|A publication of the National Electronics Manufacturing Center of Excellence||June 2003|
Michael D. Frederickson
Flex To Install applications require the flexible connectors to withstand flexing during the initial installation and /or subsequent service operations. An example of this application is the interconnection of stationary PCB's within an assembly.
Dynamic Flex applications require the flexible connectors to withstand continuous flexing for the number of cycles as required by the application involved. An example of this type of application may be found inside a robotic arm requiring several hundred thousand cycles throughout it's lifetime.
Additional end use considerations involve the operating temperature of the end product. If the product is required to operate above 105 C or is subject to specific UL criteria, the selection of material used to manufacture the flexible connector is critical.
The table below shows various operating characteristics to be considered when choosing a flex material.
Bondply is simply a flexible adhesive film used to bond together multiple flexible layers. A special conductive adhesive, known as Anisotropic, can be used to electrically and mechanically connect vertically adjacent pads while maintaining isolation of the laterally adjacent conductors.
|Conductor plating critical issues must also be considered. If conductor thickness is critical use a pad only selective plating process. Nickel plating over flexible sections can present problems because of the brittleness of the nickel. If you are using tin lead plating, it should be fused to the conductor.
For optimal performance, the conductor layout (see Figure 2) in the bend area should meet the following requirements:
In the following examples the material thicknesses used in the calculations are:
Laminate material: 50 um
Understanding the requirements and limitations of flexible connector circuits and their associated materials will yield designs that provide a reliable service life. If you would like additional information on flex circuits or any other subject related to electronic design and assembly, contact the EMPF Helpline @ 610-362-1320.
|ACI Technologies, Inc. - - www.aciusa.org - - (610)362-1200|