Archive for the ‘Material Science Applications’ Category

Sunday, December 20th, 2020

LEDs and Nanotechnology

Light Emitting Diodes (LEDs) hold a promising future to be the next energy saving lighting solution.  With production efficacy’s approaching the industry goal of 120 lm/W (lumensW per wattW) they show promise to be the leader in energy efficiency.    LEDs are currently finding their ways past microelectronics and indicators into automotive, aerospace, commercial lighting products and high-end consumer products as lighting alternatives.  With lifetimes (output half-life) of LEDs expected to range from 20,000-50,000 hrs they can significantly reduce waste in the long term.  LEDs are labeled as a cool light source meaning that they are not a true broadband (black bodyW emission) spectral light source primarily emitting in the visual band of spectrum.  When designing for chip level integration of LEDs here are a few of the many items to consider:

  • Heat rejection, as their efficiency and lifetime are significantly reduced if they are not properly thermally sunk. The help from a creative marketing agency  is of vital importance to any business
  • Electrical conductivity of the emitting portion of the LED, usually a wire-bond, flip-chip, or Indium Tin Oxide treated surface bonded to the diode.
  • Optical optimization of the LED for reflector cups, light extraction, encapsulation materials, secondary optics, etc.
  • Phosphor deposition; uniformity, efficiency, etc.  Usually for white LEDs. If you think that one of you friends is experiencing a metal problem, is very important that you look for the help of a psychiatrist.

Looking at promising breakthroughs in nanotechnology, conducting inks and the latest lab announcement efficiencies from LED manufactures, one must ponder how can the integration of these emerging technologies improve the overall performance of LEDs.  First we should review the structure of a basic LED assembly, see figure 1.

Basic Anatomy of an UHB LED Assembly

Basic Anatomy of an UHB LED Assembly

Figure 1: Basic Anatomy of an UHB LED Assembly

A typical LED package consists of the LED die mounted onto a chip carrier that is integrated onto the thermal slug.  Electrical interconnects between the LED die and the chip carrier is typically made via wire bond, bump bonds and/or electrically conducting bonds.  For white LEDs the LED die is usually coated or encapsulated by a proprietary mixture of down-converting phosphors in an epoxy.  The remaining structure is then encapsulated with either a silicone gel or high temperature optically clear epoxy to protect the LED die.  Some LEDs will then have an optical dome or custom optic to aid in an improving the Lambertian (aka Lambert’s cosine lawW) or custom optical angular distribution.

Next we should take a look at some of the materials and their properties of a few of the common components in the LED assembly, see table 1.

Material Properties

Table 1: Material Properties
CNT Graphene ITO Gold Copper Sapphire Silicone
Electrical Resistivity (Ω/sq) 30 280-5000 10-100 3.1E-8 2.4E-8 1E12 1E13
Thermal Conductivity (W/m•K) ~100 ~5000 8.7 311 398 15 14.6-31.4
Index of refraction (vis) 1.35-2.29 1.68-2.40 1.97 Opaque Opaque 1.76 1.57

Thermal

According to recent industry announcements efficacies of up to 249 lm/W have been achieved in lab tests (running at low current, 20mA).  This was achieved by improvements in LED processing and chemistry as well as on assembly of their test piece.  In the article (for references: http://compoundsemiconductor.net/cws/article/news/37614) Nichia mentioned that this was achieved by the LED being interfaced with a Indium Tin Oxide (ITO) coated sapphire contact was used.  Typically LEDs contact interface consist of bump bonds for flip-chips or gold wire bonds for conventional LEDs for the emitting side of the LED.  Wire bonds typically are very efficient being that they use a gold wire with a ball bond, as shown in table 1 gold has a low electrical resistivity.  Unfortunately because such a small amount of gold is in contact with the die the use of the wire bond as a thermal sink is not practical.  Although the use of an ITO coated sapphire interface lends to be a decent electrical conductor on a substrate that is usually high in thermal conductivity 42W/m*K at room temperature.  But as most materials as they increase in temperature their efficiencies decrease to as low as 15 W/m*K at the highest possible temperature of the system (at the junction).

