Russian Government Promotes LED Lights Programme

It is reported that Russian Railway Corporation has scheduled to purchase LED lights for retrofit of Russian railway lighting project, observed by Sergey Borovkov, the business partner of Lighting Business Consulting LLC. 

Russian Railway CorporationRZD, one of the largest Russian stated operated purchaser, had planned this LED lights replacement project since 2009. Till now LED lighting for railway station and rail track has been completed already and will be still ongoing.

LED lights fixtures price is 50 times of traditional bulbs as well as15 times of conventional fluorescent tubes. 

It might take a long time for most consumers to select LED lights instead of traditional lighting products. The price of LED lighting fixtures has become the primary consideration. And fortunately, substantial price fall of LED lights products motivated LED lights development. Recently Russian government has carried out a series of measures to promote LED lights project in Russia. As one member of emerging markets, Russia played one important role in economic development. To be brought in line with international standards, Russian government has enacted law of energy strategy outline in 2009, stipulating sales ban of over 100watts bulbs in 2011; of more than 75 watts bulbs in 2013, and of over 25watts in 2014, claiming traditional bulbs withdrawal from the market. Moreover, market capacity of fluorescent tubes in Russia is still huge, while waste recycling issue has become one Gordian knot. In the long run, environmental issues will be the bottleneck of fluorescent tube development. 

In accordance with Analyses of Russian market, LED lighting fixtures market share keeps growing, which accounts for 37% of lighting industry, among which commercial LED lighting, industrial LED lighting, office LED lighting have become the three biggest parts. It is predicted that LED lights, applied in commercial lighting, office lighting, and industrial lighting, shall increase rapidly in demand. 

What is LED Surface Texture

According to Snell’s Law, LEDs luminous efficiency depends on either internal quantum efficiency or light extraction efficiency of each component in one LEDs device, among which LED grain efficiency is the most important direct factor. Total Internal Reflection(TIR) has become the main problem to be solved.

The most common way to solve TIR problem is to change geometrical shape of LED grain. Osram has applied this technique in silicon carbide substrate system, which resulted in improvement on light transmittance. 

Nowadays one core technique to solve TIR issue is LED surface texturing. By means of modulation for LED grain geometrical surface, light refracting angle should be changed. Surface texturing processing is dedicate to altering the beam angle of light that meets the law of TIR. 

And now Wet Etching is one of the methods that has been adopted as the key of realizing surface texturing. 

What is LED Flip Chip

Flip Chip, known as controlled collapse chip connection, short of C4, is the way to interconnect semiconductor devices to external circuitry with solder bumps. The solder bumps are deposited on the chip pads on the upper side of the wafer during the final wafer processing procedure. In order  to mount the chip to external circuitry, by flip chip package, the chip is flipped over so that the chip surface aligned directly with circuit board without wire bonding, and then the solder is reflowed to complete the whole interconnection.

Here is the main processing procedures of LED flip chip package:
1. Firstly, circuit shoud be integrated on the wafer
2. Secondly, the pads should be metalized on the surface of chips
3.And then solder dots are deposited on each of the pads
4.Chips are flipped over and positioned so that the solder balls are facing the    connectors on the external circuitry
5.Solder balls are then remelted by using hot air reflow in the processing6.Mounted chip is under-filled by using an electrically-insulating adhesive

Compared with wire bonding,, the whole processing steps of flip chip package can be completed in batch so as to reduce cost and improve the speed. The resulting completed flip chip assembly is much smaller than a traditional carrier-based system; the chip sits directly on the circuit board, and is much smaller than the carrier both in area and height. The short wires greatly reduce inductance, allowing higher-speed signals, and also conduct heat better.

How to Apply PTC Thermistor in LED Tube Short Circuit Design

The latest discovery that PTC(Positive Temperature Coefficient)，one kind of positive temperature coefficient thermistor, can be applied in LED tube short circuit design.

PTC is one typical semiconductor resistance of temperature sensitiveness. Beyond the Curie Temperature, its resistance value will increase by steps 

LED Tube shortcut circuit design was previously realized by short circuit chip:

                                                   (Picture Courtesy of SYHDEE)

One big disadvantage of which, is that once the wiring mistake occurs, it might cause circuit short-cut and electronic components damage. Replacing short cut chip with PTC can solve this problem:

                                                    (Picture Courtesy of SYHDEE)

PTC should be wired in series in circuit while LED tube works. Under normal circumstances, PTC resistance value is small and so is energy loss, thus affecting little the normal working. Whereas overcurrent happens, temperature of PTC thermistor will rise up rapidly and so does PTC resistance value, automatically setting up overcurrent protection circuit. When faults removes, the power supply will be auto recovered.