Dispensing Solutions for the LED Industry UV and Thermal ... · 20 Global LED/OLED Supplement •...

Winter 2015globalledoled.com

S P E C I A L S U P P L E M E N T

Dispensing Solutions for the LED Industry

UV and Thermal Stability Protection for LEDs

• Industry News

• New Products

20 www.globalledoled.comGlobal LED/OLED Supplement • Winter 2015

Industry News

Alpha appoints Daniele Perico as Preform Manager for Europe

Alpha, the world leader in the produc-tion of electronic soldering materials, has appointed Daniele Perico as Preform Sales Manager for Europe.

Daniele will be responsible for expanding customer awareness of the potential for solder preform solu-tions, developing strong relationships with key preform customers and also providing high quality technical support.

In addition to the preform focus, Daniele will also be responsible for expanding Alpha’s presence in the European LED sector by developing knowledge of both industry trends and future customer product requirements.

Daniele has twenty five years experi-ence in the electronics assembly industry, having previously held key positions with Electrovert, Speedline and Siemens. After beginning his career with Electrovert in an applications role, he eventually moved into various European commercial roles where he enjoyed significant success.www.alpha.alent.com

Philips Lighting Electronics Mexico purchases an Ersa POWERFLOW N2

Kurtz Ersa North America, a supplier of electronics production equipment, is pleased to announce that Philips Lighting Electronics Mexico (PLEM) has purchased two POWERFLOW N₂ systems. As Ersa’s flagship machine, the POWERFLOW N₂ was specifically designed to meet the chal-lenges of lead-free.

“I selected the ERSA PowerflowN₂ because I wanted to maximize PCB production speed and minimize dross,“ said Jose Edgar Camacho Molinares, Soldering Specialist, Engineering, Philips Lighting Electronics Mexico. “The PowerflowN₂ has enabled us to increased our production speed and eliminate dross. Additionally, the PowerflowN₂ give us better hole filling in spite of using less silver / no silver content alloys.“

The POWERFLOW N2 can reduce lead-free wave solder running costs by up to 90 percent. Additionally, the machine

highlights a 16” or 20” board width, plug and play pre-heat design (Medium IR, Convection, Short IR and now with new topside Convection) and 1.8 meters of preheat standard. Additional pre-heating of up to 2.4 meters can be added if needed.www.lighting.philips.com/plem

2015 will be a transitional year for the global lighting market

Last year was a challenging one for lighting products, with most traditional technology suppliers reporting declin-ing quarterly revenues for lamps and luminaires. In contrast, many LED-only manufacturers have seen their revenues rise. This trend is expected to continue, with lamp revenues expected to increase at a compound annual growth rate (CAGR) of 1.4 percent, from $28.6 billion in 2014 to $29.9 billion in 2019. Over the same time period LED revenues are set to increase at a CAGR of 17.3 percent, while the CAGR for traditional technology declines by 7.6 percent.

Traditional technology lamp manu-facturers have had to restructure their portfolios, as traditional lighting products are replaced by more lucrative LED lamp and luminaire products. At the same time, high growth rates for LED lamps are attracting lots of competition from low-priced Chinese manufacturers – margins have been squeezed and could continue to decrease. In fact some manufactur-

ers could be forced to leave the market altogether, if they cannot find a way to compete at lower price points.

Currently, A-type LED replacement lamps – which replace the traditional technology A-lamps that are especially prevalent in the residential sector – com-prise the majority of LED lamp ship-ments and revenue in North America, Latin America and EMEA. An increasing number of manufacturers introduced T-type LED products last year, to address this large and growing market. According to the most recent IHS findings, 10.6 billion fluorescent units are currently installed in indoor commercial and industrial applications worldwide, which accounts for about half of all lamps in this sector; however, LED penetration has yet to cross 1 percent.

LED companies diversify with moves into the module market

According to the latest research from IHS, Inc., leading suppliers of LED com-ponents are increasingly diversifying, in order to produce LED modules and light engines. Many companies, known only as packaged LED providers in the past, have expanded their product offerings, and are now also supplying LED modules. The competition in this market is particu-larly diverse, not only because suppliers are located all over the world, but also because of competition from companies with backgrounds in power devices and other backgrounds.

