Whitepapers - Photonics
NuSil Technology's commitment to silicone education is manifested in part by our investment in
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resources like a Terms & Definitions document and an Adhesive / Primer study. While some papers are
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For further reading, please see our Technical Resources section.
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May 21, 2012
Novel Adhesions Methods for Solar Cell Assemblies
Traditionally, engineers and solar cell assemblers have used liquid silicone adhesives to bond solar cells to panel substrates such as satellites, and silicones with high light transmittance to bond cover glasses to cells. Using next generation silicone technology, low outgassing silicone pressure sensitive adhesives (PSA) and thin film sheeting can...
Traditionally, engineers and solar cell assemblers have used liquid silicone adhesives to bond solar cells to panel substrates such as satellites, and silicones with high light transmittance to bond cover glasses to cells. Using next generation silicone technology, low outgassing silicone pressure sensitive adhesives (PSA) and thin film sheeting can serve the same purpose as liquid adhesives but eliminate long wait times for room temperature cures or additional equipment, such as ovens, required to heat accelerate the cure process. Moreover, the processing these low outgassing materials undergo allows them to be used on extraterrestrial applications like satellites as mentioned above.
Apr 2, 2012
LED Packaging with Silicone Encapsulants
A Light Emitting Diode (LED) is not “one size fits all.” While many LEDs may appear similar, various applications call for different needs. Whether one is deciding how to construct the LED or what the final application is going to be, decisions on what material to use can vary drastically.
A Light Emitting Diode (LED) is not “one size fits all.” While many LEDs may appear similar, various applications call for different needs. Whether one is deciding how to construct the LED or what the final application is going to be, decisions on what material to use can vary drastically. It is for this reason that a relationship needs to be maintained between the LED packager and material supplier. In most cases, the material of choice for LED packagers is silicone. To accommodate the various needs of the LED packager, silicone has become widely used due to its flexibility. Some attributes of silicone that lend themselves well to the LED industry are a high transparency in the UV-visible spectrum, thermal stability, mechanical and optical properties and an ability to control the Refractive Index (RI).
Jan 26, 2012
Designing low permeability, optical-grade silicone systems – Guidelines for choosing a silicone based on transmission rates for barrier applications
Unprotected electronic components exposed to moisture from high humidity may fail due to corrosion of metal leads or other unfavorable reactions on chemically sensitive components. This is of high interest for silicones that encapsulate Light Emitting Diodes (LEDs) dies. For these applications, moisture and oxygen may react with materials, such...
Unprotected electronic components exposed to moisture from high humidity may fail due to corrosion of metal leads or other unfavorable reactions on chemically sensitive components. This is of high interest for silicones that encapsulate Light Emitting Diodes (LEDs) dies. For these applications, moisture and oxygen may react with materials, such as phosphor, used to make white LEDs for back-lighting applications and decrease or change the light output and color over time. Of the polymeric adhesives and sealants commercially available, silicones are used for their thermal stability, clarity, and comparably low modulus that provides stress relief during thermal cycling. In addition, silicones are also known to be very permeable to low molecular weight gases such as water vapor and oxygen. Recently, several types of silicones were tested for the oxygen and water vapor transmission rates, and it was found that they can have drastically different results. Silicone properties strongly affecting permeability are polymer backbone chemistry, crosslink density and fillers. Phenyl (C6H5) and trifluoropropyl (CF3CH2) groups are used to optimize the refractive index of optically clear silicones. The effect of chemical composition on the water vapor transfer rate (WVTR) and the oxygen transfer rate (OTR) at 400 C and 90% Relative Humidity was investigated on several silicones with various refractive indices and compared to polydimethylsiloxane (PDMS) with similar durometers. It was found that polymer backbone chemistry had a significant influence on the permeation rates and will assist in material selection when designing for low-permeable barriers to improve package reliability.
Jan 9, 2012
Choosing a Silicone for Joining Technologies
Engineers and material scientists are constantly looking for a polymeric adhesive that can perform in a broad operating temperature range, maintain chemical stability and offer unique mechanical properties. The dynamic attributes of silicone adhesives, sealants, coatings and encapsulants provide design engineers with a variety of solutions to the complex challenges...
