White Paper: Board-to-Board connector for Industrial Sensors and Camera Systems
Faster, smaller, more robust: When used in industrial sensors and camera systems, connector must meet an ever-increasing number of requirements. The trend is toward modularization. With the help of board-to-board connectors, printed circuit boards can be flexibly combined with one another, thereby significantly defining the sensor’s functionality. In the age of Industry 4.0, connectors must not only become smaller and more powerful—in addition to miniaturization and high speed, use in industrial environments often requires extreme ruggedness. This guide is intended to help you find the right connector for your machine vision application.
Three requirements take center stage in the development of modern sensors and camera systems for industrial applications: high-speed data transmission, miniaturization, and ruggedness. These requirements can rarely be considered in isolation from one another—however, depending on your priorities, the optimal connector can be found for your application.
High-speed data transfer
In the age of big data, IoT, and IIoT, smart sensors and cameras in industrial environments also require secure, high-speed data transmission. Connectors (connector) for high-speed applications should feature a correspondingly high-performance contact design. Since a connector’s geometry inherently poses a certain risk of fluctuations in the impedance profile, special attention must be paid during the development of high-speed connectors to optimizing the contact design for impedance control. In this context, it is important to minimize changes in cross-sectional area within the connector, if possible, as these result in impedance fluctuations, which in turn lead to losses in signal transmission.
In the case of miniaturized assemblies, connectors (connector) should also feature electromagnetic shielding, since high-frequency signals in particular are especially susceptible to unwanted electromagnetic effects. Here, even a small pulse can be enough to distort the useful signal, so that the receiver can no longer unambiguously interpret the digital states.
A connector (connector) can act as both an electromagnetic sink and a source; that is, it can be subject to interference from other components in the assembly while also exerting its own electromagnetic influence on surrounding components. The coupling inductance (mutual inductance) LK, measured in picohenry (pH), describes the connector’s behavior in both roles—as a source and as a sink. A simple test setup helps users determine which connector and which pinout is necessary or optimal for their specific application. To do this, the useful signal must be disturbed using a burst generator, and the maximum permissible mutual inductance must be measured. If the induced voltage (Uind), the generator voltage (UGen), and the generator constant (kGen) are known, the specific, maximum permissible mutual inductance (L) for each application can be determined using the following formula:
L = Uind / (UGen * kGen)
mutual inductance also helps the user select the appropriate connector in terms of its electromagnetic compatibility. This also allows for the avoidance of costly and time-consuming trial-and-error testing in the EMC-Labor.
Furthermore, it is possible to reduce the mutual inductance of a connector by using shielding. Here is an application example: For an HDMI signal, a case-specific maximum mutual inductance of 47 pH was determined at a voltage of 4.4 kV. If the value exceeds this, the signal can no longer be transmitted without interference. The figure below shows that the mutual inductance was significantly reduced through the use of a shielding concept.
A connector (connector) can act as both an electromagnetic sink and a source; that is, it can be subject to interference from other components in the assembly while also exerting its own electromagnetic influence on surrounding components. The coupling inductance (mutual inductance) LK, measured in picohenry (pH), describes the connector’s behavior in both roles—as a source and as a sink. A simple test setup helps users determine which connector and which pinout is necessary or optimal for their specific application. To do this, the useful signal must be disturbed using a burst generator, and the maximum permissible mutual inductance must be measured. If the induced voltage (Uind), the generator voltage (UGen), and the generator constant (kGen) are known, the specific, maximum permissible mutual inductance (L) for each application can be determined using the following formula:
L = Uind / (UGen * kGen)
mutual inductance also helps the user select the appropriate connector in terms of its electromagnetic compatibility. This also allows for the avoidance of costly and time-consuming trial-and-error testing in the EMC-Labor.
Furthermore, it is possible to reduce the mutual inductance of a connector by using shielding. Here is an application example: For an HDMI signal, a case-specific maximum mutual inductance of 47 pH was determined at a voltage of 4.4 kV. If the value exceeds this, the signal can no longer be transmitted without interference. The figure below shows that the mutual inductance was significantly reduced through the use of a shielding concept.
In this test, both the board locks and the outer contacts were grounded for both the unshielded and shielded versions, while a signal was applied via a pair of contacts. The measured coupling inductance values can be demonstrated using color gradients of the electric and magnetic fields. The simulation using an unshielded connector showed that a mutual inductance of up to 196 pH is present in this case. Given the determined threshold value of 47 pH, undisturbed signal transmission would no longer be guaranteed. With the shielded connector, on the other hand, the coupling inductance values range from 1 to 4 pH. The shielding thus reduced these values by a factor of approximately 50, thereby ensuring interference-free transmission. With a higher number of positions, a reduction by a factor of 100 to 200 is even possible.
For the user, the shielding offers two key benefits: First, the connector acts as less of a source of interference; second, the shielding makes it a less effective sink for interference signals. By using shielded connectors, they can now also be positioned closer to sources and sinks of interference on the printed circuit board. Additionally, this enables a higher performance class to be achieved in the required burst and surge tests of the electrical device.
