Touch Screen Supply Chain

Executive Summary
This white paper provides an overview of the supply chain touchscreen. It describes the key elements of the supply chain and touch screen modules available on the market.

Introduction
A detailed understanding of supply chain capacitive touch screen is vital for businesses considering the finished product touch screen. The engagement model chosen must match the in-house design capabilities, component supplier of value added services and options available to design and supply modules.

Controller IC Supplier
The controller of capacitive touch screen is a semiconductor device that senses finger position on a touch sensor. Silicon architectures and different detection methods are used by different suppliers, which is beyond the scope of this document. Capacitive controllers can be grouped into two broad categories.

Projected Capacitive
This method senses the position of the finger on a sensor electric field projected through a substrate. It is typically implemented with one or more reasons ITO layers applied to one or more transparent substrates. Projected Capacitive very sustainable, because users touch the top of a substrate of glass or plastic, while the ITO layers are covered below. The coordinates are calculated from the measured signals off ITO patterned with a deterministic position. This makes detection more accurate projections and reproducible than other methods of capacitive sensing. Projected Capacitive controllers generally require more detection input pins for larger screens. In practical terms, they are limited to about 10 "diagonal screen, single-chip solutions. Alternatives circuits using multiple controllers or ITO unique shape are also possible.

Surface Capacitive
This method uses a single transparent conductive foil applied to the sensor surface, usually on the ITO glass, film, or plastic. The method is cost effective and suitable for high volume manufacturing with many well-known techniques. Because the position of the fingers is determined by four sensors on the corners or edges of the panel, touch screens may be reduced to thirty inches or more without increasing the controller Pin Count IC. There are also major drawbacks, especially for small screens. Firstly, the detection is performed using ITO on top of the touchscreen substrate. Even if the ICO may be protected by a thin hard layer, it is susceptible to scratching fingers, rings, keys and so on. In addition, inherent non-linearity of the field of capacitive sensing surface must be corrected through board structure, software or hardware methods. The effect of linearization becomes more pronounced with smaller screens. Other implementation details such as the proximity effect and the shadow of the fingers, must also be addressed.

Flex Supplier
Blends of flexible printed circuit (flex) are used to connect the touch sensor to a controller card system. The flex was sometimes a touch controller mounted to the power module as a "flex". Alternatively, a single flex circuit without controller may be delivered to the manufacturer of sensors, in which case controller IC is embedded in the card controller system customers.

Sensor Supplier
Usually referred to as the "glass" or "cinema" provider, this member of the supply chain has the internal capacity to create patterning a conductive transparent substrate. The driver is the most common oxide of tin-indium (ITO) was used for its relatively low resistance and high optical clarity. Other drivers are transparent in operation or under development, but are not yet mainstream. Typical sensor substrates are glass, film or derivatives of polycarbonate plastic. Some suppliers of sensors have additional vertical integration, such as ASIC products touchscreen controller IC, power engineering to the controller boards, LCD supply, supply flex connector or the integration of the complete module.

LCD Supplier
Touch screens are usually used in conjunction with video screens, it makes sense for LCD makers as crucial in the supply chain. Their basic skills already involve depositing ITO on glass designs and design flex circuits for LCD manufacturing. It is much easier for them to vertically integrate these key elements of the supply chain touchscreen. LCD makers have chosen to simply provide displays third for integration into modules of the touch screen, or integrate the controller, glass sensor, flex circuit or in their assembly process.

Supply Chain Logistics
Logistics supply chain for the manufacture of the touch screen has many permutations, depending on supplier sales customer participation, companies preferred customer model, and vertical integration of each supplier. Customers May first consider the purchase of touch screen controllers, sensors, flex and LCD directly from each vendor, and making their own design and integration. While this may have perceived cost advantages, it puts all design, performance and quality directly on the client. Each touchscreen design is unique, the controller must be configured to work correctly with the characteristics of the sensor, LCD screen noise and environmental factors and industrial design. This is often beyond the capacity of clients for an initial design. The approach most often used is for customers to purchase custom designed and tested module called "good touch screen," one of the members of the supply chain.

Touchscreen Modules
Touchscreen modules are sold in three main varieties depending on the specific end customer:

Flex Module
It a combination of controller IC and the flexible printed circuit. Flex Modules are mainly purchased by ITO sensor suppliers touch screen to reduce design time and improve cycle performance touchscreen. The flexural modulus is composed of a flexible circuit with an attached touch controller IC, tested as a known good unit. Flex Modules are usually provided to manufacturers of ITO or final customers design through distribution channels controller IC. For the Asian market, are typically "Stocking Reps, which function as a set of manufacturer's representatives and officials of value added supply chain.

Touch Screen Module
This product combines a flexural modulus and the ITO sensor. Using the bending modulus improves time to market and product reliability, while maintaining flexibility for the design of the sensor. Touchscreen modules are usually offered by suppliers of ITO glass sensor or film to major OEM customers or end design MDGs. Some manufacturers of integrated circuits controller modules also enable touch screen to facilitate the design technique, although this offer is generally limited to large customers direct. Most large customers have very specific requirements for marketing and industrial design, product look and feel ". Subsequently, very few companies use an off-the-shelf module touch. Most are designed directly with component suppliers.

Touchscreen LCD Module
This is the highest level of integration. It combines a touch screen module with an LCD screen to create a display touch sensitive text. End customers design See this product as a black box capable of displaying images and send the contact details of the main system. It is highly preferable in terms of reliability of manufacture, because each unit provides a display of known quality and a touch interface. Some manufacturers offer this type LCD module as a product on the market generally. For OEM customers with high volume manufacturers of LCD touch sensor are also recording and producing a touchscreen LCD module from glass, flex, components and IC controller.

Summary
Understanding the details of how touch screens are produced to help you make the right choice of technology and vendors for your touchscreen enabled device.