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Electrically Conductive Adhesives: Are They Right for Your Application?

1 December 2016 by Chelsie Grierson

The exponential rise and now nearly universal integration of electronic devices in our daily lives has necessitated the creation of advanced adhesives and coatings. Electrically Conductive Adhesives (ECAs) have worked their way into a number of fields both directly and indirectly related to electronics manufacturing. ECAs are typically composed of an epoxy resin but can also be made of UV cure and silicone adhesives. To overcome the high resistivity of these compounds, the adhesive is loaded with upward of 80 percent conductive materials. These adhesives can be applied in any number of usual ways, from syringe to screen print.

There is an enormous variation in ECAs, and choosing which adhesive is right for your application depends on a number of factors. ECAs vary depending on what conductive particles are used, as well as what adhesive they are suspended in.

Adhesives

Most adhesives can be made into conductors by adding enough conductive filler so the usual considerations about what adhesive will work best should be taken into account. Factors like application method and cure-time, as well as environmental and direct stresses the adhesive joint will be under all need to be considered. One and two-part epoxies are the most commonly used adhesives, but silicones and other UV cure adhesives are all options.

Conductive Particles

A number of metals or compounds can be used to provide the electrical conductivity in an ECA. Silver is the most common because it has a very low resistance and can be cost efficient compared to other options, such as gold. Copper, gold, nickel, aluminum and graphite are other popular options for ECAs. Certain combinations can offer other advantages – such as silver plated copper or nickel, which are often less expensive but still offer low resistivity. The exact composition of the filler and method of distribution in the adhesives can be tailored to meet the required specifications.

Silver and gold are metals that are commonly used to provide electrical conductivity in an ECA.

Major Uses

The use of ECAs can be broadly split into two categories – conductive uses and shielding uses. ECAs used as a conductive connection often use silver as the filler material, while ECAs used in shielding are most often made with less conductive materials, like graphite.

Conductive

There are two main types of ECA used as a conductive pathway – isotropic conductive adhesives (ICAs), and anisotropic conductive adhesives (ACAs). While ICAs that are conductive in all directions, ACAs are conductive only in one direction (usually along the z-axis). ICAs are used in many applications where a solder would be appropriate and a ground path is necessary. ACAs are then suited for use in some specific circuit board applications such as flip-chips and RFID assembly.

With high-tech glass and plastics also playing an increasingly large part in consumer electronics, adhesives are needed that suit these applications. Nearly every modern cell phone or display device contains a transparent conducting film (TCF) of some kind. Indium Tin Oxides (ITOs) and other TCFs used in LED and OLED displays can be connected with the use of an electrically conductive adhesive to preserve optical transparency where wires or solder wouldn’t be appropriate. ECAs can also be manufactured in the form of a transparent adhesive film that can underlay such TCFs, connecting them to internal electronics.

These delicate components and modern thermoplastics can also be sensitive to high-heat. ECAs are sometimes referred to as “cold solder” because their conductivity offers an alternative to traditional solder connections in applications where the heat involved with soldering is too high. As a solder alternative, ECAs have the advantage of being lead-free when environmental or regulatory concerns are paramount. ECAs also offer options for repairing printed circuit boards (PCBs) where solder is an inconvenient or impossible option.

Finally, ECAs are also efficient heat conductors, and for that reason some ECAs or pastes can be used in heat-dissipation applications. RFID assembly and other flip-chip connections can be achieved with ECAs replacing the traditional solder bumps.

Shielding

ECAs are also used for their ability to provide a conductive surface in applications that need shielding from electromagnetic interference (EMI) or electrostatic discharge (ESD). Now that high-frequency EMI emitting devices are nearly ubiquitous (as are those that can be interfered with) international and FCC EMI compliance standards need to be considered carefully in the design of any product. When an ECA is applied as a coating, or to adhere pieces of electronics shielding, it acts as a Faraday cage, distributing charge around the coated object, rather than through it. This type of shielding can provide protection even at high frequency.

ESD can also be dangerous in environments with sensitive electronics or volatile chemicals. ECA coated or backed flooring can provide a way to safely discharge and prevent the buildup of static electricity and comply with ANSI/ESD S20.20.

Other Considerations

The types of ECA are as diverse as their potential uses. ECAs have been developed for nearly every application and finding the right one depends on the specific situation. While ECAs can serve as a solder replacement in general use – they can also be formulated for other specialty situations. In places where corrosion is a concern, non-corrosive filler material like graphite can be used. For applications where magnetic interference is a problem, ECAs can be mixed with non-magnetic materials. Other specific formulations can be suited for when ECAs are applied as a coating in electrostatic discharge or EMI shielding. Determining exactly what your needs are in terms of both physical connection and electrical connection will allow you to find an ECA that’s tailored to meet your needs precisely.

