DESIGN GUIDE Version 1.1 WIRELAID® Design Guide www.we-online.com Your benefit with WIRELAID® Caused by the increasing requirements of power and digital control electronics in almost every technological industry, PCB manufacturers are facing new challenges. To combine high currents and signals at the same time, the Wirelaid technology provides a partial power management as a competitive alternative to PCBs with thick copper technology or a parallel arrangement of additional layers. The concept of the Wirelaid technology is the use of embedded copper wires in a PCB. As a result, standard conductors, which can only manage low currents, become high current tracks. This allows for the combination of power and signal processing electronics on one single board. Available with UL listing type WE51 (UL 94 V-O). Wire types Flat wire 2 F 08 Cross-section area 0.8 x 0.25 mm2 Ø 0.2 mm2 F 14 Cross-section area 1.4 x 0.35 mm2 Ø 0.49 mm2 www.we-online.com Your advantages with WIRELAID® Reduced system volume Wires replacing the thick copper Heat reduction due to smaller cross-sectional area of copper Elimination of connectors Reduced number of layers Combination of power and signal processing electronics on one single PCB Reduction of system costs Improved heat dissipation Better soldering process in comparison with traditional thick copper technology Thinner copper layers Fewer thick copper areas through the use of partial power management WIRELAID® Production processes At the beginning of the Wirelaid process, the wires are fixed onto the under side of the copper foil using resistance welding. The wire is then welded again at the end of the trace and cut to the appropriate length. The “Wirelaid copper foil” is then laminated onto a multilayer PCB using standard production processes. As a result the “Wirelaid copper foil” forms the external layer of the PCB. Finally the outer tracks are created using standard PCB processes. PCB creation and technical specification When using Wirelaid technology in your PCB stack up, add an additional help layer in Gerber format showing the relevant wires and widths. top wirelaid_bottom (Help layer) bottom The combination of “bottom” and “wirelaid_bottom” represents the “Wirelaid-copper foil” in the shown stack up. 3 WIRELAID® Design Rules L1 x B1 Dimensions (minimum) F 08 250 x 800 µm2 F 14 Pad size 3.5 x 2.5 mm² 3.5 x 3.0 mm² LB Track width above wire 1.3 mm 1.9 mm A1 Distance of pitch between wires of separate potentials (considering the positioning of the pad) 1.3 mm + Iso distance* 1.9 mm + Iso distance* A2 350 x 1400 µm2 Distance pitch of wires for same potential 1.2 mm 1.8 mm Smax Max. length of wire between welding points 80 mm 100 mm Smin Min. length of wire between welding points 7.5 mm 7.5 mm Isolation distance between wire and inner layer Dependent on the specific stack up of the customer, which we are pleased to create for you. IL *Dependent on the thickness of copper layer according to the current Basic Design Guide of Würth Elektronik L1 LB A2 A1 B1 Smax Smin IL L2 x B2 D Dimensions (minimum) F 08 Pad size for angled tracks 5.4 x 2.8 mm² 6.3 x 3.6 mm² Min. wire separation distance 0.8 mm 0.8 mm 250 x 800 µm2 F 14 350 x 1400 µm2 B2 L2 4 www.we-online.com D WIRELAID® 3D Design Rules Dimensions (minimum) C Distance copper to milled edge F Width of milled slot F = 0.4 x (thickness of PCB –R) + 200 µm K Solder mask clearance in bending area 1.0 mm R Thickness of residual material Thickness of wire + copper + solder mask + 150 µm 0.3 mm Wires need to be arranged at right angles to the bending area The usage of an applicable bending (forming) tool is recommended Bending radius ≥ 0.1 mm Care has to be taken so that the bent parts are secured in the installed application to avoid further movement K R F C 5 Ampacity Copper thickness: 35 µm base copper + copper plating Electric current [A] Wires welded under the external layer Size & number of wires Track width [mm] Copper thickness: 70 µm base copper + copper plating Electric current [A] Size & number of wires Track width [mm] Copper thickness: 35 µm (base copper) Electric current [A] Wires welded under the internal layer Size & number of wires Track width [mm] Copper thickness: 70 µm (base copper) Electric current [A] Size & number of wires Track width [mm] The tables above serve as rough guides as the ampacity is determined and influenced by the layout, stack up, assembled components and other factors. Therefore the build-up and design needs to be evaluated by the product manager for the specific project. 6 www.we-online.com Rise of temperature (ΔT in °C) Any more questions? For higher currents, please contact our product management at [email protected] 7 Investigative procedure for the calculation of the ampacity tables Test set-up FR4 base material thickness: 2.2 – 2.5 mm PCB profile: 115 x 80 mm² Equal copper flooding of 40 % on each layer PCB Wires welded under the external layer Cu Top 35/70/105 µm* Prepreg Cu Layer 2 35/70/105 µm Prepreg Cu Layer 3 35/70/105 µm Prepreg Cu Bottom 35/70/105 µm* Wires welded under the internal layer Cu Top 35/70/105 µm* Prepreg Cu Layer 2 35/70/105 µm Prepreg Cu Layer 3 35/70/105 µm Prepreg Cu Bottom 35/70/105 µm* For the test set-up the PCBs were measured in a temperature-controlled loading gage at a constant environmental temperature of 22 C°. Solder pads were used for the power supply. The different currents are applied for five minutes to stabilise the thermal gradients, after which an infrared image was recorded. *including copper plating of 25 µm www.we-online.com Würth Elektronik GmbH & Co. KG Circuit Board Technology Salzstr. 21 · 74676 Niedernhall · Germany Tel: +49 7940 946-0 Fax: +49 7940 946-550000 [email protected]