Aerospace Assembly / Automotive Assembly / Medical Devices Assembly / Electronics Assembly

Meeting the High-Reliability Challenge

November 1, 2012
Trans

Success stories in high-reliability engineering don’t get much better than NASA’s Curiosity rover, which began exploring Mars in August. After a 10-month, 350-million mile journey, the rover landed on the Red Planet without a glitch.

Weighing in at just under a ton, Curiosity is 9.5 feet long, 8.9 feet wide and 7.2 feet tall. It’s equipped with six 20-inch-diameter wheels in a rocker-bogie suspension. Each wheel is independently actuated and geared, and each front and rear wheel can be independently steered.

The rover also has a robotic arm with a cross-shaped turret holding five devices that can spin through a 350-degree turning range. Nearly 7 feet long, the arm has three joints so it can extend forward and retract again while driving.

All totaled, Curiosity is equipped with 47 rotary and linear actuators. Each actuator has a sensor, called a cold encoder, to provide performance feedback to the rover’s control system. The sensor accurately measures the actuator’s position, velocity and other variables despite extreme temperature changes, which on Mars range from -128 to +85 C.

The encoders were assembled in Valencia, CA, by the High Reliability Solutions Div. of Flextronics International. “Flextronics is extremely proud to have played a part in this historical exploratory mission to Mars,” says Paul Humphries, president of the High Reliability Solutions Div. “We share NASA’s excitement for the complex rover program and are thrilled to have contributed to this important scientific exploration.”

Flextronics’ Valencia facility specializes in highly reliable and durable microelectronics for aerospace, defense and medical applications. Another Flextronics subsidiary, Multek Flexible Circuits, provided the thermal control materials that enabled Curiosity to travel safely to Mars.

Why Contract Manufacturing?

Surviving an epic journey through space and a harrowing descent through the Martian atmosphere is no accident. It takes rigorous design, stringent quality control, and in some cases, the right manufacturing partner. For a growing number of OEMs in the automotive, medical, aerospace and defense industries, the right partner has been Flextronics.

The High Reliability Solutions Div. consists of three business groups: automotive, medical, and aerospace and defense.

The automotive group specializes in lighting, such as reading lights and luggage compartment lights; power electronics, such as DC/DC converters and fan controllers; connectivity products, such as interface devices for cell phones and iPods; and electronic assemblies, such as brake modules and keyless entry systems.

The latter is a “traditional electronics manufacturing services business...whereas the other groups offer more of their own design content,” explains Humphries.

The medical group can produce a wide range of products, from small, plastic disposables, such as cardiac catheters, to complex electronic assemblies, such as insulin pumps and chromatographs.

The aerospace and defense group makes avionics, displays and flight management systems, in addition to more specialized assemblies, like the encoders for the Mars rover.

“Six years ago, our medical business was less than $200 million, and our automotive business was less than $100 million,” says Humphries. “This year, the medical group will do around $1.3 billion, and automotive will be close to $900 million. The aerospace and defense group is just starting up, and it will generate about $100 million in sales this year.

“[These diverse groups] are similar in that they’re all fairly regulated industries. ...They all have relatively long design cycles and product life cycles. ...And they all have stringent quality requirements.”

That commonality has fueled synergies between the groups, says Humphries. For example, development work on LED-based interior lighting by the automotive group led to introduction of cabin lighting products by the aerospace and defense group. And, the experience that the medical group gained in getting Food and Drug Administration approval of its manufacturing processes was instrumental in helping the aerospace and defense group obtain certification in AS9100, a standardized quality management system for that industry.

“We make 50,000 different products every day,” Humphries points out. “For us, the product itself is somewhat immaterial to the processes we have to control manufacturing, assembly and logistics. We’ve developed sophisticated processes, metrics and IT systems to manage any project, whether it’s a mechanical product or an electronic product; a high-mix, low-volume product or a low-mix, high-volume product. It’s really more about the system, and we can often manage that more effectively than an OEM.”

OEMs can also take advantage of Flextronics’ economies of scale. The company tallied more than $29 billion in gross revenue during its 2011-12 fiscal year, and it has manufacturing facilities in 30 countries and four continents. “Our SG&A ratio [sales, general and administration expenses as a percentage of gross revenue] for the year was 2.9 percent, which is unheard of in the automotive, medical or aerospace industries,” adds Humphries.

Reliability Starts With Design

OEMs work with Flextronics in a variety of ways, from traditional build-to-print orders through to designing and manufacturing a product from a blank sheet. But Humphries says his group’s “sweet spot” is design services—refining existing designs to satisfy specific customer goals. 