Shop our range of Electrically Conductive Materials 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.

Ellsworth Adhesives Europe HQ achieve ADS SC21 Award

15 November 2016 by Chelsie Grierson

Ellsworth Adhesives Europe HQ is pleased to announce our achievement of the ADS SC21 Bronze Award.

SC21 is a programme which aims to transform aerospace and defence supply chains. At the heart of SC21 is an industry commitment to focus on delivering a globally competitive UK supply chain within the Aerospace, Defence, Security and Space sector. By collaborating with SC21 we are proud to work together to deliver improvements to the supply chain, thus enhancing our competitiveness within the industry.

This prestigious award was collected by our Continuous Improvement Coordinator, Gary McMillan and our Quality Assurance Coordinator Douglas Burns at the SC21 Taskforce Conference within the Manufacturing Technology Centre, Coventry on 8th November 2016.

As an accredited SC21 company we are committed to achieving high performance in both Business Excellence and Manufacturing Excellence. Coupled with common performance metrics for Quality and Delivery, we are now performing as a leaner and more effective collaborative working organisation.

SC21 companies recognise that sustained success in our industry requires positive relationships in all directions. Using the SC21 relationship code of practice we have identified the level of relationship needed and are objectively focusing upon the areas that need improvement.

In order to achieve this award, we were able to exhibit that our levels for Delivery and Quality excel award standard, combined with meeting the required standards of Business Excellence and Manufacturing Excellence. Currently our On Time Delivery is 97.81% and Quality is 99% for this rolling year. We have surpassed our target of 90-95% (Delivery) and 98.5% (Quality) in both of these areas with incredible scores.

We are aiming to sustain this award and achieve Silver in the upcoming year!

Ellsworth Adhesives Europe Announces Special offers on Metcal Products

7 November 2016 by Chelsie Grierson

Ellsworth Adhesives Europe is pleased to announce a series of special promotions on Metcal’s state-of-the-art MX-5210 Soldering and Rework system. A popular quality product in the Ellsworth portfolio, the MX-5210 dual port simultaneous soldering and rework system has SmartHeat™ technology built in, guaranteeing soldering and rework is always performed at safe, controlled temperatures.

The MX-5210 is a highly efficient system, capable of fulfilling a broad range of soldering applications with increased process control. Typical applications include high mass components or boards, thermally sensitive components requiring low operating temperature, high volume production soldering and touch-up soldering operations.

The offers on the MX-5210 have been designed to benefit different types of consumer including those with a requirement for multiple machines, and for whom a single system is sufficient. The first offer is ‘Buy one MX-5210 system and get a second half price’, a fantastic deal with a huge cost saving for the customer. Offer two entitles the consumer to benefit from a free tweezer upgrade kit (MX_UK4) when purchasing one MX-5210 soldering system. Included in this offer is the MX-PTZ tweezer hand-piece and MX-W4PT work stand valued at £255.20. This tweezer upgrade kit is incredibly advantageous, ensuring SMD rework is simple, whilst allowing maximum application flexibility for most SMD components. In addition, there are 26 different cartridge and temperature combinations.

Due to the popularity of the MX-5210 system it is rare to find not only one but two fantastic promotions on this product. In order to take advantage, consumers should simply quote the respective promotional code when ordering in order to quality. To benefit from Offer 1 (Buy one MX-5210 system and get a second half price) quote ‘MX16Q4’ to validate the price. If the free tweezer upgrade kit is the more enticing offer, the perspective buyer must quote ‘P5-MXUK4’ when ordering. It is important to note that tweezer cartridges are sold separately.

These promotions are limited to orders placed on or before December 31st 2016, and cannot be used in conjunction with one another.

Ellsworth Adhesives Europe is an official distributor of Metcal Soldering Systems and Equipment. To enquire about this system or any other products within the Ellsworth range please contact: infoeurope@ellsworth.com.

The Key Benefits of Dielectric Gels for Encapsulation

1 November 2016 by Chelsie Grierson

Dielectric gels are a specialist type of encapsulant with the unique capacity to remain as a soft and flexible material post curing. Available as one or two part materials, this product group meets the needs of most applications and process situations and can be considered for use on actuators. As a solvent-less material, dielectric gels are typically low-viscosity liquids. Although available as one or two-part gels, two-part products are the most commonly designed and are distributed with a 1:1 mix ratio in the form of parts A and B, allowing for either a room temperature or a heat accelerated cure. Those that are formulated as one-parts, create ease and convenience for the user as the need for mixing is eliminated, however they do require a heat cure. Advancements have found that a few specialised one-part gels now allow for a very rapid UV cure. In this latest blog post we will look more closely at dielectric gels, examining the features and benefits of this product group, and highlighting the most popular dielectric gel products from Dow Corning, leading manufacturer of dielectric gels.

