Tag: Hermetically Sealed

High-voltage/high-current circuits in antenna, radar, rangefinder, satellite, military ground vehicles, shipboard, and other aerospace and defense applications — as well as 270-VDC aircraft power systems — pose unique power-management challenges. Today, it’s critical to design solutions that can handle high power more efficiently in less space. Power distribution for electric vehicles, charging stations, battery systems, and solar and wind applications pose similar challenges.

This discussion simplifies a designer’s task by describing how advanced relays and contactors can handle difficult power-distribution demands — and introduces a tool for navigating various contactor and relay features to facilitate selection.

Power-distribution technology comes in a variety of flavors. Many open-air switch designs can handle only several hundred volts. However, smaller, lightweight, hermetically sealed devices using either a gas with good dielectric properties or a vacuum can switch up to 70 kilovolts (kV).

For contactors, increased contact size and pressure, combined with special alloy materials, enable high current management up to 1,000 A. Integrating built-in Hall-effect current sensors into the contactor creates “smart” current-sensing versions of these devices.

Read more: Power Distribution for High-Voltage/High-Current Circuits Creates Challenges

Aluminum electrolytic capacitors have been a mainstay in electronic power circuits for their ability to provide large bulk storage, high voltage and high energy density. However, in a growing number of applications, their on-board height has become a key limiting factor. Historically speaking, capacitors have typically been among the tallest components on the circuit board. The advent of surface-mount (SMT) capacitors, across multiple dielectric technologies, has helped to shrink the height of a loaded board. In order to achieve high capacitance or voltage using SMTs, it is often necessary to bank multiple capacitors on the PCB. Unfortunately, this approach consumes a lot of valuable board real estate, especially in applications that require high capacitance for holdup.

The fairly recent development of flat, rectangular (prismatic), aluminum electrolytic capacitors is helping circuit designers achieve low profiles, space and weight savings, especially at high application voltages.

The challenge of low profile and high energy density
While most dielectric technologies employ multilayer technology to achieve low-profile SMT chip packages, conventional aluminum electrolytics use wound capacitor elements within their SMT package types. These cylindrical windings are placed in cylindrical metal containers and mounted vertically to a rectangular mounting pad. For this reason SMT aluminum electrolytics have come to be known as V-chips, short for vertical chips.

The cylindrical packages also contain a liquid electrolyte, which must be sealed into the device. Rubber or composite seals prevent this electrolyte from escaping. This design tends to be inefficient for SMT devices, as the percentage of overall capacitor volume taken up by the seals increases as total package volume decreases. This is a key point. For typical SMT aluminum electrolytics, up to 60% of the capacitor’s volume may be space-wasting end-seal gaskets and related materials!

Another consideration is the lifespan of the individual components. Even with quality end seals, cylindrical electrolytics gradually experience a long-term loss of electrolyte, a condition known as dry-out. Loss of electrolyte results in a corresponding loss of capacitance and increased equivalent series resistances (ESR). For that reason, conventionally sealed aluminum electrolytic capacitors have typically been limited to consumer, industrial and non-critical military and aerospace applications. For mission-critical military, aerospace and down-hole applications, circuit designers have historically specified higher-priced hermetically sealed wet-tantalum capacitors.

The solution to the historical limitations of electrolytics is to approach component construction with an entirely different device design. Prismatic aluminum electrolytic capacitors can be designed to deliver high bulk capacitance, in low profile, high energy-density packages that eliminate dry-out. This advancement is accomplished by replacing those space-wasting flexible seals with robotically laser-welded seams. The laser welds also do a far better job of preventing electrolyte loss, thus greatly extending component life. These new aluminum electrolytic package configurations allow engineers to improve reliability while saving space, weight and even loaded-board cost.

Read more: A better aluminum electrolytic capacitor: Here is what you need to know about the latest flat prismatics

Timing solutions are critical to today’s electronics. Many engineers rely on the internal real-time clock (RTC) functionality that comes embedded in microcontroller units (MCUs) and system on chips (SoCs). Those functions rely on crystal, crystal oscillator (XO), and temperature compensated crystal oscillator (TCXO) options as external frequency sources that translate into system clocks, which then determine the accuracy of the RTC function. In some cases, it may be more beneficial to use RTC module timing solutions instead.

RTC Module Timing Solutions
This paper identifies the barriers and benefits of various timing solutions and offers guidance on when and why an RTC module timing solution may be a better choice:

The Criticality of Timing Solutions
The Capability Range of Common Timing Solutions (Crystals, Crystal Oscillators, Temperature Compensated Crystal Oscillators, Real-Time Clock Modules)
The Pros and Cons of Switching to RTC Modules

What is a RTC module?

