Using custom masking boots for the conformal coating masking process saves time, money and improves quality.


The use of various masking materials such as tapes, dots, and liquid latex can be an effective process in protecting components from ingress of conformal coating on a printed circuit board assembly.

However, the masking process can be difficult and time-consuming. This can increase the process costs significantly.

In fact, in many cases, the masking and de-masking processes can be >75% of the actual conformal coating process time and costs.


Using recyclable masking boots as an alternative to masking tapes, dots, and latex

Three reasons to switch to reusable conformal coating masking boots

Here are three good reasons to change to masking boots and save up to 80% of your costs compared to traditional methods like masking tape and dots:

  1. The masking time is reduced significantly. Masking boots can be 4-5 times quicker to use than masking tape.
  2. De-masking time is reduced significantly. Again it is much quicker to remove masking boots than tape.
  3. Masking boots don’t leak as easily as masking tape. So, there is less likely to be repaired.

These reasons mean you can save a lot of money very quickly when switching to masking boots.


Want to find out more about conformal coating masking boots?

Contact us to discuss your needs and let us explain how we can help you.

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WHY DOES THE SOLIDS CONTENT OF MY CONFORMAL COATING MATTER FOR COSTING A PRINTED CIRCUIT BOARD FOR APPLICATION?


The amount of solids content in a conformal coating is the amount of actual material available to be applied to the circuit board and that will protect the circuit board assembly.

The more solids you have the more circuit boards you can coat.

So, you want to have as many solids as possible per liter when you buy the material.


Caution –Check the conformal coating solids is at the right viscosity for application!

You also need to take care when comparing individual materials from different companies.

The differences in both solids content and viscosity can be striking and you can be wasting a lot of money on solvents that literally evaporate away.

The first stage in checking this is to determine the final solids content of the material that you will use in production. That is the correctly blended coating ready for application at the right viscosity.

Take the following example that is typical of conformal coatings sold commercially around the world.

Material X is 35% solids as sold.

Its viscosity is 190 cps approx. at this solids content.

However, to spray the coating it must be at 24 cps approx. So, the coating must be diluted by 50% with thinners to reach this viscosity.

This means material X is now 17.5% solids and a viscosity of 24 cps approx. This also means there is >80% of the material that evaporates away!


Check the market!

You cannot assume that all conformal coating materials are similar.

For example, SCH have a UL approved acrylic conformal coating that is 44% solids at 24 cps and ready to spray.

Comparing Material X (17.5%) and this particular material means that the higher solids coating has more than twice as much coverage power for the same liter of material.

If the coatings are similar in price at this viscosity then you need to buy at least 2x more of material X than the higher solids product to get the same coverage.

Quite a saving can be made if care is taken!


Want to find out more about coating coverage?

If you would like a spreadsheet that you can just punch the values in to calculate coating coverage and costs per PCB then contact us directly and we can send it through to you to help you.

Contact us to discuss your needs and let us explain how we can help you.

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Are there design rules for applying conformal coatings?


Conformal coating is not simply a consumable material. Unfortunately, for too many designers, conformal coating is simply a part number, to be applied to circuit boards.

However, this can be a major problem especially in the conformal coating production stage of the process.

There are guidelines in the IPC standards that may help with Design for Manufacture (DFM) principles. These are worth considering.

Unfortunately, there are no official design guidelines that will help directly with the application process and conformal coating.

Unfortunately, for too many designers, conformal coating is simply a part number, to be applied to circuit boards. However, this can be a major problem especially in the conformal coating production stage of the process.
Unfortunately, for too many designers, conformal coating is simply a part number, to be applied to circuit boards. However, this can be a major problem especially in the conformal coating production stage of the process.

Nexus Design Rules

Nexus, the independent conformal coating knowledge base, has developed both guidelines for conformal coating reliability and conformal coating process.

Their philosophy is that for companies embracing lean philosophies and applying conformal coatings, a failure to appreciate the subtleties of the application process can result in an uncoatable (at least as specified) assembly process.