Features & Benefits

One of the most unique and indeed impressive characteristics of dielectric gels is the product’s ability to re-heal if it becomes broken or cut. As such, dielectric gels are an incredibly resilient material and provide cushioning whilst also offering the dimensional stability of an elastomer. The reason behind dielectric gels ability to re-heal is their natural tacky surface, which forms post cure. This surface will adhere to most common substrates without the assistance of a primer. Key features of dielectric gels include: temperature resistance, low modulus – good dampening properties, low viscosity, tacky adhesion at room temperature and high dielectric strength (>18kV/mm). This is guaranteed to create reliability as well as a number of key typical benefits including: under the hood usage, thermal and mechanical stress protection and an easy flow around components which will prevent formation of thermally induced voids. Dielectric gels have excellent stress relief properties, similar to those of a liquid. For this reason, this specialist material is commonly used on electronic circuits to isolate the circuit from the harmful effects of contaminants. Dielectric gels not only provide electrical insulation for high voltages, they also provide the electronic circuit stress relief and protection from thermal and mechanical stresses.

Applications

There are a number of applications where the choice of a dielectric gel would be advantageous. This could be in the form of a material application from conventional insulators to applications where dielectric properties are controlled for active device architectures. In addition, these can include: sensor potting, ECU potting, power module potting, rectifiers, semiconductors, transducers, capacitors, transformers and for the use with cable joints.

Closing Thoughts

Dielectric gels are a truly resilient material type that can cater to a great number of complex applications. Due to their remarkably low modulus, Dow Corning branded silicone gels are much softer compared to other similar products and, as a result offer impressive stress relief as well as dielectric insulation.

Ellsworth Adhesives Europe has a number of dielectric gels available from Dow Corning, designed for excellent performance at a low cost. Product highlights from the Dow Corning range include 3-4150 dielectric gel kit, a two-part, transparent green with a fast heat cure, as well as Sylgard 537, a one-part, clear, heat cure, low viscosity gel. If your application requires a gel with added strength, look no further than the 3-4241 with enhanced chemical adhesion.

Shop our range of Dielectric Gels.

To make an enquiry about any of our Dow Corning Dielectric gels, contact Ellsworth Adhesives Europe via email: infoeurope@ellsworth.com or alternatively call 01355 321122.

You can learn more about other encapsulant materials in our archived blog post.

Ellsworth Adhesives Europe launch new Spanish language website

18 October 2016 by Chelsie Grierson

Ellsworth Adhesives Europe is pleased to announce the launch of its new Spanish language website. As a leading distributor of industrial adhesives and adhesive applicators, the Ellsworth Adhesives Iberica product portfolio is vast and the newly updated website aims to reflect this.

As such, the new Spanish website incorporates the core of the original Ellsworth Iberica site whilst aiming to encapsulate a more modern design in line with its parent site, Ellsworth Adhesives Europe.

Users will experience the same features and attributes as on the parent site, with key information and pages translated into the Spanish language for the reader’s ease. Moreover, the new Spanish website is now accessible for all – thanks to its mobile friendly design. Users can now access the website whenever and wherever they desire. Overall Ellsworth Iberica hopes to offer a better optimised, more user friendly and positive experience for visitors to its new website.

Managing Director of Ellsworth Adhesives Europe, John Henderson comments ‘By relaunching and updating the Ellsworth Adhesives Iberica website we aim to improve the user experience for our Spanish customers. We wanted a site which allows users to navigate with ease in their native language whilst adopting the theme of the Ellsworth Adhesives Europe website’.

The new look Ellsworth Iberica website tailors content to suit Spanish consumers. For example, users can learn more about the Spanish branches and upcoming appearance at Matelec 2016 – Spain’s largest electronics trade event, taking place between October 25th and 28th.

The relaunched Ellsworth Adhesives Iberica website is now live and can be accessed by visiting: www.ellsworthadhesives.co.uk/home-spanish

The Essential Guide to Potting and Encapsulation

3 October 2016 by Chelsie Grierson

Introduction to Potting

Potting is, very simply, the process of covering a component with a resin to guard against potential environmental threats. The most common use for potting is to protect against water and moisture, or to insulate electrically. However, potting can also protect PCBS and other components from thermal and physical shock, chemical attack and tampering, as well as be a physical and visual shield to protect intellectual property and consumer information.