• RTC stands for “Real Time Clock”. These RTC modules are integrated circuits that measure time and date. RTC modules are incorporated in electronic devices which need to keep an accurate track of time.

How does a RTC module work?

• An RTC module records the passage of time by counting the cycles of an oscillator. Most RTC modules use a “crystal oscillator”, while others use micro resonators on the RTC’s silicon chip.

What is the use of crystal oscillators in microcontrollers?

• Crystal oscillators are used to keep track of time by using the mechanical resistance of a vibrating quartz crystal to create an electrical signal of constant frequency. Crystal oscillators have a frequency of 32.768 kHz, the same frequency used in quartz watches and clocks.

Where are crystal oscillators used?

• This type of quartz crystal oscillator is commonly used in quartz watches, radio transmitters and receivers, and other digital integrated circuits. Most consumer goods with a time-keeping function also contain crystal oscillators, such as TVs, personal computers, toys, digital cameras and phones.

Read more: Is an RTC Module Timing Solution Right for Your Project?

Used from test and measurement equipment to medical electronics, automotive, household appliances, aerospace, telecom, consumer electronics, HVACs, general purposes, and much more, Reed Switches offer product designers a reliable, hermetically sealed switching solution.

The Reed Switch’s hermeticity lends itself to more switching applications than any other switching device. Its ability to be used as a complete sensing component by itself or the ease of packaging it into special sensing requirements is done without any complicated process or high tooling costs.

There are so many existing and potential applications for Reed technology that it would be difficult to discuss them all. However, this paper breaks down some of the basic features and applications by market to provide insight and new considerations for your present and future projects.

Read more: Reed Switch & Sensor Technology for Technology Applications

If used correctly, a Reed Relay is a superbly reliable device. The switch contacts are hermetically sealed, so do not suffer from oxidization or contamination in the same way as an open electromechanical relay. In reality, though, relays are often considered slightly mundane and little thought is given to them. This sometimes leaves them vulnerable.

This concise technical guide will help you to maximize the reliability of your designs. Topics include:

• Former-less Coils
• Magnetic Interaction
• Temperature Effects
• Contact Abuse
• ‘Hot’ Versus ‘Cold’ Switching
• Why Place a Diode Across a Relay Coil

Read more: Maximizing the reliability of Reed Relays in your designs

International Rectifier HiRel Products (IR HiRel), an Infineon Technologies company, addresses the problem with fourteen new QPL-qualified, radiation-hardened (rad-hard) SupIR-SMD MOSFETs housed in a direct-to-PCB PCB mounting package. SupIR-SMD is a solution for high-performance space power systems used in missions ranging from satellites to space vehicles and more.

“Space applications demand high-reliability power electronics that perform to specification in the harshest environments. They must be capable of withstanding severe thermal, mechanical and radiation conditions with expected lifetimes of 15 years or longer. SupIR-SMD is a superior package solution for thermal expansion and heat transfer,” said Andrew Popp, director of marketing at IR HiRel.

PCBs for space
Space is notoriously hostile to electronics. Electronic components used in space-borne applications are primarily subjected to space radiation, known as a single-event effect, or SEE, caused by electrons and protons trapped in Earth’s magnetic field. And yet PCBs in space must provide continuous performance and high reliability in ecommunication satellites, remote sensing satellites, navigation satellites, and other planetary satellites.

Radiation is hardly the only challenge. Space-grade PCBs are subject to shock and stress during space flight launch. Vacuum is a problem too; it makes it difficult for PCBs to dissipate heat; if not handled properly, they may develop cracks and solder joint problems.

The most important factor for space hardware is reliability, as it is impossible except in extreme cases to repair it. PCB design can have a direct impact on the reliability of the spacecraft.

Satellite and spacecraft avionics increasingly combine high-power with RF transmissions. All these functions define unique requirements on the design, layout, and construction of a PCB, but also on the selection of a suitable dielectric material for the purpose, the number of layers in the stack-up, routing, track geometry and grounding.

Nowadays electronic systems require high levels of performance, starting with high-speed digital circuits, up to RF power amplifiers and high power LED modules, in all these fields the choice of material is definitely a serious goal for the designer to reduce possible problems related to heat dissipation and electromagnetic interference.

The choice of good material is generally a compromise between cost and performance. Some parameters to consider are signal integrity, noise immunity, and heat dissipation. The dielectric constant is a starting point for many selection processes for PCB materials, as well as the coefficient of thermal expansion (CTE) and the dissipation factor.

Good signal integrity also makes it possible to evaluate a number of factors such as electromagnetic compatibility requirements, and EMI, electromagnetic interference requirements. The choice of materials ensures a perfect solution to limit crosstalk noise and, at the same time, the losses that can compromise the functioning of the system.

