This Month in Design007 Magazine: Thermal Management—Keeping Cool Starts From Within

Jade Bridges_Electrolube_Oct2018.jpgIntroduction

Thermal management is a critical component of the design phase for any electronics device. Factoring in thermal management earlier on in the design process will lead to a more reliable and cost-effective end product. This month, Jade Bridges takes a fresh look at popular subjects within the field of thermal management. For instance, how do you know for sure if your thermal management process has been a success? Jade also explores what occurs when devices overheat, as well as the benefits of thermal gap fillers and how to best avoid pump-out. Thermal management plays a significant role in protecting electronic circuitry, so let’s explore some of these key areas in more detail and discuss practices that ensure better thermal management.

1. How do I know if my thermal management is a success?

There’s so much to consider when selecting a thermal management material, and getting it wrong could ultimately compromise the reliability of an electronic assembly and shorten its life expectancy. No pressure! When you think you have it right, how can you be entirely sure that your thermal management process has succeeded? Critically, the product would have been tested under real-world conditions to see how it holds up under the heat, allowing engineers to alter the design before it goes to market and giving designers the opportunity to make any necessary changes to preserve the product’s functional integrity and operational reliability.

Evaluating thermal performance in all phases of the design cycle will also confirm any issues being brought to light early on and help to prevent a costly system-level teardown. The criteria for evaluating the success of your thermal management process is actually fairly simple and involves three factors to consider. If you can say “check, check, and check” to the following, then you can reassuringly consider your thermal management process as a success:

  1. Improved efficiency of heat transfer.
  2. Reduced thermal resistance.
  3. Observe a lower temperature around the heat-generating component/device.

2. What is the worst that can happen if a device overheats?

Increasing miniaturization in electronics means that heat dissipation problems are becoming increasingly important. More effective thermal management will often lead to enhanced reliability and life expectancy of devices. Insufficient thermal management will quite simply lead to overheating, which may be caused by different factors at play as to why an electronic component becomes subjected to excessive levels of heat. For instance, consumer electronic devices, such as portable laptops and smartphones, are becoming more prone to overheating. This is because the physical dimensions of these devices are becoming smaller and more compact. To be specific, as the demand for smaller devices increases and becomes even more challenging, manufacturers of electronic components need to pack far more into even smaller areas.

With overheating, failure of the component is typical. If we consider a heat-producing electronic component in isolation, then during operation, its temperature will rise until the heat produced within the device becomes equal to the heat lost to the surroundings, and the device has reached equilibrium. The rate of loss of heat from a hot object is governed approximately by Newton’s law of cooling, which states that the rate of loss of heat is proportional to the temperature difference between the body and the surroundings.

As the temperature of the component rises, the heat loss increases. When the heat loss per second equates to the heat produced per second within the component, the device will have achieved its equilibrium temperature. This temperature may be high enough to significantly shorten the life of the component or even cause the device to fail.

Here, the worst outcome is if an entire device overheats. This will consequently affect neighboring materials, and it must be considered how these materials will react if the temperatures reach the maximum possible level. Thermal management products are the ideal solution for this scenario. A similar approach can be applied to a complete circuit or device which incorporates heat producing individual components.

3. What exactly is a gap filler?

A gap filler is a material that is designed to be used at higher thicknesses than a standard thermal interface material. It could be used on a gap of 300 µm up to a few mm. A gap filler will provide a good thermal conductivity but also maintain its stability at these higher thicknesses, ensuring good heat transfer throughout the life of the product.

Thermal gap fillers are widely used for mobile and touch screen applications; however, some products are extremely adaptable and can be used in a multitude of applications from PCB assembly and housing electronic components discretely to automotive electronics, including HEV and NEV batteries, power electronics, LEDs, and fiberoptic telecoms equipment. Gap fillers are typically soft and compliant for low-stress applications and are easy to dispense due to their low viscosity. They also offer high thermal conductivity, and their low modulus elastomer prevents pump-out, which conveniently leads to my next point.

To read this entire column, which appeared in the June 2020 issue of Design007 Magazine, click here.

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2020

This Month in Design007 Magazine: Thermal Management—Keeping Cool Starts From Within

06-09-2020

Thermal management plays a significant role in protecting electronic circuitry. Jade Bridges takes a fresh look at popular subjects within the field of thermal management and explores what occurs when devices overheat, as well as the benefits of thermal gap fillers and how to best avoid pump-out.

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Sensible Design: Thermal Management—Five Tips for Application Success

05-25-2020

With so much to consider when choosing a thermal management material, it’s important to do your calculations, consider the equipment’s operational, and environmental conditions and experiments. Underestimating these could compromise the reliability of an electronic assembly and shorten its life expectancy. Jade Bridges shares five tips to improve your thermal management process.

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Sensible Designs: Resins—Five Tips for Potting and Performance

05-05-2020

Readers continue to ask, “Does thicker coverage achieve better performance? What is the best advice for manual potting? We chose an inappropriate resin, so how will this affect our application?” In this column, Alistair Little explores these and other issues based upon frequently asked questions from Electrolube’s customers.