Engineers and material scientists are constantly looking for a polymeric adhesive that can perform in a broad operating temperature range, maintain chemical stability and offer unique mechanical properties. The dynamic attributes of silicone adhesives, sealants, coatings and encapsulants provide design engineers with a variety of solutions to the complex challenges they face. The advantages of silicone lie in the chemistry of the polymer chain, which can be modified to achieve desired mechanical properties.
Apr 4, 2011
Choosing a Silicone Encapsulant for Photovoltaic Applications
Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when...
Non-phenyl containing 1.41 RI silicones have been used for several years for bonding solar arrays in the satellite industry. Phenyl groups on the siloxane polymer can change various properties of the silicone. Understanding how phenyl affects these properties allows the engineer to understand the benefits and risks when using a RI matching silicone to minimize light loss versus a non-phenyl containing silicone.
Dec 22, 2009
Using Optical Index Matching Silicone Gels to Improve Outdoor Viewing and Ruggedness of Displays
Portable computing, military environments, and demanding outdoor activities like fire rescue require a reliable and accurate display. The bright ambient light outdoors can cause high reflection losses and subsequently “display washout.” A growing trend is use of optical index matching silicone gels to reduce reflection losses and also aid in...
Portable computing, military environments, and demanding outdoor activities like fire rescue require a reliable and accurate display. The bright ambient light outdoors can cause high reflection losses and subsequently “display washout.” A growing trend is use of optical index matching silicone gels to reduce reflection losses and also aid in durability.
Apr 30, 2008
Evaluation of Phosphor Settling Rate in Silicone Encapsulant
Working with LED manufacturers reveals a common problem: how to effectively add
phosphor to the silicone encapsulant without having it settle or incur processing problems
like curing too soon, deairing and bubbles. A study was done to evaluate two silicone
encapsulation materials for their ability to maintain phosphor in solution for ease of
manufacturing...
Working with LED manufacturers reveals a common problem: how to effectively add
phosphor to the silicone encapsulant without having it settle or incur processing problems
like curing too soon, deairing and bubbles. A study was done to evaluate two silicone
encapsulation materials for their ability to maintain phosphor in solution for ease of
manufacturing and production of white light emitting diodes. The phosphor dispersions
were evaluated over a large temperature range, -40 to 150°C, to attempt to understand the
material in the most broad and general way. This temperature range was subsequently
divided into storage, -40°C to –20°C, dispensing, 15°C to 35°C, and curing, > 40°C,
recognizing these portions of the range have unique requirements for production
applications.
Apr 30, 2008
Evaluation of Phosphor Settling Rate in Silicone Encapsulant
Working with LED manufacturers reveals a common problem: how to effectively add
phosphor to the silicone encapsulant without having it settle or incur processing problems
like curing too soon, deairing and bubbles. A study was done to evaluate two silicone
encapsulation materials for their ability to maintain phosphor in solution for ease of
manufacturing...
Working with LED manufacturers reveals a common problem: how to effectively add
phosphor to the silicone encapsulant without having it settle or incur processing problems
like curing too soon, deairing and bubbles. A study was done to evaluate two silicone
encapsulation materials for their ability to maintain phosphor in solution for ease of
manufacturing and production of white light emitting diodes. The phosphor dispersions
were evaluated over a large temperature range, -40 to 150°C, to attempt to understand the
material in the most broad and general way. This temperature range was subsequently
divided into storage, -40°C to –20°C, dispensing, 15°C to 35°C, and curing, > 40°C,
recognizing these portions of the range have unique requirements for production
applications.
Feb 13, 2008
A Characterization of Yellowing Caused by UV Radiation on Silicone Encapsulants, and Improvements in Future Materials
This study evaluates twenty-one samples for their change in optical transmission due to a 680-6800J/cm2 dose of UV radiation.
Samples were made from UV curing acrylate, epoxy and silicone chemistries. All samples were prepared and exposed the same way
so that comparisons between the samples would be meaningful. Given the same dosage...
This study evaluates twenty-one samples for their change in optical transmission due to a 680-6800J/cm2 dose of UV radiation.
Samples were made from UV curing acrylate, epoxy and silicone chemistries. All samples were prepared and exposed the same way
so that comparisons between the samples would be meaningful. Given the same dosage of UV, silicones perform better than UV
curing acrylates, which perform better than epoxies.
Jan 23, 2007
A Characterization of UV Effects on Optical Silicones used in Opto-electronic Devices and New Developments in Resistant Materials
Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been...
Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been used throughout the last decade1, 2. The high light flux and associated heat proved too much for the traditional epoxies. Data confirms silicone encapsulants/adhesives provide longer optical transmission life than epoxy encapsulants 3. Almost all optical devices have some interaction with UV wavelengths. Manufacturers of Blue LEDs with wavelengths near 405nm, and other LEDs that emit wavelengths deeper into the UV (365-399nm), have concerns about the effects of this radiation on the light transmission of the encapsulant over time. LCD and sensor devices may have UV radiation from the sun to contend with. This paper looks at many different encapsulants/adhesives, silicone, epoxy and acrylate, for their change in optical transmission due to a 680- 68000J/cm2 dose of radiation with the following spectral output: 34% in the UVA (320-399nm), 17% in the UVB (280-319nm), and 49% concentrated at 405nm and 450nm. All samples were prepped and exposed the same way so that comparisons between the samples would be meaningful. Results show that silicones perform better than acrylates, which perform better than epoxies, and not all silicones perform equally. Data will be provided of the best performing materials and a discussion of future work given the understanding of the chemistry.
Jan 23, 2007
A Characterization of UV Effects on Optical Silicones used in Opto-electronic Devices and New Developments in Resistant Materials
Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been...
Opto-electronic devices such as LEDs, optical sensors, LCDs and color filters have the need for optically transparent encapsulants or adhesives. Maintaining the highest transmission possible of the encapsulant/adhesive throughout the life of the device is a critical criteria for the device designer. Silicones as encapsulants/adhesives in opto-electronic devices have been used throughout the last decade1, 2. The high light flux and associated heat proved too much for the traditional epoxies. Data confirms silicone encapsulants/adhesives provide longer optical transmission life than epoxy encapsulants 3. Almost all optical devices have some interaction with UV wavelengths. Manufacturers of Blue LEDs with wavelengths near 405nm, and other LEDs that emit wavelengths deeper into the UV (365-399nm), have concerns about the effects of this radiation on the light transmission of the encapsulant over time. LCD and sensor devices may have UV radiation from the sun to contend with. This paper looks at many different encapsulants/adhesives, silicone, epoxy and acrylate, for their change in optical transmission due to a 680- 68000J/cm2 dose of radiation with the following spectral output: 34% in the UVA (320-399nm), 17% in the UVB (280-319nm), and 49% concentrated at 405nm and 450nm. All samples were prepped and exposed the same way so that comparisons between the samples would be meaningful. Results show that silicones perform better than acrylates, which perform better than epoxies, and not all silicones perform equally. Data will be provided of the best performing materials and a discussion of future work given the understanding of the chemistry.
Sep 28, 2006
How Temperature Effects Transmission of Silicone Encapsulants
This paper describes five optically clear materials that were evaluated for changes in optical transmission due to temperature (150°C). Initial testing revealed that 150°C temperature exposure enabled reactions between the silicone being tested and the gasket material used to form the sample preparation. Observation of the cross contamination accelerated by...
This paper describes five optically clear materials that were evaluated for changes in optical transmission due to temperature (150°C). Initial testing revealed that 150°C temperature exposure enabled reactions between the silicone being tested and the gasket material used to form the sample preparation. Observation of the cross contamination accelerated by the 150°C temperature exposure and the juxtaposition of dissimilar materials leads us to the following recommendations for working with optically clear silicones at high temperature:
- do everything possible to get the heat out
- be aware that effect of material incompatibilities will be accelerated at elevated temperatures
- use the lowest cure temperatures needed to accomplish the curing of the silicone
Sep 28, 2006
How Temperature Effects Transmission of Silicone Encapsulants
This paper describes five optically clear materials that were evaluated for changes in optical transmission due to temperature (150°C). Initial testing revealed that 150°C temperature exposure enabled reactions between the silicone being tested and the gasket material used to form the sample preparation. Observation of the cross contamination accelerated by...
This paper describes five optically clear materials that were evaluated for changes in optical transmission due to temperature (150°C). Initial testing revealed that 150°C temperature exposure enabled reactions between the silicone being tested and the gasket material used to form the sample preparation. Observation of the cross contamination accelerated by the 150°C temperature exposure and the juxtaposition of dissimilar materials leads us to the following recommendations for working with optically clear silicones at high temperature:
- do everything possible to get the heat out
- be aware that effect of material incompatibilities will be accelerated at elevated temperatures
- use the lowest cure temperatures needed to accomplish the curing of the silicone
Mar 18, 2005
Index Matching Silicone for High Brightness LED Packaging
Although silicone technology has been around for over 5 decades, this unique material continues to find usage in new applications. Its various functionalities allow its usage as fuel resistant gaskets, inert implantable devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease.
