Touchscreen Supply Chain
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Touchscreen Supply Chain Cypress Semiconductor White Paper By Darrin Vallis
Executive Summary
Introduction
This white paper provides an overview of the touchscreen supply chain. It describes the key components of the supply chain and the touchscreen modules available in the market.
A detailed understanding of the capacitive touchscreen supply chain is vital for customers considering touchscreen end products. The engagement model chosen should match the in-house design capabilities, component supplier value added services, and available options for module design and supply. In practical terms, the touchscreen supply chain works as shown in Figure 1. The four key components: controller, flex, sensor, and LCD pass through several processes before reaching the consumer in an end product. Figure 1. Touchscreen Supply Chain
Document No. 001-46842 Rev. **
June 13, 2008
Page 1 of 4
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Touchscreen Supply Chain
Controller IC Supplier The capacitive touchscreen controller is a semiconductor device which senses finger position on a touchscreen sensor. Different silicon architectures and sensing methods are used by various suppliers, which is beyond the scope of this document. Capacitive controllers can be grouped into two broad categories.
Projected Capacitive This method senses finger position on a sensor from the electric field projected through a substrate. It is typically implemented with one or more patterned ITO layers, applied to one or more transparent substrates. Projected capacitive is very durable, because users touch the top of a glass or plastic substrate, while the ITO layers are protected below. Coordinates are calculated from measuring signals off patterned ITO with a deterministic position. This makes projected sensing more accurate and repeatable than other capacitive sensing methods. Projected capacitive controllers generally require more sensing input pins for larger screens. In practical terms, they are limited to approximately a 10” diagonal screen for single chip solutions. Alternative solutions using multiple controller ICs or unique ITO patterning are also possible.
Surface Capacitive This method employs a single sheet transparent conductor applied to the sensor substrate, typically ITO on glass, film, or plastic. The method is cost effective and suitable for high volume manufacture with many well known techniques. Because finger position is determined by four sensors on the corners or edges of the panel, touchscreens may be scaled to thirty or more inches without increasing the controller IC pin count. There are also significant drawbacks, especially for smaller screens. First, sensing is accomplished via ITO on top of the touchscreen substrate. Even though the ITO may be protected by a thin hard coat, it is susceptible to scratches from fingers, rings, keys, and so on. In addition, inherent non-linearity of the sensing field for surface capacitive must be corrected though edge patterning, software, or hardware methods. This linearization effect becomes more pronounced with smaller screens. Other implementation details such as proximity effect and finger shadow must also be addressed.
Flex Supplier Flexible printed circuit assemblies (flex) are used to connect the touchscreen sensor to a system controller board. The flex sometimes has a touchscreen controller mounted for supply as a “flex module”. Alternatively, a simple flex circuit without controller may be supplied to the sensor manufacturer, in which case a controller IC is built into the customers’ system controller board.
Sensor Supplier Typically referred to as the “glass” or “film” supplier, this member of the supply chain has in-house capabilities to create conductive patterning on a transparent substrate material. The most common conductor is indium-tin oxide (ITO) used for its relatively low resistance and high optical clarity. Other transparent conductors are in use or in development, but are not yet main stream. Typical sensor substrates are glass, film, or polycarbonate plastic derivatives. Some sensor suppliers have additional vertical integration, such as touchscreen controller IC ASIC products, electrical engineering for controller boards, LCD supply, flex connector supply, or complete module integration.
LCD Supplier Touchscreens are typically used in conjunction with video displays, so it is logical for LCD manufacturers to be essential in the supply chain. Their core competencies already involve depositing patterned ITO on glass and flex circuit design for LCD manufacture. It is therefore much easier for them to vertically integrate these key elements of the touchscreen supply chain. LCD manufacturers have chosen to simply supply displays to a third party for integration into touchscreen modules, or integrate the controller, sensor glass, or flex circuit into their assembly process.
Document No. 001-46842 Rev. **
June 13, 2008
Page 2 of 4
[+] Feedback
Touchscreen Supply Chain
Supply Chain Logistics Supply chain logistics for touchscreen manufacture has several permutations, depending on the supplier-customer sales engagement, customer preferred business model, and vertical integration of each supplier. Customers may initially consider purchasing touchscreen controllers, sensors, flex, and LCD directly from each supplier, and performing their own design and integration. Although this may have perceived cost advantages, it places all design, performance, and quality issues directly on the customer. Each touchscreen design is unique, so the controller must be configured to work properly with the sensor characteristics, LCD noise, and environmental and industrial design factors. This is often outside the customers’ capabilities for a first design. The more often used approach is for customers to purchase a custom designed and tested known good “touchscreen module”, from one of the supply chain members.