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2019

Sensible Design: Top Tips for Conformal Coating Selection

12-31-2019

Over the past few months, I have covered the topic of conformal coatings in as much depth as possible. In this column, I’m going to explore some of the essential factors for designers in coating selection. As we have all experienced, sometimes, things are not always as simple or straightforward as we would like them to be, and in any engineering discipline, there is always the slightest chance that something might go wrong. Thankfully, the key to kicking that possibility is to be as fully prepared as possible. Thus, I’m going to concentrate on helping you avoid coating pitfalls in my five-point guide.

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Conformal Coatings: How to Design Out Production Problems

08-29-2019

In my last few columns, I’ve covered quite a bit of ground regarding the important considerations for conformal coating selection and performance, and the suitability of conformal coatings for LEDs and protecting circuitry from the harshest environments. I hope these columns have provided plenty of food for thought as well as given you a basic understanding of coatings and their benefits and limitations. In this column, I’m going to look at the different angles that design engineers and purchasing professionals come from and explore how these can sometimes conflict when selecting conformal coatings.

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Sensible Design: Resins Fit for a Purpose—Failure Mitigation and Environmental Concerns

07-18-2019

So far, in my columns on resin chemistries and encapsulation/potting techniques, I have tended to concentrate on the properties of these materials. My insights have included how they are best applied in the factory, and the steps that must be taken to get the best performance from them once they are in the field to protect an electronic assembly or lighting fixture against the elements. In this column, I am going to address the question of resin failures—in particular, how to avoid them—and to get a better idea of where and how appropriately selected and applied modern resins are making a big difference in the world of extreme electronics installation and implementation.

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Thermal Management: Why It Should Be High on Your Circuit Protection Agenda

06-06-2019

In my previous column, Jade Bridges highlighted a few cautionary notes on the pain points associated with thermal management products, particularly the choices that you will be confronted with, such as which material or product type (i.e., pad or paste) is best suited to your application. In this column, she will underline the importance of getting it right, and touch on the consequences if you don’t.

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Sensible Design: Five Tips to Further Improve Resin Encapsulant Performance

05-16-2019

There are a number of different factors that influence the protection afforded by potting compounds. The act of encapsulating a component or PCB means that it is surrounded by a layer of resin, which completely seals a component or an entire PCB from the environment in which it operates. When mixed, a two-part resin starts a chemical reaction, which results in the resin becoming fully polymerised to provide a homogenous layer.

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Sensible Design: Important Considerations for Conformal Coating Selection and Performance

04-25-2019

Having covered the subject of conformal coatings in depth over the past few months, now is an appropriate time to review some of the key pointers I have tried to share in my various columns. I present some of my thoughts on the essentials in this five-point guide.

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Sensible Design: Thermal Management Materials—Golden Rules for Product Selection

03-28-2019

Selecting the right type of thermal management method that will suit a particular electronic assembly and its predicted operating conditions is far from easy. There are a number of stages in the selection process that you should consider taking before you decide upon a particular material or material format, whether paste or pad. In this column on achieving effective thermal management of electronic assemblies, I will revisit our trusted question-and-answer format to bring you some essential pointers, beginning with a few cautionary notes on pain points—the occasional pangs of agony you will have to face during the decision-making process.

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Sensible Design: Getting the Best Performance from Encapsulation Resins

03-07-2019

When I last broached the subject of potting and encapsulation resins, I went into some depth on the subject, explaining their chemistries and physical properties, how they behave when being mixed, applied and cured. For this column, I’m going to return to our tried-and-trusted Q&A format to offer four commonly asked questions about resins and their application, together with my responses, which I hope will help you achieve the best outcomes for all your potting and encapsulation jobs. So, setting material choice aside for the moment, let’s start with a key aspect of potting: getting the resin in place.

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Top Five Tips to Protect PCBs from Harsh Environments

01-02-2019

First, think very carefully about the sort of environment your PCB is likely to encounter. It is easy to over-engineer a product so that it will survive the very worst of conditions, but worst conditions may only be fleeting or transient. Therefore, a resin solution with a lower temperature performance specification will often cope. Take temperature extremes as an example; your application may experience occasional temperature spikes of up to 180°C, which you might feel deserves treatment with a special resin. However, such excursions may only be short-lived.

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2018

Sensible Design: Top Tips for Successful Potting

12-19-2018

For effective potting, ideally, the layout of the circuit components should be such that the material can flow smoothly around them without too much turbulence. When possible, it is always good practice to space components in a regular pattern. Irregular spacing—particularly bunching of components in discrete areas of the PCB—causes the formation of eddies in the resin as it is poured, which can lead to voids and air entrapment, which compromise the thermal performance of the resin.

