Can MCMs deliver in the long term?

01 November 2007

Alter Technology UK has recently introduced its ObsServe service to monitor part availability

In 30 years well-designed high-reliability products will still be with us – but what about spares?

Statistics are often used to shield us from the cold, hard facts of life, but they offer little in the way of comfort. For instance, according to various industry reports, the market share for military and aerospace grade components has dropped from nine per cent in 1984 to less than 0.5 per cent today. This also highlights the fact that engineers responsible for the service or repair of equipment built in 1984, that may still be in use today, may stand much less chance of finding those military and aerospace grade components.

The suppliers for those parts, in the 80s, would necessarily have offered guarantees of supply, but will they still be available in another 30 years or more?

This is the question facing companies developing military and aerospace equipment today, making the statistics much more pertinent. With so much less demand (based on the market share figures) there is a commensurately lower supply of high-reliability components and an ever-present risk of obsolescence for all other components.

Supply and demand
For the military and aerospace markets, this supply and demand conundrum has been tackled in part by the shift towards commercial off the shelf (COTS) components, but with this shift comes the added complication of a much longer and more convoluted supply chain.

The introduction of several additional links in this supply chain for high-reliability components can inherently bring a loss of ownership when considering stability of supply, because it may no longer fall to a single supplier to provide it. Any link in the chain can succumb to unforeseen supply issues, at any time. It should also been born in mind that the traceability of high-reliability and the traceability of COTS components is not necessarily comparable.

Moreover, the supply of commercial devices is also subject to commercial pressures, meaning this sector exhibits more ‘normal’ fluidity than either military or aerospace. So while the benefits of COTS are clear the challenges continue to build, while the requirements remain the same: reliability, supportability, reparability, affordability, to be certifiable and, above all, to be safe.

It is becoming increasingly difficult to source high-reliability components and when they are found, their supply could be threatened at any time by commercial market pressures. Little wonder then, that the impact of obsolescence must now, more than ever, be planned for.

A service recently introduced by Alter Technology UK (previously known as IGG Component Technology), called ObsServe, is intended to do just that, by analysing a bill of materials and comparing it to a database of ‘at risk’ components, maintained by Alter.

Using a form of Boolean logic called Apollo Voting, each component is given a red, amber or green status. Red means the part is subject to an existing PCN (product change notification) or (last time buy) alert, or has already been made obsolete by the manufacturer. Amber indicates restricted availability or that the risk of obsolescence in the near future is high. Green shows a high level of confidence in the part’s continued availability with the understanding that, if it is a commercial part, its lifespan could be as short as three months.

When faced with a red light, a natural
reaction may be to panic and in fact there are five classic ‘stages’ of obsolescence: denial, anger, bargaining, depression and, ultimately, acceptance. By reaching the acceptance stage as quickly as possible, it could be argued that the first four stages are irrelevant, but human nature shows us otherwise.

Replacing the obsolete
Once it has been accepted, however, there is still the challenge of replacing the obsolete part. Increasingly, for the high-reliability market, a viable solution is to use either a hybrid or multichip module (MCM) approach, whereby a replacement device is manufactured using the same or similar die as used in the original part.

Obviously, for this to be viable, access to a supply of bare die is required and, given the delicate nature of bare die, this isn’t without its own challenges. Here too, Alter has a solution. Carefully developed procedures allow Alter to screen both the suppliers of bare die and the die themselves, for use in hybrids or MCMs, as well as monitor their status throughout the manufacturing and long-term storage processes.

The stages involved
Essentially there are four stages to the process: selection, evaluation, approval and verification. The selection of a supplier of bare die takes a number of factors in to account. These include the manufacturer’s capabilities, with respect to the company’s organisation, its quality assurance procedures, and any product development strategies it has in place, as well as its manufacturing facilities.

This is followed by an analysis of the expected die availability, by looking at the company’s objectives. For instance, are they committed to providing long-term availability of the bare die? Does it fit in to its business plan? If there is a product roadmap, how does it fit in with that, and what influences the roadmap’s direction? All these factors need to be considered when selecting a potential bare die supplier.

Another important factor, not to be overlooked, is the suitability of the bare die itself. Does it meet the necessary quality and reliability criteria? Could manufacturing problems affect delivery or availability?

Once these crucial steps have been conducted, there follows an evaluation period where all of the information gathered is analysed. This includes a constructional analysis of the bare die itself, providing valuable information about the technology used to manufacture the die and how it is laid out, even down to the circuit schematics and the actual construction. By using its advanced inspection equipment, Alter is placed to delve deeper in to the physical world of microscopic circuits and critically assess the design and manufacturing processes employed.

Final approval
With this information, recommendations can be made as to the suitability of both the supplier and its technology. This is the approval stage and includes a risk assessment based on all the data gathered in the preceding stages, as well as the results of batch testing. It is during the testing phase that further critical data is gathered, providing endurance and failure analysis; through endurance testing, the results gathered can be statistically verified, while the investigation of failures helps determine their cause, effect and the risk they represent.

With this information, a test strategy can be implemented and it is this that represents part of the final and ongoing stage of verification. Through periodic sample testing, as determined from the analysis stage, a higher degree of confidence in the end components, be they hybrid or MCM, is achieved.

Obsolescence represents a real and present danger in all sectors of the electronics market but none more so than in the military and aerospace sectors, where long periods of falling demand has resulted in a dearth of supply. However, through companies such as Alter and the continued battle against obsolescence, there remains a viable alternative to stability of supply.

LLOYD FRANCIS is aerospace and defence manager, Alter Technology UK

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