dispensing of conformal coating material. Compressed air pressure is used to regulate material flow through the needle valve, enabling precise control of lower viscosity materials without requiring the dispensing tip to be extremely close to the substrate surface. This pneumatic control mechanism resolves the contradiction by providing both flow precision and operational ease for densely populated PCBs.
2Quantity of substance
If known needle valve dispensers are used, then material dispensing is controlled by time and pressure, but the inability to sharply cutoff flow results in dripping, drooling, poor flow control and less precise application
Solution Approach 1:
The patent implements periodic action through a solenoid valve that rapidly opens and closes to control material flow. The solenoid provides sharp cutoff capability by completely closing the flow path when de-energized, eliminating the dripping and drooling problems associated with traditional needle valves. This periodic on/off control enables precise application by delivering controlled bursts of material exactly when needed, significantly improving application precision while maintaining proper material quantity control.
3Manufacturing precision
If current dispensers dispense beads or atomized sprays, then coating can be applied, but there is a minimum coating area that is too large for current applications with smaller areas and higher component densities
Solution Approach 1:
The patent segments the coating material into discrete droplets through solenoid-controlled dispensing. Instead of continuous bead or spray patterns, the system delivers individual controlled droplets that can be precisely placed on small areas. This segmentation enables coating of minimal areas with high precision while adapting to high component densities, as each droplet can be independently positioned and sized according to the specific requirements of small-scale PCB features.
4Manufacturing precision
If needle valve dispensers are used, then material flow is controlled, but coating materials cling to and partially cure on the dispensing tip, leading to clogs and reduced repeatability and accuracy
Solution Approach 1:
The patent replaces the mechanical needle valve system with a solenoid valve actuated by electromagnetic force. This substitution eliminates the mechanical components that cause material to cling and cure on the dispensing tip. The solenoid provides clean, rapid opening and closing actions without mechanical wear or material buildup, preventing clogs and maintaining consistent flow control over time. This improves both repeatability and accuracy while preserving the flow control capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves improved accuracy and precision in applying conformal coatings to smaller areas with reduced handling and maintenance, enabling precise control over material volume and minimizing waste, especially suitable for densely populated PCBs.
Implementation Method 1
a solenoid operable to actuate the needle valve
Implementation Method 2
The needle valve is movable to an open position by an air cylinder piston in response to pressurized air received from the solenoid
Data Source
AI summary
A coating system with an applicator that has an air cylinder with a needle valve. A control has a timer that provides a string of electrical pulses to a solenoid. With each pulse, the solenoid applies pressurized air to a cylinder piston, thereby opening the needle valve and permitting coating material to flow past the needle valve. The needle valve is closed for durations of time between pulses, and the coating material is ejected from a dispensing needle in response to closings of the needle valve.