Tips for PCB design with copper elements (HSMtec) – Part 1

HSMtec cross section
Cross-section of an HSMtec printed circuit board: Copper profiles reinforce the high-current conductors

When designing HSMtec-PCBs with integrated copper elements, it is generally recommended to design the high-current conductors before the standard layout. The development process of an HSMtec printed circuit board takes place in 10 design steps:

  1. Define mechanical features: Determine the size and contour of the printed circuit board
  2. Place power components: define short and simple paths for the high-current conductor tracks
  3. Define current ratings: e.g. 80 or 110 A
  4. Define ambient conditions: Ambient temperature e.g. 60 °C and maximum temperature difference Delta T of 40 K
  5. Define layer structure and copper layers: It is recommended to work preferentially with ground inner layers and also to flood all free areas on the outer layers with copper
  6. Calculate the required cable cross-sections in relation to the ambient conditions and layer structure.
  7. Routing of the high current conductor paths
    For routing, the following basic rule applies: For each profile width, the trace must be designed at least 1 mm wider all around. Example: An 8 mm copper profile needs at least a 10 mm wide conductor track, 2 times 4 mm profiles parallel next to each other need at least a 12 mm wide conductor track.
  8. Design of the copper profiles e.g. with an auxiliary layer
    The KSG team will be happy to assist you with the selection of copper elements.
  9. Place holes for high current and power components: Through vias, Thermovias – Set microvias in the heat path of the MOSFETs on the copper profiles. Microvias with a diameter of 0.1 mm and a pitch of 0.5 mm are placed in the heat pads of the MOSFETs, which make contact with the underlying copper profile. Place thermovias around the heatpad of the MOSFETs. For example, if the thermovias have a diameter of 0.5 mm, select a grid of 1.0 mm.
  10. Routing of the logic part of the circuit

Steps 1 to 4 are defined by the developer, for steps 5 and 6 KSG offers a high-current calculator or the KSG team will be happy to support you.

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