These suppliers are moving into the module market, in order to diversify

INDUSTRY

■ Ersa POWERFLOW N2

their portfolio and protect against com-ponent LED profit margins potentially lowering further, as the packaged LED market becomes increasingly com-moditized. With Chinese companies beginning to gain share, companies in the West and Korea (among others) are moving up the supply chain to minimize the effects of this competition. With modules and light engines becoming more common, there is a growing trend for lighting companies to purchase LED modules, rather than component-packaged LEDs, in order to shorten and simplify the supply chain; however, in-house production by lighting companies is still common and will remain so.

The combined market for LED mod-ules and light engines in lighting applica-tions is projected to reach $1.3 billion in 2014, according to the latest IHS “Next Generation Lighting” report. In addition to providing insight into modules and light engines, the report also features analysis of the emerging markets for LiFi, indoor positioning and OLED.

Avnet Abacus garners award from Omron for fast growth on range of sensors, switches and relays

Avnet Abacus, one of Europe’s leading interconnect, passive, electro-mechanical and power distributors and a business unit of Avnet Electronics Marketing EMEA, a business region of Avnet, Inc. (NYSE: AVT), has picked up the award for New Distribution Partnership 2014 from Omron, a global leader in electro-mechanical and sensing technology.

Since the two companies began their partnership in January 2014, sales of Omron products through Avnet Abacus

have grown significantly, achieving the fastest growth rate ever on the portfolio by a newly appointed distribu-tor. Omron products available from Avnet Abacus include: MEMS sensors for pressure, flow, vibration and thermal applications; a wide selection of switches including tact, rocker and microswitches; and a broad range of solid-state, power, signal and automotive relays.www.avnet-abacus.eu

Cambridge Nanotherm appoints Ewald Braith as Non-Exec Director

Cambridge Nanotherm is proud to announce that Ewald Braith has joined the board as a Non-Exec Director. Cambridge Nanotherm has already started to make significant inroads into the LED market with its innovative nano-ceramic thermal management solutions for LEDs and other electronics. Ewald has now been brought on board to lend his considerable expertise to aiding the company in its growth plans.

“We’re really excited to have Ewald on board,” commented Ralph Weir, CEO. “Ewald combines high-level strategic nous with a deep knowledge of electronic design. He’s a big-hitter in terms of his achievements in the power electronics and telco markets, and exposure to semicon-ductor technologies and vertical markets. Additionally, throughout his career, Ewald has led aggressive expansion into over-seas markets. This is a world-class hire, and clearly indicates the level at which Cambridge Nanotherm is now operating.”

“I am joining the team at a very excit-

ing point, both in terms of the company’s growth and the growth of the large scale industry and market oppor-tunities. The markets for LED technologies are growing rapidly, and manufacturers are eager for effective ways to improve the competitive-ness of their products. With

its thermal management solutions Cambridge Nanotherm can and should be at the core of this opportunity. I look forward to working with the team to continue to build on the momentum already achieved, as well as helping to drive greater penetration of key high growth markets such as the US and Asia.”www.camnano.com

LED Engin adds Digi-Key distribution channel to boost global sales of its ultra-bright compact emitters and lenses

LED Engin, Inc. announces a global distribution agreement with Digi-Key, the industry leader in electronic component selection, availability, and delivery. From today, LED Engin’s LuxiGen™ emit-ters and secondary lenses are available through Digi-Key’s global websites. With over 500,000 customers, Digi-Key is one of the most popular online destinations for electronic component purchases.

LED Engin’s product portfolio includes high power LuxiGen emit-ters, which offer high efficacy and flux, color stability and lumen performance, together with ultra-efficient and uniform optics. LuxiGen delivers the industry’s lowest thermal resistance per package area, made possible by LED Engin’s unique patented compact ceramic pack-age. Additionally, the emitters deliver superior flexibility in light output with power ranging from 3 W to 90 W and a wide selection of colors from UV 365 nm to infrared 940 nm.

