Page 41 - 2019 Mil/Aero eBook
P. 41

Eight Things to Know About M39029 Contacts
Steve Smashey, President, and Mike Conte, General Manager, SOS Engineering, Inc.
To manufacture a reliable, high-performance connector for harsh-environment applications, the design process should start with the contacts. The M39029 (SAE AS39029) specification includes requirements for crimp contacts to ensure durable and consistent signal transmission in demanding operating conditions. Commonly used in military, defense, industrial, and other harsh-environment applications, M39029 contacts are available in a variety of options. As a result, not every M39029 contact is created equal. Here are eight things to consider when specifying M39029 contacts.
1. Contact Materials
The M39029 specification simply states that the contact must be manufactured out of a copper alloy. However, this material specification is quite vague, as modern material sciences have produced more than 400 copper alloys. Copper alloys are metal alloys that have copper as their principal component. They all offer high resistance against corrosion, but other characteristics can vary. Well known copper alloys include bronze, where tin is added, and brass, which includes zinc. Brass is commonly sourced for sockets used in commercial applications. For harsh environments, leaded nickel copper or beryllium copper are ideal for their durability. Copper alloy materials can be selected based on the application requirements.
2. Tensile Strength
Higher quality materials inherently produce higher quality contacts with higher tensile strength and, as such, better spring properties. The M39029 specification states that contacts must be able to support a minimum of 500 mating cycles. Tensile strength is important for the reliability and durability of interconnects that serve applications with high mating cycles and long operating lives. High tensile strength ensures that female (socket) contacts will spring back into place after each mating and unmating cycle, and proper placement ensures reliable connectivity for the next mating cycle.
3. Contact Size
Contact size is also a consideration when choosing the material for M39029 contacts. Larger contacts usually have thicker walls, which helps to make sockets less susceptible to losing their spring properties. As a result, in many applications, large contacts can be made of lower quality, less costly copper alloy materials.

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