Flex Classifications

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Flex classification is crucial for identifying the type of flexible printed circuit board you are designing. Make sure you know what the standards and requirements are before beginning your design. This will save you time and effort in the long run. Let’s delve a bit deeper into what the different flex classes and types are, as well as the differentiators for both.

Flex Classes

Flex classes vary depending on the level of inspection and testing required, and the performance requirements of the finished product. There are three different classes.

Class One
Suitable For: General Electronic Products
Includes consumer products, some computer and computer peripherals suitable for applications where cosmetic imperfections are not important and the major requirement is function of the completed printed board. Requires minimum inspection, testing, and performance standards. Applications include disposable electronics.

Class Two
Suitable For: Dedicated Service Electronic Products
Includes communications equipment, sophisticated business machines, instruments where high performance and extended life is required and for which uninterrupted service is desired but not critical. Requires medium inspection, testing, and performance standards. More expensive than class one, the applications of these boards include cameras, smartphones, and medical diagnostic equipment.

Class Three
Suitable For: High-Reliability Electronic Parts
Includes equipment and products where continued performance on demand is critical. Equipment downtime cannot be tolerated and must function when required such as in life support items or flight control systems. Printed boards in this class are suitable for applications where high levels of assurance are required and service is essential. Requires highest inspection, testing, and performance standards. These are the most expensive flex boards. Applications include medical devices and military/aerospace electronics.

Flex Type

Flex type depends on the number of conductive layers, construction and materials, and the presence or absence of plated-through holes.

IPC Type 1
Single-sided flexible printed circuit board. This is the most common type of flex circuit, ideal for dynamic flex applications. Contains one conductive layer. Can be found with and without stiffeners. SMT lands accessible only on one side.
IPC Type 2
Double-sided flexible printed circuit boards. Contains two conductive layers with plated-through holes. Can be found with or without stiffeners. Copper is bonded on both sides of the base material, then drilled, plated, etched and insulated on both sides by a top and bottom dielectric coverlayer.
IPC Type 3
Multilayer flexible printed circuit board. Contains three or more conductive layers with plated-through holes. The plated-through holes are used to create the interconnection of the conductive layers. Can be found with or without stiffeners.
IPC Type 4
Multilayer rigid and flexible material combinations containing three or more conductive layers with plated-through holes.
IPC Type 5
Flexible or rigid-flex printed circuit boards. Contains two of more conductive layers. No plated through-holes.

Want to learn more about flexible PCBs? Download our Flex Design Guide!

Flex Design Guide


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