SITO vs DITO: Structure Differences in Touch Panels

In industrial capacitive touch panels, sensor structure directly affects optical performance, signal quality, manufacturing yield, and reliability.

Among common architectures, SITO (Single ITO) and DITO (Double ITO) represent two different routing strategies.
Although both are based on the same capacitive sensing principle, their internal layer structure and manufacturing complexity are fundamentally different.

This article examines the structural and process-level differences between SITO and DITO, and how these differences impact performance and application selection.

Basic Structure of Capacitive Touch Sensors

A capacitive touch sensor consists of X-axis and Y-axis electrodes patterned from transparent conductive material, typically ITO.

The controller detects touch by measuring capacitance changes at the intersections of these electrodes.

The key structural question is:

Are X and Y electrodes routed on one conductive layer or on two separate layers?

This defines the difference between SITO and DITO.

Definition: SITO and DITO

• SITO (Single ITO)
  Both X and Y electrodes are fabricated on a single ITO layer.

• DITO (Double ITO)
  X electrodes and Y electrodes are fabricated on two separate ITO layers, separated by an insulation layer.

The sensing principle is identical.
Only the routing topology and insulation method are different.

Routing Topology: Single-Side vs Double-Side

SITO Routing

In SITO, X and Y lines must cross on the same surface.

Direct crossing is not allowed, so an insulated bridge structure is required at each crossing point.
This is implemented by the OG (Over Glass) process.

At each crossing:

• One line is insulated

• The other line bridges over it

This enables single-side routing, but introduces:

• Additional process steps

• Strict alignment requirements

• Local impedance discontinuities

DITO Routing

In DITO, X and Y electrodes are placed on different layers.

Line crossings are naturally isolated by the insulation layer.
No bridge structure is required.

This results in:

• Simpler routing

• Fewer critical process steps

• More uniform electrical topology

Manufacturing Complexity

The main process difference appears in SITO.

A simplified SITO process flow includes:

• Glass inspection

• First ITO deposition and patterning

• OG bridge formation by photolithography

• Second ITO deposition and patterning

• Final insulation and protection

The OG process is the core technical barrier.

It requires:

• High-precision photolithography

• Yellow-light cleanroom

• Strict defect control

Any defect in the bridge area may cause line break or short circuit.

DITO avoids this complexity:

• No bridge process

• Fewer lithography steps

• Higher tolerance to alignment error

As a result, DITO generally achieves higher yield and better process stability.

Impact on Optical and Electrical Performance

Optical Performance

SITO removes one conductive layer in the active area.

This leads to:

• Higher transmittance

• Lower reflection

• Slightly higher display brightness

DITO has one additional conductive layer, which introduces:

• Slightly higher reflection

• Slightly lower transmittance

The difference is usually in the range of 3–8%.

Electrical Performance

SITO routing includes:

• Bridge structures

• Local impedance variation

• More complex signal paths

This requires tighter process control and tuning.

DITO offers:

• More uniform line impedance

• Better signal consistency

• Higher noise margin

For large-size panels and harsh EMI environments, DITO is usually more robust.

Yield, Cost, and Manufacturing Risk

From a production perspective:

SITO

• Multiple critical lithography steps

• Sensitive bridge structure

• Lower yield

• Higher unit cost

• Higher manufacturing risk

DITO

• Simpler process

• Higher yield

• Better long-term stability

• Lower cost

• Lower manufacturing risk

This is the primary reason why DITO is preferred for mass production and cost-sensitive projects.

Typical Application Selection

SITO is typically used when the project prioritizes:

• Optical quality

• Thin structure

• Narrow bezel

• High-end appearance

Typical fields:

• Medical imaging

• Precision instruments

• Aerospace and defense

• High-end outdoor equipment

DITO is typically used when the project prioritizes:

• Yield and stability

• Cost control

• Large size

• Long-term reliability

Typical fields:

• Industrial HMI

• Factory automation

• Commercial terminals

Conclusion

SITO and DITO differ mainly in routing topology and manufacturing complexity.

• SITO offers better optical performance and thinner structure, at the cost of higher process complexity and lower yield.

• DITO offers simpler structure and higher manufacturing stability, at the cost of slightly lower optical performance.

The choice between SITO and DITO should be based on application requirements, manufacturing risk, and cost constraints, rather than on a single performance parameter.