Interconnection
In space, there can be no room for compromise
Miniature connectors are playing a vital role in ensuring the success of space missions which have to operate in extreme conditions
S
pace satellites come in all shapes and sizes, from miniature Cubesats measuring just 10x10x10cm all the way up to the International Space Station, capable of enabling several astronauts to work in space for prolonged periods. Weight is a critical problem for any satellite, no matter what its size or purpose; the lighter it is, the more payload it can carry. Yet there are other special
considerations which must be taken into account. On take-off and as it climbs into the atmosphere and higher, a satellite – and any instrumentation on board – will be subject to massive shock forces, many times G (9.80665 newtons per kilogram of mass). Once in space, satellites will experience extreme fluctuations in temperature because they are constantly moving between sunlight and shade – for example, the ISS orbits Earth once every 90 minutes with a “day” and “night” occurring during each orbit.
Even an entry model CubeSat satellite costs an estimated $150,000 to make and launch; more sophisticated commercial and defence satellites cost many times that, so the cost of failure is prohibitive, and a component failure is simply not acceptable. Electronic interconnect is a particularly challenging issue, since electronic connectors are required to maintain signal integrity while also providing a physical mechanical link. Extremes of shock, vibration and temperature are the worst possible combination of events for such components, which are constructed from plastic and metal materials which have different temperature coefficients of expansion. For these reasons manufacturers of Hi- Rel systems are requiring innovative
24 February 2014 interconnect systems.
For example the new Gecko range of 1.25mm pitch Hi-Rel connectors has benefited from Harwin’s track record of manufacturing high- reliability connectors for safety-critical applications, drawing on market feedback over many years to its similarly high-reliability Datamate range. A 2mm pitch cable-to- cable, cable-to-board and board-to-board connector family, Datamate has been specified for use in harsh operating conditions many times, featuring on the Robonaut 2 NASA space robotics program and many successful Cubesat projects. Datamate's contact design features a stamped, four-fingered, gold-plated beryllium copper clip with highly stressed contact beams. The clips reside in the female half of the connector clasping round pins tightly, ensuring the integrity of electrical connection even under severe conditions. Additions to the Datamate family include miniature, lightweight mixed technology versions offering a multitude of configurations for signal, power and/or coax. Datamate Mix-Tek connectors feature power contacts rated for use at up to 20 amps and are particularly suited to
Components in Electronics
designs based on a ‘peak demands’ principle that necessitate interconnect systems with a high current carrying capability.
Datamate’s signal contacts are rated at up to 3 amps; coax contacts are rated at 50 ohms. The Datamate range also includes REMI shielded versions (Datamate S-Tek) and a variety of latching options for added security.
Smaller and lighter But inevitably and inexorably, the space industry, in common with many other sectors, is requiring smaller, lighter devices, yet with the same ability to withstand high shock and vibration. Hence Harwin’s newly- launched, Gecko 1.25mm pitch
connector family which suit demanding
applications and deliver high performance. Harwin’s low profile G125 series connectors are designed to offer high performance in a miniature package. The 1.25mm pin spacing
results in a 35% space saving over other high- performance connectors such as Micro-D and a 45%
reduction in required PCB space over 2mm pitch
interconnect systems.. The connectors are rated to handle 2A per contact. Tested and proven to allow high performance in extreme conditions, the G125 family can operate within a wide temperature range (-65 to +150°C) and under extreme vibration (Z axis 100g 6m/s). See the table opposite. The performance of miniature connectors under extreme conditions is largely
dependent on the contact design. Many styles are used across industry for Hi-Rel applications but Gecko’s high performance is made possible by Harwin’s patented four-finger Copper Alloy contact. The contact, which delivers high performance and extreme reliability, at the 1.25mm pitch level is shown in Figure 2. Offering up to 50 contacts per connector and available in dual row cable- to-board and board-to-board configurations, Gecko family connectors include a wealth of features including polarization points that prevent miss- mating, easy identification of the No 1 position for fast visual inspection and optional latches that allow simple and fast de-latching that requires no special tooling. Cable connectors feature a rear potting wall adding an extra level of strain relief.
G125 Connectors are manufactured to withstand high numbers of mating cycles but also feature low insertion and extraction forces. Moldings are manufactured from RoHS-compliant, environmentally friendly materials, eliminating harmful chemicals even before they are added to restricted substances lists. Pre-assembled cable configurations are available in a variety of layouts featuring male and female, single and double ended, in a variety of standard lengths. Board connectors are packaged in tape and reel format. Addressing cost, it’s fair to say that
today, all budgets whether the application is military or commercial, are subject to strict scrutiny. Gecko addresses this concern, with price-per-contact levels set at industrial levels running at an order lower than pure-play military devices. Many times engineers simply wait (or forget) about connectors until the last minute. The result is that often they leave themselves with little to no board space (or volume in general) for the connector. Understandably, design teams are more concerned with the more glamorous features of their projects - the processing, imaging, motion, etc - commonly
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