Troubleshooting your conformal coating process: Capillary flow

Capillary flow on a circuit board due to scavengingIn conformal coating, capillary flow is where the coating pulls or runs away from areas of a PCB thus leaving a patchy finish.

Factors that causes the capillary effect are

  • Low viscosity
  • Volume of coating
  • Substrate cleanliness
  • High surface tension

However, it is possible to reduce these effects by

  • Increasing the viscosity
  • Reducing the volume of coating
  • Cleaning the board properly
  • Using a solvent-based material
  • Heating the circuit board

Read more at Conformal Coating Defects: Capillary Flow

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

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Alternative materials to traditional liquid conformal coatings

Surface modified by a  fluoropolymer conformal coatingAside from traditional liquid coatings, Parylene and fluorochemical materials serve as potential coating alternatives.

Parylene is used in a dry process wherein the coating is deposited in a gas vacuum chamber.

On the other hand, fluoropolymer surface modifiers are ultra thin coatings that are applied at a few microns in thickness.

Two of the most popular types of this ultra thin conformal coatings are

  • liquid materials that dry onto the substrate
  • materials which are applied in a partial vacuum deposition

Read more on Alternative Coatings: Overview

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

Cleaning in Conformal Coating

Cleaning of a circuit board before conformal coatingCleaning circuit boards prior to conformal coating can help prevent contamination and improve the coating process. It also ensures the long-term reliability of the board.

Various types of contaminants are eliminated when the boards are cleaned. These include manufacturing and assembly residues.

Cleaning techniques

Circuit boards can be cleaned successfully using the following methods:

  • Aqueous chemistries
  • Solvent or chemical cleaning
  • Plasma cleaning

The key is to match the circuit board with the cleaning process and the materials.

Cleaning validation

To ensure that your boards are cleaned properly, use any of the following testing methods:

  • Ionic Contamination Testing (ROSE)
  • Ion Chromatography (IC) or High Performance Ion Chromatography (HPLC)
  • Surface Insulation Resistance (SIR) testing

Read more at Conformal Coating Processing: Cleaning

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

 

Preventing Corrosion on a Circuit Board

Corrosion on a circuit boardCorrosion is the chemical or electrochemical reaction that happens between the circuit board and its environment. This results in the deterioration of the board and its properties.

Main causes of Corrosion of circuit boards

Corrosion on a PCB can be caused by many factors during the assembly process including the following:

  • Board fabrication
  • Lack of cleanliness in components
  • Assembly equipment
  • Soldering or flux residues
  • Operator handling
  • Incorrect cleaning

Preventing Corrosion

Corrosion can be stopped by doing the following:

  • Cleaning the board properly
  • Controlling the process quality
  • Inspecting thoroughly
  • Ensuring operator cleanliness
  • Choosing the correct manufacturing materials
  • Fine-tuning the solder process
  • Reworking by using low residue wire/flux

Read more at Conformal Coating Defects: Corrosion

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

What are the important physical properties of a conformal coating in production?

Conformal coating is composed of different physical properties. One of which is liquid. The liquid properties need to be defined prior to the conformal coating.

The properties include flash point, storage lifetime, appearance and colour, density, solids content, and viscosity.

Liquid properties overview:

  • Flash point: the temperature needed for an organic compound (solvent) to release enough vapour in the air
  • Storage lifetime: shelf life of the conformal coating
  • Appearance and colour: mostly clear
  • Density: measured by a pycnometer
  • Solids content: non-volatile material that remains after the coating is done
  • Viscocity: showing the internal friction in a fluid resisting flow

Read more at Conformal Coating Physical Properties: Liquid

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

 

 

A Closer Look at Conformal Coating Selective Spraying

 

Robotic Selective conformal coated PCBSelective spraying is one of the most efficient conformal coating techniques. It involves the use of a robotic program that accurately targets circuit board areas that needs to be coated. It also avoids the components that don’t need coating.

A wide range of specialist spray guns are used to achieve this kind of efficiency and selectivity. It creates a precise spray pattern during the conformal coating process.

The Basics:

  • Selective spraying can be used for all conformal coatings.
  • A specialized robotic machine is required for the application of selective coating.
  • The initial investment is high but the ROI is good as it can handle high volume of coating.
  • Operating the robotic system requires extensive skill and training.
  • It eliminates the need for masking since the spraying is targeted.
  • It is a medium to high volume process.

Variables to consider in selective spraying conformal coating:

  • The operator’s skill and extensive training
  • Quality of selective spray robotic equipment
  • Compatibility of valve technologies
  • Perfect blending of conformal coating with the right viscosity
  • Compatibility of circuit board design
  • Temperature and humidity in the location of the robotic equipment

There are advantages and disadvantages to using selective spraying. Some of the benefits include the elimination of masking, high speed coating, and high volume processing. The downside of this technique is that it requires huge capital cost and high level of skill and expertise to operate.

Read more at Conformal Coating Application Methods: Selective Spraying

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.

 

What You Need to Know About The Parylene Vapour Deposition Method

 

Paratronix Parylene ProcessVapour Deposition is a unique conformal coating technique as it is a dry process unlike other methods that are liquid-based.

The coating is applied on circuit boards through a vacuum chamber where the components are coated in batches. Parylene is a material applied during the deposition process at room temperature.

All parts that shouldn’t be coated ought to be masked prior to the vapour deposition.

The Basics:

  • It requires a specialist system that is designed for vacuum application.
  • The set up may cost significant investment initially
  • The process can handle low and medium volumes
  • Vapour deposition application is relatively simple but the initial process development can be complex
  • Coating thickness is an important parameter and calculations should be exact.
  • It is one of the most expensive coating processes but produces the best finish.

Variables to consider in vapour deposition conformal coating:

  • The operator’s skill and extensive training
  • Knowledge in preparation particularly in handling Parylene material
  • Cleanliness of the surface
  • Masking requirements
  • Circuit board design

Just like other conformal coating application process, there are advantages and disadvantages to using vapour deposition.

Some of the benefits include excellent protection due to very low permeability, high solvent and salt protection, and 100% clarity as Parylene can coat optical components. On the flipside, the capital costs are high, preparation can be challenging, and it requires the highest masking level.

Read more at Conformal Coating Application Methods: Vapour Deposition

Who is Nexus?

Nexus brings together the accumulated knowledge of a group of conformal coating and electronics material dispensing consultants who provide a unique service, focused on helping electronics manufacturing clients improve their conformal coating and electronics materials processes.

Nexus operate across North America, Europe and Asia and can provide a unique perspective to the rapidly growing conformal coating and electronics materials industry. Expertise is held in liquid and parylene coating, capital equipment sales and specifications and material, equipment and process specification, troubleshooting and training.