What is plasma cleaning?

March 23, 2017 Blog, Plasma, Plasma cleaning

Plasma cleaning is a process of using plasma energy to clean and modify the surface of a substrate like a circuit board assembly.

It is a highly effective surface cleaning and treatment process before application of conformal coatings and is gaining more popularity due its highly effective performance.

What is Plasma?

Plasma is the energy-rich gas state (also known as the fourth state of matter) that can be used to modify the surface of a product to improve its performance.

Plasma technology is based on a simple physical principle.

Matter changes its state when energy is supplied to it. Solids become liquid. Liquids become gas.

If additional energy is then fed into a gas by means of electrical discharge it eventually ionises and goes into the energy-rich plasma state, plasma is created.

This modification can be improving the adhesion of a conformal coating or change the surface characteristics of the board.

How is Plasma used for improving the performance of coatings with printed circuit boards?

For electronic circuit surfaces, plasma treatment can be used in two highly effective ways.

That is it can:

Clean the surface of the circuit board. The surface will be free of residues and 100% contamination free including release agents and additives.
Activate the surface of the circuit board assembly. This will allow easier bonding and better adhesion of conformal coatings.

These properties make it an interesting technique for improving the surface performance of an electronic circuit board.

In fact, plasma treatment can clean, activate or coat nearly all surfaces. These surfaces include plastics, metals, (e.g., aluminum), glass, recycled materials and composite materials.

This means the plasma process can be highly effective on many different products.

For electronic circuits, plasma treatment can be used in two highly effective ways. First, it can clean the surface of the circuit board. Second, it can activate the surface of the circuit board assembly to allow easier bonding and better adhesion of conformal coatings and materials like Parylene.

What are the typical plasma processes available for surface treatment?

There are traditionally three types of plasma treatment:

Low-pressure plasma
Corona treatment
Atmospheric pressure plasma

Low-pressure plasma

These plasmas are generated in closed chambers in a vacuum (10-3 to 10-9 bar).

They can be used in conjunction with Chemical Vapor Deposition (CVD) coatings like Parylene before application.

Corona treatment

Corona treatment (corona process) is a physical process involving high voltage and is mainly used for treatment of films.

This is normally not suitable for electronic circuit boards.

How is the plasma applied to a circuit board to clean and activate the surface?

For materials like liquid conformal coatings then atmospheric pressure plasma is an excellent process for cleaning surfaces and improving adhesion and surface energy performance of circuit boards for conformal coatings.

Atmospheric plasma is generated under normal pressure. This means that low-pressure chambers are not required.

The plasma is created with clean and dry compressed air and does not require forming gases. It is possible to integrate plasma directly into manufacturing processes under normal pressure conditions.

Typical plasma components used for cleaning surfaces on circuits are:

Plasma jets (nozzles) to apply the plasma to the surface of the circuit board. They could be controlled by a robotic system.
The plasma generators that create the plasma to clean or supply the coatings as required. They provide output power and, in conjunction with complete pretreatment stations, assume various control functions.
The process monitoring that controls the nozzles, the movement of the system and the quality of the output.

These three parts form the plasma cleaning process.

For Chemical Vapor Deposition (CVD) coatings like Parylene then low-pressure plasma can be used in the chamber before application.

These plasmas are generated in closed chambers in a vacuum (10^-3 to 10^-9 bar).

Want to know more about plasma cleaning and conformal coating performance?

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

How to clean “no clean” flux residues and get it right

March 21, 2017 Blog

Cleaning the residues left behind by a no clean flux process is one of the most difficult tasks when considering cleaning.

After all, the residues left on the circuit board are not formulated to be cleaned away easily.

How do you clean no clean flux residues if you need to?

Whether a flux residue can be cleaned effectively depends on the cleaning materials saponification factor and its compatibility with the residues.

Saponification is the ability of the no clean residues to be softened to the point of being able to be dissolved by the alkali content (the saponifier) of the cleaning chemistry. The higher the saponification factor of the cleaning fluid the easier it is to clean the residues.

So the key here is to ensure that the saponifier completely dissolves the residues.

What happens if the residues are only partially dissolved?

A no-clean residue that is only partly cleaned away may be far worse for a printed circuit board assembly (PCBA) than a no-clean residue left untouched.

One of the reasons is because lead free flux activators are more active than those in earlier leaded flux formulations.

In a no clean flux, when un-cleaned, the residues are locked up in the carrier resin matrix. They are stable (benign) at normal operational temperatures and therefore will not leach out dangerous residues and cause corrosion problems.

