Printed circuit boards (PCBs)
are becoming ever more complex and assemblies are being packed with an ever-greater
component density and surface mount technology (SMT) components that get
exposed to harsh and rugged environments. Common coating methods aren’t
equipped with the precision or speed to handle applying conformal coating to these kind of assemblies; coating machine
equipment manufacturers are constantly establishing much better process control
tools, software application, equipment and coating compounds in response to this
need. Client needs and emerging innovation have led to the adaptation of archaic
conformal coating equipment to automated fluid dispensing systems that
can better address this need. Adaptations of dispensing valve applicators,
fitting of a high-speed fluid dispenser
to coating machines and developments in conformal coating compounds
are just a few of the technology that has
actually enabled the manufacture of advanced electronics.
Tilt Action
Fluid dispensing equipment that has the capability of flow coating and outlining the No-Zone or sensitive areas are helped by pneumatic tilt action throughout the process of coating machines. In the past, conformal coating machine could not coat the bottom or sides of components on PCBs, but that restriction was lifted off with the advent of four-axis tilting capabilities. They are now equipped with a tilt accessory on the arms to coat all four sides of the component and areas that formerly could not be reached with the traditional vertical approach.
The
vertical angle of the dispenser can now be tilted to about 35° maximum in majority
of the machines and hit the right, left, back, or front of difficult-to-reach
locations and components. Four Position Tilt capabilities enable the machine to
coat all the sides of a component with accuracy.
Four-Axis (X,Y,Z U) + Tilt Action
Some coating machines have a four-axis +
tilt application that permits further functionality for the fluid dispenser and has tilt and rotation
(±180°) activities for dispensing conformal coating on vertical services and
underneath the components. The dispensing action can gain access to tight and
hard to reach areas that are impossible to coat with a basic downwards spray
pattern.
Coating Specifications and More Functionality
Conformal coating for PCB advancements has allowed for numerous desirable specifications. The spray coating patterns of automated fluid dispensing systems usually vary from about 0.125” (3.175 millimeters) to about 2” (50.8 millimeters) and the variation is attributable to the height of the dispenser from the substrate. You can easily achieve thicknesses of 0.002" (0.051 millimeters) and beyond with a single pass of the dispenser. The thickness of the coating is managed by the machine speed and the flow regulator situated on the spray valves.
This
repeatability and accuracy aspect provides the advantage of eliminating much if
not all of the manual masking of the PCB. However, success or failure doesn’t
simply depend on the application method but on the capabilities of the machine.
There are now conformal
coating machines that
have the capability to access almost all required coating areas on the PCB while
avoiding keep-out areas. Often, when spray valves alone can’t gain access to an
area or coverage is too much in an area, a separate needle is used in the
dispensing valve that also has optional tilt capabilities. This setup can then be
incorporated into the coating machine’s fluid
dispensing system for added functionality.
This article is brought
to you by Anda Automation – the
conformal coating and fluid dispenser specialist.
