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Modern technological advances have seen electronic systems integrated into nearly every facet of life and environment. Delicate electronics are no longer simply working in dedicated machine rooms, but are instead being carried around in our pockets, through deserts, and oceans. These environments present potential threats to the backbone of modern computing – the printed circuit board. Conformal coatings have been developed to combat exactly the kinds of threats most frequently experienced in different situations. They also add a level of protection to circuitry in critical applications like power plants or emergency services.

Conformal coatings – so named because they conform to the physical structure of their substrate, can be made out of a number of different materials including acrylic, silicone, urethanes, epoxies as well as parylene. New types of coatings, like synthetic rubber, are also being developed to meet specific demands. These coatings offer different types of protection as well as application methods/cure and ease of rework. A number of factors need to be considered when finding the right conformal coating. The first factor to take into account is the type of environment the compone
nt will be used in. Most components benefit from some coating because moisture and dust can affect systems in almost all environments.

Conformal coatings also offer varying levels of dielectric insulation to protect from internal or external shock. Aside from these everyday concerns, components in high-stress environments need special consideration. Determining the direct exposure to abrasion, heat and cold, and amount of mechanical stress and vibration will help narrow down the possible coatings. Reworking is important to plan for if the underlying components will need to be repaired. Coatings are usually removed for repair by abrasion, burning through, or use of chemical strippers – depending on the type.

 

Types of Conformal Coating

Acrylic conformal coatings are one of the most commonly used conformal coating bases for general use. They are relatively easy to apply, quick to cure without heat or shrinkage and are easy to rework when repairs are needed.

Urethane conformal coatings generally provide a better chemical resistance than acrylics, but that chemical resistance can also make them more difficult to remove for repairs. Cure time for urethanes are also longer, particularly with one-part formulations. Two-part formulations can reduce cure-time at the expense of shorter pot-time and the added necessity of mixing.

Epoxy Conformal Coatings offer excellent abrasion and chemical resistance, but can also be difficult to remove for repairs. They have a relatively short cure time, but care must be taken since shrinkage can occur with some formulations that could potentially damage delicate parts.

Silicone conformal coatings usually need to be removed by abrasion for repairs, but offer some unique advantages. These coatings are highly flexible, which makes them ideal in situations where operating temperatures are expected to reach up to 200C. They can also provide mechanical shock resistance for the same reason. They are ideally suited to the oil and gas industry because of their resistance to specific chemicals, as well as other high-temperature applications like automobiles.

Parylene is the widely used name for poly para-xylene. This coating offers exceptional protection from a number of elements, and provides the most uniform board coating. Parylene has also been FDA approved for use in medical applications. However, these advantages come at a cost – parylene coating requires specialty application using vapor deposition polymerization, and surfaces must be impeccably clean before coating. This coating is most often used in harsh environments or military applications.

 

Cure-types

Many of the types of coating can be cured with different methods, which offer different advantages and disadvantages. Solvent-evaporation curing is the simplest cure for acrylic, urethanes and epoxies, but can take a longer time – particularly with urethanes (upward of one week). These solvent-borne coatings can also be subject to VOC regulations. Water-based and other low-VOC or non-VOC coatings are available but are also more costly.

Heat curing, which can greatly shorten cure-times, is an option for some coatings, but requires a specialized setup for temperature control and is more prone to shrinkage that can damage delicate assemblies.

UV-curing conformal coatings afford the quickest cure times – in a matter of seconds – and can be a viable option when production speed is paramount. However, this method requires other factors to be taken into consideration, since shadowed areas of the PCB may not cure fully, and shrinkage can be an issue.

 

Other Considerations

Most conformal coatings are applied in one of two methods – dipping or spraying. When applying a coating, masking must be applied to the PCB where the coating is not desired. Dipping and spraying with selective robotic coating can lower the amount of masking required by utilizing specific component placement or designed application. Spraying by hand or over the entire board requires more extensive masking – as does the Vapor Deposition Polymerization (VDP) process. Brushing is usually not used for production, but can be used to repair some coatings. Altering the viscosity of a coating by the use of thinners can allow precise control over the thickness of coating.

Boards with intricate geometries or sharp edges need special consideration since coating these areas can be difficult. Dipping can provide adequate coverage with special care, but parylene also excels at coating these types of boards.

While conformal coatings protect against many kind of contamination and environmental risks, they can make components less resistant to fire. UL standard 764E measures the resistance of coated boards to fire and there are a number of coatings which meet the highest (V-0) standard.

