Tag Archive | system

Why is Parylene used for waterproofing circuit boards?

Parylene is a completely homogeneous coating. That means it is the same thickness all over the circuit.

This is achieved by the coating being applied as a vapour and the coating condensing onto the circuit board uniformly.

This uniformity of coating means that the water cannot easily come into contact with the circuit and cause shorts.

To find out more click Parylene Application Process

SCH provides Parylene Machines from Paratronix. SCH also offer Conformal Coating Materials, Equipment, Services, Training and Consultancy.

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Can I horizontally dip my printed circuit board in conformal coating and achieve a good finish?

Dipping PCBs in conformal coating

Dipping PCBs in conformal coating

The answer is yes.

In fact we can dip your PCBs at any angle you choose. The key is control of the dipping depth and being able to hold the PCB. If we can achieve both successfully then it is perfectly possible to horizontally dip PCBs using automated batch dip coating machines such as the DS101 dip system.

There are many factors to consider such as the size of the board, the depth of dipping allowed, the type of conformal coating to be used, how to hold the PCB and the masking & components on the board that must be considered.

However, SCH regularly use this technique to minimise costs for customers. We can develop the fixtures to support the PCBs as well as design for multiple dipping of the boards.

Click conformal coating dip system FAQs for further questions

Try our different conformal coating dip system pages to see if they meet your needs:

Or, contact us here at +44 1226 249019 or email sales@schservices.com

Questions to ask when considering a Conformal Coating Dipping Application

When selecting a conformal coating process it is important to ask the right questions.

With dip coating, the information required includes questions such as:

  1. What is the size of the Printed Circuit Board (PCB) you wish to coat?
  2. What is the typical volume of the PCBs you want to coat per day, week, month etc?
  3. Is there any masking required on the PCBs?
  4. Do you know how you would like to hold the PCBs or do you need help with fixture design etc?
  5. Is the PCB to be dipped vertically, horizontally or at another angle?
  6. What is the material you wish to use for coating the PCB?
  7. Is the material compatible with a dip coating process?
  8. Do you require a batch process (operator loads and unloads at same point) or an inline process (load one end and take off at another station)?
  9. Do you require any curing mechanism within the machine (heat cure, UV light)?
  10. Do you require any automated control processes such as viscosity material maintenance and automatic material top up?

Asking these questions ensures that a dip coating machine supplier can provide a detailed quotation on the exact machine you need for your project.

Dipping PCBs in conformal coating

Dipping PCBs in conformal coating

Dip coating is the simplest and highest volume conformal coating process to be used. If printed circuit boards are designed for dip coating the huge savings in money, time and effort can be made. For help on design rules for dipping contact us direct.

For further information on Conformal Coating Dip Coating CLICK

Or, contact us here at +44 1226 249019 or email sales@schservices.com


Ten Reasons to use Parylene Conformal Coatings on your Circuit Boards

  1. Parylene coatings are completely conformal to the surface of the PCB. This means that they have a uniform thickness and are pinhole free. As a result, component configurations with sharp edges, points, flat surfaces, crevices or exposed internal surfaces are coated uniformly without voids. This provides the best protection possible, can make the circuit board “waterproof” and is impossible to achieve with liquid conformal coatings.
  2. Parylene coatings are chemically and biologically inert and stable and make excellent barrier materials.
  3. Parylene conformal coating has excellent electrical properties: low dielectric constant and loss with good high-frequency properties; good dielectric strength; and high bulk and surface resistance.
  4. Parylene is completely transparent and can be used to coat optical elements like LEDs without changing the properties of the device.
  5. Parylene complies with USP Class VI Plastics requirements
  6. Parylene conformal coating is both MIL-I- 46058C and IPC-CC-830B listed.
  7. Parylene has achieved FDA approval of when used on devices and is well-documented.
  8. Parylene has good thermal endurance: Parylene C performs in air without significant loss of physical properties for 10 years at 80°C and in the absence of oxygen to temperatures in excess of 200°C
  9. Parylene coating completely penetrates spaces as narrow 0.01mm (10 microns)giving you a complete coverage of a circuit board.
  10. Parylene is unique in being created directly on the surface at room temperature. Room temperature formation means the conformal coating and the parts are effectively stress-free.

