In the hot zone: how a novel material solved an electronics assembly dilemma deep in the Indian Ocean.

Ed. note: For the complete article, please visit circuitsassembly.com/cms/content/view/4026.

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In the competitive oil and gas drilling industry, a project's success--and a company's reputation--can hinge on seemingly insignificant variables such as a few degrees of temperature on a circuit board. That was quite literally the issue facing a major oil-exploration company as it performed data-collection tests at a client's wells sunk deep in the Indian Ocean.

Traditional, commercially available circuitry used in deep-sea wells can handle temperature spikes of up to 350[degrees]F and pressures of 20,000 psi or more, perfectly adequate for 90% of deep-sea wells worldwide. However, explains project manager Tony Jones, "as oil gets harder to find and the technology improves, the economics of looking for crude becomes more viable in increasingly hostile environments."

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For the Indian Ocean project, Jones and his team were working with temperatures up to 400[degrees]F in a geothermal "hot spot"--where magma, steam, and other geological phenomena contribute to extremely high temperatures. When Jones' team introduced a new testing service in the area, they feared standardized components wouldn't be able to take the heat.

With such high temperatures, the components would run at or exceed their limits for extended periods of time. During the 12- to 24-hr. tests, the equipment would be gradually subjected to increasing temperatures and would need to perform at sustained temperatures of 350[degrees]F or higher for four to 12 hrs.

"The reliability of the components is dependent on time and temperature," Jones explains. "The longer you stay at higher temperatures, the more the life of the electronics deteriorates. And as the life of the electronics deteriorates, reliability deteriorates as well."

Under typical deep-sea conditions, a component is used until it reaches the end of its expected life, and then is replaced. If a component fails during testing, the test apparatus must be removed from the well and the component replaced before testing can resume, at a possible cost of tens of thousands of dollars per day in lost production.

"This industry requires less than 5% lost time on an operation," Jones imparts. "The industry standard is 95% efficiency or better. So if you can't maintain a high level of efficiency, you might not get chosen to do the work."

Many projects dealing with temperatures exceeding 350[degrees]F would call for custom components or components sealed in Dewar flasks, a kind of protective sleeve. But Jones was happy with the functionality of the components on hand--provided they could find a way to shield the circuitry from the worst temperature spikes.

Because of the depths at which the components would be used, they had to be enclosed in a special housing to protect them from the pressure. But the sealed housing acted like an oven, baking the circuits inside. The pressure housing precluded cooling apparatus, such as fans.

An overheated component can stop working for a while and then resume working when temperatures cool--or it can die altogether. To avoid both scenarios meant finding a way to keep the components safely under the 350[degrees]F threshold.

Avoiding a Redesign

Without a suitable solution, the team would be faced with redesigning the chassis to better dissipate the heat. They would also have to redesign the circuit boards to convey the heat to the chassis instead of to the atmospheric cavity or the external pressure housing. The in-depth redesigns would have added time and expense that neither Jones nor the client wanted.

Another alternative Jones considered was for his team to pot or encapsulate the components using commercially available materials. "While that solution might have worked," Jones indicates, "it's a time-consuming, labor-intensive operation that requires a lot of processes to ensure consistency."

Jones began searching for possible solutions, eventually contacting Dow, which brought in Ultimate Solutions (ultimatesolutions-inc.com). Ultimate Solutions makes a patent-pending technology called preforms, a highly filled silicone material that protects electronics components from shock, vibration and temperature extremes.

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