However, if the protective matrix around the residue is partially removed by an inadequate cleaning regime, then the activators could be exposed.

This may lead to a corrosion process starting on the circuit board. Further, this process could be accelerated in the presence of heat, power on the boards in service or high relative humidity.

So how do you clean “no-clean” residues?

It is important when considering cleaning “no-clean” residues on a circuit board that you consider three points:

Can you actually clean the residue to be cleaned effectively?
Have you matched the cleaning chemistry with the relative degree of difficulty and the available process?
Have you validated the whole process by careful testing?

Consider these three points and it may help you be successful. Not considering these three points could easily lead you to having real problems in the long term.

Want to know more about cleaning no clean fluxes or cleaning circuit boards?

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

The ABCs of Atomic Layer Deposition (ALD)

March 16, 2017 Blog, Uncategorized

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

Introducing a new coating that could offer the ultimate protection for LEDs without compromise to performance or process cost

March 14, 2017 Blog

The need to protect LEDs from the long –term exposure of a harsh environment is becoming more and more required. This is doubly so for LEDs used outdoors.

The alternative coatings used to protect LEDs are many. They include Parylene, conformal coatings, ultra-thin fluoropolymer materials and encapsulates.

However, none of the material processes offer the perfect protection without adding significant cost to the production process, and ultimately the circuit board and product.

Further, to reduce costs in production some of the coating materials used compromised performance. So, there is a typical balance of costs versus protection.

Now, this may all change with the introduction of a very new coating process that takes many of the performance benefits of the best coatings but does not suffer the associated problems of increased production costs.

This process is a hybrid ALD (Atomic Layer Deposition)/CVD (Chemical Vapor Deposition) technique.

So what is a Hybrid ALD / CVD technique?

Most people in conformal coating have heard of Parylene. Parylene is a CVD (chemical vapor deposition) process where the Parylene material is applied in a vacuum chamber and the coating builds up on the surface of the circuit.

The new hybrid process uses CVD as one of its film processes. However, how it differs is that the method also uses another technique, ALD (atomic layer deposition).

Further, these two processes, ALD and CVD are applied sequentially. They are deposited as ultra-thin coatings (nanometer scale thickness) one on top of the other.

This build up of multiple layers of ultra-thin coatings (alternating ALD and CVD films) with differing coating properties produces a completely different hybrid coating that outperforms the individual coatings produced by ALD and CVD alone.

Further, the final layer applied is a hydrophobic barrier that further enhances the performance of the coating.

So how does the hybrid film differ to traditional materials like Parylene and liquid conformal coatings for protecting LEDs?

First, the hybrid coatings protective performance has been found to be superior to them all in most categories of testing so far. It provides both improved electrical and physical properties that protect the circuits.

A major issue for LEDs is light loss when the film is applied over the LEDs. For the hybrid coating the coating shows zero loss of light and this is a great advantage.

Also, the material is both temperature and UV stable. The coating will survive up to 350C and does not degrade in UV light. Again, these are great advantages for the performance of the hybrid coating.

It is also hydrophobic. This property rejects water from the surface and improves the film properties enormously.

However, what makes this coating exceptional is its final property. That is the coating does not require the circuit board to be masked when the coating is being applied!

So, why does the hybrid film not need masking like other traditional conformal coatings and Parylene?

The difference is film thickness.

The hybrid film is much thinner than the other traditional coatings including Parylene. Typical film thicknesses can be as low as 0.1um.

Since the coating is extremely thin (<< less than traditional coatings) then it has been found that no masking is required.

This is because when components like connectors are joined together then the ultrathin coating does not prevent electrical connection. The component mating parts connect together and no loss of connection can be measured.

Even better, the physical protection of the film is not compromised. In fact, all of the components including connectors are protected.

This means that the cost of process is purely the cost of application of the material and nothing else.

Since the process is relatively low cost then this does offer a very interesting alternative to the traditional coating materials in LED processing.

Doesn’t the hybrid ALD / CVD process sound complex to operate?

Actually, although the technology and chemistry can be a little complex the process itself is fairly simple.

Once the process is set up in the machine the operator just loads, switches the machine on, waits for the coating to be applied and unloads on completion.

This is a far cry from the sophisticated processes of robotic selective coating or the challenges of Parylene. Further, the application process is actually very stable and in reality is tried and test in other industries for a long time.

So, how well did the hybrid coating perform in protecting the LEDs?

Nexus, an online conformal coating database, actually worked with live LED circuits from a customer and tested the hybrid ALD / CVD material.

