Thermal management solutions are crucial to making electronic devices trouble-free, as they help to regulate the core temperature in the right manner. Electronics Bazaar finds out the latest in thermal management offerings
By Samonway Duttagupta
The world of electronics never fails to amaze one. It is beautiful, but complex. And to make complex machines operate efficiently, their components need to function properly. So to ensure everything works perfectly, controlling or properly channelising the heat generated is of utmost importance. This is where thermal management solutions come in. These include a host of materials, ranging from adhesives to gap fillers, depending on the application areas and requirements that are integrated with electronic devices. They manage the heat generated in the right manner and ensure proper functioning of the device.
Thermal management holds the key
Thermal management solutions are an integral part of any product that is manufactured in the electronics industry. A finished electronic product, which will be used to its maximum potential on a regular basis, requires a thermal management solution. Too much heat being generated inside an electronic device while in use can degrade it, and can even cause deterioration and malfunctioning in the course of time. R.S. Madhava Murthy, technical manager and Joy Thomas, manager – marketing from Electronics Materials Solutions Division, 3M Electro & Communication India Pvt Ltd, explain this concept beautifully: “The materials that are used in the heat path play a major role in conducting the heat away from the source. Such materials must be reliable to perform well at varied operating conditions. As electronic devices are designed to work for many years, the thermal management materials also must function as intended for that life span.” In short, the longevity of thermal management solutions should considerably exceed that of the electronic devices in which they are being used.
In order to match the demanding needs of the electronics industry, devices are going through constant technological advancements, resulting in the enhanced functionality of these products. Hence, they require immense amounts of power to run. But more power leads to more heat being generated inside these devices, which can only be controlled with the help of an efficient thermal management system. Sandeep Joshi, marketing manager – automotive and electronics, Dow Corning, explains, “Electronic devices are facing thermal management challenges as the smaller electronic modules are more densely packed with components, raising under-the-hood temperatures. Considering that device longevity and performance are key objectives today, effective heat dissipation is getting increasingly important.”
Innumerable benefits
As mentioned earlier, thermal management solutions are required across all electronic device manufacturing processes. Based on Electronics Bazaar’s industry interactions, we have identified a few areas where thermal management solutions are required to a greater extent—LED lighting and LED displays, semiconductors, mobile handheld devices and automotive electronics.
Let’s now look at why these products require effective thermal management systems.
Semiconductors: These are often used in transistors, which are solid-state switches that are controlled by electric current. When power is applied to the transistor, the semiconductor allows it to flow through the junction. The flow of power causes a rise in temperature at the junction. Naturally, this affects the semiconductor as the life expectancy and performance of a semiconductor is directly linked to the junction’s temperature. Studies have revealed that generally, for every 10° C above 100° C, the operational life of the semiconductor is halved. Hence, it becomes essential for a thermal management solution to be in place to regulate the heat.
LED lighting: This industry is going through a revolutionary phase, where new and innovative products are being launched on a regular basis. It is also an industry that just can’t do without thermal management solutions. As Vijay Kumar Gupta, CEO, Kwality Photonics Pvt Ltd, puts it, “One thing that is of prime importance in LED lighting manufacturing is thermal management.” This is because energy saving LED lights use chip-on-board (COB) components, which need efficient regulation of heat. In the case of not-so-efficient thermal management in LEDs, the lights might suffer from a tendency to blacken and face early damage.
Mobile handheld devices: Rapid technological advancements in mobile handheld devices have resulted in their increased functionality, even as their form factors have shrunk. Cell phones, for instance, are usually housed in sealed cases with space being a premium. It’s highly recommended that the air gaps within the enclosure are kept to a minimum. A considerable amount of the heat generated in integrated circuit (IC) packages is first conducted onto the printed circuit boards (PCBs), and then transferred to the interior walls of the housing by way of conduction, convection through air and radiation, depending on the specifics of the enclosure. The heat must then be conducted through the case walls, and finally released into the atmosphere. The ongoing demand for smaller devices has led to smaller enclosures, higher digital clock speeds,a greater number of power emitting devices and shorter design cycle times. And to make these powerful packages run efficiently, thermal management needs to be given priority early in the design cycle.