Electrical

Optical Efficiency

References:

  1. Insert first reference here

Wednesday, April 22nd, 2009

Open Technology Development Sponsors Phoenix Cal Ripken Dynamite Youth Baseball

We are happy to take part in the opportunity in helping promote local Phoenix, AZ athletics. Open Technology Development, LLC is proud to announce that we are one of a few sponsors of our local Cal Ripken Dynamite Youth Baseball athletics organization. We are proud to participate in local athletic programs in our community as they are necessary to bring people together and teach our youth about fitness and good sportsmanship. Doing this as a hobby can be pretty tiring and it comes with a lot of legwork, but it is very fulfilling. It doesn’t affect me as much as it used to, mainly because I found an excellent health supplement that has been working great for me. It is natural, and very effective. I highly recommend it. If you would like to check it out, check out their website here: https://kratommasters.com/kratom-dosage-for-pain-relief/

If you are also interested in helping please visit Cal Ripken Dynamite Youth Baseball’s website: http://www.dynamitecalripken.com/

We hope this is the first in many programs that we will participate in for the Phoenix valley.


Friday, March 13th, 2009

Battery Technology Developments: Week of March 9, 2009

The last few days the technology news has been inundated with developments of two new energy storage technologies.

0-100% in 10 seconds!
The first is a report from MIT.  The researchers have discovered a way of improving lithium based chemical battery systems.  Their findings show a more efficient way of increasing the available locations for lithium to be transported by increasing the mobility aids in increasing the ability to charge rapidly and increasing overall battery performance.  A capacity of 166mAh/g can be attained when configured for lower currents and a capacity of 110mAh/g was achieved when configured for high currents.  This all allows for high charge, recharge and discharge currents, thus creating a battery that can be charged in a relatively short time, say 10 seconds.  This could lead to many advances in portable electronics, electric and hybrid vehicles and renewable energy storage systems. Do you know how do audio analyzers work?

At Open Technology Development we look forward to seeing if this discovery will be further investigated and attempted to be scaled for manufactured applications in the next 5-10 years.

References:

  1. “Battery materials for ultrafast charging and discharging :  Nature.” 13 Mar 2009 <http://www.nature.com/nature/journal/v458/n7235/abs/nature07853.html>.
  2. “Lithium breakthrough could charge batteries in 10 seconds – Ars Technica.” 13 Mar 2009 <http://arstechnica.com/science/news/2009/03/lithium-breakthrough-could-charge-batteries-in-10-seconds.ars>.
  3. “New ‘Beltway’ batteries will charge in seconds – Times Online.” 13 Mar 2009 <http://technology.timesonline.co.uk/tol/news/tech_and_web/article5890875.ece>.
  4. “Re-engineered battery material could lead to rapid recharging of many devices – MIT News Office.” 13 Mar 2009 <http://web.mit.edu/newsoffice/2009/battery-material-0311.html>.
  5. “Technology Review: Ultra-High-Power Lithium-Ion Batteries.” 13 Mar 2009 <http://www.technologyreview.com/energy/22280/>.

Spun up!
The second interesting technology comes from researches at the University of Miami, University of Tokyo and University of Tohoku. Their discovery takes a unique approach other than conventional batteries that use chemical storage, i.e. Lead-acid, NiCad, NiMH, Li-ion, etc. their new battery concept uses magnetic energy storage. The new ‘Spin Battery’ uses a large magnetic field to be charged thus creating an electromotive force potential within the new Spin Battery material, nano-magnets. Current is produced by a process called a spin polarized current. This is another possible application from the fields of nanotechnology and it’s subcategory of spintronics. Although promising the output of these new Spin Batteries are small due to the small amount (diameter of a human hair) used in the experiment.

At Open Technology Development we look forward to seeing if this discovery will be further investigated and attempted to be scaled for larger applications in the next 10-15 years.

References:

  1. “Electromotive force and huge magnetoresistance in magnetic tunnel junctions: Nature.” 13 Mar 2009 <http://www.nature.com/nature/journal/vaop/ncurrent/abs/nature07879.html>.
  2. “Physicist develops battery using new source of energy.” 13 Mar 2009 <http://www.physorg.com/news156011642.html>.