Dave Doherty, the new president and chief operating officer of online distributor Digi-Key talks to Electronics Weekly about how the internet is changing the way engineers source components and the hype around IoT.

Q: What do you see as the biggest challenges facing the electronics distribution sector?

Dave Doherty

Dave Doherty : Adapting to the reality of a global economy. This is far different from having companies incorporating around the globe but operating regionally. To date, customers are moving faster with their supply chain needs and suppliers are struggling to keep pace with their regional legal entity structures operating autonomously. In addition, there are dynamic currency fluctuations in play in this global economy.

Q: How have you seen the customer landscape evolve in the past five years? Where do you see it going in the next few years?

Dave Doherty : Customers are looking for instantaneous access to information and they are more than willing to self-serve, in fact many prefer it. Our B2B customers’ response time to their end customers continues to shrink, requiring us to offer solution based products and not just parts. There are still the mega-volume consumer aimed products such as mobile devices but there is an even larger proliferation of high-mix/low volume requirements in areas like industrial, medical, IoT, etc.

Q: How do you see the evolution of technology (IoT, 3D Printing, Big Data, etc.) impacting the demand from the customer?

Dave Doherty: Our industry loves hype and attributing the latest and greatest buzz words to trends. The hottest of late, IoT, is not a recent phenomenon. Sensor activity has been accelerating for some time, as has a movement towards connectivity and a lowering price point for microcontrollers all the while accelerating a movement towards mechatronics.

Our industry (consumers, suppliers, distributors) has been very respectful of our social and environmental responsibilities (i.e. RoHS, NoPB). These trends will only contribute as we balance the need to push and develop cost effective technologies in a socially responsible way. Our industry in an example of global ingenuity at its finest. From a cost/performance perspective, I’m hard pressed to think of another industry that could keep pace.

Q: How are customer demands for design help changing and evolving? What are your key market segments? How is that evolving?

Dave Doherty: The need for 24/7 technical and customer service support is profound. The desire for web chat activities instead of traditional tech support calls. We are seeing more activity for kits, development boards, modules, reference designs and other solution oriented products.

We don’t necessarily see a change in direction for the supply chain, but rather an acceleration of our response to our customers. You will see more electronic data interchange connecting our systems through legacy means such as EDI and emerging alternatives such as APIs.

Q: What are your greatest concerns from a supply chain perspective for the remainder of the year?

Dave Doherty: We are in the segment of the supply/demand cycle in which product is generally available with low lead times. This tends to drive lower customer volumes offset with increased frequency to minimise their inventory carrying costs. These cycles tend to flip fairly quickly, through either a real or perceived disruption to the supply chain, inevitably accentuated by an emotional over-reaction that stretches lead-time and increases supply chain disruptions. We cannot become complacent or lose sight of our role in the process.

Richard Wilson

More on: Making MEMS on 300mm wafers

September 28, 2015

steve bush

Making MEMS on 300mm wafers

French research fab CEA-Leti has begun manufacturing accelerometers on 300mm wafers, thought to be a first for the MEMS industry.

“This demonstration that our 200mm MEMS platform is now compatible with 300mm wafer fabrication shows a significant opportunity to cut MEMS production costs,” said Leti CEO Marie Semeria. “This will be especially important with the expansion of the Internet of things and growing demand for MEMS in mobile devices.”

Leti has a 30 year history in making MEMS, spinning out MEMS companies, and selling MEMS processes to chip firms. It currently has a team of 200 people working on MEMS.

The transferred process is its ‘M&NEMS’ technology – micro and nano MEMS, which came out of a programme to make many types of micro-mechanical structures using a single straightforward process.

What emerged a way to make any mixture of the following sensors on the same chip: accelerometers (x, y and z axis), gyroscopes (x, y and z axis), magnetometers (x, y and z axis), pressure transducers and microphones.

Capacitive (electrostatic) sensing has been avoided. Instead, for simplicity, all sensing is piezoresitive (piezo: Greek for squeeze).

“Piezoresistor sensing is robust, and importantly it is compact. We have miniature sensors, half the size of other peoples,” Jean-Rene Lequepeys, head of the Si component division at Leti, told Electronics Weekly.