For further information on Parylene Coatings click

Or, contact us here at +44 1226 249019 or email sales@schservices.com

Designing for Selective Robotic Conformal Coating Processing: Rule 5 “Do not use a conformal coating as an underfill”

Under fills are used to fill the gap under components like flip chip components. The materials are specifically designed to match the coefficient of thermal expansion (CTE) of the device on the board so that any CTE change does not mean the component pops off the board or gets damaged.  Conformal coatings are not designed for this process and CTE mismatch can lead to severe damage of devices such as BGAs.

Rule 5

Do not specify the use of conformal coating as an under fill EVER. If a device needs to be under filled, specify a formulated under fill. Or, be prepared to find the component lifting off the PCB in the long term.

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.

Can the capacity of the DS101 conformal coating dip tank be reduced?

SCH can make the tank any size you want. However, there is a ratio of surface area of the tank to depth that is important. If you have too little volume of coating in relation to the surface area, the evaporation of the solvent will change the viscosity of the tank too quickly and you will constantly be monitoring it. We have no formula for this but making it too shallow could be a problem.

Click Conformal Coating Dipping FAQs to find out more about this and other issues relating to the process.

How is the height of the conformal coating material in the tank controlled on the DS101 dip coating system?

On the DS101 dip coating system there are two parts to the tank. These are the dipping area and the sump, which are separated by the weir edge. The material is pumped into the tank, over the weir into the sump. Therefore, the weir edge holds the height constant and the weir sump drops with material use.

Monitoring the weir sump depth is crucial again to learn how fast it is drained. We recommend a 25mm (1”) edge difference between the top of the weir and the sump material and keeping the material close to that avoids a wide evaporation area over the weir which means more solvent evaporation. This can also be critical with materials that do not re-dissolve into the material when dry like water based coatings. If they do dry /cure then these bits float around in the sump and then eventually could clog the pump. We would recommend using a stainless steel basket which we have designed to catch these bits like a sieve and any other bits floating (or even PCBs dropped!).

Click Conformal Coating Dipping FAQs to find out more about this and other issues relating to the process.

Why are there so many different conformal coating application methods?

Coating a printed circuit board initially seems to be a straightforward process. After all how difficult can it be to apply a “varnish” to a pcb? The problem is there are so many variables to consider.

First, there is the PCB itself. you must consider its size, the components on the PCB and whether they need to be coated or must not have coating on them, what you are protecting from (moisture, water, chemicals, heat etc) and the volume to be processed?

Once these details are understood then you have to select a conformal coating material. But, selecting a coating influences the application process. For example, choosing a UV cure coating obviously means a UV cure conveyor is required. But, it also means certain robotic valves cannot function in general with these materials. So, coating selection automatically influences the application method.

In fact, the material, the PCB and the application method must be considered as a whole to give you the best chance of developing the optimum process for costs, time and protection.

Click Which conformal coating application method should I choose? Do I dip, spray or brush? to find out more.

SCH have an option of automatic viscosity control and top up system for the DS101 dip coating system. Can you advise how this works?

Automated viscosity control is a sophisticated process reserved for companies who are going to process a lot of PCBs and change the viscosity of the tank a lot of times in a shift or for companies who want a totally closed loop process without manual adjustment.

The viscosity system is an inline viscometer with feedback monitoring the tank constantly. There is a dosing system that would adjust the coating as required, feeding back into the conformal coating tank either conformal coating material or conformal coating thinners.

Click Conformal Coating Dipping FAQs to find out more about this and other issues relating to the process.

What is an airless, non-atomised film coating valve and how does it affect my conformal coating robot process?

This type of valve design relies on generating sufficient fluid pressure to force the valve through a shaped valve opening to form a leaf-shaped fan pattern.

Conformal Coating Non-atomised airless robotic spraying

Conformal Coating Non-atomised airless robotic spraying

What you get, if several other conditions are near perfect, is a wide fluid stream with a well-defined edge as seen in the picture below.

Conformal Coating applied by a film coating valve

Conformal Coating applied by a film coating valve

To find out more about this and other valves for conformal coating application click Choosing the Right Valve for a Selective Robotic Conformal Coating Application Process