What is the thickness of a 2.76 inch 480x480 round display?

The thickness of a 2.76 inch 480x480 round display is not a single fixed number because it depends on the specific model, the type of touch panel integrated, and whether you are measuring the glass-only panel or the full module with backlight and FPC. For the most common variant, the 2.76 inch 480x480 round tft display module without a capacitive touch panel, the total thickness typically falls between 1.5 mm and 2.0 mm. However, if you add a touch sensor, the thickness can increase to between 2.5 mm and 3.5 mm. The exact thickness for a specific product is always listed in the mechanical drawing, and for the widely used DM-TFT28-479 model from DisplayModule, the module thickness is specified as 1.8 mm ± 0.1 mm for the standard version without touch. This is a critical dimension for any embedded system designer, because a 0.2 mm difference can mean the difference between a snug fit and a failed enclosure design. Let’s dive into the real data behind these numbers, covering the glass stack, the backlight unit, the FPC bending allowance, and how these factors affect your project.

The display itself is a 2.76-inch diagonal round TFT-LCD with a resolution of 480x480 pixels. The active area is approximately 49.92 mm x 49.92 mm, and the outer diameter of the glass is typically 70.0 mm. The glass substrate thickness for the TFT cell is usually 0.3 mm to 0.4 mm for the bottom glass and 0.2 mm to 0.3 mm for the color filter glass. When you bond these two layers together with liquid crystal in between, the total cell thickness is around 0.6 mm to 0.8 mm. This is just the bare LCD cell. The backlight unit adds significant thickness. For a round display, the backlight is a custom-shaped LED edge-lit light guide plate. The light guide plate itself is typically 0.4 mm to 0.6 mm thick, and the diffuser films, prism films, and reflector sheets add another 0.2 mm to 0.3 mm. The total backlight assembly, including the molded plastic frame, usually adds 1.0 mm to 1.2 mm to the overall module thickness. So, the combined thickness of the LCD cell plus the backlight is roughly 1.6 mm to 2.0 mm. The 1.8 mm figure for the DM-TFT28-479 sits right in the middle of this range. This is the thickness of the rigid part of the module, not including the FPC or any connector.

Now, the FPC (Flexible Printed Circuit) is a critical factor. The FPC itself is typically 0.1 mm to 0.2 mm thick, but it extends from the edge of the glass. The real thickness concern for the FPC is not its own thickness, but the thickness of the connector attached to it. The ZIF (Zero Insertion Force) connector on the FPC is usually 1.5 mm to 2.0 mm thick, and it can protrude beyond the edge of the module. When you bend the FPC under the display, the total stack height at the bending point can increase by 0.5 mm to 1.0 mm depending on the bend radius. For a 2.76-inch round display, the FPC is often routed to the back of the module, and the recommended bend radius is 1.0 mm. If you are designing a thin enclosure, you must account for the FPC bend radius, which effectively adds to the total thickness of the assembly. For example, if the module is 1.8 mm thick, and you bend the FPC with a 1.0 mm radius, the total space required behind the display is at least 2.8 mm to avoid pinching the FPC. This is a common mistake in mechanical design.

Touch panel integration is another major variable. The most common touch options for a 2.76-inch round display are capacitive touch (PCAP) and resistive touch. A capacitive touch sensor is usually a separate glass or film layer. A glass capacitive touch sensor is typically 0.4 mm to 0.7 mm thick, and when you optically bond it to the TFT cell, the total thickness increases by that amount. For example, a 1.8 mm module with a 0.5 mm glass touch sensor bonded with a 0.1 mm OCA (Optically Clear Adhesive) layer becomes 2.4 mm thick. A film-based capacitive touch sensor is thinner, around 0.1 mm to 0.2 mm, but it is less durable. Resistive touch panels are thicker, typically 0.7 mm to 1.2 mm, because they consist of two flexible films separated by spacer dots. If you choose a resistive touch version, the total module thickness can reach 2.5 mm to 3.0 mm. The datasheet for the 2.76 inch 480x480 round tft display from DisplayModule explicitly lists the thickness for the touch version as 2.8 mm, which is consistent with a glass capacitive touch sensor bonded to the TFT. This is a significant difference from the 1.8 mm non-touch version, and it directly impacts your enclosure design and bezel height.