Not to be confused with piezoelectric sensing, detection is through measuring the change in resistance of silicon nano-wires (220x220nm2 cross-section) as the tension in them changes. This is the ‘NEMS’ part of the process name. In lithography terms, 220nm wire geometry means relaxed constraints on available lithography.

These wires are just visible close to the substrate in the photo, which is of the measurement end of a single axis accelerometer. The ‘proof mass’ whose movement is measured, and extends far to the right of the photo (see accelerometer diagram) is hewn from 20µm-thick epitaxial silicon – the ‘M’icro part of the process.

As an aside, the two blade-like struts in the photo are the entire support structure for the proof mass – the rest of it is (see diagram below) cantilevered and free to move. Accelerometers for all three axis are constructed in the same plane

Construction starts with a Si-on-insulator wafer, prepared with a 220nm silicon top layer – which will yield the piezoresistors and the foundations of other structures. “We can develop the same technology on bulk silicon, but it is easier on SoI,” said Lequepeys.

Piezoresistors are patterned and etched from this 200nm layer, then protected by a temporary oxide covering.

Following this, 5-25µm of silicon is grown on top, from which masses and other MEMS structures are then etched – the buried oxide layer acting as an etch-stop.

NEMS and MEMS components are finally released by removing the oxide, including SoI wafer oxide, from around the piezoresistors and masses.

All the sensors mentioned earlier have been designed to be made from the same basic parts – a 220nm thick layer for piezoresitive gauges and the full later-grown thickness for masses and other parts.

Magnetometers, for example (which are sensitive enough to be used as compasses), are moving structures with a ferromagnetic layer deposited on top.

“For the magnetometer we use a balanced design to be not sensitive to the acceleration. It means that we have a symmetric design in order to have the centre of inertia that coincides with the rotation axis of the structure,” said Lequepeys.

The firm has transferred its technology Tronics Microsystems, which is making three accelerometers and three gyros within a <4mm2 footprint.

According to Lequepeys, while Leti can put triple accelerometers alongside triple gyros and triple magnetometers, competitors have to put the magnetometers on separate silicon. Type pressure monitors are a target for the process, as they need to combine an accelerometer and a pressure sensor.

300mm

According to Lequepeys, there are 97 process steps in M&NEMS, and a recipe for each has been adapted for 300mm production.

Moving the M&NEMS process to 300mm equipment is all about reducing the cost of MEMS production for consumer and automotive markets – at which M&NEMS is aimed. Ex-fab device costs are 30% cheaper in 300mm compared with 200mm, said Lequepeys.

300mm is also better for larger MEMS. “Auto-focus mechanisms are quite big devices, and so are digital loudspeakers and image-based sensors – for example for ultrasonic or micro-bolometer imaging,” he said.

Another reason for moving to 300mm is CMOS.

M&NEMS always uses a separate read-out chip to carry associated signal processing circuits. “We do MEMS and CMOS on the same wafer for other MEMS processes, but not M&NEMS,” said Lequepeys. “There are no major obstacles, but we would need to see an advantage in terms of cost.”

Both 200mm and 300mm processes at Leti offer 3d operations such as through-silicon vias (TSV), wafer thinning, wafer stacking and copper pillars which allow M&NEMS chips to be stacked with read-out chips, but while the 200mm process offers 130nm CMOS, 300mm opens the doors to 65, 45 and 28nm read-out processing.

NEMS

Starting in a similar way, with an SoI wafer with thin top silicon, Leti has developed another process called ‘NEMS’.

Aimed at biological and chemical sensing, it runs only on Leti’s 200mm line. “The size of market not large enough to justify 300mm today,” said Lequepeys.

Sensing is once again though piezo-resistors, but there is no thick epitaxial layer. Instead, sensing structures are thin cantilevers made from the SoI wafer silicon (see photo right).

These cantilevers, which each have two piezoresistors, are vibrated by an oscillating electric field from a nearby electrode. The frequency at which they resonate is dependent on the mass of the cantilever and any mass on its surface.

NEMS has been used to develop a gas chromatograph in conjunction Caltech – the design of which is being exploited by a joint spin-out called Apix.

A sample of gas fed into it passes through a long micro-machined channel (see photo right).

During the journey different molecules in the gas travel at different speeds, and by the time they reach the vibrating cantilever they can be sensed separately. Heating cleans out the sensor for repeated use.

