world of defence procurement has not escaped financial clampdown and deep cuts. Whilst attempts have been made to offset the reduction in man power via an increased use of technology, the cost of electronic systems is also now subject to severe scrutiny.
The days when ‘defence budget’ could be read as ‘unlimited budget’ are long gone – if indeed that misconception was ever true and not based mostly on newspaper myth. What is certainly now true, however, is that defence spending is under the microscope.
Armed forces worldwide are being forced to implement cost-reduction plans yet the basic demands made of the equipment they use has not changed: it must operate reliably for extended periods under the harshest of conditions, withstanding extremes of shock, vibration and temperature, often in the open air where it is exposed to rain and humidity, the ingress of dust and sand and potentially other gases and pollutants.
Electronics systems are especially vulnerable to the hazards described above. Equally, makers of equipment used for military and aerospace applications are under increasing competitive price pressure. In many circumstances the answer may lie in implementing smarter design practices, enabling the use of components which may not carry a full military release – nor a full military price tag.
Here are some pointers that may help:
- Avoid DSCC drawings if at all possible. Instead choose QPL or EPPL parts.
- Try to remove high palladium content parts such as ceramic capacitors manufactured using ‘wet processes’ from designs. The price of palladium continues to rise and with supply still limited these parts are likely to increase in price throughout the year.
- Tantalum, like palladium, is still in short supply. Throughout 2010 the tantalum industry’s consumption of material exceeded production and projections indicate that there will be continued shortages for six to nine months. To this end tantalum prices are predicted to raise well into 1H 2011.
Wet tantalum capacitors are especially expensive and often on an extended lead time, however some suppliers like AVX have secured powder and wire supplies for 3~5 years and anticipate no impact on any of their Hi-Rel tantalum parts. Wet tantalums offer higher CV, long operating life and meet the vibration and shock requirements of military applications. However there are new technologies now available such as Kemet’s polymer hermetic seal devices which reduce the number of components required on the board, offer lighter weight and have low and stable ESR across temperature and frequency range.
-Can plastic bodied connectors be used instead of metal shells? Plastics and composites technologies have moved on a great deal, and not only are non-metal shelled connectors cheaper, they are also lighter.
Then of course there is the COTS Commercial Off the Shelf approach. John McHale of USA magazine Military & Aerospace Electronics has an interesting take. “Basically everyone has a different definition of COTS from the military programme manager all the way down to the component vendor,” he says.
“Maybe it is as one defence supplier says, ‘COTS is whatever my customer says it is.”
Cynicism aside, some manufacturers such as AVX have available AEC-Q200 Commercial Off the Shelf Plus parts, that is COTS devices, with up-screening to increase the level of testing. Passive component manufacturers such as AVX, Kemet, Syfer and Vishay now provide a wide variety of testing options giving you the flexibility to pick the testing required to meet your actual design requirements.
Although COTS parts may provide a viable option, there are possible issues to consider. COTS components will usually have a shorter lifecycle and while full Mil Spec devices are rated over the full temperature range, commercial parts may only be rated over a much narrower range.
COTS devices are unlikely to have the same traceability as full Mil Spec components. Also, the design and manufacturing processing techniques and even locations of COTS products are changed frequently which may impact their usefulness for military applications.
But perhaps the most difficult issue to consider when assessing the value of COTS components is obsolescence. Previously, military systems designers relied heavily on a procurement system that had a policy of maintaining longterm spare parts availability with detailed records. Therefore, engineers could easily assess the reliability and quality of available spare parts, and as a consequence did not have to concern themselves with obsolescence management.
However, with COTS parts, the situation is different and manufacturers may cease manufacture of specific parts with only six months to one year’s warning. Finally, COTS parts are more likely to suffer from the problem of counterfeiting, since the traceability is not so rigorous.
TTI has a Europe-wide focus team supporting military, aerospace and space customers. Part of the company’s brief is to help suggest ways in which design engineers can reduce cost and ensure component supply. The company regularly works with engineering teams to create preferred parts lists, leveraging design-in synergy across multiple sites to reduce inventory held by the customer, increase quantity and reduce costs.
Above all, hi-rel customers – even more so than for other applications – must only procure from authorised distributors. This reduces incoming inspection and the risk of using counterfeit products, and should result in cost savings without compromising system reliability.