The multi-chip packages are also avail-able in multi-color/wavelength options such as RGBW, RGBA or Dental Blue and UV. Every die is individually addressable for maximum design flexibility. A suite of complementary total internal reflection (TIR) lenses is offered for these emitters in Narrow Spot to Wide Flood beam.www.digikey.com

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Industry News

21Global LED/OLED Supplement • Winter 2015

■ Ewald Braith

■ Avnet Abacuc team

LOPEC 2015 will feature a paper keyboard, flashing packaging and a printed speaker

Now in its fifth year, the OE-A (Organic and Printed Electronics Association) Demonstrator Competition shows what organic and printed electronics can make possible. Prizes will be awarded in five categories at the LOPEC trade show in Munich. The OE-A will also be presenting its new roadmap. And the latest Business Climate Survey takes a look at the organic and printed electronics industry.

A roll-up loudspeaker printed on foil and a foldable keyboard printed on paper. An interactive yoga-mat that supports exercise and an illuminated, electroluminescent scaffolding wrap. The OE-A Demonstrator Competition proves that printed electronics enables many different applications.

19 projects related to the demonstrator competition are being displayed at the OE-A booth. International companies, research institutions and universities are competing by presenting their ideas, products, prototypes and designs related to printed electronics. www.oe-a.org

Universal LightProbe tests colour and intensity of LEDs

The Universal LightProbe Spectra USB Sensor from Optomistic Products, designed for the colour and intensity test-ing of LEDs, is now available exclusively in the UK from Peak Test Services.

Universal LightProbes are small, highly versatile programmable sensors for the reliable testing of LEDs, addressing many different LED test environments and requirements - whether a simple check for a specific colour, or identifying the correct colour and intensity from a wide spectrum of colours, including white LEDs - while offering the choice of digital or analogue outputs.

Optomistic Products has recently introduced a version of the Universal LightProbe Sensors with a serial digital output and a sleek user-friendly USB interface incorporated into the sensor. Without losing the ease of use of the existing range, the new Universal LightProbe Spectra USB Sensor delivers a fast and simple serial-digital output directly to a PC.

Universal LightProbe sensors have the unique advantage of operating at any voltage from +5 V to +40 V, and they can withstand reverse polarity up to -18 V without suffering permanent damage. The range also includes one of the smallest

sensor sizes on the market today, making it ideally suited to the requirements of high-density fixture designs.www.optomisticproducts.comwww.thepeakgroup.com

BlueWave QX4 LED multi-head spot-curing system provides maximum flexibility

P350 BlueWave QX4 LED Spot-Curing SystemDymax Corporation has released the BlueWave® QX4™ high-intensity spot-curing system, featuring all the benefits of LED-curing technology in a small and versatile unit. The system is comprised of a controller and up to four LED heads which are available in 365, 385, and 405 nm and can be outfitted with 3-, 5-, or 8-mm diameter focusing lenses. The LED heads and focusing lenses can be used in any combination and can be controlled through the system’s variable mode, a feature that allows each head to be individually programed for intensity and cycle times. Individual exposure times and intensity settings can be set in 1% increments for each LED head, giving users maximum curing flexibility.

In addition to its curing versatility, the BlueWave® QX4™ also features an easy-to-use control interface that facilities flex-ibility in setup and use of the unit. The


New Products

PRODUCTS

■ BlueWave QX4

■ Product from LOPEC 2015


New Products

unit can be activated by foot pedal or PLC interface, allowing it to be easily incorpo-rated into automated systems.www.dymax.com

MechaTronix launches universal LED cooler for BJB LED module

MechaTronix launches universal LED cooler for BJB LED module under-100KThe BJB LED star cooler GH36d is specifically designed for luminaires using the BJB GH36d series LED modules and various brands of COB LED modules mounted by BJB Zhaga Book 3 or Zhaga Book 11 LED holders.The compact module GH36d consists of a based and encapsulated LED lamp with suitable Twist&Lock lamp holder.

The pre-tensioned leaf springs which are fixed with two standard screws, ensure a defined contact pressure of the light source to the heat sink and thereby a constant heat dissipation.

The versions with 1,200 lm, 2,000 lm, and 3,000 lm luminous flux, as well as with 3,000 K and 4,000 K color tem-perature, enable an easy entry with low-maintenance, flexible LED solutions into shops, offices and the hospitality field.

