How Board-to-Board Connectors Achieve
Durability
White Paper: How Board-to-Board Connectors Achieve Durability and What Factors Affect the Connector
Whether in aerospace, industrial automation, transportation, or healthcare, board-to-board connectors must always ensure reliable signal transmission and must not fail under any circumstances. At the same time, they are exposed to a range of environmental stresses: Mechanical stresses such as shock, vibration, and oscillations jeopardize the stability of data transmission, as do thermal and chemical environmental influences caused by extreme temperatures, significant temperature fluctuations, harmful gases, moisture, and dirt. Manufacturers of high-quality PCB connectors therefore employ a wide range of measures to protect their board-to-board connectors against these stresses.
Ruggedness of board-to-board connectors despite miniaturization
Modern electrical engineering is subject to one trend more than ever: miniaturization. Assemblies and their components must not only become increasingly powerful, but also increasingly smaller. Yet they are often used in harsh real-world conditions. Components, including connectors, are therefore becoming increasingly delicate while withstanding the same level of stress. However, a high-quality connector not only withstands this stress just as well as its older, larger counterpart, but even better. This is due to advancements in material composition and product design, such as in the geometry of the insulating body.
A wide variety of factors influence the robustness of a board-to-board connector:
A wide variety of factors influence the robustness of a board-to-board connector:
- Surface
- Contact design
- Contact system
- Connection technology
- Insulator design
- Tolerance range
Surface as an influencing factor
One contributing factor is the contact surface. This plays a key role in determining the connector’s service life, which is typically measured in mating cycles. During field use, the connector is subjected to certain micro-movements. These lead to surface abrasion and, consequently, to oxidation. The result is increased contact resistance and, consequently, poorer signal transmission quality.
A high-quality, durable contact coating is therefore crucial for minimizing surface abrasion.
Read our free white paper to learn what to look for when selecting a contact surface.
A high-quality, durable contact coating is therefore crucial for minimizing surface abrasion.
Read our free white paper to learn what to look for when selecting a contact surface.
Contact design as an influencing factor
The contacts of a printed circuit board connector are stamped or turned. However, stamping creates an uneven, sharp-edged surface on the underside of the stamped strip that is visible under a microscope. Conventional systems make contact along this stamped edge, which results in increased surface abrasion and, consequently, higher contact resistance.
Free white paper on connector robustness
In this free white paper, you will learn how to minimize contact resistance by selecting the optimal contact design. We also explain, using various influencing factors, how board-to-board connectors achieve robust performance and what specific parameters must be considered.
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Contact system as an influencing factor
Traditional two-part connectors feature a blade contact and a spring contact. However, in the event of a strong shock, the blade strip can lift away from the spring strip. To prevent such a contact interruption, a double-sided spring strip can be used to ensure redundancy and thus contact reliability, as the second spring ensures that signal transmission is maintained at all times via at least one contact point.
Even more robust, however, are connectors with a so-called “gender-neutral” contact system. The distinctive feature here is the identical contact geometries of the connector halves.
Even more robust, however, are connectors with a so-called “gender-neutral” contact system. The distinctive feature here is the identical contact geometries of the connector halves.
Connection technology as a contributing factor
There are various ways to mount connectors on printed circuit boards.
One of these is the press-fit technique mentioned earlier. Its goal is to achieve the highest possible retention forces between the connector and the PCB while using the lowest possible press-fit force. These holding forces define the mechanical connection, which must withstand shock and vibration.
However, press-fit technology is not always suitable, for example when PCBs are populated on both sides or when the minimum distance to components in the direction of force cannot be maintained. Another option for creating a reliable and durable connection between the connector and the PCB is surface-mount technology (SMT). In this process, the connectors are soldered to defined connection areas on the PCB—the solder pads—using solder paste.
One of these is the press-fit technique mentioned earlier. Its goal is to achieve the highest possible retention forces between the connector and the PCB while using the lowest possible press-fit force. These holding forces define the mechanical connection, which must withstand shock and vibration.
However, press-fit technology is not always suitable, for example when PCBs are populated on both sides or when the minimum distance to components in the direction of force cannot be maintained. Another option for creating a reliable and durable connection between the connector and the PCB is surface-mount technology (SMT). In this process, the connectors are soldered to defined connection areas on the PCB—the solder pads—using solder paste.
Design of the insulating body as an influencing factor
The insulation body geometry of a board-to-board connector also helps protect the contacts from damage during operation or installation. It should be designed so that the vulnerable contacts are shielded inside the connector.
Insertion chamfers further prevent damage during assembly by compensating for any misalignment of the circuit boards in any direction when mating. An additional catch area enables the two connector halves to be mated without damage even in the event of center or angular misalignment.
Insertion chamfers further prevent damage during assembly by compensating for any misalignment of the circuit boards in any direction when mating. An additional catch area enables the two connector halves to be mated without damage even in the event of center or angular misalignment.
Influencing factor Tolerance range
The tolerance range of a connector plays a crucial role in assessing its robustness. If the connector cannot compensate for given tolerances, mechanical movements will lead to wear or even damage to the connection.
In the field, for example, stresses arise not only in the x and y directions but also in the z direction. This raises the question of a connector’s mating reliability. It describes the overlap area between the male and female contacts, thereby accommodating not only different PCB spacing but also—depending on the size of this area—varying tolerance ranges.
Read the free white paper to learn what other factors influence the tolerance range and how to compensate for them. Request
white paper »
In the field, for example, stresses arise not only in the x and y directions but also in the z direction. This raises the question of a connector’s mating reliability. It describes the overlap area between the male and female contacts, thereby accommodating not only different PCB spacing but also—depending on the size of this area—varying tolerance ranges.
Read the free white paper to learn what other factors influence the tolerance range and how to compensate for them. Request
white paper »
Testing procedure
There are various testing methods available to thoroughly evaluate the durability characteristics of board-to-board connectors. These methods involve measuring variables such as dielectric strength and contact resistance both before and after a stress test, as well as visually inspecting the condition of the contacts. For example, the effects of 500 mating cycles on dielectric strength can be assessed, or a climatic test can determine whether several hours at -55°C followed by 125°C have a negative impact on the contact resistance of the connector. In the temperature shock test, the connector must withstand rapid cycling between these extreme temperatures 100 times for 30 minutes each. Furthermore, the center and angular misalignment during mating, as well as the tolerance range in the mated state, should not only be verified theoretically on the CAD model but also extensively tested in practice, with the load-bearing capacity confirmed empirically. It is equally important that various tests critical to the contact surface be performed in combination to simulate real-world conditions. For example, mating cycle and corrosive gas tests can be conducted in combination to ensure that the connector’s performance in terms of contact resistance and dielectric strength has not deteriorated and that the contacts have not been damaged.
Free webinar on the reliability of board-to-board connectors
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Then schedule a complimentary webinar with us. Request
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Your design – your choice
Depending on the application requirements, there are various robustness criteria that a board-to-board connector must meet. For example, does it need to compensate for high tolerances? Is it exposed to high shock loads or vibrations? Is it used in environments subject to extreme heat or cold? Or does the connection solution need to be protected against moisture, corrosive gases, or dirt? By addressing these factors during the selection process, engineers can ensure that the chosen connector is optimally equipped for its intended field application.
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