The terms “potting” and “encapsulation” are often used interchangeably, but technically, potting refers to a process where the shell or “pot” that is filled with resin becomes a part of the finished component. In encapsulation, the component and hardened resin are then removed from the pot to be placed in an assembly. Conformal coating is a similar process that can protect against some of the same environmental threats, but generally provides less thorough protection. The two processes can be used in conjunction, and each has its own specific applications.

Major types of potting compounds

There are three major types of potting compounds – epoxies, urethanes and silicones. Each has its strengths and drawbacks, and is suitable to particular uses.

Epoxies – Epoxies offer excellent chemical resistance, and temperature resistance up to 200C. They provide excellent strength to components and electrical insulation, making them ideal for use in high-voltage applications. They can become brittle in low temperatures, and the heat of reaction and shrinkage during curing can be a problem for sensitive components. There are some low-stress potting materials on the market designed for potting SMT populated boards where this is a key factor.

Urethanes – Urethanes are more flexible than epoxies, putting less strain on potted components in general. They offer better performance in applications with thermal cycling and in low-temperature environments (down to -40C). However, these potting compounds are generally less resistant to chemicals and high temperatures (above 130C).

Silicones – Silicones offer excellent flexibility and operate over the widest temperature range. They are also resistant to many chemicals, liquid water, UV light and ozone. However, they are often the most expensive option, and may not be suited to applications where high rigidity is needed. They also have relatively high CTE, which can sometimes cause problems in applications with high thermal cycling.

Other types of potting compounds

There are other types of potting compounds that may be applicable in specific situations. These compounds are often described by their end-use or cure method and can be formulated using epoxy, urethane or silicone bases.

UV curing compounds can be a good option, particularly when concerns over curing time are paramount. UV curing allows compounds to cure in seconds, but can run into difficulty with especially thick potting or encapsulation. A secondary heat or moisture cure can be used to finish components in those situations.

Thermally conductive potting compounds are compounds that have a heat-conductive filler added. These compounds can be used when heat-producing components would be too insulated by a regular potting compound. While they provide some thermal dissipation, heat sinks are sometimes needed and can be potted as well.

Optical encapsulants are potting compounds that are optically clear – allowing for either visual inspection of the components beneath them or for light to shine through them. These compounds are often used in the manufacture of LED lights and displays, as well as the solar panel industry because of they are UV stable and flame retardant.

Optical encapsulants tend to be used in the manufacture of LED lights.Optical encapsulants are often used in LED lights due to being UV stable and flame retardant.

Hot melt thermoplastic polyamide polymers can be used for potting as well. These are made from a thermoplastic that is heated and molded around components. This can be an excellent option for creating a watertight enclosure that sets quickly, and are available in UV-rated formulations.

Choosing a potting compound

Ceramic potting compounds can also be used for specialty purposes. These compounds provide excellent dielectric insulation, and work well in even in the 2000C range. They are mainly used in specialty electrical potting applications.

Many factors will go into the decision about what potting compound is ideal for an application. What elements should be protected from needs to be analyzed, with water, chemicals, and electrical insulation being the most common considerations. Further, the operating temperatures of the components and mechanical stresses need to be considered, as potting compounds undergo many property changes (most noticeably modulus and CTE) when crossing the glass transition temperature (Tg). Finally, production and cure times need to be taken into account. Opacity, color or translucence may also be important to think about in particular situations. All of these factors can be altered to meet specific needs.

In cases where assemblies need to be fire-resistant, there are a number of potting compounds that are UL listed for flame retardance Standard 94. Potting can also help enclosures meet IEC standard 60529 – known as International (or Ingress) Protection Marking. This IP standard assigns ratings to critical equipment (like AEDs) that describes the level of protection afforded against ingress by dust and water.

As the potting compound and the components potted will have different coefficients of thermal expansion (CTE), components may be subject to additional stress if the assembly undergoes thermal cycling. Therefore, it will be important to consider the lifecycle of the components and choose a compound that is flexible enough for the specific application.

Avoiding damage during potting

There are two main dangers to components when potting. The first is that heat from the curing reaction will cause damage to delicate components. If the components being potted are sensitive to heat, it will be important to choose a compound that either gives off a low amount of heat during curing or that dissipates heat more easily, like a thermally conductive potting compound. The second danger is that shrinkage of the potting compound during curing may damage sensitive components or solder bonds. This can be avoided by choosing a potting compound that shrinks less or is more flexible.