They also state that 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.

Nexus have design rules for both general processing and for specific application processes such as dipping, selective coating and batch spraying.

For further information visit conformal coating design rules to learn more.


Need to know more about conformal coating design rules?

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Do you need MiL spec qualification for your conformal coating?


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Normally, customers know if they require MIL-I-46058C qualification for their conformal coating. It normally is required if it is a military product.

However, caution should be shown when examining conformal coating datasheets that state MEET the requirements of MIL-I-46058C since the conformal coating will likely not be on the Qualified Product List (QPL).

What is the Qualified Product List (QPL)?

The Mil Standard for conformal coating has been inactive for new designs since November 1998. However, the standard is still widely used for independent certification of conformal coatings.

All companies tested to the MIL-I-46058C standard are listed on the QPL. It is still possible to register the coating on the list.

Conformal coatings listed on the QPL will have been through rigorous 3rd party testing to confirm they meet the standard. They are not self-certified.

So, if you require a conformal coating material that is Mil-spec approved then it will have to be on the QPL and it will have been independently tested.


Need to know more about Mil Standard conformal coatings?

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Give us a call at (+44) 1226 249019 or email your inquiries at sales@schservices.com

The ABCs of Atomic Layer Deposition (ALD)


What is ALD?

Atomic Layer Deposition (ALD) belongs to the family of Chemical Vapour Deposition methods (CVD).

It is a deposition process at a nano-scale level within an enclosed vacuum chamber.

The deposition process forms ultra-thin films (atomic layers) with extremely reliable film thickness control.

This provides for highly conformal and dense films at extremely thin layers (1-100nm).

What coatings are deposited in ALD?

ALD principally deposits metal oxide ceramic films.

These films range in composition from the most basic and widely used aluminum oxide (Al2O3) and titanium oxide (TiO2) up to mixed metal oxide multilayered or doped systems.

How does ALD work in practice?

The ALD deposition technique is based upon the sequential use of a gas phase chemical process.

Gases are used to grow the films onto the substrate within a vacuum chamber.

The majority of ALD reactions use two chemicals called precursors. These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner.

Through the repeated exposure to alternating gases there is a build up of a thin coating film.

Where is ALD used?

ALD is used in many different areas including:

  • Micro-electronics
  • Semiconductors
  • Photovoltaics
  • Biotechnology
  • biomedical
  • LEDs
  • Optics
  • Fuel cell systems
Advantages and disadvantages of ALD

Advantages

  • Self-Limiting. The ALD process limits the film thickness. Many other processes like Parylene are dependent upon amount of dimer and will continue to deposit successive polymer layers until it is completely used up.
  • Conformal films. ALD film thickness can be uniform from end to end throughout the chamber. Other coatings like Parylene can have a varied coating thickness across the chamber and the devices being coated.
  • Pinhole free. ALD films can be pinhole-free at a sub-nanometer thickness. Parylene and some other materials are only pinhole-free at micron levels.
  • ALD allows layers or laminates. Most other films including Parylene are single component layers.

Disadvantages

  • High purity substrate. This is very important to the quality of the finish similar to many other vapour deposition processes.
  • ALD Systems can range anywhere from $200,000 to $800,000 based on the quality and efficiency of the instrument. This tends to be 3-4 times the prices of a Parylene system.
  • Reaction time. Traditionally, the process of ALD is very slow and this is known to be its major limitation.
  • Masking challenges. The ALD masking process must be perfect. Any pinhole in the masking process will allow deposition beyond the masking barrier.
What are some of the ALD coatings that can be deposited?

A wide variety of chemistries are possible with Atomic Layer Deposition.

They include:

  • Oxides
  • Nitrides
  • Metals
  • Carbides
  • Sulfides

Want to know more about Atomic Layer Deposition (ALD) coatings?

Contact us now!

Call us on +44 (0) 1226 249019, email your requirements on sales@schservices.com