With a thermal resistance of 1.1°C/W in a diameter of 99 millimeter, the BJB LED star cooler offers a perfect passive

cooling platform for luminaires up to 5000 lumen.Through a modular mount-ing pattern the GH36d LED cooler offers a wide platform of mechanical exchange-ability – including Zhaga book 3 and Zhaga book 11 mounting platforms.www.mechatronix-asia.com

Flip Chip Opto introduces 300W, 600W and 960W COBs

Flip Chip Opto, a LED lighting tech-nology company, announced its innova-tive P-Series of high-power LED Flip Chip / Chip-on-Board (COB) products. These high-performance lighting modules are comprised of patented 3-Pad LED flip chips with a Pillar Metal Core Printed Circuit Board (P-MCPCB) to substan-tially reduce module thermal resistance, and results in lower junction temperature, lower thermal decay and the feasibility of smaller light emitting surface (LES). Our innovation enables designers to enhance “Lumen-per-Dollar” performance by either driving the modules at higher cur-rents for more light output, or shrinking the heatsinks and optics dimensions, or reducing LED chip counts.

The High Power P-Series COBs feature 45x45 mils 3-Pad LED flip chips and high flux density in small LES. The currently models, P110-12S8P (96 chips), P110-

15S12P (180 chips) and P110-15S19P (285 chips) support “Boost” power at 300W, 600W and 960W with LES of 45mm, 60mm and 85mm, respectively. Their high “lumen-per-dollar” value and extremely low thermal resistance (0.01°C/W, 0.008°C/W and 0.007°C/W) make these COB solutions ideal to replace HID lumi-naires applied over stadium, sport com-plex, wharf, storage, airport, golf course, farmland and architectural display.www.fcopto.com

Constant current LED driver for machine vision and UV Curing features ethernet control

Innovations in Optics, Inc. introduces the Model 5000D-100 LED Driver/Controller for powering its patented Aurora Classic Line Source Illuminators. The 5000D-100 LED Driver provides constant current in either continuous, pulsed or PWM modes. An embedded system adds network control with 10/100Mbps Ethernet connectivity.

The 5000D-100 is also available for third party LED illuminators to be used as a constant current DC to DC driver/control-ler. Drive current in continuous mode is selectable from 200 to 2000 mA at 7.5 to 60VDC output. The output current setting is adjustable from 100% down to 10%, with duty cycle adjustment from 100% to 1% via the Ethernet interface for a 100:1 dimming range. Both analog and digital remote con-trols are built-in. An RJ-45 Ethernet port for network integration is accessed by end-users with a utility application and an easy to use GUI enables field-programmability. www.innovationsinoptics.com


■ Flip Chip Opto COB products



LED lighting is popular because many governments ban incan-descent bulbs to save energy and carbon dioxide, especially for general lighting. In the automotive

industry LEDs are being used because they save energy and costs, especially with the migration to hybrid cars and electric vehicles, and because the flexible LED light shape creates cool designs. These applications have created a need for more precise and accurate fluid dispensing as well as the dispensing of some fluids that require special attention. These dispensing applications must take into account • CIE value• Heat dissipation• LED life • Power savings• Production costs

People think switching to LED light-

ing is an up-front investment because it is much more expensive than other lights, such as incandescent and flores-cent, but LEDs should last for a much longer time, like more than 10 years, and their power consumption is much less. Therefore, the technologies that enable LEDS to save more power, have a longer life, and lower their produc-tion costs are important.

CIE value relates to the clarity and color of the product. People prefer to see a warm color which is similar to an incandescent light rather than a cool color like a florescent light in factories. People have a pretty good sense of distinguishing color differences with the naked eye, so the CIE specification is quite tight: many LED manufacturers require “1 bin” for the specification.

Heat dissipation technologies at the package and board assembly levels play

a key role in extending LED life. This is because heat dissipation reduces the LED’s junction temperature. The lower the junction temperature the longer the life. In addition, LED designers try to find the best way to extract as much light as possible to save power: the more efficient the light emission the less input power. Reduction in cost also contributes directly to making the investment equation better.

LED packages vary according to the end-application and cost constraints. Typical package types include • cavity encapsulation• flip chip with phosphor attachment• remote phosphor

Each of these packages has different dispensing applications.