Parts per million of many vapours can be can be detected, and sensitivity reaches parts per billion with heavy molecule like ethylbenzene.

Details of M&NEMS were presented at the European MEMS Summit earlier this month.

steve bush

Bad Q3 for Taiwan foundries

September 28, 2015

david manners

Q3, traditionally the industry’s strongest quarter, will not be a good quarter for the Big Three Taiwanese foundries, reports Digitimes Research.

The combined revenues of TSMC, UMC and VIS (Vanguard International Semiconductor) will be 0.8% down q-o-q and 3.7% down y-o-y.

Q3 revenues are expected to be $8.03 billion compared to Q2’s $8.09 billion and the $8.33 billion of Q3 2014.

The turndown would have been worse were it not for a rise in ASPs due to an increase in the proportion of advanced (sub45nm) processes in the the mix.

Digitimes notes that TSMC started to record 16nm revenues for the first time in Q3.

See also: TSMC forecasts sales fall

david manners

AMS extends analogue foundry business with scalable process

September 28, 2015

richard wilson

AMS continues to invest in and extend its analogue foundry business.

AMS Fab B analogue foundry, top right

Last month the Austrian semiconductor maker announced a government partnership in the US to build a new 8-inch fab in New York.

The company has now added to its foundry offering in Europe with an enhancement of its 0.35µm high voltage CMOS process which will offer more dies per wafer.

Called its H35 process, it makes use of voltage scalable NMOS and PMOS transistors to lower on-resistance and so reduce die area per device.

According to AMS:

“Using an optimized 30V NMOS transistor in power management applications instead of a fixed 50V transistor results in an area saving of approx. 50%.

“A 60V optimised NMOS device results in 22% less area when compared to a standard 120V NMOS transistor.”

Typical devices fabbed in this process include MEMS drivers, motor drivers, switches and power management ICs.

The foundry is automotive (ISO/TS 16949) and medical (ISO 13485) certified.

According to Markus Wuchse, general manager of ams’ Full Service Foundry division, the company ios one of the first foundry’s to offer scalable HV transistors.

“Our process design kit as well as our high voltage (HV) process expertise enable our partners to optimise their HV integrated circuits towards area and on-resistance, which immediately results in more dies per wafer,” said Wuchse.

The set of voltage scalable transistors including device layout generator (PCells), simulation models, verification rule decks for Calibre and Assura as well as documentation such as Design Rules and Process Parameters documents can be downloaded by registered users from the company’s secure foundry support server.

Richard Wilson

Capacitor reliability can be improved with the right materials

September 27, 2015

richard wilson

Although not all applications are safety critical or mission critical, reliability is still a vital consideration for many electronic products. Making informed choices at the component selection stage can help ensure the product will perform correctly over its intended lifetime, writes James Lewis of Kemet.

When choosing capacitors, properties such as volumetric efficiency, frequency stability, temperature rating or equivalent series resistance are often the primary factors that govern technology selection. In these cases, understanding factors affecting lifetime can help engineers ensure the product will deliver the required reliability.

On the other hand, a long operational lifetime may be a key requirement of the end product and ultimately may determine device selection.

Capacitor manufacturing processes such as screening, or processes to control the purity of materials or components, can provide a higher assurance of reliability that allows engineers to reduce the number of capacitors in-circuit and hence reduce solution size and cost without compromising reliability.

Capacitor Properties

Capacitors made with metallised polyester or polypropylene film, for example, are known to have a long operational life. High-voltage or high-temperature properties make these devices ideal for applications such as automotive electronics or lamp ballasts, while self-healing helps to overcome the effects of small impurities in the dielectric that can lead to short-circuit failures.
On the other hand, as these weaknesses heal the total available capacitance begins to drop and the equivalent series resistance (ESR) starts to rise. This ultimately governs the lifetime of the device. Using high-quality materials and dielectric-manufacturing processes can minimise defects leading to a slower rate of self-healing.

In alternative-energy applications, where low ESR is particularly desirable to minimise energy losses, it is possible to verify operational lifetimes of several decades, even when capacitors are operated at temperatures of 70°C or above.

Aluminium capacitors cover a number of different types of construction, each of which has very different lifetime performance. Wet-electrolyte capacitors, for example, have a well-defined and understood wearout mechanism. The electrolyte is mildly acidic, and will therefore degrade the dielectric over time.

