Rigid-flex PC Board Design Resolves Wearable Medical Product Problems

The vast majority of circuit cards in the present day are basically inflexible plates for connecting circuitry. Yet, that is changing fast; the need for flex PCBs (or flexible circuits) is promptly escalating in large part because of the booming wearable product market. Perhaps the most significant segment of that market is the medical industry in which wearable gadgets will be helpful to accumulate all types of bodily details for examination and study, as well as individual health use. Presently wearables can be purchased to watch heart rate, blood pressure, glucose, ECG, muscle movement, and a lot more.


Those wearable devices deliver many challenges for circuit board designers that rigid boards do not. Here are several of such problems along with what designers can do to help remedy them.

3D Design

While every PCB board is actually three-dimensional, flexible circuits enable the entire assy to be bent and folded to conform to the package that the merchandise uses up. The flex circuitry is collapsed to ensure the rigid circuit cards fit into the item package, occupying space.
There are lots more to the design, so the increased challenges, than only connecting the rigid boards. Bends ought to be very well designed so boards align where they are intended to mount, while not placing force on the connection points. Until recently, engineers actually used “paper doll” models to emulate the circuit card assembly. At this point, design tools are available that offer 3D modelling of the rigid-flex assembly, helping more rapidly design and considerably greater accuracy.

Small Items and Condensed Circuitry

Obviously, wearable items should be small and highly discreet. Not that long ago, a medical “wearable” for instance a Holter heartrate monitor contained a pretty big external device with a neck strap or perhaps belt mount. The recent wearables are tiny and attach straight away to the sufferer with no or very few external wires. They obtain various info and are able to even process a few analyses.

An inconspicuous device affixing right to the sufferer requires flex circuitry and incredibly compacted layouts. Also, the board shapes are generally circular or even more unconventional shapes, requiring wise placement and routing. For such tiny and dense boards, a Electronic Circuit Board tool which is designed for rigid-flex designs helps to make addressing odd shapes easier.

Stackup Design is vital

The stackup – the map of the circuit board layers – is significant if you use rigid-flex techniques. Ideally, your PCB design software has the ability to design your stackup including both the rigid and flexible parts of the assembly. As mentioned earlier, the layout of the bending area needs to be designed to lessen the pressures on the traces and pads.
One of the greatest challenges with rigid-flex designs is qualifying multiple producers. After the design is complete, all aspects of the design should be communicated to the board fabricator so it will be properly manufactured. Nevertheless, the best practice is to choose one or more producers at the beginning of the design and collaborate with them to ensure that your design agrees with their manufacture requirements as the design goes forward. Collaborating with manufacturers is made easier by utilizing standards. In this instance, IPC-2223 is the vehicle for making contact with your fabricators.

The moment the design is done, the data package must be assembled to hand-off to be manufactured. Though Gerber is still utilized for standard PCBs in certain firms, on the subject of the difficulties of rigid-flex, it is strongly suggested by both PCB program suppliers together with fabricators that a more intelligent data exchange format be utilized. The 2 most popular intelligent formats are ODG++ (version 7 or later) and also IPC-2581, each of which certainly stipulate layer requirements.


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