Cavity encapsulation is the most popular package because of its long history, fewer patent constraints, simple structure, material availability, and

BY AKIRA MORITA

Dispensing Solutionsfor the LED Industry

■ Figure 1

■ Figure 2: LED Dispensing Applications.

technology as well as lower cost. The package needs silicone phosphor cavity encapsulation dispensing. The amount of phosphor in the cavity is the key to controlling CIE. The color depends on the consistency of the volume of the dis-pensed mixture. Changing the volume of the fluid considerably changes the color, so the dispensing operation to fill the cavity with phosphor silicone has to be very precise and consistent.

There are three major ways to get consistent dispensing: • a jetting valve with controlled process

jetting (CPJ+), • a displacement valve • an auger valve with mass flow control.

A jetting valve with CPJ+ is a sophis-ticated method which strikes a balance between getting an outstanding rate of units per hour (UPH) and good dispens-ing consistency. In CPJ+, the automated dispensing equipment measures the weight of the dot size and compensates for changes by recalibrating and adjust-ing the fluid volume as the viscosity of the fluid changes or the fluid changes

because of expansion. The jetting valve can achieve 18,000 UPH for a 3014 plas-tic leaded chip carrier (PLCC) package and +/-1.5% weight consistency by dot weight calibration with periodic moni-toring. See figure 1: Lead frame weight.

A displacement valve has the best weight consistency because its piston and cylinder structure provide volume measurement capability, but its UPH is a slow 8,000. An auger valve provides 8,000 UPH and a little less weight consistency even with mass flow control. Cavity encapsulation packages are produced in billions of units a year, therefore the bal-ance between consistency and productiv-ity is important.

Flip chip with phosphor plate attach-ment has a better performance package than cavity encapsulation because it has better heat dissipation, more emission extraction, a better power supply. Because of its higher performance, it is often used for applications where performance is more critical, such as in automotive head lamps. This package type requires several dispensing operations such as

underfill, reflection material dispensing, adhesive dispensing for plate attachment, and silicone casting. Underfill plays an important role in dissipating heat from the LED chip to the package substrate, thus providing a better heat path between the chip and substrate. The underfill material is usually silicone because of its heat resistance. When dispensing under-fill, a jetting valve is most commonly used because the fluid has to be placed extremely close to the die, get into very tight, hard-to-reach places, the volume of dispensed fluids is small, and it has to be dispensed accurately.

Thermal interface material (TIM) dispensing is important for heat dis-sipation although all LED package types are applicable. The material is applied between the LED package and the LED lamp substrate to transfer the heat from the package to the lamp and ultimately to the fixture. Many of the TIM materials are silicone.

Reflection material dispensing is done around the LED chip to prevent light from coming out of the side wall of the






LED. Titanium oxide (TiO2), which is a high viscosity material, is commonly used. The dispenser needs to have excel-lent location and placement accuracy because the dispenser has to negotiate LED chips as small as <300 µm x 300 µm to avoid contaminating the top die while filling the gap between the chip and wall. Dispensing location accuracy such as +/-40 µm plays a key role for dispensing. Auger and jetting valves are available for this application depending on the viscos-ity and UPH requirement.

Adhesive dispensing is required for phosphor plate attachment. In this pack-age, adhesive is dispensed on the top of the LED chip and a phosphor plate is then die bonded to that. The material dispensed is usually silicone. A consis-tent weight is important to avoid fluid bleeding or lessening the adhesion.

Silicone casting is used to cover an LED chip with an exposed phosphor

layer. In other words, the phosphor surface needs to be protected after phos-phor plate attachment. Pure silicone is dispensed on the surface.

Remote phosphor is the latest pack-age technology and has better light emission extraction than the others because of its unique structure. A space is created between the LED chip and phosphor to avoid yellow light and heat generated from the phosphor from being absorbed by the chip. The space between the chip and phosphor is filled with silicone by pure silicone dispens-ing. In a flip chip package, reflection material is dispensed for the same reason. The space gap is sometimes defined by the amount of silicone dis-pensed, therefore in silicone dispensing consistency is a key requirement.

As you can easily see in the package descriptions above, silicone dispens-ing is quite popular in LED packaging.