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Do's and Don'ts of Thermal Management Materials

10-18-2018

Selecting a thermal management material that is broadly applicable to a particular electronic assembly and its predicted operating conditions is a good starting point; however, as with many of these things, the devil is very much in the details! Find out the key considerations in choosing your materials.

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Conformal Coatings: An Evolving Science

09-26-2018

One of the trends impacting the electronics assembly industry is the continuing miniaturization of electronics products. This article sheds more light on coating problems posed by this trend, as well as provide key considerations when it comes to coating properties, selections, and applications. Read on to find answers to five of the best coating-related questions that frequently arise during preliminary consultations.

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Thermal Management Materials: Easing the Decision-Making Process

08-02-2018

There are many different types of thermally conductive materials, and choosing between them will be dictated by production requirements and application design, as well as critical performance factors that must be achieved.

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Protecting PCBs from Harsh, Challenging Environments

07-03-2018

Think very carefully about the sort of environment your PCB is likely to encounter. It is easy to over-engineer a product so that it will survive the very worst of conditions, but worst conditions may only be fleeting or transient. Therefore, a resin solution with a lower temperature performance specification will often cope. Take temperature extremes, for example. Your application may experience occasional temperature spikes of up to 180°C, which you might feel deserves treatment with a special resin.

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My Top Coating Queries

04-04-2018

This is my first of many columns for 2018, and I have decided to share some top trending queries that concern many different applications and areas. LEDs are always a hot topic, as are volatile organic compounds (VOCs) and harsh environment concerns.

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2017

Heat Transfer and Thermal Conductivity: The Facts

12-26-2017

In my first two columns, I presented a broad introduction to the subject of thermal management of electronic circuits. This month I’m taking a closer look at thermal interface materials—how they can be applied to achieve efficient heat transfer, and the significance of bulk thermal conductivity in relation to heat transfer and thermal resistance.

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Thermal Management—The Heat is On

09-25-2017

Thermal management materials are designed to prolong equipment life and reduce incidences of failure. They also maintain equipment performance parameters and reduce energy consumption by reducing operating temperatures, and minimising the risk of damage to surrounding components. Indirectly, they maintain brand reputation, as the reliability of the equipment will be very dependent upon the effectiveness of the thermal management technique used.

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Resins: Cutting Through the Technical Jargon

08-21-2017

This month, I’m going to cut through some of the more heavy-going tech-speak, taking a few of my customers’ more frequently asked questions about resins to try to help you refine your selection process. There’s a lot of ground to cover, but for the purposes of this column, let’s concentrate on the PCB’s operating environment, caring for the components that are to be encapsulated, and the special needs of applications like LED lighting and RF systems.

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Casting a Spotlight on Resin Applications

05-03-2017

Over the last few columns, I’ve given readers pointers on virtually every aspect of potting and encapsulation resins, ranging from their formulations and special properties to their applications, benefits and limitations. It’s probably high time, therefore, to take a step back from the do's and don’ts and focus instead on how these resins are bringing very real benefits to practical electronic and electrical engineering applications. A good starting point is to look at the special requirements of an industry that is enjoying explosive growth: LED lighting.

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2016

Resins: Five Essentials to Achieve the Right Cure

12-19-2016

In my previous column, I looked at some of the critical things you need to consider before selecting your resin. Of course, when it comes to the choice and application of resins, there’s a lot of information to take in, and over the following months I hope to distill this and provide some useful tips and design advice that will help you in your quest for reliable circuit protection.

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Why are Resin Properties So Important?

11-21-2016

I started this series of columns on resins by going back to basics, questioning the core rationale for potting and encapsulation with resins, their fundamental chemistries and how each resin type differs one from the other—indeed, how their individual properties can be exploited to maximise performance under a wide range of environmental conditions. I hope readers found this useful. Of course, when it comes to the choice and applications of resins, there’s a great deal more to discuss.

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The Little Guide to Resins

10-17-2016

I would like to start this series of columns by going back to basics, questioning the core rationale for potting and encapsulation with resins, their fundamental chemistries and how each resin type differs one from the other—indeed, how their individual properties can be exploited to maximise performance under a wide range of environmental conditions.

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Conformal Coatings - Beware the Boards that ‘Bare’ All!

09-21-2016

This month, Phil Kinner departs from his usual format of providing five essential facts about conformal coatings. Instead, he provides an account of a customer’s problem—no company names mentioned, of course—that brought into question the adhesion performance of a coating that they had been using successfully for some time.

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When Coatings Go Wrong

08-23-2016

This month, I consider some of the more common, and often very frustrating, problems that may be encountered when coating electronic circuit boards and components. I also discuss some practical solutions. As we all know, nothing in life is straightforward.

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Coatings—Five Essentials for Designers

06-28-2016

In an ideal world, PCB designs would not have an inherent weak point for corrosion; unfortunately, in the real world, they do. When a weak point is revealed, you are better equipped to deal with it. Often the spacing of components, board finish and distance to ground planes can be optimised for corrosion resistance.

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