ARINC 600 Next Generation: Stamped-and-Formed Signal Contacts Lower Costs, Save Weight

ARINC 600 Next Generation:
Stamped-and-Formed Signal Contacts Lower Costs, Save Weight

By Steven J. McIntire, Global Product Manager—I/O Connectors
Tyco Electronics—Aerospace, Defense, and Marine Business Unit

The Challenge
The typical ARINC 600 posted signal socket contact has a screw-machined, copper alloy body, with socket tines on one end, and a straight solder tail on the other end. The screw-machining process used to make these contacts is relatively, requiring multiple manufacturing steps to make the completed part. Even when employing the most advanced screw-machining technology available, individual contact cycle times are measured in seconds, at best. To ensure a stable contact resistance at the mating interface, the contacts are then gold plated through a barrel plating process that results in gold coverage over the entire contact. After plating, a stainless steel hood is then press-fit onto the body over the tines.

By contrast, stamping-and-forming technologies use progressive die technology that is capable of producing multiple, completed contacts in just a fraction of a second. In addition to these inherent production efficiencies, stamping-and-forming technology yields reduced material handling, improved tool life, and better dimensional repeatability compared to screw machining. Gold usage is also greatly reduced through the ability to selectively plate the precious metal only in the desired separable interface.

However, the contact design must continue to meet all the mechanical and electrical requirements as specified in the ARINC 600 specification, and must be fully compatible and intermateable with the existing pin contacts. So the challenge was to design a stamped-and-formed version of the ARINC 600 signal contact, while maintaining all the performance characteristics of the original design.

Contact Design
The design of the contact socket tines was based on the existing screw-machined contact, which has two tines opposed to each other. The material selection was driven by the need to meet insertion force and stress relaxation requirements, as well as current-carrying requirements. The design was evaluated for an acceptable normal force per beam (tine) so as to have a reasonable insertion force. The maximum stress was also calculated to ensure that the tines would not yield when the pin was inserted. Finally, the bulk resistance was also analyzed to confirm the ability to meet the ARINC 600 electrical requirements. The material selected was a high-performance copper alloy that combines acceptable conductivity and stress relaxation properties with excellent formability properties. The design modeling indicated that the new stamped-and-formed contact would meet or exceed all of these requirements.

Figure 1 compares the two types of contacts in terms of insertion force, resistance, and weight.

The same hood that is used for the screw-machined contact is also used on the stamped-and-formed contact. Whereas the hood is simply press-fit onto the screw-machined socket body, the stamped-and-formed contact design includes a superior secondary retention feature through the addition of two dimples on opposite sides of the hood.

The tail end of the contact includes an embossed region with two right-angle wings, which act as the retention feature when the contact is installed into the insert. These features also provide added mechanical strength to the contact to resist buckling. The solder tail is based on an existing v-groove design and is equivalent to the screw-machined tail of 0.025-inch diameter. Likewise, the tail lengths are available in lengths equivalent to the existing nominal 0.250 and 0.375-inch tails. In this way, receptacle assemblies with the stamped-and-formed contacts will be compatible with printed circuit boards used on existing ARINC assemblies.

The stamped-and-formed contact is also available with a press-fit eye-of-needle (EON) tail where the stamping process is ideal for creating the eye feature. The EON has been designed for a 0.035-inch diameter hole and a PCB with a minimum thickness of 0.063 inch. This press-fit tail design provides an added application savings to the box manufacturer because they can replace a time-consuming soldering process with a simple press operation. It should be noted that the EON tail design has certain box-level design requirements that need to be considered.

Figure 2 shows various contact configurations.

One of the advantages of the stamping process is that the contacts are handled on a continuous carrier strip and transported on reels. This can be advantageous within the manufacturing process for several reasons. The carrier strip allows for the contacts to be selectively plated. This way, the entire body can be nickel plated; the socket tines are selectively gold plated, while the tail can be plated with options such as tin-lead and RoHS-compliant materials like matte tin and selective gold. Given the recent increases in the cost of gold, selective plating can have a large impact on the cost savings for the contacts.

Also, because the contacts are on a carrier strip, it is much easier to automate the processing of the contacts. The station can feed the contact strip, install and dimple the hood, separate the contact from the strip, and load the contact into the insert. The station is also capable of selectively loading the contacts into the insert according to customer requirements. By replacing previous manual operations with this automated station, additional cost savings can be seen and the more consistent process improves quality control.

Finally, the design of the insert has been modified to accept the new stamped-and-formed contacts (Figure 3. A simple one-piece insert component replaces the existing multipiece insert assembly. Existing inserts use two thermoplastic halves with retention clips installed, which are then bonded together and painted. The new insert still meets all the ARINC dimensional requirements, but again provides another cost savings opportunity. Because the contacts are installed from the rear side of the insert, they are not removable from the front side after assembly to the PCB.

Results
Extensive validation testing has already been completed on the stamped-and-formed contact to confirm its performance and reliability. The contacts were tested against a variety of electrical, mechanical, and environmental requirements, often using the test procedures referenced in the ARINC 600 specification as the baseline requirement.

In addition to meeting all the necessary electrical and mechanical requirements, the stamped-and-formed contact also reduces weight. The stamped-and-formed contact is approximately 30 percent lighter than the standard screw-machined contact. Depending on the shell size and the number of signal contacts installed, this can reduce the weight of a receptacle assembly by up to 10 percent.

Steven J. McIntire is the global product manager, I/O connectors for Tyco Electronics—Aerospace, Defense, and Marine Business Unit. Mcintire has 20 years of experience in the electrical connector industry, with a primary focus on the aerospace industry for the past 16 years. He has held various roles in engineering, engineering management, and plant management, and has been the North American product manager for various aerospace I/O connectors for the past three years, and global product manager for ADM I/O connectors since April, 2010. McIntire has a B.S. in industrial engineering from Pennsylvania State University.