However, dispensing silicone is quite chal-lenging. The silicone is stringy and leaves a long tail that has to be cut (see Figure 2). If it is not cut cleanly and quickly, a long trail of fluid lays down next to the part instead of going into the cavity. The amount of silicone dispensed is precisely measured because the fluid volume plays a key role in the way the LED performs. If all the fluid doesn’t go into the cavity or place where it’s intended, then the amount of fluid won’t be accurate and perfor-mance will suffer. Not only is it messy, but in a tightly packed assembly that tail overlaps into the next package altering the volume in that LED. For every LED manufactured to be the same, a consistent amount of fluid has to be dispensed.

Z-retraction is the key movement used to cut the silicone tail, but there is a dis-tinct difference between the z-retraction of needle and jetting valves. A needle requires a long retraction in the z-axis. Jetting, on the other hand, needs a short one. Jetting has a unique technology that uses a valve with an active nozzle to easily make the cut. It requires only a tenth of the retraction that a needle does. The retraction is actually very time consuming and often accounts for a considerable per-cent of dispensing time. Therefore, using a jet vs. a needle not only helps solve the tail problem, but it significantly contributes to improvement in units per hour.

LEDs are becoming more common-place in all aspects of our life so manu-facturers will need to find the most cost effective way to produce them in large quantities while optimizing their color, performance, and product life. There are many manufacturing challenges because their packages are small, they are tightly packed with components, silicone is not easy to work with, and they need to be manufactured with precision, accu-racy, and consistency. Fluid dispens-ing plays an important part in many aspects of LED manufacturing. Because fluid dispensing has been an important component of microelectronic packaging and manufacturing for many years, the equipment, processes, and capabilities are already available and proven. Fluid dispensing equipment manufacturers will continue to innovate and adapt their equipment and processes to play a vital role in the manufacture of LEDS.

■ Figure 3: Silicone Dispensing.

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28 www.globalledoled.comGlobal LED/OLED Supplement • Winter 2015 28

Parylene HT: Unmatched UV and Thermal Stability Protection for LEDs

BY ALAN HARDY

Growing over the years from a few specific, high end uses to replacing many types of stan-dard lighting, LED technologies can be found in stadiums, train

stations, airports and city centers around the world due to their reliability, energy-efficiency and cost-effective operation. Most can easily picture the grandeur of today’s large LED billboards and screens; just think about popular tourist spots such as Piccadilly Circus in London, Ginza 4-chome Crossing in Tokyo and Times Square in New York. In addition to illuminating large display signs, com-puterized transit signage, traffic signals, streetlights and lighting on aircraft and automobiles, LED technologies can also be found lighting grocery store cases, manufacturing floors and our own living rooms, kitchens, offices and more. The increase in LED technology use around the world can be credited, in part, to their drop in price, but their sustainability lies in the benefits they offer –better light,

longer life, less energy consumption, and a lower cost of operation.

Various municipalities around the world are turning to LEDs to help manage their budgets, which are continu-ally being challenged, and to reduce their carbon footprint. Consider, for example, the city of Sydney, Australia, whose LED program was recently recognized for leadership and innovation (www.cityof-sydney.nsw.gov.au/vision/towards-2030/sustainability/carbon-reduction/led-lighting-project). The city of Sydney has reduced energy use by 34% since March 2012 by implementing more than 4,100 LED street and parking lights, with more lights to be replaced over the coming years. In addition to the cost-savings and environmental benefit, the city surveyed their residents and, according to their website, more than 90% said they found the new lights appealing while 75% said the LEDs improved visibility.

LED use also continues to increase in the automotive industry with the demand for safer, more energy–efficient vehicles. Manufacturers are looking to LED-based

daytime running lamps (DRLs) to mini-mize fuel consumption brought on by the continual use of headlamps, which is a result of directives such as the European Union’s 2008/89/EC. In light of this regulation, which requires all new models of cars (2011 and newer) to be fitted with DRLs, LED headlights are being implemented and consume considerably less energy than traditional headlamps. In terms of automobile design, internal lighting is also moving towards LEDs as their thin, flexible design allows for a more modern and sleek look.

As exhibited in these two industries, and could be further demonstrated with additional examples, LEDs are increas-ingly being used in both outdoor and indoor applications. The environments in which they need to operate, however, can pose challenges to LED manufactur-ers. Temperature extremes, moisture and humidity, and ultraviolet (UV) exposure are just a few of the obstacles LED assem-blies encounter. If not properly protected, these issues would inevitably cause pre-mature failure.


