Making the stack stick: bonding and DTCs

By Alexander Sommerfeld | 10 September 2024

Like most things in life, displays change, evolve and, happily, improve. As classic displays and control elements are increasingly being replaced by modern display stacks (Display Touch Cover lens or DTC), naturally new processes will come into play to bond the cover glasses or DTCs into their housings.

As the word ‘stack’ might suggest, various parts of these displays are bonded together. Firstly, the cover glass is bonded over its entire surface with a touch sensor using a transparent adhesive. The cover glass touch unit is then bonded to the display module using the same method.

Either a damping or structural adhesive can be used for the subsequent bonding of the display stack into a frame or housing. Of course, we must add a brief caveat here, as the overall process depends on several factors: the application area, material, DTC design and construction requirements. Because bonding a display stack isn’t always as straightforward as it might seem and there are plenty of considerations and challenges to be taken into account at every stage.

For example, the bonds must be resistant to moisture, grease, chemicals and UV rays. Then, additionally, each material expands and contracts at different rates and the chosen adhesive must be able to compensate for this. This means that judgements must be made in the early stages to decide which kind of bonding is the most appropriate. Simply – it’s all about the pros and cons.

Double-sided tape bonding
Pros - ‘Easier’ bonding in the front frame
- Fast further processing of the assembly (DTC + front frame)
- Cost-effective solution
Cons - Visible gap between front frame and cover glass
- Dirt accumulation in the joint

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Liquid adhesive bonding
Pros - Gap between front frame and cover glass is filled, which contributes to better sealing (protects against penetrating humidity)
- Achievable protection class IP6X
- Ensures better stability between frame and DCT
- Enhance optics (less reflection leads to higher brightness and contrast)
- Prevents glass splinters from flying around when the cover glass is destroyed
Cons - The liquid adhesive takes longer to harden than the tape
- The further processing of the assembly takes longer
- High effort when dosing and positioning the parts

Displays must withstand dust, rain, and snow without compromising performance.  Our displays feature IP sealing with specialized tapes, glue or silicone to protect against environmental elements, ensuring reliability in any weather condition.

With ratings such as IP54, which offers splash-proof and dust-proof capabilities, and IP65, providing protection against water jets, manufacturers can ensure their products stand up to the elements. For the highest demands, IP67 guarantees dust-tight integrity and protection against 30 minutes immersion.

The use of liquid adhesive bonding effectively fills the gap between the front frame and cover glass, enhancing sealing performance. This method not only achieves an IP6X protection class but also demonstrates improved stability between the frame and DCT, making it essential for applications in demanding conditions.

About Author

Alexander Sommerfeld - Solution Manager Display Integration, Avnet Displays

After getting his diploma in mechatronics, Alexander entered the world of display solutions at MSC in 2006 as a designer for display housings. After a short time, he also took over as team coach for new product manufacturing of open frame display solutions. From 2010, he continued to work as a project developer in the display sector and supported sales and customers with design and integration. In 2013, Alexander took over the planning and completion of the clean rooms and the new display production line. After completion and relocation in 2015, he dedicated himself to the new task of optical bonding processes and specialized in this area.

In his current role as Solution Manager Display Integration, Alexander supports the Avnet team and their customers concerning the integration of display products into customer applications and steers and extends the product lines of SimplePlus and MipiPlus display solutions.
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