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30 PCB007 MAGAZINE I MAY 2018 Feature by Stig Källman, ERICSSON with Happy Holden, I-CONNECT007 Introduction The material toolbox idea first came up when I saw the IPC appendix list for standard 1-ply stack-ups. The idea is to make a very simple bill of materials, specifications and notes, and possibly use the same prepreg/resin in the laminate and in the core. This article will introduce the material tool- box concept by discussing seven important factors: 1. Standardization 2. Toolbox idea 3. Materials concerns 4. Technology drivers 5. Material needs 6. Future 7. Products In the past, I came across many designers who wished to have the best specifications for impedance. They all start with specifying an impedance and conductor width that will make this according to their field solver. The conductor thickness is given as a constant due to plating or the base copper and the mini - mum requirement in the hole. This sets the re- quirement for certain material CCL and pre- preg thicknesses. You may see this today in the material supplier's data sheets for many customers. If you start with what has the largest input to the impedance in the PCB you will find that it is dielectric thickness and conductor width that contribute the most. Accordingly, I reflect- ed on what could be used as a benchmark for robust design and found that the Big Mac tastes the same anywhere in the world. Not the best burger according to some, but it's my favor- ite as it's something I can relate to and rec- ognize. If I could copy this into our design toolbox I would have a design that, with the right recipe, would re-

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