Although silicone technology has been around for over 5 decades, this unique material continues to find usage in new applications. Its various functionalities allow its usage as fuel resistant gaskets, inert implantable devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease. This paper will examine various silicones as effective encapsulants and lenses for High Brightness LEDs (HB LEDs). Physical and optical characteristics will be tested to determine which materials may prove to be the best.
Mar 18, 2005
Index Matching Silicone for High Brightness LED Packaging
Although silicone technology has been around for over 5 decades, this unique material continues to find usage in new applications. Its various functionalities allow its usage as fuel resistant gaskets, inert implantable devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease.
Although silicone technology has been around for over 5 decades, this unique material continues to find usage in new applications. Its various functionalities allow its usage as fuel resistant gaskets, inert implantable devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease. This paper will examine various silicones as effective encapsulants and lenses for High Brightness LEDs (HB LEDs). Physical and optical characteristics will be tested to determine which materials may prove to be the best.
Mar 2, 2005
Phosphors and Silicone Dispersions
From the perspective of a silicone material chemist, this paper will address the benefits of using silicone in phosphor dispersions for High Brightness LED (HBLED) packages. This investigation first provides an overview of how versatile of a material silicone can be to the HB LED industry. An examination of the...
From the perspective of a silicone material chemist, this paper will address the benefits of using silicone in phosphor dispersions for High Brightness LED (HBLED) packages. This investigation first provides an overview of how versatile of a material silicone can be to the HB LED industry. An examination of the chemistry of silicone, the multiple material composition options and various cure chemistries demonstrates how silicone can be tailored to fit specific applications. A brief discussion of both physical and optical properties of two types of material compositions, Cured Gels and Thermosets, the most common types used in HB LED packaging. Then, a general investigation of the way a silicone interacts with a phosphor, in regards to compatibility, particle size and potential interactions. The paper will also review methods of dispersion, processing considerations and equipment.
Mar 2, 2005
Phosphors and Silicone Dispersions
From the perspective of a silicone material chemist, this paper will address the benefits of using silicone in phosphor dispersions for High Brightness LED (HBLED) packages. This investigation first provides an overview of how versatile of a material silicone can be to the HB LED industry. An examination of the...
From the perspective of a silicone material chemist, this paper will address the benefits of using silicone in phosphor dispersions for High Brightness LED (HBLED) packages. This investigation first provides an overview of how versatile of a material silicone can be to the HB LED industry. An examination of the chemistry of silicone, the multiple material composition options and various cure chemistries demonstrates how silicone can be tailored to fit specific applications. A brief discussion of both physical and optical properties of two types of material compositions, Cured Gels and Thermosets, the most common types used in HB LED packaging. Then, a general investigation of the way a silicone interacts with a phosphor, in regards to compatibility, particle size and potential interactions. The paper will also review methods of dispersion, processing considerations and equipment.
Nov 4, 2004
Optical Silicones for use in Harsh Operating Environments
The optics industry widely uses silicones for various fiber optic cable potting applications and light emitting diode protection. Optics manufacturers know traditional silicone elastomers, gels, thixotropic gels, and fluids not only perform extremely well in high temperature applications, but also offer refractive index matching so that silicones can transmit light...
The optics industry widely uses silicones for various fiber optic cable potting applications and light emitting diode protection. Optics manufacturers know traditional silicone elastomers, gels, thixotropic gels, and fluids not only perform extremely well in high temperature applications, but also offer refractive index matching so that silicones can transmit light with admirable efficiency. However, because environmental conditions may affect a material’s performance over time, one must also consider the conditions the device operates in to ensure long-term reliability. External environments may include exposure to a combination of UV light and temperature, while other environments may expose devices to hydrocarbon based fuels. This paper will delve into the chemistry of silicones and functional groups that lend themselves to properties such as temperature, fuel, and radiation resistance to show why silicone is the material of choice for optic applications under normally harmful forms of exposure. Data will be presented to examine silicone’s performance in these environments.