The customer LED product was an outdoor application. The LED customer used their own in-house test methods to prove the technology.

As part of the testing the LED circuit was exposed to tests for resistance against salt, moisture and temperature.

The test methods included:

Initial test submerged in DI water dip for 12 hours
Second test submerged in 25% concentration saltwater dip for 17 hours
Third test 2 x 6 hour cycles in water ramped from room temperature to 70°C

After each test the boards were tested for failure or problems.

The LED circuit passed on all tests. All results achieved were completed with no masking of components and zero light loss in LED opacity.

The electrical connections were found to be excellent and the coating did not affect the integrity of the connectors.

So what about the cost of process?

Since the hybrid film process is masking and de-masking free then the cost per unit is incredibly low. This makes the material superior to nearly all the traditional methods of coating protection.

Further, the protective properties of the hybrid coating in nearly all cases is superior to the conventional methods.

So, you get a lower cost coating with a higher technical performance.

So, just how good is the hybrid ALD / CVD coating as a protective material for electronics?

Generally, with protective coatings for electronics then Parylene is considered the gold standard in most cases.

So, Nexus compared Parylene with the hybrid ALD / CVD material.

Property	Parylene	ALD/CVD Coating
Hardness	Soft	Hard
Wear resistance/Handling Ease	Poor	Excellent
Water Vapor Transmission Rate	Good	Excellent
Temperature Resistance (extended time)	100°C	350°C
Color	Gray/white	Clear
Adhesion to various materials	Poor	Excellent
Scalable to large production	Poor	Excellent
Process Time	8 – 12 hrs	8 – 12 hrs
Hydrophobicity	Good	Good – Excellent
Cost	High	Low – Med

Table courtesy of Nexus

What Nexus also identified for the material were some key properties for LEDs.

The Water Vapor Transmission Rate (WVTR) is superior to Parylene so the coating is far more waterproof for the LEDs
Coating adhesion is superior as it covalently bonds to the substrate. So, the lifetime of the material will be better on the circuit.
The hybrid coating is UV stable whereas Parylene in general is not. This is an important criteria for coatings exposed outside on LEDs
The coating stayed 100% transparent during testing (no loss of lux). That again is important for LEDs.
The coating thickness of the hybrid material is x10 LESS than the Parylene. This aids light transmission and electric connectivity
The film is hydrophobic so repels water and aids the performance of the coating.

So, in reality the hybrid ALD / CVD material could just be what the LED industry is looking for in protecting their circuits.

Nexus will be performing further tests on the material to see how it performs on other types of circuits shortly.

Need to find out more?

For further information on the hybrid ALD / CVD materials then contact us directly. We can help you trial the coating.

Or, check out the Nexus article, Coating LEDs with a hybrid ALD / CVD Process.

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

What are conformal coating masking boots and how can they save you money?

March 10, 2017 Blog, masking boots

The use of masking materials such as tapes, dots and liquid latex can be a highly effective process in protecting components from ingress of conformal coating.

However, the masking process can be labour intensive, difficult and time consuming.

Using reusable, custom masking boots offers a labour saving alternative in both the masking and de-masking stages of the coating process.

This can save you lots of time and money.

masking boots

Three simple reasons why conformal coating masking boots can save you money

Masking time is reduced. Using masking boots as an alternative can be 4-5 times quicker than masking tape.
De-masking time is reduced. Again it is much quicker to remove masking boots than tape
Masking boots don’t leak as easily as tape. So there is less chance of a need to repair or remove leaked coating.

This means you can save a lot of money very quickly when switching to custom masking boots.

How Diamond MT saved nearly 60% of their process time switching to masking boots

Diamond MT, a conformal coating and Parylene coating service provider, found they saved 60% of their current costs by switching to the SCH range of conformal coating masking boots.

Sean Horn, Diamond MT, explains how they did it.

“We had initially wanted to try SCH’s conformal coating masking boots for price savings. However, once we began to work with Lee on our specific masking application, we realised that we could extend the life of our boots over 200%. We switched immediately!

We then realised the importance of working with someone who understands conformal coatings. We will not being going back to our previous supplier.”

Sean Horn, Director, Diamond MT, Parylene and conformal coating subcontract service provider.

Find out how much you can save by switching to custom boots

We are happy to provide a quotation for our masking boots so you can see for yourself how much you can save.

Just provide us with three pieces of information:

Provide a picture of the board you wish to test
Identify the components you need to mask
Provide the component identification codes (manufacture details etc)

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

What is Plasma coating?

