Simplifying Device Design with PCB Connectors

As medical devices become more complex, designers must use the available spaces within their devices more efficiently. Several PCBs often have to be connected in the tightest of spaces.

Medical technology manufacturers face the challenge of integrating existing functions and adding new functions into designs that users are already comfortable with. In general, the PCB connectors have to meet numerous additional requirements that are not necessarily specific to the installation space. New technology for board-to-board connectors can simplify this integration.

The complexity and integration density of modern applications do not stop at medical devices. On the contrary, the integration density and the number of functions in medical devices will continue to increase. For example, the U.S. Centers for Disease Control has launched a “Global Digital Health Strategy,” which aims to improve the availability and use of data in health systems. The GDHS aligns with the CDC Data Modernization Initiative. Today’s devices are already very complex, but increasing digitalization will require even more integration with communication, function extensions, and other advanced features.

Board-to-board connectors commonly connect the PCBs. Depending on the environment where they are used, medical devices need to meet a large number of requirements. These requirements might relate to the electrical and mechanical connection, compliance with EMC, and the materials used in the connectors. The different locations and environments of use (ambulance, air rescue, hospital, MRT, CT, ultrasound, etc.) define these diverse requirements on the devices themselves and their connectors.

Vibration stability, impact resistance, and long-term contact reliability in the face of micromovements of the board-to-board connectors used in the devices are of considerable importance. A robust, self-adjusting system during device assembly is also a crucial economic factor. During assembly, neither damage to the contacts nor mismatching should be possible.

Solutions for Simplifying Device Design

Tolerance stack-ups are a particular challenge for all developers during the mechanical designs of their devices. Board-to-board connectors can also affect the transmission quality of the signals and the reliability of the power transmission.

However, the seamless transmission of data, signals, and power is essential. At the same time, most applications will have other requirements — for example, robustness, variability, and the smallest possible size. In addition, there is also the option of EMC shielding of the connection and the use of non-magnetic materials.

A board-to-board connector series can create robust, flexible, and extremely reliable PCB connections. With a compact pitch of 0.8 mm and a choice of either a mezzanine or angled arrangement, this connector style can enable data transmission rates of up to 52 Gbps with a specified 500 mating cycles, which can indicate the surface quality. The connector design ensures contact protection and prevents mismatching (see Figure 1).

The extended temperature range of –55° to +125 °C can ensure the connector system’s performance capability. Comprehensive test reports covering harmful gas and shock tests, among others, are available.

The hermaphroditic double contacts set this connector type apart from more traditional connectors. With conventional contact technologies, such as double contacts and single beam (see Figures 2a and 2b), the knife and spring contact sides are gender-separated. This double contact system has a knife and a spring contact on both sides, combining the advantages of conventional contact geometries. However, the connectors themselves consist of a male and female side. Thus, the new style does not suffer from the well-known technical compromises of conventional hermaphroditic connectors (see Figure 3).

The hermaphroditic double contact system ensures reliable contact in a wide range of situations. Mating position and angle variances are compensated for with tolerances of up to ±0.7 mm or 5° in all directions. When plugged in, there is a tolerance compensation of at least ±0.3 mm in the longitudinal and transversal (x-y) direction — a quasi-floating contact.

This means the system can enable multiple plug connections between the circuit boards. In the plug-in direction, the tolerance window is even larger: In addition to the qualified mating area, the so-called wiping length of 1.5 mm means that the connector also has an additional contact overlap of around 0.8 mm. This characteristic makes it possible to realize PCB clearances flexibly and seamlessly in the range of 6–21 mm in a mezzanine arrangement. The angled versions also offer various installation options, such as horizontal and vertical connections.

Numbers of positions from 12- to 80-position are available in a space-saving double-row arrangement in the portfolio. Due to the proven possibility of multiple use of several connectors on a PCB, it is possible to realize higher numbers of contacts between two PCBs — and it’s all safe, electrically reliable, pluggable, and detachable.

Data, Signals, and Power

All connectors are available both as shielded and unshielded versions. The shield and armature metals used are made of non-magnetic copper alloys, which makes it possible to use them in a strongly magnetizing environment, such as MRT applications.

Well-placed pin assignment allows for 360° of shielding around the connector, protecting the signals from external interference. In the same way, outgoing interference, which can be caused by fast signals within the board-to-board connector, is largely excluded. This ensures protected and EMC-stable data and signal transmission. Many medical devices, such as ultrasound equipment, require suitable shielding to enable interference-free (noise-free/EMC/RFI) image generation (see Figure 4).

If the connectors also need to transmit power, there are two options. First, the signal contacts can be subjected to a specified current of 1.7 A per contact when they are fed with full current. The other option is to use the galvanically isolated shields for current transmission. The hybrid connector can transmit both power and high-speed signals. This combination saves space on the PCB and makes the layout work significantly easier (see Figure 5).

The data required to design the medical device (M-CAD and E-CAD files) and signal simulations (such as 2D, 3D, derating, S-parameters, touchstone, customer-specific simulations, etc.) can be processed using the available in-house measurement and simulation technology. It can also be called up on the homepage. This simplification will have a large impact on the acceleration of medical devices.

Conclusion

The versatile characteristics of the double contact connector system make it possible to achieve a high degree of mechanical tolerance compensation, data integrity, and EMC stability, and to transmit power within the application. In almost all areas of medical technology, such as imaging diagnostics, patient monitoring, defibrillators, therapy devices and robotics, infusion technology, and related applications, the connector system simplifies the design of medical devices significantly.

It can be used as a classic, high-speed connector, a hybrid connector, and a docking connector for modular systems. The versatility of this modern board-to-board connector family can make a significant difference in state-of-the-art medical devices.

This article was written by Dipl.-Ing. Detlef E. Preissler, Senior Specialist Product Marketing Board-to-Board and PCB Connectors, Phoenix Contact GmbH & Co. KG, Blomberg, Germany. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it. or visit here .

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