Parylene Coating

Liquid Coating

Liquid vs. Parylene Coating

C A S E S T U D Y

http://www.cityofsydney.nsw.gov.au/vision/towards-2030/sustainability/carbon-reduction/led-lighting-project




29www.globalledoled.com Global LED/OLED Supplement • Winter 2015

Conformal Coating Challenges

To ensure their long life, LEDs often benefit from some form of protective coating. Many conformal coatings, such as silicones, acrylics, urethanes, and potting compounds, were historically sufficient for less rugged applications. But, when asked to perform under pressure, e.g., tempera-ture cycling and/or extremes, humidity, UV exposure, etc., LEDs often succumb to their environmental conditions and fall short in one or more of these challenges.

Due to their thick and uneven nature, many liquid coatings cause light to be dis-torted or dimmed. Simply put, any coat-ing used to protect LEDs needs to allow their true color to shine brightly. In addi-tion to possible distortion, however, the coating’s unevenness may also lend itself to voids, causing unwanted pathways that allow moisture to ingress to the circuit board, lending to premature failure. In humid environments, adverse weather conditions, even routine cleaning, LEDs must be able to withstand any moisture to which they are commonly exposed. Premature failure of the underlying elec-tronics can quickly undermine the long term cost-savings that LEDs provide.

Many conformal coatings lose key per-formance characteristics upon exposure to UV light. For LED applications that must perform in UV-rich environments, coatings cannot yellow or become brittle. This breakdown not only adds a potential for distortion of the LED light, but also provides a way for moisture to ingress through the coating, again causing pre-mature failure. Thermal cycling has also been known to break down thicker coat-ings as they expand and contract when exposed to wide temperature extremes.

Finally, the total weight of LED displays must be considered. The natural mass of most coatings is a drawback for many LED applications as their weight can induce stress on delicate electronics, causing damage on a component-level. When coating the multitude of LED panels that make up a large display, for example, the total weight added by a coating is highly significant and can pose an engineering challenge due to the additional structural framework necessary to mount such large displays. Thinking about LED signage that can be found hanging mid-air in a train station or arena, secured on posts in an end zone, attached to the corner of a large

skyscraper, or even mounted onto trailers and trucks for mobile viewing, these mas-sive electronic displays and the infra-structure required to safely display them can weigh up to, or more than, 250,000 pounds. Providing reliable protection must be accomplished without adding a signifi-cant amount of weight to the end product.

These failures can be expensive, espe-cially when considering the large number of LED boards used in digital displays and video signage. While useful for many

areas of electronics manufacturing, most traditional conformal coatings are not able to provide the high level, long-lasting protection required by LED applications.

Parylene Conformal Coatings

Parylene conformal coatings offer an alternative to heavy liquid coating and potting materials. The coatings, which are extremely thin and lightweight, offer excellent moisture, chemical and dielectric barrier properties. Additionally, Parylene HT® offers unparalleled stability in high temperature and UV environ-ments, providing maximum protection for LED applications.

Parylene is the name for a unique series of polymeric, organic coating materi-

als. They are polycrystalline and linear in nature, possess useful dielectric and barrier properties per unit thickness, and are chemically inert. Parylene coatings are ultra-thin, optically clear and truly conform to and around components – regardless of size or complexity –due to its molecular level polymerization.

Parylene coatings are applied through vapor deposition rather than a dispensing, spray, brush or dip process. The parts to be coated are placed in the deposition chamber and the powdered raw material, known as “dimer”, is placed in the vaporizer at the opposite end of the deposition system. The dimer is heated, causing it to sublimate to a vapor, then heated again to break it into a monomeric vapor. This vapor is then trans-ferred into an ambient temperature cham-ber where it spontaneously polymerizes onto the parts, forming the thin Parylene film. The Parylene process is carried out in a closed system under a controlled vacuum, with the deposition chamber remaining at room temperature throughout the process. No solvents, catalysts or plasticizers are used in the coating process.

