Standards, Materials, and Testing for Four Types of Resistance

By Contributed Article | May 30, 2023

Heavy-duty and safety-critical applications and their interconnect systems must be designed to resist mechanical stress and environmental conditions without degrading power, signal, or data transmission. Four tests help ensure high reliability.

Ruggedization methods and processes apply to the entire design, engineering, and manufacturing cycle in the creation of high-performance connectivity solutions. From choosing high-quality materials for housing, coating, plating, insulating, and sealing to protecting the insulation and conductor core against environmental challenges and chemical deterioration, material choices for connectors, and overmolding or jacketing for cables, helps maintain the integrity of the connection under extreme conditions, including rugged operating environments, sterilization processes, or mishandling.

The table below shows key factors that should be considered to enhance ruggedness, ensure a device’s reliable operation, and increase product life cycles to achieve less downtime and longer maintenance intervals.

Design engineers should consider four main types of resistance when working on interconnect solutions for extreme operating conditions: 1) vibration and shock, 2) extreme temperatures, 3) corrosion and chemicals, and 4) radiation.

Vibration and shock resistance

The ability to withstand dynamic stress exerted by vibration, drop, and impact is a key requirement for rugged interconnect solutions. These components must be able to perform, despite rough handling, transportation, and fluctuating conditions in the field.

Extremely rugged connectivity solutions are tested in compliance with the MIL-STD-202-214 Random Vibration testing standard (Military Standard 202, Method 214 and Condition I), which determines the ability of component parts to withstand the dynamic stress exerted by random vibration applied between upper and lower frequency limits to simulate the vibration experienced in various service field environments.

Mounted onto vibration testing equipment, the locking and contacts specifications (or functionalities) of a connector pair is thoroughly verified. Electrical signals are monitored to ensure that no micro-cuts smaller than one micro-second occur.

Monitoring of electrical signals ensures that interconnect solutions can withstand shocks of high G amplitude, in compliance with MIL-STD-202 Method 213 and EIA-364-27.

Drop resistance tests measure the mechanical deformation that could impact the connection’s functioning and performance following drops or bump shocks from different heights.

The most rugged connectors designed by Fischer Connectors, the Fischer UltiMate Series, can withstand random vibration of up to 37.80 Grms and shocks of up to 300 G amplitude (half sine pulse of 3 ms, no discontinuity > 1 μs).

Fischer MiniMax Series.

Data transmission must remain stable even when there are vibrations. ME-Meßsysteme’s six independent strain gauge sensors rely on the ultra-miniature, vibration-resistant Fischer MiniMax Series.

Extreme temperature resistance

High-end solutions may be tested for compliance with the U.S. Military Standard 810, Methods 501.6 (high temperature) and 502.6 (low temperature). This standard emphasizes tailoring an equipment’s environmental design and test limits to the conditions it will experience throughout its service life and establishing chamber test methods that replicate the effects of environments on the equipment rather than imitating the environments themselves. Although prepared specifically for military applications, the standard is often used for commercial products as well as medical equipment that undergoes sterilization processes.

Standardized connectivity products that operate within the temperature range of -55 °C to +135 °C are available. Cabled connectors overmolded with TPU material withstand temperatures ranging from -40 °C to +125 °C, whereas soft caps resist a temperature of +85 °C.

Tailored solutions can be designed to reach much higher or lower temperatures for dedicated applications. For example, IP68/69 sealed and hermetic chromium-plated brass connectors can resist chemicals and extreme temperatures ranging from -100 °C to +20 0°C. The premium materials used in such connectors also allow them to withstand most sterilization methods used in medical applications, such as steam autoclaving per IEC 60601-1.

Fischer Core Series

Sterile or aseptic connectors and cable assemblies must be appropriately sealed to withstand ingress from steam saturated with water under at least 15 psi of pressure during multiple autoclave sterilization cycles (up to 1,000 cycles) that usually last 30 minutes. The World Health Organization recommends that hospital instruments and all equipment in the hospital rooms should be saturated in an autoclave at 121 °C (250 °F) for 30 minutes or 134 °C (273 °F) for 13 minutes. Fischer Core Series Brass, Stainless Steel, and Plastic 405 connectors are sterilizable in autoclave, Cidex, EtO, gamma radiation, Steris, or Sterrad systems.

