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White Paper Abstract

New liquid crystal polymer substrate for high frequency applications (2014)
Presented at IMAPS 2014, October 13-15, 2014 in San Diego, CA, USA.

Liquid crystal polymer (LCP) materials have been available to the electronics industry for over 20 years. Thin films made from these materials have held great promise with respect to high frequency applications, because of their inherent low moisture absorption, low dielectric constant, and loss tangent. The promise for LCPs has been to satisfy a wide variety of applications, where a range of materials has been used, each satisfying a specific niche. The incumbent materials include PTFE polymers filled with ceramics and glass weaves, hydrocarbon/ceramic composites, and various thermoset materials. In particular, LCP has been thought to be able to satisfy all requirements for millimeter and microwave organic materials, at a lower cost. Until now LCPs have only satisfied niche applications in these markets. One of the major reasons is due to the fact that there are very specialized processes to make a uniform LCP film, which are not very cost effective and are volume limited. In addition, these processes can only provide for thin films which are appropriate for flex applications, and not for the mainstream rigid board specifications of major high frequency applications. Other problems with the incumbent technology include high variation of layer thickness, due to the requirement for post processing in the film manufacturing process, multilayer via reliability issues due to high coefficient of thermal expansion in Z axis, and manufacturability issues for multilayers due to limitations on current LCP “bond ply”. Dupont® and iQLP are jointly developing liquid crystal polymer film and laminates which solves the previous limitations with respect to this technology, which will be positioned to be the first LCP material to meet organic rigid board high frequency requirements. Also, this material has the promise to meet a wide variety of applications, which currently require multiple material sets. The innovation is based on new materials science which overcomes previous limitations with respect to properties and manufacturability. In particular these materials can be easily processed to achieve a wide variety of thickness’s and very tight thickness specifications, and meets the rigid board requirements. Also bond plies have been developed with characteristics so as to allow for ease of multilayer PCB assembly, and mechanical properties have been tailored to minimize stresses on vias in multilayer systems for high reliability. In this work we present our initial findings with this new material system. With our new set of properties we will show reliability data on multilayer LCP PCBs with various sizes of vias, establishing a promising threshold of reliability, using a new LCP bond ply material. In addition we are presenting insertion loss data at frequencies above 70 GHz, on circuits showing that this material has better loss properties than much more expensive premium material such as low temperature co-fired ceramics.