On the other hand, the electrolyte also provides the oxygen necessary to re-grow the dielectric. This is why it is important to consider the “shelf-life” of a wet aluminium electrolytic capacitor that has not been powered—whether on a shelf or on a board.

Figure 1: X5R and X7R MLCCs combine nickel-based BME and doped barium titanate dielectric.

An interesting fact is that aluminium capacitors with a diameter of 30mm or more tend to have a more neutral electrolytic, rather than acidic, and so can have shelf-lives of two to four years at relatively moderate conditions. These figures, of course, vary by electrolyte used in each product family.

Solid “aluminium polymer” or “organic polymer” capacitors, on the other hand, have very different lifetime characteristics.
These devices have no electrolyte in the finished product. Instead the cathode is a solid conductive polymer material. This results in exceptionally long operational lifetime under rated conditions, which can be close to that of other solid capacitors.

Some datasheets describe the endurance of these types of devices in terms of properties such as capacitance change, ESR and appearance after 1,000 hours of operation.

It is important to note that the 1000 hours does not represent the capacitor’s operational life. Rather, this endurance testing is similar to the types of accelerated life testing that is typically used to qualify passive components.

As far as commercial-grade ceramic capacitors are concerned, the typical electrode system is a base metal electrode (BME) system, see figure 1, that primarily utilises nickel.

Compared to the earlier precious metal electrode (PME) systems, BME allows higher voltage stress capability. Popular X7R and X5R type dielectrics today are based on barium titanate, with additives such as manganese dioxide that coexist with the BME chemistry and prevent reduction of the dielectric by the firing processes applied to the capacitor during manufacture.

Improvements in dielectric composition have greatly increased the reliability and life of ceramics.

Tantalum Capacitor Reliability

Capacitors made with a tantalum dielectric have an exceptionally long operational life. Being a completely solid device, there is virtually no wear-out mechanism.

The most common failures for tantalum-based devices are so-called “turn on” failure. This can occur where a step-voltage is applied and the capacitor is able to draw a large initial current. This can activate a defect in the dielectric, which may cause device failure in the event that the dielectric cannot heal.

Polymer-tantalum devices benefit from a pronounced self-healing capability, and are known to be robust against this type of failure. Studies have shown that the lifetime of the capacitive elements may be in the hundreds or even thousands of years. This is likely to be considerably longer than the lifetime of other materials used in capacitor construction, such as epoxies.

Capacitor manufacturers tend to screen tantalum capacitors to identify potentially weaker devices, by applying tests such as voltage and current surge tests in a controlled sequence.

However, it is worth noting that the capacitors can be weakened by stresses introduced due to coefficient of thermal expansion (CTE) mismatches between constituent materials: hence reflow soldering conditions and the number of reflow cycles the capacitor is subjected to during final product assembly can affect the susceptibility to device failures.

On the other hand, the voltage rating of the device, relative to the applied voltage, can significantly influence capacitor lifetimes generally.

For this reason, recent development of polymer-tantalum capacitors has focused on realising higher voltage ratings such as 63V and higher for use with commonly used supply voltages such as 24V or the 28V avionics rail.

James C. Lewis is technical marketing director, Kemet.

Richard Wilson

Research cools solar cells for efficiency boost

September 25, 2015

richard wilson

Solar cells work more efficiently when they are cooled, but sitting the the sun all day, it is not always easy to achieve this.

Stanford School of engineering graduate students Linxiano Zhu, Shanhui Fan, a Professor of Electrical Engineering and grad student Aaswath Raman on Friday, October 10, 2014. ( Norbert von der Groeben )

Researchers at Stanford University in the US have come up with a transparent overlay material that increases efficiency by cooling the cells even in full sunlight.

The material works by radiating heat away from the solar cells.

The researchers used a patterned silica material laid on top of a traditional solar cell. The material is transparent to the visible sunlight that powers solar cells, but captures and emits thermal radiation, or heat, as infrared rays.

According to Shanhui Fan, a professor of electrical engineering at Stanford: “Our thermal overlay allows sunlight to pass through, preserving or even enhancing sunlight absorption, but it also cools the cell by radiating the heat out and improving the cell efficiency.”

