Eurocircuits, one of Europe’s largest fabricators of prototype and small series PCBs, have launched SEMI-FLEX pool, the first cost-cutting order-pooling service for flex-to-install PCBs.
Many flex-rigid circuits are not required for continuous flexing but to fit boards into complex spaces without using connectors and cables. The flex element is polyimide, a material expensive in itself and needing special processing. SEMI-FLEX offers a more cost-effective solution.
Conventional flex-rigid PCBs use the polyimide layer to flex between the rigid FR4 areas. SEMI-FLEX PCBs are made completely of FR4, using a thin FR4 section which can be bent for a limited number of times at a controlled radius. This is an ideal solution where two or more rigid areas of the PCB need to be installed at an angle to each other but continual flexing is not required. Designing a single SEMI-FLEX PCB eliminates the need for cables and connectors. This saves space on the PCB. It lowers costs, cuts design, procurement and assembly times, and increases product reliability by reducing the number of solder joints.
Eurocircuits have chosen a 4 layer configuration. The flex area is part of a 100 micron inner core with 35 microns of high-ductility copper on each side. The alternative technology is to depth-mill through the PCB to leave a thin section on an outer layer as the flex area. Eurocircuits have opted for the inner core solution, even though it is more complex to manufacture. It offers a precise thickness in the flex area as well as a symmetrical build and so a more stable PCB. For the designer it makes it much easier to design a triple configuration with an up and a down bend or a final Z-installation.