Adequately checking that a coating has been applied in the desired thickness and coverage is critical. To make this task feasible, many coatings contain tracers that are visible only under UV light for inspection.

These coatings provide excellent general protection from a number of environmental factors, and individual formulations can provide specific safeguards against other stresses. However, they may be inadequate to protect some components. Potting with other compounds in conjunction with a conformal coating may be required. As always, determining what the components will encounter throughout their working life, as well as production needs, will help determine exactly what kind of protection is needed.

The content for this month’s blog post was provided by Gluespec®  – a partner of Ellsworth Adhesives.

Gluespec helps engineers to discover adhesives and other materials for their industrial applications.

Shop Conformal Coatings Now. 

Anaerobic adhesives offer an excellent way to adhere metal components in the absence of oxygen, without the need for light or heat. Because of their unique properties, anaerobic adhesives are applied mainly as threadlockers – to fix bolts and screws in metal assemblies. They can also be used in airtight plastic assemblies like those with nylon threads, with the use of an activator. Anaerobic adhesives also have secondary properties that make them advantageous as a sealant in those applications. These adhesives are a useful alternative in other tight-fitting metal-metal connections where press or shrink – fits would have been the only other method of connection.

Anaerobic adhesives are an acrylic polymer that bonds in the presence of metal ions. Oxygen inhibits the cure of these adhesives, which makes them ideal for threadlocking applications. Because bolts can back out, particularly under stresses like vibration in vehicles or aviation, threadlockers are often used to combat those stresses. While anaerobic adhesives usually need clean surfaces to adhere to, surface-insensitive formulations are available, as well as surface primers that can promote adhesion under different circumstances. These adhesives generally cure to fixture in minutes, curing fully within 24 hours. Application of heat can increase cure times. These adhesives generally come in specialty, air-permeable plastic containers and are only filled halfway to prevent premature curing. Transferring an anaerobic to another container or syringe can cause pre-mature curing and process difficulty. Care should be taken in handling anaerobic adhesives since they are reactive monomers and can cause potential skin damage.

 

Strengths

These adhesives are formulated in a number of different strengths. Choosing the strength of adhesives depends on a number of factors. First is the width of the bolt. Larger bolts mean larger shear forces, so strong adhesives are needed to resist those forces. Aside from size considerations, use is an important factor. If screws or bolts will need to be removed for later servicing or disassembly, weaker threadlockers need to be used that will prevent incidental backing-out, but not intentional removal. On the other hand, permanent or semi-permanent anaerobic adhesives that bond surfaces that do not later need to be removed are available. Some formulations release bonds only under high-heat, allowing extremely high adhesion, as well as removability.

 

Retaining Compounds

Although threadlocking represents a large portion of the anaerobic adhesive use, these adhesives can be used in any tight-fitting metal-metal bonding application. Assemblies that would usually be attached with shrink-fits can use anaerobic adhesives to bond pieces. This allows those assemblies to avoid some problems involved with expansion and contraction, and increases tolerance thresholds for machining of parts.

 

Special formulations

While the average threadlocker is applicable in most bolt-retaining applications, there are specialty formulations that meet the needs of particular assemblies. Viscosity can be altered in threadlockers, and very low viscosity formulations are useful for adding threadlockers to already-assembled components.

Higher viscosities can, to an extent, fill gaps, if a higher-than-normal space between threads is expected. Anaerobic adhesives usually have an operating temperature range to around 150C, but high-temperature adhesives can push that upper limit to above 200C.

 

Additional advantages

Anaerobic adhesives have a few properties that increase their value and utility beyond simple thread locking. Most importantly, threadlockers coat threads entirely and are resistant to water, solvents and oils. This allows threadlockers to serve the dual-purpose as sealants and prevent corrosion from liquids and gases that would otherwise compromise bolted assemblies. Because anaerobic adhesives don’t cure in the presence of oxygen, cleanup is easy since any excess adhesive remains as an easily wiped-away liquid.

 

Shop our range of Anaerobic Adhesives here. 

The content for this month’s blog post was provided by Gluespec® – a partner of Ellsworth Adhesives.
Gluespec helps engineers to discover adhesives and other materials for their industrial applications.

In nearly every industry from automotive to manufacturing, lubricants are integral to the long-term operation of any system with parts that come into contact with each other repeatedly. Lubricants are necessary because at a microscopic level friction between two surfaces causes the related stresses of wear and heat. These stresses lead to breakdowns or inefficiencies in systems of all kinds. Lubricants provide a physical barrier between two surfaces that would otherwise be in contact. This barrier reduces friction and can help dissipate heat. That barrier has the added advantage of keeping out dirt, air and moisture – helping to prevent rust, corrosion and contamination.