When it was tested on a custom-made solar absorber, a device that mimics the properties of a solar cell without producing electricity, it cooled the underlying absorber by as much as 23 degrees Fahrenheit.

“For a typical crystalline silicon solar cell with an efficiency of 20%, 23 deg F of cooling would improve absolute cell efficiency by over 1%, a figure that represents a significant gain in energy production,” said the researchers.

The same technology could be applied to other systems that need to be cool but also exposed to the visible spectrum of sunlight.

“Say you have a car that is bright red,” said Linxiao Zhu, co-first-author of the paper. “You really like that colour, but you’d also like to take advantage of anything that could aid in cooling your vehicle during hot days. Thermal overlays can help with passive cooling, but it’s a problem if they’re not fully transparent.”

That’s because the perception of color requires objects to reflect visible light, so any overlay would need to be transparent, or else tuned such that it would absorb only light outside the visible spectrum.

“Our photonic crystal thermal overlay optimises use of the thermal portions of the electromagnetic spectrum without affecting visible light,” Zhu said, “so you can radiate heat efficiently without affecting colour.”

The work by Shanhui Fan, a professor of electrical engineering at Stanford, research associate Aaswath P. Raman and doctoral candidate Linxiao Zhu is described in the current issue of Proceedings of the National Academy of Sciences.

Richard Wilson

Research cools solar cells for efficiency boost

September 25, 2015

richard wilson

Solar cells work more efficiently when they are cooled, but sitting the the sun all day, it is not always easy to achieve this.

Researchers at Stanford University in the US have come up with a transparent overlay material that increases efficiency by cooling the cells even in full sunlight.

The material works by radiating heat away from the solar cells.

The same technology could be applied to other systems that need to be cool but also exposed to the visible spectrum of sunlight.

“Say you have a car that is bright red,” said Linxiao Zhu, co-first-author of the paper. “You really like that colour, but you’d also like to take advantage of anything that could aid in cooling your vehicle during hot days. Thermal overlays can help with passive cooling, but it’s a problem if they’re not fully transparent.”

“Our photonic crystal thermal overlay optimises use of the thermal portions of the electromagnetic spectrum without affecting visible light,” Zhu said, “so you can radiate heat efficiently without affecting colour.”

Richard Wilson

Marvell to lay off 17% of work-force as it re-positions mobile

September 25, 2015

david manners

Marvell appears to be pulling out of mobile to focus on IoT.

Weili Dai, president and co-founder Marvell

The company is to lay off 17% of its 7,000 employees. The lay-offs will hit staff in its mobile operation, they will cost $100-130 million and will save $170-220 million a year.

Mobile produced $122 million revenues last year for a profit of $13 million.

Marvell is involved in an investigation into its accounting procedures.

In an SEC filing, Marvell stated:”The investigation consists of a review of certain revenue recognition issues in the second quarter of fiscal 2016 and any associated issues with whether senior management’s operating style during the period resulted in an open flow of information and communication to set an appropriate tone for an effective control environment.”

Marvell overstated of revenue for the financial quarter ending on July 31 by 8-9%. It says that it will file its financial results late and they will show a $382 million loss. The company’s shares have fallen 38% this year.

david manners

Marvell to lay off 17% of work-force as it re-positions mobile

September 25, 2015

david manners

Marvell appears to be pulling out of mobile to focus on IoT.

Weili Dai, president and co-founder Marvell

The company is to lay off 17% of its 7,000 employees. The lay-offs will hit staff in its mobile operation, they will cost $100-130 million and will save $170-220 million a year.

Mobile produced $122 million revenues last year for a profit of $13 million.

Marvell is involved in an investigation into its accounting procedures.

david manners

Infineon OPTIGA security certified to TPM 2.0

September 25, 2015

david manners

Infineon OPTIGA security certified to TPM 2.0

The German Federal Office for Information Security (BSI) has certified Infineon’s OPTIGA technology to TPM (Trusted Device Module) 2.0 standard.

TPM 2.0 is the most recent version of the standard which addresses the security requirements of a growing number of IoT devices.

Trusted computing based on TPM root of trust hardware provides protection for such devices as gateways and routers used in smart homes, mobile devices as well as connected industrial and automotive systems.

The system offers security from basic authentication products to advanced implementations for protecting integrity, authenticity and confidentiality of information.

david manners

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