March 7, 2017 Blog, Plasma, Plasma coating

Plasma coating is the application of a nano-coating material onto a surface via a plasma.

Using a jet nozzle the material is supplied to the plasma. Next, the plasma excites the material and this increases the coatings reactivity.

This extra reactivity allows the material to optimally cover the surface of the substrate and bond much tighter.

The plasma coating process can be adjusted individually to the substrate. It can be used to coat different materials like metals, glass, ceramics and plastics.

These nano coatings can be made to be hydrophobic (water repellent) and hydrophillic (water absorbant) depending on your requirements.

Examples of plasma coating applications include:

Improvement of barrier characteristics of plastics for packaging
Improved paint application with long-term stability and resulting high flexibility in manufacturing
PT Release coatings, for injection molding tools, allow a high number of process cycles without the components having to be stressed with release agents that contain silicone.
PT Bond coatings assuring long-term adhesion in the adhesive joint.
Corrosion protection coatings that offer extremely high corrosion protection with long term resistance to corrosive electrolytes (especially for aluminum alloys) because of their good barrier effect

Want to know more about plasma coating and protecting your products?

Contact us

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

The ABCs of plasma cleaning for conformal coating

March 2, 2017 Blog, Plasma cleaning

The ABCs of plasma cleaning for conformal coating

Plasma cleaning is a process that is gaining more popularity in thin film applications due its highly effective performance on cleaning and modifying surfaces.

It is also a highly effective surface cleaning and treatment process before application of conformal coatings.

Plasma circuit treatment of circuit board narrow

What is Plasma?

Plasma is an energy-rich gas state that can be used to modify the surface of a product to improve its performance. This modification can be improving the adhesion of a conformal coating or changing the surface characteristics.

Plasma technology is based on a simple physical principle.

Matter changes its state when energy is supplied to it. Solids become liquid. Liquids become gas.

If additional energy is then fed into a gas by means of electrical discharge it eventually ionises and goes into the energy-rich plasma state, the fourth state of matter.

Plasma is created.

How can Plasma be used for cleaning printed circuit boards?

Plasma treatment can clean, activate or coat nearly all surfaces. These surfaces include plastics, metals, (e.g., aluminum), glass, recycled materials and composite materials. This means the plasma process can be highly effective on many different products.

For electronic circuit surfaces, plasma treatment can be used in two highly effective ways.

That is it can:

Clean the surface of the circuit board to be 100% contamination free. The surface will be free of residues and contamination including release agents and additives.
Activate the surface of the circuit board assembly to allow easier bonding and better adhesion of conformal coatings. It can change the surface energy of the surface to ensure complete adhesion is possible and in some cases it can make materials bond where it was previously impossible.
These properties make it an interesting technique for improving the surface performance of an electronic circuit board.

What are the typical plasma processes available for surface treatment?

There are traditionally three types of plasma treatment:

Low-pressure plasma
Corona treatment
Atmospheric pressure plasma

Low-pressure plasma

These plasmas are generated in closed chambers in a vacuum (10-3 to 10-9 bar).

They can be used in conjunction with Chemical Vapor Deposition (CVD) coatings like Parylene before application.

Corona treatment

Corona treatment (corona process) is a physical process involving high voltage and is mainly used for treatment of films.

This is normally not suitable for electronic circuit boards.

Atmospheric pressure plasma

Atmospheric plasma is generated under normal pressure. This means that low-pressure chambers are not required.

The plasma is created with clean/dry compressed air (plant air) and does not require forming gases. It is possible to integrate plasma directly into manufacturing processes under normal pressure conditions.

This is an excellent process for improving adhesion and surface energy performance of circuit boards for conformal coatings.

How is the plasma applied to a circuit board to clean it?

Typical plasma components used for cleaning surfaces on circuits are:

Plasma jets (nozzles) to apply the plasma to the surface of the circuit board. They could be controlled by a robotic system.
The plasma generators that create the plasma to clean or supply the coatings as required. They provide output power and, in conjunction with complete pretreatment stations, assume various control functions.
The process monitoring that controls the nozzles, the movement of the system and the quality of the output.
These three parts form the plasma cleaning process.

What sectors is plasma treatment used?

different technologies that have been plasma cleaned or treated

There are many sectors that plasma cleaning is used for improving conformal coating performance.

They include:

Automotive
Telecommunications
Mobile phone and Tablets
Aerospace
Military
Transport
Consumer goods
Life sciences
LED Coating

Want to know more about plasma cleaning and conformal coating performance?

Contact us

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