Automotive electronics: This sector has gone through a complete revolution in the last few decades with the changing needs of consumers. Mirroring the miniaturisation in handheld devices, the downsizing of engines to improve fuel efficiency generates tremendous amounts of heat. Traditional thermoplastics do not have the capacity to withstand this heat. This is true even for high pressure and chemical exposure. Hence, there is a need for constant improvements in the thermal management solutions for automotive electronics.
Multiple options
Effective thermal management varies from case to case, depending upon the materials used and power usage in different electronic devices. Hence, there are plenty of options available.
Thermal interface materials (TIMs): TIMs are known to enhance electronics performance by dissipating heat when placed between solid surfaces. Joshi provides an insight: “When inserted between solid surfaces, TIMs connect the parts – mainly heat sinks and circuit boards – in devices and modules. They also dissipate heat from electronic components, ensuring their reliable, long-term performance. As device makers seek more robust, stable materials to withstand higher temperatures, material suppliers are developing a variety of higher performing TIMs.”
The performance of TIMs depends heavily on three major factors — bulk resistance, contact resistance at the interfaces and bond line thickness (BLT). Material developers are usually known to prefer high bulk thermal connectivity, low achievable BLT (<100 microns), high electrical insulation, low interfacial resistance and long term stability. Joshi adds, “Also important is ensuring the right application technique and the close contact with the substrates, which eliminates air gaps and maximises heat transfer. The right TIM can help achieve the best balance of thermal performance, physical characteristics, processing ease and costs.” Silicones provide added advantages like high- and low-temperature stability, low ionic content and high purity. Besides, they have low surface energy, and are preferred because of their excellent surface contact and void-free substrate interfaces.
A well-known manufacturer of silicone TIMs, Dow Corning offers adhesives, compounds, elastomers and gels. Thermally conductive silicone adhesives are best suited for bonding and sealing hybrid circuit substrates, semiconductor components, heat spreaders and all other applications that demand broad designs, flexible processing options and highly efficient thermal management. Thermally conductive compounds are known to draw heat from a device’s sensitive electronics and dissipate it into the ambient environment. Thermally conductive silicone elastomers and gels have low viscosity before being cured, which enables manufacturers to fully embed tall components and delicate wires, and solder joints in them. So they are the first choice for managing high levels of heat in complicated electronic architectures.
Thermal pads: This form of thermal management enables quick and precise distribution or printing of a layer of a thermally conductive silicone compound in controllable thicknesses on complex substrate shapes, which helps in ensuring excellent thermal management and a lower cost compared to prefabricated thermal pads.
Thermally conductive adhesive transfer tapes: Used largely by the electronics industry, these tapes are made of acrylic adhesives. 3M is a well-known expert in this. There are different types of such tapes on offer that do not have carriers in them. Carrier-less construction provides better shock absorption abilities, adhesion and thermal cycle performance and a comparatively longer life. Tapes are available in varied thicknesses starting from 0.05mm onwards.
Nanotechnology based thermally conductive non-silicone grease: An innovation from 3M, this grease can be dispensed by way of screen printing and offers high bulk conductivity with very low thermal impedance. In fact, a non-silicone formulation is capable of eliminating the risk of silicone contamination.
In tune with changing demands
The companies providing thermal management solutions have to stay abreast of the latest technological advancements happening in the field of electronics and keep improving their products according to the growing demands of the market. Dow Corning, for instance, has made significant improvements in its thermal adhesives for LED lighting, a booming industry in a constant state of new developments. Dow Corning’s latest launch is the SE 4485 thermal adhesive, which is a one-part, tack-free, flowable, moisture cure adhesive. This adhesive has good thermal stability and a low-temperature resistance. Joshi explains what makes this product special when compared to its key competitors in the market. He says, “The flexibility, stability and strength of the silicon-oxygen bond distinguish silicones from organic polymers. Unlike most organic materials, cured silicones retain their physical properties up to an operating temperature of 200°C. This makes them ideal for under-the-hood electronics. Silicone TIMs are also flexible enough to handle the coefficient of thermal expansion (CTE) differences without transferring stress to components or substrates.”
