A Texan’s Guide to Thermal Management for Touch Screen Displays
By Shaun Detmer, Director of Marketing
This year I lost count of how many days it was over 100 degrees here in Austin, Texas. If my dog could talk, he’d tell you it was entirely too many. While you and I (and the dog) can cool off with a cold beverage or hide out in the air conditioning, some missions can’t wait. Touch International is often tasked with providing touch display solutions in places hotter than a Texas summer. During my time here, I’ve had the benefit of learning from industry veterans while developing touch display solutions for applications in some of the most challenging environments that exist. Grab a tall glass of sweet iced tea, and check out the methods and materials available to manufacture touch screen displays that can navigate a desert combat zone without compromising optical performance.
It’s the art of putting the right combination of these options together to overcome challenges facing our customers that gets us out of bed in the morning.
We can combine any, or all of these options to beat the heat, regardless of your application.
It’s almost too obvious to list, but it can’t be left out. There’s a myriad of cooling fan options for both consumer and industrial applications. Costs vary greatly, mostly depending on the materials used. Higher end cooling fans can be aluminum or copper with optimized heat pipes, integrated heat sinks, and high-quality ball bearing assemblies. On the lower end of the cost spectrum, you can find plastic fans of any shape and size imaginable just to get some air moving through your assembly.
When designing a complete touch display that will require a fan, you must consider the additional power required, mounting options, and the additional space required before you finalize your housing design.
Heat sinks, or heat exchangers, transfer heat generated by an electronic or mechanical device into the atmosphere (or liquid cooling system) by maximizing the surface area. The fluid transfers the heat away from the device, allowing it to cool to the desired temperature. Metals with high thermal conductivity are used. Aluminum alloys are the most common heat sink material. Aluminum costs less, weighs less, and gets the job done for most applications. For environments where higher levels of thermal conductivity are a requirement for operation, copper provides the best heat dissipation. Some heatsinks use a combination of aluminum fins with a copper base to save on cost and weight where they can.
Much like the cooling fan market, there are endless options available. Heat sinks can be combined with other thermal management materials such as heat exchange gaskets and cooling fans.
Housing Material and Design
Typical touch display housing materials are steel and/or aluminum. Steel costs less and is more durable than aluminum, making it an attractive option for most industrial applications. Aluminum costs more than steel but is lighter weight, and a good conductor of heat, allowing for better dissipation in high heat applications where you might incorporate a heatsink and fan combination. Aluminum is the primary choice for field/mobile applications, automotive, medical, and aerospace applications.
There are more exotic (and expensive) materials such as magnesium, titanium, and a variety of hybrid alloys in an emerging market. These are typically found in niche applications more often than the industrial space, and come with increased costs.
Heat Exchange/Dissipation Gaskets
Gaskets offer a wide variety of increasingly efficient solutions for thermal management. Heat interface pads can efficiently transfer thermal energy from an LCD to a heat sink. Heat dissipation gaskets can cover flexible printed circuits to protect sensitive electronic components. Hybrid metal gaskets can transfer heat from a touch display to a housing or heat sink. Since gaskets are highly conformable, they can easily eliminate surface irregularities.
Gaskets can be used to mount displays, touch screens, optical filters, and complete assemblies. Lightweight and corrosion resistant, they can be laser cut and formed for a precise fit.
Hot mirrors are multilayer dielectric coated substrates (glass/plastic/film) that separate infrared (IR) from the visible part of the spectrum. This protects displays and optical components from solar heat and radiation. LCD components are very susceptible to high heat and solar energy. The “blackout” effect can happen quickly resulting in image degradation and in some cases permanent damage to sensitive components. This can be a critical failure in outdoor applications such as public use terminals, mobile computing devices, industrial controls, and military field applications.
Hot mirrors offer high optical transmittance combined with high IR blocking, making it ideal for everything from surgical lasers to fish finders. They can be combined with touch screens, EMI filters, and LCD heaters to survive the most demanding environments.
Extended Temperature Displays
Designing the right touch display starts with choosing the right LCD. LCDs of every size have a wide variety of features, and every manufacturer has their strengths and weaknesses. For industrial applications such as agricultural equipment or military field computing, heat and direct sunlight must be taken into consideration. Standard LCD operating temperatures are 0 to +50 degrees Celsius (0 to +122°F). That’s fine for the TV on your wall or the monitor on your desk, but not for walking around in the desert or in a hot factory. Once the display goes beyond that range, you start to get the “blackout” effect and lose the image. In some cases, the damage can be permanent. Extended temperature displays typically have an operating temperature of -30 to +85 degrees Celsius (-31° to +185°F), greatly reducing the risk of “blackout” for most industrial environments.
TI’s OFM Series Open Frame Monitors we exclusively selected extended temperature LCDs. This allows us to offer the option of sunlight readability, night vision, and dual-mode operation without the cost and time of sourcing a new panel and changing the entire assembly.
I’m sure I missed some things, but as you can see, when it comes to keeping things cool the menu is stacked. It’s the art of putting the right combination of these options together in a concrete solution to a complex problem that gets my team out of bed in the morning. From half-inch optical filters for cameras to parking lot kiosks, mobile computers on the battlefield, and more, we design and manufacture products that beat the heat. Our extensive experience with various high-reliability markets that share similar environmental challenges, yet have unique application requirements and design cycles make us a versatile partner for efficient solutions to thermal management in touch screen displays.
For more information on thermal management solutions or if you’re looking for the right partner for your next touch screen or display project, please contact us and let’s get working on a solution that solves your problem.