SCH launch a NEW NON-SELECTIVE inline spray system for uniform conformal coating film application for medium and high volume coating processing
NON-SELECTIVE inline spray system for uniform conformal coating film application
Conformal coating atomised spray application using a spray gun is an excellent method for applying coatings to printed circuit boards.
However, the problem can be that depending on the coating used, the circuit board to be coated and the thickness tolerance demanded, it can be difficult to get repeatable results.
Dr Lee Hitchens, Technical Director of SCH Technologies discusses the issues
“We are regularly asked for conformal coating equipment that can apply an even, repeatable coating film on a PCB using a spray application. This can be done with a spray booth but the operator needs to be very well-trained and disciplined. Also, if a tight tolerance of coating thickness is required, this can be pretty difficult for even the best operators. ”
“Another option could be to use selective robotic spray technology. However, the nature of the valve technologies does not easily allow variation in coating thickness as an option. In fact, most of the time the coating thickness is bound by the material properties, the robot technology and environment in which the machine is placed. Couple this with the cost of a typical selective coating system and it quickly becomes unattractive!”
Dr Hitchens explains further
“What we really wanted was a simple system that combined the repeatability of the XYZ platform, had easy programming, could provide the spray gun film forming quality and could do all this at a sensible price. So, we started to search for a solution.”
This search quickly found there was no perfect answer until SCH began work with TE Connectivity. They were developing exactly what SCH were looking to find a customer project.
However, using an atomised spray nozzle with a programmable XYZ system allows repeatable atomised spray results with fixed distances, patterns and speeds. This non-selective approach applies an even film of conformal coating over circuit boards without significant operator expertise and gives control to the film thickness without operator interpretation found in manual spraying.
Contact SCH Technologies for further information on inline spray system by ringing +44 1226 249019 or email us at sales@schservices.com
Designing for Selective Robotic Conformal Coating Processing: Rule 13 “Sticking coatings to non stick silicones is a pain”
Applying silicone RTVs to circuit boards to provide support to components for long term reliability is fine. Just don’t do it before you apply a conformal coating to the surface unless the conformal coating itself is a silicone. Acrylic and urethane coatings do not stick to silicone. So, don’t try unless you want defects appearing.
Rule 13
If you call out silicone staking materials for ruggedisation purposes, use a silicone conformal coating. If you don’t want to use a silicone conformal coating, then use a urethane or epoxy staking compound.
The Rules
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.
Designing for Selective Robotic Conformal Coating Processing: Rule 12 “Coating 3D components is hard work. Why do it?”
When a circuit board surface looks like a scene from a cityscape and is highly 3D in nature, choosing to coat the sides of components is a really difficult process. You will need at least 5 axes of rotation, the process will slow down, quality really goes down and it looks awful cosmetically. If you don’t need it, don’t do it.
Rule 12
Make coating component packages optional. Coating the sides of a 3D device is difficult, especially since the coating is subject to gravity, as well as de-wetting due to mould release agents used in the component fabrication. The plastic or metal package mouldings are almost certainly more resistant to humidity or other forms of water than any conformal coating.
The Rules
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.
Designing for Selective Robotic Conformal Coating Processing: Rule 11 “Why do you want to coat the edge of a circuit board”
Conformal coating works by protecting the components and stopping conduction through leakage between leads and devices. Most of the time the edge of the circuit board does not need to be coated. So, why specify that it should be?
Rule 11
Make coating the edge of a PCB optional – it is tricky and messy, especially if there is no frame or breakout around the board, and is of questionable efficacy in improving coating or reliability performance.
The Rules
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.
Designing for Selective Robotic Conformal Coating Processing: Rule 10 “Treat connectors with respect!”
Conformal coating and connectors are the ultimate problem for processing with a spray valve or gun. Any coating close to a connector could wick (suck up into) a connector very easily and ruin the component. Therefore, a strategy for handling coating around connectors is required.
Rule 10
Use conformal coating gel around connectors if you want to get close to the connector with the material. Conformal coating materials will flow freely into unsealed connectors and wick up connector leads.
The Rules
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.
Designing for Selective Robotic Conformal Coating Processing: Rule 9 “A flat board is a happy conformal coating process”
Many printed circuit boards can become warped in the manufacturing process. Or, they can bend in the conformal coating process if not adequately supported. This means that the surface is not even for the valves to travel across. For processes where the valves are running very close to the surface of the board this can be critical and lead to defects.
Rule 9
The board should be flat and sufficiently rigid to prevent sagging during dispensing or curing, otherwise coatings may flow and pool in unexpected fashions. In particular, heavy boards may need to be palletized to provide sufficient rigidity.
The Rules
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.
Designing for Selective Robotic Conformal Coating Processing: Rule 7 “Add tooling holes for the PCB if the board is not a standard shape to be supported on the fixture or conveyor”
Many PCBs can be irregular in shape or have components very close to the edge. This can make it very difficult to support the circuit board on a fixture or even worse on a moving conveyor. So, this may mean it is difficult to get the position to be repeatable. If the position is unrepeatable then the coating will go where it is not wanted.
Rule 7
Add tooling holes for the PCB if the board is not a standard shape to be supported on the fixture or conveyor.
The Rules
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.
We have no facilities for RFI Shielding Coating application? What can SCH offer?
SCH can offer any solution the customer requires.
We can offer a global subcontract coating service across north America, Europe and Asia, we can provide in house coating services where we set the facility up inside a company and complete the process for them or we can provide spray equipment, RFI shielding paints from MG chemicals and the training for the customer to process the boards themselves.
Click RFI Shielding Coating Application to find out more or contact us directly to discuss your needs.
How do I spray PCBs with coating without ruining the ESD board I am spraying onto and meeting ESD requirements?
There are several ways and no ideal solution. Basically, you can spray onto boards that are covered in paper or ESD bag material which will then earth to the turntable of the booth. Since the operator should be earthed via the ESD points or the floor then you creating good protection for the device.
However, it is important to change the material regularly since a build up of coating turns the material to an insulator fairly quickly!
Click Conformal Coating Spray Equipment FAQs to find out more about this and other issues relating to the process.
Conformal Coating 