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We understand from customers that they’d like a flexible board in order to avoid a connector (and sometimes a cable) when fitting PCBs into a small enclosure. This makes sense since avoiding such connections is a good way to reduce costs and avoid signal integrity issues caused by impedance mismatches at the interfaces. Flex to install PCBs in enclosures, but how?
The first question customers ask us is if we offer a pooling service for flexible PCBs. Whilst we would be able to manufacture them, setting it up as a pooling service would not be cost-effective, for now. This is because the traditional flexible PCB market is for a few customers with high-volume requirements. That’s obviously not the kind of market suitable for a pooling service where you need many customers with low-volume requirements.
However, if the bending is done only once when assembling the product, a bendable PCB may be the right solution rather than a flexible PCB! With this in mind, we investigated how we could use standard FR-4 to create a buildup that met the requirements of our customers, and that can become a workable pooling service and from this our SEMI-FLEX pool service was born.
We offer a bendable PCB that is typically four layers and made entirely of FR-4 which can be bended in multiple directions. But unlike conventional flex-rigid PCBs, the flexing element is a thin FR-4 core rather than polyimide.
The bendable FR-4 core has 2 layers of copper that are specially treated so that they can bend without cracking and will bend a limited number of times (typically 5 times) at a minimum radius and to any angle thus making it suitable for a flex to install application, see the Technical specification.
Eurocircuits’ 4-layer SEMI-FLEX PCBs use a 100 micron central core for the flex portion, with 35 micron high-ductility copper foil on each side. The stack is then built up on each side with a 510 micron FR-4 core and two layers of no-flow prepreg. Our buildup is symmetrical and stable and can be bent in any direction.