Electronics Protection Online - A Complete Guide to Enclosures and Protection

Electronics Protection

Protecting Electronics with Connector Innovations
Keith Teichmann, Global Marketing Manager
ITT Interconnect Solutions

Regardless of the type of electronic device, proper protection must be applied to the vital components in order to achieve optimum performance. However, devices that are employed in critical applications, such as medical, military and aerospace industries, must meet more stringent reliability, durability and performance specifications than their consumer counterparts. A fundamental design consideration is to implement protection within the interconnect system. Contact systems that can protect from misalignment, EMI, surge protection and harsh environment conditions ensure proper function and significantly reduce failure rates.

Contact Systems
An ideal contact system is robust, reliable and flexible across a variety of specifications. Connector manufacturers have recently made design innovations to traditional male-to-female contact systems, integrating protective elements and design flexibility. For example, one design employs an internal clip mechanism that provides proper mating in a spring probe pin/pad contact system. This design also allows enough space for individual contact pads that provide an effective, ultra-reliable electrical connection. Misalignment in the connection is often the cause of device failure, using contact systems such as the one described above can resolve these issues. The spring probe system has a significantly longer life cycle than traditional pin-and-socket designs due to the fragility of pins. Using the spring probe systems can increase a connector’s cycle life by more than 70 percent.

In addition to providing solutions to misalignment, spring probe pin/pad contact systems can generate more force than a pin-and-socket design. Spring probe systems possess a pre-loaded contact that immediately generates force. This results in a much higher force at deflection; and, because alignment is not as critical in this design, the contact system is able to generate a significant amount of Hertzian force while maintaining signal integrity.

Contact systems in medical, military, and aerospace equipment must achieve a high degree of reliability for obvious reasons. Connector manufacturers are designing “hyperboloid” contact systems in order to answer this call for highly reliable components. Hyperboloid contact systems include multiple points of contact, positive wiping action, and a closed entry to guide the mating pin for thousands of cycles without degrading the signal integrity. For example, portable medical and military equipment employ hyperboloid contact systems due to their extremely low insertion force and resistance to shock and vibration.

EMI and Surge Protection
EMI and surge protection is most effective when it is implemented at the interface of the system within the connector. Because of the labor-intensive and costly traditional methods of EMI and surge protection - such as physically attaching a device to the side of each contact within the connector and grounding it to the connector shell; or attaching a pre-tested JANTX certified device with leads to the contact via circuit boards or other similar techniques, with the other end being connected to the shell - connector manufacturers are developing new solutions for shielding and filtering inside the connectors themselves to protect signal integrity.

For applications that require the utmost protection, such as military and aerospace systems, fragile ceramic planar array block capacitors are being replaced with state-of-the-art flexible circuits. To increase durability and reliability in harsh environments, these circuits are comprised of individual chip capacitors that are surface-mounted on a pad adjacent to the feed-through contact. These feed-through contacts are not soldered into the capacitor to relieve stress of certain points that were vulnerable to thermal shock and vibration up to 1,000 cycles. The Chip-on-Flex (CoF) filter connectors utilize off-the-shelf chip capacitors mounted on the flex circuits for filtering. This type of filter connector has standard filtering capabilities that include filtering at the face of system boxes, plane barriers in connectors, and high-frequency noise.

Transient voltage surge protection (TVSS) can be accomplished by using the CoF technology to surface-mount TVSS devices on a flex layers or add a separate layer with the chips on it. The chips mounted on the flex circuit in the filter connector provide a number of benefits in addition to the traditional surge, EMI and EMP protection, and take up less board space. The filter connector has a ground plane, so it provides further protection by acting as a shield at the system or box level. Vacant board space can easily sustain a ground plane if one is not available.

TVSS for interconnect systems in airplanes comes in the form of a device called a transorb. Traditionally, a transorb must be specified to voltage; and, in order to get true protection, it must be physically attached to every contact in the interface connector. This time-consuming method of protection prompted a search for a more cost-effective and less labor-intensive solution. Incorporating TVSS with CoF technology in the interconnect system is the most practical answer. The flex circuit design provides the necessary platform to surface mount TVSS devices that are strong enough to withstand a powerful surge.

EMI and surge protection is also vital in medical equipment. Electromagnetic inference can distort images in X-ray machines and ultrasound equipment, while signal noise can affect the operation of pacemakers or other implantable devices. Connector technologies used in military and aerospace applications can be applied to meet EMI/RFI requirements that are needed for diagnostic equipment.

Insert and Filter Innovations
Enhancing the materials surrounding contacts in connectors can significantly increase the degree of protection for the end product. A standard circular multi-pin connector with positive locking and quick disconnect features that utilize a plastic or rubber insert is a perfect example of this. This type of insert makes the component well suited for entertainment and commercial applications. However, these materials do not have the ability to withstand temperatures reaching 165°C. An alternative to rubber and plastic inserts is to employ metal hermetic seals to provide a durable insert for harsher environments.

Other harsh environments require a ceramic insert, which is fire resistant. Introducing ceramic can increase the connector’s high-temperature capabilities from 165°C to more than 700°C. By the same token, high temperature silicon grommets seal the connector wires against humidity and water penetration. One particular high-temperature connector, shown below, consists of machined copper alloy-plated contacts with a metal retention clip, a machined stainless steel shell and ceramic inserts.

Applications such as mass transit, railway systems, as well as geophysical, nuclear and military installations require connectors that can achieve temperatures in the 700-degree range. Other applications, such as medical electronics must apply the same degree of reliability and ability to withstand harsh environments.

Materials
The key to materials utilized in connectors for portable medical equipment is their robustness. Aluminum or composite alloy shells with copper alloy or thermocouple contact materials are employed for high reliability. Copper alloy plated contacts with metal retention clips and thermoplastic inserts pave the way for a robust connection to meet the environmental requirements of portable medical devices.

With the requirement for high voltage and portability in medical equipment, connector manufacturers are keeping pace with innovative connector configurations and contact technologies. Using hyperboloid contact designs in conjunction with circular bayonet style connectors with robust alloys materials are just a few of the ideal solutions available today.

The environment in which an end product is used is a significant factor in influencing the design of its contact system. Interconnect innovations have enabled EMI and surge protection within the contact system via inserts and filters to provide the necessary degree of protection. Whether it is used in an airplane, pacemaker or MP3 player, in order for the end product to function at the highest level, every component within that device must be protected. As explored, CoF technology, TVSS layers and materials are some of the most effective methods in which to provide this protection.

For more information contact www.ittcannon.com