Agilent 5991-2803EN Analysis of Test Coupon Structures for the Extraction of High Frequency PCB Material Pro free download

File name 5991-2803EN Analysis of Test Coupon Structures for the Extraction of High Frequency PCB Material Pro

Analysis of Test Coupon Structures for the Extraction of High Frequency PCB Material Properties White Paper Heidi Barnes and Robert Schaefer Keysight Technologies Santa Rosa, USA Jose Moreira Advantest Corporation Boeblingen, Germany 02 | Keysight | Analysis of Test Coupon Structures for the Extraction of High Frequency PCB Material Properties - White Paper Abstract The driving forces behind low cost RF/Microwave mponents and the ever increasing data rates of the digital world have resulted in a proliferation of printed circuit board (PCB) materials and manufacturing techniques to provide cost effective solutions for modern day applications. This has resulted in the need for practical ways of identifying the frequency dependent loss properties of the after fabrication or "as-fabricated" PCB designs for accurate pre- and post- layout simulation. Variations in key parameters such as dielectric constant, loss tangent, dielectric height, etched trace width, surface rough- ness, glass weave, moisture content, etc. can easily reduce the effectiveness of simula- tions to predict the final design performance. Few companies have the time, money, or equipment to fully dissect a fabricated PCB and determine all of these key dimensions and material loss properties for a design. There is a strong need for simpler techniques, such as measurable test structures, that can enable extraction of material properties for improved accuracy of simulations. Recent papers using two transmission line lengths do demonstrate measurements of dielectric constant and complex loss tangent [1,2,3,4], but this method makes it difficult to predict the as-fabricated PCB trace width and dielec- tric height. The intent of this paper is to explore the addition of Beatty series resonant impedance structures [5] to improve the accuracy of extracting the as-fabricated PCB material properties for the purpose of constructing 3D-EM simulations. Keywords--material properties, PCB test structures, high speed digital, 3D-EM Introduction The proliferation of epoxy based multi-layer laminate PCBs for high speed digital circuits running at microwave frequencies puts new demands on the world of EM simulations. Recent publications have clearly shown that assuming dielectric loss to be constant with frequency may have worked well for narrow band microwave applications, but for wide band digital simulations it produces non-causal results. Surface roughness which could be ignored with high quality thin film circuits is sparking new debates [6,7] to understand the physics and accurately predict the variations seen between standard copper foil and low profile versions. One issue that has not been widely addressed is the as-fabricated transmission line etched trace widths and the dielectric height which are critical for the set-up of accurate multi-Gigahertz EM simulations. PCB fabrication can be very repeatable for a specific PCB design and fabricat