 

What are Lubricants?

Lubricants come in a variety of forms, but most liquid or semi-liquid lubricants are formed from a base oil – either petroleum-based mineral oils, synthetic oils or vegetable oils. Additives are combined with these base oils to change the properties as necessary. Dry lubricants like graphite and molybdenum disulphide can be used by themselves or as additives in other lubricants.

 

Types of Lubricant

Each type of lubricant has specific properties that make it well-suited to particular applications.

 

Oil
Oils are the thinnest type of liquid lubricant, with petroleum- or synthetic polyalphaolefin- (PAO) based formulations the most common. Because they are relatively thin liquids, they can be used where dissipating heat is necessary since they can be easily circulated through a system and cooled. Additives can be used to provide extra protection and prolong life of equipment and machinery they are used with. Their viscosity can also be modified by varying molecule chain length – lower viscosity oils are used for high speed applications like compressors, and higher viscosity oils are used for slow speed applications like gear boxes.

 

Grease
Greases are semisolid materials consisting of a lubricating fluid, thickening agent (typically mineral soap of some kind) and additives. Because they are thicker than oils, they can be used in applications where oils might eventually be cast off like high speeds or exposed surfaces. They can provide extra protection against oxidation and rust, forming a solid air and moisture barrier on coated surfaces.

 

(Silicone) Compound
Compounds are grease-like materials, but instead of the usual lubricating oils or solids, they are composed of silicone fluids and silica fillers. They have silicone’s advantage of high-temperature stability, and can also be used for sealing. They have good dielectric properties, and can be used for non-metal-to-metal lubricating and release applications. Special formulations can also be used for food and beverage applications.

 

Paste
Pastes or anti-seize compounds are similar to greases, but contain a very high percentage (over 50 percent) of solid lubricants .They can be used in high-load, low-speed applications that would be unsuitable for oils or greases. With pastes, the solid compounds are providing much of the lubrication, so even in high temperature environments where the oil carrier evaporates, a friction reducing solid-lubricant film remains.

 

Solid
Solid, dry or powdered lubricants are often components in other lubricating fluids, but can be used directly as well. The most common are graphite or molybdenum disulphide. These lubricants can provide friction-reducing properties in extreme heat, pressure and oxidizing environments where other lubricants would be ineffective or unable to withstand conditions.

 

Dispersion
Dispersions are simply solid lubricants suspended in lubricating fluids, where application of those solids in liquid form is preferred or necessary, such as mould-release sprays.

 

Anti-Friction Coating
AF Coatings or “lubricating paints” consist of a fluid carrier, a binder and solid lubricants. When applied, these materials cure to form dry, solid lubricant coatings that are bonded to the surface. They are useful for helping to prevent corrosion, do not attract dust or dirt and can provide a long-lasting, even covering of lubricating film.

 

Which Lubricant for Which Application?

Determining which lubricant to use for a specific application requires taking into account a number of factors. Using the acronym L.E.T.S. breaks down those factors into four categories.

Load – The amount of force or stress placed on the component or surface. In general, loads can be classified as heavy, moderate or light.

Environment – The operating environment, such as atmospheric pressures, humidity, water immersion, the presence of chemicals, fuels or airborne contaminants.

Temperature – The actual operating temperature, the soak temperature at standstill and the ambient temperature.

Speed – Runs from high to low, and it involves rotational and reciprocating speeds as well as frequency of motion.

 

Final Thoughts

Shop our range of lubricants here. 

If you have any questions on lubricants, we know a man who can help! Ask The Ellsworth Adhesives Glue Doctor!

The content for this month’s blog post was provided by Gluespec® – a partner of Ellsworth Adhesives.
Gluespec helps engineers to discover adhesives and other materials for their industrial applications.

 

Soldering : The Basics

While there are adhesives and other materials capable of bonding metals, soldering tends to be the preferred method of joining smaller more intricate metal components and is commonly used in the electronics production assembly line.

The soldering process involves melting and flowing a filler metal or solder, into the joint with the filler metal having a lower melting point than the adjoining metal.

Though it may sound complex, soldering is actually a fairly straightforward process, however it is crucial that you have the correct tools for the job. In this latest blog post, we explore the different soldering products and equipment available.

 

Soldering Workstation

A standard Soldering System is required for any soldering work and is comprised of three main components; a soldering iron tool, a power supply and a work stand.

The power supply transmits heat energy to the soldering iron tool by passing an electric current through a resistive heating element.

