The world of touch screen technology is filled with acronyms—GG, GFF, PG, CG, FOG. For product designers and engineers, navigating this terminology is critical to selecting the right components for their application. A misunderstanding of these fundamental structures can lead to costly design errors, suboptimal performance, or unnecessary expenses. This guide provides a definitive breakdown of these common touch screen acronyms, moving logically from core sensor structures to complete touch monitor assemblies. By the end, you will have a clear and comprehensive understanding of the touch screen stack-up, empowering you to make informed decisions for your next project.
The Foundation: Core Sensor Structures (GG, GFF, GF, PG)
At the heart of any capacitive touch panel is the sensor structure, which dictates the panel's primary characteristics. These structures define how the conductive ITO (Indium Tin Oxide) layers are arranged.
The Classic Choice: GG (Glass-on-Glass) for Maximum Durability
The GG (Glass-on-Glass) structure is renowned for its robustness and superior optical performance. It consists of a top Cover Glass (CG) and a separate glass sensor substrate below it. The X and Y axes of the ITO conductive grid are etched onto this single sensor glass layer.
- Advantages: Superior durability, high scratch resistance, and excellent optical clarity due to the all-glass construction.
- Ideal For: Industrial HMIs, medical devices, outdoor kiosks, and any application where ruggedness is the top priority.
The Flexible Option: GFF (Glass-on-Film-on-Film) for Thinner Designs
The GFF (Glass-on-Film-on-Film) structure prioritizes a slim profile and cost-effectiveness. It uses a top Cover Glass, but the sensor is composed of two separate layers of optical PET film. One film carries the X-axis ITO pattern, and the other carries the Y-axis.
- Advantages: Significantly thinner and lighter than GG, more cost-effective, and offers greater design flexibility.
- Ideal For: Consumer electronics, portable devices, and smart home panels where a sleek, lightweight design is essential.
The Hybrid Solution: GF (Glass-on-Film)
The GF (Glass-on-Film) structure is a hybrid approach. It uses a single film layer for the sensor, with the X and Y ITO traces intricately patterned on the same layer. This simplifies the stack-up compared to GFF, offering a good balance between the thickness of GFF and the optical performance of GG.
- Advantages: Thinner than GFF, good optical performance, and a balanced cost.
- Ideal For: A wide range of applications, including automotive displays and high-end smart appliances.
The Premium Variant: PG (Plastic-on-Glass)
In a PG (Plastic-on-Glass) structure, the top cover lens itself is made of a durable plastic (like polycarbonate or PMMA) instead of glass. The sensor below it is typically a glass substrate (similar to GG).
- Advantages: High impact resistance (plastic is less prone to shattering than glass), lightweight, and allows for complex 3D curved surfaces.
- Ideal For: Wearable devices, ruggedized handheld terminals, and products with unconventional form factors.
A Critical Component: Understanding CG (Cover Glass) and FOG (Film-on-Glass)
Beyond the core sensor structures, two other acronyms are vital for understanding the supply chain and assembly process.
CG (Cover Glass): More Than Just Protection
CG (Cover Glass) refers specifically to the top protective layer of the touch screen. While its primary role is protection, the CG is also a critical design element. It can undergo various enhancements:
- Surface Treatments: Anti-glare (AG), anti-reflective (AR), and anti-fingerprint (AF) coatings.
- Customization: Custom shapes, cutouts, and printed borders or logos.
FOG (Film-on-Glass): The Pre-Bonded Sensor Module with FPC
FOG (Film-on-Glass) is not a complete touch panel structure itself, but rather a sub-assembly. It consists of the flexible printed circuit (FPC) tail, containing the driver IC, which has been bonded to the glass sensor substrate. A manufacturer might purchase a FOG component and then laminate their own custom CG on top.
The Next Level: Touch Display Assembly Options
A touch sensor is rarely used in isolation. The next logical step in product integration is the Touch Display Assembly, which combines the touch panel with an LCD or OLED display.
GG + Display Assembly: For Rugged, High-Clarity Needs
This assembly combines the durable, optically superior GG touch panel with a display module. When optically bonded, this combination offers the best possible performance for demanding environments like medical operating rooms or outdoor industrial settings.
GFF + Display Assembly: For Slim, Cost-Effective Products
This is the most common assembly type for consumer electronics. The thin GFF touch panel is bonded to a display, creating a slim and lightweight module that is perfect for tablets, smartphones, and other portable devices.
CG + Display Assembly: Towards Advanced Integration
In advanced integration methods like On-Cell or In-Cell, the touch sensor function is built directly into the display's structure. In these cases, a custom CG is laminated directly onto the display module, resulting in the thinnest possible profile.
From Assembly to Final Product: The Complete Touch Monitor
The final step is to integrate the Touch Display Assembly with the necessary electronics and housing to create a finished product.
The Full Stack-up Formula: Sensor + Display + PCBA + Housing
A complete touch monitor is a system. It follows this basic formula:
- (GG/GFF/etc.) + Display forms the core visual and interactive component.
- This assembly connects to a PCBA (Printed Circuit Board Assembly), or mainboard, which drives the display and processes data.
- All these components are enclosed in a protective Housing (or chassis), which can be made of plastic or metal.
Key Considerations for Turnkey Touch Monitor Solutions
When sourcing a complete touch monitor, you are choosing a turnkey solution. Key factors to consider include the PCBA's processing power (e.g., ARM-based for Android, x86 for Windows), connectivity options (HDMI, USB, Ethernet), and the housing's mounting options and environmental ratings (e.g., IP65).
Comparison Table: Choosing the Right Structure for Your Application
To help you make an informed decision, this table summarizes the key trade-offs between the core sensor structures.
| Feature | GG (Glass-on-Glass) | GFF (Glass-on-Film-on-Film) | GF (Glass-on-Film) | PG (Plastic-on-Glass) |
|---|---|---|---|---|
| Durability | Excellent | Good | Very Good | Excellent (Impact) |
| Thickness | Thicker | Thinnest | Thinner | Varies (Allows Curves) |
| Optical Clarity | Excellent | Good | Very Good | Good |
| Cost | Higher | Lowest | Moderate | Higher |
| Ideal Application | Industrial, Medical | Consumer, Portable | Automotive, Appliances | Wearables, Rugged |
Navigating the World of Touch Screens with Confidence
Understanding the language of touch screen structures is the first step toward successful product development. By grasping the fundamental differences between GG, GFF, GF, PG, and how they integrate into assemblies like FOG and complete monitors, you can communicate your requirements clearly and select a solution that perfectly balances performance, design, and cost.
Frequently Asked Questions (FAQ)
1. What is the difference between FOG and COF (Chip-on-Film)? FOG (Film-on-Glass) describes bonding the FPC tail (which contains the chip) to the glass sensor. COF (Chip-on-Film) is a more specific term for the process of mounting the driver IC directly onto the flexible film of the FPC itself. FOG is a broader assembly term.
2. In a Touch Display Assembly, is optical bonding always used? No, not always. The touch panel and display can be joined using either air bonding (bonded only at the edges) or optical bonding (the gap is filled with adhesive). Optical bonding provides superior optical performance and durability but is a more premium process.
3. How does choosing a structure like GFF affect the choice of a PCBA mainboard? The sensor structure (like GFF) itself does not directly dictate the PCBA choice. However, the product's overall goals do. A cost-effective GFF panel for a consumer tablet will likely be paired with a consumer-grade ARM-based PCBA, while a rugged GG panel for an industrial monitor might be paired with a more robust, wide-temperature industrial-grade PCBA. The choices are complementary. For help selecting the right combination for your project, you can consult with our engineering experts.