Because there is no liquid phase during the deposition process, there are no subsequent meniscus, pooling or bridging effects as can be seen in the application of liquid coatings. The molecular “growth” of Parylene coatings produces not only an even, conformal coating at the thickness

29 29

■ Parylene HT

coated (top)

and non-coated

(bottom) boards

after testing in salt-

fog environment.

“Due to their thick and uneven nature, many liquid coatings cause light to be distorted or dimmed.”

30 www.globalledoled.comGlobal LED/OLED Supplement • Winter 2015 30


specified by the manufacturer, but because Parylene is formed from a gas, it also pene-trates into every crevice, regardless of how seemingly inaccessible, ensuring complete encapsulation of the substrate.

Parylene coatings are optically clear so they do not reduce the color or lumen output of LEDs. Applied in ultra-thin thicknesses, Parylene coatings are also extremely lightweight, offering excel-lent barrier properties without adding dimension or significant mass to delicate components. Parylene is typically applied in thickness ranging from 500 angstroms to 75 microns. A 25 micron coating of Parylene HT, for example, will have a dielectric capability in excess of 5,400 volts. No other coating material can be applied as thin as Parylene and still pro-vide the same level of protection.

While several variants of Parylene con-formal coatings are commercially available, Parylene HT is particularly well-suited for LED applications. A brief summary of Parylene HT’s properties include:

• UV STABILITY Unlike other conformal coatings, Parylene HT provides mea-surable protection from ultraviolet light exposure. Tested per ASTM G 154, Parylene HT did not show any signs of degradation or discoloration after over 2,000 hours of accelerated testing.

• HIGH TEMPERATURE STABILITY Tested per ASTM D 150, Parylene HT is thermally stable in operating temper-atures up to 350°C long-term, and can also withstand short-term exposures to 450° C.

• MOISTURE RESISTANCE All Parylene coatings offer incredibly low moisture vapor transmission and gas permeability rates, providing excellent barrier proper-ties to protect components from exposure to moisture, chemicals and/or gases.

• CREVICE PENETRATION The extremely small molecular size of Parylene allows it to ingress deep into

open areas on the top or bottom of any package, regardless of the size or com-plexity of integrated devices, ensuring complete coverage for reliable protection. Parylene HT has the smallest molecular structure of the Parylene family.

• LOWEST DIELECTRIC CONSTANT AND DISSIPATION FACTOR Parylene HT has an extremely low dielectric constant and dissipation factor, slightly lower than those of the other Parylenes and a significant improvement over more traditional conformal coatings. These properties enable Parylene to provide small, tight packages with dielectric insulation via a thin coating. It has been demonstrated that the voltage breakdown per unit thickness increases with decreasing Parylene film thickness.

LEDs consume up to 90 percent less energy than incandescent light bulbs and 50 percent less than fluorescent lighting, without the mercury disposal issues faced

SCS Parylene Properties

by compact fluorescent lamps (CFLs). And, the projected life of LEDs far surpasses that of both incandescent and fluorescent light-ing options. To fully take advantage of these benefits, some LED applications require an added layer of protection to reliably operate in their intended environments.

Parylene coatings – more specifically, Parylene HT –can benefit LED applica-tions in the automotive, aerospace, con-sumer electronics, industrial and military industries, wherever LED assemblies require protection from moisture and humidity, high temperatures and/or UV exposure. For applications where electrical failures, moisture ingress and UV damage can be common occurrences, the ability of Parylene to completely coat underneath, around and between the smallest compo-nents, without affecting the light emission of the LEDs, saves manufacturers both time and warranty costs.

■ Ultra-thin Parylene conformal coatings

are applied as a vapor at room temperature.

31www.globalledoled.com Global LED/OLED Supplement • Winter 2015

LED/OLED

March 24 - 25

Lighting ShowJohansburg, South Africawww.terrapinn.com/ exhibition/lighting-show-africa

March 25 - 27

LED Taiwan 2015Taiwanwww.ledtaiwan.org

May 21- 24

lED Expo ThailandBangkok, Thailandwww.ledexpothailand.com

May 5 - 7

LightFair InternationalNew York, NY USAwww.lightfair.com/lightfair/V40

September 16 - 19

LED ChinaGuangzhou, Chinawww.ledchina-sh.com/zh-cn

October 3 - 6

NECASan Francisco, CA USAwww.necanet.org

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