Let’s look at the mechanical tolerances. The thickness of a round display is not uniform across the entire surface. The backlight frame often has a slightly thicker edge, sometimes by 0.1 mm to 0.2 mm, because of the injection molding gate or the LED placement. The LEDs themselves are typically 0.6 mm x 0.3 mm or 0.8 mm x 0.4 mm in size, and they are mounted on the edge of the light guide plate. The area around the LEDs can be up to 0.5 mm thicker than the center of the module. This is why you should always use the maximum thickness dimension from the drawing, not the typical value. For the DM-TFT28-479, the maximum thickness is 1.9 mm for the non-touch version, and 2.9 mm for the touch version. These tolerances are critical for press-fit or snap-fit enclosure designs. If you design a cavity that is exactly 1.8 mm, you will have interference with the module at the LED edge. You need at least 2.0 mm clearance for the non-touch version, and 3.1 mm for the touch version.

Now, let’s compare this to other round display sizes. A 1.28-inch round display (typically 240x240) has a module thickness of around 1.2 mm to 1.5 mm. A 1.54-inch round display (240x240) is about 1.5 mm to 1.8 mm. A 2.76-inch round display is at the upper end of the thin profile for this size class. In contrast, a 3.5-inch round display (480x480) is usually thicker, around 2.5 mm to 3.0 mm without touch, because the backlight needs more LEDs and a thicker light guide plate to maintain uniform brightness across the larger area. The 2.76-inch size is a sweet spot where you can still achieve a thin profile while maintaining good brightness (typically 350 cd/m² to 500 cd/m²). The number of LEDs in the backlight for a 2.76-inch round display is typically 6 to 9 LEDs, depending on the brightness requirement. Each LED is about 0.3 mm thick, and they are mounted on a flexible PCB that is 0.2 mm thick. The total thickness of the LED strip is around 0.5 mm, which is embedded in the backlight frame.

Another critical dimension is the thickness of the polarizer. The top polarizer is typically 0.1 mm to 0.15 mm thick, and the bottom polarizer is similar. These are already included in the glass cell thickness. The cover glass or lens that you might add on top of the display is a separate consideration. If you are using a round display in a smartwatch or a smart home device, you often add a cover glass of 0.5 mm to 1.0 mm thickness. This is not part of the display module thickness, but it adds to the total stack height. The air gap between the display and the cover glass is typically 0.2 mm to 0.5 mm if you are not using optical bonding. If you use optical bonding, the OCA layer is 0.1 mm to 0.2 mm thick, and it eliminates the air gap. So, the total stack height from the back of the display module to the top of the cover glass can be 1.8 mm (module) + 0.2 mm (OCA) + 0.7 mm (cover glass) = 2.7 mm for the non-touch version, or 2.8 mm (touch module) + 0.2 mm (OCA) + 0.7 mm (cover glass) = 3.7 mm for the touch version. This is the real-world thickness you need to plan for in your product.

The interface type also affects the mechanical design. The 2.76-inch 480x480 round display typically uses a MIPI DSI interface with 1 or 2 lanes, or a parallel RGB interface. The MIPI interface is more common for high-resolution round displays because it reduces the number of pins. The FPC for a MIPI interface is usually 0.1 mm to 0.15 mm thick, with a pitch of 0.3 mm to 0.5 mm. The connector on the FPC is a 0.3 mm or 0.5 mm pitch ZIF connector, which is about 1.5 mm thick. The connector itself is the thickest part of the FPC assembly. Some designs use a board-to-board connector, which can be thicker, up to 2.0 mm. The DM-TFT28-479 uses a 0.5 mm pitch ZIF connector, which is a standard choice for this size. The FPC length is typically 15 mm to 30 mm, and it is designed to be bent at a 90-degree angle. The bending area must be free of components, and the bend radius must be maintained to avoid stress on the copper traces.