The Soldering Iron is composed of a heated metal tip and an insulated handle and the heat supplied from the tip will melt solder allowing it to flow into the joint between the two pieces to be joined. Soldering Irons normally have interchangeable tips, allowing users to change the size and shape of their hand-held soldering tool, depending on the type of work being carried out. Fine, conical tips tend to be used to be well suited to electronics applications, while pyramid tips with a flat face are perfect for soldering sheet metal.

A work stand is used to rest the soldering iron when it is necessary for the user to take a pause in the soldering process. There are different types of work stand available including ‘auto-sleep’ and ‘tip-savers’ to help prolong the tip cartridge life and most should include a cellulose sponge for cleaning solder from the tip.

MX-500 from Metcal, the global leader in the manufacture of Soldering Systems, is the go-to unit for soldering, de-soldering and convection re-work. This Bench top icon features a switchable dual port and 40 Watt operation and is available with either one hand-piece or two. Safety is at the heart of the MX-500’s design, with an AC ground monitor fitted to detect any possible power line ground failures, before alerting the user and then shutting the equipment down automatically. The MX-500 also benefits from what is known as ‘SmartHeat Technology’ whereby each cartridge is equipped with a self-regulating heater which senses its own temperature and is therefore able to maintain its pre-set ideal temperature.
Other notable features of the MX-500 include a user-programmable ‘power-save’ mode that is adjustable from between 10 and 120 minutes, as well as a universal power supply, making the equipment suitable for worldwide operation.

 

Soldering Materials

Now that we have established the core soldering equipment, let us consider the solder materials associated with the soldering process including solder, solder paste, flux, masking compounds and cleaning wicks.

Solder is a metal alloy, made up with a combination of tin and lead. Solder is normally solid – either in bar form, whereby it would be melted in a solder bath before parts are dipped into it, or wire form, which is hand fed to the solder tip then melted. Before applying solder, the surface temperature of the parts to be soldered must be elevated above the melting point of solder and to ensure a strong solder joint, these parts must be held in place until the solder solidifies.

Solder Paste is a special form of solder, often used in PCB assembly. Unlike standard solder, solder paste is liquid in form and is dispensed using a syringe dispenser. Henkel Loctite’s GC10 solder paste is the first material of its kind to boost temperature stability. The innovative formulation is temperature stable at 26.5°C for one year and stable at temperatures of up to 40°C for one month.

Flux is a crucial material in soldering process since it is used to remove and reduce the oxides that often form when hot metals mix with the air. Fluxes are composed of natural or synthetic rosins that make it very corrosive at solder melt temperatures, thus enabling it to remove any trace of metal oxide.

Masking Compounds perform a protective function in the soldering process and are used to prevent solder from sticking to the areas surrounding the joint, where solder is obviously not wanted. Dymax manufacture a range of soldering masking compounds, such as Dymax 9-318-F, a solvent and silicone free masking compound that provides rapid masking. This maskant is highly thixotropic, making it ideal for dispensing onto boards that may be difficult to mask with other methods.

Cleaning Wicks, also referred to as desoldering braids or solder wicks, are pre-fluxed copper wires used to remove excess solder and other components. By placing a length of solder braid onto the connection with a hot iron, the solder is removed as it wicks up into braid. Techspray is a leading manufacturer of Cleaning Wicks, with products available in different specifications to suit varying application requirements.

 

Top Tips for Soldering

Solder will simply not join to a greasy surface, therefore you must ensure that you thoroughly clean the area to be soldered before beginning the process.

Be careful to use just the right amount of solder! Too much solder will cause the joint to form a ‘blob’ yet too little solder will lead to a physically weak joint that may not be complete nor electrically sound.

Don’t panic if you have messed up your attempt at soldering – solder can be removed with a de-soldering tool or cleaning wick allowing you to start over again.

When you have finished soldering, allow the soldered joint to cool naturally and resist the urge to interfere with the drying process.

Before unplugging the soldering iron, be sure to clean the soldering tip on a damp sponge, before re-tinning with a fresh solder. This action will protect the tip’s tin plating and prevents the possibility of oxidisation.

After soldering, it is also important to remove flux residue with the help of a cleaning solvent or designated flux remover.

 

Over to you…
If you have any additional questions about Soldering Materials and Equipment, please get in touch with the Ellsworth Glue Doctor. As an expert in the processes of joining and bonding, he has the knowledge to answer any questions you may have and will be happy to help select the soldering system best matched to your particular application.

Shop our range of solder equipment and solder materials now.