HSMtec 3D printed circuit board: the self-supporting 3D construction
The HSMtec 3D printed circuit board does not require any flex foil at the bending point. This technique uses copper wires and copper profiles pressed into the FR4 material of the multilayer as bendable material. At the bending edges the FR4 is removed with notch milling. Individual segments with an angle of inclination of up to ±90° can be aligned at these predetermined bending points. The special feature: The copper profiles allow a self-supporting construction, whereby even high currents or heat are conducted over the bending edge. In this way, multidimensional applications can be combined with power electronics over the bending range or with rapid heat spreading in circuit carriers for LEDs.
The design is predestined for one-time bends, e.g. for applications where the flexible area is only bent for the installation of the assembly. The PCB is qualified according to DIN EN 60068-2-14 and JEDEC A 101-A as well as audited for aviation and automotive. Another advantage is that the low moisture absorption eliminates the need for thermal pretreatment during soldering. In addition, all other processes are fully compatible with the standard process.
The possibilities of this 3D structure are demonstrated by eCube – a cube created in a research project led by Continental Automotive. The goal was to develop a three-dimensional cube- or cuboid-shaped PCB based on an existing Continental standard PCB layout for an engine control system. The components were to be mounted on the printed circuit board on a placement line using the existing placement machines. After assembly, the PCB was folded at the defined folding edges and the resulting butt edges were connected electrically and mechanically.
After joining the edges, the cube was aligned on the base plate and assembled both electrically and mechanically. The cube is connected to the motor control motherboard via a ball grid array structure. What at first appears to be a complex task, namely mounting a multi-dimensional printed circuit board construction on the actual printed circuit board of the motor control unit, is, on closer inspection, a technically clever and economical solution. The multidimensional printed circuit board is used to design a module that can be manufactured in different variants but in a standardized way, making use of the available installation space.
Expert tip: The perfect balancing act
Multi-dimensional PCBs add value to the electronic assembly. Although the 3D PCB is more valuable and more expensive to manufacture than a rigid PCB, the system costs of the overall solution are reduced. The three-dimensional printed circuit board is laid out and manufactured as a two-dimensional printed circuit board, and after assembly it is formed into the desired three-dimensional shape. From the point of view of the PCB manufacturer, the focus is on manufacturability and the balancing act between stability, flexibility and accuracy must be achieved. Stability, so that the finished PCB can be assembled, reflowed and tested; flexibility, so that the PCB can be easily and quickly separated from the panel; and accuracy, because too many retaining webs would leave unclean traces.