“We work on design for assembly, design for cost, design for supply chain, and design for reliability,” says Humphries. “We work hand-in-hand with our customers’ design engineers to come up with the most robust, cost-effective design that can be made in high-volume production.”

For example, a customer had designed a complex, high-frequency circuit board that was very costly—more than $600 per bare board. The board required five lamination steps. Since each lamination step has yield losses due to misalignment and other process variables, reducing the steps would save money and improve yield.

After evaluating the design, Flextronics engineers believed they could reduce the lamination steps by inserting another technology in the board fabrication process, and they redesigned the board to require fewer laminations.

To validate the performance of the new design, engineers conducted an extensive radio frequency analysis of the board both before and after the redesign. After Flextronics demonstrated that performance was the same or better after the redesign, the customer agreed to the change. This lowered the cost of the board by $200, producing a yearly savings of more than $2 million.

Before assembling a product, the company conducts failure modes and effects analyses on both the design and the assembly process. Once potential trouble spots are known, the company can implement process controls and poke-yoke mechanisms to prevent manufacturing defects.

“You can design quality into a product, but you can only manufacture quality out of it, because of the inherent variability of any process,” Humphries points out.
For legal or security reasons, many of the division’s customers require their products to be assembled in the United States. Others have no preference. In the latter instance, Flextronics will assess the customer’s design, comparing it against the capabilities of its supply base. In some cases, Flextronics engineers will suggest changes to components or materials to leverage the company’s supply chain advantages.

Flextronics has developed simulation software, known as SimFlex, that can analyze the entire supply chain, from raw material coming out of the ground, to the finished product, to aftermarket service. Based on multiple variables, such as product complexity, logistics costs and taxes, the software recommends the best location to manufacture a particular product.


All Systems Go: Assembling the Cygnus Delivery Spacecraft

More than 400 kilometers above the Earth, the International Space Station continuously circles our planet as it has done since October 1998. A joint project of the United States, Russia and Japan, the station is an orbiting laboratory where crew members conduct experiments in astronomy, physics, human biology and meteorology.

The station consists of pressurized modules, solar arrays, trusses and other components. It requires regular delivery of supplies, spare parts and scientific experiments. It received several deliveries this year from both American and Russian spacecraft.

The station’s next load of supplies will be delivered by Cygnus, an unmanned spacecraft made by Orbital Sciences Corp. Set to launch in December 2012, the Cygnus will be thrust into space on the Antares 110 rocket, also made by Orbital Sciences. The Cygnus will disintegrate as it falls back to the earth.

After the initial mission, Orbital will send seven more Cygnus spacecraft to resupply the space station between 2013 and 2015. The eight missions will involve the delivery of nearly 20,000 kilograms of cargo and the disposal of tons of waste from the space station.

“The timeline from spacecraft design to launch is about two years,” says Dan Wiles, senior manager of program scheduling at Orbital. “Each spacecraft contains tens of thousands of components and miles of wire.”

At Orbital’s Dulles, VA, manufacturing facility, workers are assembling service modules for multiple Cygnus spacecraft. The service module features avionics systems from Orbital’s LEOStar and GEOStar satellites, as well as propulsion systems from GEOStar satellites.

Assembly of the service module is done manually, except for lifting equipment to move workers or large subassemblies into place. Module assembly lasts 16 months and requires two crews of seven assemblers each working 11 shifts per week.

Assembly takes place in a small Class 10,000 clean room, a large Class 100,000 clean room, and a large assembly and integration bay. The finished vehicle then goes to an environmental test bay.

The Class 10,000 room consists of 30-day workcells, where workers assemble tiny to moderate-sized subassemblies, including all electronics.
The Class 100,000 room and the assembly and integration bay feature four- to six-month workcells, where subassemblies are joined and tested.

The environmental test bay is divided into 10 areas. The largest are the thermal vacuum and vibration test cells. Other test cells include antenna range, electromagnetic interference and compatibility testing, structural testing, thermal cycling, tube bending, box-level vibration, and leak testing.

Each module spends seven days in the vibration area, where Orbital duplicates the acoustic and vibration conditions the module might encounter in space. After this, the module spends 13 days in the thermal vacuum area. Finally, the spacecraft’s fuel tanks are pressurized with helium to check for leaks and to test the function of the pressure gauges. For safety reasons, this last test is done in a blast cage.

Also included in the environmental test bay is the propulsion work center, where the Cygnus propulsion system is assembled and tested.

—Jim Camillo, senior editor 


 


ASSEMBLY ONLINE
For more information on assembling high-reliability products, visit www.assemblymag.com to read these articles:

  • How Reliable Are BGA Connectors
  • Quality in Assembly: Get the MOEST out of Reliability Testing

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