Touchscreen Modules Touchscreen modules are sold in three main varieties depending on the specific end customer:
Flex Module This is a combination of controller IC and flexible printed circuit. Flex modules are mainly purchased by ITO sensor suppliers to reduce touchscreen design cycle time and improve touchscreen yield. The flex module consists of a flexible circuit with an attached touchscreen controller IC, tested as a known good unit. Flex modules are typically supplied to ITO manufacturers or design end customers via controller IC distribution channels. For the Asian market, these are typically “Stocking Reps”, who function as a combination of manufacturer representatives and value added supply chain managers.
Touchscreen Module This product combines a flex module and ITO sensor. Using the flex module improves time to market and product reliability, while maintaining flexibility for sensor design. Touchscreen modules are usually offered by suppliers of the ITO sensor glass or film to large OEM or ODM design end customers. Some controller IC manufacturers also offer complete touchscreen modules for ease of engineering design, although this offering is usually limited to large direct customers. Most large customers have very specific marketing requirements for industrial design and product “look and feel”. Subsequently, very few companies use an off-the-shelf touchscreen module. The majority are custom designed directly with component suppliers.
Touchscreen LCD Module This is the highest level of integration. It combines a touchscreen module with an LCD to create a full touch sensitive display device. Design end customers see this device as a black box, capable of displaying images and sending touch coordinates to the main system. It is highly preferable in terms of manufacturing reliability, because each unit guarantees a known good display and touch interface. Some LCD manufacturers offer this type of module as a product to the general market. For high volume OEM customers, touch sensor manufacturers also take LCDs on consignment and produce a touchscreen LCD module from glass, flex, and controller IC components.
Summary Understanding the details of how touchscreens are produced helps you make the right choice of technology and suppliers for your touchscreen enabled device.
Document No. 001-46842 Rev. **
June 13, 2008
Page 3 of 4
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Touchscreen Supply Chain
All trademarks or registered trademarks referenced herein may be the property of their respective owners.
Cypress Semiconductor 198 Champion Court San Jose, CA 95134-1709 Phone: 408-943-2600 Fax: 408-943-4730 http://www.cypress.com
© Cypress Semiconductor Corporation, 2008. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign), United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without the express written permission of Cypress. Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. Use may be limited by and subject to the applicable Cypress software license agreement.
Document No. 001-46842 Rev. **
June 13, 2008
Page 4 of 4
[+] Feedback
Executive Summary
Introduction
This white paper provides an overview of the touchscreen supply chain. It describes the key components of the supply chain and the touchscreen modules available in the market.
A detailed understanding of the capacitive touchscreen supply chain is vital for customers considering touchscreen end products. The engagement model chosen should match the in-house design capabilities, component supplier value added services, and available options for module design and supply. In practical terms, the touchscreen supply chain works as shown in Figure 1. The four key components: controller, flex, sensor, and LCD pass through several processes before reaching the consumer in an end product. Figure 1. Touchscreen Supply Chain
Document No. 001-46842 Rev. **
June 13, 2008
Page 1 of 4
[+] Feedback
Touchscreen Supply Chain
Controller IC Supplier The capacitive touchscreen controller is a semiconductor device which senses finger position on a touchscreen sensor. Different silicon architectures and sensing methods are used by various suppliers, which is beyond the scope of this document. Capacitive controllers can be grouped into two broad categories.
Projected Capacitive This method senses finger position on a sensor from the electric field projected through a substrate. It is typically implemented with one or more patterned ITO layers, applied to one or more transparent substrates. Projected capacitive is very durable, because users touch the top of a glass or plastic substrate, while the ITO layers are protected below. Coordinates are calculated from measuring signals off patterned ITO with a deterministic position. This makes projected sensing more accurate and repeatable than other capacitive sensing methods. Projected capacitive controllers generally require more sensing input pins for larger screens. In practical terms, they are limited to approximately a 10” diagonal screen for single chip solutions. Alternative solutions using multiple controller ICs or unique ITO patterning are also possible.
Surface Capacitive This method employs a single sheet transparent conductor applied to the sensor substrate, typically ITO on glass, film, or plastic. The method is cost effective and suitable for high volume manufacture with many well known techniques. Because finger position is determined by four sensors on the corners or edges of the panel, touchscreens may be scaled to thirty or more inches without increasing the controller IC pin count. There are also significant drawbacks, especially for smaller screens. First, sensing is accomplished via ITO on top of the touchscreen substrate. Even though the ITO may be protected by a thin hard coat, it is susceptible to scratches from fingers, rings, keys, and so on. In addition, inherent non-linearity of the sensing field for surface capacitive must be corrected though edge patterning, software, or hardware methods. This linearization effect becomes more pronounced with smaller screens. Other implementation details such as proximity effect and finger shadow must also be addressed.