The CTE shows the speed at which a PCB material expands after heating. CTE is a way to express the amount of volume change of a material during a temperature change, expressed in parts per million per degree centigrade. Most substrates have a higher CTE than copper. It can cause interconnection problems when the PCB temperature increases.

New package
The misalignment of the coefficient of thermal expansion (CTE) between the PCB and the hermetically sealed surface mount poses two fundamental challenges: maintaining reliable solder joints at the interface and preserving the sealed integrity of the hermetically sealed power MOSFET. Even small CTE mismatches can cause thermal stress-induced interface fractures.

The property of materials to expand with temperature is well known. It occurs in all 3 dimensions. This expansion gives rise to the same tension that can cause assembly problems. The change in length of a material due to a change in temperature is defined by the equation:

Read more: SMD Package for Rad-Hard Power Electronics

This White Paper opens with a brief background into the history of space satellites. The focus then shifts to the NASA EEE-INST-02 and how it is a perfect example of how to understand the function and importance of capacitors. After showcasing a screening protocol, the author then dives into more of the specifics of what the screening and qualification processes entail. The paper then gets into a case study, offering specific capacitor requirements and how several Quantic Evans series’ would serve the needs of this designer well. Finally, the paper discusses the “hermetic seal” requirement and how Quantic Evans tantalum cases not only are hermetically sealed, but also shielded from radiation. A similar discussion is then had regarding shock and vibration, mission lifespan, and storage life, wrapping up with a brief statement on the evolution of capacitor design.

Read more: Specifying a Capacitor for Space-Based Applications

Semiconductors are increasingly finding their way into a variety of medical devices, after years of slow growth and largely consumer electronics types of applications.

Nearly every major chipmaker has a toehold in health care these days, and many are starting to look beyond wearable such as the Apple Watch to devices that can be relied on for accuracy and reliability. Unlike in the past, these chips also are being developed at relatively advanced processes, several generations behind the leading edge so that the processes have matured sufficiently.

Included in this mix are custom ASICs, as well as off-the-shelf analog and digital chips. And they span everything from low-power ICs for medical implants to high-performance accelerators that process images for diagnosis.

“Right now, chips manufactured at 28, 20, and 16nm are in production within medical equipment,” said Subh Bhattacharya, Health care & Sciences lead at Xilinx. That can include anything from a 510(k) device, which is demonstrated to be safe and effective, to De Novo and pre-market approval (PMA) classifications, which are further along. Many of these applications are Class II, which means they have a moderate to high risk for the user, but there are also some Class III applications, such as automated external defibrillators and infusion pumps.

As of today, the main uses of electronic medical devices are for research, collecting of public-health data, maintaining and accessing patient records, and patient health care. But the use of semiconductors in these devices is widening as devices shift into monitoring, diagnosis, and treatment via surgery or other therapeutics, such as drug delivery and stimulation of nerves in neurotechnology. Monitoring systems also include implanted clinical devices used at the patient’s home to send data back to doctors or monitoring services about vital-signs systems from sensors physically applied to the patient.

The over-arching goal in medical devices is always to make health care accurate, effective, convenient, accessible, and affordable, while making treatments safer and less invasive. Those improvements focus on using less power in a smaller form factor, and getting the signals out securely to their destinations. Sensors, analog-to-digital converters, RF, and microcontrollers are all key elements. So are image and signal processing. Increasingly, AI is being added into these systems, as well, to make monitoring and diagnosis tasks less complex, faster, and hopefully more accurate than humans.

Device form factors
Medical devices for patient health care take many forms, from tiny ingestible and implantable devices to large biomedical diagnosis and treatment machines. Devices for the consumer market are distinct from clinical/professional devices in that they may cost less and be less accurate or reliable.

What’s less obvious is the fine line between them. Devices used in clinical settings can have similar but better quality components and system design. But the lines are blurring as chips are used in more devices, including:

Externally worn devices. These include wearables, hearables (fitness and vital sign trackers; newer consumer watch/smartphone systems offer ECG tracking, sleep apnea detection, arrhythmia detection, and blood oxygen tracking); disposable sensors (for example, in glucose monitoring); and e-skin for stimulating nerves, adding a sense of touch in prosthetic hands. Some of these devices are consumer devices (over the counter — anyone can buy the device without a doctor’s prescription) or clinical (prescribed by medical professionals).
In-body devices. This group includes implants, such as pacemakers, cochlear implants, and neurostimulators. These devices have to be in hermetically sealed packages, which may be ceramic or metal. The wireless communication and signal acquisition and processing has to be extremely low-power. Electromagnetic interference (EMI) is a hazard to implanted devices. Also in this group are ingestibles, which have to be the size of pill or capsule, and made of biocompatible materials that can withstand the GI tract while housing MCUs, sensors, memory, and power supplies. Some ingestible sensors can communicate in real time with the outside world.
Clinical patient diagnosis, care, and treatment. These are predominantly monitoring systems, including sensors connected to in-hospital networks that monitor patients’ vitals. Also in this class are lifesaving machines, such as ventilators and defribrillators, surgical equipment, robotics, and diagnostic equipment (CT scans, MRIs, X-rays). Some clinical devices are designed to be used by patients at home and some have an implantable or wearable version. Blood analyzers and assays for diagnosis are progressing.
On top of these are some new applications, as well.