Thermal management is another angle. The thickness of the display affects its thermal behavior. A thinner display has less thermal mass, so it heats up faster when the backlight is on. The backlight LEDs generate heat, and the temperature rise at the surface of the display can be 5°C to 15°C above ambient, depending on the brightness and the duty cycle. For a 1.8 mm thick module, the thermal resistance from the LEDs to the back of the module is lower than for a thicker module, so the heat is more easily transferred to the enclosure. If you are using a metal enclosure, you can use a thermal pad or thermal paste to conduct heat from the back of the display to the enclosure. The thermal pad thickness is typically 0.5 mm to 1.0 mm, which adds to the total stack height. This is a common consideration in smartwatch designs where the display is in direct contact with the skin.

Let’s break down the typical thickness values in a table for clarity:

Component	Thickness (mm)	Notes
Color filter glass	0.2 - 0.3	Top glass layer
Liquid crystal layer	0.005 - 0.01	Negligible in stack
TFT glass substrate	0.3 - 0.4	Bottom glass layer
Total LCD cell	0.6 - 0.8	Bare glass stack
Backlight light guide plate	0.4 - 0.6	PMMA or PC material
Backlight films (diffuser, prism, reflector)	0.2 - 0.3	Multiple layers
Backlight plastic frame	0.4 - 0.6	Molded frame
Total backlight assembly	1.0 - 1.2	Including frame
Module thickness (no touch)	1.6 - 2.0	Typical range
Capacitive touch sensor (glass)	0.4 - 0.7	Separate layer
OCA bonding layer	0.1 - 0.2	For touch bonding
Module thickness (with touch)	2.4 - 3.0	Typical range
FPC thickness	0.1 - 0.2	Flexible circuit
ZIF connector thickness	1.5 - 2.0	On FPC
FPC bend radius (minimum)	1.0	Required clearance

The brightness of the display is also related to the thickness. A thinner backlight has less space for light mixing, which can lead to hotspots near the LEDs. To achieve uniform brightness, the light guide plate must have a specific pattern of dots or microstructures. For a 2.76-inch round display, the typical brightness is 350 cd/m² to 500 cd/m², and the uniformity is usually >80%. The color gamut is typically 50% to 70% NTSC for standard TFTs, and 90% to 100% NTSC for IPS or high-color versions. The viewing angle is 80° to 85° in all directions for IPS, and 60° to 70° for standard TN. The thickness of the display does not directly affect the color gamut or viewing angle, but it does affect the optical bonding options. If you use a thicker cover glass, you may need a thicker OCA layer to fill the gap, which can slightly reduce the brightness by 1% to 3% due to light absorption in the adhesive.

The weight of the display is another factor. A 2.76-inch round display without touch typically weighs 10 grams to 15 grams. With a glass capacitive touch sensor, the weight increases to 15 grams to 20 grams. The thickness directly correlates with the weight because the materials have similar densities. For example, the glass used in the TFT cell has a density of about 2.5 g/cm³. The backlight plastic frame is typically ABS or PC, with a density of 1.0 to 1.2 g/cm³. The light guide plate is PMMA, with a density of 1.19 g/cm³. So, a 1.8 mm thick module has a lower weight than a 2.8 mm thick module, but the difference is only a few grams. This is important for wearable devices where every gram matters.

The interface voltage and power consumption are also related to the thickness indirectly. The driver IC is typically mounted on the glass using COG (Chip-on-Glass) technology. The driver IC itself is about 0.3 mm to 0.5 mm thick, and it is encapsulated with a protective epoxy. The COG area is on the bottom glass, and it adds to the local thickness of the module. The FPC is bonded to the glass using ACF (Anisotropic Conductive Film), which is about 0.02 mm to 0.05 mm thick. The total thickness of the bond area is slightly higher than the rest of the glass, but it is usually within the overall tolerance. The power consumption of the display is typically 100 mW to 300 mW for the backlight at full brightness, and 10 mW to 50 mW for the LCD driver. The thickness of the display does not directly affect the power consumption, but a thinner backlight may require more LEDs to achieve the same brightness, which can increase power consumption.

For the specific model DM-TFT28-479, the mechanical drawing shows the following critical dimensions: the active area diameter is 49.92 mm, the outer glass diameter is 70.0 mm, the module thickness is 1.8 mm ± 0.1 mm for the non-touch version, and 2.8 mm ±