Flex Supplier Flexible printed circuit assemblies (flex) are used to connect the touchscreen sensor to a system controller board. The flex sometimes has a touchscreen controller mounted for supply as a “flex module”. Alternatively, a simple flex circuit without controller may be supplied to the sensor manufacturer, in which case a controller IC is built into the customers’ system controller board.
Sensor Supplier Typically referred to as the “glass” or “film” supplier, this member of the supply chain has in-house capabilities to create conductive patterning on a transparent substrate material. The most common conductor is indium-tin oxide (ITO) used for its relatively low resistance and high optical clarity. Other transparent conductors are in use or in development, but are not yet main stream. Typical sensor substrates are glass, film, or polycarbonate plastic derivatives. Some sensor suppliers have additional vertical integration, such as touchscreen controller IC ASIC products, electrical engineering for controller boards, LCD supply, flex connector supply, or complete module integration.
LCD Supplier Touchscreens are typically used in conjunction with video displays, so it is logical for LCD manufacturers to be essential in the supply chain. Their core competencies already involve depositing patterned ITO on glass and flex circuit design for LCD manufacture. It is therefore much easier for them to vertically integrate these key elements of the touchscreen supply chain. LCD manufacturers have chosen to simply supply displays to a third party for integration into touchscreen modules, or integrate the controller, sensor glass, or flex circuit into their assembly process.
Document No. 001-46842 Rev. **
June 13, 2008
Page 2 of 4
[+] Feedback
Touchscreen Supply Chain
Supply Chain Logistics Supply chain logistics for touchscreen manufacture has several permutations, depending on the supplier-customer sales engagement, customer preferred business model, and vertical integration of each supplier. Customers may initially consider purchasing touchscreen controllers, sensors, flex, and LCD directly from each supplier, and performing their own design and integration. Although this may have perceived cost advantages, it places all design, performance, and quality issues directly on the customer. Each touchscreen design is unique, so the controller must be configured to work properly with the sensor characteristics, LCD noise, and environmental and industrial design factors. This is often outside the customers’ capabilities for a first design. The more often used approach is for customers to purchase a custom designed and tested known good “touchscreen module”, from one of the supply chain members.
Touchscreen Modules Touchscreen modules are sold in three main varieties depending on the specific end customer:
Flex Module This is a combination of controller IC and flexible printed circuit. Flex modules are mainly purchased by ITO sensor suppliers to reduce touchscreen design cycle time and improve touchscreen yield. The flex module consists of a flexible circuit with an attached touchscreen controller IC, tested as a known good unit. Flex modules are typically supplied to ITO manufacturers or design end customers via controller IC distribution channels. For the Asian market, these are typically “Stocking Reps”, who function as a combination of manufacturer representatives and value added supply chain managers.
Touchscreen Module This product combines a flex module and ITO sensor. Using the flex module improves time to market and product reliability, while maintaining flexibility for sensor design. Touchscreen modules are usually offered by suppliers of the ITO sensor glass or film to large OEM or ODM design end customers. Some controller IC manufacturers also offer complete touchscreen modules for ease of engineering design, although this offering is usually limited to large direct customers. Most large customers have very specific marketing requirements for industrial design and product “look and feel”. Subsequently, very few companies use an off-the-shelf touchscreen module. The majority are custom designed directly with component suppliers.
Touchscreen LCD Module This is the highest level of integration. It combines a touchscreen module with an LCD to create a full touch sensitive display device. Design end customers see this device as a black box, capable of displaying images and sending touch coordinates to the main system. It is highly preferable in terms of manufacturing reliability, because each unit guarantees a known good display and touch interface. Some LCD manufacturers offer this type of module as a product to the general market. For high volume OEM customers, touch sensor manufacturers also take LCDs on consignment and produce a touchscreen LCD module from glass, flex, and controller IC components.
Summary Understanding the details of how touchscreens are produced helps you make the right choice of technology and suppliers for your touchscreen enabled device.
Document No. 001-46842 Rev. **
June 13, 2008
Page 3 of 4
[+] Feedback
Touchscreen Supply Chain
All trademarks or registered trademarks referenced herein may be the property of their respective owners.
Cypress Semiconductor 198 Champion Court San Jose, CA 95134-1709 Phone: 408-943-2600 Fax: 408-943-4730 http://www.cypress.com
© Cypress Semiconductor Corporation, 2008. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign), United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without the express written permission of Cypress. Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. Use may be limited by and subject to the applicable Cypress software license agreement.
Document No. 001-46842 Rev. **
June 13, 2008
Page 4 of 4
[+] Feedback
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