Read more: Rising Fortunes For ICs In Health Care

Wireless and battery-free radio sensors are proving increasingly beneficial as the Industrial Internet of Things matures. They can be used directly on moving parts or in hermetically sealed environments, for example to measure the flow, pressure and temperature of liquids or gases. Above all, industrial companies save themselves time-consuming and cost-intensive cabling.

However, it is of crucial importance that wireless sensors employ energy harvesting, rather than being powered by batteries. This is because replacing a single battery in an industrial environment costs between $250 to $500 US dollars. Although the actual battery exchange happens quite quickly, the travel, locating, device-testing, and documentation increase the hourly costs enormously. Very often, batteries are said to have a service life of two to five years, but in practice they are often replaced every one to two years in order to avoid early failures.

Resource saving and environmental protection are also becoming increasingly important: the prices for copper are steadily going up and the harmful components as well as safety aspects of batteries are a serious problem. A sustainable solution is needed that takes both the financial aspect and the damage to the environment into account.

There is a more sustainable way for wireless sensors: sensors that obtain their energy from movement, light, and temperature differences according to the principle of energy harvesting. This means that they neither require cables nor batteries for smooth operation. Therefore, they can be flexibly mounted directly on moving parts. The combination of radio and energy harvesting enables new applications entirely without maintenance requirements and battery waste.

Sensors in quality control

Quality monitoring is a key aspect of the production process in order to ensure that the final product meets predefined parameters. To achieve this goal, a variety of parameters must be monitored, such as environmental factors like temperature, humidity, and air quality; process factors like speed, force, pressure, and temperature; or material factors like the starting materials used.

Many of these parameters are suitable for automated monitoring with the help of sensors. Ideally, sensors can be optimally integrated into existing production processes and require neither special training nor do they cause follow-up costs in ongoing operations.

Maintenance-free process monitoring

The aim of process monitoring is to ensure that a defined production quantity is achieved, taking into account various parameters such as the required time, material and personnel. Deviations in the production process must therefore be detected at an early stage and failures avoided. The integration of wireless sensors in production offers decisive advantages: wireless sensors can be used, for example, in hermetically sealed environments such as pipelines to measure the flow, pressure, and temperature of liquids or gases.

Read more: Battery-free wireless sensors conquer the IIoT

A hermetic seal is an air tight seal that is used to prevent contaminants such as solids, liquids, or gases from entering a package. Hermetic seals used in a wide range of applications including semiconductor electronics, thermostats, optical devices, MEMS, and switches. Electronic parts can be hermeticly sealed to ensure water vapor, dust particles or other particles do not enter package to ensure proper operation of the component. Many Semiconductor devices and components require hermetic seals to be used in High Reliability (Hi-Rel) applications.

Some RF and Microwave Parts that are often available with Hermetic Seals are:

Coaxial Connectors: Hermetically sealed RF connectors are used in a wide range of applications where entry of liquid, air or gas has to be avoided.

RF Semiconductors: Many Hi-Rel Applications like Space, Military and Critical communications require semiconductors ICs to be Hermitically Sealed.

Hermetically Sealed Relays: The device is sealed into a metal cover via welding to ensure zero intrusion of any form of materials. This is done to make the relay free from the impact of ambient conditions such as harmful gas, humidity, dust, etc.

Hermetically Sealed MEMS: To secure the operations of MEMS devices, it is advised to design a hermetically sealed package which protects the device from wet environments. There are multiple ways in which MEMS devices can be hermetically-sealed. In the one show below, a lid (metal) is placed on a ceramic package which is hermetically sealed via seam welding.

How do you Test the Hermeticity of a Seal?

The most common method used to determine the hermeticity of a seal is to measure the rate at which helium escapes from a package that has been pressurized with helium. As stated by MIL-STD-883C, a hermetic package is one in which the leak rate of helium after pressurization is below a rate specified with reference to the package size (refer to Table 1). The sealed package is placed in a chamber which is pressurized with helium (helium bomb) to a level depending on the package volume.

Read more: What are Hermetically Sealed Packages?