Silicone rubber pads are also undergoing technological advancements these days. This is because they are used for heat management in electronic devices and joining/stacking parts in electronic components (both are in high demand these days). 3M Electronics’ materials solutions division has recently launched the 3M 5515S ultra-thin silicone rubber pad which ensures easy handling of die-cut parts. What really sets this pad apart is its thickness of 0.2mm or 0.25mm; yet it offers thermal conductivity of 2.7W/mK. Murthy and Thomas of 3M Electronics’ materials solutions division claims, “This product can reduce total cost of ownership. With the company’s decades of experience in developing various materials, it understands the aging and weathering of materials because it has real field data from over 100 years of operations.”
When it comes to automotive electronics, thermal management solutions providers are running against time to offer products that gel with the highly demanding technological advancements. DuPont, being a leading provider, has recently launched the Crastin Polybutylene Terephthalate (PBT) resin, which is known to have a considerable amount of stability against moisture and has good heat resistance abilities. It is well-suited for lighting bezels, connectors, relays, switches, distribution boxes and fibre optic cable jackets. What makes it stand out is its superior flow qualities, ease of processing on conventional injection moulding machines, and a wide range of grades designed specifically for low warpage, hydrolysis resistance and also for blow-moulding and extrusion.
Choosing the one that works best
Deciding upon the right thermal management solutions for one’s business is a tough call. After all, it is not just about choosing one from a plethora of options, but requires analysis of which option best suits the company’s products and the possible technological advancements in the future. This is the reason why thermal management is something that should be considered right at the beginning, when a product is being conceptualised and designed. This makes the selection process easier and, at the same time, a provider of thermal management solutions can also suggest the best options available. Murthy and Thomas of 3M Electronics provide an expert view on this: “Good thermal engineering is the starting point. The designer must do detailed calculations of heat management and set a target for thermal resistance or the impedance of the interface material needed for the application. Based on this input and other parameters like ease of manufacturing, cost and ease of servicing, among others, we can shortlist a few products to conduct experiments. Final selection of thermal interface materials is done after installing them on devices and taking measurements to verify if the simulated thermal design concurs with what actually occurs.”
The way forward
Thermal management plays an important role in determining a device’s functionality and can prove to be as important as the device itself. The process starts before the product is designed and resides at the core of its system. This is a wonderful time for companies manufacturing and dealing in thermal management solutions. The primary focus must be on the quality of the material so that it dissipates maximum heat, remains future-ready and can be the most cost-efficient solution in any production process.
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Views that matter
Nobody can provide insights and suggest systematic improvements better than users of a product. In an attempt to dig a little deeper into the state of thermal management solutions provided these days, Electronics Bazaar interacted with a few buyers to let readers hear the other side of the story.
Deki Electronics Ltd, which is a leading manufacturer of capacitors in India, gave us an interesting insight. The company identified a very niche application area, which actually indicates business opportunities for budding companies in the field of thermal management solutions. Anil Bali, vice president, Deki Electronics Ltd, puts it in a nutshell: “In our process, we do hot pressing of the round capacitors to make them flat. For this, we require very accurate temperature control. For that we use proportional-integral-derivative (PID) temperature controllers. These help us to maintain accuracy. We also do pre- and post-curing of our capacitors after undercoating and top coating with liquid epoxy or powder epoxy. The temperature also needs to be maintained within specifications, at this stage. This is also achieved by PID controllers.” When asked about his expectations from thermal management solution providers, Bali said that the key things are better accuracies, faster corrections and getting printouts with temperature readings.
Vijay Kumar Gupta of Kwality Photonics Pvt Ltd gave us his inputs with respect to thermal management in the LED lighting industry: “Our thermal management starts at the chip and die level. The bonding of the die is mostly done by conductive epoxy, which provides both electrical and thermal conductivity. And for higher power chips, we use silicon sub-mounts for thermal management.” Suggesting how thermal management can get better in the future, Gupta says, “The thermal conductive particles that are used should be better, because that is what decides the quality of thermal management and how long it can last without getting dried up.” LED lighting being a key industry in India, with the government promoting it actively even for lighting up households, thermal management solution providers should focus on technological advancements in this field as much as possible. This will certainly open new avenues for their businesses in the coming days.
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A checklist prior to making a purchase decision
√ Look for features that fit your needs best
√ Experiment before you purchase
√Ascertain the life of the product
√ Right temperature controllable
√ Check if the solution will ease manufacturing
√ Look for accuracy
√Check the cost-effectiveness
√ Ensure ease of servicing