For the user, the shielding offers two key benefits: First, the connector acts as less of a source of interference; second, the shielding makes it a less effective sink for interference signals. By using shielded connectors, they can now also be positioned closer to sources and sinks of interference on the printed circuit board. Additionally, this enables a higher performance class to be achieved in the required burst and surge tests of the electrical device.
miniaturization
Despite increasing functional integration, the size of sensors and camera systems must not increase. In most cases, industrial automation even demands continuous miniaturization to enable the construction of increasingly compact machines. Similarly, the trend toward modular sensor and camera designs requires the use of correspondingly miniaturized connector. Over the past decades, connector have therefore been reduced to a fraction of their original size while maintaining nearly identical performance.
Surface-mount technology is ideal for applications with particularly tight installation spaces. It is especially space-saving because it allows for double-sided PCB assembly as well as small pitch. With the “press-fit technology” (press-fit), for example, a tight pitch of only 0.5 mm would not be feasible due to the physical forces acting during the press-fit process—nor would double-sided PCB assembly. In the case of miniaturized applications, there is also another important criterion to consider when selecting the right connector: In such cases, sensitive components within an assembly are often located very close to one another. This creates an increased risk of mutual electromagnetic interference between the components. Of course, data transmission in your application must under no circumstances be disrupted, distorted, or even prevented. For this reason, electromagnetic (EM) protection is becoming increasingly important. To avoid signal interference, it is therefore recommended—as with high-speed connector—to choose a shielded connector in this case as well.
Robustness
Sensors and camera systems used in close proximity to machinery are particularly exposed to harsh environmental conditions. To protect the electronics from these external influences, the entire assembly can be encapsulated. However, this requires a connection solution that is also compatible with the encapsulation process. Conventional connector are at a clear disadvantage here because the vulnerable mating area must be protected from the potting compound. The spring-blade contact technology used here would not meet the required IP degree of protection for these materials.
When selecting the right connector, it is therefore important to choose a one-piece connection solution—that is, a connector that does not require the conventional mating area. This allows the potting compound to provide a durable and robust connection, while ensuring it does not penetrate the contact area.
If electronic components need to be tested for robustness, this can be done through laboratory tests. In these tests, the standardized shock profile must correspond to the target condition (control), i.e., an acceleration of 50 g with a tolerance of 20 percent (high abort and low abort). According to DIN EN 60068-2-27, a contact interruption (discontinuity) of ≤ 1 µs is permissible.
If electronic components need to be tested for robustness, this can be done through laboratory tests. In these tests, the standardized shock profile must correspond to the target condition (control), i.e., an acceleration of 50 g with a tolerance of 20 percent (high abort and low abort). According to DIN EN 60068-2-27, a contact interruption (discontinuity) of ≤ 1 µs is permissible.
If the connector in your application is exposed to extreme external environmental influences such as vibration, shock, moisture, dirt, extreme temperatures, or temperature fluctuations, extreme robustness is also required. Encapsulating potting your assembly can help, but it is advisable not to rely solely on this method. Instead, a combination of potting and press-fit technology is recommended. The latter has already proven itself billions of times over and is considered the most robust and reliable connection method—even under adverse conditions. In press-fit technology, the connector pin is pressed into a through-hole in the printed circuit board, thereby creating both an electrical and a mechanical connection between the connector and the printed circuit board. At the same time, this approach can yield cost savings of up to 50 percent by eliminating time-consuming soldering work and expensive cable solutions. Without the vulnerable mating area, a connector using the press-fit technology can even withstand shock loads of 50 to 200 g without discontinuity.
When all-rounders are in demand
In theory, these requirements—high-speed data transmission, miniaturization, and robustness—can be viewed as relatively distinct from one another. As a user, however, you will certainly find that the connector you need rarely has to meet just one of these requirements. For this reason, many connector meet several of these criteria to varying degrees. In some cases, it’s also worth taking a look at the “all-rounders” among connectors. For example, if multiple connector are to be used simultaneously, it is advisable to choose a product family that offers high scalability. This helps avoid time-consuming and costly approval cycles while ensuring that all products within a connector family are compatible with one another—regardless of whether they are shielded, unshielded, straight, or angle.
Any questions?
As experts in PCB connector and contacting, we are happy to share our knowledge, for example, in webinars tailored to your needs:
webinar.ept-group.de
Or contact us directly with any questions you may have regarding connector!
ept GmbH
Bergwerkstr. 50
86971 Peiting, GERMANY
Phone +49 (0) 8861 2501 0
Fax +49 (0) 8861 2501 700
www.ept.de
sales@ept.de
webinar.ept-group.de
Or contact us directly with any questions you may have regarding connector!
ept GmbH
Bergwerkstr. 50
86971 Peiting, GERMANY
Phone +49 (0) 8861 2501 0
Fax +49 (0) 8861 2501 700
www.ept.de
sales@ept.de