Corrosion and chemical resistance

Choosing the right materials and coating can protect connections against galvanic corrosion mechanisms – pitting, intergranular, or crevice. The most common coating on metallic parts is nickel chromium or thin gold-based layers applied with a galvanic or sputtering deposition process. Common materials and coatings used in circular connectors are:

  • Brass with nickel or chromium coating
  • Aluminum with nickel or chromium coating or anodized (aluminum oxide Al2O3)
  • Stainless steel, which is one of the best materials for corrosion resistance, since corrosion protection is embedded within the material itself.

Products are tested in compliance with standards such as IEC 60068-2-11 Test Ka, MIL-STD-202 Method 101, and EIA-364-26. Testing includes long-standing exposure to a 5% salt solution at a temperature of 35 °C to ensure that there is no impact on mechanical or electrical functionalities.

In hospital, dentistry, and laboratory settings, as well as in food and pharmaceutical processing, devices and equipment must be regularly cleaned, disinfected, and sterilized. Product components – shells, contact blocks, O-rings and seals, cable jackets – should be made of ultra-resistant materials to withstand the conditions brought about by sterilization methods with chemicals such as Steris LCS (Liquid Chemical Sterilant with peracetic acid), Sterrad (hydrogen peroxide plasma), EtO (ethylene oxide), or through disinfection cycles such as Cidex Plus (glutaraldehyde) and Cidex OPA (ortho-phthalaldehyde and phosphate salts).

Chemical-proof connectivity is also demanded in the defense and security, and oil, gas, and petrochemical industries. In the latter hazardous environment, workers on land or offshore use downhole monitoring applications, seismic evaluation and drilling instruments, and geophysical and infrastructure maintenance devices that must resist chemicals such as aliphatic hydrocarbons, oils or fuels, greases, dilute acids and bases, detergents, and most aqueous salt solutions. For certain ATEX-certified areas and equipment in the petrochemical industry, additional property requirements for cables include flame retardancy and fire resistance.

Fischer UltiMate 80

With their special surface finish, most of Fischer Connectors’ products can withstand exposure to salt fog for 1,000 hours. Tested in compliance with IEC 60512 and MIL-STD-202H / 810G / 883K standards, the ultra-rugged NATO STANAG 4695 compatible Fischer UltiMate 80 connector passed several mechanical and electrical tests after an immersion of one hour into cutting oil Swisscut Twin 300, isopropylic alcohol, and fractionated fuel 60/95. It also offers high corrosion resistance (500 hours of salt mist).

Radiation resistance

High radiation resistance is required for tasks in nuclear or contaminated environments such as handling heavy radioactive loads, performing inspections, and repairing equipment. These tasks are sometimes performed remotely with robots due to inaccessibility or the danger of radiation exposure. Radiation-resistant connectors and cables are also required when healthcare professionals sterilize medical devices and equipment using gamma irradiation (typically Cobalt 60).

In hospital settings, there has been an increase in medical devices and instruments made of materials, such as plastics, that require low-temperature sterilization. Some single or two-piece shell disposable connectors with housing in ABS plastic withstand sterilization with both gamma irradiation per ISO 11137-2 (up to 60 kGy for Fischer Core Series Disposable) and EtO per ISO 11135.

Suppliers of high-performance, radiation-resistant connectivity solutions are regularly audited by their customers to ensure that they are compliant with main nuclear safety standards such as KTA 1401 from the Nuclear Safety Standards Commission (Kerntechnischer Ausschuss, KTA) and IAEA 50-C-Q from the International Atomic Energy Agency (IAEA).

Fischer Core Series Stainless Steel

Fischer Core Series Stainless Steel connectors are made of 316L stainless steel, polyether ether ketone (PEEK), and ethylene propylene diene monomer (EPDM), offering high radiation and corrosion resistance while ensuring high performance even in high temperatures. They also allow microbiological sterilization and radioactive decontamination.

Selecting materials for rugged connectivity

The following table helps identify which type of material is the most suitable for use in shells, contact blocks, and O-rings and sealing.

An aid to selecting the most suitable material for shells, contact blocks, and O-rings and sealing to resist mechanical stress and harsh environmental conditions in heavy-use or safety-critical applications.

References to KPIs, materials, testing methods, and industry standards mentioned in this article apply to products and solutions engineered by Fischer Connectors. Visit Fischer Connectors to learn more.

By Fischer Connectors.

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